//! Session export as Markdown.

use crate::types::{Message, Part, Role, Session};

fn fence(s: &str) -> String {
    // A fence longer than any backtick run inside the content.
    let mut longest = 0;
    let mut run = 0;
    for c in s.chars() {
        if c == '`' {
            run += 1;
            longest = longest.max(run);
        } else {
            run = 0;
        }
    }
    "`".repeat((longest + 1).max(3))
}

fn clip(s: &str, max: usize) -> String {
    if s.len() <= max {
        return s.to_string();
    }
    let mut end = max;
    while !s.is_char_boundary(end) {
        end -= 1;
    }
    format!("{}\n… ({} more bytes)", &s[..end], s.len() - end)
}

fn time(ms: i64) -> String {
    chrono::DateTime::from_timestamp_millis(ms).map(|t| t.format("%Y-%m-%d %H:%M UTC").to_string()).unwrap_or_default()
}

pub fn markdown(s: &Session, messages: &[Message]) -> String {
    let title = if s.title.is_empty() { "Untitled session" } else { s.title.as_str() };
    let mut out = format!(
        "# {title}\n\n- Directory: `{}`\n- Model: `{}`\n- Mode: {}\n- Created: {}\n- Exported from CodeCraft\n\n---\n\n",
        s.cwd,
        s.model,
        s.agent,
        time(s.created_at)
    );
    for m in messages {
        let is_tool_results = m.parts.iter().all(|p| matches!(p, Part::ToolResult { .. }));
        if !is_tool_results {
            let who = match m.role {
                Role::User => "User".to_string(),
                _ => format!("Assistant{}", m.model.as_deref().map(|x| format!(" ({x})")).unwrap_or_default()),
            };
            out.push_str(&format!("## {who} · {}\n\n", time(m.created_at)));
        }
        for p in &m.parts {
            match p {
                Part::Text { text } => out.push_str(&format!("{}\n\n", text.trim())),
                Part::Summary { text, .. } => out.push_str(&format!("<details><summary>Summary of the earlier conversation</summary>\n\n{}\n\n</details>\n\n", text.trim())),
                Part::Reasoning { text, .. } if !text.trim().is_empty() => {
                    out.push_str(&format!("<details><summary>Thinking</summary>\n\n{}\n\n</details>\n\n", text.trim()))
                }
                Part::Reasoning { .. } => {}
                Part::Image { image } => out.push_str(&format!("*[image: {}]*\n\n", image.media_type)),
                Part::ToolCall { name, input, .. } => {
                    let body = match name.as_str() {
                        "bash" => input["command"].as_str().unwrap_or("").to_string(),
                        _ => serde_json::to_string_pretty(input).unwrap_or_default(),
                    };
                    let body = clip(&body, 4000);
                    let f = fence(&body);
                    out.push_str(&format!("**Tool `{name}`**\n\n{f}{}\n{body}\n{f}\n\n", if name == "bash" { "sh" } else { "json" }));
                }
                Part::ToolResult { name, content, is_error, .. } => {
                    let body = clip(content.trim(), 4000);
                    let f = fence(&body);
                    out.push_str(&format!(
                        "<details><summary>{} of <code>{name}</code></summary>\n\n{f}\n{body}\n{f}\n\n</details>\n\n",
                        if *is_error { "Error" } else { "Result" }
                    ));
                }
            }
        }
    }
    out
}