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

import (
	"fmt"
	"strings"
)

// PostgreSQLGenerator PostgreSQL SQL生成器
type PostgreSQLGenerator struct{}

// NewPostgreSQLGenerator 创建PostgreSQL生成器实例
func NewPostgreSQLGenerator() *PostgreSQLGenerator {
	return &PostgreSQLGenerator{}
}

func (pg *PostgreSQLGenerator) DBType() string {
	return "postgresql"
}

func (pg *PostgreSQLGenerator) TableExistsSQL(tableName string) string {
	return fmt.Sprintf(
		"SELECT EXISTS (SELECT FROM information_schema.tables WHERE table_schema = 'public' AND table_name = '%s')",
		strings.ToLower(tableName),
	)
}

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

func (pg *PostgreSQLGenerator) 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, pg.getPostgreSQLType(col)))

		// 添加选项（转换MySQL选项到PostgreSQL）
		for _, opt := range col.Options {
			pgOpt := pg.convertOption(opt, col)
			if pgOpt != "" {
				sql.WriteString(" " + pgOpt)
			}
		}

		// 添加默认值
		if col.Default != "" {
			pgDefault := pg.convertDefaultValue(col.Default, col.Type)
			if pgDefault != "" {
				sql.WriteString(" DEFAULT " + pgDefault)
			}
		}

		// 列注释将在表创建后单独添加

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

	// 添加主键约束（从列选项中提取）
	primaryKeys := pg.extractPrimaryKeys(columns)
	if len(primaryKeys) > 0 {
		sql.WriteString(fmt.Sprintf("  ,PRIMARY KEY (%s)\n", strings.Join(primaryKeys, ", ")))
	}

	sql.WriteString(");\n")

	// 添加表注释
	if table.Schema.Comment != "" {
		sql.WriteString(fmt.Sprintf("COMMENT ON TABLE %s IS '%s';\n",
			table.Name, table.Schema.Comment))
	}

	// 添加列注释
	for _, col := range columns {
		if col.Comment != "" {
			sql.WriteString(fmt.Sprintf("COMMENT ON COLUMN %s.%s IS '%s';\n",
				table.Name, col.Name, col.Comment))
		}
	}

	// 添加索引（PostgreSQL中索引在表外创建）
	for _, idx := range table.Schema.Indexes {
		if idx.Unique {
			sql.WriteString(fmt.Sprintf("CREATE UNIQUE INDEX IF NOT EXISTS %s ON %s (%s);\n",
				idx.Name, table.Name, strings.Join(idx.Columns, ", ")))
		} else {
			sql.WriteString(fmt.Sprintf("CREATE INDEX IF NOT EXISTS %s ON %s (%s);\n",
				idx.Name, table.Name, strings.Join(idx.Columns, ", ")))
		}
	}

	return sql.String()
}

// getPostgreSQLType 获取PostgreSQL数据类型
func (pg *PostgreSQLGenerator) getPostgreSQLType(col ColumnSchema) string {
	switch col.Type {
	case "TINYINT":
		if col.Length == 1 {
			return "BOOLEAN"
		}
		return "SMALLINT"
	case "BOOL":
		return "BOOLEAN"
	case "DATETIME":
		return "TIMESTAMP"
	case "TIMESTAMP":
		return "TIMESTAMP"
	case "JSON":
		return "JSONB"
	case "BLOB":
		return "BYTEA"
	case "INT":
		return "INTEGER"
	case "BIGINT":
		return "BIGINT"
	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"
	case "CHAR":
		if col.Length > 0 {
			return fmt.Sprintf("CHAR(%d)", col.Length)
		}
		return "CHAR"
	case "TEXT":
		return "TEXT"
	case "FLOAT":
		return "REAL"
	case "DOUBLE":
		return "DOUBLE PRECISION"
	case "DATE":
		return "DATE"
	case "TIME":
		return "TIME"
	default:
		return col.Type
	}
}

// convertOption 转换选项到PostgreSQL语法
func (pg *PostgreSQLGenerator) convertOption(option string, col ColumnSchema) string {
	option = strings.ToUpper(option)

	switch option {
	case "NOT NULL":
		return "NOT NULL"
	case "UNIQUE":
		return "UNIQUE"
	case "AUTO_INCREMENT":
		// PostgreSQL使用SERIAL/BIGSERIAL/SMALLSERIAL
		// 已在getPostgreSQLType中处理
		return ""
	case "PRIMARY KEY":
		// 主键将在表级别定义
		return ""
	default:
		return option
	}
}

// convertDefaultValue 转换默认值
func (pg *PostgreSQLGenerator) convertDefaultValue(value, colType string) string {
	value = strings.TrimSpace(value)

	// 移除引号（如果有）
	if strings.HasPrefix(value, "'") && strings.HasSuffix(value, "'") {
		value = value[1 : len(value)-1]
	}

	// 处理布尔值
	if strings.EqualFold(colType, "BOOLEAN") || strings.EqualFold(colType, "BOOL") {
		switch strings.ToUpper(value) {
		case "1", "TRUE", "'TRUE'":
			return "TRUE"
		case "0", "FALSE", "'FALSE'":
			return "FALSE"
		}
	}

	// 处理时间戳
	if strings.Contains(strings.ToUpper(value), "CURRENT_TIMESTAMP") {
		return "CURRENT_TIMESTAMP"
	}

	// 处理数字
	if _, ok := pg.isNumber(value); ok {
		return value
	}

	// 其他情况加单引号
	return "'" + value + "'"
}

// isNumber 检查字符串是否为数字
func (pg *PostgreSQLGenerator) isNumber(s string) (float64, bool) {
	var f float64
	_, err := fmt.Sscanf(s, "%f", &f)
	return f, err == nil
}

// extractPrimaryKeys 从列中提取主键
func (pg *PostgreSQLGenerator) extractPrimaryKeys(columns []ColumnSchema) []string {
	var primaryKeys []string
	for _, col := range columns {
		for _, opt := range col.Options {
			if strings.ToUpper(opt) == "PRIMARY KEY" {
				primaryKeys = append(primaryKeys, col.Name)
				break
			}
		}
	}
	return primaryKeys
}

func init() {
	RegisterGenerator(NewPostgreSQLGenerator())
}