package functions

import (
	"database/sql"
	"encoding/csv"
	"fmt"
	"strings"

	"github.com/jmoiron/sqlx"
)

// QueryToCSV 无参数查询并返回 CSV 字节数据
func QueryToCSV(db *sqlx.DB, sql string) ([]byte, error) {
	if sql == "" {
		return nil, fmt.Errorf("SQL query cannot be empty")
	}

	rows, err := db.Query(sql)
	if err != nil {
		return nil, fmt.Errorf("query execution failed: %v", err)
	}

	return rowsToCSV(rows)
}

// QueryParamsToCSV 位置参数查询并返回 CSV 字节数据
func QueryPositionalToCSV(db *sqlx.DB, sql string, params ...interface{}) ([]byte, error) {
	if sql == "" {
		return nil, fmt.Errorf("SQL query cannot be empty")
	}

	rows, err := db.Query(sql, params...)
	if err != nil {
		return nil, fmt.Errorf("query execution failed: %v", err)
	}

	return rowsToCSV(rows)
}

// QueryParamsNameToCSV 命名参数查询并返回 CSV 字节数据
// params 可以是 map[string]interface{} 或结构体
func QueryParamsNameToCSV(db *sqlx.DB, sql string, params map[string]interface{}) ([]byte, error) {
	if sql == "" {
		return nil, fmt.Errorf("SQL query cannot be empty")
	}

	query, args, err := sqlx.Named(sql, params)
	if err != nil {
		return nil, fmt.Errorf("failed to bind named parameters: %v", err)
	}

	query = db.Rebind(query)
	rows, err := db.Query(query, args...)
	if err != nil {
		return nil, fmt.Errorf("query execution failed: %v", err)
	}

	return rowsToCSV(rows)
}

// / rowsToCSV 公共方法：将查询结果转换为 CSV 字节数据
func rowsToCSV(rows *sql.Rows) ([]byte, error) {
	defer rows.Close()

	columns, err := rows.Columns()
	if err != nil {
		return nil, fmt.Errorf("failed to get columns: %v", err)
	}

	var builder strings.Builder
	writer := csv.NewWriter(&builder)

	// 写入表头
	if err := writer.Write(columns); err != nil {
		return nil, fmt.Errorf("failed to write CSV header: %v", err)
	}

	for rows.Next() {
		values := make([]interface{}, len(columns))
		valuePtrs := make([]any, len(columns))
		for i := range columns {
			valuePtrs[i] = &values[i]
		}

		if err := rows.Scan(valuePtrs...); err != nil {
			return nil, fmt.Errorf("failed to scan row: %v", err)
		}

		// 所有值转为字符串
		row := make([]string, len(columns))
		for i, val := range values {
			if val == nil {
				row[i] = ""
			} else {
				row[i] = fmt.Sprintf("%v", val)
			}
		}

		if err := writer.Write(row); err != nil {
			return nil, fmt.Errorf("failed to write CSV row: %v", err)
		}
	}

	writer.Flush()
	if err := writer.Error(); err != nil {
		return nil, fmt.Errorf("failed to flush CSV: %v", err)
	}

	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("row iteration error: %v", err)
	}

	return []byte(builder.String()), nil
}