//! Local web dashboard (issue #54): a read-only HTTP server bound to
//! 127.0.0.1, serving the embedded frontend and a JSON API that mirrors
//! the CLI's stable `--json` contracts (same serde structs).
//!
//! Security model: localhost bind only, GET-only routes, no mutation
//! endpoints. Remote access with a token is issue #80 (phase 3).
//!
//! The frontend is a single self-contained HTML file embedded at compile
//! time (`include_str!`): no external assets, no CDN, works offline.

use crate::app::App;
use anyhow::{Context, Result};
use serde::Serialize;
use tiny_http::{Header, Method, Response, Server, StatusCode};

/// Default listening port (overridable with `am web --port`).
pub const DEFAULT_PORT: u16 = 7878;

/// The embedded single-file frontend (HTML + CSS + JS, dark cockpit).
const INDEX_HTML: &str = include_str!("frontend/index.html");

/// One HTTP exchange result, decoupled from tiny_http so the routing
/// logic stays a pure function (unit-testable without sockets).
pub struct HttpResult {
    pub status: u16,
    pub content_type: &'static str,
    pub body: Vec<u8>,
}

impl HttpResult {
    fn json<T: Serialize>(value: &T) -> Self {
        let body = serde_json::to_vec(value)
            .unwrap_or_else(|_| b"{\"error\":\"serialization failed\"}".to_vec());
        Self {
            status: 200,
            content_type: "application/json; charset=utf-8",
            body,
        }
    }

    /// Serialize a `Result`: Ok → 200 JSON, Err → 500 JSON with the error.
    fn api<T: Serialize>(result: Result<T>) -> Self {
        match result {
            Ok(v) => Self::json(&v),
            Err(e) => Self {
                status: 500,
                content_type: "application/json; charset=utf-8",
                body: serde_json::json!({ "error": format!("{e:#}") })
                    .to_string()
                    .into_bytes(),
            },
        }
    }

    fn text(status: u16, content_type: &'static str, body: String) -> Self {
        Self {
            status,
            content_type,
            body: body.into_bytes(),
        }
    }
}

/// Route one request. Pure function: the only I/O is the app's own data
/// files (journal, sessions, state) — never writes anything.
pub fn handle(app: &App, method: &Method, target: &str) -> HttpResult {
    if *method != Method::Get {
        return HttpResult::text(
            405,
            "text/plain; charset=utf-8",
            "method not allowed — this API is read-only".to_string(),
        );
    }
    let (path, params) = split_query(target);
    match path {
        "/" | "/index.html" => index_page(app),
        "/api/health" => HttpResult::json(&serde_json::json!({
            "status": "ok",
            "version": env!("CARGO_PKG_VERSION"),
        })),
        // Same shape as `am dashboard --json`.
        "/api/overview" => HttpResult::json(&crate::dashboard::collect(app)),
        // Same shape as `am stats --json` (optional ?agent=&period=).
        "/api/stats" => HttpResult::api(crate::commands::stats_cmd::aggregate(
            app,
            query_get(&params, "agent").as_deref(),
            query_get(&params, "period").as_deref(),
        )),
        // Same shape as `am sessions --json` (optional ?agent=&project=&status=).
        "/api/sessions" => HttpResult::api(crate::commands::sessions_cmd::list_rows(
            app,
            query_get(&params, "agent").as_deref(),
            query_get(&params, "project").as_deref(),
            query_get(&params, "status").as_deref(),
        )),
        // Same shape as `am log --json` (optional ?agent=&kind=&since=&limit=).
        "/api/events" => {
            let limit = query_get(&params, "limit")
                .and_then(|v| v.parse::<usize>().ok())
                .unwrap_or(200)
                .min(5000);
            HttpResult::api(crate::commands::log_cmd::rows(
                app,
                query_get(&params, "agent").as_deref(),
                query_get(&params, "kind").as_deref(),
                query_get(&params, "since").as_deref(),
                limit,
            ))
        }
        // Same shape as `am projects --json`.
        "/api/projects" => HttpResult::json(&crate::projects::aggregate(app)),
        _ => HttpResult::text(
            404,
            "text/plain; charset=utf-8",
            format!("not found: {path}"),
        ),
    }
}

/// The embedded page, with every `{{label}}` token replaced by the
/// localized label (`tr_in`), and the status-label bundle injected for
/// the client-side rendering.
fn index_page(app: &App) -> HttpResult {
    let lang = app.lang();
    // The status-label bundle first: it contains raw JSON (quotes, braces)
    // that the {{...}} loop below must not touch.
    let bundle = serde_json::json!({
        "running": crate::i18n::tr_in(lang, "En cours"),
        "stopped": crate::i18n::tr_in(lang, "Terminée"),
        "failed": crate::i18n::tr_in(lang, "Échec"),
        "interrupted": crate::i18n::tr_in(lang, "Interrompue"),
    })
    .to_string();
    let mut html = INDEX_HTML.replace("{{i18n_bundle}}", &bundle);
    // Then every {{label}} token: replaced by the localized label (the
    // French text is both the key and the fallback, so nothing survives).
    while let Some(start) = html.find("{{") {
        let Some(rel_end) = html[start + 2..].find("}}") else {
            break;
        };
        let end = start + 2 + rel_end;
        let key = html[start + 2..end].to_string();
        let translated = crate::i18n::tr_in(lang, &key);
        html.replace_range(start..end + 2, translated);
    }
    HttpResult {
        status: 200,
        content_type: "text/html; charset=utf-8",
        body: html.into_bytes(),
    }
}

/// Serve the dashboard until the process is interrupted (Ctrl-C).
pub fn run(app: &App, port: u16, open_browser: bool) -> Result<i32> {
    let addr = format!("127.0.0.1:{port}");
    let server = Server::http(&addr)
        .map_err(|e| anyhow::anyhow!("cannot bind {addr}: {e}"))?;
    let url = format!("http://{addr}/");
    println!(
        "{}",
        crate::tr_fmt!("am web — {} (Ctrl-C pour arrêter)", url)
    );
    if open_browser {
        println!("{}", crate::i18n::tr("ouverture du navigateur…"));
        open_in_browser(&url);
    }
    for request in server.incoming_requests() {
        let method = request.method().clone();
        let url = request.url().to_string();
        let result = handle(app, &method, &url);
        let response = Response::from_data(result.body)
            .with_status_code(StatusCode(result.status))
            .with_header(
                Header::from_bytes(b"Content-Type", result.content_type.as_bytes())
                    .expect("valid content-type"),
            )
            .with_header(Header::from_bytes(b"Cache-Control", b"no-store").expect("valid header"));
        let _ = request.respond(response);
    }
    Ok(0)
}

/// Open the dashboard in the default browser (best effort, per platform).
pub fn open_in_browser(url: &str) {
    #[cfg(target_os = "windows")]
    {
        // 'start' is a cmd builtin; the empty quoted argument protects
        // URLs containing '&'.
        let _ = std::process::Command::new("cmd")
            .args(["/C", "start", "", url])
            .spawn();
    }
    #[cfg(target_os = "macos")]
    {
        let _ = std::process::Command::new("open").arg(url).spawn();
    }
    #[cfg(all(unix, not(target_os = "macos")))]
    {
        let _ = std::process::Command::new("xdg-open").arg(url).spawn();
    }
}

// ---------------------------------------------------------------------------
// Query parsing (tiny, standard library only)
// ---------------------------------------------------------------------------

/// Split `path?query` into the path and the decoded query parameters.
fn split_query(target: &str) -> (&str, Vec<(String, String)>) {
    match target.split_once('?') {
        Some((p, q)) => (p, parse_query(q)),
        None => (target, Vec::new()),
    }
}

fn parse_query(query: &str) -> Vec<(String, String)> {
    query
        .split('&')
        .filter_map(|kv| {
            let (k, v) = kv.split_once('=')?;
            Some((percent_decode(k), percent_decode(v)))
        })
        .collect()
}

fn query_get(params: &[(String, String)], key: &str) -> Option<String> {
    params
        .iter()
        .find(|(k, _)| k == key)
        .map(|(_, v)| v.clone())
}

/// Decode `+` as space and `%XX` as a byte (best effort; unknown escapes
/// are kept verbatim).
fn percent_decode(s: &str) -> String {
    let bytes = s.as_bytes();
    let mut out = Vec::with_capacity(bytes.len());
    let mut i = 0;
    while i < bytes.len() {
        match bytes[i] {
            b'+' => out.push(b' '),
            b'%' if i + 2 < bytes.len() => {
                let hex = u8::from_str_radix(&s[i + 1..i + 3], 16).unwrap_or(b'%');
                out.push(hex);
                i += 2;
            }
            b => out.push(b),
        }
        i += 1;
    }
    String::from_utf8_lossy(&out).into_owned()
}

#[cfg(test)]
mod tests {
    use super::*;
    use clap::Parser;

    fn test_app() -> App {
        let guard = tempfile::tempdir().unwrap();
        let dir = guard.path().to_path_buf();
        std::mem::forget(guard);
        let cfg = dir.join("config.yaml");
        std::fs::write(
            &cfg,
            "version: \"1.0\"\nsettings:\n  auto_install_deps: false\nagents: []\n",
        )
        .unwrap();
        let cli = crate::cli::Cli::parse_from(["am", "--config", cfg.to_str().unwrap()]);
        let mut app = crate::app::App::from_cli(cli).unwrap();
        let mut p = app.paths.clone();
        p.install_dir = dir.join("agents");
        p.bin_dir = dir.join("agents").join("bin");
        p.log_dir = dir.join("logs");
        p.state_file = dir.join("state.json");
        p.probe_cache_file = dir.join("probe-cache.json");
        p.config_dir = Some(dir.join("config"));
        app.paths = p;
        app.state = crate::state::StateStore::new(dir.join("state.json"));
        app
    }

    #[test]
    fn percent_decode_handles_plus_and_hex() {
        assert_eq!(percent_decode("a+b%20c%41"), "a b cA");
        assert_eq!(percent_decode("plain"), "plain");
        assert_eq!(percent_decode("100%"), "100%"); // truncated escape kept
    }

    #[test]
    fn parse_query_splits_and_decodes() {
        let (path, params) = split_query("/api/events?agent=claude-code&limit=5&q=a+b");
        assert_eq!(path, "/api/events");
        assert_eq!(params.len(), 3);
        assert_eq!(query_get(&params, "agent").as_deref(), Some("claude-code"));
        assert_eq!(query_get(&params, "limit").as_deref(), Some("5"));
        assert_eq!(query_get(&params, "q").as_deref(), Some("a b"));
        assert_eq!(query_get(&params, "missing"), None);
    }

    #[test]
    fn only_get_is_allowed() {
        let app = test_app();
        let r = handle(&app, &Method::Post, "/api/stats");
        assert_eq!(r.status, 405);
        let r = handle(&app, &Method::Get, "/api/stats");
        assert_eq!(r.status, 200);
    }

    #[test]
    fn unknown_route_is_404() {
        let app = test_app();
        let r = handle(&app, &Method::Get, "/api/nope");
        assert_eq!(r.status, 404);
    }

    #[test]
    fn health_reports_ok() {
        let app = test_app();
        let r = handle(&app, &Method::Get, "/api/health");
        assert_eq!(r.status, 200);
        let v: serde_json::Value = serde_json::from_slice(&r.body).unwrap();
        assert_eq!(v["status"], "ok");
        assert!(v["version"].is_string());
    }

    #[test]
    fn api_contracts_serialize_as_json_arrays() {
        let app = test_app();
        for route in [
            "/api/overview",
            "/api/stats",
            "/api/sessions",
            "/api/events",
            "/api/projects",
        ] {
            let r = handle(&app, &Method::Get, route);
            assert_eq!(r.status, 200, "{route}");
            let v: serde_json::Value = serde_json::from_slice(&r.body).unwrap_or_else(|e| {
                panic!("{route}: invalid JSON ({e}): {}", String::from_utf8_lossy(&r.body))
            });
            assert!(v.is_object() || v.is_array(), "{route} must be JSON data");
        }
    }

    #[test]
    fn index_is_served_with_localized_labels() {
        let app = test_app();
        app.set_lang(crate::i18n::Lang::En);
        let r = handle(&app, &Method::Get, "/");
        assert_eq!(r.status, 200);
        let html = String::from_utf8_lossy(&r.body).into_owned();
        assert!(html.contains("<!DOCTYPE html>"));
        assert!(html.contains("Overview"), "EN labels injected");
        assert!(!html.contains("{{"), "no leftover tokens: {html}");
        assert!(html.contains("window.I18N"), "status bundle injected");
    }
}