package generators

import (
	"fmt"
	"strings"
)

// MySQLGenerator MySQL SQL生成器
type MySQLGenerator struct{}

// NewMySQLGenerator 创建MySQL生成器实例
func NewMySQLGenerator() *MySQLGenerator {
	return &MySQLGenerator{}
}

func (mg *MySQLGenerator) DBType() string {
	return "mysql"
}

func (mg *MySQLGenerator) TableExistsSQL(tableName string) string {
	return fmt.Sprintf(
		"SELECT COUNT(*) FROM information_schema.tables WHERE table_schema = DATABASE() AND table_name = '%s'",
		tableName,
	)
}

func (mg *MySQLGenerator) DropTableSQL(tableName string) string {
	return fmt.Sprintf("DROP TABLE IF EXISTS %s", tableName)
}

func (mg *MySQLGenerator) GenerateCreateTable(table TableDDL) string {
	if table.Schema == nil {
		return ""
	}

	var sql strings.Builder
	var pkColumns []string

	// 表头
	sql.WriteString(fmt.Sprintf("CREATE TABLE IF NOT EXISTS %s (\n", table.Name))

	// 第一遍：收集主键列
	for _, col := range table.Schema.Columns {
		for _, opt := range col.Options {
			if strings.ToUpper(opt) == "PRIMARY KEY" {
				pkColumns = append(pkColumns, col.Name)
				break
			}
		}
	}

	// 第二遍：构建列定义
	columnDefs := make([]string, 0, len(table.Schema.Columns))
	for _, col := range table.Schema.Columns {
		colDef := fmt.Sprintf("  %s %s", col.Name, mg.getMySQLType(col))

		// 处理列选项
		for _, opt := range col.Options {
			upperOpt := strings.ToUpper(opt)
			// PRIMARY KEY 选项不在列级定义
			if upperOpt != "PRIMARY KEY" {
				colDef += " " + opt
			}
		}

		// 如果是主键列，确保有 NOT NULL
		isPrimaryKey := false
		for _, pk := range pkColumns {
			if pk == col.Name {
				isPrimaryKey = true
				break
			}
		}

		if isPrimaryKey {
			hasNotNull := false
			for _, opt := range col.Options {
				if strings.ToUpper(opt) == "NOT NULL" {
					hasNotNull = true
					break
				}
			}
			if !hasNotNull {
				colDef += " NOT NULL"
			}
		}

		// 添加默认值
		if col.Default != "" {
			upperDefault := strings.ToUpper(col.Default)
			if strings.Contains(upperDefault, "CURRENT_TIMESTAMP") ||
				strings.Contains(upperDefault, "NOW()") ||
				strings.Contains(upperDefault, "UUID()") ||
				strings.Contains(upperDefault, "NULL") {
				colDef += " DEFAULT " + col.Default
			} else {
				colDef += fmt.Sprintf(" DEFAULT '%s'", col.Default)
			}
		}

		// 添加注释
		if col.Comment != "" {
			colDef += fmt.Sprintf(" COMMENT '%s'", escapeSingleQuote(col.Comment))
		}

		columnDefs = append(columnDefs, colDef)
	}

	// 将所有定义部分合并
	allParts := make([]string, 0)
	allParts = append(allParts, columnDefs...)

	// 添加主键
	if len(pkColumns) > 0 {
		allParts = append(allParts, fmt.Sprintf("  PRIMARY KEY (%s)", strings.Join(pkColumns, ", ")))
	}

	// 添加索引
	for _, idx := range table.Schema.Indexes {
		if idx.Unique {
			allParts = append(allParts, fmt.Sprintf("  UNIQUE KEY %s (%s)",
				idx.Name, strings.Join(idx.Columns, ", ")))
		} else {
			allParts = append(allParts, fmt.Sprintf("  KEY %s (%s)",
				idx.Name, strings.Join(idx.Columns, ", ")))
		}
	}

	// 用逗号连接所有部分
	sql.WriteString(strings.Join(allParts, ",\n"))
	sql.WriteString("\n)")

	// 表注释
	if table.Schema.Comment != "" {
		sql.WriteString(fmt.Sprintf(" COMMENT='%s'", escapeSingleQuote(table.Schema.Comment)))
	}

	// 引擎和字符集
	sql.WriteString(" ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;")

	return sql.String()
}

// getMySQLType 获取MySQL数据类型
func (mg *MySQLGenerator) getMySQLType(col ColumnSchema) string {
	switch col.Type {
	case "DECIMAL":
		if col.Precision > 0 && col.Scale > 0 {
			return fmt.Sprintf("DECIMAL(%d,%d)", col.Precision, col.Scale)
		}
		return "DECIMAL"
	case "VARCHAR":
		if col.Length > 0 {
			return fmt.Sprintf("VARCHAR(%d)", col.Length)
		}
		return "VARCHAR(255)"
	case "CHAR":
		if col.Length > 0 {
			return fmt.Sprintf("CHAR(%d)", col.Length)
		}
		return "CHAR(1)"
	case "INT":
		return "INT"
	case "BIGINT":
		return "BIGINT"
	case "TINYINT":
		return "TINYINT"
	case "BOOL":
		return "TINYINT(1)"
	case "DATETIME":
		return "DATETIME"
	case "TIMESTAMP":
		return "TIMESTAMP"
	case "DATE":
		return "DATE"
	case "TIME":
		return "TIME"
	case "TEXT":
		return "TEXT"
	case "JSON":
		return "JSON"
	case "BLOB":
		return "BLOB"
	case "FLOAT":
		return "FLOAT"
	case "DOUBLE":
		return "DOUBLE"
	default:
		return col.Type
	}
}

// escapeSingleQuote 转义单引号
func escapeSingleQuote(str string) string {
	return strings.ReplaceAll(str, "'", "''")
}

func init() {
	RegisterGenerator(NewMySQLGenerator())
}