bulletty 0.2.1

//! A simple markdown renderer widget for Ratatui.
//! Originally written by joshka
//! https://github.com/joshka/tui-markdown

use std::sync::LazyLock;
use std::vec;

use ansi_to_tui::IntoText;
use itertools::{Itertools, Position};
use pulldown_cmark::{
    BlockQuoteKind, CodeBlockKind, CowStr, Event, HeadingLevel, Options, Parser, Tag, TagEnd,
};
use ratatui::style::{Style, Stylize};
use ratatui::text::{Line, Span, Text};
use syntect::{
    easy::HighlightLines,
    highlighting::ThemeSet,
    parsing::SyntaxSet,
    util::{LinesWithEndings, as_24_bit_terminal_escaped},
};
use tracing::{debug, instrument, warn};

use crate::core::library::settings::theme::Theme;
use crate::ui::tools::styles;

pub fn from_str(input: &str, theme: Option<Theme>) -> Text<'_> {
    let mut options = Options::empty();
    options.insert(Options::ENABLE_STRIKETHROUGH);
    let parser = Parser::new_ext(input, options);
    let mut writer = TextWriter::new(parser, theme);
    writer.run();
    writer.text
}

struct TextWriter<'a, I> {
    /// Iterator supplying events.
    iter: I,

    /// Text to write to.
    text: Text<'a>,

    /// Current style.
    ///
    /// This is a stack of styles, with the top style being the current style.
    inline_styles: Vec<Style>,

    /// Prefix to add to the start of the each line.
    line_prefixes: Vec<Span<'a>>,

    /// Stack of line styles.
    line_styles: Vec<Style>,

    /// Used to highlight code blocks, set when  a codeblock is encountered
    code_highlighter: Option<HighlightLines<'a>>,

    /// Current list index as a stack of indices.
    list_indices: Vec<Option<u64>>,

    /// A link which will be appended to the current line when the link tag is closed.
    link: Option<CowStr<'a>>,

    /// The current image to be closed
    image: Option<CowStr<'a>>,

    /// True when last element requires a new line
    needs_newline: bool,

    /// bulletty Theme
    theme: Option<Theme>,
}

static SYNTAX_SET: LazyLock<SyntaxSet> = LazyLock::new(SyntaxSet::load_defaults_newlines);
static THEME_SET: LazyLock<ThemeSet> = LazyLock::new(ThemeSet::load_defaults);

impl<'a, I> TextWriter<'a, I>
where
    I: Iterator<Item = Event<'a>>,
{
    fn new(iter: I, theme: Option<Theme>) -> Self {
        Self {
            iter,
            text: Text::default(),
            inline_styles: vec![],
            line_styles: vec![],
            line_prefixes: vec![],
            list_indices: vec![],
            needs_newline: false,
            code_highlighter: None,
            link: None,
            image: None,
            theme,
        }
    }

    fn run(&mut self) {
        debug!("Running text writer");
        while let Some(event) = self.iter.next() {
            self.handle_event(event);
        }
    }

    #[instrument(level = "debug", skip(self))]
    fn handle_event(&mut self, event: Event<'a>) {
        match event {
            Event::Start(tag) => self.start_tag(tag),
            Event::End(tag) => self.end_tag(tag),
            Event::Text(text) => self.text(text),
            Event::Code(code) => self.code(code),
            Event::Html(_html) => warn!("Html not yet supported"),
            Event::InlineHtml(_html) => warn!("Inline html not yet supported"),
            Event::FootnoteReference(_) => warn!("Footnote reference not yet supported"),
            Event::SoftBreak => self.soft_break(),
            Event::HardBreak => self.hard_break(),
            Event::Rule => warn!("Rule not yet supported"),
            Event::TaskListMarker(_) => warn!("Task list marker not yet supported"),
            Event::InlineMath(_) => warn!("Inline math not yet supported"),
            Event::DisplayMath(_) => warn!("Display math not yet supported"),
        }
    }

    fn start_tag(&mut self, tag: Tag<'a>) {
        match tag {
            Tag::Paragraph => self.start_paragraph(),
            Tag::Heading { level, .. } => self.start_heading(level),
            Tag::BlockQuote(kind) => self.start_blockquote(kind),
            Tag::CodeBlock(kind) => self.start_codeblock(kind),
            Tag::HtmlBlock => warn!("Html block not yet supported"),
            Tag::List(start_index) => self.start_list(start_index),
            Tag::Item => self.start_item(),
            Tag::FootnoteDefinition(_) => warn!("Footnote definition not yet supported"),
            Tag::Table(_) => warn!("Table not yet supported"),
            Tag::TableHead => warn!("Table head not yet supported"),
            Tag::TableRow => warn!("Table row not yet supported"),
            Tag::TableCell => warn!("Table cell not yet supported"),
            Tag::Emphasis => self.push_inline_style(Style::new().italic()),
            Tag::Strong => self.push_inline_style(Style::new().bold()),
            Tag::Strikethrough => self.push_inline_style(Style::new().crossed_out()),
            Tag::Subscript => warn!("Subscript not yet supported"),
            Tag::Superscript => warn!("Superscript not yet supported"),
            Tag::Link { dest_url, .. } => self.push_link(dest_url),
            Tag::Image {
                link_type,
                dest_url,
                title,
                ..
            } => self.push_image(link_type, dest_url, title),
            Tag::MetadataBlock(_) => warn!("Metadata block not yet supported"),
            Tag::DefinitionList => warn!("Definition list not yet supported"),
            Tag::DefinitionListTitle => warn!("Definition list title not yet supported"),
            Tag::DefinitionListDefinition => warn!("Definition list definition not yet supported"),
        }
    }

    fn end_tag(&mut self, tag: TagEnd) {
        match tag {
            TagEnd::Paragraph => self.end_paragraph(),
            TagEnd::Heading(_) => self.end_heading(),
            TagEnd::BlockQuote(_) => self.end_blockquote(),
            TagEnd::CodeBlock => self.end_codeblock(),
            TagEnd::HtmlBlock => {}
            TagEnd::List(_is_ordered) => self.end_list(),
            TagEnd::Item => {}
            TagEnd::FootnoteDefinition => {}
            TagEnd::Table => {}
            TagEnd::TableHead => {}
            TagEnd::TableRow => {}
            TagEnd::TableCell => {}
            TagEnd::Emphasis => self.pop_inline_style(),
            TagEnd::Strong => self.pop_inline_style(),
            TagEnd::Strikethrough => self.pop_inline_style(),
            TagEnd::Subscript => {}
            TagEnd::Superscript => {}
            TagEnd::Link => self.pop_link(),
            TagEnd::Image => self.pop_image(),
            TagEnd::MetadataBlock(_) => {}
            TagEnd::DefinitionList => {}
            TagEnd::DefinitionListTitle => {}
            TagEnd::DefinitionListDefinition => {}
        }
    }

    fn start_paragraph(&mut self) {
        // Insert an empty line between paragraphs if there is at least one line of text already.
        if self.needs_newline {
            self.push_line(Line::default());
        }

        self.push_line(Line::default().style(styles::p(self.theme.as_ref())));
        self.needs_newline = false;
    }

    fn end_paragraph(&mut self) {
        self.needs_newline = true
    }

    fn start_heading(&mut self, level: HeadingLevel) {
        if self.needs_newline {
            self.push_line(Line::default());
        }

        let style = match level {
            HeadingLevel::H1 => styles::h1(self.theme.as_ref()),
            HeadingLevel::H2 => styles::h2(self.theme.as_ref()),
            HeadingLevel::H3 => styles::h3(self.theme.as_ref()),
            HeadingLevel::H4 => styles::h4(self.theme.as_ref()),
            HeadingLevel::H5 => styles::h5(self.theme.as_ref()),
            HeadingLevel::H6 => styles::h6(self.theme.as_ref()),
        };

        let content = format!("{} ", "#".repeat(level as usize));
        self.push_line(Line::styled(content, style));
        self.needs_newline = false;
    }

    fn end_heading(&mut self) {
        self.needs_newline = true
    }

    fn start_blockquote(&mut self, _kind: Option<BlockQuoteKind>) {
        if self.needs_newline {
            self.push_line(Line::default());
            self.needs_newline = false;
        }
        self.line_prefixes.push(Span::from(">"));
        self.line_styles
            .push(styles::blockquote(self.theme.as_ref()));
    }

    fn end_blockquote(&mut self) {
        self.line_prefixes.pop();
        self.line_styles.pop();
        self.needs_newline = true;
    }

    fn text(&mut self, text: CowStr<'a>) {
        if let Some(highlighter) = &mut self.code_highlighter {
            let text: Text = LinesWithEndings::from(&text)
                .filter_map(|line| highlighter.highlight_line(line, &SYNTAX_SET).ok())
                .filter_map(|part| as_24_bit_terminal_escaped(&part, false).into_text().ok())
                .flatten()
                .collect();

            for line in text.lines {
                self.text.push_line(line);
            }
            self.needs_newline = false;
            return;
        }

        for (position, line) in text.lines().with_position() {
            if self.needs_newline {
                self.push_line(Line::default());
                self.needs_newline = false;
            }
            if matches!(position, Position::Middle | Position::Last) {
                self.push_line(Line::default());
            }

            let style = self.inline_styles.last().copied().unwrap_or_default();

            let span = Span::styled(line.to_owned(), style);

            self.push_span(span);
        }
        self.needs_newline = false;
    }

    fn code(&mut self, code: CowStr<'a>) {
        let span = Span::styled(code, styles::code(self.theme.as_ref()));
        self.push_span(span);
    }

    fn hard_break(&mut self) {
        self.push_line(Line::default());
    }

    fn start_list(&mut self, index: Option<u64>) {
        if self.list_indices.is_empty() && self.needs_newline {
            self.push_line(Line::default());
        }
        self.list_indices.push(index);
        self.inline_styles
            .push(styles::list_item(self.theme.as_ref()));
    }

    fn end_list(&mut self) {
        self.list_indices.pop();
        self.inline_styles.pop();
        self.needs_newline = true;
    }

    fn start_item(&mut self) {
        self.push_line(Line::default());
        let width = self.list_indices.len() * 4 - 3;
        if let Some(last_index) = self.list_indices.last_mut() {
            let span = match last_index {
                None => Span::from(" ".repeat(width - 1) + "\u{00A0}\u{00A0}• "),
                Some(index) => {
                    *index += 1;
                    Span::from(format!("\u{00A0}\u{00A0}{:width$}. ", *index - 1))
                }
            };
            self.push_span(span.style(styles::list_item(self.theme.as_ref())));
        }
        self.needs_newline = false;
    }

    fn soft_break(&mut self) {
        self.push_line(Line::default().style(styles::p(self.theme.as_ref())));
    }

    fn start_codeblock(&mut self, kind: CodeBlockKind<'_>) {
        if !self.text.lines.is_empty() {
            self.push_line(Line::default());
        }
        let lang = match kind {
            CodeBlockKind::Fenced(ref lang) => lang.as_ref(),
            CodeBlockKind::Indented => "",
        };

        self.line_styles.push(styles::code(self.theme.as_ref()));

        self.set_code_highlighter(lang);

        let span = Span::from(format!("```{lang}"));
        self.push_line(span.into());
        self.needs_newline = true;
    }

    fn end_codeblock(&mut self) {
        let span = Span::from("```");
        self.push_line(span.into());
        self.needs_newline = true;

        self.line_styles.pop();

        self.clear_code_highlighter();
    }

    #[instrument(level = "trace", skip(self))]
    fn set_code_highlighter(&mut self, lang: &str) {
        if let Some(syntax) = SYNTAX_SET.find_syntax_by_token(lang) {
            debug!("Starting code block with syntax: {:?}", lang);
            let theme = &THEME_SET.themes["base16-ocean.dark"];
            let highlighter = HighlightLines::new(syntax, theme);
            self.code_highlighter = Some(highlighter);
        } else {
            warn!("Could not find syntax for code block: {:?}", lang);
        }
    }

    #[instrument(level = "trace", skip(self))]
    fn clear_code_highlighter(&mut self) {
        self.code_highlighter = None;
    }

    #[instrument(level = "trace", skip(self))]
    fn push_inline_style(&mut self, style: Style) {
        let current_style = self.inline_styles.last().copied().unwrap_or_default();
        let style = current_style.patch(style);
        self.inline_styles.push(style);
        debug!("Pushed inline style: {:?}", style);
        debug!("Current inline styles: {:?}", self.inline_styles);
    }

    #[instrument(level = "trace", skip(self))]
    fn pop_inline_style(&mut self) {
        self.inline_styles.pop();
    }

    #[instrument(level = "trace", skip(self))]
    fn push_line(&mut self, line: Line<'a>) {
        let style = self.line_styles.last().copied().unwrap_or_default();
        let mut line = line.patch_style(style);

        // Add line prefixes to the start of the line.
        let line_prefixes = self.line_prefixes.iter().cloned().collect_vec();
        let has_prefixes = !line_prefixes.is_empty();
        if has_prefixes {
            line.spans.insert(0, " ".into());
        }
        for prefix in line_prefixes.iter().rev().cloned() {
            line.spans.insert(0, prefix);
        }
        self.text.lines.push(line);
    }

    #[instrument(level = "trace", skip(self))]
    fn push_span(&mut self, span: Span<'a>) {
        if let Some(line) = self.text.lines.last_mut() {
            line.push_span(span);
        } else {
            self.push_line(Line::from(vec![span]));
        }
    }

    /// Store the link to be appended to the link text
    #[instrument(level = "trace", skip(self))]
    fn push_link(&mut self, dest_url: CowStr<'a>) {
        self.link = Some(dest_url);
    }

    /// Append the link to the current line
    #[instrument(level = "trace", skip(self))]
    fn pop_link(&mut self) {
        if let Some(link) = self.link.take() {
            self.push_span(" (".into());
            self.push_span(Span::styled(link, styles::link(self.theme.as_ref())));
            self.push_span(")".into());
        }
    }

    #[instrument(level = "trace", skip(self))]
    fn push_image(
        &mut self,
        link_type: pulldown_cmark::LinkType,
        dest_url: CowStr<'a>,
        title: CowStr<'a>,
    ) {
        self.image = Some(dest_url);
        let text = "[Image: ";
        self.push_line(Line::styled(text, styles::p(self.theme.as_ref())));
    }

    /// Append the end of the image tag
    #[instrument(level = "trace", skip(self))]
    fn pop_image(&mut self) {
        if let Some(image_link) = self.image.take() {
            self.push_span("  -> ".into());
            self.push_span(Span::styled(image_link, styles::link(self.theme.as_ref())));
            self.push_span("]".into());
        }
    }
}

#[cfg(test)]
mod tests {
    use indoc::indoc;
    use pretty_assertions::assert_eq;
    use rstest::{fixture, rstest};
    use tracing::level_filters::LevelFilter;
    use tracing::subscriber::{self, DefaultGuard};
    use tracing_subscriber::fmt::format::FmtSpan;
    use tracing_subscriber::fmt::time::Uptime;

    use super::*;

    #[fixture]
    fn with_tracing() -> DefaultGuard {
        let subscriber = tracing_subscriber::fmt()
            .with_test_writer()
            .with_timer(Uptime::default())
            .with_max_level(LevelFilter::TRACE)
            .with_span_events(FmtSpan::ENTER)
            .finish();
        subscriber::set_default(subscriber)
    }

    #[rstest]
    fn empty(_with_tracing: DefaultGuard) {
        assert_eq!(from_str("", None), Text::default());
    }

    #[rstest]
    fn paragraph_single(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("Hello, world!", None),
            Text::from(Line::from("Hello, world!").style(styles::p(None)))
        );
    }

    #[rstest]
    fn paragraph_soft_break(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                Hello
                World
            "},
                None
            ),
            Text::from_iter([
                Line::from("Hello").style(styles::p(None)),
                Line::from("World").style(styles::p(None)),
            ])
        );
    }

    #[rstest]
    fn paragraph_multiple(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                Paragraph 1
                
                Paragraph 2
            "},
                None
            ),
            Text::from_iter([
                Line::from("Paragraph 1").style(styles::p(None)),
                Line::default(),
                Line::from("Paragraph 2").style(styles::p(None))
            ])
        );
    }

    #[rstest]
    fn headings(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                # Heading 1
                ## Heading 2
                ### Heading 3
                #### Heading 4
                ##### Heading 5
                ###### Heading 6
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter(["# ", "Heading 1"]).style(styles::h1(None)),
                Line::default(),
                Line::from_iter(["## ", "Heading 2"]).style(styles::h2(None)),
                Line::default(),
                Line::from_iter(["### ", "Heading 3"]).style(styles::h3(None)),
                Line::default(),
                Line::from_iter(["#### ", "Heading 4"]).style(styles::h4(None)),
                Line::default(),
                Line::from_iter(["##### ", "Heading 5"]).style(styles::h5(None)),
                Line::default(),
                Line::from_iter(["###### ", "Heading 6"]).style(styles::h6(None)),
            ])
        );
    }

    /// I was having difficulty getting the right number of newlines between paragraphs, so this
    /// test is to help debug and ensure that.
    #[rstest]
    fn blockquote_after_paragraph(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                Hello, world!

                > Blockquote
            "},
                None
            ),
            Text::from_iter([
                Line::from("Hello, world!").style(styles::blockquote(None)),
                Line::default(),
                Line::from_iter([">", " ", "Blockquote"]).style(styles::blockquote(None)),
            ])
        );
    }
    #[rstest]
    fn blockquote_single(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("> Blockquote", None),
            Text::from(Line::from_iter([">", " ", "Blockquote"]).style(styles::blockquote(None)))
        );
    }

    #[rstest]
    fn blockquote_soft_break(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                > Blockquote 1
                > Blockquote 2
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([">", " ", "Blockquote 1"]).style(styles::blockquote(None)),
                Line::from_iter([">", " ", "Blockquote 2"]).style(styles::blockquote(None)),
            ])
        );
    }

    #[rstest]
    fn blockquote_multiple(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                > Blockquote 1
                >
                > Blockquote 2
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([">", " ", "Blockquote 1"]).style(styles::blockquote(None)),
                Line::from_iter([">", " "]).style(styles::blockquote(None)),
                Line::from_iter([">", " ", "Blockquote 2"]).style(styles::blockquote(None)),
            ])
        );
    }

    #[rstest]
    fn blockquote_multiple_with_break(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                > Blockquote 1

                > Blockquote 2
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([">", " ", "Blockquote 1"]).style(styles::blockquote(None)),
                Line::default(),
                Line::from_iter([">", " ", "Blockquote 2"]).style(styles::blockquote(None)),
            ])
        );
    }

    #[rstest]
    fn blockquote_nested(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                > Blockquote 1
                >> Nested Blockquote
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([">", " ", "Blockquote 1"]).style(styles::blockquote(None)),
                Line::from_iter([">", " "]).style(styles::blockquote(None)),
                Line::from_iter([">", ">", " ", "Nested Blockquote"])
                    .style(styles::blockquote(None)),
            ])
        );
    }

    #[rstest]
    fn list_single(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                - List item 1
            "},
                None
            ),
            Text::from(Line::from_iter([
                Span::from("\u{a0}\u{a0}• ").style(styles::list_item(None)),
                Span::from("List item 1").style(styles::list_item(None))
            ]))
        );
    }

    #[rstest]
    fn list_multiple(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                - List item 1
                - List item 2
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([
                    Span::from("\u{a0}\u{a0}• ").style(styles::list_item(None)),
                    Span::from("List item 1").style(styles::list_item(None))
                ]),
                Line::from_iter([
                    Span::from("\u{a0}\u{a0}• ").style(styles::list_item(None)),
                    Span::from("List item 2").style(styles::list_item(None))
                ]),
            ])
        );
    }

    #[rstest]
    fn list_ordered(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                1. List item 1
                2. List item 2
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([
                    Span::from("\u{a0}\u{a0}1. ").style(styles::list_item(None)),
                    Span::from("List item 1").style(styles::list_item(None))
                ]),
                Line::from_iter([
                    Span::from("\u{a0}\u{a0}2. ").style(styles::list_item(None)),
                    Span::from("List item 2").style(styles::list_item(None))
                ]),
            ])
        );
    }

    #[rstest]
    fn list_nested(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str(
                indoc! {"
                - List item 1
                  - Nested list item 1
            "},
                None
            ),
            Text::from_iter([
                Line::from_iter([
                    Span::from("\u{a0}\u{a0}• ").style(styles::list_item(None)),
                    Span::from("List item 1").style(styles::list_item(None))
                ]),
                Line::from_iter([
                    Span::from("    \u{a0}\u{a0}• ").style(styles::list_item(None)),
                    Span::from("Nested list item 1").style(styles::list_item(None))
                ]),
            ])
        );
    }

    #[rstest]
    fn strong(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("**Strong**", None),
            Text::from(Line::from("Strong".bold()).style(styles::p(None)))
        );
    }

    #[rstest]
    fn emphasis(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("*Emphasis*", None),
            Text::from(Line::from("Emphasis".italic()).style(styles::p(None)))
        );
    }

    #[rstest]
    fn strikethrough(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("~~Strikethrough~~", None),
            Text::from(Line::from("Strikethrough".crossed_out()).style(styles::p(None)))
        );
    }

    #[rstest]
    fn strong_emphasis(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("**Strong *emphasis***", None),
            Text::from(
                Line::from_iter(["Strong ".bold(), "emphasis".bold().italic()])
                    .style(styles::p(None))
            )
        );
    }

    #[rstest]
    fn link(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("[Link](https://example.com)", None),
            Text::from(
                Line::from_iter([
                    Span::from("Link"),
                    Span::from(" ("),
                    Span::from("https://example.com")
                        .style(styles::p(None))
                        .underlined(),
                    Span::from(")")
                ])
                .style(styles::p(None))
            )
        );
    }

    #[rstest]
    fn image(_with_tracing: DefaultGuard) {
        assert_eq!(
            from_str("![TestImage](/test.html)", None),
            Text::from_iter([
                Line::default().style(styles::p(None)),
                Line::from_iter([
                    Span::from("[Image: "),
                    Span::from("TestImage"),
                    Span::from("  -> "),
                    Span::from("/test.html").style(styles::p(None)).underlined(),
                    Span::from("]"),
                ])
                .style(styles::p(None)),
            ])
        );
    }
}