// Package database provides database initialization, migration, and management utilities
// for the 3x-ui panel using GORM with SQLite.
package database

import (
	"bytes"
	"errors"
	"io"
	"log"
	"os"
	"path"
	"slices"
	"strings"
	"time"

	"github.com/mhsanaei/3x-ui/v3/config"
	"github.com/mhsanaei/3x-ui/v3/database/model"
	"github.com/mhsanaei/3x-ui/v3/util/crypto"
	"github.com/mhsanaei/3x-ui/v3/xray"

	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

var db *gorm.DB

const (
	defaultUsername = "admin"
	defaultPassword = "admin"
)

func initModels() error {
	models := []any{
		&model.User{},
		&model.Inbound{},
		&model.OutboundTraffics{},
		&model.Setting{},
		&model.InboundClientIps{},
		&xray.ClientTraffic{},
		&model.HistoryOfSeeders{},
		&model.CustomGeoResource{},
		&model.Node{},
		&model.ApiToken{},
	}
	for _, mdl := range models {
		if err := db.AutoMigrate(mdl); err != nil {
			if isIgnorableDuplicateColumnErr(err, mdl) {
				log.Printf("Ignoring duplicate column during auto migration for %T: %v", mdl, err)
				continue
			}
			log.Printf("Error auto migrating model: %v", err)
			return err
		}
	}
	return nil
}

func isIgnorableDuplicateColumnErr(err error, mdl any) bool {
	if err == nil {
		return false
	}
	errMsg := strings.ToLower(err.Error())
	const dupPrefix = "duplicate column name:"
	if !strings.Contains(errMsg, dupPrefix) {
		return false
	}
	idx := strings.Index(errMsg, dupPrefix)
	if idx < 0 {
		return false
	}
	col := strings.TrimSpace(errMsg[idx+len(dupPrefix):])
	col = strings.Trim(col, "`\"[]")
	if col == "" {
		return false
	}
	return db != nil && db.Migrator().HasColumn(mdl, col)
}

// initUser creates a default admin user if the users table is empty.
func initUser() error {
	empty, err := isTableEmpty("users")
	if err != nil {
		log.Printf("Error checking if users table is empty: %v", err)
		return err
	}
	if empty {
		hashedPassword, err := crypto.HashPasswordAsBcrypt(defaultPassword)

		if err != nil {
			log.Printf("Error hashing default password: %v", err)
			return err
		}

		user := &model.User{
			Username: defaultUsername,
			Password: hashedPassword,
		}
		return db.Create(user).Error
	}
	return nil
}

// runSeeders migrates user passwords to bcrypt and records seeder execution to prevent re-running.
func runSeeders(isUsersEmpty bool) error {
	empty, err := isTableEmpty("history_of_seeders")
	if err != nil {
		log.Printf("Error checking if users table is empty: %v", err)
		return err
	}

	if empty && isUsersEmpty {
		hashSeeder := &model.HistoryOfSeeders{
			SeederName: "UserPasswordHash",
		}
		if err := db.Create(hashSeeder).Error; err != nil {
			return err
		}
		return seedApiTokens()
	}

	var seedersHistory []string
	if err := db.Model(&model.HistoryOfSeeders{}).Pluck("seeder_name", &seedersHistory).Error; err != nil {
		log.Printf("Error fetching seeder history: %v", err)
		return err
	}

	if !slices.Contains(seedersHistory, "UserPasswordHash") && !isUsersEmpty {
		var users []model.User
		if err := db.Find(&users).Error; err != nil {
			log.Printf("Error fetching users for password migration: %v", err)
			return err
		}

		for _, user := range users {
			hashedPassword, err := crypto.HashPasswordAsBcrypt(user.Password)
			if err != nil {
				log.Printf("Error hashing password for user '%s': %v", user.Username, err)
				return err
			}
			if err := db.Model(&user).Update("password", hashedPassword).Error; err != nil {
				log.Printf("Error updating password for user '%s': %v", user.Username, err)
				return err
			}
		}

		hashSeeder := &model.HistoryOfSeeders{
			SeederName: "UserPasswordHash",
		}
		if err := db.Create(hashSeeder).Error; err != nil {
			return err
		}
	}

	if !slices.Contains(seedersHistory, "ApiTokensTable") {
		if err := seedApiTokens(); err != nil {
			return err
		}
	}
	return nil
}

// seedApiTokens copies the legacy `apiToken` setting into the new
// api_tokens table as a row named "default" so existing central panels
// keep working after the upgrade. Idempotent — records itself in
// history_of_seeders and only runs when api_tokens is empty.
func seedApiTokens() error {
	empty, err := isTableEmpty("api_tokens")
	if err != nil {
		return err
	}
	if empty {
		var legacy model.Setting
		err := db.Model(model.Setting{}).Where("key = ?", "apiToken").First(&legacy).Error
		if err == nil && legacy.Value != "" {
			row := &model.ApiToken{
				Name:    "default",
				Token:   legacy.Value,
				Enabled: true,
			}
			if err := db.Create(row).Error; err != nil {
				log.Printf("Error migrating legacy apiToken: %v", err)
				return err
			}
		}
	}
	return db.Create(&model.HistoryOfSeeders{SeederName: "ApiTokensTable"}).Error
}

// isTableEmpty returns true if the named table contains zero rows.
func isTableEmpty(tableName string) (bool, error) {
	var count int64
	err := db.Table(tableName).Count(&count).Error
	return count == 0, err
}

// InitDB sets up the database connection, migrates models, and runs seeders.
func InitDB(dbPath string) error {
	dir := path.Dir(dbPath)
	err := os.MkdirAll(dir, 0755)
	if err != nil {
		return err
	}

	var gormLogger logger.Interface

	if config.IsDebug() {
		gormLogger = logger.Default
	} else {
		gormLogger = logger.Discard
	}

	c := &gorm.Config{
		Logger: gormLogger,
	}
	dsn := dbPath + "?_journal_mode=WAL&_busy_timeout=10000&_synchronous=NORMAL&_txlock=immediate"
	db, err = gorm.Open(sqlite.Open(dsn), c)
	if err != nil {
		return err
	}

	sqlDB, err := db.DB()
	if err != nil {
		return err
	}
	if _, err := sqlDB.Exec("PRAGMA journal_mode=WAL"); err != nil {
		return err
	}
	if _, err := sqlDB.Exec("PRAGMA busy_timeout=10000"); err != nil {
		return err
	}
	if _, err := sqlDB.Exec("PRAGMA synchronous=NORMAL"); err != nil {
		return err
	}
	sqlDB.SetMaxOpenConns(8)
	sqlDB.SetMaxIdleConns(4)
	sqlDB.SetConnMaxLifetime(time.Hour)

	if err := initModels(); err != nil {
		return err
	}

	isUsersEmpty, err := isTableEmpty("users")
	if err != nil {
		return err
	}

	if err := initUser(); err != nil {
		return err
	}
	return runSeeders(isUsersEmpty)
}

// CloseDB closes the database connection if it exists.
func CloseDB() error {
	if db != nil {
		sqlDB, err := db.DB()
		if err != nil {
			return err
		}
		return sqlDB.Close()
	}
	return nil
}

// GetDB returns the global GORM database instance.
func GetDB() *gorm.DB {
	return db
}

func IsNotFound(err error) bool {
	return errors.Is(err, gorm.ErrRecordNotFound)
}

// IsSQLiteDB checks if the given file is a valid SQLite database by reading its signature.
func IsSQLiteDB(file io.ReaderAt) (bool, error) {
	signature := []byte("SQLite format 3\x00")
	buf := make([]byte, len(signature))
	_, err := file.ReadAt(buf, 0)
	if err != nil {
		return false, err
	}
	return bytes.Equal(buf, signature), nil
}

// Checkpoint performs a WAL checkpoint on the SQLite database to ensure data consistency.
func Checkpoint() error {
	// Update WAL
	err := db.Exec("PRAGMA wal_checkpoint;").Error
	if err != nil {
		return err
	}
	return nil
}

// ValidateSQLiteDB opens the provided sqlite DB path with a throw-away connection
// and runs a PRAGMA integrity_check to ensure the file is structurally sound.
// It does not mutate global state or run migrations.
func ValidateSQLiteDB(dbPath string) error {
	if _, err := os.Stat(dbPath); err != nil { // file must exist
		return err
	}
	gdb, err := gorm.Open(sqlite.Open(dbPath), &gorm.Config{Logger: logger.Discard})
	if err != nil {
		return err
	}
	sqlDB, err := gdb.DB()
	if err != nil {
		return err
	}
	defer sqlDB.Close()
	var res string
	if err := gdb.Raw("PRAGMA integrity_check;").Scan(&res).Error; err != nil {
		return err
	}
	if res != "ok" {
		return errors.New("sqlite integrity check failed: " + res)
	}
	return nil
}
