init

2026-09-10 12:30:42 +02:00
commit 9843fe0c50
79 changed files with 16318 additions and 0 deletions
@@ -0,0 +1,212 @@
+package banking
+
+import (
+	"bufio"
+	"encoding/csv"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+	"unicode"
+
+	"finance-duck/internal/domain"
+)
+
+// ParseCSV accepts N26 English and German account-activity exports, including
+// their older Date/Datum and newer Booking Date/Buchungsdatum schemas. Supported
+// columns: Date/Datum/Booking Date/Buchungsdatum, Value Date/Wertstellung/
+// Wertstellungsdatum, Payee/Partner Name/Zahlungsempfänger/Empfänger/Auftraggeber,
+// Account number/Kontonummer/IBAN, Payment reference/Verwendungszweck,
+// Payment type/Transaktionstyp, Amount (EUR)/Betrag (EUR), and optional
+// Currency/Währung and Transaction ID/Transaktions-ID. Foreign-original-amount,
+// exchange-rate and category columns are deliberately not used for account money.
+// Comma and semicolon delimiters, UTF-8 BOM, CRLF, RFC4180 quoted multiline
+// descriptions, ISO and German dates, decimal comma and decimal point are accepted.
+// Missing required booking-date or account-amount columns fail the entire import.
+func ParseCSV(input io.Reader, account domain.Account) ([]domain.Facts, error) {
+	if account.ID == "" {
+		return nil, fmt.Errorf("CSV requires a selected account")
+	}
+	reader := bufio.NewReader(input)
+	first, err := reader.ReadString('\n')
+	if err != nil && err != io.EOF {
+		return nil, fmt.Errorf("read CSV header: %w", err)
+	}
+	first = strings.TrimPrefix(first, "\ufeff")
+	delimiter := ','
+	// Count separators outside quotes; descriptions may contain either delimiter.
+	quoted := false
+	commas, semicolons := 0, 0
+	for _, r := range first {
+		if r == '"' {
+			quoted = !quoted
+		}
+		if !quoted {
+			if r == ',' {
+				commas++
+			}
+			if r == ';' {
+				semicolons++
+			}
+		}
+	}
+	if semicolons > commas {
+		delimiter = ';'
+	}
+	parser := csv.NewReader(io.MultiReader(strings.NewReader(first), reader))
+	parser.Comma = delimiter
+	headers, err := parser.Read()
+	if err != nil {
+		return nil, fmt.Errorf("invalid N26 CSV header")
+	}
+	columns := make(map[string]int)
+	amountCurrency := ""
+	for i, h := range headers {
+		name := headerName(h)
+		key := ""
+		switch name {
+		case "date", "datum", "booking date", "buchungsdatum":
+			key = "date"
+		case "value date", "wertstellung", "wertstellungsdatum", "valutadatum":
+			key = "value"
+		case "payee", "partner name", "zahlungsempfänger", "zahlungsempfänger name", "empfänger", "empfänger/auftraggeber", "partnername", "name zahlungspartner":
+			key = "party"
+		case "account number", "partner iban", "kontonummer", "iban", "konto":
+			key = "iban"
+		case "payment reference", "verwendungszweck", "reference", "beschreibung":
+			key = "description"
+		case "payment type", "transaktionstyp", "zahlungstyp", "type", "typ":
+			key = "type"
+		case "currency", "währung":
+			key = "currency"
+		case "transaction id", "transaktions-id", "transaktions id":
+			key = "external"
+		case "amount", "betrag":
+			key = "amount"
+		default:
+			for _, prefix := range []string{"amount (", "betrag ("} {
+				if strings.HasPrefix(name, prefix) && strings.HasSuffix(name, ")") {
+					candidate := strings.ToUpper(strings.TrimSuffix(strings.TrimPrefix(name, prefix), ")"))
+					if validCurrency(candidate) {
+						key = "amount"
+						amountCurrency = candidate
+					}
+				}
+			}
+		}
+		if key != "" {
+			if _, exists := columns[key]; exists {
+				return nil, fmt.Errorf("duplicate N26 CSV column %s", key)
+			}
+			columns[key] = i
+		}
+	}
+	if _, ok := columns["date"]; !ok {
+		return nil, fmt.Errorf("N26 CSV requires Date/Datum or Booking Date/Buchungsdatum")
+	}
+	if _, ok := columns["amount"]; !ok {
+		return nil, fmt.Errorf("N26 CSV requires Amount (currency)/Betrag (currency)")
+	}
+	get := func(row []string, key string) string {
+		if i, ok := columns[key]; ok {
+			return strings.TrimSpace(row[i])
+		}
+		return ""
+	}
+	result := make([]domain.Facts, 0)
+	for rowNumber := 2; ; rowNumber++ {
+		row, err := parser.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, fmt.Errorf("invalid N26 CSV record %d", rowNumber)
+		}
+		date, err := parseDate(get(row, "date"))
+		if err != nil {
+			return nil, fmt.Errorf("invalid booking date in CSV record %d", rowNumber)
+		}
+		value := get(row, "value")
+		if value != "" {
+			value, err = parseDate(value)
+			if err != nil {
+				return nil, fmt.Errorf("invalid value date in CSV record %d", rowNumber)
+			}
+		}
+		amount, err := parseCSVAmount(get(row, "amount"))
+		if err != nil {
+			return nil, fmt.Errorf("invalid account amount in CSV record %d", rowNumber)
+		}
+		currency := strings.ToUpper(get(row, "currency"))
+		if currency == "" {
+			currency = amountCurrency
+		}
+		if currency == "" {
+			currency = strings.ToUpper(account.Currency)
+		}
+		if !validCurrency(currency) || (amountCurrency != "" && currency != amountCurrency) || (account.Currency != "" && currency != strings.ToUpper(account.Currency)) {
+			return nil, fmt.Errorf("invalid or conflicting account currency in CSV record %d", rowNumber)
+		}
+		description := get(row, "description")
+		if description == "" {
+			description = get(row, "type")
+		}
+		result = append(result, domain.Facts{Source: "n26_csv", AccountID: account.ID, BookingDate: date, ValueDate: value, Amount: amount, Currency: currency, RawDescription: description, ExternalID: get(row, "external"), Counterparty: get(row, "party"), CounterpartyIBAN: normalizeIBAN(get(row, "iban"))})
+	}
+	return result, nil
+}
+
+func headerName(s string) string {
+	return strings.ToLower(strings.Join(strings.Fields(strings.TrimPrefix(s, "\ufeff")), " "))
+}
+func normalizeIBAN(s string) string {
+	return strings.ToUpper(strings.Map(func(r rune) rune {
+		if unicode.IsSpace(r) {
+			return -1
+		}
+		return r
+	}, s))
+}
+func validCurrency(s string) bool {
+	if len(s) != 3 {
+		return false
+	}
+	for _, c := range s {
+		if c < 'A' || c > 'Z' {
+			return false
+		}
+	}
+	return true
+}
+func parseDate(s string) (string, error) {
+	for _, layout := range []string{"2006-01-02", "02.01.2006", "2.1.2006"} {
+		if d, e := time.Parse(layout, s); e == nil {
+			return d.Format("2006-01-02"), nil
+		}
+	}
+	return "", fmt.Errorf("invalid date")
+}
+func parseCSVAmount(s string) (domain.Money, error) {
+	s = strings.TrimPrefix(strings.TrimSpace(s), "+")
+	// German grouping is only accepted when every group is exactly three digits.
+	if strings.Contains(s, ",") {
+		if strings.Count(s, ",") != 1 {
+			return "", fmt.Errorf("invalid decimal separator")
+		}
+		pair := strings.SplitN(s, ",", 2)
+		if strings.Contains(pair[0], ".") {
+			groups := strings.Split(strings.TrimLeft(pair[0], "+-"), ".")
+			if len(groups[0]) < 1 || len(groups[0]) > 3 {
+				return "", fmt.Errorf("invalid grouping")
+			}
+			for _, g := range groups[1:] {
+				if len(g) != 3 {
+					return "", fmt.Errorf("invalid grouping")
+				}
+			}
+			pair[0] = strings.ReplaceAll(pair[0], ".", "")
+		}
+		s = pair[0] + "." + pair[1]
+	}
+	return domain.ParseMoney(s)
+}