shoin 0.2.2

//! Markdown to plain text.
//!
//! Not a renderer — a *stripper*. The job is to leave a file someone can read
//! in `less` or paste into an email, so every marker that exists to be parsed
//! rather than read comes out, and nothing that carries meaning does.
//!
//! Where a marker carries meaning, it is replaced rather than removed: a list
//! stays a list, a quote stays marked as quoted, and a heading keeps its rank
//! by being underlined the way plain-text documents have always done it.

use crate::config::schema::MarkdownConfig;
use crate::render::markdown::block::{classify, BlockKind, Carry, Marker};
use crate::render::markdown::inline;

/// Convert a Markdown document to plain text.
///
/// `justify` stretches every wrapped row of a paragraph but its last to fill
/// `measure` exactly — the same math (`render::align::justify_gaps`) and the
/// same word-wrap (`render::layout::wrap_line`) the live editor's own
/// `:align justified` draws with, reused here because exported text has no
/// terminal to render into. Left `false` (the default), a paragraph is
/// written exactly as it always was: one output line per source line,
/// unwrapped — Shoin stores a paragraph as one logical line and only wraps it
/// for display, so that is already the full text. A heading, quote, list item,
/// or table row is never justified; stretching a quote's `> ` prefix or a
/// table's `|` columns would break what they are.
pub fn render(text: &str, measure: u16, justify: bool) -> String {
    let md = MarkdownConfig::default();
    let mut out: Vec<String> = Vec::new();
    let mut carry = Carry::None;
    let mut in_fence = false;

    for (i, line) in text.lines().enumerate() {
        let (kind, next) = classify(line, &carry, i == 0);
        carry = next;

        match &kind {
            // The fence delimiters go; the code between them is indented, which
            // is how plain text has always marked a block as verbatim.
            BlockKind::FenceOpen(_) => {
                in_fence = true;
                continue;
            }
            BlockKind::FenceClose => {
                in_fence = false;
                continue;
            }
            BlockKind::FenceBody { .. } => {
                out.push(format!("    {line}"));
                continue;
            }
            // Front matter is metadata for tools, not text for readers.
            BlockKind::FrontMatter => continue,
            _ => {}
        }
        if in_fence {
            out.push(format!("    {line}"));
            continue;
        }

        match &kind {
            BlockKind::Heading(level) => {
                let title = strip_inline(line.trim_start().trim_start_matches('#').trim(), &md);
                out.push(title.clone());
                // Underline the top two ranks, the convention `setext` headings
                // and every README have used forever. Deeper ranks would need
                // a third rule nobody recognises, so they stand on their own.
                let rule = match level {
                    1 => Some('='),
                    2 => Some('-'),
                    _ => None,
                };
                if let Some(c) = rule {
                    out.push(c.to_string().repeat(title.chars().count().max(1)));
                }
            }
            BlockKind::Rule => out.push("-".repeat(40)),
            BlockKind::Quote(depth) => {
                let body = line.trim_start().trim_start_matches(['>', ' ']);
                let prefix = "> ".repeat((*depth as usize).max(1));
                out.push(format!("{prefix}{}", strip_inline(body, &md)));
            }
            BlockKind::ListItem { marker, checked, depth } => {
                let indent = " ".repeat(*depth as usize);
                let body = list_body(line);
                let bullet = match (marker, checked) {
                    // A checkbox has to survive: unticked and ticked are the
                    // whole point of the line.
                    (_, Some(true)) => "[x] ".to_string(),
                    (_, Some(false)) => "[ ] ".to_string(),
                    (Marker::Ordered, None) => format!("{} ", ordinal(line)),
                    (_, None) => "- ".to_string(),
                };
                out.push(format!("{indent}{bullet}{}", strip_inline(body, &md)));
            }
            BlockKind::Paragraph if justify => {
                push_justified(&mut out, &strip_inline(line, &md), measure)
            }
            _ => out.push(strip_inline(line, &md)),
        }
    }

    let mut joined = out.join("\n");
    if !joined.ends_with('\n') {
        joined.push('\n');
    }
    joined
}

/// The text of a list item, past its marker and any checkbox.
fn list_body(line: &str) -> &str {
    let t = line.trim_start();
    let past_marker = match t.find(' ') {
        Some(i) => &t[i + 1..],
        None => "",
    };
    let t = past_marker.trim_start();
    if (t.starts_with("[ ]") || t.starts_with("[x]") || t.starts_with("[X]")) && t.len() >= 3 {
        t[3..].trim_start()
    } else {
        t
    }
}

/// `12.` from `  12. text`.
fn ordinal(line: &str) -> String {
    let t = line.trim_start();
    let digits: String = t.chars().take_while(|c| c.is_ascii_digit()).collect();
    let delim = t.chars().nth(digits.len()).unwrap_or('.');
    format!("{digits}{delim}")
}

/// Word-wrap `body` to `measure` and stretch every row but the last to fill it
/// exactly, pushing each as its own output line.
fn push_justified(out: &mut Vec<String>, body: &str, measure: u16) {
    let chars: Vec<char> = body.chars().collect();
    let ranges = crate::render::layout::wrap_line(body, measure);
    let last = ranges.len() - 1;
    for (i, (start, end)) in ranges.into_iter().enumerate() {
        let row: String = chars[start..end].iter().collect();
        if i == last {
            out.push(row.trim_end().to_string());
        } else {
            let gaps = crate::render::align::justify_gaps(&row, measure);
            out.push(stretch(&row, &gaps));
        }
    }
}

/// Insert the extra spaces `align::justify_gaps` computed at each gap.
fn stretch(row: &str, gaps: &[(usize, u16)]) -> String {
    let trimmed = row.trim_end();
    if gaps.is_empty() {
        return trimmed.to_string();
    }
    let mut out = String::new();
    for (i, ch) in trimmed.chars().enumerate() {
        out.push(ch);
        if let Some(&(_, extra)) = gaps.iter().find(|g| g.0 == i) {
            out.push_str(&" ".repeat(extra as usize));
        }
    }
    out
}

/// Drop inline markers, keeping what they wrapped.
///
/// A LINK keeps its target in parentheses: the whole reason to write a link is
/// the address, and a plain-text reader has no way to follow one that has been
/// thrown away.
fn strip_inline(line: &str, md: &MarkdownConfig) -> String {
    let chars: Vec<char> = line.chars().collect();
    let spans = inline::scan(line, md);
    if spans.is_empty() {
        return line.to_string();
    }
    let mut out = String::new();
    let mut i = 0usize;
    for sp in &spans {
        if sp.outer.start < i {
            continue;
        }
        out.extend(&chars[i..sp.outer.start]);
        let inner: String = chars[sp.inner.clone()].iter().collect();
        match sp.kind {
            inline::Inline::Link => {
                let whole: String = chars[sp.outer.clone()].iter().collect();
                match url_of(&whole) {
                    Some(url) if url != inner => out.push_str(&format!("{inner} ({url})")),
                    _ => out.push_str(&inner),
                }
            }
            inline::Inline::Image => out.push_str(&format!("[image: {inner}]")),
            _ => out.push_str(&inner),
        }
        i = sp.outer.end;
    }
    out.extend(&chars[i.min(chars.len())..]);
    out
}

/// The `url` from `[text](url)`.
fn url_of(whole: &str) -> Option<&str> {
    let open = whole.rfind("](")?;
    let close = whole.rfind(')')?;
    (close > open + 2).then(|| whole[open + 2..close].trim())
}

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

    #[test]
    fn headings_keep_their_rank_by_being_underlined() {
        let got = render("# Title\n\n## Section\n\n### Deeper\n", 72, false);
        assert!(got.contains("Title\n====="), "an H1 is ruled with =");
        assert!(got.contains("Section\n-------"), "an H2 with -");
        assert!(got.contains("Deeper"), "deeper ranks stand alone");
        assert!(!got.contains("###"));
    }

    #[test]
    fn inline_markers_go_and_their_text_stays() {
        let got = render("a **bold** and *italic* and `code` and ==hi== here\n", 72, false);
        assert_eq!(got.trim(), "a bold and italic and code and hi here");
    }

    /// A link's address is the reason it was written; plain text has no other
    /// way to carry it.
    #[test]
    fn a_link_keeps_its_address() {
        let got = render("see [the docs](https://example.com/x) now\n", 72, false);
        assert_eq!(got.trim(), "see the docs (https://example.com/x) now");
        // …unless the text already is the address.
        let got = render("[https://example.com](https://example.com)\n", 72, false);
        assert_eq!(got.trim(), "https://example.com");
    }

    #[test]
    fn lists_stay_lists_and_checkboxes_survive() {
        let got = render("- one\n- two\n\n1. first\n2. second\n\n- [ ] todo\n- [x] done\n", 72, false);
        assert!(got.contains("- one"));
        assert!(got.contains("1. first"));
        assert!(got.contains("2. second"));
        assert!(got.contains("[ ] todo"), "an unticked box is the point of the line");
        assert!(got.contains("[x] done"));
    }

    #[test]
    fn quotes_keep_their_mark_and_code_is_indented() {
        let got = render("> quoted words\n\n```rust\nlet x = 1;\n```\n", 72, false);
        assert!(got.contains("> quoted words"));
        assert!(got.contains("    let x = 1;"), "verbatim text is indented");
        assert!(!got.contains("```"), "the fence itself goes");
        assert!(!got.contains("rust"), "…and so does its info string");
    }

    /// A `#` inside a fence is code, not a heading, and must not be underlined.
    #[test]
    fn a_hash_inside_a_fence_is_left_alone() {
        let got = render("```sh\n# a comment\n```\n", 72, false);
        assert!(got.contains("    # a comment"));
        assert!(!got.contains("====="));
    }

    #[test]
    fn front_matter_is_metadata_and_goes() {
        let got = render("---\ntitle: x\n---\nbody\n", 72, false);
        assert!(got.contains("body"));
        assert!(!got.contains("title: x"));
    }

    /// `justify: true` wraps a paragraph to `measure` and stretches every row
    /// but its last to fill it exactly — the same values `render::frame`'s
    /// own `justified_stretches_every_row_but_the_last` test draws on screen,
    /// since this reuses the very same `wrap_line`/`justify_gaps` math.
    #[test]
    fn justify_wraps_and_stretches_a_paragraph_but_its_last_row() {
        let got = render("aaa bbb ccc ddd\n", 10, true);
        let lines: Vec<&str> = got.lines().collect();
        assert_eq!(lines, vec!["aaa    bbb", "ccc ddd"], "{got:?}");
    }

    /// A paragraph that never wraps has no "last row" distinct from its only
    /// row, so it is left exactly as `justify: false` would write it.
    #[test]
    fn justify_leaves_an_unwrapped_paragraph_ragged() {
        let got = render("aaa bbb\n", 20, true);
        assert_eq!(got.trim_end(), "aaa bbb");
    }

    /// `justify` never touches a heading, quote, list item or table row: a
    /// quote's `> ` prefix and a table's `|` columns are the author's own
    /// layout, and wrapping them the way a paragraph wraps would break it.
    #[test]
    fn justify_leaves_headings_quotes_lists_and_tables_alone() {
        let got = render(
            "# A heading much longer than the measure itself\n\n\
             > a quoted line that is also much longer than the measure\n\n\
             - a list item that likewise runs well past the measure\n\n\
             | a | b |\n|---|---|\n| longer than the measure | cell |\n",
            10,
            true,
        );
        assert!(got.contains("A heading much longer than the measure itself"));
        assert!(got.contains("> a quoted line that is also much longer than the measure"));
        assert!(got.contains("- a list item that likewise runs well past the measure"));
        assert!(got.contains("| longer than the measure | cell |"));
    }
}