package utils

import (
	"encoding/csv"
	"errors"
	"io"
	"strings"
)

// CardInfo 卡信息（ICCID + MSISDN）
type CardInfo struct {
	ICCID  string
	MSISDN string
}

// CSVParseResult CSV 解析结果
type CSVParseResult struct {
	Cards       []CardInfo
	TotalCount  int
	ParseErrors []CSVParseError
}

// CSVParseError CSV 解析错误
type CSVParseError struct {
	Line   int
	ICCID  string
	MSISDN string
	Reason string
}

// ErrInvalidCSVFormat CSV 格式错误
var ErrInvalidCSVFormat = errors.New("CSV 文件格式错误：缺少 MSISDN 列，文件必须包含 ICCID 和 MSISDN 两列")

// ParseCardCSV 解析包含 ICCID 和 MSISDN 两列的 CSV 文件
func ParseCardCSV(reader io.Reader) (*CSVParseResult, error) {
	csvReader := csv.NewReader(reader)
	csvReader.FieldsPerRecord = -1
	csvReader.TrimLeadingSpace = true

	result := &CSVParseResult{
		Cards:       make([]CardInfo, 0),
		ParseErrors: make([]CSVParseError, 0),
	}

	lineNum := 0
	headerSkipped := false

	for {
		record, err := csvReader.Read()
		if err == io.EOF {
			break
		}
		lineNum++

		if err != nil {
			result.ParseErrors = append(result.ParseErrors, CSVParseError{
				Line:   lineNum,
				Reason: "CSV 解析错误: " + err.Error(),
			})
			continue
		}

		if len(record) == 0 {
			continue
		}

		if len(record) < 2 {
			if lineNum == 1 && !headerSkipped {
				firstCol := strings.TrimSpace(record[0])
				if isICCIDHeader(firstCol) {
					return nil, ErrInvalidCSVFormat
				}
			}
			result.ParseErrors = append(result.ParseErrors, CSVParseError{
				Line:   lineNum,
				ICCID:  strings.TrimSpace(record[0]),
				Reason: "列数不足：缺少 MSISDN 列",
			})
			result.TotalCount++
			continue
		}

		iccid := strings.TrimSpace(record[0])
		msisdn := strings.TrimSpace(record[1])

		if lineNum == 1 && !headerSkipped && isHeader(iccid, msisdn) {
			headerSkipped = true
			continue
		}

		result.TotalCount++

		if iccid == "" {
			result.ParseErrors = append(result.ParseErrors, CSVParseError{
				Line:   lineNum,
				MSISDN: msisdn,
				Reason: "ICCID 不能为空",
			})
			continue
		}

		if msisdn == "" {
			result.ParseErrors = append(result.ParseErrors, CSVParseError{
				Line:   lineNum,
				ICCID:  iccid,
				Reason: "MSISDN 不能为空",
			})
			continue
		}

		result.Cards = append(result.Cards, CardInfo{
			ICCID:  iccid,
			MSISDN: msisdn,
		})
	}

	return result, nil
}

func isICCIDHeader(value string) bool {
	lower := strings.ToLower(value)
	return lower == "iccid" || lower == "卡号" || lower == "号码"
}

func isMSISDNHeader(value string) bool {
	lower := strings.ToLower(value)
	return lower == "msisdn" || lower == "接入号" || lower == "手机号" || lower == "电话" || lower == "号码"
}

func isHeader(col1, col2 string) bool {
	return isICCIDHeader(col1) && isMSISDNHeader(col2)
}