package auth

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"github.com/haopengzhan/rsspipe/internal/config"
	"github.com/haopengzhan/rsspipe/internal/db"
	"golang.org/x/crypto/bcrypt"
)

type contextKey string

const UserContextKey contextKey = "user"

type Claims struct {
	UserID   string `json:"user_id"`
	Username string `json:"username"`
	jwt.RegisteredClaims
}

type AuthService struct {
	db     *db.DB
	config *config.Config
}

func NewAuthService(database *db.DB, cfg *config.Config) *AuthService {
	return &AuthService{
		db:     database,
		config: cfg,
	}
}

func (s *AuthService) BootstrapAdmin() error {
	count, err := s.db.CountUsers()
	if err != nil {
		return fmt.Errorf("failed to count users: %w", err)
	}
	if count == 0 {
		hash, err := bcrypt.GenerateFromPassword([]byte(s.config.AdminPassword), bcrypt.DefaultCost)
		if err != nil {
			return fmt.Errorf("failed to hash admin password: %w", err)
		}
		_, err = s.db.CreateUser(s.config.AdminUsername, string(hash))
		if err != nil {
			return fmt.Errorf("failed to bootstrap admin user: %w", err)
		}
		fmt.Printf("==> Initialized Admin user: '%s'\n", s.config.AdminUsername)
	}
	return nil
}

func (s *AuthService) Authenticate(username, password string) (string, error) {
	u, err := s.db.GetUserByUsername(username)
	if err != nil {
		return "", errors.New("invalid username or password")
	}

	if err := bcrypt.CompareHashAndPassword([]byte(u.PasswordHash), []byte(password)); err != nil {
		return "", errors.New("invalid username or password")
	}

	claims := Claims{
		UserID:   u.ID,
		Username: u.Username,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(30 * 24 * time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "rsspipe",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString([]byte(s.config.JWTSecret))
	if err != nil {
		return "", fmt.Errorf("failed to sign token: %w", err)
	}

	return tokenString, nil
}

func (s *AuthService) ValidateToken(tokenString string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return []byte(s.config.JWTSecret), nil
	})

	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(*Claims); ok && token.Valid {
		return claims, nil
	}

	return nil, errors.New("invalid token")
}

func (s *AuthService) Middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		var tokenStr string

		// 1. Check Authorization header
		authHeader := r.Header.Get("Authorization")
		if authHeader != "" {
			parts := strings.Split(authHeader, " ")
			if len(parts) == 2 && strings.ToLower(parts[0]) == "bearer" {
				tokenStr = parts[1]
			}
		}

		// 2. Check Cookie
		if tokenStr == "" {
			if cookie, err := r.Cookie("rsspipe_token"); err == nil {
				tokenStr = cookie.Value
			}
		}

		if tokenStr == "" {
			http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
			return
		}

		claims, err := s.ValidateToken(tokenStr)
		if err != nil {
			http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
			return
		}

		ctx := context.WithValue(r.Context(), UserContextKey, claims)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}