//! Markdown-to-styled-spans rendering for the chat transcript.
//!
//! Flow: `render_markdown` walks a `pulldown_cmark` event stream and
//! translates each markdown construct into styled `ratatui::text::Span`s,
//! then re-wraps the flat span list to a target column width.
//!
//! Design: code blocks get a dark background with a labeled top bar,
//! headings are bold with distinct colors, blockquotes get a vertical
//! accent bar prefix, and inline code is highlighted with a background.
//! Deliberately adds no leading indentation of its own for paragraphs,
//! headings, or list bullets — the caller (`chat.rs`) owns column
//! alignment via its `PREFIX_WIDTH` scheme, so any indent added here
//! would only apply to a construct's first rendered line and throw
//! wrapped continuation lines out of alignment with it. Code-block lines
//! are the exception: every line gets its `"  "` prefix independently
//! and consistently, so there's no first-line-only misalignment there.

use ratatui::style::{Modifier, Style};
use ratatui::text::Span;
use super::theme::Theme;

/// Render a markdown string into styled terminal spans, word-wrapped to `width`.
///
/// Flow: `pulldown_cmark` parses `text` into an event stream → each
/// Start/End/Text/Code/Break event is translated into styled `Span`s →
/// if `width > 0`, a second pass wraps long lines.
///
/// Return: a flat vec of styled spans; `chat::split_spans_into_lines`
/// turns it back into `Line`s for the Paragraph widget.
#[allow(clippy::too_many_lines)]
pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
    let mut spans = Vec::new();
    let parser = pulldown_cmark::Parser::new(text);
    let mut in_code_block = false;
    let mut in_heading = false;
    let mut heading_level = 0;

    for event in parser {
        match event {
            pulldown_cmark::Event::Start(tag) => {
                match tag {
                    pulldown_cmark::Tag::CodeBlock(_) => {
                        in_code_block = true;
                        // Code block top bar
                        spans.push(Span::styled(
                            "\n",
                            Style::default(),
                        ));
                        spans.push(Span::styled(
                            "  ┌─ code ",
                            Style::default().fg(Theme::TEXT_MUTED).bg(Theme::CODE_BG),
                        ));
                        spans.push(Span::styled(
                            "\n",
                            Style::default(),
                        ));
                    }
                    pulldown_cmark::Tag::Heading { level, .. } => {
                        in_heading = true;
                        heading_level = match level {
                            pulldown_cmark::HeadingLevel::H1 => 1,
                            pulldown_cmark::HeadingLevel::H2 => 2,
                            pulldown_cmark::HeadingLevel::H3 => 3,
                            _ => 4,
                        };
                        // No prefix, we'll handle in the text events
                    }
                    pulldown_cmark::Tag::Item => {
                        // List item bullet
                        spans.push(Span::styled(
                            "• ",
                            Style::default().fg(Theme::PRIMARY),
                        ));
                    }
                    pulldown_cmark::Tag::Link { dest_url, .. } => {
                        spans.push(Span::styled(
                            "[",
                            Style::default().fg(Theme::INFO),
                        ));
                        // We push the URL as a tooltip-like suffix
                        // After the link text ends, we'll add the URL
                        spans.push(Span::styled(
                            format!("]({dest_url})"),
                            Style::default().fg(Theme::TEXT_MUTED).add_modifier(Modifier::ITALIC),
                        ));
                    }
                    pulldown_cmark::Tag::BlockQuote(_) => {
                        spans.push(Span::styled(
                            "▎",
                            Style::default().fg(Theme::BLOCKQUOTE_BAR),
                        ));
                    }
                    _ => {}
                }
            }
            pulldown_cmark::Event::End(tag) => {
                match tag {
                    pulldown_cmark::TagEnd::CodeBlock => {
                        in_code_block = false;
                        // Code block bottom bar
                        spans.push(Span::styled(
                            "\n  └─\n",
                            Style::default().fg(Theme::TEXT_MUTED).bg(Theme::CODE_BG),
                        ));
                    }
                    pulldown_cmark::TagEnd::Heading(_) => {
                        in_heading = false;
                        heading_level = 0;
                        spans.push(Span::raw("\n"));
                    }
                    pulldown_cmark::TagEnd::Paragraph => {
                        spans.push(Span::raw("\n\n"));
                    }
                    pulldown_cmark::TagEnd::Item | pulldown_cmark::TagEnd::BlockQuote(_) => {
                        spans.push(Span::raw("\n"));
                    }
                    _ => {}
                }
            }
            pulldown_cmark::Event::Text(text) => {
                let s = text.to_string();
                if in_code_block {
                    spans.push(Span::styled(
                        format!("  {s}"),
                        Style::default().fg(Theme::ACCENT_TEAL).bg(Theme::CODE_BG),
                    ));
                } else if in_heading {
                    let color = match heading_level {
                        1 => Theme::PRIMARY,
                        2 => Theme::INFO,
                        3 => Theme::ACCENT_PURPLE,
                        _ => Theme::TEXT,
                    };
                    spans.push(Span::styled(
                        s,
                        Style::default().fg(color).add_modifier(Modifier::BOLD),
                    ));
                } else {
                    spans.push(Span::raw(s));
                }
            }
            pulldown_cmark::Event::Code(text) => {
                // Inline code with background
                spans.push(Span::styled(
                    format!(" {text} "),
                    Style::default()
                        .fg(Theme::ACCENT_TEAL)
                        .bg(Theme::CODE_BAR)
                        .add_modifier(Modifier::BOLD),
                ));
            }
            pulldown_cmark::Event::SoftBreak => {
                spans.push(Span::raw(" "));
            }
            pulldown_cmark::Event::HardBreak => {
                spans.push(Span::raw("\n"));
            }
            _ => {}
        }
    }

    if width > 0 {
        let mut spans_out = Vec::new();
        let mut line_len = 0;
        let effective_width = (width as usize).saturating_sub(2); // leave margin

        for span in &spans {
            let style = span.style;
            let s = span.content.clone();
            let text_str = s.as_ref();
            let remaining = text_str.len();

            if line_len + remaining > effective_width && line_len > 0 {
                spans_out.push(Span::raw("\n"));
                line_len = 0;
            }

            spans_out.push(Span::styled(text_str.to_string(), style));

            if text_str.contains('\n') {
                line_len = text_str.split('\n').next_back().unwrap_or("").len();
            } else {
                line_len += remaining;
            }
        }
        spans = spans_out;
    }

    spans
}