//! Admin-only crawler observability + control endpoints.
//!
//! Mounted under `/api/v1/admin/crawler*`, cookie-only via `RequireAdmin`.
//! All control endpoints return 503 when the crawler daemon is disabled
//! (`AppState.crawler == None`). Reads compose the live in-process status
//! ([`crate::crawler::status`]) with DB-derived queue counts and the
//! session/browser flags.

use std::convert::Infallible;
use std::time::Duration;

use axum::extract::{Query, State};
use axum::response::sse::{Event, KeepAlive, Sse};
use axum::routing::{get, post};
use axum::{Json, Router};
use futures_util::stream::Stream;
use serde::{Deserialize, Serialize};
use serde_json::json;
use uuid::Uuid;

use crate::app::{AppState, CrawlerControl};
use crate::auth::extractor::RequireAdmin;
use crate::crawler::browser_manager::RestartPhase;
use crate::crawler::status::{LastPass, Phase, WorkerState};
use crate::error::{AppError, AppResult};
use crate::repo;
use crate::repo::crawler::{DeadJob, RequeueScope};

/// Backstop recompose interval for the SSE stream. Phase/worker/session
/// changes push instantly via the status `watch`; this only bounds the
/// staleness of DB-derived queue counts and the browser phase when those
/// change without an accompanying status poke.
const SSE_BACKSTOP: Duration = Duration::from_secs(5);

pub fn routes() -> Router<AppState> {
    Router::new()
        .route("/admin/crawler", get(get_status))
        .route("/admin/crawler/stream", get(stream_status))
        .route("/admin/crawler/run", post(run_now))
        .route("/admin/crawler/browser/restart", post(restart_browser))
        .route("/admin/crawler/session", post(update_session))
        .route(
            "/admin/crawler/session/clear-expired",
            post(clear_session_expired),
        )
        .route("/admin/crawler/dead-jobs", get(list_dead_jobs))
        .route("/admin/crawler/dead-jobs/requeue", post(requeue_dead_jobs))
}

// ---------------------------------------------------------------------------
// GET /admin/crawler — live status
// ---------------------------------------------------------------------------

#[derive(Debug, Serialize)]
struct QueueCounts {
    pending: i64,
    running: i64,
    dead: i64,
}

#[derive(Debug, Serialize)]
struct SessionStatus {
    /// Whether the sticky session-expired flag is set (chapter workers idle).
    expired: bool,
    /// Whether a PHPSESSID is currently configured at all.
    configured: bool,
}

#[derive(Debug, Serialize)]
struct CrawlerStatusResponse {
    /// `"running"` | `"disabled"`.
    daemon: &'static str,
    phase: Option<Phase>,
    workers: Vec<WorkerState>,
    last_pass: LastPass,
    session: SessionStatus,
    /// `"healthy"` | `"draining"` | `"restarting"` | `"down"`.
    browser: &'static str,
    queue: QueueCounts,
}

fn browser_phase_str(p: RestartPhase) -> &'static str {
    match p {
        RestartPhase::Healthy => "healthy",
        RestartPhase::Draining => "draining",
        RestartPhase::Restarting => "restarting",
    }
}

/// Compose a full status snapshot from the in-memory status, the
/// browser/session flags, and a fresh DB queue-count query. Shared by the
/// one-shot `get_status` and the SSE `stream_status`.
async fn compose_status(state: &AppState) -> AppResult<CrawlerStatusResponse> {
    let (pending, running, dead) = repo::crawler::job_state_counts(&state.db).await?;
    let queue = QueueCounts {
        pending,
        running,
        dead,
    };

    Ok(match state.crawler.as_ref() {
        None => CrawlerStatusResponse {
            daemon: "disabled",
            phase: None,
            workers: Vec::new(),
            last_pass: LastPass::default(),
            session: SessionStatus {
                expired: false,
                configured: false,
            },
            browser: "down",
            queue,
        },
        Some(c) => {
            let snap = c.status.snapshot().await;
            CrawlerStatusResponse {
                daemon: "running",
                phase: Some(snap.phase),
                workers: snap.workers,
                last_pass: snap.last_pass,
                session: SessionStatus {
                    expired: c.session.is_expired(),
                    configured: c.session.current().await.is_some(),
                },
                browser: browser_phase_str(c.browser_manager.phase()),
                queue,
            }
        }
    })
}

async fn get_status(
    State(state): State<AppState>,
    _admin: RequireAdmin,
) -> AppResult<Json<CrawlerStatusResponse>> {
    Ok(Json(compose_status(&state).await?))
}

// ---------------------------------------------------------------------------
// GET /admin/crawler/stream — Server-Sent Events live status
// ---------------------------------------------------------------------------

/// Push live status to the dashboard instead of polling. Emits a snapshot
/// immediately on connect, then on every status change (instant, via the
/// `watch` notifier) and on a [`SSE_BACKSTOP`] tick (to refresh DB queue
/// counts / browser phase that change without a status poke). The browser
/// opens this only while the crawler page is mounted and closes it on
/// navigate-away, so the subscription is scoped to the active page.
async fn stream_status(
    State(state): State<AppState>,
    _admin: RequireAdmin,
) -> Sse<impl Stream<Item = Result<Event, Infallible>>> {
    // Subscribe before the first emit so no change between the initial
    // snapshot and the first await is lost.
    let rx = state.crawler.as_ref().map(|c| c.status.subscribe());

    let stream = futures_util::stream::unfold(
        (state, rx, true),
        |(state, mut rx, first)| async move {
            // After the first immediate emit, wait for a change or the
            // backstop tick before recomposing.
            if !first {
                match rx.as_mut() {
                    Some(rx) => {
                        tokio::select! {
                            _ = rx.changed() => {}
                            _ = tokio::time::sleep(SSE_BACKSTOP) => {}
                        }
                    }
                    None => tokio::time::sleep(SSE_BACKSTOP).await,
                }
            }
            // Compose; on a transient DB error, emit a keep-alive comment
            // rather than tearing down the stream.
            let event = match compose_status(&state).await {
                Ok(resp) => Event::default()
                    .event("status")
                    .json_data(&resp)
                    .unwrap_or_else(|_| Event::default().comment("serialize error")),
                Err(_) => Event::default().comment("status unavailable"),
            };
            Some((Ok(event), (state, rx, false)))
        },
    );

    Sse::new(stream).keep_alive(KeepAlive::default())
}

// ---------------------------------------------------------------------------
// POST /admin/crawler/run — trigger an out-of-cycle metadata pass
// ---------------------------------------------------------------------------

#[derive(Debug, Serialize)]
struct RunResponse {
    started: bool,
}

async fn run_now(
    State(state): State<AppState>,
    admin: RequireAdmin,
) -> AppResult<Json<RunResponse>> {
    let c = require_crawler(&state)?;
    let mp = c.metadata_pass.as_ref().ok_or_else(|| {
        AppError::ServiceUnavailable("no source configured (CRAWLER_START_URL unset)".into())
    })?;
    let mp = std::sync::Arc::clone(mp);
    // Fire-and-forget: the pass can run for minutes; the dashboard polls
    // status for progress. Overlap with the daily cron is rare (daily) and
    // both serialise on the single browser lease.
    tokio::spawn(async move {
        if let Err(e) = mp.run().await {
            tracing::warn!(error = ?e, "manual metadata pass failed");
        }
    });
    repo::admin_audit::insert(&state.db, admin.0.id, "crawler_run", "crawler", None, json!({}))
        .await?;
    Ok(Json(RunResponse { started: true }))
}

// ---------------------------------------------------------------------------
// POST /admin/crawler/browser/restart — coordinated restart
// ---------------------------------------------------------------------------

#[derive(Debug, Serialize)]
struct RestartResponse {
    ok: bool,
    error: Option<String>,
}

async fn restart_browser(
    State(state): State<AppState>,
    admin: RequireAdmin,
) -> AppResult<Json<RestartResponse>> {
    let c = require_crawler(&state)?;
    let result = c.browser_manager.coordinated_restart(c.drain_deadline).await;
    // A successful coordinated_restart re-runs on_launch, which re-injects
    // PHPSESSID and re-probes — i.e. the session is live. Drop the sticky
    // `session_expired` flag so chapter workers stop idling without
    // requiring a second click on "Clear expired".
    if result.is_ok() {
        c.session.clear_expired();
    }
    // Push the post-restart browser phase to live subscribers immediately.
    c.status.poke();
    repo::admin_audit::insert(
        &state.db,
        admin.0.id,
        "crawler_browser_restart",
        "crawler",
        None,
        json!({ "ok": result.is_ok() }),
    )
    .await?;
    Ok(Json(match result {
        Ok(()) => RestartResponse {
            ok: true,
            error: None,
        },
        Err(e) => RestartResponse {
            ok: false,
            error: Some(format!("{e:#}")),
        },
    }))
}

// ---------------------------------------------------------------------------
// POST /admin/crawler/session — refresh PHPSESSID
// ---------------------------------------------------------------------------

#[derive(Debug, Deserialize)]
struct UpdateSessionRequest {
    phpsessid: String,
}

#[derive(Debug, Serialize)]
struct UpdateSessionResponse {
    /// Whether the post-update browser relaunch + session probe succeeded.
    valid: bool,
    error: Option<String>,
}

async fn update_session(
    State(state): State<AppState>,
    admin: RequireAdmin,
    Json(body): Json<UpdateSessionRequest>,
) -> AppResult<Json<UpdateSessionResponse>> {
    let c = require_crawler(&state)?;
    c.session
        .update(&body.phpsessid)
        .await
        .map_err(|e| AppError::InvalidInput(format!("{e:#}")))?;
    // Relaunch the browser so on_launch re-injects the new cookie and
    // re-probes — the restart's success IS the session-validity signal.
    let probe = c.browser_manager.coordinated_restart(c.drain_deadline).await;
    // Session + browser state changed — push to live subscribers.
    c.status.poke();
    repo::admin_audit::insert(
        &state.db,
        admin.0.id,
        "crawler_session_update",
        "crawler",
        None,
        json!({ "valid": probe.is_ok() }),
    )
    .await?;
    Ok(Json(match probe {
        Ok(()) => UpdateSessionResponse {
            valid: true,
            error: None,
        },
        Err(e) => UpdateSessionResponse {
            valid: false,
            error: Some(format!("{e:#}")),
        },
    }))
}

#[derive(Debug, Serialize)]
struct ClearExpiredResponse {
    cleared: bool,
}

async fn clear_session_expired(
    State(state): State<AppState>,
    admin: RequireAdmin,
) -> AppResult<Json<ClearExpiredResponse>> {
    let c = require_crawler(&state)?;
    c.session.clear_expired();
    // session.expired flipped — push to live subscribers.
    c.status.poke();
    repo::admin_audit::insert(
        &state.db,
        admin.0.id,
        "crawler_session_clear_expired",
        "crawler",
        None,
        json!({}),
    )
    .await?;
    Ok(Json(ClearExpiredResponse { cleared: true }))
}

// ---------------------------------------------------------------------------
// Dead jobs
// ---------------------------------------------------------------------------

#[derive(Debug, Deserialize, Default)]
struct DeadJobsParams {
    #[serde(default)]
    search: Option<String>,
    #[serde(default = "default_limit")]
    limit: i64,
    #[serde(default)]
    offset: i64,
}

fn default_limit() -> i64 {
    50
}

async fn list_dead_jobs(
    State(state): State<AppState>,
    _admin: RequireAdmin,
    Query(params): Query<DeadJobsParams>,
) -> AppResult<Json<crate::api::pagination::PagedResponse<DeadJob>>> {
    let limit = params.limit.clamp(1, 200);
    let offset = params.offset.max(0);
    let search = params.search.filter(|s| !s.trim().is_empty());
    let (items, total) =
        repo::crawler::list_dead_jobs(&state.db, search.as_deref(), limit, offset).await?;
    Ok(Json(crate::api::pagination::PagedResponse::with_total(
        items, limit, offset, total,
    )))
}

#[derive(Debug, Deserialize)]
#[serde(tag = "scope", rename_all = "snake_case")]
enum RequeueRequest {
    All,
    Manga { manga_id: Uuid },
    Chapter { chapter_id: Uuid },
    Job { job_id: Uuid },
}

#[derive(Debug, Serialize)]
struct RequeueResponse {
    requeued: u64,
}

async fn requeue_dead_jobs(
    State(state): State<AppState>,
    admin: RequireAdmin,
    Json(body): Json<RequeueRequest>,
) -> AppResult<Json<RequeueResponse>> {
    let scope = match &body {
        RequeueRequest::All => RequeueScope::All,
        RequeueRequest::Manga { manga_id } => RequeueScope::Manga(*manga_id),
        RequeueRequest::Chapter { chapter_id } => RequeueScope::Chapter(*chapter_id),
        RequeueRequest::Job { job_id } => RequeueScope::Job(*job_id),
    };
    let requeued = repo::crawler::requeue_dead_jobs(&state.db, scope).await?;
    repo::admin_audit::insert(
        &state.db,
        admin.0.id,
        "crawler_dead_jobs_requeue",
        "crawler",
        None,
        json!({ "requeued": requeued, "scope": scope_label(&body) }),
    )
    .await?;
    Ok(Json(RequeueResponse { requeued }))
}

fn scope_label(r: &RequeueRequest) -> &'static str {
    match r {
        RequeueRequest::All => "all",
        RequeueRequest::Manga { .. } => "manga",
        RequeueRequest::Chapter { .. } => "chapter",
        RequeueRequest::Job { .. } => "job",
    }
}

// ---------------------------------------------------------------------------

fn require_crawler(state: &AppState) -> Result<&std::sync::Arc<CrawlerControl>, AppError> {
    state.crawler.as_ref().ok_or_else(|| {
        AppError::ServiceUnavailable("crawler daemon is disabled".into())
    })
}