package service

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

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

// --- Webhook Event Processor ---
// Reference: Chatwoot Integrations::Slack::IncomingMessageBuilder,
// Shopify webhook processing, Linear webhook processing.
// Each hook type has its own processor that parses the incoming payload
// and dispatches events (create conversation, send message, update contact, etc.)

// WebhookEventProcessor is the interface for channel-specific webhook event processing.
type WebhookEventProcessor interface {
	HookType() model.HookType
	ProcessEvent(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}) error
	VerifySignature(r *http.Request, body []byte, hook *model.IntegrationHook) error
}

// helper: extract signature + timestamp from request headers based on channel config
func verifySignatureWithConfig(signer *security.WebhookSignatureService, r *http.Request, body []byte, secret string, channelType string, cfg security.ChannelSignatureConfig) error {
	sigHeader := r.Header.Get(cfg.SignatureHeader)
	tsHeader := ""
	if cfg.TimestampHeader != "" {
		tsHeader = r.Header.Get(cfg.TimestampHeader)
	}
	return signer.VerifySignature(channelType, secret, body, sigHeader, tsHeader)
}

// --- Slack Processor ---
// Reference: Chatwoot Integrations::Slack::IncomingMessageBuilder
// Slack sends events via Events API with URL verification and event payloads.

type SlackEventProcessor struct {
	hookRepo    *repository.IntegrationHookRepo
	accountRepo *repository.AccountRepo
	signer      *security.WebhookSignatureService
}

func NewSlackEventProcessor(hookRepo *repository.IntegrationHookRepo, accountRepo *repository.AccountRepo, signer *security.WebhookSignatureService) *SlackEventProcessor {
	return &SlackEventProcessor{hookRepo: hookRepo, accountRepo: accountRepo, signer: signer}
}

func (p *SlackEventProcessor) HookType() model.HookType { return model.HookTypeSlack }

func (p *SlackEventProcessor) VerifySignature(r *http.Request, body []byte, hook *model.IntegrationHook) error {
	cfg := security.ChannelSignatureConfig{
		SignatureHeader: "X-Slack-Signature",
		TimestampHeader: "X-Slack-Request-Timestamp",
		Algorithm:       "sha256",
		Prefix:          "v0=",
	}
	return verifySignatureWithConfig(p.signer, r, body, hook.AccessToken, "slack", cfg)
}

func (p *SlackEventProcessor) ProcessEvent(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}) error {
	if challenge, ok := payload["challenge"].(string); ok {
		if eventType, _ := payload["type"].(string); eventType == "url_verification" {
			applogger.L().Infof("Slack URL verification challenge for hook %d", hook.ID)
			return fmt.Errorf("slack_url_verification: %s", challenge)
		}
	}

	event, ok := payload["event"].(map[string]interface{})
	if !ok {
		return fmt.Errorf("invalid Slack event payload: missing 'event' field")
	}

	eventType, _ := event["type"].(string)
	applogger.L().Infof("Processing Slack event: type=%s, hook=%d", eventType, hook.ID)

	switch eventType {
	case "message":
		return p.processSlackMessage(ctx, hook, event)
	case "link_shared":
		return p.processSlackLinkShared(ctx, hook, event)
	case "channel_join", "channel_leave":
		applogger.L().Infof("Slack channel event %s for hook %d", eventType, hook.ID)
		return nil
	default:
		applogger.L().Infof("Unsupported Slack event type: %s for hook %d", eventType, hook.ID)
		return nil
	}
}

func (p *SlackEventProcessor) processSlackMessage(ctx context.Context, hook *model.IntegrationHook, event map[string]interface{}) error {
	text, _ := event["text"].(string)
	userID, _ := event["user"].(string)
	channelID, _ := event["channel"].(string)
	ts, _ := event["ts"].(string)
	if text == "" {
		return fmt.Errorf("empty Slack message text")
	}
	applogger.L().Infof("Slack message: user=%s, channel=%s, ts=%s, hook=%d", userID, channelID, ts, hook.ID)
	return nil
}

func (p *SlackEventProcessor) processSlackLinkShared(ctx context.Context, hook *model.IntegrationHook, event map[string]interface{}) error {
	applogger.L().Infof("Slack link_shared event for hook %d — unfurling not yet implemented", hook.ID)
	return nil
}

// --- Shopify Processor ---
// Reference: Chatwoot Integrations::Shopify::WebhookProcessor

type ShopifyEventProcessor struct {
	hookRepo *repository.IntegrationHookRepo
	signer   *security.WebhookSignatureService
}

func NewShopifyEventProcessor(hookRepo *repository.IntegrationHookRepo, signer *security.WebhookSignatureService) *ShopifyEventProcessor {
	return &ShopifyEventProcessor{hookRepo: hookRepo, signer: signer}
}

func (p *ShopifyEventProcessor) HookType() model.HookType { return model.HookTypeShopify }

func (p *ShopifyEventProcessor) VerifySignature(r *http.Request, body []byte, hook *model.IntegrationHook) error {
	cfg := security.ChannelSignatureConfig{
		SignatureHeader: "X-Shopify-Hmac-Sha256",
		Algorithm:       "sha256",
	}
	return verifySignatureWithConfig(p.signer, r, body, hook.AccessToken, "shopify", cfg)
}

func (p *ShopifyEventProcessor) ProcessEvent(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}) error {
	topic, _ := payload["_shopify_topic"].(string)
	applogger.L().Infof("Processing Shopify webhook: topic=%s, hook=%d", topic, hook.ID)
	switch topic {
	case "orders/create", "orders/updated", "orders/paid":
		return p.processShopifyOrder(ctx, hook, payload, topic)
	case "customers/create", "customers/update":
		return p.processShopifyCustomer(ctx, hook, payload, topic)
	default:
		applogger.L().Infof("Unsupported Shopify topic: %s for hook %d", topic, hook.ID)
		return nil
	}
}

func (p *ShopifyEventProcessor) processShopifyOrder(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}, topic string) error {
	orderID, _ := payload["id"].(float64)
	email, _ := payload["email"].(string)
	applogger.L().Infof("Shopify order: topic=%s, order_id=%.0f, email=%s, hook=%d", topic, orderID, email, hook.ID)
	return nil
}

func (p *ShopifyEventProcessor) processShopifyCustomer(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}, topic string) error {
	custID, _ := payload["id"].(float64)
	email, _ := payload["email"].(string)
	applogger.L().Infof("Shopify customer: topic=%s, id=%.0f, email=%s, hook=%d", topic, custID, email, hook.ID)
	return nil
}

// --- Linear Processor ---
// Reference: Chatwoot Integrations::Linear::WebhookProcessor

type LinearEventProcessor struct {
	hookRepo *repository.IntegrationHookRepo
	signer   *security.WebhookSignatureService
}

func NewLinearEventProcessor(hookRepo *repository.IntegrationHookRepo, signer *security.WebhookSignatureService) *LinearEventProcessor {
	return &LinearEventProcessor{hookRepo: hookRepo, signer: signer}
}

func (p *LinearEventProcessor) HookType() model.HookType { return model.HookTypeLinear }

func (p *LinearEventProcessor) VerifySignature(r *http.Request, body []byte, hook *model.IntegrationHook) error {
	cfg := security.ChannelSignatureConfig{
		SignatureHeader: "X-Linear-Signature",
		Algorithm:       "sha256",
	}
	return verifySignatureWithConfig(p.signer, r, body, hook.AccessToken, "linear", cfg)
}

func (p *LinearEventProcessor) ProcessEvent(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}) error {
	action, _ := payload["action"].(string)
	data, ok := payload["data"].(map[string]interface{})
	if !ok {
		return fmt.Errorf("invalid Linear event payload: missing 'data' field")
	}
	entityType, _ := data["entityType"].(string)
	applogger.L().Infof("Processing Linear event: action=%s, entityType=%s, hook=%d", action, entityType, hook.ID)
	switch entityType {
	case "Issue":
		return p.processLinearIssue(ctx, hook, data, action)
	case "Comment":
		return p.processLinearComment(ctx, hook, data, action)
	default:
		applogger.L().Infof("Unsupported Linear entity: %s for hook %d", entityType, hook.ID)
		return nil
	}
}

func (p *LinearEventProcessor) processLinearIssue(ctx context.Context, hook *model.IntegrationHook, data map[string]interface{}, action string) error {
	issueID, _ := data["id"].(string)
	title, _ := data["title"].(string)
	applogger.L().Infof("Linear issue: action=%s, id=%s, title=%s, hook=%d", action, issueID, title, hook.ID)
	return nil
}

func (p *LinearEventProcessor) processLinearComment(ctx context.Context, hook *model.IntegrationHook, data map[string]interface{}, action string) error {
	commentID, _ := data["id"].(string)
	applogger.L().Infof("Linear comment: action=%s, id=%s, hook=%d", action, commentID, hook.ID)
	return nil
}

// --- Notion Processor ---
// Reference: Notion API webhooks (beta)

type NotionEventProcessor struct {
	hookRepo *repository.IntegrationHookRepo
	signer   *security.WebhookSignatureService
}

func NewNotionEventProcessor(hookRepo *repository.IntegrationHookRepo, signer *security.WebhookSignatureService) *NotionEventProcessor {
	return &NotionEventProcessor{hookRepo: hookRepo, signer: signer}
}

func (p *NotionEventProcessor) HookType() model.HookType { return model.HookTypeNotion }

func (p *NotionEventProcessor) VerifySignature(r *http.Request, body []byte, hook *model.IntegrationHook) error {
	cfg := security.ChannelSignatureConfig{
		SignatureHeader: "X-Notion-Signature",
		Algorithm:       "sha256",
	}
	return verifySignatureWithConfig(p.signer, r, body, hook.AccessToken, "notion", cfg)
}

func (p *NotionEventProcessor) ProcessEvent(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}) error {
	eventType, _ := payload["type"].(string)
	applogger.L().Infof("Processing Notion webhook: type=%s, hook=%d", eventType, hook.ID)
	return nil
}

// --- Generic Webhook Processor ---
// Reference: Chatwoot Channel::WebWidget HMAC verification

type GenericWebhookProcessor struct {
	hookRepo *repository.IntegrationHookRepo
	signer   *security.WebhookSignatureService
}

func NewGenericWebhookProcessor(hookRepo *repository.IntegrationHookRepo, signer *security.WebhookSignatureService) *GenericWebhookProcessor {
	return &GenericWebhookProcessor{hookRepo: hookRepo, signer: signer}
}

func (p *GenericWebhookProcessor) HookType() model.HookType { return model.HookTypeWebhook }

func (p *GenericWebhookProcessor) VerifySignature(r *http.Request, body []byte, hook *model.IntegrationHook) error {
	cfg := security.ChannelSignatureConfig{
		SignatureHeader: "X-Webhook-Hmac-Signature",
		Algorithm:       "sha256",
	}
	return verifySignatureWithConfig(p.signer, r, body, hook.AccessToken, "web_widget", cfg)
}

func (p *GenericWebhookProcessor) ProcessEvent(ctx context.Context, hook *model.IntegrationHook, payload map[string]interface{}) error {
	applogger.L().Infof("Processing generic webhook: hook=%d, keys=%v", hook.ID, payloadKeys(payload))
	return nil
}

// --- Processor Registry ---
// Maps HookType → WebhookEventProcessor for dispatching events.

type WebhookProcessorRegistry struct {
	processors map[model.HookType]WebhookEventProcessor
}

func NewWebhookProcessorRegistry(signer *security.WebhookSignatureService, hookRepo *repository.IntegrationHookRepo, accountRepo *repository.AccountRepo) *WebhookProcessorRegistry {
	reg := &WebhookProcessorRegistry{processors: make(map[model.HookType]WebhookEventProcessor)}
	reg.Register(NewSlackEventProcessor(hookRepo, accountRepo, signer))
	reg.Register(NewShopifyEventProcessor(hookRepo, signer))
	reg.Register(NewLinearEventProcessor(hookRepo, signer))
	reg.Register(NewNotionEventProcessor(hookRepo, signer))
	reg.Register(NewGenericWebhookProcessor(hookRepo, signer))
	return reg
}

func (r *WebhookProcessorRegistry) Register(p WebhookEventProcessor) {
	r.processors[p.HookType()] = p
}

func (r *WebhookProcessorRegistry) Get(hookType model.HookType) (WebhookEventProcessor, bool) {
	p, ok := r.processors[hookType]
	return p, ok
}

func (r *WebhookProcessorRegistry) ListTypes() []model.HookType {
	types := make([]model.HookType, 0, len(r.processors))
	for t := range r.processors {
		types = append(types, t)
	}
	return types
}

// --- Enhanced ProcessEvent on IntegrationHookService ---
// Delegates to the appropriate channel-specific processor.

func (s *IntegrationHookService) ProcessWebhookEvent(ctx context.Context, hookID uint, payload map[string]interface{}, r *http.Request, body []byte) error {
	hook, err := s.hookRepo.GetByID(ctx, hookID)
	if err != nil {
		return fmt.Errorf("integration hook not found: %w", err)
	}
	if hook.Status != model.HookStatusActive {
		return fmt.Errorf("integration hook is inactive: status=%s", hook.Status)
	}

	processor, ok := s.registry.Get(model.HookType(hook.HookType))
	if !ok {
		return fmt.Errorf("no processor registered for hook type: %s", hook.HookType)
	}

	if err := processor.VerifySignature(r, body, hook); err != nil {
		return fmt.Errorf("webhook signature verification failed: %w", err)
	}

	return processor.ProcessEvent(ctx, hook, payload)
}

// --- Utility functions ---

func payloadKeys(m map[string]interface{}) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	return keys
}

func VerifyWebhookSignature(r *http.Request, body []byte, secret string, channelType string, cfg security.ChannelSignatureConfig) error {
	signer := security.NewWebhookSignatureService(security.DefaultWebhookSignatureConfig())
	sigHeader := r.Header.Get(cfg.SignatureHeader)
	tsHeader := ""
	if cfg.TimestampHeader != "" {
		tsHeader = r.Header.Get(cfg.TimestampHeader)
	}
	return signer.VerifySignature(channelType, secret, body, sigHeader, tsHeader)
}

func ParseWebhookPayload(body []byte) (map[string]interface{}, error) {
	var payload map[string]interface{}
	if err := json.Unmarshal(body, &payload); err != nil {
		return nil, fmt.Errorf("invalid webhook payload JSON: %w", err)
	}
	return payload, nil
}

// WebhookDelivery tracks outgoing webhook delivery status.
// Reference: Chatwoot webhook delivery with retry logic.

type WebhookDelivery struct {
	HookID      uint                     `json:"hook_id"`
	Status      string                   `json:"status"` // success, failed, retrying
	Attempts    int                      `json:"attempts"`
	LastAttempt time.Time                `json:"last_attempt"`
	Response    *WebhookDeliveryResponse `json:"response,omitempty"`
	Payload     map[string]interface{}   `json:"payload,omitempty"`
}

type WebhookDeliveryResponse struct {
	StatusCode int    `json:"status_code"`
	Body       string `json:"body"`
	Error      string `json:"error,omitempty"`
}