package channel

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

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

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/pubsub"
)

// --- ChannelStatus enum ---
// Reference: P2D §3.2 — tracks per-inbox channel connection state
// Chatwoot tracks channel reauthorization status; GoChat extends this to full lifecycle tracking.

// ChannelStatus represents the connection status of a channel inbox.
type ChannelStatus string

const (
	ChannelStatusConnected    ChannelStatus = "connected"
	ChannelStatusDisconnected ChannelStatus = "disconnected"
	ChannelStatusError        ChannelStatus = "error"
	ChannelStatusReconnecting ChannelStatus = "reconnecting"
	ChannelStatusPending      ChannelStatus = "pending"
)

// --- StatusTracker: tracks per-inbox connection status in memory ---
// Used for monitoring dashboards and health checks.

// StatusTracker tracks per-inbox channel connection status in memory.
type StatusTracker struct {
	mu     sync.RWMutex
	status map[uint]ChannelStatus
}

// NewStatusTracker creates a new StatusTracker.
func NewStatusTracker() *StatusTracker {
	return &StatusTracker{
		status: make(map[uint]ChannelStatus),
	}
}

// Set updates the connection status for an inbox.
func (st *StatusTracker) Set(inboxID uint, status ChannelStatus) {
	st.mu.Lock()
	defer st.mu.Unlock()
	st.status[inboxID] = status
}

// Get retrieves the connection status for an inbox.
// Returns ChannelStatusPending if the inbox has no recorded status.
func (st *StatusTracker) Get(inboxID uint) ChannelStatus {
	st.mu.RLock()
	defer st.mu.RUnlock()
	if s, ok := st.status[inboxID]; ok {
		return s
	}
	return ChannelStatusPending
}

// GetAll returns a snapshot of all tracked inbox statuses.
func (st *StatusTracker) GetAll() map[uint]ChannelStatus {
	st.mu.RLock()
	defer st.mu.RUnlock()
	result := make(map[uint]ChannelStatus, len(st.status))
	for k, v := range st.status {
		result[k] = v
	}
	return result
}

// Remove removes tracking for an inbox (e.g. on inbox deletion).
func (st *StatusTracker) Remove(inboxID uint) {
	st.mu.Lock()
	defer st.mu.Unlock()
	delete(st.status, inboxID)
}

// --- LifecycleManager: manages channel connect/disconnect/reconnect lifecycle ---
// Reference: P2D §3.2 — Chatwoot's channel setup/teardown + reauthorization
// Orchestrates ChannelProvider.OnCreate/OnDestroy + publishes events to EventBus.

// LifecycleManager manages the connect/disconnect/reconnect lifecycle of channel providers.
// It coordinates with the ChannelRegistry for provider lookup and the EventBus for event publishing.
type LifecycleManager struct {
	registry     *ChannelRegistry
	eventBus     *pubsub.EventBus
	statusTracker *StatusTracker
}

// NewLifecycleManager creates a new LifecycleManager.
func NewLifecycleManager(registry *ChannelRegistry, eventBus *pubsub.EventBus) *LifecycleManager {
	return &LifecycleManager{
		registry:     registry,
		eventBus:     eventBus,
		statusTracker: NewStatusTracker(),
	}
}

// ConnectInbox connects a channel inbox to its external provider.
// Calls provider.OnCreate() and publishes EventChannelConnected.
// Reference: Chatwoot's before_save :setup_*_webhook callbacks
func (lm *LifecycleManager) ConnectInbox(ctx context.Context, inbox *model.Inbox) error {
	if inbox == nil {
		return fmt.Errorf("inbox is nil")
	}

	provider, err := lm.registry.Get(ChannelType(inbox.ChannelType))
	if err != nil {
		return fmt.Errorf("failed to get provider for channel type %s: %w", inbox.ChannelType, err)
	}

	// Parse config from Inbox.ChannelConfig JSON string
	config, parseErr := parseInboxConfig(inbox.ChannelConfig)
	if parseErr != nil {
		return fmt.Errorf("failed to parse channel config for inbox %d: %w", inbox.ID, parseErr)
	}

	// Call provider's OnCreate to set up external resources (webhooks, subscriptions, etc.)
	updatedConfig, createErr := provider.OnCreate(ctx, inbox, config)
	if createErr != nil {
		lm.statusTracker.Set(inbox.ID, ChannelStatusError)
		return fmt.Errorf("provider OnCreate failed for inbox %d: %w", inbox.ID, createErr)
	}

	// If provider returned updated config, we should persist it.
	// Note: the actual DB update should be done by the caller (service layer),
	// but we serialize it here for reference.
	if updatedConfig != nil {
		configBytes, marshalErr := json.Marshal(updatedConfig)
		if marshalErr != nil {
			applogger.L().Warnf("failed to marshal updated config for inbox %d: %v", inbox.ID, marshalErr)
		} else {
			inbox.ChannelConfig = string(configBytes)
		}
	}

	// Update status
	lm.statusTracker.Set(inbox.ID, ChannelStatusConnected)

	// Publish connected event
	if lm.eventBus != nil {
		topic := pubsub.FormatTopic(pubsub.TopicChannelEvent, inbox.ChannelType)
		eventPayload, _ := json.Marshal(map[string]interface{}{
			"event_type":  string(EventChannelConnected),
			"inbox_id":    inbox.ID,
			"account_id":  inbox.AccountID,
			"channel_type": inbox.ChannelType,
		})
		if publishErr := lm.eventBus.Publish(topic, eventPayload); publishErr != nil {
			applogger.L().Warnf("failed to publish channel.connected event for inbox %d: %v", inbox.ID, publishErr)
		}
	}

	applogger.L().Infof("inbox %d (channel %s) connected successfully", inbox.ID, inbox.ChannelType)
	return nil
}

// DisconnectInbox disconnects a channel inbox from its external provider.
// Calls provider.OnDestroy() and publishes EventChannelDisconnected.
// Reference: Chatwoot's before_destroy :cleanup_*_webhook callbacks
func (lm *LifecycleManager) DisconnectInbox(ctx context.Context, inbox *model.Inbox) error {
	if inbox == nil {
		return fmt.Errorf("inbox is nil")
	}

	provider, err := lm.registry.Get(ChannelType(inbox.ChannelType))
	if err != nil {
		return fmt.Errorf("failed to get provider for channel type %s: %w", inbox.ChannelType, err)
	}

	// Parse config from Inbox.ChannelConfig JSON string
	config, parseErr := parseInboxConfig(inbox.ChannelConfig)
	if parseErr != nil {
		return fmt.Errorf("failed to parse channel config for inbox %d: %w", inbox.ID, parseErr)
	}

	// Call provider's OnDestroy to clean up external resources
	if destroyErr := provider.OnDestroy(ctx, inbox, config); destroyErr != nil {
		lm.statusTracker.Set(inbox.ID, ChannelStatusError)
		return fmt.Errorf("provider OnDestroy failed for inbox %d: %w", inbox.ID, destroyErr)
	}

	// Update status
	lm.statusTracker.Set(inbox.ID, ChannelStatusDisconnected)

	// Publish disconnected event
	if lm.eventBus != nil {
		topic := pubsub.FormatTopic(pubsub.TopicChannelEvent, inbox.ChannelType)
		eventPayload, _ := json.Marshal(map[string]interface{}{
			"event_type":   string(EventChannelDisconnected),
			"inbox_id":     inbox.ID,
			"account_id":   inbox.AccountID,
			"channel_type": inbox.ChannelType,
		})
		if publishErr := lm.eventBus.Publish(topic, eventPayload); publishErr != nil {
			applogger.L().Warnf("failed to publish channel.disconnected event for inbox %d: %v", inbox.ID, publishErr)
		}
	}

	applogger.L().Infof("inbox %d (channel %s) disconnected successfully", inbox.ID, inbox.ChannelType)
	return nil
}

// ReconnectInbox reconnects a channel inbox by disconnecting then connecting.
// Updates status to reconnecting during the transition.
// Reference: Chatwoot's channel reauthorization flow
func (lm *LifecycleManager) ReconnectInbox(ctx context.Context, inbox *model.Inbox) error {
	if inbox == nil {
		return fmt.Errorf("inbox is nil")
	}

	// Mark as reconnecting
	lm.statusTracker.Set(inbox.ID, ChannelStatusReconnecting)

	// Disconnect first
	if disconnectErr := lm.DisconnectInbox(ctx, inbox); disconnectErr != nil {
		applogger.L().Warnf("disconnect during reconnect for inbox %d failed: %v", inbox.ID, disconnectErr)
		// Continue with connect even if disconnect fails — some channels don't need clean disconnect
	}

	// Re-connect
	if connectErr := lm.ConnectInbox(ctx, inbox); connectErr != nil {
		lm.statusTracker.Set(inbox.ID, ChannelStatusError)
		return fmt.Errorf("reconnect failed for inbox %d: connect error: %w", inbox.ID, connectErr)
	}

	applogger.L().Infof("inbox %d (channel %s) reconnected successfully", inbox.ID, inbox.ChannelType)
	return nil
}

// RefreshOAuth refreshes OAuth tokens for OAuth-capable channel providers.
// Only works for channels that implement OAuthProvider.
// Reference: Chatwoot's RefreshOauthTokenService per channel
func (lm *LifecycleManager) RefreshOAuth(ctx context.Context, inbox *model.Inbox) error {
	if inbox == nil {
		return fmt.Errorf("inbox is nil")
	}

	provider, err := lm.registry.Get(ChannelType(inbox.ChannelType))
	if err != nil {
		return fmt.Errorf("failed to get provider for channel type %s: %w", inbox.ChannelType, err)
	}

	// Check if provider supports OAuth
	oauthProvider, ok := provider.(OAuthProvider)
	if !ok {
		return fmt.Errorf("channel type %s does not support OAuth refresh", inbox.ChannelType)
	}

	// Parse config from Inbox.ChannelConfig JSON string
	config, parseErr := parseInboxConfig(inbox.ChannelConfig)
	if parseErr != nil {
		return fmt.Errorf("failed to parse channel config for inbox %d: %w", inbox.ID, parseErr)
	}

	// Refresh the token
	tokenResult, refreshErr := oauthProvider.RefreshToken(ctx, inbox, config)
	if refreshErr != nil {
		lm.statusTracker.Set(inbox.ID, ChannelStatusError)
		return fmt.Errorf("OAuth token refresh failed for inbox %d: %w", inbox.ID, refreshErr)
	}

	// Update config with new token data
	config["access_token"] = tokenResult.AccessToken
	if tokenResult.RefreshToken != "" {
		config["refresh_token"] = tokenResult.RefreshToken
	}
	if !tokenResult.ExpiresAt.IsZero() {
		config["token_expires_at"] = tokenResult.ExpiresAt.Unix()
	}

	// Merge extra data from token result
	if tokenResult.Extra != nil {
		for k, v := range tokenResult.Extra {
			config[k] = v
		}
	}

	// Serialize updated config back to inbox
	configBytes, marshalErr := json.Marshal(config)
	if marshalErr != nil {
		return fmt.Errorf("failed to marshal updated config for inbox %d: %w", inbox.ID, marshalErr)
	}
	inbox.ChannelConfig = string(configBytes)

	// Publish reauthorized event
	if lm.eventBus != nil {
		topic := pubsub.FormatTopic(pubsub.TopicChannelEvent, inbox.ChannelType)
		eventPayload, _ := json.Marshal(map[string]interface{}{
			"event_type":   string(EventChannelReauthorized),
			"inbox_id":     inbox.ID,
			"account_id":   inbox.AccountID,
			"channel_type": inbox.ChannelType,
		})
		if publishErr := lm.eventBus.Publish(topic, eventPayload); publishErr != nil {
			applogger.L().Warnf("failed to publish channel.reauthorized event for inbox %d: %v", inbox.ID, publishErr)
		}
	}

	applogger.L().Infof("OAuth token refreshed for inbox %d (channel %s)", inbox.ID, inbox.ChannelType)
	return nil
}

// GetChannelStatus returns the current connection status for an inbox.
func (lm *LifecycleManager) GetChannelStatus(ctx context.Context, inbox *model.Inbox) ChannelStatus {
	if inbox == nil {
		return ChannelStatusPending
	}
	return lm.statusTracker.Get(inbox.ID)
}

// GetStatusTracker returns the underlying StatusTracker for direct access.
func (lm *LifecycleManager) GetStatusTracker() *StatusTracker {
	return lm.statusTracker
}

// --- Helper: parse Inbox.ChannelConfig JSON string into ChannelConfig map ---
// Since Inbox.ChannelConfig is stored as a JSON string (jsonb in DB), we need to parse it.

func parseInboxConfig(configJSON string) (ChannelConfig, error) {
	if configJSON == "" || configJSON == "{}" {
		return ChannelConfig{}, nil
	}

	var config ChannelConfig
	if err := json.Unmarshal([]byte(configJSON), &config); err != nil {
		return nil, fmt.Errorf("failed to unmarshal channel config JSON: %w", err)
	}
	return config, nil
}