package excel

import (
	"context"
	"encoding/csv"
	"io"
	"os"

	"github.com/gogf/gf/v2/errors/gerror"
)

func StreamCSVFile(ctx context.Context, filePath string, options ParseOptions, handler func(ParsedRow) error) (int, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return 0, gerror.Wrap(err, "open CSV file failed")
	}
	defer file.Close()
	return StreamCSVReader(ctx, file, options, handler)
}

func StreamCSVReader(ctx context.Context, reader io.Reader, options ParseOptions, handler func(ParsedRow) error) (int, error) {
	if handler == nil {
		return 0, gerror.New("CSV row handler cannot be nil")
	}

	csvReader := csv.NewReader(reader)
	csvReader.FieldsPerRecord = -1
	csvReader.ReuseRecord = true

	headers, err := csvReader.Read()
	if err != nil {
		if err == io.EOF {
			return 0, gerror.New("CSV file has no header")
		}
		return 0, gerror.Wrap(err, "read CSV header failed")
	}
	columnIndex, err := buildColumnIndex(headers)
	if err != nil {
		return 0, err
	}
	for _, requiredHeader := range options.RequiredHeaders {
		if _, ok := columnIndex[normalizeHeader(requiredHeader)]; !ok {
			return 0, gerror.Newf("CSV file is missing required column: %s", requiredHeader)
		}
	}

	rowNo := 1
	parsedCount := 0
	for {
		if err = ctx.Err(); err != nil {
			return parsedCount, err
		}
		values, readErr := csvReader.Read()
		if readErr == io.EOF {
			break
		}
		if readErr != nil {
			return parsedCount, gerror.Wrapf(readErr, "read CSV row %d failed", rowNo+1)
		}
		rowNo++
		if isEmptyRow(values) {
			continue
		}

		fields := make(map[string]string, len(columnIndex))
		for columnName, index := range columnIndex {
			fields[columnName] = cellValue(values, index)
		}
		if err = handler(ParsedRow{RowNo: rowNo, Fields: fields}); err != nil {
			return parsedCount, err
		}
		parsedCount++
	}
	if parsedCount == 0 {
		return 0, gerror.New("CSV file has no data rows")
	}
	return parsedCount, nil
}