package app

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"git.az-it.net/az/morz-infoboard/player/agent/internal/config"
	"git.az-it.net/az/morz-infoboard/player/agent/internal/mqttheartbeat"
	"git.az-it.net/az/morz-infoboard/player/agent/internal/mqttsubscriber"
	"git.az-it.net/az/morz-infoboard/player/agent/internal/playerserver"
	"git.az-it.net/az/morz-infoboard/player/agent/internal/statusreporter"
)

type Status string

type Connectivity string

const (
	StatusStarting Status = "starting"
	StatusRunning  Status = "running"
	StatusStopped  Status = "stopped"

	ConnectivityUnknown  Connectivity = "unknown"
	ConnectivityOnline   Connectivity = "online"
	ConnectivityDegraded Connectivity = "degraded"
	ConnectivityOffline  Connectivity = "offline"
)

const offlineFailureThreshold = 3

type HealthSnapshot struct {
	Status             Status
	ServerConnectivity Connectivity
	ScreenID           string
	ServerBaseURL      string
	MQTTBroker         string
	HeartbeatEvery     int
	StartedAt          time.Time
	LastHeartbeatAt    time.Time
}

type App struct {
	Config   config.Config
	logger   *log.Logger
	now      func() time.Time
	reporter statusSender
	mqttPub  mqttSender

	mu                        sync.RWMutex
	status                    Status
	serverConnectivity        Connectivity
	consecutiveReportFailures int
	startedAt                 time.Time
	lastHeartbeatAt           time.Time

	// Playlist fetched from the backend (protected by playlistMu).
	playlistMu sync.RWMutex
	playlist   []playerserver.PlaylistItem

	// mqttFetchC receives a signal whenever a playlist-changed MQTT message
	// arrives (after debouncing in the subscriber).  pollPlaylist listens on
	// this channel to trigger an immediate fetchPlaylist call.
	mqttFetchC chan struct{}
}

type statusSender interface {
	Send(ctx context.Context, snapshot statusreporter.Snapshot) error
}

type mqttSender interface {
	SendHeartbeat(status, connectivity string, ts time.Time) error
	Close()
}

func New() (*App, error) {
	cfg, err := config.Load()
	if err != nil {
		return nil, err
	}

	logger := log.New(os.Stdout, "agent ", log.LstdFlags|log.LUTC)

	var mqttPub mqttSender
	if cfg.MQTTBroker != "" {
		mqttPub = mqttheartbeat.New(cfg.MQTTBroker, cfg.ScreenID, cfg.MQTTUsername, cfg.MQTTPassword)
		logger.Printf("event=mqtt_enabled broker=%s", cfg.MQTTBroker)
	} else {
		logger.Printf("event=mqtt_disabled reason=no_broker_configured")
	}

	return newApp(cfg, logger, time.Now, statusreporter.New(cfg.ServerBaseURL, nil, time.Now), mqttPub), nil
}

func newApp(cfg config.Config, logger *log.Logger, now func() time.Time, reporter statusSender, mqttPub mqttSender) *App {
	if logger == nil {
		logger = log.New(os.Stdout, "agent ", log.LstdFlags|log.LUTC)
	}

	if now == nil {
		now = time.Now
	}

	return &App{
		Config:             cfg,
		logger:             logger,
		now:                now,
		reporter:           reporter,
		mqttPub:            mqttPub,
		status:             StatusStarting,
		serverConnectivity: ConnectivityUnknown,
		mqttFetchC:         make(chan struct{}, 1),
	}
}

func (a *App) Snapshot() HealthSnapshot {
	a.mu.RLock()
	defer a.mu.RUnlock()

	return HealthSnapshot{
		Status:             a.status,
		ServerConnectivity: a.serverConnectivity,
		ScreenID:           a.Config.ScreenID,
		ServerBaseURL:      a.Config.ServerBaseURL,
		MQTTBroker:         a.Config.MQTTBroker,
		HeartbeatEvery:     a.Config.HeartbeatEvery,
		StartedAt:          a.startedAt,
		LastHeartbeatAt:    a.lastHeartbeatAt,
	}
}

func (a *App) Run(ctx context.Context) error {
	if a.Config.ScreenID == "" {
		return fmt.Errorf("screen id is required")
	}

	select {
	case <-ctx.Done():
		a.mu.Lock()
		a.status = StatusStopped
		a.mu.Unlock()
		return nil
	default:
	}

	a.mu.Lock()
	a.startedAt = a.now()
	a.mu.Unlock()

	a.logger.Printf(
		"event=agent_configured screen_id=%s screen_name=%q orientation=%s server_url=%s mqtt_broker=%s heartbeat_every_seconds=%d player_addr=%s",
		a.Config.ScreenID,
		a.Config.ScreenName,
		a.Config.ScreenOrientation,
		a.Config.ServerBaseURL,
		a.Config.MQTTBroker,
		a.Config.HeartbeatEvery,
		a.Config.PlayerListenAddr,
	)

	// Start the player HTTP server (serves Chromium UI).
	ps := playerserver.New(a.Config.PlayerListenAddr, func() playerserver.NowPlaying {
		snap := a.Snapshot()
		a.playlistMu.RLock()
		items := a.playlist
		a.playlistMu.RUnlock()

		np := playerserver.NowPlaying{
			Status:       string(snap.Status),
			Connectivity: string(snap.ServerConnectivity),
		}
		if len(items) > 0 {
			np.Playlist = items
		} else if a.Config.PlayerContentURL != "" {
			// Fallback: single static URL when no playlist is available yet.
			np.Playlist = []playerserver.PlaylistItem{{
				Src:             a.Config.PlayerContentURL,
				Type:            "web",
				Title:           "",
				DurationSeconds: 30,
			}}
		}
		return np
	})
	go func() {
		if err := ps.Run(ctx); err != nil {
			a.logger.Printf("event=player_server_error error=%v", err)
		}
	}()

	// Self-register this screen in the backend (best-effort, non-blocking).
	go a.registerScreen(ctx)

	// Subscribe to playlist-changed MQTT notifications (optional; fallback = polling).
	sub := mqttsubscriber.New(
		a.Config.MQTTBroker,
		a.Config.ScreenID,
		a.Config.MQTTUsername,
		a.Config.MQTTPassword,
		func() {
			// Debounced callback: send a non-blocking signal to the fetch channel.
			select {
			case a.mqttFetchC <- struct{}{}:
			default: // already a pending signal — no need to queue another
			}
			a.logger.Printf("event=mqtt_playlist_notification screen_id=%s", a.Config.ScreenID)
		},
	)
	if sub != nil {
		a.logger.Printf("event=mqtt_subscriber_enabled broker=%s screen_id=%s topic=%s",
			a.Config.MQTTBroker, a.Config.ScreenID, mqttsubscriber.Topic(a.Config.ScreenID))
		defer sub.Close()
	}

	// Start polling the backend for playlist updates (60 s fallback + MQTT trigger).
	go a.pollPlaylist(ctx)

	a.emitHeartbeat()
	a.mu.Lock()
	a.status = StatusRunning
	a.mu.Unlock()

	ticker := time.NewTicker(time.Duration(a.Config.HeartbeatEvery) * time.Second)
	defer ticker.Stop()

	reportTicker := time.NewTicker(time.Duration(a.Config.StatusReportEvery) * time.Second)
	defer reportTicker.Stop()
	a.reportStatus(ctx)

	for {
		select {
		case <-ctx.Done():
			a.mu.Lock()
			a.status = StatusStopped
			a.mu.Unlock()
			if a.mqttPub != nil {
				a.mqttPub.Close()
			}
			a.logger.Printf("event=agent_stopped screen_id=%s", a.Config.ScreenID)
			return nil
		case <-ticker.C:
			a.emitHeartbeat()
		case <-reportTicker.C:
			a.reportStatus(ctx)
		}
	}
}

// registerScreen upserts this screen in the backend so it appears in the admin UI.
// Called once at startup in a goroutine — retries every 30s until successful.
func (a *App) registerScreen(ctx context.Context) {
	body, _ := json.Marshal(map[string]string{
		"slug":        a.Config.ScreenID,
		"name":        a.Config.ScreenName,
		"orientation": a.Config.ScreenOrientation,
	})

	for attempt := 1; ; attempt++ {
		req, err := http.NewRequestWithContext(ctx,
			http.MethodPost,
			a.Config.ServerBaseURL+"/api/v1/screens/register",
			bytes.NewReader(body),
		)
		if err != nil {
			return
		}
		req.Header.Set("Content-Type", "application/json")

		resp, err := http.DefaultClient.Do(req)
		if err == nil {
			resp.Body.Close()
			if resp.StatusCode == http.StatusOK {
				a.logger.Printf("event=screen_registered screen_id=%s attempt=%d", a.Config.ScreenID, attempt)
				return
			}
			a.logger.Printf("event=screen_register_failed screen_id=%s status=%d attempt=%d",
				a.Config.ScreenID, resp.StatusCode, attempt)
		} else {
			a.logger.Printf("event=screen_register_failed screen_id=%s error=%v attempt=%d",
				a.Config.ScreenID, err, attempt)
		}

		select {
		case <-ctx.Done():
			return
		case <-time.After(30 * time.Second):
		}
	}
}

// pollPlaylist fetches the active playlist from the backend.
// It fetches immediately on startup, then waits for either:
//   - an MQTT playlist-changed notification (fast path, debounced by subscriber)
//   - the 60-second fallback ticker (in case MQTT is unavailable)
func (a *App) pollPlaylist(ctx context.Context) {
	// Fetch immediately on startup.
	a.fetchPlaylist(ctx)

	ticker := time.NewTicker(60 * time.Second)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-a.mqttFetchC:
			a.logger.Printf("event=playlist_triggered_by_mqtt screen_id=%s", a.Config.ScreenID)
			a.fetchPlaylist(ctx)
		case <-ticker.C:
			a.fetchPlaylist(ctx)
		}
	}
}

// remotePlaylistResponse is the JSON shape of GET /api/v1/screens/{slug}/playlist.
type remotePlaylistResponse struct {
	Items []playerserver.PlaylistItem `json:"items"`
}

func (a *App) fetchPlaylist(ctx context.Context) {
	url := a.Config.ServerBaseURL + "/api/v1/screens/" + a.Config.ScreenID + "/playlist"
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		a.logger.Printf("event=playlist_fetch_failed screen_id=%s error=%v", a.Config.ScreenID, err)
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		a.logger.Printf("event=playlist_fetch_failed screen_id=%s status=%d", a.Config.ScreenID, resp.StatusCode)
		return
	}

	var pr remotePlaylistResponse
	if err := json.NewDecoder(resp.Body).Decode(&pr); err != nil {
		a.logger.Printf("event=playlist_decode_failed screen_id=%s error=%v", a.Config.ScreenID, err)
		return
	}

	for i := range pr.Items {
		if strings.HasPrefix(pr.Items[i].Src, "/") {
			pr.Items[i].Src = a.Config.ServerBaseURL + pr.Items[i].Src
		}
	}

	a.playlistMu.Lock()
	a.playlist = pr.Items
	a.playlistMu.Unlock()

	a.logger.Printf("event=playlist_fetched screen_id=%s items=%d", a.Config.ScreenID, len(pr.Items))
}

func (a *App) emitHeartbeat() {
	now := a.now()

	a.mu.Lock()
	a.lastHeartbeatAt = now
	status := a.status
	connectivity := a.serverConnectivity
	a.mu.Unlock()

	if a.mqttPub != nil {
		if err := a.mqttPub.SendHeartbeat(string(status), string(connectivity), now); err != nil {
			a.logger.Printf("event=mqtt_heartbeat_failed screen_id=%s error=%v", a.Config.ScreenID, err)
		}
	}
}

func (a *App) reportStatus(ctx context.Context) {
	if a.reporter == nil {
		return
	}

	snapshot := a.Snapshot()
	payloadConnectivity := snapshot.ServerConnectivity
	if payloadConnectivity == ConnectivityUnknown || payloadConnectivity == ConnectivityOnline || payloadConnectivity == ConnectivityDegraded || payloadConnectivity == ConnectivityOffline {
		payloadConnectivity = ConnectivityOnline
	}

	err := a.reporter.Send(ctx, statusreporter.Snapshot{
		Status:                string(snapshot.Status),
		ServerConnectivity:    string(payloadConnectivity),
		ScreenID:              snapshot.ScreenID,
		ServerBaseURL:         snapshot.ServerBaseURL,
		MQTTBroker:            snapshot.MQTTBroker,
		HeartbeatEverySeconds: snapshot.HeartbeatEvery,
		StartedAt:             snapshot.StartedAt,
		LastHeartbeatAt:       snapshot.LastHeartbeatAt,
	})
	if err != nil {
		a.mu.Lock()
		a.consecutiveReportFailures++
		a.serverConnectivity = ConnectivityDegraded
		if a.consecutiveReportFailures >= offlineFailureThreshold {
			a.serverConnectivity = ConnectivityOffline
		}
		a.mu.Unlock()
		a.logger.Printf("event=status_report_failed screen_id=%s error=%v", a.Config.ScreenID, err)
		return
	}

	a.mu.Lock()
	a.consecutiveReportFailures = 0
	a.serverConnectivity = ConnectivityOnline
	a.mu.Unlock()
}