package service

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"strings"

	"github.com/gochat/gochat/internal/model"
	channelmodel "github.com/gochat/gochat/internal/model/channel"
)

var whatsappAuthorizationHTTPClient = http.DefaultClient

type WhatsAppAuthorizationRequest struct {
	Code          string `json:"code" form:"code"`
	BusinessID    string `json:"business_id" form:"business_id"`
	WabaID        string `json:"waba_id" form:"waba_id"`
	PhoneNumberID string `json:"phone_number_id" form:"phone_number_id"`
	InboxID       *uint  `json:"inbox_id" form:"inbox_id"`
}

type WhatsAppAuthorizationResult struct {
	Inbox   *model.Inbox
	Message string
}

type whatsappPhoneInfo struct {
	PhoneNumberID string
	PhoneNumber   string
	BusinessName  string
}

// AuthorizeWhatsAppEmbeddedSignup implements Chatwoot's WhatsApp embedded signup
// callback endpoint for both new channel creation and reauthorization.
func (s *InboxService) AuthorizeWhatsAppEmbeddedSignup(ctx context.Context, accountID uint, req WhatsAppAuthorizationRequest) (*WhatsAppAuthorizationResult, error) {
	if err := validateWhatsAppAuthorizationParams(req); err != nil {
		return nil, err
	}
	if s == nil || s.repo == nil || s.whatsappRepo == nil {
		return nil, fmt.Errorf("WhatsApp authorization service is not configured")
	}
	if req.InboxID != nil && *req.InboxID > 0 {
		if _, err := s.repo.FindByAccountAndID(ctx, accountID, *req.InboxID); err != nil {
			return nil, err
		}
	}

	accessToken, err := exchangeWhatsAppAuthorizationCode(ctx, req.Code)
	if err != nil {
		return nil, err
	}
	phoneInfo, err := fetchWhatsAppPhoneInfo(ctx, req.WabaID, req.PhoneNumberID, accessToken)
	if err != nil {
		return nil, err
	}
	if err := validateWhatsAppTokenAccess(ctx, accessToken, req.WabaID); err != nil {
		return nil, err
	}

	if req.InboxID != nil && *req.InboxID > 0 {
		return s.reauthorizeWhatsAppInbox(ctx, accountID, *req.InboxID, req, accessToken, phoneInfo)
	}
	return s.createWhatsAppEmbeddedSignupInbox(ctx, accountID, req, accessToken, phoneInfo)
}

func validateWhatsAppAuthorizationParams(req WhatsAppAuthorizationRequest) error {
	missing := make([]string, 0, 3)
	if strings.TrimSpace(req.Code) == "" {
		missing = append(missing, "code")
	}
	if strings.TrimSpace(req.BusinessID) == "" {
		missing = append(missing, "business_id")
	}
	if strings.TrimSpace(req.WabaID) == "" {
		missing = append(missing, "waba_id")
	}
	if len(missing) > 0 {
		return fmt.Errorf("Required parameters are missing: %s", strings.Join(missing, ", "))
	}
	return nil
}

func (s *InboxService) createWhatsAppEmbeddedSignupInbox(ctx context.Context, accountID uint, req WhatsAppAuthorizationRequest, accessToken string, phoneInfo whatsappPhoneInfo) (*WhatsAppAuthorizationResult, error) {
	if err := s.EnsureCanCreateInbox(ctx, accountID); err != nil {
		return nil, err
	}
	var count int64
	if err := s.repo.DB().WithContext(ctx).Model(&channelmodel.ChannelWhatsApp{}).Where("phone_number = ?", phoneInfo.PhoneNumber).Count(&count).Error; err != nil {
		return nil, err
	}
	if count > 0 {
		return nil, fmt.Errorf("Channel already exists")
	}

	inboxName := strings.TrimSpace(phoneInfo.BusinessName)
	if inboxName == "" {
		inboxName = "WhatsApp"
	} else {
		inboxName += " WhatsApp"
	}
	inbox := &model.Inbox{AccountID: accountID, Name: inboxName, ChannelType: "whatsapp", Enabled: true, EnableEmailCollect: true, AllowMessagesAfterResolved: true, SenderNameType: "friendly_name", Timezone: "UTC"}
	if err := s.repo.Create(ctx, inbox); err != nil {
		return nil, err
	}

	channel := &channelmodel.ChannelWhatsApp{
		AccountID:           accountID,
		InboxID:             inbox.ID,
		PhoneNumber:         phoneInfo.PhoneNumber,
		PhoneNumberID:       firstNonEmpty(phoneInfo.PhoneNumberID, req.PhoneNumberID),
		BusinessAccountID:   req.WabaID,
		WhatsAppAccountName: phoneInfo.BusinessName,
		AccessToken:         accessToken,
		Provider:            "whatsapp_cloud",
		ProviderConfig:      marshalInboxJSON(whatsappEmbeddedProviderConfig(accessToken, firstNonEmpty(phoneInfo.PhoneNumberID, req.PhoneNumberID), req.WabaID)),
		WebhookVerifyToken:  generateInboxSecret(),
		AutoCreateContact:   true,
	}
	if err := s.whatsappRepo.Create(ctx, channel); err != nil {
		return nil, err
	}
	inbox.ChannelID = channel.ID
	inbox.ChannelConfig = marshalInboxJSON(whatsappInboxChannelConfig(channel))
	if err := s.repo.Update(ctx, inbox); err != nil {
		return nil, err
	}
	_ = s.setupWhatsAppWebhook(ctx, channel, whatsappWebhookCallbackURL(channel.PhoneNumber))
	return &WhatsAppAuthorizationResult{Inbox: inbox}, nil
}

func (s *InboxService) reauthorizeWhatsAppInbox(ctx context.Context, accountID, inboxID uint, req WhatsAppAuthorizationRequest, accessToken string, phoneInfo whatsappPhoneInfo) (*WhatsAppAuthorizationResult, error) {
	inbox, err := s.repo.FindByAccountAndID(ctx, accountID, inboxID)
	if err != nil {
		return nil, err
	}
	channel, err := s.whatsappRepo.GetByInboxID(ctx, inbox.ID)
	if err != nil || channel.Provider != "whatsapp_cloud" {
		return nil, fmt.Errorf("WhatsApp channel not found")
	}
	if phoneInfo.PhoneNumber != "" && channel.PhoneNumber != "" && phoneInfo.PhoneNumber != channel.PhoneNumber {
		return nil, fmt.Errorf("Phone number mismatch. Expected %s, got %s", channel.PhoneNumber, phoneInfo.PhoneNumber)
	}

	channel.AccessToken = accessToken
	channel.PhoneNumberID = firstNonEmpty(phoneInfo.PhoneNumberID, req.PhoneNumberID)
	channel.BusinessAccountID = req.BusinessID
	channel.ProviderConfig = marshalInboxJSON(whatsappEmbeddedProviderConfig(accessToken, channel.PhoneNumberID, req.BusinessID))
	channel.ReauthorizationRequired = false
	if phoneInfo.BusinessName != "" {
		channel.WhatsAppAccountName = phoneInfo.BusinessName
		inbox.Name = phoneInfo.BusinessName
	}
	if err := s.whatsappRepo.Update(ctx, channel); err != nil {
		return nil, err
	}
	inbox.ChannelConfig = marshalInboxJSON(whatsappInboxChannelConfig(channel))
	if err := s.repo.Update(ctx, inbox); err != nil {
		return nil, err
	}
	_ = s.setupWhatsAppWebhook(ctx, channel, whatsappWebhookCallbackURL(channel.PhoneNumber))
	return &WhatsAppAuthorizationResult{Inbox: inbox, Message: "Inbox reauthorized successfully"}, nil
}

func whatsappEmbeddedProviderConfig(accessToken, phoneNumberID, businessAccountID string) map[string]any {
	return map[string]any{"api_key": accessToken, "phone_number_id": phoneNumberID, "business_account_id": businessAccountID, "source": "embedded_signup"}
}

func whatsappInboxChannelConfig(channel *channelmodel.ChannelWhatsApp) map[string]any {
	providerConfig := parseJSONMap(channel.ProviderConfig)
	return map[string]any{
		"phone_number":             channel.PhoneNumber,
		"provider":                 channel.Provider,
		"provider_config":          providerConfig,
		"message_templates":        []any{},
		"reauthorization_required": channel.ReauthorizationRequired,
		"webhook_verify_token":     channel.WebhookVerifyToken,
	}
}

func whatsappWebhookCallbackURL(phoneNumber string) string {
	return strings.TrimRight(envOrDefaultService("FRONTEND_URL", "http://localhost:3000"), "/") + "/webhooks/whatsapp/" + url.PathEscape(phoneNumber)
}

func exchangeWhatsAppAuthorizationCode(ctx context.Context, code string) (string, error) {
	endpoint := whatsappGraphAPIBase() + "/" + whatsappAPIVersion() + "/oauth/access_token"
	params := url.Values{}
	params.Set("client_id", os.Getenv("WHATSAPP_APP_ID"))
	params.Set("client_secret", os.Getenv("WHATSAPP_APP_SECRET"))
	params.Set("code", code)
	body, err := whatsappGET(ctx, endpoint, params, "Token exchange failed")
	if err != nil {
		return "", err
	}
	accessToken, _ := body["access_token"].(string)
	if accessToken == "" {
		return "", fmt.Errorf("No access token in response")
	}
	return accessToken, nil
}

func fetchWhatsAppPhoneInfo(ctx context.Context, wabaID, requestedPhoneNumberID, accessToken string) (whatsappPhoneInfo, error) {
	endpoint := whatsappGraphAPIBase() + "/" + whatsappAPIVersion() + "/" + url.PathEscape(wabaID) + "/phone_numbers"
	params := url.Values{"access_token": []string{accessToken}}
	body, err := whatsappGET(ctx, endpoint, params, "WABA phone numbers fetch failed")
	if err != nil {
		return whatsappPhoneInfo{}, err
	}
	items, _ := body["data"].([]any)
	for _, item := range items {
		phone, _ := item.(map[string]any)
		if len(phone) == 0 {
			continue
		}
		if requestedPhoneNumberID == "" || whatsappStringMapValue(phone, "id") == requestedPhoneNumberID {
			return buildWhatsAppPhoneInfo(phone), nil
		}
	}
	if len(items) > 0 {
		if phone, _ := items[0].(map[string]any); len(phone) > 0 {
			return buildWhatsAppPhoneInfo(phone), nil
		}
	}
	return whatsappPhoneInfo{}, fmt.Errorf("No phone numbers found for WABA %s", wabaID)
}

func validateWhatsAppTokenAccess(ctx context.Context, accessToken, wabaID string) error {
	endpoint := whatsappGraphAPIBase() + "/" + whatsappAPIVersion() + "/debug_token"
	params := url.Values{}
	params.Set("input_token", accessToken)
	params.Set("access_token", os.Getenv("WHATSAPP_APP_ID")+"|"+os.Getenv("WHATSAPP_APP_SECRET"))
	body, err := whatsappGET(ctx, endpoint, params, "Token validation failed")
	if err != nil {
		return err
	}
	data, _ := body["data"].(map[string]any)
	scopes, _ := data["granular_scopes"].([]any)
	for _, item := range scopes {
		scope, _ := item.(map[string]any)
		if whatsappStringMapValue(scope, "scope") != "whatsapp_business_management" {
			continue
		}
		for _, id := range anySlice(scope["target_ids"]) {
			if fmt.Sprint(id) == wabaID {
				return nil
			}
		}
		return fmt.Errorf("Token does not have access to WABA %s", wabaID)
	}
	return fmt.Errorf("No WABA scope found in token")
}

func whatsappGET(ctx context.Context, endpoint string, params url.Values, errorPrefix string) (map[string]any, error) {
	if len(params) > 0 {
		endpoint += "?" + params.Encode()
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return nil, err
	}
	resp, err := whatsappAuthorizationHTTPClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
		return nil, fmt.Errorf("%s: %s", errorPrefix, string(body))
	}
	var parsed map[string]any
	if err := json.Unmarshal(body, &parsed); err != nil {
		return nil, err
	}
	return parsed, nil
}

func buildWhatsAppPhoneInfo(phone map[string]any) whatsappPhoneInfo {
	display := sanitizeWhatsAppPhoneNumber(whatsappStringMapValue(phone, "display_phone_number"))
	name := firstNonEmpty(whatsappStringMapValue(phone, "verified_name"), whatsappStringMapValue(phone, "display_phone_number"))
	return whatsappPhoneInfo{PhoneNumberID: whatsappStringMapValue(phone, "id"), PhoneNumber: "+" + display, BusinessName: name}
}

func sanitizeWhatsAppPhoneNumber(phone string) string {
	replacer := strings.NewReplacer(" ", "", "-", "", "(", "", ")", "", ".", "", "+", "")
	return strings.TrimSpace(replacer.Replace(phone))
}

func whatsappGraphAPIBase() string {
	return strings.TrimRight(envOrDefaultService("WHATSAPP_GRAPH_API_BASE", "https://graph.facebook.com"), "/")
}
func whatsappAPIVersion() string {
	return strings.Trim(strings.TrimSpace(envOrDefaultService("WHATSAPP_API_VERSION", "v22.0")), "/")
}

func envOrDefaultService(key string, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
		return value
	}
	return fallback
}

func parseJSONMap(raw string) map[string]any {
	var out map[string]any
	if err := json.Unmarshal([]byte(raw), &out); err != nil || out == nil {
		return map[string]any{}
	}
	return out
}

func whatsappStringMapValue(values map[string]any, key string) string {
	if values == nil || values[key] == nil {
		return ""
	}
	return fmt.Sprint(values[key])
}

func anySlice(value any) []any {
	if items, ok := value.([]any); ok {
		return items
	}
	return nil
}