//! `@path` mentions in user prompts: the mentioned files (or folder listings)
//! are attached to the prompt, read with the regular read/list tools.

use crate::app::App;
use crate::tools::{Tool, ToolCtx};
use crate::types::Part;
use serde_json::json;
use std::path::PathBuf;
use std::sync::Arc;
use tokio_util::sync::CancellationToken;

const MAX_MENTIONS: usize = 10;
const MAX_CHARS: usize = 60_000;

/// `@token`s at the start of the text or after whitespace (not e-mail addresses).
pub fn find(text: &str) -> Vec<String> {
    let re = regex::Regex::new(r"(?:^|\s)@([\w./~+\-]+)").unwrap();
    let mut out: Vec<String> = Vec::new();
    for c in re.captures_iter(text) {
        let token = c[1].trim_end_matches(['.', ',', ';', ':', '!', '?', ')']).to_string();
        if !token.is_empty() && !out.contains(&token) {
            out.push(token);
        }
    }
    out
}

/// Parts to append to a user prompt for its mentions.
pub async fn expand(app: &Arc<App>, session_id: &str, text: &str) -> Vec<Part> {
    let tokens = find(text);
    if tokens.is_empty() {
        return vec![];
    }
    let Ok(session) = app.session(session_id) else { return vec![] };
    let cwd = PathBuf::from(&session.cwd);
    let ctx = ToolCtx {
        app: app.clone(),
        session_id: session_id.to_string(),
        call_id: String::new(),
        cwd: cwd.clone(),
        cancel: CancellationToken::new(),
        agent: session.agent.clone(),
        roots: app.user_roots(session.owner_id.as_deref()),
        sandbox: crate::sandbox::spec_for(app, session.owner_id.as_deref()),
        clean_room: session.clean_room(app.config().craft.clean_room),
        owner_id: None,
    };
    let mut parts = Vec::new();
    for token in tokens.into_iter().take(MAX_MENTIONS) {
        let Ok(path) = ctx.resolve_read(&token) else { continue };
        if !path.exists() {
            continue;
        }
        let res = if path.is_dir() {
            crate::tools::fs::List.run(json!({"path": token}), &ctx).await
        } else {
            crate::tools::fs::Read.run(json!({"path": token}), &ctx).await
        };
        let Ok(out) = res else { continue };
        let mut content = out.content;
        if content.len() > MAX_CHARS {
            let mut end = MAX_CHARS;
            while !content.is_char_boundary(end) {
                end -= 1;
            }
            content.truncate(end);
            content.push_str("\n[… truncated – read the rest with the read tool]");
        }
        let kind = if path.is_dir() { "folder" } else { "file" };
        parts.push(Part::Text { text: format!("<mentioned-{kind} path=\"{token}\">\n{content}\n</mentioned-{kind}>") });
        parts.extend(out.images.into_iter().map(|image| Part::Image { image }));
    }
    parts
}

#[cfg(test)]
mod tests {
    #[test]
    fn finds_mentions() {
        assert_eq!(super::find("look at @src/main.rs, and @README.md."), vec!["src/main.rs", "README.md"]);
        assert!(super::find("mail me at a@b.de").is_empty());
        assert_eq!(super::find("@docs/ please"), vec!["docs/"]);
    }
}