package migrate

import (
	"regexp"
	"strconv"
	"strings"
)

// ============================== 类型归一 ==============================

var (
	reParen    = regexp.MustCompile(`\(([^)]*)\)`)               // (11) / (10,2) / ('a','b')
	reUnsigned = regexp.MustCompile(`(?i)\bunsigned\b`)          // mysql unsigned 修饰
	rePgCast   = regexp.MustCompile(`(?i)^'(.*)'::[\w\s\[\]]+$`) // pgsql 'x'::character varying
	rePgFunc   = regexp.MustCompile(`(?i)^(current_timestamp|now|localtime)\(\d*\)$`)
)

// normalizeType 源方言原始列类型转换为中间类型
//
// 同时解析长度、精度与枚举值
func normalizeType(dialect, rawType string) (typ string, length, scale int, enumVals []string) {
	t := strings.ToLower(strings.TrimSpace(rawType))
	unsigned := reUnsigned.MatchString(t)
	t = reUnsigned.ReplaceAllString(t, "")
	t = strings.TrimSpace(t)

	// 提取括号参数（长度/精度/枚举值）
	pargs := ""
	if m := reParen.FindStringSubmatch(t); m != nil {
		pargs = strings.TrimSpace(m[1])
		t = strings.TrimSpace(reParen.ReplaceAllString(t, ""))
	}
	// 剥离 pgsql 时区/精度修饰
	t = strings.TrimSuffix(t, " without time zone")
	t = strings.TrimSuffix(t, " with time zone")

	// 枚举/集合：括号内为引号列表
	if strings.HasPrefix(t, "enum") || strings.HasPrefix(t, "set") || strings.HasPrefix(t, "enum(") {
		for _, v := range strings.Split(pargs, ",") {
			if v = strings.Trim(strings.TrimSpace(v), "'\""); v != "" {
				enumVals = append(enumVals, v)
			}
		}
		if strings.HasPrefix(t, "set") {
			return TypeSet, 0, 0, enumVals
		}
		return TypeEnum, 0, 0, enumVals
	}

	// decimal/numeric：pargs = "10,2"
	if parts := strings.Split(pargs, ","); len(parts) == 2 {
		if p, e1 := strconv.Atoi(strings.TrimSpace(parts[0])); e1 == nil {
			if s, e2 := strconv.Atoi(strings.TrimSpace(parts[1])); e2 == nil {
				return TypeDecimal, p, s, nil
			}
		}
	}

	// 单参数括号：varchar(150) / int(11)
	if pargs != "" {
		if n, err := strconv.Atoi(strings.TrimSpace(strings.Split(pargs, ",")[0])); err == nil {
			length = n
		}
	}

	switch t {
	case "bool", "boolean", "bit":
		return TypeBool, 0, 0, nil
	case "tinyint":
		// mysql tinyint(1) 惯例为布尔
		if length == 1 {
			return TypeBool, 0, 0, nil
		}
		if unsigned {
			return TypeSmallint, 0, 0, nil
		}
		return TypeTinyint, 0, 0, nil
	case "smallint", "year":
		return TypeSmallint, 0, 0, nil
	case "mediumint", "int", "integer":
		return TypeInt, 0, 0, nil
	case "bigint":
		return TypeBigint, 0, 0, nil
	case "float", "real", "binary_float":
		return TypeFloat, 0, 0, nil
	case "double", "double precision", "float8", "binary_double":
		return TypeDouble, 0, 0, nil
	case "decimal", "numeric", "number", "dec", "fixed":
		if length == 0 {
			return TypeDecimal, 0, 0, nil
		}
		return TypeDecimal, length, scale, nil
	case "varchar", "character varying", "nvarchar", "varchar2":
		return TypeVarchar, length, 0, nil
	case "char", "character", "nchar", "char2":
		return TypeChar, length, 0, nil
	case "tinytext":
		return TypeTinytext, 0, 0, nil
	case "text", "mediumtext", "longtext", "clob", "ntext", "json", "jsonb", "xml":
		if t == "json" || t == "jsonb" {
			return TypeJson, 0, 0, nil
		}
		if t == "mediumtext" {
			return TypeMediumText, 0, 0, nil
		}
		if t == "longtext" {
			return TypeLongText, 0, 0, nil
		}
		return TypeText, 0, 0, nil
	case "date":
		return TypeDate, 0, 0, nil
	case "time":
		return TypeTime, 0, 0, nil
	case "datetime", "timestamp", "smalldatetime", "datetime2":
		return TypeDateTime, 0, 0, nil
	case "tinyblob", "blob", "mediumblob", "longblob", "binary", "varbinary",
		"bytea", "image", "raw", "long raw":
		return TypeBlob, 0, 0, nil
	case "uuid":
		return TypeChar, 36, 0, nil
	}
	return TypeOther, 0, 0, nil
}

// cleanDefault 归一默认值表达式
//
// PostgreSQL 剥去类型转换与函数括号，其余方言原样保留
func cleanDefault(dialect string, raw any) string {
	if raw == nil {
		return ""
	}
	s := strings.TrimSpace(toString(raw))
	if s == "" || strings.EqualFold(s, "null") {
		return ""
	}
	if dialect == "pgsql" {
		if m := rePgCast.FindStringSubmatch(s); m != nil {
			s = m[1]
		} else if rePgFunc.MatchString(s) {
			s = "CURRENT_TIMESTAMP"
		}
	}
	if dialect == "mysql" && strings.EqualFold(s, "current_timestamp()") {
		s = "CURRENT_TIMESTAMP"
	}
	return s
}

// toString 将任意默认值转为字符串
// 兼容不同驱动的返回类型差异
func toString(v any) string {
	switch t := v.(type) {
	case nil:
		return ""
	case string:
		return t
	case []byte:
		return string(t)
	default:
		return strings.TrimSpace(strings.TrimSuffix(strval(t), ".0"))
	}
}

// strval 数值转字符串
func strval(v any) string {
	switch t := v.(type) {
	case int64:
		return strconv.FormatInt(t, 10)
	case float64:
		return strconv.FormatFloat(t, 'f', -1, 64)
	default:
		return strings.TrimSpace(toStr(v))
	}
}

// toStr 尝试调用 String 方法转为字符串
func toStr(v any) string {
	if s, ok := v.(interface{ String() string }); ok {
		return s.String()
	}
	return ""
}