package database

import (
	"errors"
	"fmt"
	"strconv"

	"github.com/golang-migrate/migrate/v4"
	"github.com/golang-migrate/migrate/v4/database/postgres"
	"github.com/golang-migrate/migrate/v4/source/iofs"
	"gorm.io/gorm"
	"silk-server-go/migrations"
)

// CurrentSchemaVersion 是当前后端代码期望的迁移版本。
const CurrentSchemaVersion = "9"

// RunMigrations 使用嵌入式 SQL 迁移文件将数据库升级到最新版本。
func RunMigrations(db *gorm.DB) error {
	sqlDB, err := db.DB()
	if err != nil {
		return fmt.Errorf("获取数据库连接: %w", err)
	}

	sourceDriver, err := iofs.New(migrations.FS, ".")
	if err != nil {
		return fmt.Errorf("加载嵌入式迁移文件: %w", err)
	}
	defer sourceDriver.Close()

	databaseDriver, err := postgres.WithInstance(sqlDB, &postgres.Config{})
	if err != nil {
		return fmt.Errorf("初始化 PostgreSQL 迁移驱动: %w", err)
	}

	m, err := migrate.NewWithInstance("iofs", sourceDriver, "postgres", databaseDriver)
	if err != nil {
		return fmt.Errorf("创建迁移实例: %w", err)
	}

	if err := m.Up(); err != nil && !errors.Is(err, migrate.ErrNoChange) {
		return fmt.Errorf("执行数据库迁移: %w", err)
	}

	return nil
}

// CheckSchemaVersion 校验 schema_migrations 当前版本与 expected 一致，且不是 dirty。
func CheckSchemaVersion(db *gorm.DB, expected string) error {
	var version int64
	var dirty bool

	row := db.Raw("SELECT version, dirty FROM schema_migrations ORDER BY version DESC LIMIT 1").Row()
	if err := row.Scan(&version, &dirty); err != nil {
		return fmt.Errorf("读取 schema_migrations: %w", err)
	}
	if dirty {
		return fmt.Errorf("schema 迁移处于 dirty 状态，版本 %d", version)
	}
	if strconv.FormatInt(version, 10) != expected {
		return fmt.Errorf("schema 版本不匹配：当前 %d，期望 %s", version, expected)
	}
	return nil
}