package webhook

import (
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"

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

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

// ShopifyWebhookHandler handles Chatwoot-compatible Shopify public webhooks.
// Reference: reference/chatwoot/app/controllers/webhooks/shopify_controller.rb
type ShopifyWebhookHandler struct {
	db           *gorm.DB
	clientSecret string
}

func NewShopifyWebhookHandler(db *gorm.DB, clientSecret string) *ShopifyWebhookHandler {
	return &ShopifyWebhookHandler{db: db, clientSecret: clientSecret}
}

func (h *ShopifyWebhookHandler) HandleShopifyWebhook(c *gin.Context) {
	body, err := io.ReadAll(c.Request.Body)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "failed to read request body"})
		return
	}
	defer c.Request.Body.Close()

	if err := h.verifyHMAC(c.GetHeader("X-Shopify-Hmac-SHA256"), body); err != nil {
		applogger.L().Warnf("Shopify webhook: HMAC verification failed: %v", err)
		c.Status(http.StatusUnauthorized)
		return
	}

	var payload map[string]interface{}
	if len(body) > 0 {
		if err := json.Unmarshal(body, &payload); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid JSON payload"})
			return
		}
	} else {
		payload = map[string]interface{}{}
	}

	topic := c.GetHeader("X-Shopify-Topic")
	payload["_shopify_topic"] = topic
	shopDomain := c.GetHeader("X-Shopify-Shop-Domain")
	if shopDomain == "" {
		shopDomain, _ = payload["shop_domain"].(string)
	}

	if topic == "shop/redact" {
		if shopDomain != "" {
			if err := h.deleteShopifyHooksByDomain(c.Request.Context(), shopDomain); err != nil {
				applogger.L().Warnf("Shopify webhook: shop/redact cleanup failed for %s: %v", shopDomain, err)
			}
		}
		c.Status(http.StatusOK)
		return
	}

	if shopDomain != "" {
		if hook, err := h.findShopifyHookByDomain(c.Request.Context(), shopDomain); err == nil && hook != nil {
			processor := service.NewShopifyEventProcessor(nil, nil)
			if err := processor.ProcessEvent(c.Request.Context(), hook, payload); err != nil {
				applogger.L().Warnf("Shopify webhook: event processing failed for hook %d: %v", hook.ID, err)
			}
		}
	}

	c.Status(http.StatusOK)
}

func (h *ShopifyWebhookHandler) verifyHMAC(signature string, body []byte) error {
	secret := h.clientSecret
	if secret == "" {
		secret = os.Getenv("SHOPIFY_CLIENT_SECRET")
	}
	if secret == "" {
		return fmt.Errorf("SHOPIFY_CLIENT_SECRET is not configured")
	}
	if signature == "" {
		return fmt.Errorf("missing X-Shopify-Hmac-SHA256 header")
	}

	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(body)
	expected := base64.StdEncoding.EncodeToString(mac.Sum(nil))
	if !hmac.Equal([]byte(expected), []byte(signature)) {
		return fmt.Errorf("invalid Shopify HMAC")
	}
	return nil
}

func (h *ShopifyWebhookHandler) deleteShopifyHooksByDomain(ctx context.Context, shopDomain string) error {
	if h.db == nil {
		return fmt.Errorf("shopify webhook database is not configured")
	}

	hooks, err := h.shopifyHooks(ctx, shopDomain)
	if err != nil {
		return err
	}
	for i := range hooks {
		if err := h.db.Delete(&model.IntegrationHook{}, hooks[i].ID).Error; err != nil {
			return err
		}
	}
	return nil
}

func (h *ShopifyWebhookHandler) findShopifyHookByDomain(ctx context.Context, shopDomain string) (*model.IntegrationHook, error) {
	hooks, err := h.shopifyHooks(ctx, shopDomain)
	if err != nil || len(hooks) == 0 {
		return nil, err
	}
	return &hooks[0], nil
}

func (h *ShopifyWebhookHandler) shopifyHooks(ctx context.Context, shopDomain string) ([]model.IntegrationHook, error) {
	if h.db == nil {
		return nil, fmt.Errorf("shopify webhook database is not configured")
	}

	var hooks []model.IntegrationHook
	if err := h.db.WithContext(ctx).Where("hook_type = ?", model.HookTypeShopify).Find(&hooks).Error; err != nil {
		return nil, err
	}

	matched := make([]model.IntegrationHook, 0, len(hooks))
	for _, hook := range hooks {
		var settings model.ShopifySettings
		if len(hook.Settings) == 0 || json.Unmarshal(hook.Settings, &settings) != nil {
			continue
		}
		if settings.ShopDomain == shopDomain {
			matched = append(matched, hook)
		}
	}
	return matched, nil
}