package report

import (
	"bytes"
	"context"
	"fmt"
	"log/slog"
	"reflect"
	"strconv"
	"vctp/db"

	"github.com/xuri/excelize/v2"
)

func CreateReport(logger *slog.Logger, Database db.Database, ctx context.Context) ([]byte, error) {
	var xlsx *excelize.File
	sheetName := "Inventory Report"
	var buffer bytes.Buffer

	logger.Debug("Querying inventory table")
	results, err := Database.Queries().ListInventory(ctx)
	if err != nil {
		logger.Error("Unable to query inventory table", "error", err)
		return nil, err
	}

	if len(results) == 0 {
		logger.Error("Empty inventory results")
		return nil, fmt.Errorf("Empty inventory results")
	}

	// Use reflection to determine column headings from the first item
	firstItem := results[0]
	v := reflect.ValueOf(firstItem)
	typeOfItem := v.Type()

	// Create column headers dynamically
	for i := 0; i < v.NumField(); i++ {
		column := string(rune('A'+i)) + "1" // A1, B1, C1, etc.
		xlsx.SetCellValue(sheetName, column, typeOfItem.Field(i).Name)
	}

	// Populate the Excel file with data from the Inventory table
	for i, item := range results {
		v = reflect.ValueOf(item)
		for j := 0; j < v.NumField(); j++ {
			column := string(rune('A'+j)) + strconv.Itoa(i+2) // Start from row 2
			xlsx.SetCellValue(sheetName, column, v.Field(j).Interface())
		}
	}

	// Save the Excel file into a byte buffer
	if err := xlsx.Write(&buffer); err != nil {
		return nil, err
	}

	return buffer.Bytes(), nil
}