package channel

import (
	"net/http"

	"github.com/gin-gonic/gin"

	"github.com/gochat/gochat/internal/model"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// WebhookHandler provides unified webhook callback entry point for all channels.
// Reference: P2D §6 — all external channel callbacks route through /webhooks/{channel_type}/{identifier}
// Corresponds to Chatwoot's per-channel WebhooksController (Telegram, Facebook, WhatsApp etc.)
//
// Updated to use MessageBroker + Dispatcher instead of calling ChannelProvider directly.
// The flow is now: webhook → WebhookHandler → MessageBroker.HandleIncoming →
//   IncomingMessageProcessor pipeline → Dispatcher.Dispatch (events to listeners)
type WebhookHandler struct {
	inboxRepo  InboxRepository
	broker     Broker
	dispatcher *Dispatcher
}

// InboxRepository abstracts inbox lookup for webhook processing.
type InboxRepository interface {
	FindByChannelTypeAndIdentifier(channelType string, identifier string) (*model.Inbox, error)
	FindByID(id uint) (*model.Inbox, error)
}

// NewWebhookHandler creates a new webhook handler with the given dependencies.
// broker routes the message through the appropriate ChannelProvider's pipeline.
// dispatcher broadcasts events (message.created, conversation.created, etc.) to registered listeners.
func NewWebhookHandler(inboxRepo InboxRepository, broker Broker, dispatcher *Dispatcher) *WebhookHandler {
	return &WebhookHandler{
		inboxRepo:  inboxRepo,
		broker:     broker,
		dispatcher: dispatcher,
	}
}

// RegisterRoutes registers webhook routes on the given router group.
// Pattern: /webhooks/{channel_type}/{identifier}
// Example: /webhooks/telegram/123456:ABC-DEF  (bot_token as identifier)
// Example: /webhooks/facebook/123456789        (page_id as identifier)
// The router group may have middleware applied (e.g. WebhookAuth for token-based verification).
func (h *WebhookHandler) RegisterRoutes(g *gin.RouterGroup) {
	g.POST("/:channel_type/:identifier", h.HandleWebhook)
	g.GET("/:channel_type/:identifier", h.HandleWebhookVerification) // for FB/WhatsApp verification
}

// HandleWebhook is the unified POST webhook callback handler.
// Flow:
//   1. Parse channel_type + identifier from URL params
//   2. Look up the Inbox via InboxRepository
//   3. Extract raw request body + headers + query params
//   4. Find the ChannelProvider via registry and validate webhook authenticity
//   5. Parse the raw body into an IncomingMessage via the provider
//   6. Route through MessageBroker.HandleIncoming (pipeline: validate → resolve → persist)
//   7. Dispatch events via Dispatcher (webhook, notification, status listeners)
func (h *WebhookHandler) HandleWebhook(c *gin.Context) {
	channelType := ChannelType(c.Param("channel_type"))
	identifier := c.Param("identifier")

	// Check if channel provider is registered
	provider, err := Get(channelType)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "unsupported channel type"})
		return
	}

	// Find inbox by channel type and identifier
	inbox, err := h.inboxRepo.FindByChannelTypeAndIdentifier(string(channelType), identifier)
	if err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": "inbox not found"})
		return
	}

	// Build WebhookRequest for provider validation
	body, _ := c.GetRawData()
	headers := make(map[string]string)
	for k, v := range c.Request.Header {
		if len(v) > 0 {
			headers[k] = v[0]
		}
	}
	queryParams := make(map[string]string)
	for k, v := range c.Request.URL.Query() {
		if len(v) > 0 {
			queryParams[k] = v[0]
		}
	}

	webhookReq := &WebhookRequest{
		ChannelType:  channelType,
		Identifier:   identifier,
		Headers:      headers,
		Body:         body,
		QueryParams:  queryParams,
		Method:       c.Request.Method,
	}

	// Validate webhook request authenticity (signature verification)
	if err := provider.ValidateWebhookRequest(c.Request.Context(), inbox, webhookReq); err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "webhook validation failed"})
		return
	}

	// Parse the raw webhook body into an IncomingMessage via the provider
	incomingMsg, err := provider.ProcessIncoming(c.Request.Context(), inbox, body)
	if err != nil {
		applogger.L().Errorf("provider.ProcessIncoming failed: channel=%s inbox=%d err=%v", channelType, inbox.ID, err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to parse incoming message"})
		return
	}

	// Acknowledge to external channel immediately (before pipeline processing)
	// This prevents webhook timeouts for channels that require fast response (e.g. Telegram)
	c.JSON(http.StatusOK, gin.H{
		"status":        "received",
		"channel_type":  channelType,
		"inbox_id":      inbox.ID,
		"account_id":    inbox.AccountID,
	})

	// Route through MessageBroker → IncomingMessageProcessor pipeline
	// Pipeline stages: ValidateConfig → ResolveContact → ResolveConversation → PersistMessage → PublishEvent
	if err := h.broker.HandleIncoming(c.Request.Context(), inbox, incomingMsg); err != nil {
		applogger.L().Errorf("broker.HandleIncoming failed: channel=%s inbox=%d err=%v", channelType, inbox.ID, err)
		// Already responded 200 to the channel — log the error for investigation
		return
	}

	// Dispatch events to all registered listeners
	// Listeners: WebhookListener (forward to external integrations),
	//   NotificationListener (push to agents), ChannelStatusListener (track channel health)
	event := &ChannelEvent{
		Type:      EventMessageCreated,
		Channel:   channelType,
		InboxID:   inbox.ID,
		AccountID: inbox.AccountID,
		Timestamp: incomingMsg.ReceivedAt.Unix(),
		Data: map[string]interface{}{
			"inbox":          inbox,
			"incoming_msg":   incomingMsg,
			"channel_type":   string(channelType),
			"source_id":      incomingMsg.SourceID,
		},
	}
	if err := h.dispatcher.Dispatch(c.Request.Context(), event); err != nil {
		applogger.L().Errorf("dispatcher.Dispatch failed: event=%s inbox=%d err=%v", event.Type, inbox.ID, err)
	}
}

// HandleWebhookVerification handles GET requests for webhook verification.
// Used by Facebook/WhatsApp webhook verification (challenge-response).
// This method does NOT use the broker/dispatcher — verification is a direct provider interaction.
func (h *WebhookHandler) HandleWebhookVerification(c *gin.Context) {
	channelType := ChannelType(c.Param("channel_type"))
	identifier := c.Param("identifier")

	provider, err := Get(channelType)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "unsupported channel type"})
		return
	}

	// Some channels (Facebook, WhatsApp) require GET verification
	// The provider handles this via ValidateWebhookRequest for GET method
	inbox, err := h.inboxRepo.FindByChannelTypeAndIdentifier(string(channelType), identifier)
	if err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": "inbox not found"})
		return
	}

	headers := make(map[string]string)
	for k, v := range c.Request.Header {
		if len(v) > 0 {
			headers[k] = v[0]
		}
	}
	queryParams := make(map[string]string)
	for k, v := range c.Request.URL.Query() {
		if len(v) > 0 {
			queryParams[k] = v[0]
		}
	}

	webhookReq := &WebhookRequest{
		ChannelType:  channelType,
		Identifier:   identifier,
		Headers:      headers,
		Body:         nil, // GET requests have no body
		QueryParams:  queryParams,
		Method:       c.Request.Method,
	}

	// Provider handles verification challenge (e.g. Facebook hub.mode=subscribe, hub.challenge)
	if err := provider.ValidateWebhookRequest(c.Request.Context(), inbox, webhookReq); err != nil {
		c.JSON(http.StatusForbidden, gin.H{"error": "verification failed"})
		return
	}

	// If ValidateWebhookRequest succeeded, the provider may have set a challenge response
	// in the webhookReq. Return 200 OK to confirm verification.
	c.JSON(http.StatusOK, gin.H{"status": "verified", "channel_type": channelType})
}