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

import (
	"bytes"
	"encoding/json"
	"errors"
	"io"
	"log"
	"os"
	"path"
	"slices"
	"strconv"
	"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/postgres"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

var db *gorm.DB

const (
	DialectSQLite   = "sqlite"
	DialectPostgres = "postgres"
)

// IsPostgres reports whether the active connection is a PostgreSQL backend.
func IsPostgres() bool {
	if db == nil {
		return config.GetDBKind() == "postgres"
	}
	return db.Dialector.Name() == "postgres"
}

// Dialect returns the active GORM dialect name, or "" if the DB is not open.
func Dialect() string {
	if db == nil {
		return ""
	}
	return db.Dialector.Name()
}


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{},
		&model.ClientRecord{},
		&model.ClientInbound{},
		&model.InboundFallback{},
	}
	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())
	// SQLite: "duplicate column name: foo"
	// Postgres: `pq: column "foo" of relation "bar" already exists` / `sqlstate 42701`
	const sqlitePrefix = "duplicate column name:"
	if _, after, ok := strings.Cut(errMsg, sqlitePrefix); ok {
		col := strings.TrimSpace(after)
		col = strings.Trim(col, "`\"[]")
		return col != "" && db != nil && db.Migrator().HasColumn(mdl, col)
	}
	if strings.Contains(errMsg, "already exists") && strings.Contains(errMsg, "column ") {
		// Best effort: extract the column name between the first pair of double quotes.
		if _, after, ok := strings.Cut(errMsg, "column \""); ok {
			rest := after
			if e := strings.Index(rest, "\""); e > 0 {
				col := rest[:e]
				return col != "" && db != nil && db.Migrator().HasColumn(mdl, col)
			}
		}
	}
	return false
}

// 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
		}
	}

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

// normalizeClientJSONFields coerces loosely-typed numeric fields in a raw
// settings.clients entry so json.Unmarshal into model.Client doesn't fail
// when older rows wrote tgId/limitIp/totalGB/etc. as strings. Empty strings
// drop the key so the field falls back to its zero value.
func normalizeClientJSONFields(obj map[string]any) {
	normalizeInt := func(key string) {
		raw, exists := obj[key]
		if !exists {
			return
		}
		s, ok := raw.(string)
		if !ok {
			return
		}
		trimmed := strings.ReplaceAll(strings.TrimSpace(s), " ", "")
		if trimmed == "" {
			delete(obj, key)
			return
		}
		if n, err := strconv.ParseInt(trimmed, 10, 64); err == nil {
			obj[key] = n
		} else {
			delete(obj, key)
		}
	}
	for _, k := range []string{"tgId", "limitIp", "totalGB", "expiryTime", "reset", "created_at", "updated_at"} {
		normalizeInt(k)
	}
}

func seedClientsFromInboundJSON() error {
	var inbounds []model.Inbound
	if err := db.Find(&inbounds).Error; err != nil {
		return err
	}

	return db.Transaction(func(tx *gorm.DB) error {
		byEmail := map[string]*model.ClientRecord{}

		for _, inbound := range inbounds {
			if strings.TrimSpace(inbound.Settings) == "" {
				continue
			}
			var settings map[string]any
			if err := json.Unmarshal([]byte(inbound.Settings), &settings); err != nil {
				log.Printf("ClientsTable seed: skip inbound %d (invalid settings json): %v", inbound.Id, err)
				continue
			}
			rawList, ok := settings["clients"].([]any)
			if !ok {
				continue
			}

			for _, raw := range rawList {
				obj, ok := raw.(map[string]any)
				if !ok {
					continue
				}
				normalizeClientJSONFields(obj)
				blob, err := json.Marshal(obj)
				if err != nil {
					continue
				}
				var c model.Client
				if err := json.Unmarshal(blob, &c); err != nil {
					log.Printf("ClientsTable seed: skip client in inbound %d (unmarshal failed): %v; payload=%s",
						inbound.Id, err, string(blob))
					continue
				}
				email := strings.TrimSpace(c.Email)
				if email == "" {
					continue
				}
				incoming := c.ToRecord()

				row, dup := byEmail[email]
				if !dup {
					if err := tx.Create(incoming).Error; err != nil {
						return err
					}
					byEmail[email] = incoming
					row = incoming
				} else {
					conflicts := model.MergeClientRecord(row, incoming)
					for _, x := range conflicts {
						log.Printf("client merge: email=%s conflict on %s old=%v new=%v kept=%v",
							email, x.Field, x.Old, x.New, x.Kept)
					}
					if err := tx.Save(row).Error; err != nil {
						return err
					}
				}

				link := model.ClientInbound{
					ClientId:     row.Id,
					InboundId:    inbound.Id,
					FlowOverride: c.Flow,
				}
				if err := tx.Where("client_id = ? AND inbound_id = ?", row.Id, inbound.Id).
					FirstOrCreate(&link).Error; err != nil {
					return err
				}
			}
		}

		return tx.Create(&model.HistoryOfSeeders{SeederName: "ClientsTable"}).Error
	})
}

// 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.
// When XUI_DB_TYPE=postgres, dbPath is ignored and XUI_DB_DSN is used instead.
func InitDB(dbPath string) error {
	var gormLogger logger.Interface
	if config.IsDebug() {
		gormLogger = logger.Default
	} else {
		gormLogger = logger.Discard
	}
	c := &gorm.Config{Logger: gormLogger}

	var err error
	switch config.GetDBKind() {
	case "postgres":
		dsn := config.GetDBDSN()
		if dsn == "" {
			return errors.New("XUI_DB_TYPE=postgres but XUI_DB_DSN is empty")
		}
		db, err = gorm.Open(postgres.Open(dsn), c)
		if err != nil {
			return err
		}
	default:
		dir := path.Dir(dbPath)
		if err = os.MkdirAll(dir, 0755); err != nil {
			return err
		}
		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, err := db.DB()
	if 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.
// No-op on PostgreSQL (WAL there is managed by the server).
func Checkpoint() error {
	if IsPostgres() {
		return nil
	}
	return db.Exec("PRAGMA wal_checkpoint;").Error
}

// 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
}