//! REST API server for recording management and live telemetry access.
//!
//! Runs as a parallel tokio task alongside the UDP listeners.

use axum::{
    Json, Router,
    extract::{Path, State},
    http::StatusCode,
    response::{IntoResponse, Response},
    routing::{get, post},
};
use serde::{Deserialize, Serialize};
use std::sync::{Arc, Mutex, MutexGuard};
use tower_http::cors::CorsLayer;

use crate::analysis;
use crate::feed_state::FeedState;
use crate::recording::{Game, RecordingManager, RecordingStatus, StartRecordingRequest, UseCase};
use crate::session::SessionManager;
use crate::ui::FeedDisplayInfo;

pub struct AppState {
    pub recording_manager: Arc<RecordingManager>,
    pub feed_displays: Vec<(FeedDisplayInfo, Arc<Mutex<FeedState>>)>,
    pub session_manager: Arc<std::sync::Mutex<SessionManager>>,
}

#[derive(Serialize)]
struct ApiError {
    error: String,
}

fn ok_json<T: Serialize>(data: T) -> Response {
    (StatusCode::OK, Json(data)).into_response()
}

fn err(status: StatusCode, msg: &str) -> Response {
    (
        status,
        Json(ApiError {
            error: msg.to_string(),
        }),
    )
        .into_response()
}

fn lock_sessions(state: &Arc<AppState>) -> MutexGuard<'_, SessionManager> {
    state.session_manager.lock().unwrap_or_else(|e| {
        eprintln!("[WARN] SessionManager mutex poisoned, recovering: {}", e);
        e.into_inner()
    })
}

#[derive(Serialize)]
struct LiveFeedSnapshot {
    label: String,
    port: u16,
    health: String,
    frequency_hz: f64,
    total_packets: u64,
    data_rate_kb_s: f64,
    speed_kmh: Option<f32>,
    gear: Option<String>,
    engine_rpm: Option<f32>,
    throttle: Option<f32>,
    brake: Option<f32>,
    lap_time: Option<String>,
    spline_position: Option<f32>,
}

#[derive(Serialize)]
struct LiveTelemetryResponse {
    feeds: Vec<LiveFeedSnapshot>,
    active_recording: Option<String>,
}

#[derive(Deserialize)]
struct CreateSessionRequest {
    use_case: UseCase,
    label: Option<String>,
}

#[derive(Deserialize)]
struct StartRunRequest {
    feed_name: String,
    label: Option<String>,
}

async fn create_session(
    State(state): State<Arc<AppState>>,
    Json(req): Json<CreateSessionRequest>,
) -> Response {
    let mut mgr = lock_sessions(&state);
    match mgr.create_session(req.use_case, req.label) {
        Ok(session) => (StatusCode::CREATED, Json(session)).into_response(),
        Err(msg) => err(StatusCode::BAD_REQUEST, &msg),
    }
}

async fn list_sessions(State(state): State<Arc<AppState>>) -> Response {
    let mut mgr = lock_sessions(&state);
    ok_json(mgr.list_sessions())
}

async fn get_session(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    let mgr = lock_sessions(&state);
    match mgr.get_session(&id) {
        Some(session) => ok_json(session),
        None => err(StatusCode::NOT_FOUND, "Session not found"),
    }
}

async fn delete_session(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    let mut mgr = lock_sessions(&state);
    match mgr.delete_session(&id) {
        Ok(()) => StatusCode::NO_CONTENT.into_response(),
        Err(msg) => err(StatusCode::NOT_FOUND, &msg),
    }
}

async fn start_run(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
    Json(req): Json<StartRunRequest>,
) -> Response {
    let mut mgr = lock_sessions(&state);
    match mgr.start_run(&id, &req.feed_name, req.label) {
        Ok(run) => (StatusCode::CREATED, Json(run)).into_response(),
        Err(msg) => err(StatusCode::BAD_REQUEST, &msg),
    }
}

async fn stop_run(
    State(state): State<Arc<AppState>>,
    Path((id, run_id)): Path<(String, String)>,
) -> Response {
    let mut mgr = lock_sessions(&state);
    match mgr.stop_run(&id, &run_id) {
        Ok(run) => ok_json(run),
        Err(msg) => err(StatusCode::BAD_REQUEST, &msg),
    }
}

async fn complete_session(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    let (use_case, frames_by_run, run_labels) = {
        let mut mgr = lock_sessions(&state);
        match mgr.complete_session(&id) {
            Ok(_session) => {}
            Err(msg) => return err(StatusCode::BAD_REQUEST, &msg),
        }
        match mgr.collect_run_frames(&id) {
            Some((uc, frames, labels)) => (uc, frames, labels),
            None => return err(StatusCode::NOT_FOUND, "Session not found after completion"),
        }
    };

    let result = analysis::analyze(&use_case, &frames_by_run, &run_labels);

    {
        let mut mgr = lock_sessions(&state);
        let _ = mgr.set_analysis(&id, result);
    }

    let mgr = lock_sessions(&state);
    match mgr.get_session(&id) {
        Some(session) => ok_json(session),
        None => err(StatusCode::INTERNAL_SERVER_ERROR, "Session lost after analysis"),
    }
}

async fn get_analysis(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    let mgr = lock_sessions(&state);
    match mgr.get_session(&id) {
        Some(session) => {
            match session.analysis {
                Some(ref analysis) => ok_json(analysis),
                None => err(StatusCode::NOT_FOUND, "Analysis not available yet. Complete the session first."),
            }
        }
        None => err(StatusCode::NOT_FOUND, "Session not found"),
    }
}

async fn run_analysis(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    let (use_case, frames_by_run, run_labels) = {
        let mgr = lock_sessions(&state);
        match mgr.get_session(&id) {
            Some(session) => {
                if session.status != crate::session::SessionStatus::Completed {
                    return err(StatusCode::BAD_REQUEST, "Session must be completed before analysis");
                }
            }
            None => return err(StatusCode::NOT_FOUND, "Session not found"),
        }
        match mgr.collect_run_frames(&id) {
            Some(data) => data,
            None => return err(StatusCode::NOT_FOUND, "Session not found"),
        }
    };

    let result = analysis::analyze(&use_case, &frames_by_run, &run_labels);

    {
        let mut mgr = lock_sessions(&state);
        let _ = mgr.set_analysis(&id, result.clone());
    }

    ok_json(result)
}

async fn list_recordings(State(state): State<Arc<AppState>>) -> Response {
    match state.recording_manager.list_recordings().await {
        Ok(recordings) => ok_json(recordings),
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to list recordings: {}", e),
        ),
    }
}

async fn get_recording(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    match state.recording_manager.get_recording(&id).await {
        Ok(manifest) => ok_json(manifest),
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
            err(StatusCode::NOT_FOUND, "Recording not found")
        }
        Err(e) if e.kind() == std::io::ErrorKind::InvalidInput => {
            err(StatusCode::BAD_REQUEST, &e.to_string())
        }
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to get recording: {}", e),
        ),
    }
}

async fn start_recording(
    State(state): State<Arc<AppState>>,
    Json(req): Json<StartRecordingRequest>,
) -> Response {
    match state.recording_manager.start_recording(req).await {
        Ok(manifest) => (StatusCode::CREATED, Json(manifest)).into_response(),
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to start recording: {}", e),
        ),
    }
}

async fn stop_recording(State(state): State<Arc<AppState>>) -> Response {
    match state.recording_manager.stop_recording().await {
        Ok(Some(manifest)) => ok_json(manifest),
        Ok(None) => err(StatusCode::BAD_REQUEST, "No active recording to stop"),
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to stop recording: {}", e),
        ),
    }
}

async fn stop_specific_recording(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    let manifest = match state.recording_manager.get_recording(&id).await {
        Ok(m) => m,
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
            return err(StatusCode::NOT_FOUND, "Recording not found")
        }
        Err(e) if e.kind() == std::io::ErrorKind::InvalidInput => {
            return err(StatusCode::BAD_REQUEST, &e.to_string())
        }
        Err(e) => {
            return err(
                StatusCode::INTERNAL_SERVER_ERROR,
                &format!("Failed to get recording: {}", e),
            )
        }
    };

    if manifest.status != RecordingStatus::Recording {
        return err(StatusCode::CONFLICT, "Recording is not active");
    }

    match state
        .recording_manager
        .stop_recording_internal(&id)
        .await
    {
        Ok(stopped) => {
            state
                .recording_manager
                .clear_active_if_matches(&id)
                .await;
            ok_json(stopped)
        }
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to stop recording: {}", e),
        ),
    }
}

async fn delete_recording(
    State(state): State<Arc<AppState>>,
    Path(id): Path<String>,
) -> Response {
    match state.recording_manager.delete_recording(&id).await {
        Ok(()) => StatusCode::NO_CONTENT.into_response(),
        Err(e) if e.kind() == std::io::ErrorKind::InvalidInput => {
            err(StatusCode::CONFLICT, &e.to_string())
        }
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
            err(StatusCode::NOT_FOUND, "Recording not found")
        }
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to delete recording: {}", e),
        ),
    }
}

async fn get_feed_data(
    State(state): State<Arc<AppState>>,
    Path((id, feed_name)): Path<(String, String)>,
) -> Response {
    let active_id = state.recording_manager.active_recording_id().await;
    if active_id.as_deref() == Some(id.as_str()) {
        match state.recording_manager.read_frames(&feed_name) {
            Some(frames) => return ok_json(frames),
            None => {
                return err(
                    StatusCode::NOT_FOUND,
                    &format!("Feed '{}' not found in active recording", feed_name),
                )
            }
        }
    }

    let manifest = match state.recording_manager.get_recording(&id).await {
        Ok(m) => m,
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
            return err(StatusCode::NOT_FOUND, "Recording not found")
        }
        Err(e) if e.kind() == std::io::ErrorKind::InvalidInput => {
            return err(StatusCode::BAD_REQUEST, &e.to_string())
        }
        Err(e) => {
            return err(
                StatusCode::INTERNAL_SERVER_ERROR,
                &format!("Failed to get recording: {}", e),
            )
        }
    };

    let feed_stats = match manifest.feeds.iter().find(|f| f.name == feed_name) {
        Some(f) => f,
        None => {
            return err(
                StatusCode::NOT_FOUND,
                &format!("Feed '{}' not found in recording", feed_name),
            )
        }
    };

    let file_path = manifest.dir_path(state.recording_manager.data_dir()).join(&feed_stats.file);
    if !file_path.exists() {
        return err(StatusCode::NOT_FOUND, "Feed data file not found on disk (recording may still be in progress)");
    }

    match tokio::fs::read_to_string(&file_path).await {
        Ok(content) => {
            let frames: Vec<serde_json::Value> = content
                .lines()
                .filter(|l| !l.is_empty())
                .filter_map(|l| serde_json::from_str(l).ok())
                .collect();
            ok_json(frames)
        }
        Err(e) => err(
            StatusCode::INTERNAL_SERVER_ERROR,
            &format!("Failed to read feed data: {}", e),
        ),
    }
}

async fn get_live(State(state): State<Arc<AppState>>) -> Response {
    let mut feeds = Vec::new();

    for (info, state_arc) in &state.feed_displays {
        let snapshot = state_arc.lock().ok().map(|mut s| {
            s.tick();
            s.clone()
        });

        let snap = match snapshot {
            Some(s) => s,
            None => continue,
        };

        let (speed_kmh, gear, engine_rpm, throttle, brake, lap_time, spline_position) =
            if let Some(ref frame) = snap.last_frame {
                (
                    Some(frame.speed_kmh),
                    Some(frame.gear_display()),
                    Some(frame.engine_rpm),
                    Some(frame.throttle),
                    Some(frame.brake),
                    Some(
                        crate::telemetry_frame::TelemetryFrame::format_lap_time(frame.lap_time_ms),
                    ),
                    Some(frame.spline_position),
                )
            } else {
                (None, None, None, None, None, None, None)
            };

        feeds.push(LiveFeedSnapshot {
            label: info.label.to_string(),
            port: info.port,
            health: format!("{:?}", snap.health).to_lowercase(),
            frequency_hz: snap.frequency_hz,
            total_packets: snap.total_packets,
            data_rate_kb_s: snap.data_rate_kb_s,
            speed_kmh,
            gear,
            engine_rpm,
            throttle,
            brake,
            lap_time,
            spline_position,
        });
    }

    let active_recording = state.recording_manager.active_recording_id().await;

    ok_json(LiveTelemetryResponse {
        feeds,
        active_recording,
    })
}

async fn list_use_cases() -> Response {
    ok_json(UseCase::all())
}

async fn list_games() -> Response {
    ok_json(Game::valid_choices())
}

pub fn build_router(state: Arc<AppState>) -> Router {
    Router::new()
        .route("/api/sessions", get(list_sessions).post(create_session))
        .route("/api/sessions/{id}", get(get_session).delete(delete_session))
        .route("/api/sessions/{id}/runs", post(start_run))
        .route("/api/sessions/{id}/runs/{run_id}/stop", post(stop_run))
        .route("/api/sessions/{id}/complete", post(complete_session))
        .route("/api/sessions/{id}/analysis", get(get_analysis))
        .route("/api/sessions/{id}/analyze", post(run_analysis))
        .route("/api/recordings", get(list_recordings).post(start_recording))
        .route("/api/recordings/stop", post(stop_recording))
        .route(
            "/api/recordings/{id}",
            get(get_recording).delete(delete_recording),
        )
        .route("/api/recordings/{id}/stop", post(stop_specific_recording))
        .route(
            "/api/recordings/{id}/data/{feed_name}",
            get(get_feed_data),
        )
        .route(
            "/api/recordings/{id}/frames/{feed_name}",
            get(get_feed_data),
        )
        .route("/api/live", get(get_live))
        .route("/api/use-cases", get(list_use_cases))
        .route("/api/games", get(list_games))
        .layer(CorsLayer::permissive())
        .with_state(state)
}

pub async fn run_server(state: Arc<AppState>, addr: String, mut shutdown_rx: tokio::sync::watch::Receiver<bool>) {
    let router = build_router(state);
    let listener = match tokio::net::TcpListener::bind(&addr).await {
        Ok(l) => l,
        Err(e) => {
            eprintln!("[ERROR] Failed to bind API server on {}: {}", addr, e);
            return;
        }
    };
    eprintln!("[INFO] REST API server listening on {}", addr);

    let shutdown_signal = async move {
        while shutdown_rx.changed().await.is_ok() {
            if *shutdown_rx.borrow() {
                break;
            }
        }
    };

    if let Err(e) = axum::serve(listener, router)
        .with_graceful_shutdown(shutdown_signal)
        .await
    {
        eprintln!("[ERROR] API server error: {}", e);
    }
    eprintln!("[INFO] REST API server shut down.");
}