// mysql.go 根据//table_defintion.go 定义的表结构，编写mysql建立表和索引的代码。
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

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

	// 列定义
	columns := table.Schema.Columns
	for i, col := range columns {
		sql.WriteString(fmt.Sprintf("  %s %s", col.Name, mg.getMySQLType(col)))

		// 添加选项
		for _, opt := range col.Options {
			sql.WriteString(" " + opt)
		}

		// 添加默认值
		if col.Default != "" {
			// 检查是否是函数调用（如CURRENT_TIMESTAMP）
			if strings.Contains(strings.ToUpper(col.Default), "CURRENT_TIMESTAMP") ||
				strings.Contains(strings.ToUpper(col.Default), "NOW()") {
				sql.WriteString(" DEFAULT " + col.Default)
			} else {
				sql.WriteString(fmt.Sprintf(" DEFAULT '%s'", col.Default))
			}
		}

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

		if i < len(columns)-1 {
			sql.WriteString(",")
		}
		sql.WriteString("\n")
	}

	// 添加索引（在MySQL中，索引可以在CREATE TABLE语句中定义）
	for _, idx := range table.Schema.Indexes {
		if idx.Unique {
			sql.WriteString(fmt.Sprintf("  ,UNIQUE KEY %s (%s)\n",
				idx.Name, strings.Join(idx.Columns, ", ")))
		} else {
			sql.WriteString(fmt.Sprintf("  ,KEY %s (%s)\n",
				idx.Name, strings.Join(idx.Columns, ", ")))
		}
	}

	sql.WriteString(")")

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

	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
	}
}

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