package service

import (
	"errors"
	"log"
	"strings"
	"time"

	"github.com/basketikun/infinite-canvas/config"
	"github.com/basketikun/infinite-canvas/model"
	"github.com/basketikun/infinite-canvas/repository"
	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
	"golang.org/x/crypto/bcrypt"
)

type TokenClaims struct {
	UserID   string         `json:"userId"`
	Username string         `json:"username"`
	Role     model.UserRole `json:"role"`
	jwt.RegisteredClaims
}

func EnsureDefaultAdmin() error {
	if strings.TrimSpace(config.Cfg.AdminUsername) == "" || strings.TrimSpace(config.Cfg.AdminPassword) == "" {
		return nil
	}
	WarnDefaultSecurityConfig()
	hasAdmin, err := repository.HasAdmin()
	if err != nil || hasAdmin {
		return err
	}
	hash, err := hashPassword(config.Cfg.AdminPassword)
	if err != nil {
		return err
	}
	_, err = repository.SaveUser(model.User{
		ID:        newID("user"),
		Username:  strings.TrimSpace(config.Cfg.AdminUsername),
		Password:  hash,
		Role:      model.UserRoleAdmin,
		CreatedAt: now(),
		UpdatedAt: now(),
	})
	return err
}

func Register(username string, password string) (model.AuthSession, error) {
	return model.AuthSession{}, errors.New("注册功能暂时关闭")
	username = strings.TrimSpace(username)
	if strings.ContainsAny(username, " \t\r\n") {
		return model.AuthSession{}, errors.New("用户名不能包含空格")
	}
	if username == "" || password == "" {
		return model.AuthSession{}, errors.New("用户名和密码不能为空")
	}
	if _, ok, err := repository.GetUserByUsername(username); err != nil || ok {
		if err != nil {
			return model.AuthSession{}, err
		}
		return model.AuthSession{}, errors.New("用户名已存在")
	}
	hash, err := hashPassword(password)
	if err != nil {
		return model.AuthSession{}, err
	}
	user, err := repository.SaveUser(model.User{
		ID:        newID("user"),
		Username:  username,
		Password:  hash,
		Role:      model.UserRoleUser,
		CreatedAt: now(),
		UpdatedAt: now(),
	})
	if err != nil {
		return model.AuthSession{}, err
	}
	return newSession(user)
}

func Login(username string, password string) (model.AuthSession, error) {
	user, ok, err := repository.GetUserByUsername(strings.TrimSpace(username))
	if err != nil {
		return model.AuthSession{}, err
	}
	if !ok || bcrypt.CompareHashAndPassword([]byte(user.Password), []byte(password)) != nil {
		return model.AuthSession{}, errors.New("用户名或密码错误")
	}
	return newSession(user)
}

func ParseToken(tokenText string) (TokenClaims, error) {
	claims := TokenClaims{}
	token, err := jwt.ParseWithClaims(tokenText, &claims, func(token *jwt.Token) (any, error) {
		return []byte(config.Cfg.JWTSecret), nil
	})
	if err != nil || !token.Valid {
		return TokenClaims{}, errors.New("登录状态无效")
	}
	return claims, nil
}

func CurrentAuthUser(tokenText string) (model.AuthUser, bool) {
	claims, err := ParseToken(tokenText)
	if err != nil {
		return model.AuthUser{}, false
	}
	user, ok, err := repository.GetUserByID(claims.UserID)
	if err != nil || !ok {
		return model.AuthUser{}, false
	}
	return model.PublicUser(user), true
}

func ListUsers(q model.Query) (model.UserList, error) {
	users, total, err := repository.ListUsers(q)
	if err != nil {
		return model.UserList{}, err
	}
	for i := range users {
		users[i].Password = ""
	}
	return model.UserList{Items: users, Total: int(total)}, nil
}

func SaveUser(user model.User, password string) (model.User, error) {
	user.Username = strings.TrimSpace(user.Username)
	if strings.ContainsAny(user.Username, " \t\r\n") {
		return user, errors.New("用户名不能包含空格")
	}
	if user.Username == "" {
		return user, errors.New("用户名不能为空")
	}
	if user.Role == "" || user.Role == model.UserRoleGuest {
		user.Role = model.UserRoleUser
	}
	if saved, ok, err := repository.GetUserByUsername(user.Username); err != nil {
		return user, err
	} else if ok && saved.ID != user.ID {
		return user, errors.New("用户名已存在")
	}
	if user.ID == "" {
		user.ID = newID("user")
		user.CreatedAt = now()
	} else if saved, ok, err := repository.GetUserByID(user.ID); err != nil {
		return user, err
	} else if ok {
		user.CreatedAt = saved.CreatedAt
		user.Password = saved.Password
	}
	if password != "" {
		hash, err := hashPassword(password)
		if err != nil {
			return user, err
		}
		user.Password = hash
	}
	if user.Password == "" {
		return user, errors.New("密码不能为空")
	}
	user.UpdatedAt = now()
	user, err := repository.SaveUser(user)
	user.Password = ""
	return user, err
}

func DeleteUser(id string) error {
	return repository.DeleteUser(id)
}

func GuestUser() model.AuthUser {
	return model.AuthUser{ID: "", Username: "guest", Role: model.UserRoleGuest}
}

func newSession(user model.User) (model.AuthSession, error) {
	token, err := newToken(user)
	if err != nil {
		return model.AuthSession{}, err
	}
	return model.AuthSession{Token: token, User: model.PublicUser(user)}, nil
}

func newToken(user model.User) (string, error) {
	expireHours := config.Cfg.JWTExpireHours
	if expireHours <= 0 {
		expireHours = 168
	}
	claims := TokenClaims{
		UserID:   user.ID,
		Username: user.Username,
		Role:     user.Role,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Duration(expireHours) * time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Subject:   user.ID,
		},
	}
	return jwt.NewWithClaims(jwt.SigningMethodHS256, claims).SignedString([]byte(config.Cfg.JWTSecret))
}

func hashPassword(password string) (string, error) {
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(hash), err
}

func now() string {
	return time.Now().Format(time.RFC3339)
}

func newID(prefix string) string {
	return prefix + "-" + uuid.NewString()
}

func WarnDefaultSecurityConfig() {
	if config.Cfg.AdminUsername == "admin" && config.Cfg.AdminPassword == "infinite-canvas" {
		log.Println("WARNING: using default admin credentials, please set ADMIN_USERNAME and ADMIN_PASSWORD to safer values before deployment")
	}
	if config.Cfg.JWTSecret == "infinite-canvas" {
		log.Println("WARNING: using default JWT_SECRET, please set a long random value before deployment")
	}
}