//! Live-update plumbing for `report --serve`: a background refresher that
//! re-scans the recipe `reports/` dirs when the file system says something
//! changed, and an SSE endpoint (`/events`) that pushes the rows JSON to the
//! page whenever the scan result differs (a new report file, a bench
//! finishing, a log growing).
//!
//! The refresher is event-driven, not a fixed poll: a `notify` watcher
//! (FSEvents on macOS, inotify on Linux) over the recipe dirs feeds an mpsc
//! channel; after a short debounce burst the rows are re-collected and
//! published on the `watch` channel only when the serialization changed.
//! Filesystem events are filtered to the report-relevant paths (anything
//! under a `reports/` dir, or a `recipe.toml`), so build churn elsewhere in
//! the repo is ignored. A slow keepalive scan stays as a safety net for
//! missed notifications (legacy log-only reports, dirs created late).
//!
//! One refresher serves all clients: each SSE connection forwards its own
//! `watch::Receiver`.

use crate::config::Config;
use crate::report::collect;
use axum::{
    Router,
    extract::Path,
    response::{Response, Sse, sse::Event as SseEvent},
    routing::get,
};
use futures::{Stream, StreamExt};
use notify::Watcher;
use std::convert::Infallible;
use std::sync::Arc;
use std::time::Duration;

/// Safety-net rescan interval: covers missed watcher notifications (a
/// legacy `.log`-only report whose score lands in a Modify the filter
/// ignores, a source dir created after startup). The normal path is the
/// event-driven one, so this can stay slow.
pub(crate) const KEEPALIVE: Duration = Duration::from_secs(30);

/// Wait after a filesystem event before re-scanning, so a write burst
/// (the launcher copying a report triplet) collapses into one collect.
const DEBOUNCE: Duration = Duration::from_millis(500);

/// Shared server state: the config (for `/r/...` file loads) plus the
/// latest rows JSON (each SSE connection clones the receiver).
#[derive(Clone)]
pub(crate) struct AppState {
    pub(crate) config: Arc<Config>,
    pub(crate) data: tokio::sync::watch::Receiver<String>,
}

/// True when the event touches a report-relevant path: anything under a
/// `reports/` directory, or a `recipe.toml` (row fields come from it).
/// Everything else (build churn, git, the rest of the repo) is ignored so
/// the watcher can watch a wide tree cheaply.
fn is_relevant(ev: &notify::Event) -> bool {
    ev.paths.iter().any(|p| {
        p.ancestors()
            .any(|a| a.file_name().is_some_and(|n| n == "reports"))
            || p.file_name().is_some_and(|n| n == "recipe.toml")
    })
}

/// Background refresher: watch the recipe dirs, re-collect after a debounced
/// filesystem event (or the keepalive safety net), publish the rows JSON on
/// the watch channel only when it changed. The first collect runs
/// immediately so clients see current data without waiting. If the watcher
/// cannot be created (unsupported FS), the keepalive alone keeps the data
/// fresh.
pub(crate) async fn refresh_loop(
    cfg: Arc<Config>,
    tx: tokio::sync::watch::Sender<String>,
    keepalive: Duration,
) {
    let (ev_tx, mut ev_rx) = tokio::sync::mpsc::unbounded_channel::<()>();
    let watcher = notify::recommended_watcher(move |res: Result<notify::Event, notify::Error>| {
        if let Ok(ev) = res
            && is_relevant(&ev)
        {
            let _ = ev_tx.send(());
        }
    });
    let mut watcher = watcher.ok();
    if let Some(w) = &mut watcher {
        for dir in crate::config::recipe_dirs(&cfg) {
            if dir.is_dir() {
                let _ = w.watch(&dir, notify::RecursiveMode::Recursive);
            }
        }
    }
    let mut last = String::new();
    loop {
        tokio::select! {
            _ = ev_rx.recv() => {}
            _ = tokio::time::sleep(keepalive) => {}
        }
        // debounce: let the burst settle, then drain the remaining events
        tokio::time::sleep(DEBOUNCE).await;
        while ev_rx.try_recv().is_ok() {}
        let json = serde_json::to_string(&collect(&cfg)).unwrap_or_default();
        if json != last {
            last = json;
            let _ = tx.send(last.clone());
        }
    }
}

/// `GET /events` — the latest rows JSON on connect, then one message per
/// refresher update. The stream ends when the refresher (the sender) drops.
async fn events_stream(
    axum::extract::State(s): axum::extract::State<AppState>,
) -> Sse<impl Stream<Item = Result<SseEvent, Infallible>>> {
    let mut rx = s.data;
    let first = rx.borrow_and_update().clone();
    let first = futures::stream::once(async move { Ok(SseEvent::default().data(first)) });
    let rest = futures::stream::unfold(rx, |mut rx| async move {
        if rx.changed().await.is_err() {
            return None;
        }
        let json = rx.borrow_and_update().clone();
        Some((Ok(SseEvent::default().data(json)), rx))
    });
    Sse::new(first.chain(rest))
}

/// `GET /r/<recipe>/<file>` — full file text (report, log, json, or the
/// recipe's own `recipe.toml`) served through the viewer page. Both path
/// parts must be plain names (no traversal); the resolve walks every
/// recipe dir, so stay strict.
pub(crate) fn load_report(config: &Config, recipe: &str, file: &str) -> Option<String> {
    let plain = |s: &str| {
        !s.contains("..")
            && s.chars()
                .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | '-'))
    };
    if !plain(recipe) || !plain(file) {
        return None;
    }
    crate::config::recipe_dirs(config)
        .into_iter()
        .find_map(|dir| {
            let base = dir.join(recipe);
            // "recipe.toml" resolves from the recipe dir root, everything
            // else from its reports/ subdir
            let p = if file == "recipe.toml" {
                base.join("recipe.toml")
            } else {
                base.join("reports").join(file)
            };
            p.is_file()
                .then(|| std::fs::read_to_string(p).ok())
                .flatten()
        })
}

/// `GET /r/<recipe>/<file>` — file viewer page: rendered markdown (with a
/// raw toggle), syntax-highlighted TOML/JSON, plain logs.
const VIEW_TEMPLATE: &str = include_str!("view.html");

async fn report_file(
    axum::extract::State(state): axum::extract::State<AppState>,
    axum::extract::Path((recipe, file)): Path<(String, String)>,
) -> Response {
    use axum::http::StatusCode;
    use axum::response::IntoResponse;
    match load_report(&state.config, &recipe, &file) {
        Some(text) => {
            // Strip ANSI escapes (old logs were saved raw; new ones are
            // already clean) and normalize line ends: the old pty-saved
            // logs carry CRLF (ONLCR) and the Live-soup ones bare \r —
            // CRLF first, then lone \r, so nothing doubles.
            let clean = crate::ansi::strip_ansi(text.as_bytes());
            let clean = String::from_utf8_lossy(&clean)
                .replace("\r\n", "\n")
                .replace('\r', "\n");
            let meta = serde_json::json!({ "recipe": recipe, "file": file, "content": clean });
            let meta = serde_json::to_string(&meta)
                .unwrap_or_default()
                .replace('<', "\\u003c");
            axum::response::Html(VIEW_TEMPLATE.replace("{{META}}", &meta)).into_response()
        }
        None => (
            StatusCode::NOT_FOUND,
            axum::response::Html(
                "<!doctype html><meta charset=\"utf-8\"><title>404</title>report not found"
                    .to_string(),
            ),
        )
            .into_response(),
    }
}

/// Build the report server router: static page at `/`, live SSE at
/// `/events`, full report text at `/r/<recipe>/<file>`. `initial` is the
/// rows JSON snapshot used to seed the watch channel (from the same
/// `collect` that rendered the page, so the first paint and the first SSE
/// message agree).
pub(crate) fn router(config: Arc<Config>, page: String, initial: String) -> Router {
    let (tx, rx) = tokio::sync::watch::channel(initial);
    tokio::spawn(refresh_loop(config.clone(), tx, KEEPALIVE));
    Router::new()
        .route(
            "/",
            get(move || {
                let page = page.clone();
                async move { axum::response::Html(page) }
            }),
        )
        .route("/events", get(events_stream))
        .route("/r/{recipe}/{file}", get(report_file))
        .with_state(AppState { config, data: rx })
}