// Package ws provides typing indicator management via Redis.
// Mirrors Chatwoot's typing indicator pattern: short-lived events
// published to Redis Pub/Sub with TTL-based auto-expiry.
package ws

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"github.com/redis/go-redis/v9"

	"github.com/gochat/gochat/pkg/logger"
)

// TypingTracker manages typing indicators for conversations.
// Uses Redis for cross-instance visibility and TTL for auto-expiry.
//
// Reference: Chatwoot publishes typing_on/typing_off events via
// ActionCable, which are broadcast to all agents viewing that conversation.
// The Go implementation uses Redis keys with TTL so typing indicators
// automatically expire after TypingTTLSec seconds.
type TypingTracker struct {
	rdb    *redis.Client
	relay  *BroadcastRelay
}

// NewTypingTracker creates a new typing tracker with Redis client and broadcast relay.
func NewTypingTracker(rdb *redis.Client, relay *BroadcastRelay) *TypingTracker {
	return &TypingTracker{
		rdb:   rdb,
		relay: relay,
	}
}

// SetTypingOn marks a user/contact as typing in a conversation and broadcasts
// the typing_on event to all clients viewing that conversation.
//
// Reference: Chatwoot ConversationTypingOnJob — sets a Redis key with TTL
// and broadcasts the event to the account and conversation rooms.
func (t *TypingTracker) SetTypingOn(ctx context.Context, accountID, conversationID uint, performer *Performer) error {
	key := fmt.Sprintf(RedisKeyTyping, accountID, conversationID)

	// Store typing state in Redis with TTL (auto-expiry)
	typingData := &typingState{
		AccountID:      accountID,
		ConversationID: conversationID,
		Performer:      performer,
		StartedAt:      time.Now().Unix(),
	}

	data, err := json.Marshal(typingData)
	if err != nil {
		return fmt.Errorf("failed to marshal typing state: %w", err)
	}

	ttl := time.Duration(TypingTTLSec) * time.Second
	if err := t.rdb.Set(ctx, key, data, ttl).Err(); err != nil {
		return fmt.Errorf("failed to set typing key %s: %w", key, err)
	}

	// Broadcast typing_on event to the account and conversation rooms
	msg := &WSMessage{
		Event:     EventConversationTypingOn,
		Data:      map[string]any{
			"conversation_id": conversationID,
		},
		AccountID: accountID,
		Performer: performer,
	}

	// Publish to Redis for cross-instance relay
	if err := t.relay.PublishAccount(ctx, accountID, msg); err != nil {
		logger.L().Warnf("ws typing: failed to broadcast typing_on: %v", err)
	}

	logger.L().Debugf("ws typing: typing_on set for account=%d conversation=%d user=%d",
		accountID, conversationID, performer.ID)
	return nil
}

// SetTypingOff removes a typing indicator and broadcasts the typing_off event.
//
// Reference: Chatwoot ConversationTypingOffJob — removes Redis key
// and broadcasts typing_off to the account and conversation rooms.
func (t *TypingTracker) SetTypingOff(ctx context.Context, accountID, conversationID uint, performer *Performer) error {
	key := fmt.Sprintf(RedisKeyTyping, accountID, conversationID)

	// Remove typing state from Redis
	if err := t.rdb.Del(ctx, key).Err(); err != nil {
		return fmt.Errorf("failed to delete typing key %s: %w", key, err)
	}

	// Broadcast typing_off event
	msg := &WSMessage{
		Event:     EventConversationTypingOff,
		Data:      map[string]any{
			"conversation_id": conversationID,
		},
		AccountID: accountID,
		Performer: performer,
	}

	if err := t.relay.PublishAccount(ctx, accountID, msg); err != nil {
		logger.L().Warnf("ws typing: failed to broadcast typing_off: %v", err)
	}

	logger.L().Debugf("ws typing: typing_off set for account=%d conversation=%d user=%d",
		accountID, conversationID, performer.ID)
	return nil
}

// IsTyping checks whether a typing indicator is currently active for a conversation.
func (t *TypingTracker) IsTyping(ctx context.Context, accountID, conversationID uint) (bool, error) {
	key := fmt.Sprintf(RedisKeyTyping, accountID, conversationID)
	result, err := t.rdb.Exists(ctx, key).Result()
	if err != nil {
		return false, fmt.Errorf("failed to check typing key %s: %w", key, err)
	}
	return result > 0, nil
}

// GetTypingState retrieves the full typing state for a conversation.
// Returns nil if no typing indicator is active.
func (t *TypingTracker) GetTypingState(ctx context.Context, accountID, conversationID uint) (*typingState, error) {
	key := fmt.Sprintf(RedisKeyTyping, accountID, conversationID)
	data, err := t.rdb.Get(ctx, key).Bytes()
	if err != nil {
		if err == redis.Nil {
			return nil, nil // no active typing
		}
		return nil, fmt.Errorf("failed to get typing state for key %s: %w", key, err)
	}

	var state typingState
	if err := json.Unmarshal(data, &state); err != nil {
		return nil, fmt.Errorf("failed to unmarshal typing state: %w", err)
	}
	return &state, nil
}

// typingState represents the persisted typing indicator data stored in Redis.
type typingState struct {
	AccountID      uint      `json:"account_id"`
	ConversationID uint      `json:"conversation_id"`
	Performer      *Performer `json:"performer"`
	StartedAt      int64     `json:"started_at"`
}