package gorm

import (
	"fmt"
	"reflect"
	"strings"
	"time"
)

type mysql struct {
	commonDialect
}

func init() {
	RegisterDialect("mysql", &mysql{})
}

func (mysql) GetName() string {
	return "mysql"
}

func (mysql) Quote(key string) string {
	return fmt.Sprintf("`%s`", key)
}

// Get Data Type for MySQL Dialect
func (mysql) DataTypeOf(field *StructField) string {
	var dataValue, sqlType, size, additionalType = ParseFieldStructForDialect(field)

	if sqlType == "" {
		switch dataValue.Kind() {
		case reflect.Bool:
			sqlType = "boolean"
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32:
			if _, ok := field.TagSettings["AUTO_INCREMENT"]; ok || field.IsPrimaryKey {
				sqlType = "int AUTO_INCREMENT"
			} else {
				sqlType = "int"
			}
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uintptr:
			if _, ok := field.TagSettings["AUTO_INCREMENT"]; ok || field.IsPrimaryKey {
				sqlType = "int unsigned AUTO_INCREMENT"
			} else {
				sqlType = "int unsigned"
			}
		case reflect.Int64:
			if _, ok := field.TagSettings["AUTO_INCREMENT"]; ok || field.IsPrimaryKey {
				sqlType = "bigint AUTO_INCREMENT"
			} else {
				sqlType = "bigint"
			}
		case reflect.Uint64:
			if _, ok := field.TagSettings["AUTO_INCREMENT"]; ok || field.IsPrimaryKey {
				sqlType = "bigint unsigned AUTO_INCREMENT"
			} else {
				sqlType = "bigint unsigned"
			}
		case reflect.Float32, reflect.Float64:
			sqlType = "double"
		case reflect.String:
			if size > 0 && size < 65532 {
				sqlType = fmt.Sprintf("varchar(%d)", size)
			} else {
				sqlType = "longtext"
			}
		case reflect.Struct:
			if _, ok := dataValue.Interface().(time.Time); ok {
				if _, ok := field.TagSettings["NOT NULL"]; ok {
					sqlType = "timestamp"
				} else {
					sqlType = "timestamp NULL"
				}
			}
		default:
			if _, ok := dataValue.Interface().([]byte); ok {
				if size > 0 && size < 65532 {
					sqlType = fmt.Sprintf("varbinary(%d)", size)
				} else {
					sqlType = "longblob"
				}
			}
		}
	}

	if sqlType == "" {
		panic(fmt.Sprintf("invalid sql type %s (%s) for mysql", dataValue.Type().Name(), dataValue.Kind().String()))
	}

	if strings.TrimSpace(additionalType) == "" {
		return sqlType
	}
	return fmt.Sprintf("%v %v", sqlType, additionalType)
}

func (s mysql) RemoveIndex(tableName string, indexName string) error {
	_, err := s.db.Exec(fmt.Sprintf("DROP INDEX %v ON %v", indexName, s.Quote(tableName)))
	return err
}

func (s mysql) HasForeignKey(tableName string, foreignKeyName string) bool {
	var count int
	s.db.QueryRow("SELECT count(*) FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_SCHEMA=? AND TABLE_NAME=? AND CONSTRAINT_NAME=? AND CONSTRAINT_TYPE='FOREIGN KEY'", s.currentDatabase(), tableName, foreignKeyName).Scan(&count)
	return count > 0
}

func (s mysql) currentDatabase() (name string) {
	s.db.QueryRow("SELECT DATABASE()").Scan(&name)
	return
}

func (mysql) SelectFromDummyTable() string {
	return "FROM DUAL"
}