bbs-md/src/renderer.rs

//! Markdown-to-styled-lines renderer for bbs-md.
//!
//! Converts a markdown string into `Vec<Line<'static>>` using pulldown-cmark
//! event processing, CGA-themed styling, syntax-highlighted code blocks, and
//! box-drawing table grids.
//!
//! # Public API
//!
//! - `render_markdown(input: &str, width: u16, vault_path: Option<&Path>) -> (Vec<Line<'static>>, Vec<LinkRecord>, Vec<CopyableBlock>)`

use std::path::Path;
use pulldown_cmark::{
    Alignment, CodeBlockKind, Event, HeadingLevel, LinkType, Options, Parser, Tag, TagEnd,
    TextMergeStream,
};
use ratatui::style::{Color, Modifier, Style};
use ratatui::text::{Line, Span};

// ── LinkRecord ─────────────────────────────────────────────────────────────────

/// Metadata for a single link discovered during rendering.
///
/// Produced by `render_markdown` as a parallel structure alongside `Vec<Line>`.
/// Plan 02 consumes this to wire Tab-cycling navigation and link following.
pub struct LinkRecord {
    /// Index into `Vec<Line>` where this link appears.
    pub line_index: usize,
    /// Character column offset within that line where the link bracket `[` starts.
    /// Uses `chars().count()` for multi-byte Unicode correctness (Pitfall 4).
    pub col_offset: usize,
    /// Display length of the full `[Link Text]` span (including brackets).
    pub span_len: usize,
    /// Raw destination — vault-relative path for inline links, wiki target for wiki-links.
    pub dest: String,
    /// True if this is a `[[wiki-link]]` (needs `vault::resolve_wiki_link` at nav time).
    /// False for inline `[text](path.md)` links.
    pub is_wiki: bool,
}

// ── CopyableBlock ────────────────────────────────────────────────────────────

/// The kind of copyable block discovered during rendering.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum BlockKind {
    Code,
    Table,
    Blockquote,
    Text,
}

/// Metadata for a single copyable block discovered during rendering.
///
/// Produced by `render_markdown` alongside `Vec<Line>` and `Vec<LinkRecord>`.
/// Used to support OSC 52 copy-to-clipboard in copy mode or on right-click.
pub struct CopyableBlock {
    /// Index into `Vec<Line>` where this block begins.
    pub start_line: usize,
    /// Index into `Vec<Line>` where this block ends (inclusive).
    pub end_line: usize,
    /// Raw content suitable for clipboard (plain text).
    pub raw_content: String,
    /// What kind of block this is.
    pub kind: BlockKind,
}

// ── Internal pending link helpers ─────────────────────────────────────────────

/// Captured at `Tag::Link` Start — records link metadata before the text spans are pushed.
struct PendingLink {
    dest: String,
    is_wiki: bool,
    /// Character column offset computed from current_spans at the moment Start fires.
    col_offset: usize,
    /// Style chosen for this link's brackets and text.
    link_style: Style,
}

/// Created at `TagEnd::Link` — fully formed except for `line_index` (known only at flush).
struct PendingLinkRecord {
    dest: String,
    is_wiki: bool,
    col_offset: usize,
    /// Display length including brackets: computed from spans pushed between Start and End.
    span_len: usize,
}

// ── RenderState ───────────────────────────────────────────────────────────────

/// Internal mutable state threaded through the event handler.
struct RenderState {
    /// Accumulated output lines.
    lines: Vec<Line<'static>>,
    /// Spans for the current (in-progress) line.
    current_spans: Vec<Span<'static>>,
    /// Style stack — push on block/inline Start, pop on End.
    style_stack: Vec<Style>,
    /// True while inside a fenced or indented code block.
    in_code_block: bool,
    /// Language token for the current code block (empty = no language).
    code_lang: String,
    /// Accumulated raw text inside a code block.
    code_buf: String,
    /// List nesting: `None` = unordered, `Some(n)` = ordered starting at n.
    list_counters: Vec<Option<u64>>,
    /// Nesting depth of blockquotes (0 = not in blockquote).
    blockquote_depth: u32,
    /// True when we are currently inside at least one blockquote.
    in_blockquote: bool,
    /// True while collecting alt text for an image.
    in_image: bool,
    /// Accumulated image alt text.
    image_alt: String,
    // ── Table state ──────────────────────────────────────────────────────────
    /// True while inside a table element.
    in_table: bool,
    /// Column alignment from the `Table` tag.
    table_alignments: Vec<Alignment>,
    /// All rows collected (rows[0] = header row).
    table_rows: Vec<Vec<String>>,
    /// Text accumulated for the current table cell.
    current_cell: String,
    /// True while inside the `<thead>` section.
    in_table_head: bool,
    // ── Width ────────────────────────────────────────────────────────────────
    /// Terminal width; used for horizontal rules and code block sizing.
    width: u16,
    // ── Link state ───────────────────────────────────────────────────────────
    /// Active link being rendered (set at Tag::Link Start, cleared at TagEnd::Link).
    pending_link: Option<PendingLink>,
    /// Span count at the moment Tag::Link Start fired — used to compute span_len at End.
    link_span_start_count: usize,
    /// Finalized link records awaiting line_index from the next flush_line call.
    pending_link_records: Vec<PendingLinkRecord>,
    /// All fully resolved link records (line_index filled in at flush time).
    link_records: Vec<LinkRecord>,
    /// All copyable block records discovered during rendering.
    copyable_blocks: Vec<CopyableBlock>,
    /// Line index where the current text section began (None = not in a text section).
    text_section_start: Option<usize>,
    /// Accumulated raw text for the current text section.
    text_section_raw: String,
    /// Line index where the outermost blockquote began (None = not in a blockquote block).
    blockquote_start_line: Option<usize>,
    /// Accumulated raw text for the current blockquote.
    blockquote_raw: String,
}

impl RenderState {
    fn new(width: u16) -> Self {
        RenderState {
            lines: Vec::new(),
            current_spans: Vec::new(),
            style_stack: Vec::new(),
            in_code_block: false,
            code_lang: String::new(),
            code_buf: String::new(),
            list_counters: Vec::new(),
            blockquote_depth: 0,
            in_blockquote: false,
            in_image: false,
            image_alt: String::new(),
            in_table: false,
            table_alignments: Vec::new(),
            table_rows: Vec::new(),
            current_cell: String::new(),
            in_table_head: false,
            width,
            pending_link: None,
            link_span_start_count: 0,
            pending_link_records: Vec::new(),
            link_records: Vec::new(),
            copyable_blocks: Vec::new(),
            text_section_start: None,
            text_section_raw: String::new(),
            blockquote_start_line: None,
            blockquote_raw: String::new(),
        }
    }

    // ── Style helpers ─────────────────────────────────────────────────────────

    /// Return the topmost style from the stack, or `Style::default()` if empty.
    fn current_style(&self) -> Style {
        self.style_stack.last().copied().unwrap_or_default()
    }

    /// Push a new style derived from the current top by adding a modifier.
    fn push_modifier(&mut self, modifier: Modifier) {
        let new_style = self.current_style().add_modifier(modifier);
        self.style_stack.push(new_style);
    }

    // ── Line flushing ─────────────────────────────────────────────────────────

    /// Flush `current_spans` into a `Line`, optionally prepending blockquote borders.
    ///
    /// If inside a blockquote, the content spans are colored gray and preceded
    /// by a yellow `│ ` border for each nesting level.
    ///
    /// Also finalizes any `pending_link_records` by setting their `line_index` to the
    /// index of the line being pushed (Pitfall 1: line_index recorded at flush time,
    /// not at TagEnd::Link, because flush can happen from heading/item/paragraph ends).
    fn flush_line(&mut self) {
        let mut spans = std::mem::take(&mut self.current_spans);

        // Capture raw text from current spans for copyable block tracking
        let raw_text: String = spans.iter().map(|s| s.content.as_ref()).collect();
        if self.in_blockquote {
            if !raw_text.is_empty() {
                if !self.blockquote_raw.is_empty() {
                    self.blockquote_raw.push('\n');
                }
                self.blockquote_raw.push_str(&raw_text);
            }
        } else if self.text_section_start.is_some() && !raw_text.is_empty() {
            if !self.text_section_raw.is_empty() {
                self.text_section_raw.push('\n');
            }
            self.text_section_raw.push_str(&raw_text);
        }

        if self.in_blockquote && self.blockquote_depth > 0 {
            // Re-color content spans to Gray
            for span in spans.iter_mut() {
                span.style = span.style.fg(Color::Gray);
            }
            // Prepend the blockquote border(s)
            let border_str = "│ ".repeat(self.blockquote_depth as usize);
            let border_span =
                Span::styled(border_str, Style::default().fg(Color::Yellow));
            let mut prefixed = vec![border_span];
            prefixed.extend(spans);
            spans = prefixed;
        }

        self.lines.push(Line::from(spans));
        let line_index = self.lines.len() - 1;

        // Finalize any pending link records with the just-pushed line index
        let drained: Vec<PendingLinkRecord> = self.pending_link_records.drain(..).collect();
        for record in drained {
            self.link_records.push(LinkRecord {
                line_index,
                col_offset: record.col_offset,
                span_len: record.span_len,
                dest: record.dest,
                is_wiki: record.is_wiki,
            });
        }
    }

    /// Push a blank (empty) line.
    fn push_blank(&mut self) {
        self.lines.push(Line::default());
    }

    // ── Text section helpers ───────────────────────────────────────────────────

    /// Finalize the current text section, pushing a CopyableBlock if it has content.
    fn finalize_text_section(&mut self) {
        if let Some(start) = self.text_section_start.take() {
            let raw = std::mem::take(&mut self.text_section_raw);
            let trimmed = raw.trim();
            if !trimmed.is_empty() {
                let end = self.lines.len().saturating_sub(1);
                self.copyable_blocks.push(CopyableBlock {
                    start_line: start,
                    end_line: end,
                    raw_content: trimmed.to_string(),
                    kind: BlockKind::Text,
                });
            }
        }
    }

    /// Start a text section if none is active and we are not inside a blockquote.
    fn ensure_text_section(&mut self) {
        if self.text_section_start.is_none() && !self.in_blockquote {
            self.text_section_start = Some(self.lines.len());
        }
    }

    // ── Heading handling ──────────────────────────────────────────────────────

    fn start_heading(&mut self, level: HeadingLevel) {
        let style = match level {
            HeadingLevel::H1 => {
                Style::default().fg(Color::LightCyan).add_modifier(Modifier::BOLD)
            }
            HeadingLevel::H2 => {
                Style::default().fg(Color::LightYellow).add_modifier(Modifier::BOLD)
            }
            HeadingLevel::H3 => {
                Style::default().fg(Color::LightGreen).add_modifier(Modifier::BOLD)
            }
            HeadingLevel::H4 => Style::default().fg(Color::Green),
            HeadingLevel::H5 => Style::default().fg(Color::Cyan),
            HeadingLevel::H6 => Style::default().fg(Color::DarkGray),
        };
        self.style_stack.push(style);
    }

    fn end_heading(&mut self, level: HeadingLevel) {
        // Flush the heading text
        self.flush_line();

        // Pop the heading style
        self.style_stack.pop();

        // Emit decorator for H1 and H2
        let w = self.width as usize;
        match level {
            HeadingLevel::H1 => {
                self.lines.push(Line::from(Span::styled(
                    "═".repeat(w),
                    Style::default().fg(Color::LightCyan),
                )));
            }
            HeadingLevel::H2 => {
                self.lines.push(Line::from(Span::styled(
                    "─".repeat(w),
                    Style::default().fg(Color::LightYellow),
                )));
            }
            _ => {}
        }

        // Always add a blank line after any heading
        self.push_blank();
    }

    // ── Code block emitter ────────────────────────────────────────────────────

    /// Flush the accumulated code buffer and emit a bordered, syntax-highlighted
    /// code block into `self.lines`, recording a `CopyableBlock`.
    fn emit_code_block_now(&mut self) {
        let code = std::mem::take(&mut self.code_buf);
        let lang = std::mem::take(&mut self.code_lang);
        let width = self.width;
        let start_line = self.lines.len(); // index of blank line before top border
        emit_code_block(&code, &lang, width, &mut self.lines);
        let end_line = self.lines.len().saturating_sub(1); // index of blank line after bottom border
        self.copyable_blocks.push(CopyableBlock {
            start_line,
            end_line,
            raw_content: code,
            kind: BlockKind::Code,
        });
    }

    // ── Table emitter ─────────────────────────────────────────────────────────

    /// Flush the accumulated table rows and emit a full box-drawing grid table
    /// into `self.lines`, recording a `CopyableBlock`.
    fn emit_table_now(&mut self) {
        let alignments = std::mem::take(&mut self.table_alignments);
        let rows = std::mem::take(&mut self.table_rows);
        let start_line = self.lines.len();
        // Build TSV raw content for clipboard
        let raw_content: String = rows.iter()
            .map(|r| r.join("\t"))
            .collect::<Vec<_>>()
            .join("\n");
        emit_table(&alignments, &rows, &mut self.lines);
        let end_line = self.lines.len().saturating_sub(1);
        self.copyable_blocks.push(CopyableBlock {
            start_line,
            end_line,
            raw_content,
            kind: BlockKind::Table,
        });
    }

    // ── Finish ────────────────────────────────────────────────────────────────

    fn finish(mut self) -> (Vec<Line<'static>>, Vec<LinkRecord>, Vec<CopyableBlock>) {
        // Flush any trailing spans that were not terminated with a paragraph end
        if !self.current_spans.is_empty() {
            self.flush_line();
        }
        // Finalize any pending text section or blockquote
        self.finalize_text_section();
        if let Some(start) = self.blockquote_start_line.take() {
            let raw = std::mem::take(&mut self.blockquote_raw);
            let trimmed = raw.trim();
            if !trimmed.is_empty() {
                let end = self.lines.len().saturating_sub(1);
                self.copyable_blocks.push(CopyableBlock {
                    start_line: start,
                    end_line: end,
                    raw_content: trimmed.to_string(),
                    kind: BlockKind::Blockquote,
                });
            }
        }
        (self.lines, self.link_records, self.copyable_blocks)
    }
}

// ── Event dispatcher ──────────────────────────────────────────────────────────

fn handle_event(state: &mut RenderState, event: Event, vault_path: Option<&Path>) {
    match event {
        // ── Headings ──────────────────────────────────────────────────────────
        Event::Start(Tag::Heading { level, .. }) => {
            state.finalize_text_section();
            state.text_section_start = Some(state.lines.len());
            state.start_heading(level);
        }
        Event::End(TagEnd::Heading(level)) => {
            state.end_heading(level);
        }

        // ── Paragraphs ────────────────────────────────────────────────────────
        Event::Start(Tag::Paragraph) => {
            state.ensure_text_section();
        }
        Event::End(TagEnd::Paragraph) => {
            state.flush_line();
            state.push_blank();
        }

        // ── Inline formatting ─────────────────────────────────────────────────
        Event::Start(Tag::Strong) => {
            state.push_modifier(Modifier::BOLD);
        }
        Event::End(TagEnd::Strong) => {
            state.style_stack.pop();
        }
        Event::Start(Tag::Emphasis) => {
            state.push_modifier(Modifier::ITALIC);
        }
        Event::End(TagEnd::Emphasis) => {
            state.style_stack.pop();
        }

        // ── Inline code ───────────────────────────────────────────────────────
        Event::Code(text) => {
            // Inline code: LightCyan color, no background color available in 16-color
            let span = Span::styled(
                text.to_string(),
                Style::default().fg(Color::LightCyan),
            );
            state.current_spans.push(span);
        }

        // ── Text ──────────────────────────────────────────────────────────────
        Event::Text(text) => {
            if state.in_code_block {
                state.code_buf.push_str(&text);
            } else if state.in_image {
                state.image_alt.push_str(&text);
            } else if state.in_table {
                state.current_cell.push_str(&text);
            } else if let Some(ref pending) = state.pending_link {
                // Inside a link: render text with the link's style
                let link_style = pending.link_style;
                state.current_spans.push(Span::styled(text.to_string(), link_style));
            } else {
                let style = state.current_style();
                state.current_spans.push(Span::styled(text.to_string(), style));
            }
        }

        // ── Code blocks ───────────────────────────────────────────────────────
        Event::Start(Tag::CodeBlock(kind)) => {
            state.finalize_text_section();
            state.code_lang = match kind {
                CodeBlockKind::Fenced(lang) => lang.to_string(),
                CodeBlockKind::Indented => String::new(),
            };
            state.in_code_block = true;
            state.code_buf.clear();
        }
        Event::End(TagEnd::CodeBlock) => {
            state.in_code_block = false;
            state.emit_code_block_now();
        }

        // ── Lists ─────────────────────────────────────────────────────────────
        Event::Start(Tag::List(start)) => {
            state.ensure_text_section();
            state.list_counters.push(start);
        }
        Event::End(TagEnd::List(_)) => {
            state.list_counters.pop();
            // Blank line after top-level list only
            if state.list_counters.is_empty() {
                state.push_blank();
            }
        }
        Event::Start(Tag::Item) => {
            let depth = state.list_counters.len();
            let indent = "  ".repeat(depth.saturating_sub(1));

            let bullet_str = match state.list_counters.last_mut() {
                Some(Some(n)) => {
                    let s = format!("{}{}. ", indent, n);
                    *n += 1;
                    s
                }
                Some(None) => {
                    let bullet = match depth {
                        1 => "• ",
                        2 => "◦ ",
                        _ => "▪ ",
                    };
                    format!("{}{}", indent, bullet)
                }
                None => format!("{}• ", indent),
            };

            state.current_spans.push(Span::styled(
                bullet_str,
                Style::default().fg(Color::Cyan),
            ));
        }
        Event::End(TagEnd::Item) => {
            state.flush_line();
        }

        // ── Blockquotes ───────────────────────────────────────────────────────
        Event::Start(Tag::BlockQuote(_)) => {
            if state.blockquote_depth == 0 {
                state.finalize_text_section();
                state.push_blank();
                state.blockquote_start_line = Some(state.lines.len());
            }
            state.blockquote_depth += 1;
            state.in_blockquote = true;
        }
        Event::End(TagEnd::BlockQuote(_)) => {
            if state.blockquote_depth > 0 {
                state.blockquote_depth -= 1;
            }
            if state.blockquote_depth == 0 {
                state.in_blockquote = false;
                // Finalize blockquote as a copyable block
                if let Some(start) = state.blockquote_start_line.take() {
                    let raw = std::mem::take(&mut state.blockquote_raw);
                    let trimmed = raw.trim();
                    if !trimmed.is_empty() {
                        let end = state.lines.len().saturating_sub(1);
                        state.copyable_blocks.push(CopyableBlock {
                            start_line: start,
                            end_line: end,
                            raw_content: trimmed.to_string(),
                            kind: BlockKind::Blockquote,
                        });
                    }
                }
                state.push_blank();
            }
        }

        // ── Horizontal rules ──────────────────────────────────────────────────
        Event::Rule => {
            state.finalize_text_section();
            let w = state.width as usize;
            state.lines.push(Line::from(Span::styled(
                "─".repeat(w),
                Style::default().fg(Color::DarkGray),
            )));
            state.push_blank();
        }

        // ── Images ────────────────────────────────────────────────────────────
        Event::Start(Tag::Image { .. }) => {
            state.in_image = true;
            state.image_alt.clear();
        }
        Event::End(TagEnd::Image) => {
            let alt = std::mem::take(&mut state.image_alt);
            let placeholder = format!("[IMAGE: {}]", alt);
            state.current_spans.push(Span::styled(
                placeholder,
                Style::default()
                    .fg(Color::DarkGray)
                    .add_modifier(Modifier::DIM),
            ));
            state.in_image = false;
        }

        // ── Links ─────────────────────────────────────────────────────────────
        Event::Start(Tag::Link { link_type, dest_url, .. }) => {
            let is_wiki = matches!(link_type, LinkType::WikiLink { .. });

            // Determine link style: broken wiki-links get Red+CROSSED_OUT,
            // all other links get LightCyan.
            // Per plan: check wiki-link validity at render time using vault_path.
            // Standard links (inline) are always LightCyan — broken state revealed at nav time only.
            let link_style = if is_wiki {
                // Check whether this wiki-link resolves in the vault
                let resolves = vault_path.map(|vp| {
                    crate::vault::resolve_wiki_link(vp, &dest_url).is_some()
                }).unwrap_or(true); // if no vault_path, assume valid (non-breaking)

                if resolves {
                    Style::default().fg(Color::LightCyan)
                } else {
                    Style::default().fg(Color::Red).add_modifier(Modifier::CROSSED_OUT)
                }
            } else if dest_url.starts_with("http://") || dest_url.starts_with("https://") {
                // Remote HTTP/HTTPS links are visually distinct from local links
                Style::default().fg(Color::LightMagenta)
            } else {
                Style::default().fg(Color::LightCyan)
            };

            // Record column offset before pushing any link spans
            let col_offset: usize = state.current_spans.iter()
                .map(|s| s.content.chars().count())
                .sum();

            // Record span count to compute span_len at TagEnd::Link
            state.link_span_start_count = state.current_spans.len();

            // Set pending link state
            state.pending_link = Some(PendingLink {
                dest: dest_url.to_string(),
                is_wiki,
                col_offset,
                link_style,
            });

            // Push opening bracket "[" with the link style
            state.current_spans.push(Span::styled("[".to_string(), link_style));
        }

        Event::End(TagEnd::Link) => {
            if let Some(pending) = state.pending_link.take() {
                // Push closing bracket "]" with the same link style
                state.current_spans.push(Span::styled("]".to_string(), pending.link_style));

                // Compute span_len: total chars in all spans pushed for this link
                // (from link_span_start_count to current end, inclusive of brackets)
                let span_len: usize = state.current_spans[state.link_span_start_count..]
                    .iter()
                    .map(|s| s.content.chars().count())
                    .sum();

                // Enqueue pending link record — line_index will be set at flush_line
                state.pending_link_records.push(PendingLinkRecord {
                    dest: pending.dest,
                    is_wiki: pending.is_wiki,
                    col_offset: pending.col_offset,
                    span_len,
                });
            }
        }

        // ── Tables ────────────────────────────────────────────────────────────
        Event::Start(Tag::Table(alignments)) => {
            state.finalize_text_section();
            state.table_alignments = alignments;
            state.table_rows.clear();
            state.in_table = true;
        }
        Event::End(TagEnd::Table) => {
            state.in_table = false;
            state.emit_table_now();
        }
        Event::Start(Tag::TableHead) => {
            state.in_table_head = true;
            // Start a new row for the header
            state.table_rows.push(Vec::new());
        }
        Event::End(TagEnd::TableHead) => {
            state.in_table_head = false;
        }
        Event::Start(Tag::TableRow) => {
            if !state.in_table_head {
                state.table_rows.push(Vec::new());
            }
        }
        Event::End(TagEnd::TableRow) => {}
        Event::Start(Tag::TableCell) => {
            state.current_cell.clear();
        }
        Event::End(TagEnd::TableCell) => {
            let cell = std::mem::take(&mut state.current_cell);
            if let Some(row) = state.table_rows.last_mut() {
                row.push(cell);
            }
        }

        // ── Breaks ────────────────────────────────────────────────────────────
        Event::SoftBreak => {
            state.current_spans.push(Span::raw(" "));
        }
        Event::HardBreak => {
            state.flush_line();
        }

        // ── Strikethrough (enabled but treated as plain text for now) ─────────
        Event::Start(Tag::Strikethrough) => {
            state.push_modifier(Modifier::CROSSED_OUT);
        }
        Event::End(TagEnd::Strikethrough) => {
            state.style_stack.pop();
        }

        // ── Everything else ────────────────────────────────────────────────────
        _ => {}
    }
}

// ── Code block emitter ────────────────────────────────────────────────────────

/// Emit a fenced code block with rounded box-drawing borders and syntax
/// highlighting via `crate::highlighter::highlight_code()`.
///
/// Layout:
/// ```text
/// ╭─ rust ─────────────────────╮
/// │ let x = 1;                 │
/// ╰────────────────────────────╯
/// ```
fn emit_code_block(
    code_buf: &str,
    lang: &str,
    width: u16,
    lines: &mut Vec<Line<'static>>,
) {
    let highlighted = crate::highlighter::highlight_code(code_buf, lang);

    // Compute box width: at least lang.len() + 6, capped at terminal width
    let max_content_width = highlighted.iter()
        .map(|l| l.spans.iter().map(|s| s.content.chars().count()).sum::<usize>())
        .max()
        .unwrap_or(0);
    let min_width_for_lang = if lang.is_empty() { 4 } else { lang.chars().count() + 6 };
    let box_width = (max_content_width + 4)
        .max(min_width_for_lang)
        .min(width as usize);

    // ── Top border ───────────────────────────────────────────────────────────
    // ╭─ rust ───────╮  or  ╭──────────╮
    let top_line = if lang.is_empty() {
        // No language label
        let fill = "─".repeat(box_width.saturating_sub(2));
        Line::from(vec![
            Span::styled("╭".to_string(), Style::default().fg(Color::DarkGray)),
            Span::styled(fill, Style::default().fg(Color::DarkGray)),
            Span::styled("╮".to_string(), Style::default().fg(Color::DarkGray)),
        ])
    } else {
        // With language label: ╭─ {lang} ─...─╮
        let label = format!("─ {} ", lang);
        let used = label.chars().count() + 2; // ╭ + label + ╮
        let fill_len = box_width.saturating_sub(used);
        let fill = "─".repeat(fill_len);
        Line::from(vec![
            Span::styled("╭".to_string(), Style::default().fg(Color::DarkGray)),
            Span::styled("─ ".to_string(), Style::default().fg(Color::DarkGray)),
            Span::styled(lang.to_string(), Style::default().fg(Color::Yellow)),
            Span::styled(format!(" {}", fill), Style::default().fg(Color::DarkGray)),
            Span::styled("╮".to_string(), Style::default().fg(Color::DarkGray)),
        ])
    };
    lines.push(Line::default()); // blank before
    lines.push(top_line);

    // ── Content lines ─────────────────────────────────────────────────────────
    // │ {highlighted spans} {padding} │
    if highlighted.is_empty() {
        // Empty code block
        let inner_width = box_width.saturating_sub(4); // "│ " + " │"
        let padding = " ".repeat(inner_width);
        lines.push(Line::from(vec![
            Span::styled("│ ".to_string(), Style::default().fg(Color::DarkGray)),
            Span::styled(padding, Style::default().fg(Color::Gray)),
            Span::styled(" │".to_string(), Style::default().fg(Color::DarkGray)),
        ]));
    } else {
        for hl_line in highlighted {
            let content_len: usize = hl_line.spans.iter().map(|s| s.content.chars().count()).sum();
            let inner_width = box_width.saturating_sub(4);
            let pad_len = inner_width.saturating_sub(content_len);
            let padding = " ".repeat(pad_len);

            let mut row_spans = vec![
                Span::styled("│ ".to_string(), Style::default().fg(Color::DarkGray)),
            ];
            for span in hl_line.spans {
                row_spans.push(span);
            }
            row_spans.push(Span::styled(padding, Style::default()));
            row_spans.push(Span::styled(" │".to_string(), Style::default().fg(Color::DarkGray)));
            lines.push(Line::from(row_spans));
        }
    }

    // ── Bottom border ─────────────────────────────────────────────────────────
    let fill = "─".repeat(box_width.saturating_sub(2));
    lines.push(Line::from(vec![
        Span::styled("╰".to_string(), Style::default().fg(Color::DarkGray)),
        Span::styled(fill, Style::default().fg(Color::DarkGray)),
        Span::styled("╯".to_string(), Style::default().fg(Color::DarkGray)),
    ]));
    lines.push(Line::default()); // blank after
}

// ── Table emitter ─────────────────────────────────────────────────────────────

/// Emit a GFM table with full box-drawing grid.
///
/// Layout:
/// ```text
/// ┌──────┬──────┐
/// │ Col1 │ Col2 │
/// ├──────┼──────┤
/// │ data │ data │
/// └──────┴──────┘
/// ```
fn emit_table(
    alignments: &[Alignment],
    rows: &[Vec<String>],
    lines: &mut Vec<Line<'static>>,
) {
    if rows.is_empty() {
        return;
    }

    let n_cols = alignments.len().max(
        rows.iter().map(|r| r.len()).max().unwrap_or(0)
    );
    if n_cols == 0 {
        return;
    }

    // ── Compute column widths ─────────────────────────────────────────────────
    // Minimum 5 chars; each cell gets +2 for surrounding spaces
    let mut col_widths: Vec<usize> = vec![5; n_cols];
    for row in rows {
        for (i, cell) in row.iter().enumerate() {
            if i < n_cols {
                col_widths[i] = col_widths[i].max(cell.chars().count() + 2);
            }
        }
    }

    // ── Border builder ────────────────────────────────────────────────────────
    let build_border = |left: char, mid: char, right: char, fill: char| -> String {
        let mut s = String::new();
        s.push(left);
        for (i, &w) in col_widths.iter().enumerate() {
            s.extend(std::iter::repeat(fill).take(w));
            if i + 1 < n_cols {
                s.push(mid);
            }
        }
        s.push(right);
        s
    };

    let border_style = Style::default().fg(Color::Cyan);

    // ── Top border ────────────────────────────────────────────────────────────
    let top = build_border('┌', '┬', '┐', '─');
    lines.push(Line::from(Span::styled(top, border_style)));

    // ── Header row ────────────────────────────────────────────────────────────
    let header_style = Style::default()
        .fg(Color::LightCyan)
        .add_modifier(Modifier::BOLD);

    emit_table_row(
        &rows[0],
        &col_widths,
        alignments,
        header_style,
        border_style,
        lines,
    );

    // ── Header separator ──────────────────────────────────────────────────────
    let sep = build_border('├', '┼', '┤', '─');
    lines.push(Line::from(Span::styled(sep, border_style)));

    // ── Data rows ─────────────────────────────────────────────────────────────
    let data_style = Style::default();
    for row in rows.iter().skip(1) {
        emit_table_row(row, &col_widths, alignments, data_style, border_style, lines);
    }

    // ── Bottom border ─────────────────────────────────────────────────────────
    let bottom = build_border('└', '┴', '┘', '─');
    lines.push(Line::from(Span::styled(bottom, border_style)));
    lines.push(Line::default()); // spacing after table
}

/// Emit a single table data row (header or body) as a `Line`.
fn emit_table_row(
    cells: &[String],
    col_widths: &[usize],
    alignments: &[Alignment],
    cell_style: Style,
    border_style: Style,
    lines: &mut Vec<Line<'static>>,
) {
    let n_cols = col_widths.len();
    let mut spans: Vec<Span<'static>> = Vec::new();

    for col in 0..n_cols {
        spans.push(Span::styled("│".to_string(), border_style));
        let cell_text = cells.get(col).map(|s| s.as_str()).unwrap_or("");
        let width = col_widths[col];
        let alignment = alignments.get(col).copied().unwrap_or(Alignment::None);

        let padded = pad_cell(cell_text, width, alignment);
        spans.push(Span::styled(padded, cell_style));
    }
    spans.push(Span::styled("│".to_string(), border_style));
    lines.push(Line::from(spans));
}

/// Pad a cell string to `width` according to the column alignment.
///
/// - `Left` / `None`: one leading space, right-pad to width
/// - `Right`: left-pad to width, one trailing space
/// - `Center`: center the text within width
fn pad_cell(text: &str, width: usize, alignment: Alignment) -> String {
    // width includes the surrounding single-space padding on each side
    let content_width = width.saturating_sub(2);
    let text_len = text.chars().count();

    match alignment {
        Alignment::Right => {
            // Right-align: spaces on left, 1 trailing space
            let pad = content_width.saturating_sub(text_len);
            format!("{}{} ", " ".repeat(pad + 1), text)
        }
        Alignment::Center => {
            let pad = content_width.saturating_sub(text_len);
            let left_pad = pad / 2 + 1;
            let right_pad = pad - (pad / 2) + 1;
            format!(
                "{}{}{}",
                " ".repeat(left_pad),
                text,
                " ".repeat(right_pad)
            )
        }
        // Alignment::Left and Alignment::None
        _ => {
            let pad = content_width.saturating_sub(text_len);
            format!(" {}{}", text, " ".repeat(pad + 1))
        }
    }
}

// ── Public API ────────────────────────────────────────────────────────────────

/// Convert a markdown string into styled ratatui lines plus link and copyable block metadata.
///
/// Returns a 3-tuple `(Vec<Line<'static>>, Vec<LinkRecord>, Vec<CopyableBlock>)`:
/// - Lines: styled display content for ratatui `Paragraph`
/// - LinkRecords: parallel metadata for every link found (line_index, col_offset,
///   span_len, dest, is_wiki) — consumed for Tab-cycling navigation
/// - CopyableBlocks: metadata for every copyable block (start_line, end_line,
///   raw_content, kind) — consumed for copy mode and OSC 52 clipboard
///
/// The `vault_path` parameter is used to resolve wiki-links at render time,
/// enabling broken wiki-links to be shown in red/strikethrough inline. Pass
/// `None` when vault_path is unavailable (e.g. during resize before first doc load).
///
/// The `width` parameter controls the width used for:
/// - Horizontal rule `─` characters (full-width)
/// - Code block border sizing
///
/// All output spans are `'static` (owned strings) — no lifetime dependency on
/// the input `&str`. The result can be stored in `App` state and rendered
/// indefinitely via `Paragraph::new(lines).scroll((offset, 0))`.
///
/// # Panics
///
/// Panics if `crate::highlighter::init_highlighter()` has not been called before
/// the first code block is encountered.
pub fn render_markdown(input: &str, width: u16, vault_path: Option<&Path>) -> (Vec<Line<'static>>, Vec<LinkRecord>, Vec<CopyableBlock>) {
    let mut opts = Options::empty();
    opts.insert(Options::ENABLE_TABLES);
    opts.insert(Options::ENABLE_STRIKETHROUGH);
    opts.insert(Options::ENABLE_TASKLISTS);
    opts.insert(Options::ENABLE_GFM);
    opts.insert(Options::ENABLE_WIKILINKS);

    let parser = TextMergeStream::new(Parser::new_ext(input, opts));

    let mut state = RenderState::new(width);
    for event in parser {
        handle_event(&mut state, event, vault_path);
    }
    state.finish()
}