package router

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

	"github.com/gin-gonic/gin"
	"github.com/gochat/gochat/internal/model"
	channelmodel "github.com/gochat/gochat/internal/model/channel"
	"github.com/golang-jwt/jwt/v5"
	"gorm.io/gorm"
)

func googleEmailCallback(db *gorm.DB) gin.HandlerFunc {
	return emailOAuthCallback(db, emailCallbackConfig{
		Provider:       "google",
		ClientIDEnv:    "GOOGLE_OAUTH_CLIENT_ID",
		SecretEnv:      "GOOGLE_OAUTH_CLIENT_SECRET",
		TokenURLEnv:    "GOOGLE_OAUTH_TOKEN_URL",
		DefaultURL:     "https://oauth2.googleapis.com/token",
		IMAPAddress:    "imap.gmail.com",
		StateSecretEnv: "GOOGLE_OAUTH_CLIENT_SECRET",
	})
}

func microsoftEmailCallback(db *gorm.DB) gin.HandlerFunc {
	return emailOAuthCallback(db, emailCallbackConfig{
		Provider:       "microsoft",
		ClientIDEnv:    "AZURE_APP_ID",
		SecretEnv:      "AZURE_APP_SECRET",
		TokenURLEnv:    "MICROSOFT_OAUTH_TOKEN_URL",
		DefaultURL:     "https://login.microsoftonline.com/common/oauth2/v2.0/token",
		IMAPAddress:    "outlook.office365.com",
		StateSecretEnv: "AZURE_APP_SECRET",
	})
}

type emailCallbackConfig struct {
	Provider       string
	ClientIDEnv    string
	SecretEnv      string
	TokenURLEnv    string
	DefaultURL     string
	IMAPAddress    string
	StateSecretEnv string
}

func emailOAuthCallback(db *gorm.DB, cfg emailCallbackConfig) gin.HandlerFunc {
	return func(c *gin.Context) {
		accountID, ok := callbackAccountID(c.Query("state"), os.Getenv(cfg.StateSecretEnv))
		if !ok || db == nil || c.Query("code") == "" || !accountExists(c, db, accountID) {
			c.Redirect(http.StatusFound, frontendBaseURL())
			return
		}

		body, err := exchangeOAuthToken(c, oauthTokenExchangeRequest{
			TokenURL:     envOrDefault(cfg.TokenURLEnv, cfg.DefaultURL),
			ClientID:     os.Getenv(cfg.ClientIDEnv),
			ClientSecret: os.Getenv(cfg.SecretEnv),
			Code:         c.Query("code"),
			RedirectURI:  frontendBaseURL() + "/" + cfg.Provider + "/callback",
		})
		claims, claimErr := parseJWTClaimsUnverified(body["id_token"])
		if err != nil || claimErr != nil || strings.TrimSpace(claimString(claims, "email")) == "" {
			c.Redirect(http.StatusFound, frontendBaseURL())
			return
		}

		email := claimString(claims, "email")
		login := email
		if cfg.Provider == "microsoft" {
			if value := firstNonBlank(claimString(claims, "preferred_username"), claimString(claims, "upn")); value != "" {
				login = value
			}
		}
		name := firstNonBlank(claimString(claims, "name"), strings.Split(email, "@")[0])
		inbox, existed, err := upsertEmailOAuthInbox(c, db, accountID, email, login, name, cfg.IMAPAddress, cfg.Provider, body)
		if err != nil {
			c.Redirect(http.StatusFound, frontendBaseURL())
			return
		}
		if existed {
			c.Redirect(http.StatusFound, inboxSettingsURL(accountID, inbox.ID))
			return
		}
		c.Redirect(http.StatusFound, inboxAgentsURL(accountID, inbox.ID))
	}
}

func instagramChannelCallback(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		accountID, ok := callbackAccountID(c.Query("state"), os.Getenv("INSTAGRAM_APP_SECRET"))
		if !ok {
			c.Redirect(http.StatusFound, frontendBaseURL())
			return
		}
		if c.Query("error") != "" {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "instagram", map[string]string{
				"error_type":    firstNonBlank(c.Query("error"), "authorization_error"),
				"code":          "400",
				"error_message": firstNonBlank(c.Query("error_description"), "Authorization was denied"),
			}))
			return
		}
		if db == nil || c.Query("code") == "" || !accountExists(c, db, accountID) {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "instagram", nil))
			return
		}

		body, err := exchangeOAuthToken(c, oauthTokenExchangeRequest{
			TokenURL:     envOrDefault("INSTAGRAM_OAUTH_TOKEN_URL", "https://api.instagram.com/oauth/access_token"),
			ClientID:     os.Getenv("INSTAGRAM_APP_ID"),
			ClientSecret: os.Getenv("INSTAGRAM_APP_SECRET"),
			Code:         c.Query("code"),
			RedirectURI:  frontendBaseURL() + "/instagram/callback",
		})
		instagramID := firstNonBlank(body["instagram_account_id"], body["user_id"], body["id"])
		username := firstNonBlank(body["username"], body["instagram_account_name"], "Instagram")
		if err != nil || body["access_token"] == "" || instagramID == "" {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "instagram", map[string]string{"error_type": "OAuthException", "code": "400", "error_message": "failed to exchange OAuth token"}))
			return
		}

		inbox, existed, err := upsertInstagramInbox(c, db, accountID, instagramID, username, body)
		if err != nil {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "instagram", map[string]string{"error_type": "RecordInvalid", "code": "500", "error_message": err.Error()}))
			return
		}
		if existed {
			c.Redirect(http.StatusFound, inboxSettingsURL(accountID, inbox.ID))
			return
		}
		c.Redirect(http.StatusFound, inboxAgentsURL(accountID, inbox.ID))
	}
}

func tiktokChannelCallback(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		accountID, ok := callbackAccountID(c.Query("state"), os.Getenv("TIKTOK_APP_SECRET"))
		if !ok {
			c.Redirect(http.StatusFound, frontendBaseURL())
			return
		}
		if c.Query("error") != "" {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "tiktok", map[string]string{
				"error_type":    firstNonBlank(c.Query("error"), "access_denied"),
				"code":          c.Query("error_code"),
				"error_message": firstNonBlank(c.Query("error_description"), "User cancelled the Authorization"),
			}))
			return
		}
		if db == nil || c.Query("code") == "" || !accountExists(c, db, accountID) {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "tiktok", nil))
			return
		}

		body, err := exchangeOAuthToken(c, oauthTokenExchangeRequest{
			TokenURL:     envOrDefault("TIKTOK_OAUTH_TOKEN_URL", "https://business-api.tiktok.com/open_api/v1.3/oauth2/access_token/"),
			ClientID:     os.Getenv("TIKTOK_APP_ID"),
			ClientSecret: os.Getenv("TIKTOK_APP_SECRET"),
			Code:         c.Query("code"),
			RedirectURI:  frontendBaseURL() + "/tiktok/callback",
		})
		businessID := firstNonBlank(body["business_id"], body["tiktok_business_id"], body["advertiser_id"])
		if err != nil || body["access_token"] == "" || businessID == "" {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "tiktok", map[string]string{"error_type": "OAuthException", "code": "500", "error_message": "failed to exchange OAuth token"}))
			return
		}
		if !tiktokScopesGranted(body["scope"]) {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "tiktok", map[string]string{"error_type": "ungranted_scopes", "code": "400", "error_message": "User did not grant all the required scopes"}))
			return
		}

		name := firstNonBlank(body["display_name"], body["username"], "TikTok")
		inbox, existed, err := upsertTikTokInbox(c, db, accountID, businessID, name, body)
		if err != nil {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "tiktok", map[string]string{"error_type": "RecordInvalid", "code": "500", "error_message": err.Error()}))
			return
		}
		if existed {
			c.Redirect(http.StatusFound, inboxSettingsURL(accountID, inbox.ID))
			return
		}
		c.Redirect(http.StatusFound, inboxAgentsURL(accountID, inbox.ID))
	}
}

func twitterChannelCallback(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		accountID, ok := callbackAccountID(firstNonBlank(c.Query("state"), c.Query("account_id")), os.Getenv("TWITTER_CONSUMER_SECRET"))
		if !ok {
			c.Redirect(http.StatusFound, frontendBaseURL())
			return
		}
		if c.Query("denied") != "" || db == nil || !accountExists(c, db, accountID) {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "twitter", nil))
			return
		}
		body, err := exchangeTwitterAccessToken(c)
		if err != nil || body.Get("oauth_token") == "" || body.Get("user_id") == "" {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "twitter", nil))
			return
		}
		inbox, _, err := upsertTwitterInbox(c, db, accountID, body)
		if err != nil {
			c.Redirect(http.StatusFound, newInboxURL(accountID, "twitter", nil))
			return
		}
		c.Redirect(http.StatusFound, inboxAgentsURL(accountID, inbox.ID))
	}
}

func upsertEmailOAuthInbox(c *gin.Context, db *gorm.DB, accountID uint, email, login, name, imapAddress, provider string, tokenBody map[string]string) (*model.Inbox, bool, error) {
	var channel channelmodel.ChannelEmail
	existed := db.WithContext(c.Request.Context()).Where("account_id = ? AND (imap_login = ? OR email = ?)", accountID, login, email).First(&channel).Error == nil
	if existed {
		channel.IMAPLogin = login
		channel.IMAPAddress = imapAddress
		channel.IMAPPort = 993
		channel.IMAPEnabled = true
		channel.MailboxName = name
		if err := db.WithContext(c.Request.Context()).Save(&channel).Error; err != nil {
			return nil, false, err
		}
		var inbox model.Inbox
		if err := db.WithContext(c.Request.Context()).Where("id = ? AND account_id = ?", channel.InboxID, accountID).First(&inbox).Error; err != nil {
			return nil, false, err
		}
		inbox.Name = name
		inbox.ChannelConfig = oauthInboxConfig(provider, tokenBody)
		return &inbox, true, db.WithContext(c.Request.Context()).Save(&inbox).Error
	}

	channel = channelmodel.ChannelEmail{AccountID: accountID, Email: email, MailboxName: name, Domain: emailDomain(email), IMAPEnabled: true, IMAPAddress: imapAddress, IMAPPort: 993, IMAPLogin: login, IMAPSSLMode: "ssl"}
	if err := db.WithContext(c.Request.Context()).Create(&channel).Error; err != nil {
		return nil, false, err
	}
	inbox := model.Inbox{AccountID: accountID, Name: name, ChannelType: "email", ChannelID: channel.ID, Enabled: true, ChannelConfig: oauthInboxConfig(provider, tokenBody)}
	if err := db.WithContext(c.Request.Context()).Create(&inbox).Error; err != nil {
		return nil, false, err
	}
	channel.InboxID = inbox.ID
	return &inbox, false, db.WithContext(c.Request.Context()).Save(&channel).Error
}

func upsertInstagramInbox(c *gin.Context, db *gorm.DB, accountID uint, instagramID, username string, body map[string]string) (*model.Inbox, bool, error) {
	var channel channelmodel.ChannelInstagram
	existed := db.WithContext(c.Request.Context()).Where("account_id = ? AND instagram_account_id = ?", accountID, instagramID).First(&channel).Error == nil
	if existed {
		channel.PageAccessToken = body["access_token"]
		channel.InstagramAccountName = username
		if err := db.WithContext(c.Request.Context()).Save(&channel).Error; err != nil {
			return nil, false, err
		}
		var inbox model.Inbox
		if err := db.WithContext(c.Request.Context()).Where("id = ? AND account_id = ?", channel.InboxID, accountID).First(&inbox).Error; err != nil {
			return nil, false, err
		}
		inbox.Name = username
		return &inbox, true, db.WithContext(c.Request.Context()).Save(&inbox).Error
	}
	channel = channelmodel.ChannelInstagram{AccountID: accountID, InstagramAccountID: instagramID, InstagramBusinessAccountID: body["instagram_business_account_id"], PageAccessToken: body["access_token"], ConnectedFBPageID: firstNonBlank(body["connected_fb_page_id"], body["page_id"]), InstagramAccountName: username}
	if channel.ConnectedFBPageID == "" {
		channel.ConnectedFBPageID = instagramID
	}
	if err := db.WithContext(c.Request.Context()).Create(&channel).Error; err != nil {
		return nil, false, err
	}
	inbox := model.Inbox{AccountID: accountID, Name: username, ChannelType: "instagram", ChannelID: channel.ID, Enabled: true}
	if err := db.WithContext(c.Request.Context()).Create(&inbox).Error; err != nil {
		return nil, false, err
	}
	channel.InboxID = inbox.ID
	return &inbox, false, db.WithContext(c.Request.Context()).Save(&channel).Error
}

func upsertTikTokInbox(c *gin.Context, db *gorm.DB, accountID uint, businessID, name string, body map[string]string) (*model.Inbox, bool, error) {
	var channel channelmodel.ChannelTikTok
	existed := db.WithContext(c.Request.Context()).Where("account_id = ? AND tiktok_business_id = ?", accountID, businessID).First(&channel).Error == nil
	expiresAt := time.Now().UTC().Add(time.Duration(parseIntDefault(body["expires_in"], 3600)) * time.Second)
	if existed {
		channel.AccessToken = body["access_token"]
		channel.RefreshToken = body["refresh_token"]
		channel.TokenExpiresAt = expiresAt
		if err := db.WithContext(c.Request.Context()).Save(&channel).Error; err != nil {
			return nil, false, err
		}
		var inbox model.Inbox
		if err := db.WithContext(c.Request.Context()).Where("id = ? AND account_id = ?", channel.InboxID, accountID).First(&inbox).Error; err != nil {
			return nil, false, err
		}
		inbox.Name = name
		return &inbox, true, db.WithContext(c.Request.Context()).Save(&inbox).Error
	}
	channel = channelmodel.ChannelTikTok{AccountID: accountID, TikTokBusinessID: businessID, AccessToken: body["access_token"], RefreshToken: body["refresh_token"], TokenExpiresAt: expiresAt}
	if err := db.WithContext(c.Request.Context()).Create(&channel).Error; err != nil {
		return nil, false, err
	}
	inbox := model.Inbox{AccountID: accountID, Name: name, ChannelType: "tiktok", ChannelID: channel.ID, Enabled: true}
	if err := db.WithContext(c.Request.Context()).Create(&inbox).Error; err != nil {
		return nil, false, err
	}
	channel.InboxID = inbox.ID
	return &inbox, false, db.WithContext(c.Request.Context()).Save(&channel).Error
}

func upsertTwitterInbox(c *gin.Context, db *gorm.DB, accountID uint, values url.Values) (*model.Inbox, bool, error) {
	var channel channelmodel.ChannelTwitter
	existed := db.WithContext(c.Request.Context()).Where("account_id = ? AND twitter_user_id = ?", accountID, values.Get("user_id")).First(&channel).Error == nil
	name := firstNonBlank(values.Get("screen_name"), values.Get("name"), "Twitter")
	if existed {
		channel.TwitterAccessToken = values.Get("oauth_token")
		channel.TwitterAccessTokenSecret = values.Get("oauth_token_secret")
		channel.ScreenName = values.Get("screen_name")
		channel.Name = name
		if err := db.WithContext(c.Request.Context()).Save(&channel).Error; err != nil {
			return nil, false, err
		}
		var inbox model.Inbox
		if err := db.WithContext(c.Request.Context()).Where("id = ? AND account_id = ?", channel.InboxID, accountID).First(&inbox).Error; err != nil {
			return nil, false, err
		}
		return &inbox, true, nil
	}
	channel = channelmodel.ChannelTwitter{AccountID: accountID, TwitterUserID: values.Get("user_id"), TwitterAccessToken: values.Get("oauth_token"), TwitterAccessTokenSecret: values.Get("oauth_token_secret"), ScreenName: values.Get("screen_name"), Name: name, AccessToken: values.Get("oauth_token")}
	if err := db.WithContext(c.Request.Context()).Create(&channel).Error; err != nil {
		return nil, false, err
	}
	inbox := model.Inbox{AccountID: accountID, Name: name, ChannelType: "twitter", ChannelID: channel.ID, Enabled: true}
	if err := db.WithContext(c.Request.Context()).Create(&inbox).Error; err != nil {
		return nil, false, err
	}
	channel.InboxID = inbox.ID
	return &inbox, false, db.WithContext(c.Request.Context()).Save(&channel).Error
}

func parseJWTClaimsUnverified(tokenString string) (jwt.MapClaims, error) {
	claims := jwt.MapClaims{}
	_, _, err := jwt.NewParser().ParseUnverified(tokenString, claims)
	return claims, err
}

func claimString(claims jwt.MapClaims, key string) string {
	if value, ok := claims[key].(string); ok {
		return value
	}
	return ""
}

func oauthInboxConfig(provider string, tokenBody map[string]string) string {
	encoded, _ := json.Marshal(map[string]any{"provider": provider, "provider_config": compactStringMap(tokenBody)})
	return string(encoded)
}

func compactStringMap(values map[string]string) map[string]string {
	result := make(map[string]string, len(values))
	for key, value := range values {
		if value != "" {
			result[key] = value
		}
	}
	return result
}

func exchangeTwitterAccessToken(c *gin.Context) (url.Values, error) {
	form := url.Values{}
	form.Set("oauth_token", c.Query("oauth_token"))
	form.Set("oauth_verifier", c.Query("oauth_verifier"))
	req, err := http.NewRequestWithContext(c.Request.Context(), http.MethodPost, envOrDefault("TWITTER_OAUTH_TOKEN_URL", "https://api.twitter.com/oauth/access_token"), strings.NewReader(form.Encode()))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
		return nil, fmt.Errorf("twitter access token failed: %s", resp.Status)
	}
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	return url.ParseQuery(string(body))
}

func tiktokScopesGranted(scope string) bool {
	if strings.TrimSpace(scope) == "" {
		return true
	}
	granted := map[string]bool{}
	for _, item := range strings.Split(scope, ",") {
		granted[strings.TrimSpace(item)] = true
	}
	for _, required := range []string{"user.info.basic", "user.info.username", "user.info.stats", "user.info.profile", "user.account.type", "user.insights", "message.list.read", "message.list.send", "message.list.manage"} {
		if !granted[required] {
			return false
		}
	}
	return true
}

func inboxAgentsURL(accountID uint, inboxID uint) string {
	return fmt.Sprintf("%s/app/accounts/%d/settings/inboxes/new/%d/agents", frontendBaseURL(), accountID, inboxID)
}

func inboxSettingsURL(accountID uint, inboxID uint) string {
	return fmt.Sprintf("%s/app/accounts/%d/settings/inboxes/%d", frontendBaseURL(), accountID, inboxID)
}

func newInboxURL(accountID uint, channel string, query map[string]string) string {
	base := fmt.Sprintf("%s/app/accounts/%d/settings/inboxes/new/%s", frontendBaseURL(), accountID, channel)
	if len(query) == 0 {
		return base
	}
	values := url.Values{}
	for key, value := range query {
		if value != "" {
			values.Set(key, value)
		}
	}
	if len(values) == 0 {
		return base
	}
	return base + "?" + values.Encode()
}

func emailDomain(email string) string {
	parts := strings.SplitN(email, "@", 2)
	if len(parts) == 2 {
		return parts[1]
	}
	return ""
}

func parseIntDefault(value string, fallback int) int {
	parsed, err := strconv.Atoi(value)
	if err != nil {
		return fallback
	}
	return parsed
}

func firstNonBlank(values ...string) string {
	for _, value := range values {
		if strings.TrimSpace(value) != "" {
			return value
		}
	}
	return ""
}