package db

import (
	"crypto/rand"
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"fmt"
	"os"
	"path/filepath"
	"time"

	_ "modernc.org/sqlite"
)

var DB *sql.DB

func Init() error {
	dir, _ := os.Executable()
	dbPath := filepath.Join(filepath.Dir(dir), "data", "game.db")
	os.MkdirAll(filepath.Dir(dbPath), 0755)

	var err error
	DB, err = sql.Open("sqlite", dbPath)
	if err != nil {
		return err
	}
	_, err = DB.Exec(`
		CREATE TABLE IF NOT EXISTS users (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			username TEXT UNIQUE NOT NULL,
			password_hash TEXT NOT NULL,
			salt TEXT NOT NULL,
			nickname TEXT NOT NULL,
			bio TEXT DEFAULT '',
			avatar TEXT DEFAULT '',
			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
			last_login TIMESTAMP
		);
		CREATE TABLE IF NOT EXISTS sessions (
			token TEXT PRIMARY KEY,
			user_id INTEGER NOT NULL,
			username TEXT NOT NULL,
			nickname TEXT NOT NULL,
			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
			FOREIGN KEY (user_id) REFERENCES users(id)
		);
	`)
	return err
}

type User struct {
	ID       int64
	Username string
	Nickname string
	Bio      string
	Avatar   string
}

func hashPassword(password, salt string) string {
	h := sha256.Sum256([]byte(password + salt))
	return hex.EncodeToString(h[:])
}

func generateSalt() string {
	b := make([]byte, 16)
	rand.Read(b)
	return hex.EncodeToString(b)
}

func generateToken() string {
	b := make([]byte, 32)
	rand.Read(b)
	return hex.EncodeToString(b)
}

func Register(username, password, nickname string) (*User, error) {
	if len(username) < 2 || len(password) < 4 {
		return nil, fmt.Errorf("用户名至少2位，密码至少4位")
	}
	if nickname == "" {
		nickname = username
	}
	salt := generateSalt()
	hash := hashPassword(password, salt)
	res, err := DB.Exec("INSERT INTO users (username, password_hash, salt, nickname) VALUES (?, ?, ?, ?)",
		username, hash, salt, nickname)
	if err != nil {
		return nil, fmt.Errorf("用户名已存在")
	}
	id, _ := res.LastInsertId()
	return &User{ID: id, Username: username, Nickname: nickname}, nil
}

func Login(username, password string) (string, *User, error) {
	var id int64
	var hash, salt, nickname, bio, avatar string
	err := DB.QueryRow("SELECT id, password_hash, salt, nickname, bio, avatar FROM users WHERE username = ?",
		username).Scan(&id, &hash, &salt, &nickname, &bio, &avatar)
	if err != nil {
		return "", nil, fmt.Errorf("用户不存在")
	}
	if hashPassword(password, salt) != hash {
		return "", nil, fmt.Errorf("密码错误")
	}
	DB.Exec("UPDATE users SET last_login = ? WHERE id = ?", time.Now(), id)

	token := generateToken()
	DB.Exec("INSERT OR REPLACE INTO sessions (token, user_id, username, nickname) VALUES (?, ?, ?, ?)",
		token, id, username, nickname)

	return token, &User{ID: id, Username: username, Nickname: nickname, Bio: bio, Avatar: avatar}, nil
}

func ValidateToken(token string) (*User, error) {
	var id int64
	var username, nickname string
	err := DB.QueryRow("SELECT user_id, username, nickname FROM sessions WHERE token = ?", token).
		Scan(&id, &username, &nickname)
	if err != nil {
		return nil, fmt.Errorf("无效的令牌")
	}
	return &User{ID: id, Username: username, Nickname: nickname}, nil
}

func Logout(token string) {
	DB.Exec("DELETE FROM sessions WHERE token = ?", token)
}

func UpdateProfile(userID int64, nickname, bio, avatar string) error {
	_, err := DB.Exec("UPDATE users SET nickname=?, bio=?, avatar=? WHERE id=?", nickname, bio, avatar, userID)
	return err
}

func GetProfile(username string) (*User, error) {
	var u User
	err := DB.QueryRow("SELECT id, username, nickname, bio, avatar FROM users WHERE username=?", username).
		Scan(&u.ID, &u.Username, &u.Nickname, &u.Bio, &u.Avatar)
	if err != nil {
		return nil, fmt.Errorf("用户不存在")
	}
	return &u, nil
}