package auth

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/google/uuid"
	"golang.org/x/crypto/bcrypt"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
)

// Auth handles authentication
type Auth struct {
	db            *sql.DB
	googleConfig  *oauth2.Config
	discordConfig *oauth2.Config
	sessionStore  map[string]*Session
}

// Session represents a user session
type Session struct {
	UserID    int64
	Email     string
	Name      string
	IsAdmin   bool
	ExpiresAt time.Time
}

// NewAuth creates a new auth instance
func NewAuth(db *sql.DB) (*Auth, error) {
	auth := &Auth{
		db:           db,
		sessionStore: make(map[string]*Session),
	}

	// Initialize Google OAuth
	googleClientID := os.Getenv("GOOGLE_CLIENT_ID")
	googleClientSecret := os.Getenv("GOOGLE_CLIENT_SECRET")
	if googleClientID != "" && googleClientSecret != "" {
		auth.googleConfig = &oauth2.Config{
			ClientID:     googleClientID,
			ClientSecret: googleClientSecret,
			RedirectURL:  os.Getenv("GOOGLE_REDIRECT_URL"),
			Scopes:       []string{"openid", "profile", "email"},
			Endpoint:     google.Endpoint,
		}
	}

	// Initialize Discord OAuth
	discordClientID := os.Getenv("DISCORD_CLIENT_ID")
	discordClientSecret := os.Getenv("DISCORD_CLIENT_SECRET")
	if discordClientID != "" && discordClientSecret != "" {
		auth.discordConfig = &oauth2.Config{
			ClientID:     discordClientID,
			ClientSecret: discordClientSecret,
			RedirectURL:  os.Getenv("DISCORD_REDIRECT_URL"),
			Scopes:       []string{"identify", "email"},
			Endpoint: oauth2.Endpoint{
				AuthURL:  "https://discord.com/api/oauth2/authorize",
				TokenURL: "https://discord.com/api/oauth2/token",
			},
		}
	}

	// Initialize admin settings on startup to ensure they persist between boots
	if err := auth.initializeSettings(); err != nil {
		log.Printf("Warning: Failed to initialize admin settings: %v", err)
		// Don't fail startup, but log the warning
	}

	// Initialize test local user from environment variables (for testing only)
	if err := auth.initializeTestUser(); err != nil {
		log.Printf("Warning: Failed to initialize test user: %v", err)
		// Don't fail startup, but log the warning
	}

	return auth, nil
}

// initializeSettings ensures all admin settings are initialized with defaults if they don't exist
func (a *Auth) initializeSettings() error {
	// Initialize registration_enabled setting (default: true) if it doesn't exist
	var settingCount int
	err := a.db.QueryRow("SELECT COUNT(*) FROM settings WHERE key = ?", "registration_enabled").Scan(&settingCount)
	if err != nil {
		return fmt.Errorf("failed to check registration_enabled setting: %w", err)
	}
	if settingCount == 0 {
		_, err = a.db.Exec(
			`INSERT INTO settings (key, value, updated_at) VALUES (?, ?, CURRENT_TIMESTAMP)`,
			"registration_enabled", "true",
		)
		if err != nil {
			return fmt.Errorf("failed to initialize registration_enabled setting: %w", err)
		}
		log.Printf("Initialized admin setting: registration_enabled = true")
	}
	return nil
}

// initializeTestUser creates a test local user from environment variables (for testing only)
func (a *Auth) initializeTestUser() error {
	testEmail := os.Getenv("LOCAL_TEST_EMAIL")
	testPassword := os.Getenv("LOCAL_TEST_PASSWORD")

	if testEmail == "" || testPassword == "" {
		// No test user configured, skip
		return nil
	}

	// Check if user already exists
	var exists bool
	err := a.db.QueryRow("SELECT EXISTS(SELECT 1 FROM users WHERE email = ? AND oauth_provider = 'local')", testEmail).Scan(&exists)
	if err != nil {
		return fmt.Errorf("failed to check if test user exists: %w", err)
	}

	if exists {
		// User already exists, skip creation
		log.Printf("Test user %s already exists, skipping creation", testEmail)
		return nil
	}

	// Hash password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(testPassword), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("failed to hash test user password: %w", err)
	}

	// Check if this is the first user (make them admin)
	var userCount int
	a.db.QueryRow("SELECT COUNT(*) FROM users").Scan(&userCount)
	isAdmin := userCount == 0

	// Create test user (use email as name if no name is provided)
	testName := testEmail
	if atIndex := strings.Index(testEmail, "@"); atIndex > 0 {
		testName = testEmail[:atIndex]
	}

	// Create test user
	_, err = a.db.Exec(
		"INSERT INTO users (email, name, oauth_provider, oauth_id, password_hash, is_admin) VALUES (?, ?, 'local', ?, ?, ?)",
		testEmail, testName, testEmail, string(hashedPassword), isAdmin,
	)
	if err != nil {
		return fmt.Errorf("failed to create test user: %w", err)
	}

	log.Printf("Created test user: %s (admin: %v)", testEmail, isAdmin)
	return nil
}

// GoogleLoginURL returns the Google OAuth login URL
func (a *Auth) GoogleLoginURL() (string, error) {
	if a.googleConfig == nil {
		return "", fmt.Errorf("Google OAuth not configured")
	}
	state := uuid.New().String()
	return a.googleConfig.AuthCodeURL(state), nil
}

// DiscordLoginURL returns the Discord OAuth login URL
func (a *Auth) DiscordLoginURL() (string, error) {
	if a.discordConfig == nil {
		return "", fmt.Errorf("Discord OAuth not configured")
	}
	state := uuid.New().String()
	return a.discordConfig.AuthCodeURL(state), nil
}

// GoogleCallback handles Google OAuth callback
func (a *Auth) GoogleCallback(ctx context.Context, code string) (*Session, error) {
	if a.googleConfig == nil {
		return nil, fmt.Errorf("Google OAuth not configured")
	}

	token, err := a.googleConfig.Exchange(ctx, code)
	if err != nil {
		return nil, fmt.Errorf("failed to exchange token: %w", err)
	}

	client := a.googleConfig.Client(ctx, token)
	resp, err := client.Get("https://www.googleapis.com/oauth2/v2/userinfo")
	if err != nil {
		return nil, fmt.Errorf("failed to get user info: %w", err)
	}
	defer resp.Body.Close()

	var userInfo struct {
		ID    string `json:"id"`
		Email string `json:"email"`
		Name  string `json:"name"`
	}

	if err := json.NewDecoder(resp.Body).Decode(&userInfo); err != nil {
		return nil, fmt.Errorf("failed to decode user info: %w", err)
	}

	return a.getOrCreateUser("google", userInfo.ID, userInfo.Email, userInfo.Name)
}

// DiscordCallback handles Discord OAuth callback
func (a *Auth) DiscordCallback(ctx context.Context, code string) (*Session, error) {
	if a.discordConfig == nil {
		return nil, fmt.Errorf("Discord OAuth not configured")
	}

	token, err := a.discordConfig.Exchange(ctx, code)
	if err != nil {
		return nil, fmt.Errorf("failed to exchange token: %w", err)
	}

	client := a.discordConfig.Client(ctx, token)
	resp, err := client.Get("https://discord.com/api/users/@me")
	if err != nil {
		return nil, fmt.Errorf("failed to get user info: %w", err)
	}
	defer resp.Body.Close()

	var userInfo struct {
		ID       string `json:"id"`
		Email    string `json:"email"`
		Username string `json:"username"`
	}

	if err := json.NewDecoder(resp.Body).Decode(&userInfo); err != nil {
		return nil, fmt.Errorf("failed to decode user info: %w", err)
	}

	return a.getOrCreateUser("discord", userInfo.ID, userInfo.Email, userInfo.Username)
}

// IsRegistrationEnabled checks if new user registration is enabled
func (a *Auth) IsRegistrationEnabled() (bool, error) {
	var value string
	err := a.db.QueryRow("SELECT value FROM settings WHERE key = ?", "registration_enabled").Scan(&value)
	if err == sql.ErrNoRows {
		// Default to enabled if setting doesn't exist
		return true, nil
	}
	if err != nil {
		return false, fmt.Errorf("failed to check registration setting: %w", err)
	}
	return value == "true", nil
}

// SetRegistrationEnabled sets whether new user registration is enabled
func (a *Auth) SetRegistrationEnabled(enabled bool) error {
	value := "false"
	if enabled {
		value = "true"
	}

	// Check if setting exists
	var exists bool
	err := a.db.QueryRow("SELECT EXISTS(SELECT 1 FROM settings WHERE key = ?)", "registration_enabled").Scan(&exists)
	if err != nil {
		return fmt.Errorf("failed to check if setting exists: %w", err)
	}

	if exists {
		// Update existing setting
		_, err = a.db.Exec(
			"UPDATE settings SET value = ?, updated_at = CURRENT_TIMESTAMP WHERE key = ?",
			value, "registration_enabled",
		)
		if err != nil {
			return fmt.Errorf("failed to update setting: %w", err)
		}
	} else {
		// Insert new setting
		_, err = a.db.Exec(
			"INSERT INTO settings (key, value, updated_at) VALUES (?, ?, CURRENT_TIMESTAMP)",
			"registration_enabled", value,
		)
		if err != nil {
			return fmt.Errorf("failed to insert setting: %w", err)
		}
	}

	return nil
}

// getOrCreateUser gets or creates a user in the database
// Automatically links accounts by email across different OAuth providers and local login
func (a *Auth) getOrCreateUser(provider, oauthID, email, name string) (*Session, error) {
	var userID int64
	var dbEmail, dbName string
	var isAdmin bool
	var dbProvider, dbOAuthID string

	// First, try to find by provider + oauth_id
	err := a.db.QueryRow(
		"SELECT id, email, name, is_admin, oauth_provider, oauth_id FROM users WHERE oauth_provider = ? AND oauth_id = ?",
		provider, oauthID,
	).Scan(&userID, &dbEmail, &dbName, &isAdmin, &dbProvider, &dbOAuthID)

	if err == sql.ErrNoRows {
		// Not found by provider+oauth_id, check by email for account linking
		err = a.db.QueryRow(
			"SELECT id, email, name, is_admin, oauth_provider, oauth_id FROM users WHERE email = ?",
			email,
		).Scan(&userID, &dbEmail, &dbName, &isAdmin, &dbProvider, &dbOAuthID)

		if err == sql.ErrNoRows {
			// User doesn't exist, check if registration is enabled
			registrationEnabled, err := a.IsRegistrationEnabled()
			if err != nil {
				return nil, fmt.Errorf("failed to check registration setting: %w", err)
			}
			if !registrationEnabled {
				return nil, fmt.Errorf("registration is disabled")
			}

			// Check if this is the first user
			var userCount int
			a.db.QueryRow("SELECT COUNT(*) FROM users").Scan(&userCount)
			isAdmin = userCount == 0

			// Create new user
			err = a.db.QueryRow(
				"INSERT INTO users (email, name, oauth_provider, oauth_id, is_admin) VALUES (?, ?, ?, ?, ?) RETURNING id",
				email, name, provider, oauthID, isAdmin,
			).Scan(&userID)
			if err != nil {
				return nil, fmt.Errorf("failed to create user: %w", err)
			}
		} else if err != nil {
			return nil, fmt.Errorf("failed to query user by email: %w", err)
		} else {
			// User exists with same email but different provider - link accounts by updating provider info
			// This allows the user to log in with any provider that has the same email
			_, err = a.db.Exec(
				"UPDATE users SET oauth_provider = ?, oauth_id = ?, name = ? WHERE id = ?",
				provider, oauthID, name, userID,
			)
			if err != nil {
				return nil, fmt.Errorf("failed to link account: %w", err)
			}
			log.Printf("Linked account: user %d (email: %s) now accessible via %s provider", userID, email, provider)
		}
	} else if err != nil {
		return nil, fmt.Errorf("failed to query user: %w", err)
	} else {
		// User found by provider+oauth_id, update info if changed
		if dbEmail != email || dbName != name {
			_, err = a.db.Exec(
				"UPDATE users SET email = ?, name = ? WHERE id = ?",
				email, name, userID,
			)
			if err != nil {
				return nil, fmt.Errorf("failed to update user: %w", err)
			}
		}
	}

	session := &Session{
		UserID:    userID,
		Email:     email,
		Name:      name,
		IsAdmin:   isAdmin,
		ExpiresAt: time.Now().Add(24 * time.Hour),
	}

	return session, nil
}

// CreateSession creates a new session and returns a session ID
func (a *Auth) CreateSession(session *Session) string {
	sessionID := uuid.New().String()
	a.sessionStore[sessionID] = session
	return sessionID
}

// GetSession retrieves a session by ID
func (a *Auth) GetSession(sessionID string) (*Session, bool) {
	session, ok := a.sessionStore[sessionID]
	if !ok {
		return nil, false
	}
	if time.Now().After(session.ExpiresAt) {
		delete(a.sessionStore, sessionID)
		return nil, false
	}
	// Refresh admin status from database
	var isAdmin bool
	err := a.db.QueryRow("SELECT is_admin FROM users WHERE id = ?", session.UserID).Scan(&isAdmin)
	if err == nil {
		session.IsAdmin = isAdmin
	}
	return session, true
}

// DeleteSession deletes a session
func (a *Auth) DeleteSession(sessionID string) {
	delete(a.sessionStore, sessionID)
}

// Middleware creates an authentication middleware
func (a *Auth) Middleware(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		cookie, err := r.Cookie("session_id")
		if err != nil {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusUnauthorized)
			json.NewEncoder(w).Encode(map[string]string{"error": "Unauthorized"})
			return
		}

		session, ok := a.GetSession(cookie.Value)
		if !ok {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusUnauthorized)
			json.NewEncoder(w).Encode(map[string]string{"error": "Unauthorized"})
			return
		}

		// Add user info to request context
		ctx := context.WithValue(r.Context(), "user_id", session.UserID)
		ctx = context.WithValue(ctx, "user_email", session.Email)
		ctx = context.WithValue(ctx, "user_name", session.Name)
		ctx = context.WithValue(ctx, "is_admin", session.IsAdmin)
		next(w, r.WithContext(ctx))
	}
}

// GetUserID gets the user ID from context
func GetUserID(ctx context.Context) (int64, bool) {
	userID, ok := ctx.Value("user_id").(int64)
	return userID, ok
}

// IsAdmin checks if the user in context is an admin
func IsAdmin(ctx context.Context) bool {
	isAdmin, ok := ctx.Value("is_admin").(bool)
	return ok && isAdmin
}

// AdminMiddleware creates an admin-only middleware
func (a *Auth) AdminMiddleware(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// First check authentication
		cookie, err := r.Cookie("session_id")
		if err != nil {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusUnauthorized)
			json.NewEncoder(w).Encode(map[string]string{"error": "Unauthorized"})
			return
		}

		session, ok := a.GetSession(cookie.Value)
		if !ok {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusUnauthorized)
			json.NewEncoder(w).Encode(map[string]string{"error": "Unauthorized"})
			return
		}

		// Then check admin status
		if !session.IsAdmin {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusForbidden)
			json.NewEncoder(w).Encode(map[string]string{"error": "Forbidden: Admin access required"})
			return
		}

		// Add user info to request context
		ctx := context.WithValue(r.Context(), "user_id", session.UserID)
		ctx = context.WithValue(ctx, "user_email", session.Email)
		ctx = context.WithValue(ctx, "user_name", session.Name)
		ctx = context.WithValue(ctx, "is_admin", session.IsAdmin)
		next(w, r.WithContext(ctx))
	}
}

// IsLocalLoginEnabled returns whether local login is enabled
// Local login is enabled when ENABLE_LOCAL_AUTH environment variable is set to "true"
func (a *Auth) IsLocalLoginEnabled() bool {
	return os.Getenv("ENABLE_LOCAL_AUTH") == "true"
}

// IsGoogleOAuthConfigured returns whether Google OAuth is configured
func (a *Auth) IsGoogleOAuthConfigured() bool {
	return a.googleConfig != nil
}

// IsDiscordOAuthConfigured returns whether Discord OAuth is configured
func (a *Auth) IsDiscordOAuthConfigured() bool {
	return a.discordConfig != nil
}

// LocalLogin handles local username/password authentication
func (a *Auth) LocalLogin(username, password string) (*Session, error) {
	// Find user by email (local users use email as username)
	email := username
	var userID int64
	var dbEmail, dbName, passwordHash string
	var isAdmin bool

	err := a.db.QueryRow(
		"SELECT id, email, name, password_hash, is_admin FROM users WHERE email = ? AND oauth_provider = 'local'",
		email,
	).Scan(&userID, &dbEmail, &dbName, &passwordHash, &isAdmin)

	if err == sql.ErrNoRows {
		return nil, fmt.Errorf("invalid credentials")
	}
	if err != nil {
		return nil, fmt.Errorf("failed to query user: %w", err)
	}

	// Verify password
	if passwordHash == "" {
		return nil, fmt.Errorf("invalid credentials")
	}

	err = bcrypt.CompareHashAndPassword([]byte(passwordHash), []byte(password))
	if err != nil {
		return nil, fmt.Errorf("invalid credentials")
	}

	// Create session
	session := &Session{
		UserID:    userID,
		Email:     dbEmail,
		Name:      dbName,
		IsAdmin:   isAdmin,
		ExpiresAt: time.Now().Add(24 * time.Hour),
	}

	return session, nil
}

// RegisterLocalUser creates a new local user account
func (a *Auth) RegisterLocalUser(email, name, password string) (*Session, error) {
	// Check if registration is enabled
	registrationEnabled, err := a.IsRegistrationEnabled()
	if err != nil {
		return nil, fmt.Errorf("failed to check registration setting: %w", err)
	}
	if !registrationEnabled {
		return nil, fmt.Errorf("registration is disabled")
	}

	// Check if user already exists
	var exists bool
	err = a.db.QueryRow("SELECT EXISTS(SELECT 1 FROM users WHERE email = ?)", email).Scan(&exists)
	if err != nil {
		return nil, fmt.Errorf("failed to check if user exists: %w", err)
	}
	if exists {
		return nil, fmt.Errorf("user with this email already exists")
	}

	// Hash password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return nil, fmt.Errorf("failed to hash password: %w", err)
	}

	// Check if this is the first user (make them admin)
	var userCount int
	a.db.QueryRow("SELECT COUNT(*) FROM users").Scan(&userCount)
	isAdmin := userCount == 0

	// Create user
	var userID int64
	err = a.db.QueryRow(
		"INSERT INTO users (email, name, oauth_provider, oauth_id, password_hash, is_admin) VALUES (?, ?, 'local', ?, ?, ?) RETURNING id",
		email, name, email, string(hashedPassword), isAdmin,
	).Scan(&userID)
	if err != nil {
		return nil, fmt.Errorf("failed to create user: %w", err)
	}

	// Create session
	session := &Session{
		UserID:    userID,
		Email:     email,
		Name:      name,
		IsAdmin:   isAdmin,
		ExpiresAt: time.Now().Add(24 * time.Hour),
	}

	return session, nil
}

// ChangePassword allows a user to change their own password
func (a *Auth) ChangePassword(userID int64, oldPassword, newPassword string) error {
	// Get current password hash
	var passwordHash string
	err := a.db.QueryRow("SELECT password_hash FROM users WHERE id = ? AND oauth_provider = 'local'", userID).Scan(&passwordHash)
	if err == sql.ErrNoRows {
		return fmt.Errorf("user not found or not a local user")
	}
	if err != nil {
		return fmt.Errorf("failed to query user: %w", err)
	}

	// Verify old password
	if passwordHash == "" {
		return fmt.Errorf("user has no password set")
	}

	err = bcrypt.CompareHashAndPassword([]byte(passwordHash), []byte(oldPassword))
	if err != nil {
		return fmt.Errorf("incorrect old password")
	}

	// Hash new password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("failed to hash password: %w", err)
	}

	// Update password
	_, err = a.db.Exec("UPDATE users SET password_hash = ? WHERE id = ?", string(hashedPassword), userID)
	if err != nil {
		return fmt.Errorf("failed to update password: %w", err)
	}

	return nil
}

// AdminChangePassword allows an admin to change any user's password without knowing the old password
func (a *Auth) AdminChangePassword(targetUserID int64, newPassword string) error {
	// Verify user exists and is a local user
	var exists bool
	err := a.db.QueryRow("SELECT EXISTS(SELECT 1 FROM users WHERE id = ? AND oauth_provider = 'local')", targetUserID).Scan(&exists)
	if err != nil {
		return fmt.Errorf("failed to check if user exists: %w", err)
	}
	if !exists {
		return fmt.Errorf("user not found or not a local user")
	}

	// Hash new password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("failed to hash password: %w", err)
	}

	// Update password
	_, err = a.db.Exec("UPDATE users SET password_hash = ? WHERE id = ?", string(hashedPassword), targetUserID)
	if err != nil {
		return fmt.Errorf("failed to update password: %w", err)
	}

	return nil
}

// GetFirstUserID returns the ID of the first user (user with the lowest ID)
func (a *Auth) GetFirstUserID() (int64, error) {
	var firstUserID int64
	err := a.db.QueryRow("SELECT id FROM users ORDER BY id ASC LIMIT 1").Scan(&firstUserID)
	if err == sql.ErrNoRows {
		return 0, fmt.Errorf("no users found")
	}
	if err != nil {
		return 0, fmt.Errorf("failed to get first user ID: %w", err)
	}
	return firstUserID, nil
}

// SetUserAdminStatus allows an admin to change a user's admin status
func (a *Auth) SetUserAdminStatus(targetUserID int64, isAdmin bool) error {
	// Verify user exists
	var exists bool
	err := a.db.QueryRow("SELECT EXISTS(SELECT 1 FROM users WHERE id = ?)", targetUserID).Scan(&exists)
	if err != nil {
		return fmt.Errorf("failed to check if user exists: %w", err)
	}
	if !exists {
		return fmt.Errorf("user not found")
	}

	// Prevent removing admin status from the first user
	firstUserID, err := a.GetFirstUserID()
	if err != nil {
		return fmt.Errorf("failed to check first user: %w", err)
	}
	if targetUserID == firstUserID && !isAdmin {
		return fmt.Errorf("cannot remove admin status from the first user")
	}

	// Update admin status
	_, err = a.db.Exec("UPDATE users SET is_admin = ? WHERE id = ?", isAdmin, targetUserID)
	if err != nil {
		return fmt.Errorf("failed to update admin status: %w", err)
	}

	return nil
}