package db

import (
	"errors"
	"fmt"
	"ims/util/backoff"

	"gorm.io/gorm"
	"zestack.dev/env"
)

type mysqlSchemaHelper struct{}

func (s *mysqlSchemaHelper) PublicSchema() string {
	return env.String("DB_NAME")
}

func (s *mysqlSchemaHelper) TenantSchema(tenantId uint) string {
	if tenantId == 0 {
		return s.PublicSchema()
	}
	return fmt.Sprintf(
		"%s%d%s",
		env.String("DB_TENANT_PREFIX", "tenant_"),
		tenantId,
		env.String("DB_TENANT_SUFFIX", ""),
	)
}

func (s *mysqlSchemaHelper) CurrentSchema(tx *gorm.DB) string {
	var schema string
	tx.Raw("SELECT DATABASE()").Row().Scan(&schema)
	return schema
}

func (s *mysqlSchemaHelper) UseSchema(tx *gorm.DB, schema string) (func() error, error) {
	if schema == "" {
		err := errors.New("schema name is empty")
		tx.AddError(err)
		return nil, err
	}

	currentSchema := s.CurrentSchema(tx)
	publicSchema := s.PublicSchema()

	// 当前 schema 与目标 schema 相同，无需切换
	if schema == currentSchema {
		reset := func() error { return nil }
		return reset, nil
	}

	// 不支持租户切换
	if currentSchema != publicSchema && schema != publicSchema {
		err := fmt.Errorf(
			"failed to switch schema %s from current schema %s: %w",
			schema,
			currentSchema,
			ErrSwitchSchema,
		)
		tx.AddError(err)
		return nil, err
	}

	sqlstr := "USE " + tx.Statement.Quote(schema)
	if execErr := tx.Exec(sqlstr).Error; execErr != nil {
		err := fmt.Errorf("failed to set database %q: %w", schema, execErr)
		tx.AddError(err)
		return nil, err
	}

	if schema == publicSchema {
		reset := func() error { return nil }
		return reset, nil
	}

	reset := func() error {
		return tx.Exec("USE " + tx.Statement.Quote(publicSchema)).Error
	}

	return reset, nil
}

func (s *mysqlSchemaHelper) LockSchema(tx *gorm.DB, schema string, retry *backoff.Options) (func() error, error) {
	return AcquireLock(tx, schema, retry)
}

func (s *mysqlSchemaHelper) CreateSchema(tx *gorm.DB, schema string) error {
	sql := fmt.Sprintf("CREATE DATABASE IF NOT EXISTS %s", tx.Statement.Quote(schema))
	return tx.Exec(sql).Error
}

func (s *mysqlSchemaHelper) DropSchema(tx *gorm.DB, schema string) error {
	sql := fmt.Sprintf("DROP DATABASE IF EXISTS %s", tx.Statement.Quote(schema))
	return tx.Exec(sql).Error
}

func (s *mysqlSchemaHelper) String() string {
	return "mysql"
}