package auth

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

	"github.com/google/uuid"
	"golang.org/x/oauth2"

	"custom-start-page/internal/models"
	"custom-start-page/internal/storage"
)

// GoogleUserInfo represents the user info returned by Google
type GoogleUserInfo struct {
	ID            string `json:"id"`
	Email         string `json:"email"`
	VerifiedEmail bool   `json:"verified_email"`
	Name          string `json:"name"`
	Picture       string `json:"picture"`
}

// UserService handles user creation and retrieval
type UserService struct {
	userRepo *storage.UserRepository
}

// NewUserService creates a new user service
func NewUserService(userRepo *storage.UserRepository) *UserService {
	return &UserService{
		userRepo: userRepo,
	}
}

// GetOrCreateUserFromGoogle fetches user info from Google and creates or retrieves the user
func (s *UserService) GetOrCreateUserFromGoogle(ctx context.Context, token *oauth2.Token, oauthConfig *oauth2.Config) (*models.User, error) {
	// Fetch user info from Google
	userInfo, err := s.fetchGoogleUserInfo(ctx, token, oauthConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch Google user info: %w", err)
	}

	// Check if user already exists
	user, err := s.userRepo.GetByOAuthID(ctx, "google", userInfo.ID)
	if err == nil {
		// User exists, update last login time
		user.UpdatedAt = time.Now()
		if err := s.userRepo.Update(ctx, user); err != nil {
			return nil, fmt.Errorf("failed to update user: %w", err)
		}
		return user, nil
	}

	// User doesn't exist, create new user
	user = &models.User{
		ID:            uuid.New().String(),
		Email:         userInfo.Email,
		OAuthProvider: "google",
		OAuthID:       userInfo.ID,
		CreatedAt:     time.Now(),
		UpdatedAt:     time.Now(),
	}

	if err := s.userRepo.Create(ctx, user); err != nil {
		return nil, fmt.Errorf("failed to create user: %w", err)
	}

	return user, nil
}

// fetchGoogleUserInfo fetches user information from Google's userinfo endpoint
func (s *UserService) fetchGoogleUserInfo(ctx context.Context, token *oauth2.Token, oauthConfig *oauth2.Config) (*GoogleUserInfo, error) {
	client := oauthConfig.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()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("failed to get user info: status %d, body: %s", resp.StatusCode, string(body))
	}

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

	if !userInfo.VerifiedEmail {
		return nil, fmt.Errorf("email not verified")
	}

	return &userInfo, nil
}