// Package jetstream provides an ATProto Jetstream consumer for real-time updates.
// It connects to the Bluesky Jetstream WebSocket, processes repository events,
// indexes manifests and tags, and populates the AppView database for the web UI.
package jetstream

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/url"
	"sync"
	"time"

	"atcr.io/pkg/appview/db"
	"atcr.io/pkg/atproto"
	"github.com/gorilla/websocket"
	"github.com/klauspost/compress/zstd"
)

// UserCache caches DID -> handle/PDS mappings to avoid repeated lookups
type UserCache struct {
	cache map[string]*db.User
}

// EventCallback is called for each processed event
type EventCallback func(timeUS int64)

// Worker consumes Jetstream events and populates the UI database
type Worker struct {
	db                   *sql.DB
	jetstreamURL         string
	endpoints            *EndpointRotator
	startCursor          int64
	wantedCollections    []string
	debugCollectionCount int
	processor            *Processor  // Shared processor for DB operations
	statsCache           *StatsCache // In-memory cache for stats aggregation across holds
	eventCallback        EventCallback
	connStartTime        time.Time // Track when connection started for debugging

	// Ping/pong tracking for connection health
	pingsSent     int64
	pongsReceived int64
	lastPongTime  time.Time
	pongMutex     sync.Mutex

	// In-memory cursor tracking for reconnects
	lastCursor  int64
	cursorMutex sync.RWMutex
}

// NewWorker creates a new Jetstream worker
// startCursor: Unix microseconds timestamp to start from (0 = start from now)
func NewWorker(database *sql.DB, urls []string, startCursor int64) *Worker {
	if len(urls) == 0 {
		urls = []string{"wss://jetstream2.us-west.bsky.network/subscribe"}
	}

	rotator := NewEndpointRotator(urls)

	// Create shared stats cache for aggregating across holds
	statsCache := NewStatsCache()

	return &Worker{
		db:           database,
		jetstreamURL: rotator.Current(),
		endpoints:    rotator,
		startCursor:  startCursor,
		wantedCollections: []string{
			"io.atcr.*",              // Subscribe to all ATCR collections
			"app.bsky.actor.profile", // Subscribe to Bluesky profile updates for avatar sync
		},
		statsCache: statsCache,
		processor:  NewProcessor(database, true, statsCache), // Use cache for live streaming
	}
}

// Start begins consuming Jetstream events
// This is a blocking function that runs until the context is cancelled
func (w *Worker) Start(ctx context.Context) error {
	// Build connection URL with filters
	u, err := url.Parse(w.jetstreamURL)
	if err != nil {
		return fmt.Errorf("invalid jetstream URL: %w", err)
	}

	q := u.Query()
	for _, collection := range w.wantedCollections {
		q.Add("wantedCollections", collection)
	}

	// Add cursor if specified (for backfilling historical data or reconnects)
	if w.startCursor > 0 {
		q.Set("cursor", fmt.Sprintf("%d", w.startCursor))

		// Calculate lag (cursor is in microseconds)
		now := time.Now().UnixMicro()
		lagSeconds := float64(now-w.startCursor) / 1_000_000.0
		slog.Info("Jetstream starting from cursor", "cursor", w.startCursor, "lag_seconds", lagSeconds)
	}

	// Disable compression for now to debug
	// q.Set("compress", "true")
	u.RawQuery = q.Encode()

	slog.Info("Connecting to Jetstream", "url", u.String())

	// Connect to Jetstream
	conn, _, err := websocket.DefaultDialer.DialContext(ctx, u.String(), nil)
	if err != nil {
		return fmt.Errorf("failed to connect to jetstream: %w", err)
	}
	defer conn.Close()

	// Track connection start time for debugging
	w.connStartTime = time.Now()

	// Reset ping/pong counters for this connection
	w.pongMutex.Lock()
	w.pingsSent = 0
	w.pongsReceived = 0
	w.lastPongTime = time.Now()
	w.pongMutex.Unlock()

	// Set up pong handler - called when server responds to our ping
	conn.SetPongHandler(func(appData string) error {
		w.pongMutex.Lock()
		w.pongsReceived++
		w.lastPongTime = time.Now()
		w.pongMutex.Unlock()

		// Reset read deadline - we know connection is alive
		// Allow 90 seconds for next pong (3x ping interval)
		return conn.SetReadDeadline(time.Now().Add(90 * time.Second))
	})

	// Set initial read deadline
	if err := conn.SetReadDeadline(time.Now().Add(90 * time.Second)); err != nil {
		return fmt.Errorf("failed to set read deadline: %w", err)
	}

	// Create zstd decoder for decompressing messages
	decoder, err := zstd.NewReader(nil)
	if err != nil {
		return fmt.Errorf("failed to create zstd decoder: %w", err)
	}
	defer decoder.Close()

	slog.Info("Connected to Jetstream, listening for events...")

	// Start heartbeat ticker to show Jetstream is alive
	heartbeatTicker := time.NewTicker(30 * time.Second)
	defer heartbeatTicker.Stop()

	// Start ping ticker for keepalive
	pingTicker := time.NewTicker(30 * time.Second)
	defer pingTicker.Stop()

	// Start ping sender goroutine
	pingDone := make(chan struct{})
	defer close(pingDone)

	go func() {
		for {
			select {
			case <-ctx.Done():
				return
			case <-pingDone:
				return
			case <-pingTicker.C:
				// Check if we've received a pong recently
				w.pongMutex.Lock()
				timeSinceLastPong := time.Since(w.lastPongTime)
				pingsTotal := w.pingsSent
				pongsTotal := w.pongsReceived
				w.pongMutex.Unlock()

				// If no pong for 60 seconds, connection is likely dead
				if timeSinceLastPong > 60*time.Second {
					slog.Info("Jetstream no pong received, closing connection", "time_since_last_pong", timeSinceLastPong, "pings_sent", pingsTotal, "pongs_received", pongsTotal)
					conn.Close()
					return
				}

				// Send ping with write deadline
				if err := conn.SetWriteDeadline(time.Now().Add(10 * time.Second)); err != nil {
					slog.Warn("Jetstream failed to set write deadline", "error", err)
					conn.Close()
					return
				}
				if err := conn.WriteMessage(websocket.PingMessage, nil); err != nil {
					slog.Warn("Jetstream failed to send ping", "error", err)
					conn.Close()
					return
				}

				w.pongMutex.Lock()
				w.pingsSent++
				w.pongMutex.Unlock()
			}
		}
	}()

	eventCount := 0
	lastHeartbeat := time.Now()

	// Read messages
	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-heartbeatTicker.C:
			elapsed := time.Since(lastHeartbeat)
			slog.Debug("Jetstream alive", "events_processed", eventCount, "elapsed_seconds", elapsed.Seconds())
			eventCount = 0
			lastHeartbeat = time.Now()
		default:
			_, message, err := conn.ReadMessage()
			if err != nil {
				// Calculate connection duration and idle time for debugging
				connDuration := time.Since(w.connStartTime)
				timeSinceLastEvent := time.Since(lastHeartbeat)

				// Get ping/pong stats
				w.pongMutex.Lock()
				pingsTotal := w.pingsSent
				pongsTotal := w.pongsReceived
				timeSinceLastPong := time.Since(w.lastPongTime)
				w.pongMutex.Unlock()

				// Calculate ping/pong success rate
				var pongRate float64
				if pingsTotal > 0 {
					pongRate = float64(pongsTotal) / float64(pingsTotal) * 100
				}

				// Determine diagnosis
				var diagnosis string
				if pongRate >= 95 && timeSinceLastPong < 60*time.Second {
					diagnosis = "Connection was healthy (good ping/pong), likely server-side timeout or network interruption"
				} else if timeSinceLastPong > 60*time.Second {
					diagnosis = "Connection died (no pong for >60s), network issue detected"
				} else if pongRate < 80 {
					diagnosis = "Connection unstable (low pong rate), network quality issues"
				} else {
					diagnosis = "Connection closed unexpectedly"
				}

				// Log detailed context about the failure
				slog.Info("Jetstream connection closed", "duration", connDuration, "events_in_last_30s", eventCount, "time_since_last_event", timeSinceLastEvent, "pongs_received", pongsTotal, "pings_sent", pingsTotal, "pong_rate_pct", pongRate, "time_since_last_pong", timeSinceLastPong, "error", err, "diagnosis", diagnosis)

				return fmt.Errorf("failed to read message: %w", err)
			}

			// For now, process uncompressed messages
			// TODO: Re-enable compression once debugging is complete
			_ = decoder // Keep decoder to avoid unused variable error

			if err := w.processMessage(message); err != nil {
				slog.Error("ERROR processing message", "error", err)
				// Continue processing other messages
			} else {
				eventCount++
			}
		}
	}
}

// StartWithFailover runs the Jetstream worker with automatic failover across endpoints.
// On disconnect it retries the same endpoint with escalating delays (1s, 5s, 10s).
// If all retries fail, it fails over to the next endpoint and rewinds the cursor
// 30 seconds to avoid missing events (events are idempotent DB upserts).
// Cycles through all endpoints indefinitely and never gives up.
func (w *Worker) StartWithFailover(ctx context.Context) {
	retryDelays := []time.Duration{1 * time.Second, 5 * time.Second, 10 * time.Second}

	for {
		currentURL := w.endpoints.Current()
		w.jetstreamURL = currentURL

		slog.Info("Jetstream connecting", "url", currentURL)
		err := w.Start(ctx)
		if ctx.Err() != nil {
			return // Context cancelled, clean shutdown
		}

		// Capture cursor at disconnect time for rewind calculation
		disconnectCursor := w.GetLastCursor()

		// Retry same endpoint with escalating delays
		recovered := false
		for i, delay := range retryDelays {
			slog.Warn("Jetstream disconnected, retrying same endpoint",
				"url", currentURL,
				"attempt", i+1,
				"delay", delay,
				"error", err)
			time.Sleep(delay)

			if ctx.Err() != nil {
				return
			}

			w.jetstreamURL = currentURL
			err = w.Start(ctx)
			if ctx.Err() != nil {
				return
			}
			if err == nil {
				recovered = true
				break
			}
			// Update disconnect cursor if we got further
			if latest := w.GetLastCursor(); latest > disconnectCursor {
				disconnectCursor = latest
			}
		}

		if recovered {
			continue
		}

		// All retries failed — failover to next endpoint
		failedURL := currentURL
		nextURL := w.endpoints.Next()

		// Rewind cursor 30 seconds (30M microseconds) to avoid gaps
		if disconnectCursor > 0 {
			rewound := disconnectCursor - 30_000_000
			if rewound < 0 {
				rewound = 0
			}
			w.cursorMutex.Lock()
			w.lastCursor = rewound
			w.startCursor = rewound
			w.cursorMutex.Unlock()
			slog.Warn("Jetstream failing over to next endpoint",
				"failed_url", failedURL,
				"next_url", nextURL,
				"cursor_rewound_by", "30s")
		} else {
			slog.Warn("Jetstream failing over to next endpoint",
				"failed_url", failedURL,
				"next_url", nextURL)
		}
	}
}

// SetEventCallback sets a callback to be called for each event
func (w *Worker) SetEventCallback(cb EventCallback) {
	w.eventCallback = cb
}

// Processor returns the worker's processor for configuration (e.g., setting webhook dispatcher)
func (w *Worker) Processor() *Processor {
	return w.processor
}

// GetLastCursor returns the last processed cursor (time_us) for reconnects
func (w *Worker) GetLastCursor() int64 {
	w.cursorMutex.RLock()
	defer w.cursorMutex.RUnlock()
	return w.lastCursor
}

// processMessage processes a single Jetstream event
func (w *Worker) processMessage(message []byte) error {
	var event JetstreamEvent
	if err := json.Unmarshal(message, &event); err != nil {
		return fmt.Errorf("failed to unmarshal event: %w", err)
	}

	// Update cursor for reconnects (do this first, even if processing fails)
	w.cursorMutex.Lock()
	w.lastCursor = event.TimeUS
	w.cursorMutex.Unlock()

	// Call callback if set
	if w.eventCallback != nil {
		w.eventCallback(event.TimeUS)
	}

	// Process based on event kind
	switch event.Kind {
	case "commit":
		commit := event.Commit
		if commit == nil {
			return nil
		}

		// Set DID on commit from parent event
		commit.DID = event.DID

		// Debug: log first few collections we see to understand what's coming through
		if w.debugCollectionCount < 5 {
			slog.Debug("Jetstream received collection", "collection", commit.Collection, "did", commit.DID)
			w.debugCollectionCount++
		}

		// Check if this is a collection we care about
		if !isRelevantCollection(commit.Collection) {
			return nil // Ignore irrelevant collections
		}

		// Marshal record to bytes for processing
		var recordBytes []byte
		if commit.Record != nil {
			var err error
			recordBytes, err = json.Marshal(commit.Record)
			if err != nil {
				return fmt.Errorf("failed to marshal record: %w", err)
			}
		}

		// Handle Bluesky profile updates separately (for avatar sync)
		if commit.Collection == BlueskyProfileCollection {
			// Only process creates/updates, not deletes (we don't clear avatars on profile delete)
			if commit.Operation == "delete" {
				return nil
			}
			return w.processor.ProcessProfileUpdate(context.Background(), commit.DID, recordBytes)
		}

		// Log ATCR events (but not Bluesky profile events - too noisy)
		slog.Info("Jetstream processing event",
			"collection", commit.Collection,
			"did", commit.DID,
			"operation", commit.Operation,
			"rkey", commit.RKey)

		isDelete := commit.Operation == "delete"
		return w.processor.ProcessRecord(context.Background(), commit.DID, commit.Collection, commit.RKey, recordBytes, isDelete, nil)

	case "identity":
		if event.Identity == nil {
			return nil
		}
		return w.processIdentity(&event)

	case "account":
		if event.Account == nil {
			return nil
		}
		return w.processAccount(&event)

	default:
		// Ignore unknown event kinds
		return nil
	}
}

// processIdentity processes an identity event (handle change)
func (w *Worker) processIdentity(event *JetstreamEvent) error {
	if event.Identity == nil {
		return nil
	}

	identity := event.Identity
	// Process via shared processor (only ATCR users will be logged at Info level)
	return w.processor.ProcessIdentity(context.Background(), identity.DID, identity.Handle)
}

// processAccount processes an account event (status change)
func (w *Worker) processAccount(event *JetstreamEvent) error {
	if event.Account == nil {
		return nil
	}

	account := event.Account
	// Process via shared processor (only ATCR users will be logged at Info level)
	return w.processor.ProcessAccount(context.Background(), account.DID, account.Active, account.Status)
}

// BlueskyProfileCollection is the collection for Bluesky actor profiles
const BlueskyProfileCollection = "app.bsky.actor.profile"

// isRelevantCollection returns true if the collection is one we process
func isRelevantCollection(collection string) bool {
	switch collection {
	case atproto.ManifestCollection,
		atproto.TagCollection,
		atproto.StarCollection,
		atproto.RepoPageCollection,
		atproto.SailorProfileCollection,
		atproto.StatsCollection,
		atproto.CaptainCollection,
		atproto.CrewCollection,
		atproto.ScanCollection,
		BlueskyProfileCollection: // For avatar sync
		return true
	default:
		return false
	}
}

// JetstreamEvent represents a Jetstream event
type JetstreamEvent struct {
	DID      string        `json:"did"`
	TimeUS   int64         `json:"time_us"`
	Kind     string        `json:"kind"` // "commit", "identity", "account"
	Commit   *CommitEvent  `json:"commit,omitempty"`
	Identity *IdentityInfo `json:"identity,omitempty"`
	Account  *AccountInfo  `json:"account,omitempty"`
}

// CommitEvent represents a commit event (create/update/delete)
type CommitEvent struct {
	Rev        string         `json:"rev"`
	Operation  string         `json:"operation"` // "create", "update", "delete"
	Collection string         `json:"collection"`
	RKey       string         `json:"rkey"`
	Record     map[string]any `json:"record,omitempty"`
	CID        string         `json:"cid,omitempty"`
	DID        string         `json:"-"` // Set from parent event
}

// IdentityInfo represents an identity event
type IdentityInfo struct {
	DID    string `json:"did"`
	Handle string `json:"handle"`
	Seq    int64  `json:"seq"`
	Time   string `json:"time"`
}

// AccountInfo represents an account status event
type AccountInfo struct {
	Active bool   `json:"active"`
	DID    string `json:"did"`
	Seq    int64  `json:"seq"`
	Time   string `json:"time"`
	Status string `json:"status,omitempty"`
}