package db

import (
	"context"
	"excel_export/biz/export"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
	"runtime/trace"
)

var _ export.DataFetcher = new(Db)

type Db struct {
	db *gorm.DB
}

func NewDb(str string) (*Db, error) {
	db, err := gorm.Open(mysql.Open(str + ""))
	if err != nil {
		return nil, err
	}
	//db = db.Debug()
	return &Db{
		db: db,
	}, nil
}

func (d *Db) Fetch(s string) (*export.Data, error) {
	fetchRegion := trace.StartRegion(context.Background(), "db.fetch")
	defer func() {
		fetchRegion.End()
	}()
	rows, err := d.db.Raw(s).Rows()
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	titles, err := rows.Columns()
	if err != nil {
		return nil, err
	}

	var dd []map[string]interface{}
	d.db.ScanRows(rows, &dd)
	data := make([]interface{}, len(dd))
	for i, m := range dd {
		row := make([]interface{}, 0, len(m))
		for _, title := range titles {
			row = append(row, m[title])
		}
		data[i] = interface{}(row)
	}

	return &export.Data{
		Title: titles,
		Data:  data,
	}, nil
}