package webhook

// TikTok Gin webhook adapter — bridges HTTP requests from the Gin router
// to the TikTok channel package's WebhookHandler and IncomingProcessor.
// Reference: Facebook webhook adapter pattern (facebook_webhook.go)

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/gochat/gochat/internal/channel"
	tiktokchannel "github.com/gochat/gochat/internal/channel/tiktok"
	"github.com/gochat/gochat/internal/model"
	channelmodel "github.com/gochat/gochat/internal/model/channel"
	applogger "github.com/gochat/gochat/pkg/logger"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

// TikTokWebhookHandler adapts TikTok webhook handling to Gin HTTP requests.
type TikTokWebhookHandler struct {
	tiktokWebhook *tiktokchannel.WebhookHandler
	pipeline      *tiktokchannel.IncomingProcessor
	db            *gorm.DB
	persister     *IncomingPersister
}

// NewTikTokWebhookHandler creates a Gin-compatible TikTok webhook handler.
func NewTikTokWebhookHandler(tiktokWebhook *tiktokchannel.WebhookHandler, pipeline *tiktokchannel.IncomingProcessor, db *gorm.DB, dispatcher ...*channel.Dispatcher) *TikTokWebhookHandler {
	return &TikTokWebhookHandler{
		tiktokWebhook: tiktokWebhook,
		pipeline:      pipeline,
		db:            db,
		persister:     NewIncomingPersister(db, dispatcher...),
	}
}

// HandleTikTokWebhook processes incoming TikTok webhook HTTP requests.
func (h *TikTokWebhookHandler) HandleTikTokWebhook(c *gin.Context) {
	body, err := io.ReadAll(c.Request.Body)
	if err != nil {
		applogger.L().Errorf("TikTok webhook: failed to read body: %v", err)
		c.JSON(http.StatusOK, gin.H{"status": "ignored"})
		return
	}
	c.Request.Body.Close()
	c.Request.Body = io.NopCloser(bytes.NewReader(body))

	if err := verifyTikTokSignature(c.GetHeader("Tiktok-Signature"), body, time.Now()); err != nil {
		applogger.L().Warnf("TikTok webhook: signature verification failed: %v", err)
		c.JSON(http.StatusUnauthorized, gin.H{"error": "signature verification failed"})
		return
	}

	businessID := c.Param("business_id")
	if businessID == "" {
		businessID = extractTikTokBusinessID(body)
	}
	if businessID == "" {
		applogger.L().Warn("TikTok webhook: missing business_id in path and payload")
		c.JSON(http.StatusOK, gin.H{"status": "ignored"})
		return
	}

	// Lookup inbox from database
	inbox, err := h.lookupInboxByBusinessID(businessID)
	if err != nil {
		applogger.L().Warnf("TikTok webhook: inbox lookup failed for business_id %s: %v", businessID, err)
		c.JSON(http.StatusOK, gin.H{"status": "ignored"})
		return
	}

	// Parse the webhook event using the channel-level handler
	event, err := h.tiktokWebhook.HandleWebhookRequest(c.Request)
	if err != nil {
		applogger.L().Errorf("TikTok webhook: parse request failed for inbox %d: %v", inbox.ID, err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request"})
		return
	}

	// Process the event via the pipeline
	incomingMsg, err := h.pipeline.ProcessUpdate(c.Request.Context(), inbox, *event)
	if err != nil {
		applogger.L().Errorf("TikTok webhook: process event failed for inbox %d: %v", inbox.ID, err)
		c.JSON(http.StatusOK, gin.H{"status": "ignored"})
		return
	}
	if incomingMsg != nil {
		if _, persistErr := h.persister.PersistIncoming(c.Request.Context(), inbox, incomingMsg); persistErr != nil {
			applogger.L().Errorf("TikTok webhook: persist event failed for inbox %d source_id=%s: %v", inbox.ID, incomingMsg.SourceID, persistErr)
		}
	} else if event.Type == "message.read" {
		if messageID := tiktokDataString(event.Data, "message_id"); messageID != "" {
			if err := h.persister.UpdateMessageStatus(c.Request.Context(), inbox, messageID, model.MessageStatusRead, nil); err != nil {
				applogger.L().Errorf("TikTok webhook: read status persistence failed for inbox %d source_id=%s: %v", inbox.ID, messageID, err)
			}
		}
	}

	c.JSON(http.StatusOK, gin.H{"status": "processed"})
}

// HandleTikTokVerification handles TikTok webhook verification (challenge-response).
func (h *TikTokWebhookHandler) HandleTikTokVerification(c *gin.Context) {
	body, err := io.ReadAll(c.Request.Body)
	if err != nil {
		c.JSON(http.StatusUnprocessableEntity, gin.H{"error": "failed to read body"})
		return
	}
	defer c.Request.Body.Close()

	// Parse verification challenge
	var verifyReq map[string]interface{}
	if err := json.Unmarshal(body, &verifyReq); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid JSON"})
		return
	}

	challenge, _ := verifyReq["challenge"].(string)
	applogger.L().Infof("TikTok webhook verification: business_id=%s challenge=%s", c.Param("business_id"), challenge)

	c.JSON(http.StatusOK, gin.H{"challenge": challenge})
}

// lookupInbox fetches an Inbox record from the database.
func (h *TikTokWebhookHandler) lookupInbox(inboxID uint) (*model.Inbox, error) {
	var inbox model.Inbox
	if err := h.db.Where("id = ?", inboxID).First(&inbox).Error; err != nil {
		return nil, err
	}
	return &inbox, nil
}

// lookupInboxByBusinessID fetches an Inbox through the TikTok channel record.
func (h *TikTokWebhookHandler) lookupInboxByBusinessID(businessID string) (*model.Inbox, error) {
	if h.db == nil {
		return nil, fmt.Errorf("tiktok webhook database is not configured")
	}

	var channel channelmodel.ChannelTikTok
	if err := h.db.Where("tiktok_business_id = ?", businessID).First(&channel).Error; err != nil {
		return nil, fmt.Errorf("tiktok channel not found for business_id=%s: %w", businessID, err)
	}

	var inbox model.Inbox
	if err := h.db.Where("id = ? AND channel_type = ?", channel.InboxID, "tiktok").First(&inbox).Error; err != nil {
		return nil, fmt.Errorf("tiktok inbox not found for channel inbox_id=%d: %w", channel.InboxID, err)
	}
	return &inbox, nil
}

func extractTikTokBusinessID(body []byte) string {
	var payload struct {
		BizID            string `json:"biz_id"`
		BusinessID       string `json:"business_id"`
		TikTokBusinessID string `json:"tiktok_business_id"`
		Data             struct {
			BizID            string `json:"biz_id"`
			BusinessID       string `json:"business_id"`
			TikTokBusinessID string `json:"tiktok_business_id"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &payload); err != nil {
		return ""
	}
	for _, candidate := range []string{
		payload.BizID,
		payload.BusinessID,
		payload.TikTokBusinessID,
		payload.Data.BizID,
		payload.Data.BusinessID,
		payload.Data.TikTokBusinessID,
	} {
		if candidate != "" {
			return candidate
		}
	}
	return ""
}

func verifyTikTokSignature(signatureHeader string, body []byte, now time.Time) error {
	clientSecret := os.Getenv("TIKTOK_APP_SECRET")
	timestamp, signature := extractTikTokSignatureParts(signatureHeader)
	if clientSecret == "" || timestamp == 0 || signature == "" {
		return fmt.Errorf("missing tiktok signature credentials")
	}

	payload := fmt.Sprintf("%d.%s", timestamp, string(body))
	mac := hmac.New(sha256.New, []byte(clientSecret))
	mac.Write([]byte(payload))
	expected := hex.EncodeToString(mac.Sum(nil))
	if !hmac.Equal([]byte(expected), []byte(signature)) {
		return fmt.Errorf("invalid tiktok signature")
	}
	if now.Unix()-timestamp > 5 {
		return fmt.Errorf("stale tiktok signature")
	}
	return nil
}

func extractTikTokSignatureParts(signatureHeader string) (int64, string) {
	if signatureHeader == "" {
		return 0, ""
	}
	var timestamp int64
	var signature string
	for _, part := range strings.Split(signatureHeader, ",") {
		keyValue := strings.SplitN(strings.TrimSpace(part), "=", 2)
		if len(keyValue) != 2 {
			continue
		}
		switch keyValue[0] {
		case "t":
			parsed, err := strconv.ParseInt(keyValue[1], 10, 64)
			if err == nil {
				timestamp = parsed
			}
		case "s":
			signature = keyValue[1]
		}
	}
	return timestamp, signature
}

func tiktokDataString(data map[string]interface{}, key string) string {
	if value, ok := data[key].(string); ok {
		return value
	}
	return ""
}

// parseChannelConfig parses the JSON-encoded ChannelConfig string into a map.
func (h *TikTokWebhookHandler) parseChannelConfig(inbox *model.Inbox) map[string]interface{} {
	if inbox.ChannelConfig == "" {
		return map[string]interface{}{}
	}
	var config map[string]interface{}
	if err := json.Unmarshal([]byte(inbox.ChannelConfig), &config); err != nil {
		applogger.L().Warnf("TikTok: Failed to parse ChannelConfig for inbox %d: %v", inbox.ID, err)
		return map[string]interface{}{}
	}
	return config
}