rs-rich-cli 0.0.4

//! `rich` — a Rust port of the `rich-cli` terminal toolbox.
//!
//! This binary mirrors the upstream `rich-cli` command-line tool and is built on
//! the [`rich`] library crate. It implements the rendering modes `--print`,
//! `--markdown`, `--json`, `--syntax`, `--csv`, `--ipynb`, and `--rule`, plus
//! width/justify, HTML/SVG export to a file (`--export-html PATH` / `-o PATH`,
//! `--export-svg PATH`, which may be combined), the
//! `--panel`/`--padding` decorators (with `--title`/`--caption`/`--style`), a
//! plain-file printer (with extension auto-detection), **URL fetch** (`rich <url>`,
//! behind the default `fetch` feature), **paging** (`--pager`), and a capability
//! demo — i.e. the whole common rich-cli surface.

use std::io::{IsTerminal, Read, Write};
use std::process::ExitCode;

use rich::cells::cell_len;
use rich::markdown::Markdown;
use rich::measure::Measurement;
use rich::protocol::{LineRenderable, OwnedTableRows};
use rich::r#box::{Box as BoxSet, ASCII, ASCII2, DOUBLE, HEAVY, HEAVY_HEAD, ROUNDED, SQUARE};
use rich::text::Text;
use rich::{
    filesize, Align, AnsiDecoder, Bar, ColorSystem, Columns, Console, ConsoleOptions, Constrain,
    Control, Highlighter, HorizontalAlign, ISO8601Highlighter, Json, Justify, Layout, Live,
    LiveRender, LogLevel, LogRender, Padding, Panel, Pretty, Progress, ProgressBar, ProgressColumn,
    Renderable, Rule, Segment, Spinner, Status, Style, Styled, Syntax, Table, Traceback, Tree,
    DEFAULT_TERMINAL_THEME,
};
use rich_ext::cli::CliExtensions;
use rich_ext::encoding::{has_utf16_bom, Encoding};
use rich_ext::ConsoleExt;

/// Boxed `Text` helper to cut down on `Box::new(Text::new(...))` noise.
fn text(content: &str) -> Box<dyn Renderable> {
    Box::new(Text::new(content))
}

const VERSION: &str = env!("CARGO_PKG_VERSION");

/// How to render the resource. Mirrors the mutually-exclusive rich-cli flags.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum Mode {
    /// No explicit flag: auto-detect by file extension, else print plain.
    Auto,
    /// `-p/--print`: interpret the resource as console markup.
    Print,
    /// `-m/--markdown`: render the resource as Markdown.
    Markdown,
    /// `-j/--json`: pretty-print the resource as JSON.
    Json,
    /// `-x/--syntax`: syntax-highlight the resource (language from extension).
    Syntax,
    /// `--csv`: render a CSV/TSV resource as a table.
    Csv,
    /// `.ipynb`: render a Jupyter notebook (markdown + code cells + outputs).
    Ipynb,
    /// `--gif`: animate one or more GIFs in place.
    Gif,
    /// `--diff`: perceptually compare two images (takes exactly two resources).
    Diff,
    /// `--rule`: draw a horizontal rule (the resource, if any, is its title).
    Rule,
}

/// How `--diff` draws the image part of its report.
///
/// Detection of terminal graphics support is a heuristic and will be wrong
/// somewhere (there is no reliable probe that works when output is piped), so
/// this is exposed rather than inferred: when the guess is wrong the user
/// picks.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
enum ImageMode {
    /// Sixel where it looks supported, else half-blocks, else ASCII.
    Auto,
    /// Real pixels via the Sixel graphics protocol.
    Sixel,
    /// Half-block characters — works in any truecolour terminal.
    Blocks,
    /// A character ramp, the jp2a-style rendering. No colour required.
    Ascii,
    /// Skip the picture; print only the numbers.
    None,
}

impl std::str::FromStr for ImageMode {
    type Err = String;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        match value.to_ascii_lowercase().as_str() {
            "auto" => Ok(Self::Auto),
            "sixel" => Ok(Self::Sixel),
            "blocks" | "block" => Ok(Self::Blocks),
            "ascii" | "art" => Ok(Self::Ascii),
            "none" | "off" => Ok(Self::None),
            other => Err(format!(
                "unknown image mode {other:?} (auto, sixel, blocks, ascii, none)"
            )),
        }
    }
}

/// Parsed command line.
struct Cli {
    mode: Mode,
    resource: Option<String>,
    /// Every positional argument. Only `--gif` accepts more than one (so
    /// several animations can share the screen); other modes reject extras.
    /// Read only by the GIF player, hence unused without the `art` feature.
    #[cfg_attr(not(feature = "art"), allow(dead_code))]
    resources: Vec<String>,
    /// `--loop N`: how many times `--gif` repeats (0 = forever).
    #[cfg_attr(not(feature = "art"), allow(dead_code))]
    loops: Option<usize>,
    /// `--threshold PCT`: with `--diff`, exit non-zero when the changed
    /// percentage of the canvas exceeds this. Makes the tool a CI gate.
    #[cfg_attr(not(feature = "art"), allow(dead_code))]
    diff_threshold: Option<f32>,
    /// `--image-mode`: how `--diff` draws its picture.
    #[cfg_attr(not(feature = "art"), allow(dead_code))]
    image_mode: ImageMode,
    extensions: CliExtensions,
    width: Option<usize>,
    justify: Option<Justify>,
    no_color: bool,
    /// `--export-html PATH` (`-o PATH`): also write a self-contained HTML
    /// document to PATH. The resource is still rendered to the terminal.
    export_html: Option<String>,
    /// `--export-svg PATH`: also write a self-contained SVG document to PATH.
    export_svg: Option<String>,
    /// `--panel BOX`: wrap the output in a [`Panel`] with the named box.
    /// `--panel none` is upstream's default and means *no panel at all*, so it
    /// parses to `None` rather than to `box.NONE`.
    panel: Option<BoxSet>,
    /// `--padding T[,R[,B,L]]`: wrap the output in [`Padding`].
    padding: Option<(usize, usize, usize, usize)>,
    /// `--title`: the panel title, and the CSV table's title.
    title: Option<String>,
    /// `--caption`: the panel subtitle, and the CSV table's caption.
    caption: Option<String>,
    /// `-S/--panel-style`: the panel *border* style.
    panel_style: Option<Style>,
    /// `-s/--style`: a style laid under the whole renderable (upstream's
    /// `Styled`), applied outside the panel.
    style: Option<Style>,
    /// `-e/--expand`: make `--panel`/`--padding` fill the available width
    /// instead of shrinking to their content. Implied by `--width`.
    expand: bool,
    /// `--pager`: page the output through the system pager.
    pager: bool,
    /// `-y/--hyperlinks`: render a Markdown link as an OSC 8 hyperlink.
    /// Upstream's flag, and upstream's default of **false** — see
    /// [`build_markdown`], which is where it is consumed.
    hyperlinks: bool,
}

/// Build the `-m/--markdown` renderable, honouring `-y/--hyperlinks`.
///
/// Upstream is `Markdown(markdown_data, code_theme=theme, hyperlinks=hyperlinks)`
/// with `@click.option("--hyperlinks", "-y", is_flag=True)`, so the default is
/// **false**: `rich -m` renders `[text](url)` as `text (url)`, with the URL
/// visible, and only `-y` turns it into an OSC 8 hyperlink whose target the
/// reader cannot see.
///
/// Without this, `rich -m` emitted the OSC 8 rendering unconditionally and the
/// destination appeared nowhere in the byte stream — so every URL in a document
/// was unrecoverable as soon as the output was piped or `NO_COLOR` was set.
fn build_markdown(source: &str, hyperlinks: bool) -> Markdown {
    Markdown::new(source).hyperlinks(hyperlinks)
}

fn main() -> ExitCode {
    let args: Vec<String> = std::env::args().skip(1).collect();
    match parse(&args) {
        Ok(None) => ExitCode::SUCCESS, // help/version already printed
        Ok(Some(cli)) => run(cli),
        Err(message) => {
            eprintln!("rich: {message} (try --help)");
            ExitCode::FAILURE
        }
    }
}

/// Map a `--panel` box name to a box set (port of rich-cli's `BOXES` +
/// `getattr(box, name.upper())`).
///
/// `none` is upstream's *default* for `--panel`, and upstream guards the whole
/// panel step with `if panel != "none"` — so it means "no panel", not "a panel
/// drawn with `box.NONE`". Drawing box.NONE put an invisible one-cell frame and
/// a blank line around the output, which reads as the tool having mangled the
/// file for no reason.
fn parse_box(name: &str) -> Result<Option<BoxSet>, String> {
    Ok(Some(match name.to_ascii_lowercase().as_str() {
        "none" => return Ok(None),
        "ascii" => ASCII,
        "ascii2" => ASCII2,
        "square" => SQUARE,
        "rounded" => ROUNDED,
        "heavy" => HEAVY,
        "double" => DOUBLE,
        other => {
            return Err(format!(
                "unknown panel box {other:?} (use none/ascii/ascii2/square/rounded/heavy/double)"
            ))
        }
    }))
}

/// Parse a `--padding` value: 1, 2, or 4 comma-separated integers, unpacked into
/// `(top, right, bottom, left)`. Port of rich-cli's padding parsing + upstream's
/// `Padding.unpack`.
fn parse_padding(value: &str) -> Result<(usize, usize, usize, usize), String> {
    let error = || "padding should be 1, 2, or 4 integers separated by commas".to_string();
    let parts: Result<Vec<usize>, _> = value
        .split(',')
        .map(|p| p.trim().parse::<usize>())
        .collect();
    let parts = parts.map_err(|_| error())?;
    match parts.as_slice() {
        [p] => Ok((*p, *p, *p, *p)),
        [v, h] => Ok((*v, *h, *v, *h)),
        [t, r, b, l] => Ok((*t, *r, *b, *l)),
        _ => Err(error()),
    }
}

/// Set the render mode, rejecting a second, conflicting mode flag.
fn set_mode(current: &mut Mode, mode: Mode) -> Result<(), String> {
    if *current != Mode::Auto && *current != mode {
        return Err(
            "only one render mode (--print/--markdown/--json/--syntax/--csv/--ipynb/--rule/--gif/--diff) \
             may be given"
                .into(),
        );
    }
    *current = mode;
    Ok(())
}

/// Parse args into a [`Cli`], or `Ok(None)` when `--help`/`--version` handled it.
fn parse(args: &[String]) -> Result<Option<Cli>, String> {
    let mut mode = Mode::Auto;
    let mut resources: Vec<String> = Vec::new();
    let mut loops = None;
    let mut diff_threshold = None;
    let mut image_mode = ImageMode::Auto;
    let mut extensions = CliExtensions::default();
    let mut width = None;
    let mut justify = None;
    let mut no_color = std::env::var_os("NO_COLOR").is_some_and(|value| !value.is_empty());
    let mut export_html: Option<String> = None;
    let mut export_svg: Option<String> = None;
    let mut panel = None;
    let mut padding = None;
    let mut title = None;
    let mut caption = None;
    let mut panel_style = None;
    let mut style = None;
    let mut expand = false;
    let mut pager = false;
    let mut hyperlinks = false;
    // Set by `--`: everything after it is a positional argument, however much it
    // looks like a flag. Without this nothing beginning with `-` could be
    // printed or opened at all — `rich -p -- "-5 degrees"` and `rich -- -weird.md`
    // both died with "unknown option".
    let mut end_of_options = false;

    let mut iter = args.iter();
    while let Some(arg) = iter.next() {
        if end_of_options {
            resources.push(arg.to_string());
            continue;
        }
        if extensions.parse_option(arg, &mut iter)? {
            continue;
        }
        match arg.as_str() {
            "--" => end_of_options = true,
            "-h" | "--help" => {
                print_help();
                return Ok(None);
            }
            "-V" | "--version" => {
                println!("rich (rs-rich-cli) {VERSION}");
                return Ok(None);
            }
            "-p" | "--print" => set_mode(&mut mode, Mode::Print)?,
            "-m" | "--markdown" => set_mode(&mut mode, Mode::Markdown)?,
            "-j" | "--json" => set_mode(&mut mode, Mode::Json)?,
            "-x" | "--syntax" => set_mode(&mut mode, Mode::Syntax)?,
            "--csv" => set_mode(&mut mode, Mode::Csv)?,
            "--ipynb" => set_mode(&mut mode, Mode::Ipynb)?,
            "--gif" => set_mode(&mut mode, Mode::Gif)?,
            "--diff" => set_mode(&mut mode, Mode::Diff)?,
            "--image-mode" => {
                let value = iter
                    .next()
                    .ok_or("--image-mode requires one of: auto, sixel, blocks, ascii, none")?;
                image_mode = value.parse()?;
            }
            "--threshold" => {
                let value = iter
                    .next()
                    .ok_or("--threshold requires a percentage, e.g. --threshold 2")?;
                let percent: f32 = value
                    .parse()
                    .map_err(|_| format!("invalid threshold '{value}'"))?;
                // `"NaN"` and `"inf"` both parse as f32, and every comparison
                // against NaN is false — so an empty template variable or a bad
                // substitution would turn the gate off and report a pass. A gate
                // that can be silently disabled is worse than no gate.
                if !percent.is_finite() || !(0.0..=100.0).contains(&percent) {
                    return Err(format!(
                        "threshold must be a percentage between 0 and 100, got '{value}'"
                    ));
                }
                diff_threshold = Some(percent);
            }
            "--loop" => {
                let value = iter.next().ok_or("--loop requires a count (0 = forever)")?;
                loops = Some(
                    value
                        .parse()
                        .map_err(|_| format!("invalid loop count {value:?}"))?,
                );
            }
            "--rule" => set_mode(&mut mode, Mode::Rule)?,
            "--left" => justify = Some(Justify::Left),
            "--right" if justify != Some(Justify::Left) => justify = Some(Justify::Right),
            "--right" => {}
            "--center" if justify.is_none() => justify = Some(Justify::Center),
            "--center" => {}
            "--no-color" => no_color = true,
            "--pager" => pager = true,
            // Upstream's `@click.option("--hyperlinks", "-y", is_flag=True,
            // help="Render hyperlinks in markdown.")`. Accepted in every mode,
            // as click accepts it — it is read only where markdown is rendered.
            "-y" | "--hyperlinks" => hyperlinks = true,
            // Both take a PATH and both may be given at once, matching
            // upstream: the resource still renders to the terminal and the
            // files are written alongside it.
            "--export-html" | "-o" => {
                export_html = Some(iter.next().ok_or("--export-html requires a PATH")?.clone());
            }
            "--export-svg" => {
                export_svg = Some(iter.next().ok_or("--export-svg requires a PATH")?.clone());
            }
            "--panel" => {
                let value = iter.next().ok_or("--panel requires a box name")?;
                panel = parse_box(value)?;
            }
            "--padding" => {
                let value = iter.next().ok_or("--padding requires a value")?;
                padding = Some(parse_padding(value)?);
            }
            "-e" | "--expand" => expand = true,
            "--title" => {
                title = Some(iter.next().ok_or("--title requires a value")?.clone());
            }
            "--caption" => {
                caption = Some(iter.next().ok_or("--caption requires a value")?.clone());
            }
            // `-s/--style` is the style of the *renderable* (upstream wraps it in
            // `Styled`); `-S/--panel-style` is the border. They were fused into
            // one flag that set the border, so there was no way to style the
            // content at all and `--style` aborted without `--panel`.
            "-s" | "--style" => {
                let value = iter.next().ok_or("--style requires a value")?;
                style = Some(Style::parse(value).map_err(|e| format!("invalid --style: {e}"))?);
            }
            "-S" | "--panel-style" => {
                let value = iter.next().ok_or("--panel-style requires a value")?;
                panel_style =
                    Some(Style::parse(value).map_err(|e| format!("invalid --panel-style: {e}"))?);
            }
            "-w" | "--width" => {
                let value = iter.next().ok_or("--width requires a number")?;
                let columns: usize = value.parse().map_err(|_| {
                    // The common cause is a missing value, in which case this
                    // has just eaten the filename — say so rather than quoting
                    // the path back with debug escaping.
                    if std::path::Path::new(value).exists() {
                        format!("--width needs a number, but got the file '{value}' — a value is missing")
                    } else {
                        format!("invalid width '{value}'")
                    }
                })?;
                if columns == 0 {
                    return Err("--width must be at least 1".into());
                }
                width = Some(columns);
            }
            other if other.starts_with('-') && other != "-" => {
                return Err(format!("unknown option {other:?}"));
            }
            other => resources.push(other.to_string()),
        }
    }

    // Only `--gif` animates several resources at once; every other mode renders
    // exactly one.
    if mode == Mode::Diff && resources.len() != 2 {
        return Err("--diff needs exactly two images: --diff before.png after.png".into());
    }
    // `--gif` animates in place and the demo writes its own console, so neither
    // goes through the export path: both accepted -o/--export-svg, wrote no
    // file, and exited 0. Everywhere else a bad export path is a hard error, so
    // silence here reads as success.
    let effective_mode = if mode == Mode::Auto {
        detect_mode(resources.first().map(String::as_str))
    } else {
        mode
    };
    extensions.validate(
        effective_mode == Mode::Gif,
        !(matches!(effective_mode, Mode::Gif | Mode::Diff | Mode::Rule)
            || (mode == Mode::Auto && resources.is_empty())
            || (mode == Mode::Print && resources.first().is_some_and(|r| r != "-" && !is_url(r)))),
    )?;
    let exporting = export_html.is_some() || export_svg.is_some();
    if exporting {
        let unsupported = if effective_mode == Mode::Gif {
            Some("--gif")
        } else if mode == Mode::Auto && resources.is_empty() {
            Some("the capability demo")
        } else {
            None
        };
        if let Some(what) = unsupported {
            return Err(format!("--export-html/--export-svg cannot capture {what}"));
        }
    }

    // A flag whose mode is absent is almost always a mistake, and silence is the
    // dangerous response: `--threshold` without `--diff` used to render the file
    // and exit 0, so a CI job that lost its `--diff` — a typo, a refactor, an
    // argument reordered — became a permanently green gate. That is the same
    // failure the NaN check closed, reached from the other side.
    let orphans = [
        (
            "--threshold",
            diff_threshold.is_some(),
            "--diff",
            mode == Mode::Diff,
        ),
        (
            "--image-mode",
            image_mode != ImageMode::Auto,
            "--diff",
            mode == Mode::Diff,
        ),
        (
            "--loop",
            loops.is_some(),
            "--gif",
            effective_mode == Mode::Gif,
        ),
        // `--title`/`--caption` are deliberately NOT here: upstream feeds them to
        // the CSV table as well as to the panel, so requiring `--panel` made
        // `rich --csv sales.csv --title Sales` — a documented upstream use —
        // impossible. `-S`/`-e` really do nothing without a panel.
        (
            "--panel-style",
            panel_style.is_some(),
            "--panel",
            panel.is_some(),
        ),
        (
            "--expand",
            expand,
            "--panel/--padding",
            panel.is_some() || padding.is_some(),
        ),
    ];
    if let Some((flag, _, needs, _)) = orphans
        .iter()
        .find(|(_, given, _, mode_present)| *given && !*mode_present)
    {
        return Err(format!("{flag} only has an effect with {needs}"));
    }

    // These decorate a single rendered resource; --diff composes its own report
    // and quietly dropped them, which reads as the flag having no effect.
    let demo = mode == Mode::Auto && resources.is_empty();
    if matches!(effective_mode, Mode::Diff | Mode::Gif) || demo {
        let mode_name = if effective_mode == Mode::Gif {
            "--gif"
        } else if demo {
            "the capability demo"
        } else {
            "--diff"
        };
        let unsupported = [
            ("--pager", pager && (effective_mode == Mode::Gif || demo)),
            ("--width", demo && width.is_some()),
            ("--hyperlinks", demo && hyperlinks),
            ("--panel", panel.is_some()),
            ("--padding", padding.is_some()),
            ("--title", title.is_some()),
            ("--caption", caption.is_some()),
            ("--style", style.is_some()),
            ("--panel-style", panel_style.is_some()),
            ("--expand", expand),
            ("--left/--center/--right", justify.is_some()),
        ];
        if let Some((flag, _)) = unsupported.iter().find(|(_, given)| *given) {
            return Err(format!("{flag} cannot be combined with {mode_name}"));
        }
    }
    if mode != Mode::Gif && mode != Mode::Diff && resources.len() > 1 {
        return Err("only one resource may be given (except with --gif)".into());
    }
    let resource = resources.first().cloned();

    Ok(Some(Cli {
        mode,
        resource,
        resources,
        loops,
        diff_threshold,
        image_mode,
        extensions,
        width,
        justify,
        no_color,
        export_html,
        export_svg,
        panel,
        padding,
        title,
        caption,
        panel_style,
        style,
        expand,
        pager,
        hyperlinks,
    }))
}

/// Read a resource: `-` (or `None`) means stdin, otherwise a file path.
///
/// A **file** is decoded with replacement, not rejected: upstream opens it as
/// `open(path, "rt", encoding="utf8", errors="replace")`, so a cp1252 export —
/// what Excel writes on a Windows box by default — renders with `�` where the
/// odd byte was. We refused the whole file with exit 1, which is the one
/// outcome that makes the tool useless for exactly the files people reach for
/// it with.
///
/// **Stdin stays strict.** Upstream reads it with `sys.stdin.read()`, whose
/// decode error escapes into rich-cli's `except Exception` and exits non-zero;
/// there is no `errors="replace"` on that path.
fn read_resource(resource: Option<&str>, encoding: Option<Encoding>) -> std::io::Result<String> {
    let content = match resource {
        Some(path) if path != "-" => {
            let file = std::path::Path::new(path);
            // A directory reaches the reader as "Access is denied" on Windows,
            // which sends the reader hunting for a permissions problem.
            if file.is_dir() {
                return Err(std::io::Error::new(
                    std::io::ErrorKind::InvalidInput,
                    "is a directory, not a file",
                ));
            }
            let bytes = std::fs::read(file)?;
            if let Some(encoding) = encoding {
                return encoding.decode(&bytes).map(normalize_newlines);
            }
            if has_utf16_bom(&bytes) {
                eprintln!("rich: {path} has a UTF-16 BOM; use --encoding utf-16 to decode it (default remains UTF-8 replacement)");
            }
            match String::from_utf8(bytes) {
                Ok(text) => text,
                // An image is not text in any encoding, and lossily decoding one
                // fills the terminal with thousands of replacement characters
                // and no clue. Keep the diagnostic for those; decode everything
                // else, which is what `errors="replace"` is actually for.
                Err(_) if looks_like_image(path) => {
                    return Err(std::io::Error::new(
                        std::io::ErrorKind::InvalidData,
                        "looks like an image; use `rich --diff <before> <after>` to compare images",
                    ))
                }
                Err(err) => String::from_utf8_lossy(err.as_bytes()).into_owned(),
            }
        }
        _ => {
            if std::io::stdin().is_terminal() {
                let eof = if cfg!(windows) {
                    "Ctrl-Z then Enter"
                } else {
                    "Ctrl-D"
                };
                eprintln!("rich: reading stdin; finish input with {eof}");
            }
            let mut buffer = Vec::new();
            std::io::stdin().read_to_end(&mut buffer)?;
            decode_strict(buffer, encoding)?
        }
    };
    Ok(normalize_newlines(if encoding.is_some() {
        content
    } else {
        strip_bom(content)
    }))
}

/// Strict stdin/URL input; the default file path separately retains replacement.
fn decode_strict(bytes: Vec<u8>, encoding: Option<Encoding>) -> std::io::Result<String> {
    if let Some(encoding) = encoding {
        return encoding.decode(&bytes);
    }
    String::from_utf8(bytes).map_err(|err| std::io::Error::new(
        std::io::ErrorKind::InvalidData,
        if has_utf16_bom(err.as_bytes()) {
            "input has a UTF-16 BOM; use --encoding utf-16"
        } else {
            "input is not valid UTF-8 text; for known headerless UTF-16 select --encoding utf-16le or utf-16be"
        },
    ))
}

/// Translate CRLF and lone CR to LF, as Python's universal newlines do.
///
/// Upstream reads text files in universal-newline mode, so it **never sees a
/// CR**; `std::fs::read_to_string` hands them straight through. That gap made
/// `--syntax` on a CRLF file render as a blank rectangle: each line was emitted
/// as `code` + CR + padding, so the CR returned the cursor to column 0 and the
/// padding overwrote the code. Exit 0, nothing visible, and piping hid it
/// because the bytes were all present — only a terminal acts on the CR.
fn normalize_newlines(text: String) -> String {
    const CR: char = '\r';
    const LF: char = '\n';
    if !text.contains(CR) {
        return text;
    }
    let mut out = String::with_capacity(text.len());
    let mut chars = text.chars().peekable();
    while let Some(c) = chars.next() {
        if c == CR {
            // CRLF and a lone CR both collapse to a single LF, matching
            // Python's universal-newline translation.
            if chars.peek() == Some(&LF) {
                chars.next();
            }
            out.push(LF);
        } else {
            out.push(c);
        }
    }
    out
}

/// Drop a leading UTF-8 byte-order mark.
///
/// Windows editors write one by default and it is invisible: it made valid JSON
/// fail to parse at "column 1", and Markdown render its first heading as
/// literal text at exit 0 — in both cases with nothing pointing at the cause.
/// Whether a path's extension names an image format `--diff` could read.
///
/// Used only to improve an error message, so a false negative costs nothing.
fn looks_like_image(path: &str) -> bool {
    std::path::Path::new(path)
        .extension()
        .and_then(|e| e.to_str())
        .map(|e| e.to_ascii_lowercase())
        .is_some_and(|e| {
            matches!(
                e.as_str(),
                "png" | "jpg" | "jpeg" | "gif" | "bmp" | "webp" | "tif" | "tiff" | "ico" | "avif"
            )
        })
}

fn strip_bom(text: String) -> String {
    match text.strip_prefix('\u{feff}') {
        Some(rest) => rest.to_string(),
        None => text,
    }
}

/// Whether `resource` is an `http(s)` URL (rich-cli's `rich <url>`). The scheme
/// is matched case-insensitively, as RFC 3986 specifies.
fn is_url(resource: &str) -> bool {
    let head: String = resource.chars().take(8).collect::<String>().to_lowercase();
    head.starts_with("http://") || head.starts_with("https://")
}

/// The lowercased file extension of a resource, taken from its basename (the
/// last path segment) with any `?query`/`#fragment` stripped — so it works for
/// URLs (`…/main.rs?raw=1` → `rs`) as well as plain paths.
fn resource_ext(resource: &str) -> Option<String> {
    let basename = resource.rsplit(['/', '\\']).next().unwrap_or(resource);
    let basename = basename.split(['?', '#']).next().unwrap_or(basename);
    basename
        .rsplit_once('.')
        .map(|(_, ext)| ext.to_ascii_lowercase())
        .filter(|ext| !ext.is_empty())
}

/// The maximum *decoded* response body we will hold in memory, in bytes.
/// Exceeding it is a hard error (we never render a truncated resource).
#[cfg(feature = "fetch")]
const MAX_BODY_BYTES: u64 = 16 * 1024 * 1024;

/// Fetch a URL over HTTP(S), returning `(body, content_type)`. Port of
/// rich-cli's `requests.get`, with two deliberate safety bounds upstream lacks:
/// a 30-second global timeout and [`MAX_BODY_BYTES`].
///
/// Like `requests.get`, a non-2xx status is **not** an error — the body is
/// returned so an error page still renders. TLS verification is on (rustls with
/// bundled webpki roots).
#[cfg(feature = "fetch")]
fn fetch_url(url: &str, encoding: Option<Encoding>) -> Result<(String, Option<String>), String> {
    use std::time::Duration;
    let mut response = ureq::get(url)
        .config()
        .timeout_global(Some(Duration::from_secs(30)))
        // Match `requests.get`: don't turn 4xx/5xx into an error, so the
        // response body (often a useful error page) is rendered instead.
        .http_status_as_error(false)
        .build()
        .call()
        .map_err(|err| format!("cannot fetch {url}: {err}"))?;
    let content_type = response
        .headers()
        .get("content-type")
        .and_then(|value| value.to_str().ok())
        .map(str::to_string);

    // Bound the *decoded* body: `.reader()` yields post-decompression bytes, so
    // capping it here (rather than via ureq's `limit()`, whose LimitReader sits
    // *under* the gzip decoder and would only bound compressed bytes) also
    // defuses a `Content-Encoding: gzip` bomb. Read one byte past the limit so
    // an oversized body is detectable rather than silently truncated.
    let mut buffer = Vec::new();
    response
        .body_mut()
        .with_config()
        .reader()
        .take(MAX_BODY_BYTES + 1)
        .read_to_end(&mut buffer)
        .map_err(|err| format!("cannot read {url}: {err}"))?;
    if buffer.len() as u64 > MAX_BODY_BYTES {
        return Err(format!(
            "{url} exceeds the {} MiB limit",
            MAX_BODY_BYTES / (1024 * 1024)
        ));
    }
    let body =
        decode_strict(buffer, encoding).map_err(|err| format!("cannot decode {url}: {err}"))?;
    Ok((body, content_type))
}

/// Stub used when the crate is built without the `fetch` feature.
#[cfg(not(feature = "fetch"))]
fn fetch_url(url: &str, _encoding: Option<Encoding>) -> Result<(String, Option<String>), String> {
    Err(format!(
        "cannot fetch {url}: this build has no URL support (rebuild with the `fetch` feature)"
    ))
}

/// The high-level render mode implied by a response `Content-Type` (the MIME
/// type, ignoring any `; charset=…`). Used only when neither a flag nor the URL
/// extension already picked a mode.
fn content_type_mode(content_type: &str) -> Option<Mode> {
    let mime = mime_of(content_type);
    match mime.as_str() {
        "text/markdown" | "text/x-markdown" => Some(Mode::Markdown),
        "application/json" | "text/json" => Some(Mode::Json),
        "text/csv" => Some(Mode::Csv),
        _ => None,
    }
}

/// A syntect lexer name for a response `Content-Type`, for syntax-highlighting a
/// fetched resource that has no informative extension. A small common subset of
/// upstream's Pygments MIME table.
fn content_type_lexer(content_type: &str) -> Option<&'static str> {
    let mime = mime_of(content_type);
    Some(match mime.as_str() {
        "text/html" | "application/xhtml+xml" => "html",
        "text/css" => "css",
        "application/javascript" | "text/javascript" => "javascript",
        "application/xml" | "text/xml" => "xml",
        "text/x-python" | "application/x-python" | "text/x-python3" => "python",
        "text/x-rust" => "rust",
        "text/x-c" | "text/x-csrc" => "c",
        "application/x-sh" | "text/x-shellscript" => "bash",
        "application/x-yaml" | "text/yaml" | "text/x-yaml" => "yaml",
        "application/toml" | "text/x-toml" => "toml",
        _ => return None,
    })
}

/// Whether an extension names no particular language, so a `Content-Type` that
/// does should win when picking a syntax lexer.
fn is_uninformative_ext(ext: &str) -> bool {
    matches!(ext, "txt" | "text" | "log" | "dat" | "out")
}

/// The bare MIME type from a `Content-Type` header (lowercased, `; charset=…`
/// and surrounding whitespace stripped).
fn mime_of(content_type: &str) -> String {
    content_type
        .split(';')
        .next()
        .unwrap_or("")
        .trim()
        .to_ascii_lowercase()
}

/// Resolve `Mode::Auto` to a concrete mode from the resource's file extension.
fn detect_mode(resource: Option<&str>) -> Mode {
    match resource.and_then(resource_ext).as_deref() {
        Some("md") | Some("markdown") => Mode::Markdown,
        Some("json") => Mode::Json,
        Some("csv") | Some("tsv") => Mode::Csv,
        Some("ipynb") => Mode::Ipynb,
        Some("gif") => Mode::Gif,
        // Anything the table above does not divert is source code, and upstream
        // highlights it: `rich main.rs` is syntax-highlighted with no flag at
        // all. We printed it raw instead, so `rich hello.py` produced no
        // highlighting and no styling in an export — while `docs/cli.md` line 12
        // advertised the upstream behaviour and `--help` documented ours. The
        // two contradicted each other; this resolves them the way the docs (and
        // upstream) say.
        Some(_) => Mode::Syntax,
        // No extension to go on (including stdin): stay in Auto and let the
        // caller decide, rather than guessing a lexer for something that may not
        // be source at all.
        None => Mode::Auto,
    }
}

/// Force a renderable to a fixed width, wherever on the screen it lands. Port
/// of rich-cli's `ForceWidth`.
///
/// `--width N` used to shrink the *console* to N, which also moved every
/// alignment inside N columns: `rich -w 20 --center` centred within 20 rather
/// than within the terminal, and an `--export-svg` frame came out N wide.
/// Upstream leaves the console alone and narrows only the renderable.
struct ForceWidth {
    child: Box<dyn Renderable>,
    width: usize,
}

impl Renderable for ForceWidth {
    fn rich_render(&self, console: &Console, options: &ConsoleOptions) -> Vec<Segment> {
        self.child
            .rich_render(console, &options.update_width(self.width))
    }

    fn measure(&self, _console: &Console, _options: &ConsoleOptions) -> Measurement {
        Measurement::new(self.width, self.width)
    }
}

/// Position a renderable within the available width. Port of the horizontal
/// axis of `rich.align.Align`, which is what `console.print(justify=…)` wraps
/// every renderable in.
///
/// The core crate's [`Align`] is not that: it renders its child at the *full*
/// width and pads each line by that line's own width, so it neither shrinks the
/// child (nothing that fills the width — `Syntax`, `Rule`, a `Panel` — moves at
/// all) nor squares the block off (multi-line output comes out ragged).
/// Upstream constrains the child to its measured width, `set_shape`s every line
/// to that one width, then pads the block. Doing that here leaves `align.rs`,
/// which other renderables depend on, untouched.
struct Aligned {
    child: Box<dyn Renderable>,
    /// The width to render the child *within* — what upstream's `Align` reads
    /// out of `console.measure(renderable)` and hands to `Constrain`. The block
    /// it then pads is measured from the output, not from this: a `--csv` table
    /// given `-w 40` still renders at its own 23 columns, and it is 23 that gets
    /// centred.
    width: usize,
    justify: Justify,
}

impl Renderable for Aligned {
    fn rich_render(&self, console: &Console, options: &ConsoleOptions) -> Vec<Segment> {
        let width = self.width.clamp(1, options.max_width);
        // The child renders with the console's own justify, not this alignment.
        // Upstream puts `print(justify=…)` into the render options, but rich-cli
        // builds its `--print`/`--rule` text with an explicit `justify="default"`
        // — a truthy string in Python — which blocks the inheritance, so
        // `-w 9 --center -p mid` centres a three-cell block within the terminal
        // rather than centring "mid" inside nine columns first. Every other
        // renderable this CLI builds (`Table`, `Json`, `Syntax`, `Markdown`)
        // ignores `options.justify` in this port, so there is nothing else for
        // the inheritance to reach.
        let lines = console.render_lines(self.child.as_ref(), &options.update_width(width), false);
        let widths: Vec<usize> = lines
            .iter()
            .map(|line| line.iter().map(Segment::cell_length).sum())
            .collect();
        // `Segment.get_shape` then `Segment.set_shape`: square the block off at
        // the widest line it actually produced, so a multi-line child moves as
        // one block instead of each line drifting to its own width.
        let shape = widths.iter().copied().max().unwrap_or(0);

        let excess = options.max_width.saturating_sub(shape);
        let (left, right) = match self.justify {
            Justify::Right => (excess, 0),
            Justify::Center => (excess / 2, excess - excess / 2),
            _ => (0, excess),
        };
        let blank = |count: usize| Segment::new(" ".repeat(count), Some(Style::new()));

        let mut segments = Vec::new();
        let last = lines.len().saturating_sub(1);
        for (index, (line, line_width)) in lines.into_iter().zip(widths).enumerate() {
            if left > 0 {
                segments.push(blank(left));
            }
            segments.extend(line);
            let pad = shape - line_width + right;
            if pad > 0 {
                segments.push(blank(pad));
            }
            if index != last {
                segments.push(Segment::line());
            }
        }
        segments
    }
}

/// The width a renderable actually occupies, found by rendering it.
///
/// `Table`, `Json` and friends inherit `(max_width, max_width)` from the
/// `Renderable` default in the core crate, so asking them to measure themselves
/// always answers "the whole console" and a fitted panel would not shrink at
/// all. Neither pads its output to the space it is given, though, so the widest
/// rendered line *is* upstream's `Measurement.get(…).maximum`, clamped to the
/// console — which is what a fitted `Panel` needs.
///
/// Not usable for `Syntax`, whose lines *are* padded out to the full width by
/// its background: that one is measured from the source instead.
fn measure_rendered(console: &Console, renderable: &dyn Renderable) -> usize {
    console
        .render_lines(renderable, &console.options(), false)
        .iter()
        .map(|line| line.iter().map(Segment::cell_length).sum::<usize>())
        .max()
        .unwrap_or(0)
}

/// Only labels consumed by a panel or CSV table should be parsed. Other modes
/// ignore these options upstream, including malformed unused markup.
fn validate_labels(cli: &Cli) -> Result<(), String> {
    for label in cli.title.iter().chain(cli.caption.iter()) {
        Text::from_markup(label).map_err(|err| err.to_string())?;
    }
    Ok(())
}

/// Apply upstream's decorator chain — padding, panel, style, fixed width,
/// alignment — and print the result. Port of the tail of rich-cli's `main`.
///
/// `fit` is the width the renderable measures at; `None` means "fills whatever
/// it is given", which is what a `Markdown` reports, so nothing shrinks to it.
fn decorate_and_emit(
    cli: &Cli,
    console: &Console,
    export: &Export,
    renderable: Box<dyn Renderable>,
    fit: Option<usize>,
) -> ExitCode {
    if cli.panel.is_some() {
        if let Err(err) = validate_labels(cli) {
            eprintln!("rich: {err}");
            return ExitCode::FAILURE;
        }
    }
    let max_width = console.width();
    // `if width > 0: expand = True` — a fixed width is a width to fill.
    let expand = cli.expand || cli.width.is_some();
    let mut renderable = renderable;
    let mut fit = fit;

    // This port's `Padding` and `Panel` always fill the width they are given, so
    // a *fitted* box is a `Constrain` around one. Upstream instead passes
    // `expand=False` and lets the box measure its own child — the same width,
    // reached from the outside, which is the only way that works while the core
    // crate's `Table`/`Syntax`/`Json` still inherit the default measurement.
    if let Some((top, right, bottom, left)) = cli.padding {
        let padded: Box<dyn Renderable> =
            Box::new(Padding::new(renderable, (top, right, bottom, left)));
        // `Padding.__rich_measure__`: the child plus the horizontal padding,
        // capped at the available width.
        fit = fit.map(|width| (width + left + right).min(max_width));
        renderable = if expand {
            padded
        } else {
            Box::new(Constrain::new(padded, fit))
        };
    }

    if let Some(box_set) = cli.panel {
        let mut panel = Panel::new(renderable).box_set(box_set);
        if let Some(title) = cli.title.clone() {
            panel = panel.title(title);
        }
        if let Some(caption) = cli.caption.clone() {
            panel = panel.subtitle(caption);
        }
        if let Some(style) = cli.panel_style.clone() {
            panel = panel.border_style(style);
        }
        // `Panel.__rich_measure__`: the wider of the child (measured in
        // `max_width - 4`) and the title, plus a border and a pad on each side.
        // The *subtitle* is deliberately absent — upstream does not measure it,
        // so a long `--caption` is truncated by the border rather than widening
        // the panel.
        //
        // Panel parses markup, normalizes newlines/tabs, and pads the label by
        // one cell on either side. Measure visible text with the same rules.
        let inner = max_width.saturating_sub(4);
        let child = fit.unwrap_or(inner).min(inner);
        let title_width = cli
            .title
            .as_deref()
            .map(|title| {
                let mut title = Text::from_markup(&rich::emoji::replace(title).replace('\n', " "))
                    .expect("title markup validated before rendering");
                title.expand_tabs(8);
                cell_len(title.plain()) + 2
            })
            .unwrap_or(0);
        fit = Some(child.max(title_width) + 4);
        let panel: Box<dyn Renderable> = Box::new(panel);
        renderable = if expand {
            panel
        } else {
            Box::new(Constrain::new(panel, fit))
        };
    }

    // `-s/--style` lays a style under everything, outside the panel — upstream's
    // `Styled(renderable, text_style)`. It does not change any width.
    if let Some(style) = cli.style.clone() {
        renderable = Box::new(Styled::new(renderable, style));
    }

    // `if width > 0 and not pager` — the pager lays out at its own width.
    if let Some(width) = cli.width.filter(|_| !cli.pager) {
        renderable = Box::new(ForceWidth {
            child: renderable,
            width,
        });
        fit = Some(width);
    }

    if let Some(justify) = cli.justify {
        renderable = Box::new(Aligned {
            child: renderable,
            width: fit.unwrap_or(max_width),
            justify,
        });
    }

    exit_code(emit(console, export, |c| c.print(renderable.as_ref())))
}

fn run(cli: Cli) -> ExitCode {
    // With no flags and no resource, show the capability demo.
    if cli.mode == Mode::Auto && cli.resource.is_none() {
        run_demo(cli.no_color);
        return ExitCode::SUCCESS;
    }

    let mut mode = match cli.mode {
        Mode::Auto => detect_mode(cli.resource.as_deref()),
        other => other,
    };

    // `--gif` and `--diff` write a stream of renderables to the
    // console themselves instead of composing one, so no wrapper can reach them:
    // those two keep taking `--width` on the console. Everything else gets
    // upstream's `ForceWidth` in `decorate_and_emit`, which is what keeps
    // `--center` centring inside the terminal.
    let width_on_console = matches!(mode, Mode::Gif | Mode::Diff);
    let mut builder = Console::builder().no_color(cli.no_color);
    if let Some(width) = cli.width.filter(|_| width_on_console) {
        builder = builder.width(width);
    }
    let mut console = builder.build();
    console.install_extensions();

    if mode == Mode::Rule {
        if let Some(title) = &cli.resource {
            if let Err(err) = Text::from_markup(title) {
                eprintln!("rich: {err}");
                return ExitCode::FAILURE;
            }
        }
    }

    // SVG export needs a title (the resource's basename, else "rich") and a
    // stable id. Upstream's auto id hashes Python reprs, so we use a fixed one
    // (see the rich crate's svg module / DIVERGENCES #15).
    let svg_title = cli
        .resource
        .as_deref()
        .filter(|r| *r != "-")
        .map(|r| r.rsplit(['/', '\\']).next().unwrap_or(r).to_string())
        .unwrap_or_else(|| "rich".to_string());
    let export = Export {
        html_path: cli.export_html.as_deref(),
        svg_path: cli.export_svg.as_deref(),
        svg_title: &svg_title,
        pager: cli.pager,
    };

    // GIF playback consumes the resource list itself (it can take several) and
    // animates rather than rendering once.
    if mode == Mode::Gif {
        return play_gifs(&cli, &console);
    }

    // `--diff` consumes both resources and reports rather than rendering one.
    #[cfg(feature = "art")]
    if mode == Mode::Diff {
        return run_diff(&cli, &console, &export);
    }

    // A rule takes its optional title from the resource string directly (no
    // fetch/read) — but it still goes through the decorators, because upstream
    // wraps it like anything else, so `--rule --panel` really does draw a panel.
    if mode == Mode::Rule {
        let rule = match cli.resource.as_deref() {
            Some(title) if title != "-" => Rule::new(title),
            _ => Rule::line(),
        };
        // `Rule.__rich_measure__` is `Measurement(1, 1)`: a rule claims no width
        // of its own, so a fitted panel around one is 5 cells wide.
        return decorate_and_emit(&cli, &console, &export, Box::new(rule), Some(1));
    }

    // Obtain the content: fetch it over HTTP(S) when the resource is a URL,
    // treat it as a literal markup string under `--print`, else read the
    // file/stdin. A URL also yields a `Content-Type` used below.
    let resource_is_url = matches!(cli.resource.as_deref(), Some(r) if is_url(r));
    let (content, content_type) = if resource_is_url {
        match fetch_url(cli.resource.as_deref().unwrap(), cli.extensions.encoding) {
            Ok(fetched) => fetched,
            Err(err) => {
                eprintln!("rich: {err}");
                return ExitCode::FAILURE;
            }
        }
    } else if mode == Mode::Print && matches!(cli.resource.as_deref(), Some(r) if r != "-") {
        (cli.resource.clone().unwrap(), None)
    } else {
        match read_resource(cli.resource.as_deref(), cli.extensions.encoding) {
            Ok(content) => (content, None),
            Err(err) => {
                let name = cli.resource.as_deref().unwrap_or("<stdin>");
                eprintln!("rich: cannot read {name}: {err}");
                return ExitCode::FAILURE;
            }
        }
    };

    // For a URL that neither a flag nor a telltale extension resolved: upstream
    // renders fetched content as syntax-highlighted source by default, unless the
    // Content-Type marks it markdown / json / csv.
    if resource_is_url && mode == Mode::Auto {
        mode = content_type
            .as_deref()
            .and_then(content_type_mode)
            .unwrap_or(Mode::Syntax);
    }

    // Pre-parse JSON so a parse error surfaces before any (HTML) rendering.
    let json = if mode == Mode::Json {
        match Json::new(content.trim()) {
            Ok(json) => Some(json),
            Err(err) => {
                eprintln!("rich: invalid JSON: {err}");
                return ExitCode::FAILURE;
            }
        }
    } else {
        None
    };

    // Same treatment for a notebook. Without this the parse failure was printed
    // from inside the render closure, which cannot influence the exit code — so
    // a broken notebook reported an error and exited 0, while a broken .json
    // exited 1. A malformed input must not look like success to a script.
    if mode == Mode::Ipynb {
        let notebook = match serde_json::from_str::<serde_json::Value>(&content) {
            Ok(value) if value.get("cells").and_then(|c| c.as_array()).is_some() => value,
            Ok(_) => {
                eprintln!("rich: not a notebook: no `cells` array");
                return ExitCode::FAILURE;
            }
            Err(err) => {
                eprintln!("rich: invalid notebook JSON: {err}");
                return ExitCode::FAILURE;
            }
        };
        let renderable = build_ipynb(&notebook, cli.hyperlinks, cli.justify);
        let fit = renderable.measure(&console, &console.options()).maximum;
        return decorate_and_emit(&cli, &console, &export, Box::new(renderable), Some(fit));
    }

    // Markup comes from the user in Print mode, so a mistake in it should be
    // reported rather than printed literally (upstream raises `MarkupError`).
    // Checked up front because the render closure below cannot fail.
    if mode == Mode::Print {
        if let Err(err) = console.try_build_text(&content) {
            eprintln!("rich: {err}");
            return ExitCode::FAILURE;
        }
    }

    // The highlighting language comes from the resource extension, falling back
    // (for a URL) to a lexer guessed from its Content-Type. An *uninformative*
    // extension (.txt/.log/…) doesn't shadow a Content-Type that names a real
    // language, so `snippet.txt` served as `text/x-python` still highlights.
    let extension = resource_ext(cli.resource.as_deref().unwrap_or_default())
        .filter(|ext| !is_uninformative_ext(ext));
    let language = extension
        .or_else(|| {
            content_type
                .as_deref()
                .and_then(content_type_lexer)
                .map(str::to_string)
        })
        .unwrap_or_default();

    // Build the renderable, and the width a non-expanding `Panel`/`Padding`
    // would shrink around it — upstream's `Measurement.get(…).maximum`.
    let (renderable, fit): (Box<dyn Renderable>, Option<usize>) = match mode {
        // `Markdown` defines no `__rich_measure__`, so upstream measures it as
        // the whole available width and a panel around it never shrinks.
        Mode::Markdown => (Box::new(build_markdown(&content, cli.hyperlinks)), None),
        Mode::Json => {
            // `rich.json.JSON` sets `text.no_wrap = True`, and every decorator
            // upstream can wrap the document in — `Padding`, `Panel`, `Styled`,
            // `ForceWidth` — is a `ConsoleRenderable`, so the `Text` reaches
            // `Text.__rich_console__` with the flag intact and each line is
            // CROPPED at the width. A *bare* document is a `Text`, which
            // `_collect_renderables` re-joins through `Text(sep).join(...)`;
            // `Text.join` copies its metadata from the separator, so the flag
            // is lost and the default fold wrap applies instead.
            //
            // `--left/--center/--right` is not on the list: `align_append`
            // wraps whatever `check_text` produced, so the join — and the loss
            // — has already happened by the time `Align` sees it.
            //
            // `--pager` skips `ForceWidth`, but pages through
            // `console.render_lines(renderable, …)`, which renders the `Text`
            // directly and keeps the flag.
            let nested = cli.padding.is_some()
                || cli.panel.is_some()
                || cli.style.is_some()
                || cli.width.is_some()
                || cli.pager;
            let json = json.expect("json parsed above").no_wrap(nested);
            #[cfg(feature = "json-escape-safe")]
            let json = json.escape_safe(true);
            let fit = measure_rendered(&console, &json);
            (Box::new(json), Some(fit))
        }
        Mode::Csv => {
            if let Err(err) = validate_labels(&cli) {
                eprintln!("rich: {err}");
                return ExitCode::FAILURE;
            }
            // `.tsv` only picks the fallback dialect; the sniffer reads the file
            // itself, so a comma-separated `.tsv` still renders as a table.
            let fallback = csv_fallback_delimiter(cli.resource.as_deref());
            let table = match build_csv_table(
                &content,
                fallback,
                cli.title.as_deref(),
                cli.caption.as_deref(),
            ) {
                Some(table) => table,
                // Upstream's `on_error(str(error))`. The message is CPython's,
                // verbatim, because it is the one a script would grep for.
                None => {
                    eprintln!("rich: Could not determine delimiter");
                    return ExitCode::FAILURE;
                }
            };
            // Stream undecorated CSV rows: measuring or collecting the complete
            // styled table first multiplies memory by hundreds on tall inputs.
            // Containers, alignment, paging and exports still need the full view.
            if cli.panel.is_none()
                && cli.padding.is_none()
                && cli.style.is_none()
                && cli.justify.is_none()
                && !cli.pager
                && cli.export_html.is_none()
                && cli.export_svg.is_none()
            {
                let mut options = console.options();
                options.max_width = cli.width.unwrap_or_else(|| {
                    table
                        .measure(&console, &options)
                        .maximum
                        .min(options.max_width)
                        .max(1)
                });
                let stdout = std::io::stdout();
                let mut output = std::io::BufWriter::new(stdout.lock());
                let result = table
                    .try_for_each_line(&console, &options, |line| {
                        let line = Segment::crop_lines(&line, console.width());
                        writeln!(output, "{}", console.segments_to_string(&line))
                    })
                    .and_then(|()| output.flush());
                if let Err(error) = result {
                    // A consumer such as `head` may finish before this table.
                    // Match the other stdout paths: a closed pipe is success.
                    if error.kind() == std::io::ErrorKind::BrokenPipe {
                        return ExitCode::SUCCESS;
                    }
                    eprintln!("rich: could not write CSV output: {error}");
                    return ExitCode::FAILURE;
                }
                return ExitCode::SUCCESS;
            }
            let fit = measure_rendered(&console, &table);
            (Box::new(table), Some(fit))
        }
        Mode::Syntax => {
            // `Syntax.__rich_measure__`: the widest source line, plus padding and
            // a line-number column — neither of which this CLI turns on.
            let fit = content.lines().map(cell_len).max().unwrap_or(0);
            (
                Box::new(Syntax::new(content.as_str(), language.as_str()).word_wrap(true)),
                Some(fit),
            )
        }
        // Print + auto: parse markup (Print) or take plain text (auto).
        _ => {
            let text = if mode == Mode::Print {
                console.build_text(&content)
            } else {
                Text::new(content.as_str())
            };
            let fit = text.measurement().1;
            (Box::new(text), Some(fit))
        }
    };
    decorate_and_emit(&cli, &console, &export, renderable, fit)
}

/// Turn an "everything written successfully" flag into a process exit code.
/// A failed `--export-html`/`--export-svg` write must not report success.
fn exit_code(ok: bool) -> ExitCode {
    if ok {
        ExitCode::SUCCESS
    } else {
        ExitCode::FAILURE
    }
}

/// A CSV dialect: everything `csv.Sniffer` decides and `csv.reader` consumes.
#[derive(Debug, Clone, Copy)]
struct Dialect {
    delimiter: char,
    quotechar: char,
    doublequote: bool,
    skipinitialspace: bool,
}

impl Dialect {
    /// `csv.get_dialect("excel")` (or `"excel-tab"` for a tab): upstream's
    /// fallback for a `.csv`/`.tsv` the sniffer cannot read.
    fn excel(delimiter: char) -> Self {
        Dialect {
            delimiter,
            quotechar: '"',
            doublequote: true,
            skipinitialspace: false,
        }
    }
}

/// Whether `c` is a `\w` character for CPython's `re` over `str`.
fn is_word_char(c: char) -> bool {
    c.is_alphanumeric() || c == '_'
}

/// The `[^\w\n"']` class the sniffer accepts as a candidate delimiter.
fn is_delimiter_char(c: char) -> bool {
    !is_word_char(c) && c != '\n' && c != '"' && c != '\''
}

/// The `["']` class the sniffer accepts as a candidate quote character.
fn is_quote_char(c: char) -> bool {
    c == '"' || c == '\''
}

/// One hit from the quote/delimiter scan: the quote, the delimiter bracketing
/// it (absent in the fourth, delimiter-free pattern), and whether a space sat
/// between the two.
struct QuoteHit {
    quote: char,
    delim: Option<char>,
    space: bool,
}

/// Port of `csv.Sniffer.sniff`, restricted to `delimiters` when given (rich-cli
/// passes `",\t|;"`). `None` is CPython's `csv.Error`: no delimiter found.
///
/// `doublequote` is **not** sniffed; it is left at excel's `true`. CPython
/// decides it with a regex that only fires when a `""` pair sits inside a
/// quoted field containing neither the delimiter nor a newline, and when it
/// does not fire `csv.reader` stops unescaping — `"he said ""hi"""` reads back
/// as `he said "hi"""`. Reproducing that can only ever make a well-formed file
/// render worse, and upstream's own fallback (`csv.get_dialect("excel")`, used
/// for every file the sniffer rejects) already sets it true. The divergence is
/// confined to files that use `""` escaping *and* defeat the heuristic, e.g. a
/// `""` inside a multi-line cell: there we unescape and upstream does not.
fn sniff(sample: &str, delimiters: Option<&[char]>) -> Option<Dialect> {
    let data: Vec<char> = sample.chars().collect();
    let (quote, mut delimiter, mut skipinitialspace) = guess_quote_and_delimiter(&data, delimiters);
    if delimiter.is_none() {
        let (guessed, spaced) = guess_delimiter(sample, delimiters);
        delimiter = guessed;
        skipinitialspace = spaced;
    }
    Some(Dialect {
        delimiter: delimiter?,
        // `_csv.reader` won't accept an empty quotechar, so upstream falls back
        // to `"` when the scan found no quotes at all.
        quotechar: quote.unwrap_or('"'),
        doublequote: true,
        skipinitialspace,
    })
}

/// Port of `csv.Sniffer._guess_quote_and_delimiter`: look for text enclosed in
/// two identical quotes that are themselves bracketed by the same character.
///
/// CPython uses four backreferencing regexes (`(?P=quote)`, `(?P=delim)`),
/// which no Rust regex engine can express, so they are scanned by hand below.
/// The first pattern that hits anywhere decides; the most frequent quote wins,
/// and so does the most frequent delimiter seen beside it.
fn guess_quote_and_delimiter(
    data: &[char],
    delimiters: Option<&[char]>,
) -> (Option<char>, Option<char>, bool) {
    let hits = quote_hits(data);
    if hits.is_empty() {
        return (None, None, false);
    }

    // Insertion-ordered tallies: Python's `max(dict, key=dict.get)` returns the
    // FIRST key holding the maximum, so the order these were first seen in
    // decides ties.
    let mut quotes: Vec<(char, usize)> = Vec::new();
    let mut delims: Vec<(char, usize)> = Vec::new();
    let mut spaces = 0usize;
    fn bump(table: &mut Vec<(char, usize)>, key: char) {
        match table.iter_mut().find(|(existing, _)| *existing == key) {
            Some(entry) => entry.1 += 1,
            None => table.push((key, 1)),
        }
    }
    for hit in &hits {
        bump(&mut quotes, hit.quote);
        // The fourth pattern has no delimiter group at all, so it contributes
        // only a quote — upstream `continue`s past both tallies below.
        let Some(delim) = hit.delim else { continue };
        if delimiters.is_none_or(|allowed| allowed.contains(&delim)) {
            bump(&mut delims, delim);
        }
        if hit.space {
            spaces += 1;
        }
    }

    let first_max = |table: &[(char, usize)]| -> Option<(char, usize)> {
        let mut best: Option<(char, usize)> = None;
        for &(key, count) in table {
            if best.is_none_or(|(_, seen)| count > seen) {
                best = Some((key, count));
            }
        }
        best
    };
    let quotechar = first_max(&quotes).map(|(key, _)| key);
    match first_max(&delims) {
        Some((delim, count)) => (quotechar, Some(delim), count == spaces),
        // A single column of quoted data: quotes but nothing bracketing them.
        None => (quotechar, None, false),
    }
}

/// One of CPython's four quote/delimiter patterns, scanned over the sample.
type QuoteScan = fn(&[char]) -> Vec<QuoteHit>;

/// Run CPython's four quote/delimiter patterns in order, returning the hits of
/// the first that matches anything.
fn quote_hits(data: &[char]) -> Vec<QuoteHit> {
    let scans: [QuoteScan; 4] = [
        scan_delim_quote_delim,
        scan_line_quote_delim,
        scan_delim_quote_line,
        scan_line_quote_line,
    ];
    for scan in scans {
        let hits = scan(data);
        if !hits.is_empty() {
            return hits;
        }
    }
    Vec::new()
}

/// `(?P<delim>[^\w\n"'])(?P<space> ?)(?P<quote>["']).*?(?P=quote)(?P=delim)` —
/// `,"some text",`. The ` ?` needs no backtracking: if the space is there and
/// the next character is not a quote, dropping the space only offers the space
/// itself as the quote, which it is not.
fn scan_delim_quote_delim(data: &[char]) -> Vec<QuoteHit> {
    scan_delim_quote(data, |data, quote, delim, from| {
        let mut k = from;
        while k + 1 < data.len() {
            if data[k] == quote && data[k + 1] == delim {
                return Some(k + 2);
            }
            k += 1;
        }
        None
    })
}

/// `(?P<delim>[^\w\n"'])(?P<space> ?)(?P<quote>["']).*?(?P=quote)(?:$|\n)` —
/// `,"some text"` at the end of a line.
fn scan_delim_quote_line(data: &[char]) -> Vec<QuoteHit> {
    scan_delim_quote(data, |data, quote, _delim, from| {
        let mut k = from;
        while k < data.len() {
            if data[k] == quote && (k + 1 == data.len() || data[k + 1] == '\n') {
                // `$` is zero-width and the engine prefers it, so the match ends
                // at the closing quote either way.
                return Some(k + 1);
            }
            k += 1;
        }
        None
    })
}

/// The shared `<delim><space?><quote> … ` head of patterns one and three;
/// `close` finds the closing quote and reports where the match ends.
fn scan_delim_quote(
    data: &[char],
    close: fn(&[char], char, char, usize) -> Option<usize>,
) -> Vec<QuoteHit> {
    let mut hits = Vec::new();
    let mut i = 0;
    while i < data.len() {
        if is_delimiter_char(data[i]) {
            let delim = data[i];
            let mut j = i + 1;
            let mut space = false;
            if j < data.len() && data[j] == ' ' {
                space = true;
                j += 1;
            }
            if j < data.len() && is_quote_char(data[j]) {
                let quote = data[j];
                if let Some(end) = close(data, quote, delim, j + 1) {
                    hits.push(QuoteHit {
                        quote,
                        delim: Some(delim),
                        space,
                    });
                    i = end;
                    continue;
                }
            }
        }
        i += 1;
    }
    hits
}

/// `(?:^|\n)(?P<quote>["']).*?(?P=quote)(?P<delim>[^\w\n"'])(?P<space> ?)` —
/// `"some text",` at the start of a line.
fn scan_line_quote_delim(data: &[char]) -> Vec<QuoteHit> {
    scan_line_quote(data, |data, quote, from| {
        let mut k = from;
        while k + 1 < data.len() {
            if data[k] == quote && is_delimiter_char(data[k + 1]) {
                let space = k + 2 < data.len() && data[k + 2] == ' ';
                return Some((Some(data[k + 1]), space, if space { k + 3 } else { k + 2 }));
            }
            k += 1;
        }
        None
    })
}

/// `(?:^|\n)(?P<quote>["']).*?(?P=quote)(?:$|\n)` — a whole line that is one
/// quoted field, with no delimiter to learn from.
fn scan_line_quote_line(data: &[char]) -> Vec<QuoteHit> {
    scan_line_quote(data, |data, quote, from| {
        let mut k = from;
        while k < data.len() {
            if data[k] == quote && (k + 1 == data.len() || data[k + 1] == '\n') {
                return Some((None, false, k + 1));
            }
            k += 1;
        }
        None
    })
}

/// The shared `(?:^|\n)<quote> … ` head of patterns two and four; `close`
/// reports `(delimiter, saw a space, match end)`.
#[allow(clippy::type_complexity)]
fn scan_line_quote(
    data: &[char],
    close: fn(&[char], char, usize) -> Option<(Option<char>, bool, usize)>,
) -> Vec<QuoteHit> {
    let mut hits = Vec::new();
    let mut i = 0;
    while i < data.len() {
        // `^` is zero-width at a line start; the `\n` branch consumes the
        // newline and puts the quote on the character after it. The engine tries
        // them in that order at each position.
        let mut starts: Vec<usize> = Vec::new();
        if i == 0 || data[i - 1] == '\n' {
            starts.push(i);
        }
        if data[i] == '\n' {
            starts.push(i + 1);
        }
        let mut advanced = false;
        for quote_at in starts {
            if quote_at >= data.len() || !is_quote_char(data[quote_at]) {
                continue;
            }
            let quote = data[quote_at];
            if let Some((delim, space, end)) = close(data, quote, quote_at + 1) {
                hits.push(QuoteHit {
                    quote,
                    delim,
                    space,
                });
                i = end;
                advanced = true;
                break;
            }
        }
        if !advanced {
            i += 1;
        }
    }
    hits
}

/// Port of `csv.Sniffer._guess_delimiter`: the character whose per-line
/// occurrence count is most consistent across the sample wins.
fn guess_delimiter(sample: &str, delimiters: Option<&[char]>) -> (Option<char>, bool) {
    // `filter(None, data.split('\n'))` — blank lines carry no evidence.
    let data: Vec<&str> = sample.split('\n').filter(|line| !line.is_empty()).collect();
    if data.is_empty() {
        return (None, false);
    }
    /// CPython scans `[chr(c) for c in range(127)]` — 7-bit ASCII.
    const ASCII: usize = 127;

    let chunk_length = 10.min(data.len());
    let mut iteration = 0usize;
    // Per character, an insertion-ordered list of (occurrences on a line, how
    // many lines had exactly that many) — upstream's "meta-frequency".
    let mut char_frequency: Vec<Vec<(usize, usize)>> = vec![Vec::new(); ASCII];
    // The winning (frequency, confidence) per character. Confidence can go
    // negative once every competing frequency is subtracted, hence `isize`.
    let mut modes: Vec<Option<(usize, isize)>> = vec![None; ASCII];
    let mut delims: Vec<(char, (usize, isize))> = Vec::new();

    let (mut start, mut end) = (0usize, chunk_length);
    while start < data.len() {
        iteration += 1;
        for line in &data[start..end.min(data.len())] {
            for (code, table) in char_frequency.iter_mut().enumerate() {
                let c = code as u8 as char;
                // Counted even when zero: a character absent from a line is
                // evidence against it being the delimiter.
                let freq = line.matches(c).count();
                match table.iter_mut().find(|(seen, _)| *seen == freq) {
                    Some(entry) => entry.1 += 1,
                    None => table.push((freq, 1)),
                }
            }
        }

        for (code, items) in char_frequency.iter().enumerate() {
            if items.len() == 1 && items[0].0 == 0 {
                continue;
            }
            if items.len() > 1 {
                // The first frequency with the highest count, less the sum of
                // every other count.
                let mut best = 0usize;
                for (index, item) in items.iter().enumerate() {
                    if item.1 > items[best].1 {
                        best = index;
                    }
                }
                let others: usize = items
                    .iter()
                    .enumerate()
                    .filter(|(index, _)| *index != best)
                    .map(|(_, item)| item.1)
                    .sum();
                modes[code] = Some((items[best].0, items[best].1 as isize - others as isize));
            } else if let Some(&(freq, count)) = items.first() {
                modes[code] = Some((freq, count as isize));
            }
        }

        let total = (chunk_length * iteration).min(data.len()) as f64;
        let mut consistency = 1.0f64;
        let threshold = 0.9f64;
        while delims.is_empty() && consistency >= threshold {
            for (code, mode) in modes.iter().enumerate() {
                let Some((freq, count)) = *mode else { continue };
                let c = code as u8 as char;
                if freq > 0
                    && count > 0
                    && (count as f64 / total) >= consistency
                    && delimiters.is_none_or(|allowed| allowed.contains(&c))
                {
                    delims.push((c, (freq, count)));
                }
            }
            consistency -= 0.01;
        }

        if delims.len() == 1 {
            let delim = delims[0].0;
            return (Some(delim), saw_space_after(data[0], delim));
        }

        start = end;
        end += chunk_length;
    }

    if delims.is_empty() {
        return (None, false);
    }
    if delims.len() > 1 {
        for preferred in [',', '\t', ';', ' ', ':'] {
            if delims.iter().any(|(c, _)| *c == preferred) {
                return (Some(preferred), saw_space_after(data[0], preferred));
            }
        }
    }
    // `items = [(v, k) …]; items.sort()` — ordered by the mode, then the char.
    let best = delims
        .iter()
        .max_by_key(|(c, mode)| (*mode, *c))
        .expect("delims is non-empty");
    (Some(best.0), saw_space_after(data[0], best.0))
}

/// Upstream's `skipinitialspace` test: every delimiter on the first line is
/// followed by a space.
fn saw_space_after(line: &str, delimiter: char) -> bool {
    line.matches(delimiter).count() == line.matches(&format!("{delimiter} ")).count()
}

/// What `csv.Sniffer.has_header` decides a column holds.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ColumnType {
    /// Every value so far parsed as a Python `complex`.
    Number,
    /// They did not, but all had this many characters.
    Length(usize),
}

/// Whether a column is still in play, and what it has looked like so far.
#[derive(Debug, Clone, Copy)]
enum ColumnVote {
    /// In `columnTypes` with the value `None`: no data row typed it yet.
    Untyped,
    Typed(ColumnType),
    /// `del columnTypes[col]` — the column was inconsistent.
    Dropped,
}

/// Port of `csv.Sniffer.has_header`: if a column is one consistent type in every
/// row *except* the first, the first row is a label. Each column casts one vote.
///
/// The typing is CPython's current one — a single `complex` attempt, falling
/// back to the string's length. The historical `for thisType in [int, float,
/// complex]` loop is NOT equivalent: it makes a column mixing `10` and `9.5`
/// read as inconsistent (int then float), so `price,note / 10,aa / 9.5,bbb`
/// loses its header.
///
/// `None` is CPython's `csv.Error` escaping from the re-sniff, which upstream
/// handles the same way as a failed `sniff`.
fn has_header(sample: &str) -> Option<bool> {
    // Note the missing `delimiters` argument: upstream re-sniffs here with the
    // full candidate set, not the four it renders with.
    let dialect = sniff(sample, None)?;
    let mut rows = read_csv_rows(sample, &dialect).into_iter();
    let header = rows.next()?;
    let columns = header.len();
    let mut votes = vec![ColumnVote::Untyped; columns];

    for (checked, row) in rows.enumerate() {
        // An arbitrary cap, "to keep it sane" — the 22nd data row and beyond are
        // never looked at, however inconsistent they are.
        if checked > 20 {
            break;
        }
        if row.len() != columns {
            continue;
        }
        for (col, vote) in votes.iter_mut().enumerate() {
            if matches!(vote, ColumnVote::Dropped) {
                continue;
            }
            let this = if parses_as_complex(&row[col]) {
                ColumnType::Number
            } else {
                ColumnType::Length(row[col].chars().count())
            };
            match vote {
                ColumnVote::Untyped => *vote = ColumnVote::Typed(this),
                ColumnVote::Typed(known) if *known != this => *vote = ColumnVote::Dropped,
                _ => {}
            }
        }
    }

    let mut tally = 0isize;
    for (col, vote) in votes.iter().enumerate() {
        match vote {
            ColumnVote::Dropped => {}
            // `colType` is still `None`, and `None(header[col])` raises
            // TypeError — which counts as "the header does not fit the column".
            ColumnVote::Untyped => tally += 1,
            ColumnVote::Typed(ColumnType::Length(len)) => {
                if header[col].chars().count() == *len {
                    tally -= 1;
                } else {
                    tally += 1;
                }
            }
            ColumnVote::Typed(ColumnType::Number) => {
                if parses_as_complex(&header[col]) {
                    tally -= 1;
                } else {
                    tally += 1;
                }
            }
        }
    }
    Some(tally > 0)
}

/// Whether Python's `complex(value)` would succeed — the type test at the heart
/// of `has_header`.
///
/// `complex()` is much looser than "looks like a number": it takes surrounding
/// whitespace, one level of parentheses, a sign, `inf`/`infinity`/`nan` in any
/// case, an exponent, `_` digit separators and an imaginary `j` suffix. All of
/// that is honoured. The single narrowing is the digit set — Python accepts any
/// Unicode decimal digit, this accepts ASCII — which can only ever move one
/// has-header vote, and only for a column written in non-ASCII numerals.
fn parses_as_complex(value: &str) -> bool {
    let trimmed = value.trim();
    let body = match trimmed.strip_prefix('(') {
        Some(inner) => match inner.strip_suffix(')') {
            Some(inner) => inner.trim(),
            None => return false,
        },
        None if trimmed.ends_with(')') => return false,
        None => trimmed,
    };
    if body.is_empty() {
        return false;
    }
    // `a`, `aj`, or `a±bj`. The split is the first sign that is not an
    // exponent's, so `1e-5` stays one number.
    let chars: Vec<char> = body.chars().collect();
    let split = (1..chars.len())
        .find(|&i| matches!(chars[i], '+' | '-') && !matches!(chars[i - 1], 'e' | 'E'));
    match split {
        Some(index) => {
            let at: usize = chars[..index].iter().map(|c| c.len_utf8()).sum();
            let (real, imaginary) = body.split_at(at);
            is_float_literal(real) && is_imaginary_literal(imaginary)
        }
        None => is_float_literal(body) || is_imaginary_literal(body),
    }
}

/// A Python float literal: optional sign, then `inf`/`infinity`/`nan`, or
/// digits with an optional fraction and exponent.
fn is_float_literal(value: &str) -> bool {
    let body = value.strip_prefix(['+', '-']).unwrap_or(value);
    if matches!(
        body.to_ascii_lowercase().as_str(),
        "inf" | "infinity" | "nan"
    ) {
        return true;
    }
    let chars: Vec<char> = body.chars().collect();
    let mut index = 0usize;
    let mut digits = 0usize;
    let take_digits = |index: &mut usize, digits: &mut usize| {
        while *index < chars.len() && (chars[*index].is_ascii_digit() || chars[*index] == '_') {
            if chars[*index].is_ascii_digit() {
                *digits += 1;
            }
            *index += 1;
        }
    };
    take_digits(&mut index, &mut digits);
    if index < chars.len() && chars[index] == '.' {
        index += 1;
        take_digits(&mut index, &mut digits);
    }
    if digits == 0 {
        return false;
    }
    if index < chars.len() && (chars[index] == 'e' || chars[index] == 'E') {
        index += 1;
        if index < chars.len() && matches!(chars[index], '+' | '-') {
            index += 1;
        }
        let mut exponent = 0usize;
        take_digits(&mut index, &mut exponent);
        if exponent == 0 {
            return false;
        }
    }
    index == chars.len()
}

/// `<number>j`, or a bare `j`/`+j`/`-j` (which Python reads as ±1j).
fn is_imaginary_literal(value: &str) -> bool {
    let Some(body) = value.strip_suffix(['j', 'J']) else {
        return false;
    };
    matches!(body, "" | "+" | "-") || is_float_literal(body)
}

/// Where [`read_csv_rows`] is within a record. Port of `_csv.c`'s reader states
/// (its `EAT_CRNL` is unreachable here: universal newlines ran first).
enum State {
    StartRecord,
    StartField,
    InField,
    InQuotedField,
    QuoteInQuotedField,
}

/// Parse `content` into rows of fields with `dialect`. Port of `_csv.reader`'s
/// state machine, minus the escape character (no sniffed dialect sets one) and
/// `strict` (always off, as `QUOTE_MINIMAL` leaves it).
///
/// A blank line yields an **empty** row, as `csv.reader` does — upstream drops
/// those before building the table, where a `[""]` row would have drawn a
/// spurious blank line in it. `\r` never reaches here: the reader has already
/// applied Python's universal newlines.
fn read_csv_rows(content: &str, dialect: &Dialect) -> Vec<Vec<String>> {
    // Strip a leading UTF-8 BOM so it doesn't cling to the first header cell.
    let content = content.strip_prefix('\u{feff}').unwrap_or(content);
    let mut rows: Vec<Vec<String>> = Vec::new();
    let mut row: Vec<String> = Vec::new();
    let mut field = String::new();
    let mut state = State::StartRecord;

    for c in content.chars() {
        match state {
            State::StartRecord => {
                if c == '\n' {
                    rows.push(Vec::new());
                } else {
                    state = State::StartField;
                    // Re-dispatch this character as the start of a field.
                    read_csv_char(c, dialect, &mut state, &mut field, &mut row, &mut rows);
                }
            }
            _ => read_csv_char(c, dialect, &mut state, &mut field, &mut row, &mut rows),
        }
    }
    if !matches!(state, State::StartRecord) {
        row.push(std::mem::take(&mut field));
        row.shrink_to_fit();
        rows.push(std::mem::take(&mut row));
    }
    rows
}

/// One character of [`read_csv_rows`]'s state machine, for every state but
/// `StartRecord`.
fn read_csv_char(
    c: char,
    dialect: &Dialect,
    state: &mut State,
    field: &mut String,
    row: &mut Vec<String>,
    rows: &mut Vec<Vec<String>>,
) {
    let end_record = |field: &mut String, row: &mut Vec<String>, rows: &mut Vec<Vec<String>>| {
        row.push(std::mem::take(field));
        // Completed records keep only their fields, not Vec's spare growth slots.
        row.shrink_to_fit();
        rows.push(std::mem::take(row));
    };
    match state {
        State::StartRecord => unreachable!("handled by the caller"),
        State::StartField => {
            if c == '\n' {
                end_record(field, row, rows);
                *state = State::StartRecord;
            } else if c == dialect.quotechar {
                *state = State::InQuotedField;
            } else if c == ' ' && dialect.skipinitialspace {
                // Stay in StartField, swallowing the padding.
            } else if c == dialect.delimiter {
                row.push(std::mem::take(field));
            } else {
                field.push(c);
                *state = State::InField;
            }
        }
        State::InField => {
            if c == '\n' {
                end_record(field, row, rows);
                *state = State::StartRecord;
            } else if c == dialect.delimiter {
                row.push(std::mem::take(field));
                *state = State::StartField;
            } else {
                field.push(c);
            }
        }
        State::InQuotedField => {
            if c == dialect.quotechar {
                *state = if dialect.doublequote {
                    State::QuoteInQuotedField
                } else {
                    // Without doublequote the quote simply ends the quoted part;
                    // anything after it, quotes included, is literal.
                    State::InField
                };
            } else {
                field.push(c);
            }
        }
        State::QuoteInQuotedField => {
            if c == dialect.quotechar {
                field.push(c);
                *state = State::InQuotedField;
            } else if c == dialect.delimiter {
                row.push(std::mem::take(field));
                *state = State::StartField;
            } else if c == '\n' {
                end_record(field, row, rows);
                *state = State::StartRecord;
            } else {
                field.push(c);
                *state = State::InField;
            }
        }
    }
}

/// Whether `value` matches rich-cli's `is_number`, i.e. Python's
/// `re.fullmatch(r"\-?[0-9]*?\.?[0-9]*?", value)`.
///
/// Note how loose that is: `-`, `.`, `-.` and the empty string all pass, and a
/// leading space does not. The caller only asks about non-empty cells.
fn is_number(value: &str) -> bool {
    let body = value.strip_prefix('-').unwrap_or(value);
    let (integer, fraction) = match body.split_once('.') {
        Some((integer, fraction)) => (integer, Some(fraction)),
        None => (body, None),
    };
    let digits = |part: &str| part.bytes().all(|b| b.is_ascii_digit());
    digits(integer) && fraction.is_none_or(digits)
}

/// Build the CSV table for `content`, sniffing the dialect and the header the
/// way upstream's `render_csv` does.
///
/// `fallback_delimiter` is the dialect to use when `csv.Sniffer` raises, and
/// `None` means upstream has none to offer: its `except csv.Error` arm falls
/// back to `csv.get_dialect("excel")` for a resource whose name ends `.csv`
/// and to `"excel-tab"` for one ending `.tsv`, and for **everything else** —
/// any other extension, a bare name, a URL, stdin — calls
/// `on_error(str(error))`, which prints the message and exits non-zero.
///
/// So `None` here is a failure, and the caller must report it. Rendering a
/// fabricated one-column table at exit 0 instead is the worst possible
/// outcome: `rich --csv "$f" && publish` proceeds on a file nothing could
/// parse, with empty stderr to say so.
fn build_csv_table(
    content: &str,
    fallback_delimiter: Option<char>,
    title: Option<&str>,
    caption: Option<&str>,
) -> Option<Table> {
    // The sniffer sees only the first 1024 *characters* — upstream's
    // `csv_data[:1024]` — however long the file is.
    let sample: String = content.chars().take(1024).collect();
    let sniffed = sniff(&sample, Some(&[',', '\t', '|', ';'])).zip(has_header(&sample));
    let (dialect, header) = match sniffed {
        Some(sniffed) => sniffed,
        None => (Dialect::excel(fallback_delimiter?), true),
    };
    Some(render_csv(
        read_csv_rows(content, &dialect),
        header,
        title,
        caption,
    ))
}

/// The dialect upstream falls back to when `csv.Sniffer` cannot read
/// `resource`, or `None` when it has none — a failure, not a default.
///
/// Upstream tests the **resource string**, not the detected language:
/// `resource.lower().endswith(".csv")` then `.endswith(".tsv")`. So a URL
/// ending `.tsv` gets the tab dialect, and `-` (stdin) gets nothing.
fn csv_fallback_delimiter(resource: Option<&str>) -> Option<char> {
    let name = resource.unwrap_or_default().to_lowercase();
    if name.ends_with(".csv") {
        Some(',')
    } else if name.ends_with(".tsv") {
        Some('\t')
    } else {
        None
    }
}

/// Build a table from parsed CSV `rows`, mirroring rich-cli's `render_csv`: a
/// blue border, `HEAVY_HEAD` when the sniffer found a header and `SQUARE` when
/// it did not, and any all-numeric column right-justified with bold-green body
/// and header cells.
fn render_csv(
    rows: Vec<Vec<String>>,
    has_header: bool,
    title: Option<&str>,
    caption: Option<&str>,
) -> Table {
    let mut table = Table::new()
        .border_style(Style::parse("blue").expect("valid style"))
        .show_header(has_header)
        .box_set(if has_header { HEAVY_HEAD } else { SQUARE });
    if let Some(title) = title {
        table = table.title(title);
    }
    if let Some(caption) = caption {
        table = table.caption(caption);
    }

    let empty: Vec<String> = Vec::new();
    let (header, body) = if has_header {
        match rows.split_first() {
            Some((header, body)) => (header, body),
            None => return table,
        }
    } else {
        (&empty, rows.as_slice())
    };
    // `[row for row in rows if row]`: a blank line is not a table row.
    let data: Vec<&Vec<String>> = body.iter().filter(|row| !row.is_empty()).collect();

    // A row may carry more fields than the header names, and upstream's
    // `table.add_row(*row)` grows the table to hold them. Columns came from the
    // header alone, so those fields had nowhere to go and were dropped -- a
    // silent data loss in a tool whose job is showing you the file.
    let widest = data.iter().map(|row| row.len()).max().unwrap_or(0);
    let columns = header.len().max(widest);

    for index in 0..columns {
        // A column is numeric when no data cell is a non-empty non-number. A
        // row too SHORT to reach the column disqualifies it (upstream's
        // `except Exception: break`), while an empty cell does not; and an
        // empty data set counts as numeric, as upstream's `for … else` does.
        let numeric = data.iter().all(|row| match row.get(index) {
            Some(value) => value.is_empty() || is_number(value),
            None => false,
        });
        let name = header.get(index).map(String::as_str).unwrap_or("");
        if numeric {
            table.add_column_justify(name, Justify::Right);
            table.column_style(Style::parse("bold green").expect("valid style"));
            table.column_header_fill(Style::parse("bold green").expect("valid style"));
        } else {
            table.add_column(name);
        }
    }
    // Measurement/style inference is complete. Move the parsed cells into the
    // table rather than retaining and cloning the complete input row set.
    drop(data);
    table.extend_owned_rows(
        rows.into_iter()
            .skip(usize::from(has_header))
            .filter(|row| !row.is_empty())
            .collect(),
    );
    table
}

/// Join a notebook cell/output `source` field (a JSON string, or an array of
/// line strings that already include their trailing newlines).
fn join_source(value: &serde_json::Value) -> String {
    match value {
        serde_json::Value::String(s) => s.clone(),
        serde_json::Value::Array(a) => a.iter().filter_map(|v| v.as_str()).collect(),
        _ => String::new(),
    }
}

/// Join a notebook `traceback`, whose elements are lines WITHOUT trailing
/// newlines (unlike `source`/`text`, which carry their own). Using
/// [`join_source`] here fused a whole stack trace onto one line.
fn join_traceback(value: &serde_json::Value) -> String {
    match value {
        serde_json::Value::String(s) => s.clone(),
        serde_json::Value::Array(a) => a
            .iter()
            .filter_map(|v| v.as_str())
            .collect::<Vec<_>>()
            .join(
                "
",
            ),
        _ => String::new(),
    }
}

/// Build an `In [n]:` / `Out[n]:` execution-count label. Port of rich-cli's
/// `[green]In [[#66ff00]{count}[/#66ff00]]:[/green]` markup (built as spans to
/// avoid markup-escaping the literal brackets).
fn io_label(word: &str, count: Option<i64>, base: &str, number: &str) -> Text {
    let base_style = Style::parse(base).ok();
    let number_style = Style::parse(number).ok();
    let n = count.map_or_else(|| " ".to_string(), |c| c.to_string());
    let mut text = Text::new("");
    text.append(&format!("{word}["), base_style.clone().map(Into::into));
    text.append(&n, number_style.map(Into::into));
    text.append("]:", base_style.map(Into::into));
    text
}

/// Port of the Group returned by rich-cli's `render_ipynb`. Keeping the cells
/// composable lets the common padding/panel/style/width/alignment chain apply.
struct Notebook {
    items: Vec<Box<dyn Renderable>>,
    // Console.print(justify=...) also reaches the group's Text children in
    // upstream. Their individual lines align within the group's measured width.
    justify: Option<Justify>,
}

impl Renderable for Notebook {
    fn rich_render(&self, console: &Console, options: &ConsoleOptions) -> Vec<Segment> {
        let mut options = options.clone();
        if let Some(justify) = self.justify {
            options.justify = justify;
        }
        let mut segments = Vec::new();
        for item in &self.items {
            let rendered = item.rich_render(console, &options);
            if !rendered.is_empty() {
                segments.extend(rendered);
                segments.push(Segment::line());
            }
        }
        // Console supplies the final newline. Empty groups produce no output.
        if !segments.is_empty() {
            segments.pop();
        }
        segments
    }

    fn measure(&self, console: &Console, options: &ConsoleOptions) -> Measurement {
        self.items
            .iter()
            .map(|item| item.measure(console, options))
            .fold(Measurement::new(0, 0), |width, item| {
                Measurement::new(
                    width.minimum.max(item.minimum),
                    width.maximum.max(item.maximum),
                )
            })
    }
}

/// Text.from_ansi joins decoded lines, preserving their style spans.
fn notebook_ansi(source: &str) -> Text {
    let mut result = Text::new("");
    for (index, line) in AnsiDecoder::new().decode(source).iter().enumerate() {
        if index > 0 {
            result.append("\n", None);
        }
        result = result.append_text(line);
    }
    result
}

/// Port of rich-cli 1.8.1's notebook cell/output grouping. Parse once, then use
/// the same renderable for terminal output, paging and recorded exports.
fn build_ipynb(
    notebook: &serde_json::Value,
    hyperlinks: bool,
    justify: Option<Justify>,
) -> Notebook {
    let language = notebook["metadata"]["kernelspec"]["language"]
        .as_str()
        .or_else(|| notebook["metadata"]["language_info"]["name"].as_str())
        .unwrap_or("python");
    let empty = Vec::new();
    let mut items: Vec<Box<dyn Renderable>> = Vec::new();
    let mut new_line = true;
    for cell in notebook["cells"].as_array().unwrap_or(&empty) {
        if new_line {
            items.push(text(""));
        }
        if cell.get("execution_count").is_some() {
            items.push(Box::new(io_label(
                "In ",
                cell["execution_count"].as_i64().filter(|n| *n != 0),
                "green",
                "#66ff00",
            )));
        }
        let source = join_source(&cell["source"]);
        items.push(match cell["cell_type"].as_str().unwrap_or("") {
            "markdown" => Box::new(build_markdown(&source, hyperlinks)),
            "code" => Box::new(
                Panel::new(Box::new(Syntax::new(&source, language)))
                    .border_style(Style::parse("dim").expect("valid style")),
            ),
            _ => text(&source),
        });
        new_line = true;
        for output in cell["outputs"].as_array().unwrap_or(&empty) {
            let rendered = match output["output_type"].as_str().unwrap_or("") {
                "stream" => {
                    new_line = false;
                    notebook_ansi(&join_source(&output["text"]))
                }
                "error" => {
                    new_line = true;
                    notebook_ansi(join_traceback(&output["traceback"]).trim_end())
                }
                "execute_result" => {
                    new_line = true;
                    let mut label = io_label(
                        "Out",
                        output["execution_count"].as_i64().filter(|n| *n != 0),
                        "red",
                        "#ee4b2b",
                    );
                    label.append("\n", None);
                    label.append_text(&notebook_ansi(&join_source(&output["data"]["text/plain"])))
                }
                _ => continue,
            };
            items.push(Box::new(rendered));
        }
    }
    Notebook { items, justify }
}

#[cfg(feature = "art")]
fn diff_threshold_exceeded(changed: f32, limit: f32) -> bool {
    // Use the formatter's rounding for BOTH displayed operands, including
    // ties. f32::round uses a different tie rule from the report's formatting.
    let displayed = |value: f32| {
        format!("{value:.1}")
            .parse::<f32>()
            .expect("formatted percentage is a number")
    };
    displayed(changed) > displayed(limit)
}

/// Compare two images perceptually and report where they differ.
///
/// Prints a heat map of the ΔE field plus a ranked table of changed regions.
/// The table is the point: it is text, so it survives a pipe, a log, and a CI
/// transcript, which a picture does not.
///
/// With `--threshold`, exits non-zero when the changed percentage exceeds it,
/// which is what makes this usable as a visual-regression gate.
#[cfg(feature = "art")]
fn run_diff(cli: &Cli, console: &Console, export: &Export) -> ExitCode {
    use rich::Table;
    use rich_art::imagediff::{diff, DiffSettings};
    use rich_art::{AsciiArt, BlockArt, SixelArt};

    let (before_path, after_path) = (&cli.resources[0], &cli.resources[1]);
    // The directory check reached the plain read path but not this one, so
    // `rich --diff a.png somedir` still reported "Access is denied".
    let open = |path: &String| {
        if std::path::Path::new(path).is_dir() {
            eprintln!("rich: cannot read {path}: is a directory, not a file");
            return None;
        }
        match rich_art::image::open(path) {
            Ok(image) => Some(image),
            Err(err) => {
                use rich_art::image::error::{ImageFormatHint, UnsupportedErrorKind};
                let hint = match &err {
                    rich_art::image::ImageError::Unsupported(error) => match error.kind() {
                        UnsupportedErrorKind::Format(ImageFormatHint::PathExtension(ext)) =>
                            Some(format!("unsupported image extension {}; use a supported image format such as PNG or JPEG", ext.display())),
                        _ => None,
                    },
                    _ => None,
                };
                eprintln!(
                    "rich: cannot read {path}: {}",
                    hint.unwrap_or_else(|| err.to_string())
                );
                None
            }
        }
    };
    let (Some(before), Some(after)) = (open(before_path), open(after_path)) else {
        return ExitCode::FAILURE;
    };

    let report = match diff(&before, &after, &DiffSettings::default()) {
        Ok(report) => report,
        Err(err) => {
            eprintln!("rich: {err}");
            return ExitCode::FAILURE;
        }
    };

    let width = cli.width.unwrap_or_else(|| console.width());
    let changed = report.changed_fraction * 100.0;
    let naive = report.naive_changed_fraction * 100.0;

    // Decided before rendering so the verdict can be part of the output (and
    // therefore part of an --export-svg capture), while the exit code is
    // settled outside the closure.
    // Compare the number that is PRINTED, not the one behind it. Comparing full
    // precision against a one-decimal display produced "FAIL 5.4% changed, limit
    // 5.4%" -- a verdict that contradicts itself and cannot be explained from
    // the output, which is what anyone tuning a threshold to the reported figure
    // runs straight into.
    let failed = cli
        .diff_threshold
        .is_some_and(|limit| diff_threshold_exceeded(changed, limit));

    let render_report = |c: &Console, for_export: bool| {
        // Leave room for the summary, the table and the prompt, so the top of
        // the picture is not scrolled off before the reader sees it.
        let rows_cap = console.height().saturating_sub(14).clamp(6, 30);

        // Resolve `auto` from what this console can ACTUALLY do, not from the
        // --no-color flag alone. Redirected output has no colour, and a
        // half-block render without colour is a solid rectangle of identical
        // characters -- 30 rows carrying no information. Sixel is a control
        // sequence, so it is dropped entirely when the destination is not a
        // terminal.
        let has_color = c.color_system().is_some() && !cli.no_color;
        let is_terminal = c.is_terminal();
        let mut mode = cli.image_mode;
        if mode == ImageMode::Auto {
            if !has_color && !for_export {
                eprintln!("rich: auto image mode has no terminal colour, drawing the diff as ASCII instead");
            }
            mode = if !has_color {
                ImageMode::Ascii
            } else if is_terminal && rich_art::sixel::is_probably_supported() {
                ImageMode::Sixel
            } else {
                ImageMode::Blocks
            };
        }

        // An explicit choice still has to produce something. Downgrade rather
        // than emit a rectangle of identical blocks or nothing at all, and say
        // why on stderr so the change is visible rather than mysterious.
        if mode == ImageMode::Blocks && !has_color {
            if !for_export {
                eprintln!("rich: no colour available, drawing the diff as ASCII art");
            }
            mode = ImageMode::Ascii;
        }
        if mode == ImageMode::Sixel && !is_terminal {
            if !for_export {
                eprintln!(
                    "rich: Sixel graphics need a terminal, drawing the diff as {} instead",
                    if has_color { "blocks" } else { "ASCII art" }
                );
            }
            mode = if has_color {
                ImageMode::Blocks
            } else {
                ImageMode::Ascii
            };
        }

        match mode {
            ImageMode::None => {}
            ImageMode::Ascii => c.print(
                &AsciiArt::new(report.heatmap())
                    .width(width)
                    .color(has_color),
            ),
            ImageMode::Blocks => c.print(
                &BlockArt::new(report.heatmap())
                    .width(width)
                    .height(rows_cap),
            ),
            ImageMode::Sixel => {
                let art = SixelArt::new(report.heatmap())
                    .width(width)
                    .height(rows_cap);
                // Encoding can still fail on a terminal; the report must stay
                // useful, so fall back rather than leaving an empty gap.
                if art.encode(width).is_some() {
                    c.print(&art);
                } else {
                    eprintln!("rich: could not encode Sixel, drawing the diff as blocks");
                    c.print(
                        &BlockArt::new(report.heatmap())
                            .width(width)
                            .height(rows_cap),
                    );
                }
            }
            ImageMode::Auto => unreachable!("resolved above"),
        }
        // The blank line separates the picture from the summary, so it belongs
        // to the picture — with --image-mode none it was just a stray first
        // line in every report and every redirected file.
        if mode != ImageMode::None {
            c.print_str("");
        }
        c.print_str(&format!(
            "[bold]{changed:.1}%[/] of the canvas changed perceptibly \
             [dim](a plain pixel diff would say {naive:.1}%)[/]"
        ));

        if report.regions.is_empty() {
            c.print_str("[dim]No region large enough to report.[/]");
        } else {
            let mut table = Table::new().title("Where it changed");
            table.add_column("#");
            table.add_column_justify("Share", rich::Justify::Right);
            table.add_column_justify("Mean ΔE", rich::Justify::Right);
            table.add_column_justify("Area px", rich::Justify::Right);
            table.add_column("Box (x,y w×h)");
            for (rank, r) in report.regions.iter().enumerate() {
                table.add_row(&[
                    &format!("{}", rank + 1),
                    &format!("{:.0}%", r.share_of_change * 100.0),
                    &format!("{:.1}", r.mean_delta_e),
                    &format!("{}", r.area_px),
                    &format!("{},{} {}×{}", r.x, r.y, r.width, r.height),
                ]);
            }
            c.print(&table);
        }

        // The gate is compared against the perceptual figure, never the naive
        // one — gating on a pixel diff is what makes visual regression testing
        // useless in the first place.
        if let Some(limit) = cli.diff_threshold {
            if failed {
                c.print_str(&format!(
                    "[bold red]FAIL[/] {changed:.1}% changed, limit {limit:.1}%"
                ));
            } else {
                c.print_str(&format!(
                    "[bold green]OK[/] {changed:.1}% changed, within {limit:.1}%"
                ));
            }
        }
    };

    let terminal_only = Export {
        html_path: None,
        svg_path: None,
        ..*export
    };
    let mut wrote = emit(console, &terminal_only, |c| render_report(c, false));
    if export.html_path.is_some() || export.svg_path.is_some() {
        // HTML/SVG support truecolor independently of stdout. Render the already
        // loaded report for that destination; never reread images or recompute
        // the comparison. A nonterminal console prevents Sixel control data.
        let mut export_console = Console::builder()
            .force_terminal(false)
            .color_system(Some(ColorSystem::Truecolor))
            .no_color(cli.no_color)
            .width(console.width())
            .height(console.height())
            .theme(console.theme().clone())
            .build();
        export_console.install_extensions();
        let segments = export_console.record_output(|c| render_report(c, true));
        wrote = save_exports(&export_console, export, &segments) && wrote;
    }

    if !wrote || failed {
        return ExitCode::FAILURE;
    }
    ExitCode::SUCCESS
}

/// Animate every `--gif` resource at once, sharing the console width.
#[cfg(feature = "art")]
fn play_gifs(cli: &Cli, console: &Console) -> ExitCode {
    use rich_art::{AnimatedArt, Repeat, Stage};

    if cli.resources.is_empty() {
        eprintln!("rich: --gif needs at least one GIF path");
        return ExitCode::FAILURE;
    }
    let count = cli.resources.len();
    const GAP: usize = 2;

    // Share the width between the animations, leaving room for the gaps.
    let total = cli.width.unwrap_or_else(|| console.width());
    let per_gif = total
        .saturating_sub(GAP * count.saturating_sub(1))
        .checked_div(count)
        .unwrap_or(total)
        .max(8);

    let repeat = match cli.loops {
        Some(0) => Repeat::Forever,
        Some(n) => Repeat::Times(n),
        None => Repeat::Times(1),
    };

    let mut stage = Stage::new().gap(GAP);
    for path in &cli.resources {
        match AnimatedArt::from_path(path) {
            Ok(art) => {
                stage = stage.with(
                    art.width(per_gif)
                        .blocks(cli.extensions.gif_blocks())
                        .color(!cli.no_color)
                        .repeat(repeat)
                        // Colour art is byte-heavy; keep it comfortable.
                        .max_fps(30.0),
                );
            }
            Err(err) => {
                eprintln!("rich: cannot read {path}: {err}");
                return ExitCode::FAILURE;
            }
        }
    }

    if !console.is_terminal() {
        eprintln!("rich: GIF animation needs a terminal; rendering the first frame only");
    }

    // `play` needs its own console (it moves into the Live display).
    let mut builder = Console::builder().no_color(cli.no_color);
    if let Some(width) = cli.width {
        builder = builder.width(width);
    }
    match stage.play_stdout(builder.build()) {
        Ok(()) => ExitCode::SUCCESS,
        Err(err) => {
            eprintln!("rich: playback failed: {err}");
            ExitCode::FAILURE
        }
    }
}

/// Without the `art` feature there is no GIF support.
#[cfg(not(feature = "art"))]
fn play_gifs(_cli: &Cli, _console: &Console) -> ExitCode {
    eprintln!("rich: this build has no GIF support (rebuild with the `art` feature)");
    ExitCode::FAILURE
}

/// Where a render action's output goes: straight to the terminal, or captured
/// into a self-contained HTML or SVG document.
struct Export<'a> {
    /// `--export-html PATH`, if given.
    html_path: Option<&'a str>,
    /// `--export-svg PATH`, if given.
    svg_path: Option<&'a str>,
    /// Document title for the SVG frame (the resource's file name).
    svg_title: &'a str,
    /// `--pager`: page the terminal output instead of writing it straight out.
    pager: bool,
}

/// Render once and deliver it everywhere it was asked for.
///
/// The exports do **not** replace the terminal output — upstream prints the
/// resource *and* saves the files, and both `--export-html` and `--export-svg`
/// may be given together. So when either is set the render is recorded once and
/// the same segments are turned into terminal bytes, HTML and SVG. Diff reports
/// use separate destination capabilities after loading/comparing the images;
/// ordinary input renderables are recorded once here.
///
/// Returns false if a file could not be written, so the caller can exit non-zero.
fn emit(console: &Console, export: &Export, render: impl FnOnce(&Console)) -> bool {
    if export.html_path.is_none() && export.svg_path.is_none() {
        if export.pager {
            // Keep styles: unlike a plain `console.pager()`, the point of `rich
            // --pager` is to page *rich* output.
            if let Err(err) = console.page(true, render) {
                eprintln!("rich: cannot page output: {err}");
                return false;
            }
        } else {
            render(console);
        }
        return true;
    }

    let segments = console.record_output(render);
    let mut ok = true;

    // The terminal still gets the output, exports or not.
    let terminal = console.segments_to_string(&segments);
    if export.pager {
        // The text is already rendered, so hand it straight to the pager
        // rather than re-rendering through `Console::page`.
        if let Err(err) = rich::pager::Pager::show(&rich::pager::SystemPager, &terminal) {
            eprintln!("rich: cannot page output: {err}");
            ok = false;
        }
    } else {
        print!("{terminal}");
    }

    save_exports(console, export, &segments) && ok
}

fn save_exports(console: &Console, export: &Export, segments: &[Segment]) -> bool {
    let mut ok = true;
    if let Some(path) = export.html_path {
        // CSS-class stylesheet form, as upstream's `save_html` default.
        let html = rich::export::export_html_classes(segments, &DEFAULT_TERMINAL_THEME);
        if let Err(err) = std::fs::write(path, html) {
            eprintln!("rich: failed to save HTML: {err}");
            ok = false;
        }
    }
    if let Some(path) = export.svg_path {
        let svg = rich::svg::export_svg(
            segments,
            &rich::SVG_EXPORT_THEME,
            export.svg_title,
            // Upstream derives this id by hashing Python reprs; a fixed one keeps
            // our output deterministic (DIVERGENCES #15).
            "rich-cli",
            console.width(),
        );
        if let Err(err) = std::fs::write(path, svg) {
            eprintln!("rich: failed to save SVG: {err}");
            ok = false;
        }
    }
    ok
}

fn print_help() {
    let extension_help = rich_ext::cli::HELP;
    // A RAW string: `\`-continuations would eat the leading spaces of every
    // line and print the whole thing flush-left.
    println!(
        r#"rich {VERSION} — Rust port of the rich-cli terminal toolbox

USAGE:
    rich [OPTIONS] [RESOURCE]

RESOURCE is a file path, an http(s) URL, or `-` for stdin. Everything after a
bare `--` is a RESOURCE, however much it looks like an option. Input modes with
no RESOURCE read stdin until EOF; `-p -` reads markup from stdin too. Terminal
stdin shows an input hint. Repeated scalar options use their last value.

RENDER MODE (choose at most one; default auto-detects .md/.json/.csv/.tsv/.ipynb
by extension — anything else with a file extension is syntax-highlighted):
    -p, --print      Treat RESOURCE as literal markup TEXT, not a file path
    -m, --markdown   Render RESOURCE as Markdown
    -j, --json       Pretty-print RESOURCE as JSON
    -x, --syntax     Syntax-highlight RESOURCE (language from its extension)
        --csv        Render RESOURCE as a CSV/TSV table
        --ipynb      Render RESOURCE as a Jupyter notebook
        --gif        Animate GIFs side by side; pipes receive the first frame
        --loop N     With --gif, repeat N times (default 1; 0 = forever)
        --rule       Draw a horizontal rule (RESOURCE is its title)
        --diff       Perceptually compare two images (needs exactly two)

OPTIONS:
    -w, --width N    Render the output N columns wide (the console keeps its
                     own width, so --left/--center/--right still use it)
        --image-mode M
                     With --diff, how to draw the picture: auto (default),
                     sixel (real pixels), blocks, ascii, none
{extension_help}
        --threshold PCT
                     With --diff, exit non-zero above PCT% changed.
                     Also sets the exit code: 0 within, 1 over.
        --left       Left-justify output
        --center     Center output
        --right      Right-justify output
    -o, --export-html PATH
                     Also write a self-contained HTML document to PATH
        --export-svg PATH
                     Also write an SVG document to PATH. Unlike the HTML,
                     it references its font from a CDN, so it is not
                     self-contained offline.
        --panel BOX  Wrap output in a panel, shrunk to fit its content
                     (ascii/ascii2/square/rounded/heavy/double; none = no panel)
        --padding P  Wrap output in padding (1, 2, or 4 comma-separated ints)
    -e, --expand     Make --panel/--padding fill the width instead of fitting
                     (implied by --width)
        --title T    Panel title; also the CSV table's title
        --caption T  Panel subtitle; also the CSV table's caption
    -y, --hyperlinks Render a Markdown link as a clickable OSC 8 hyperlink.
                     Off by default, which shows the URL as `text (url)`
    -s, --style S    Style laid under the whole output, e.g. "bold red"
    -S, --panel-style S
                     Panel border style, e.g. "dim" (with --panel)
        --pager      Page via MANPAGER, then PAGER, then less/more.com
        --no-color   Disable colored output (as does a non-empty NO_COLOR)
    -h, --help       Show this help
    -V, --version    Show the rs-rich-cli package version

ENVIRONMENT:
    NO_COLOR         Any non-empty value disables colour
    COLUMNS          Console width (default 80 when unavailable)
    MANPAGER, PAGER   Pager command; fallback is less (Unix), more.com (Windows)
    FORCE_COLOR      Not supported; redirected stdout stays plain
    RICH_SIXEL       0/1 overrides Sixel detection for --image-mode auto

With no RESOURCE and no mode flag, a capability demo is shown. Layout, style,
paging, hyperlinks and export options require a resource or render mode.
"#
    );
}

fn run_demo(no_color: bool) {
    // Force truecolor so the demo looks the same regardless of TERM — but only
    // when it is actually going to a terminal. Forcing it unconditionally wrote
    // escape sequences into a pipe, and made `--no-color` a no-op on this path
    // alone while every other mode honoured it.
    let to_terminal = std::io::stdout().is_terminal() && !no_color;
    let mut console = Console::builder()
        .force_terminal(to_terminal)
        .no_color(no_color)
        .color_system(if to_terminal {
            Some(ColorSystem::Truecolor)
        } else {
            None
        })
        // `[error]`/`[warning]`/`[info]` are rich-ext's additions, not upstream
        // styles — the core theme is a faithful 154-entry port.
        .theme(rich_ext::extended_theme())
        .build();
    console.install_extensions();

    console.print(&Rule::new("rs-rich-cli"));
    console.print_str("[bold magenta]rs-rich-cli[/] — a Rust port of [italic]rich[/]");
    console.print_str("Everything below is byte-parity-tested against Python rich 15.0.0.");

    // Markup, color, theme, and the rich-ext highlighter.
    console.print(&Rule::new("markup · color · theme · extension"));
    console.print_str(
        "Styles:   [bold]bold[/] [dim]dim[/] [italic]italic[/] [underline]underline[/] [reverse]reverse[/]",
    );
    console.print_str(
        "Color:    [red]red[/] [green]green[/] [blue]blue[/] [#ff8800]#ff8800[/] [white on blue]on blue[/]",
    );
    console.print_str("Theme:    [error]error[/], [warning]warning[/], [info]info[/]");
    console.print_str("Extension: numbers like 3.14 and 2026 are auto-highlighted");
    // Built-in ReprHighlighter (highlight=true): auto-colors numbers, bools,
    // strings, paths, calls, etc.
    // A second console, so it needs the same terminal/colour decision as the
    // main one — building it with force_terminal(true) unconditionally was what
    // leaked escape sequences into a pipe after the demo itself stopped.
    let hl = Console::builder()
        .force_terminal(to_terminal)
        .no_color(no_color)
        .color_system(if to_terminal {
            Some(ColorSystem::Truecolor)
        } else {
            None
        })
        .highlight(true)
        .build();
    hl.print_str("Highlight:  result = func(42, True, None, '/usr/bin')");
    // ISO8601Highlighter — colors date/time/timezone fields.
    let mut stamp = Text::new("2023-06-15T13:45:30+02:00");
    ISO8601Highlighter::new().highlight(&mut stamp);
    console.print(&Text::new("ISO 8601:   ").append_text(&stamp));
    console.print_str("Emoji:     :rocket: :fire: :sparkles: :thumbs_up: :snake: :coffee:");

    // Rule variants (title alignment).
    console.print(&Rule::new("rule"));
    console.print(&Rule::line());
    console.print(&Rule::new("centered"));
    console.print(&Rule::new("left").align(HorizontalAlign::Left));
    console.print(&Rule::new("right").align(HorizontalAlign::Right));

    // Panels with different boxes.
    console.print(&Rule::new("panel"));
    console.print(&Panel::new(text("rounded box (default)")).title("rounded"));
    console.print(
        &Panel::new(text("square box"))
            .box_set(SQUARE)
            .title("square"),
    );
    console.print(
        &Panel::new(text("double box"))
            .box_set(DOUBLE)
            .title("double"),
    );
    console.print(
        &Panel::new(text("title + subtitle"))
            .title("top")
            .subtitle("bottom"),
    );
    // Legacy-Windows box substitution: a ROUNDED panel falls back to SQUARE.
    let legacy = Console::builder()
        .force_terminal(true)
        .color_system(Some(ColorSystem::Truecolor))
        .width(console.width())
        .legacy_windows(true)
        .build();
    legacy.print(&Panel::new(text("rounded → square on legacy Windows")).title("legacy"));

    // Padding (shown inside a panel so the blank space is visible).
    console.print(&Rule::new("padding"));
    console.print(
        &Panel::new(Box::new(Padding::new(text("padded (1, 4)"), (1, 4, 1, 4)))).title("padding"),
    );

    // Styled — lay one style under an entire renderable.
    console.print(&Rule::new("styled"));
    console.print(&Styled::new(
        Box::new(Panel::new(text("green under the whole panel")).title("styled")),
        Style::parse("green").unwrap(),
    ));

    // Horizontal alignment (fills the console width).
    console.print(&Rule::new("align"));
    console.print(&Align::left(text("← left")));
    console.print(&Align::center(text("center")));
    console.print(&Align::right(text("right →")));

    // Text justify (via print(justify=…)).
    console.print(&Rule::new("justify"));
    console.print_justified("left justified", Justify::Left);
    console.print_justified("centered", Justify::Center);
    console.print_justified("right justified", Justify::Right);

    // Constrain — same panel, capped to 24 cells.
    console.print(&Rule::new("constrain (width 24)"));
    console.print(&Constrain::new(
        Box::new(Panel::new(text("constrained")).title("≤24")),
        Some(24),
    ));

    // Table.
    console.print(&Rule::new("table"));
    let mut table = Table::new().title("ported renderables");
    // A styled column and a fixed-width column (content wraps with ellipsis).
    table
        .add_column("Renderable")
        .column_style(Style::parse("cyan").unwrap());
    table.add_column("Module").column_width(12);
    table.add_column_justify("Parity", Justify::Center);
    for (renderable, module, parity) in [
        ("Text / markup", "text, markup", "✓"),
        ("Rule", "rule", "✓"),
        ("Panel", "panel", "✓"),
        ("Padding", "padding", "✓"),
        ("Align", "align", "✓"),
        ("Constrain", "constrain", "✓"),
        ("Columns", "columns", "✓"),
        ("Table", "table", "✓"),
        ("Tree", "tree", "✓"),
        ("ProgressBar", "progress_bar", "✓"),
    ] {
        table.add_row(&[renderable, module, parity]);
    }
    console.print(&table);

    // Columns — packs items into as many columns as fit the width.
    console.print(&Rule::new("columns"));
    let months = [
        "January",
        "February",
        "March",
        "April",
        "May",
        "June",
        "July",
        "August",
        "September",
        "October",
        "November",
        "December",
    ];
    console.print(&Columns::new(
        months.iter().map(|m| m.to_string()).collect(),
    ));

    // Tree.
    console.print(&Rule::new("tree"));
    let mut tree = Tree::new("rs-rich-cli");
    let core = tree.add("crates/rich (core, mirrors rich 15.0.0)");
    core.add("color · style · text · console");
    core.add("box · rule · panel · padding · align");
    core.add("table · tree · wrap · filesize");
    tree.add("crates/rich-ext (our extensions)");
    tree.add("crates/rich-cli (this binary)");
    console.print(&tree);

    // Progress bars at a few completion levels (0 → 100%).
    console.print(&Rule::new("progress bar"));
    for pct in [0.0, 33.0, 66.0, 100.0] {
        console.print(&ProgressBar::new(100.0, pct).width(48));
    }

    // Progress display — description + flexing bar + percentage (static frame).
    console.print(&Rule::new("progress"));
    let mut progress = Progress::new();
    progress.add_task("Downloading", 100.0, 50.0);
    progress.add_task("Processing", 100.0, 100.0);
    progress.add_task("Waiting", 100.0, 0.0);
    console.print(&progress);

    // Progress with custom columns — description + bar + M-of-N counter.
    let mut mofn = Progress::new().columns(vec![
        ProgressColumn::Description,
        ProgressColumn::Bar,
        ProgressColumn::MofN,
    ]);
    mofn.add_task("Files", 8.0, 3.0);
    mofn.add_task("Chunks", 128.0, 128.0);
    console.print(&mofn);

    // Progress with a download column — completed/total in shared byte units.
    let mut download = Progress::new().columns(vec![
        ProgressColumn::Description,
        ProgressColumn::Bar,
        ProgressColumn::Download,
    ]);
    download.add_task("archive.tar", 10_000_000.0, 4_200_000.0);
    console.print(&download);

    // JSON — pretty-printed and highlighted.
    console.print(&Rule::new("json"));
    if let Ok(json) = Json::new(
        r#"{"port": "rich", "version": "15.0.0", "parity": true, "widgets": ["panel", "table", "tree"]}"#,
    ) {
        console.print(&json);
    }

    // Pretty — colorize a Rust value's Debug output (Rust-native rich.pretty).
    console.print(&Rule::new("pretty"));
    let value = vec![("panel", 1u32), ("table", 2), ("tree", 3)];
    console.print(&Pretty::new(&value));

    // Log records — a severity-colored line per record (Rust-native rich.logging).
    console.print(&Rule::new("log"));
    for (level, message) in [
        (LogLevel::Info, "server started on port 8080"),
        (LogLevel::Debug, "cache warm: 128 entries"),
        (LogLevel::Warn, "disk usage at 85%"),
        (LogLevel::Error, "connection reset by peer"),
    ] {
        console.print(
            &LogRender::new(level, message)
                .time("12:00:00")
                .path("main.rs:42"),
        );
    }

    // Traceback — render an error + its source chain (Rust-native rich.traceback).
    console.print(&Rule::new("traceback"));
    let cause = std::io::Error::new(std::io::ErrorKind::NotFound, "no such file: config.toml");
    let err = std::io::Error::other(cause);
    console.print(&Traceback::new(&err));

    // Bar — a filled span within a range (eighth-block resolution).
    console.print(&Rule::new("bar (range)"));
    for (begin, end) in [(0.0, 100.0), (0.0, 62.0), (20.0, 80.0), (55.0, 100.0)] {
        console.print(&Bar::new(100.0, begin, end).width(48));
    }

    // Markdown — headings, inline styles, lists, block quotes, tables, and rules.
    console.print(&Rule::new("markdown"));
    console.print(&Markdown::new(
        "# Heading\n\nA paragraph with **bold**, *italic*, `code`, and a [link](https://example.com).\n\n- bullet item\n- another\n\n1. first\n2. second\n\n> a block quote\n\n| Name | Age |\n| :--- | ---: |\n| Alice | 30 |\n| Bob | 7 |\n\n```rust\nfn main() {\n    println!(\"hi\");\n}\n```\n\n---",
    ));

    // Syntax highlighting (via syntect — functional, not byte-parity with rich).
    console.print(&Rule::new("syntax"));
    console.print(&Syntax::new(
        "fn main() {\n    let msg = \"hello, rich\";\n    println!(\"{msg}\");\n}",
        "rust",
    ));

    // Control codes — cursor/screen sequences (shown escaped, not executed).
    console.print(&Rule::new("control codes"));
    let show_escape = |label: &str, control: &Control| {
        // Escaped so the sequence is visible (and its `[` isn't read as markup).
        let escaped = control
            .as_str()
            .replace('\x1b', "\\x1b")
            .replace('\x07', "\\a")
            .replace('\r', "\\r");
        console.print(&Text::new(format!("  {label:>14}: {escaped}")));
    };
    show_escape("clear screen", &Control::clear());
    show_escape("home", &Control::home());
    show_escape("move (2,-1)", &Control::move_(2, -1));
    show_escape("move_to (3,4)", &Control::move_to(3, 4));
    show_escape("hide cursor", &Control::show_cursor(false));
    show_escape("bell", &Control::bell());
    // LiveRender — the in-place redraw sequence for a 3-line render.
    let live_render = LiveRender::new(text("a\nb\nc"));
    let _ = console.render_to_string(&live_render); // render once to record the shape
    show_escape("live refresh", &live_render.position_cursor());
    // Live — the full control stream for a two-frame in-place update (captured
    // to a buffer so the demo stays static instead of animating).
    let live_console = Console::builder()
        .force_terminal(true)
        .color_system(Some(ColorSystem::Truecolor))
        .width(20)
        .build();
    let mut live = Live::new(text("frame one"), live_console, Vec::<u8>::new());
    live.start();
    live.update(text("frame two"));
    live.stop();
    let stream = String::from_utf8_lossy(live.writer())
        .replace('\x1b', "\\x1b")
        .replace('\r', "\\r")
        .replace('\n', "\\n");
    console.print(&Text::new(format!("  {:>14}: {stream}", "live stream")));

    // ANSI decoder — parse a raw SGR string back into styled Text, then re-render.
    console.print(&Rule::new("ansi decoder"));
    let raw =
        "\x1b[1;31mred bold\x1b[0m \x1b[38;5;214morange\x1b[0m \x1b[3;4mitalic underline\x1b[0m";
    console.print(&Text::new(format!(
        "  input:  {}",
        raw.replace('\x1b', "\\x1b")
    )));
    let mut decoder = rich::AnsiDecoder::new();
    for line in decoder.decode(raw) {
        console.print(&Text::new("  output: ").append_text(&line));
    }

    // Capture / export — record a rendering to a buffer, then strip its styles.
    console.print(&Rule::new("capture · export_text"));
    let plain = console.export_text(|c| {
        c.print(&Panel::new(text("captured panel")).box_set(SQUARE));
    });
    console.print(&Text::new("  export_text (styles stripped):"));
    for line in plain.lines() {
        console.print(&Text::new(format!("    {line}")));
    }
    // export_html — the inline CSS a style compiles to (via `--export-html`).
    let html_rule = Style::parse("bold red")
        .unwrap()
        .get_html_style(&DEFAULT_TERMINAL_THEME);
    console.print(&Text::new(format!(
        "  export_html: [bold red] → <span style=\"{html_rule}\">"
    )));

    // Layout — split a region into ratioed rows/columns; Panel leaves expand
    // to fill their region (rendered here at a fixed size).
    console.print(&Rule::new("layout"));
    let panel_leaf = |title: &str, body: &str| {
        Layout::with_renderable(Box::new(
            Panel::new(text(body))
                .box_set(SQUARE)
                .title(title.to_string()),
        ))
    };
    let mut header = Layout::new();
    header.split_row(vec![
        panel_leaf("left", "pane A"),
        panel_leaf("right", "pane B"),
    ]);
    let mut root = Layout::new();
    root.split_column(vec![
        header,
        Layout::with_renderable(text("footer (fixed size 3)")).size(3),
    ]);
    let grid = Console::builder()
        .force_terminal(true)
        .color_system(Some(ColorSystem::Truecolor))
        .width(48)
        .height(7)
        .build();
    for line in grid.export_text(|c| c.print(&root)).lines() {
        console.print(&Text::new(line));
    }

    // Spinners — a few frames of each built-in (animation needs a Live loop).
    console.print(&Rule::new("spinner (frames)"));
    for name in ["dots", "line", "arrow", "simpleDots"] {
        let spinner = Spinner::new(name);
        let frames: String = (0..6)
            .map(|i| console.render_to_string(&spinner.render(i as f64 * 0.15)))
            .collect::<Vec<_>>()
            .join(" ");
        console.print_str(&format!("  {name:>11}: {frames}"));
    }
    // Status — a spinner + message (green frame; animation needs a Live loop).
    let status = Status::new("Loading…").renderable().render(0.0);
    console.print(&Text::new("       status: ").append_text(&status));

    // CSV rendered as a table (blue border, numeric columns bold-green + right).
    console.print(&Rule::new("csv"));
    let csv = "Product,Qty,Price\nWidget,3,9.99\nGadget,12,19.50\nGizmo,1,4.25";
    if let Some(table) = build_csv_table(csv, Some(','), None, None) {
        console.print(&table);
    }

    // filesize.
    console.print(&Rule::new("filesize"));
    for bytes in [1u64, 999, 1_000, 1_500, 1_000_000, 1_500_000_000] {
        console.print_str(&format!("  {bytes:>13} → {}", filesize::decimal(bytes)));
    }
    console.print(&Rule::line());
}

#[cfg(test)]
mod tests {
    use super::*;
    use rich::ColorSystem;

    #[cfg(feature = "art")]
    #[test]
    fn diff_threshold_uses_the_reports_tie_rounding() {
        // The report prints 0.2 against 0.2, then 0.8 against 0.7.
        assert!(!diff_threshold_exceeded(0.25, 0.24));
        assert!(diff_threshold_exceeded(0.75, 0.74));
        assert!(!diff_threshold_exceeded(0.75, 0.76));
    }

    #[test]
    fn read_csv_rows_handles_quotes_and_delimiters() {
        let comma = Dialect::excel(',');
        // Quoted field containing the delimiter, and `""` escaping.
        let rows = read_csv_rows("a,\"b,c\",d\n\"he said \"\"hi\"\"\",2\n", &comma);
        assert_eq!(
            rows,
            vec![
                vec!["a".to_string(), "b,c".to_string(), "d".to_string()],
                vec!["he said \"hi\"".to_string(), "2".to_string()],
            ]
        );
        // No trailing empty row after a final newline (`\r` is gone by now:
        // the reader applies universal newlines first).
        assert_eq!(read_csv_rows("x\ny\n", &comma), vec![vec!["x"], vec!["y"]]);
        // Tab delimiter.
        assert_eq!(
            read_csv_rows("a\tb", &Dialect::excel('\t')),
            vec![vec!["a", "b"]]
        );
        // A leading UTF-8 BOM is stripped, not glued to the first cell.
        assert_eq!(read_csv_rows("\u{feff}a,b", &comma), vec![vec!["a", "b"]]);
        // A blank line is an EMPTY record, as `csv.reader` reports it — upstream
        // then drops it, where a `[""]` row would have drawn a blank table row.
        assert_eq!(
            read_csv_rows("a,b\n\nc,d\n", &comma),
            vec![vec!["a", "b"], vec![], vec!["c", "d"]]
        );
        // `skipinitialspace` eats the padding after a delimiter, but only there.
        let padded = Dialect {
            skipinitialspace: true,
            ..Dialect::excel(',')
        };
        assert_eq!(
            read_csv_rows("a,  b , c", &padded),
            vec![vec!["a", "b ", "c"]]
        );
    }

    #[test]
    fn the_sniffer_finds_the_delimiter_and_the_header() {
        // Every expectation here was read out of CPython's own `csv.Sniffer`.
        let candidates = [',', '\t', '|', ';'];
        let sniffed =
            |sample: &str| sniff(sample, Some(&candidates)).map(|dialect| dialect.delimiter);
        assert_eq!(
            sniffed("name;age;city\nAlice;30;Paris\nBob;25;Lyon\n"),
            Some(';')
        );
        assert_eq!(sniffed("a|b|c\n1|2|3\n4|5|6\n"), Some('|'));
        assert_eq!(sniffed("a\tb\tc\n1\t2\t3\n4\t5\t6\n"), Some('\t'));
        assert_eq!(sniffed("a, b, c\n1, 2, 3\n4, 5, 6\n"), Some(','));
        // A quoted, multi-line cell: only the quote/delimiter scan can find the
        // comma here, because the line counts are inconsistent.
        assert_eq!(
            sniffed("name,bio\nAlice,\"line one\nline two\"\nBob,short\n"),
            Some(',')
        );
        // Ragged rows and a single column defeat the sniffer, exactly as they do
        // upstream — that is what the excel fallback is for.
        assert_eq!(sniffed("a,b,c\n1,2\n3,4,5,6\n"), None);
        assert_eq!(sniffed("alpha\nbeta\ngamma\n"), None);

        assert_eq!(has_header("name,age\nAlice,30\nBob,25\n"), Some(true));
        // A column mixing an int and a float must stay ONE type. The historical
        // `for thisType in [int, float, complex]` loop reads it as inconsistent
        // and loses the header.
        assert_eq!(has_header("price,note\n10,aa\n9.5,bbb\n"), Some(true));
        assert_eq!(has_header("1,2,3\n4,5,6\n7,8,9\n"), Some(false));
    }

    #[test]
    fn detects_urls() {
        assert!(is_url("http://example.com"));
        assert!(is_url("https://example.com/x"));
        // RFC 3986: the scheme is case-insensitive.
        assert!(is_url("HTTPS://example.com"));
        assert!(is_url("Http://example.com"));
        assert!(!is_url("example.com"));
        assert!(!is_url("./file.md"));
        assert!(!is_url("-"));
        assert!(!is_url("")); // must not panic on a short/empty resource
        assert!(!is_url("ht"));
        assert!(!is_url("ftp://example.com"));
    }

    #[test]
    fn uninformative_extensions_defer_to_content_type() {
        assert!(is_uninformative_ext("txt"));
        assert!(is_uninformative_ext("log"));
        assert!(!is_uninformative_ext("py"));
        assert!(!is_uninformative_ext("rs"));
    }

    #[test]
    fn resource_ext_uses_basename_without_query() {
        assert_eq!(resource_ext("a.md").as_deref(), Some("md"));
        assert_eq!(resource_ext("path/to/b.RS").as_deref(), Some("rs"));
        assert_eq!(
            resource_ext("https://x.com/c.py?raw=1").as_deref(),
            Some("py")
        );
        // Dots in the host must not be mistaken for an extension.
        assert_eq!(resource_ext("https://api.example.com/data"), None);
        assert_eq!(resource_ext("https://x.com/"), None);
        assert_eq!(resource_ext("noext"), None);
    }

    #[test]
    fn content_type_maps_mode_and_lexer() {
        assert_eq!(mime_of("text/html; charset=utf-8"), "text/html");
        assert_eq!(content_type_mode("text/markdown"), Some(Mode::Markdown));
        assert_eq!(
            content_type_mode("application/json; charset=utf-8"),
            Some(Mode::Json)
        );
        assert_eq!(content_type_mode("text/csv"), Some(Mode::Csv));
        assert_eq!(content_type_mode("text/html"), None); // -> syntax, not a mode
        assert_eq!(content_type_lexer("text/html"), Some("html"));
        assert_eq!(content_type_lexer("text/x-python"), Some("python"));
        assert_eq!(content_type_lexer("text/plain"), None);
    }

    #[test]
    fn join_source_handles_string_and_array() {
        use serde_json::json;
        assert_eq!(join_source(&json!("a\nb")), "a\nb");
        // Array elements already carry their trailing newlines; they concat.
        assert_eq!(join_source(&json!(["a\n", "b"])), "a\nb");
        assert_eq!(join_source(&json!(null)), "");
    }

    #[test]
    fn ipynb_extension_auto_detects() {
        assert_eq!(detect_mode(Some("notebook.ipynb")), Mode::Ipynb);
    }

    #[test]
    fn io_label_builds_execution_count() {
        // "In [1]:" — the plain text (styles aside) should read back exactly.
        assert_eq!(
            io_label("In ", Some(1), "green", "#66ff00").plain(),
            "In [1]:"
        );
        assert_eq!(io_label("Out", None, "red", "#ee4b2b").plain(), "Out[ ]:");
    }

    #[test]
    fn parse_padding_unpacks_like_upstream() {
        assert_eq!(parse_padding("2"), Ok((2, 2, 2, 2)));
        assert_eq!(parse_padding("1,2"), Ok((1, 2, 1, 2)));
        assert_eq!(parse_padding("1,2,3,4"), Ok((1, 2, 3, 4)));
        assert_eq!(parse_padding(" 1 , 2 "), Ok((1, 2, 1, 2)));
        assert!(parse_padding("1,2,3").is_err()); // 3 values not allowed
        assert!(parse_padding("x").is_err());
    }

    #[test]
    fn parse_box_maps_names() {
        assert!(matches!(parse_box("rounded"), Ok(Some(_))));
        assert!(matches!(parse_box("HEAVY"), Ok(Some(_))));
        // `none` is upstream's default and means NO panel, not `box.NONE`.
        assert!(matches!(parse_box("none"), Ok(None)));
        assert!(parse_box("bogus").is_err());
    }

    #[test]
    fn parses_pager_flag() {
        let s = |v: &str| v.to_string();
        assert!(parse(&[s("--pager"), s("x")]).unwrap().unwrap().pager);
        assert!(!parse(&[s("x")]).unwrap().unwrap().pager);
    }

    #[test]
    fn parses_export_flags() {
        let s = |v: &str| v.to_string();
        // Both take a PATH, and the resource is a separate positional.
        let cli = parse(&[s("--export-svg"), s("out.svg"), s("x")])
            .unwrap()
            .unwrap();
        assert_eq!(cli.export_svg.as_deref(), Some("out.svg"));
        assert!(cli.export_html.is_none());
        assert_eq!(cli.resource.as_deref(), Some("x"));

        let cli = parse(&[s("-o"), s("out.html"), s("x")]).unwrap().unwrap();
        assert_eq!(cli.export_html.as_deref(), Some("out.html"));

        // Both together is allowed — upstream writes both files.
        let cli = parse(&[
            s("--export-html"),
            s("a.html"),
            s("--export-svg"),
            s("b.svg"),
            s("x"),
        ])
        .unwrap()
        .unwrap();
        assert_eq!(cli.export_html.as_deref(), Some("a.html"));
        assert_eq!(cli.export_svg.as_deref(), Some("b.svg"));

        // A missing PATH is an error rather than swallowing the next argument.
        assert!(parse(&[s("--export-html")]).is_err());
        // The two export formats are mutually exclusive.
    }

    #[test]
    fn is_number_matches_pattern() {
        // Every case checked against Python's own
        // `re.compile(r"\-?[0-9]*?\.?[0-9]*?").fullmatch`. The loose ones are
        // not oversights: that pattern really does accept a lone `-`, a lone
        // `.` and the empty string, and really does reject a padded `" 12 "`.
        for ok in [
            "0", "42", "-7", "3.14", "-0.5", "", "-", ".", "-.", "5.", ".5",
        ] {
            assert!(is_number(ok), "{ok:?} should be numeric");
        }
        for no in [" 12 ", "1.2.3", "1e5", "abc", "5%"] {
            assert!(!is_number(no), "{no:?} should not be numeric");
        }
    }

    #[test]
    fn render_csv_matches_upstream() {
        // Byte-parity with the Table real rich-cli's render_csv builds for this
        // CSV (captured from rich 15.0.0): HEAVY_HEAD box, blue border, the
        // numeric Age column right-justified with bold-green body + header cells.
        let table = build_csv_table(
            "Name,Age,City\nAlice,30,NYC\nBob,25,LA\n",
            Some(','),
            None,
            None,
        )
        .expect("the sniffer reads this one");
        let out = Console::builder()
            .force_terminal(true)
            .color_system(Some(ColorSystem::Truecolor))
            .width(40)
            .no_color(false)
            .build()
            .render_to_string(&table);
        let expected = concat!(
            "\x1b[34m┏━━━━━━━┳━━━━━┳━━━━━━┓\x1b[0m\n",
            "\x1b[34m┃\x1b[0m\x1b[1m \x1b[0m\x1b[1mName \x1b[0m\x1b[1m \x1b[0m\x1b[34m┃\x1b[0m",
            "\x1b[1;32m \x1b[0m\x1b[1;32mAge\x1b[0m\x1b[1;32m \x1b[0m\x1b[34m┃\x1b[0m",
            "\x1b[1m \x1b[0m\x1b[1mCity\x1b[0m\x1b[1m \x1b[0m\x1b[34m┃\x1b[0m\n",
            "\x1b[34m┡━━━━━━━╇━━━━━╇━━━━━━┩\x1b[0m\n",
            "\x1b[34m│\x1b[0m Alice \x1b[34m│\x1b[0m\x1b[1;32m \x1b[0m\x1b[1;32m 30\x1b[0m",
            "\x1b[1;32m \x1b[0m\x1b[34m│\x1b[0m NYC  \x1b[34m│\x1b[0m\n",
            "\x1b[34m│\x1b[0m Bob   \x1b[34m│\x1b[0m\x1b[1;32m \x1b[0m\x1b[1;32m 25\x1b[0m",
            "\x1b[1;32m \x1b[0m\x1b[34m│\x1b[0m LA   \x1b[34m│\x1b[0m\n",
            "\x1b[34m└───────┴─────┴──────┘\x1b[0m",
        );
        assert_eq!(out, expected);
    }
}