fix(pdfamount): не считать ставку НДС суммой; итог DKV (#29)

- Строки с %/MwSt/USt/Prozent/Steuer больше не дают сумму (было: Storchen
  19,00 % -> amount 19.00 и ложная отбраковка кандидатов в матчере).
- Приоритет меток: zu zahlender betrag > rechnungsbetrag > rechnungsendbetrag
  > gesamtbetrag > gesamtsumme (inkl. Steuern); low-priority не перебивает.
- DKV: секция Gesamtsummenaufstellung (значение после «»») важнее повторяющихся
  TOTAL-строк по машинам.
- Тесты: 19,00 % не сумма; fallback на usable-метку; DKV-итог.

cmd/pdfamount/main.go

@@ -18,36 +18,52 @@ import (
 	onlyoffice "github.com/eslider/go-onlyoffice"
 )
 
-// amountLabels are the payable-amount labels in priority order: the first
-// label present in a document wins. Within one label the last amount is taken,
-// because totals usually come last.
-//
-// "gesamtsumme" is not in the original list but is the real label on Diashop
-// invoices: "Gesamtsumme (inkl. Steuern)".
-var amountLabels = []string{
-	"zu zahlender betrag",
-	"rechnungsbetrag",
-	"rechnungsendbetrag",
-	"endbetrag",
-	"zahlbetrag",
-	"bruttobetrag",
-	"gesamtbetrag",
-	"gesamtsumme",
-	"betrag",
-	"total",
-	"summe",
+// amountPat is the amount capture shared by every amount regex.
+const amountPat = `([0-9]+(?:[.,][0-9]+)*)`
+
+// amountRE builds "<label> [optional (comment)] [: -] <number>".
+func amountRE(label string) *regexp.Regexp {
+	return regexp.MustCompile(
+		`(?i)\b` + regexp.QuoteMeta(label) + `\b\s*(?:\([^)]*\))?\s*[:\-]?\s*` + amountPat)
 }
 
-// amountRes matches "<label> [optional (comment)] [: -] <number>" for every
-// label, in the same priority order as amountLabels.
-var amountRes = func() []*regexp.Regexp {
-	res := make([]*regexp.Regexp, 0, len(amountLabels))
-	for _, label := range amountLabels {
-		res = append(res, regexp.MustCompile(
-			`(?i)\b`+regexp.QuoteMeta(label)+`\b\s*(?:\([^)]*\))?\s*[:\-]?\s*([0-9]+(?:[.,][0-9]+)*)`))
-	}
-	return res
-}()
+// amountRes lists the payable-amount patterns in strict priority order: the
+// first pattern with a usable amount wins, and a lower-priority label can never
+// override a higher-priority one ("zu zahlender betrag" > "rechnungsbetrag" >
+// "rechnungsendbetrag" > "gesamtbetrag" > "gesamtsumme (inkl. steuern)").
+//
+// "gesamtbetrag" and "gesamtsumme" are not in the original set but are the real
+// labels on Diashop invoices ("Gesamtsumme (inkl. Steuern)"). The inclusive
+// variant is matched before a plain "gesamtsumme". Everything after those
+// primary labels is the broader fallback set, consulted only when no primary
+// label yields an amount. Within one pattern the last usable amount is taken,
+// because totals usually come last.
+var amountRes = []*regexp.Regexp{
+	amountRE("zu zahlender betrag"),
+	amountRE("rechnungsbetrag"),
+	amountRE("rechnungsendbetrag"),
+	amountRE("gesamtbetrag"),
+	regexp.MustCompile(`(?i)\bgesamtsumme\b\s*\(\s*inkl\.?\s*steuern\s*\)\s*[:\-]?\s*` + amountPat),
+	amountRE("gesamtsumme"),
+	amountRE("endbetrag"),
+	amountRE("zahlbetrag"),
+	amountRE("bruttobetrag"),
+	amountRE("betrag"),
+	amountRE("total"),
+	amountRE("summe"),
+}
+
+// taxLineRe marks a line whose number is a tax rate/percentage: an explicit
+// percent sign or a VAT/tax keyword. "Steuern" (plural, as in "inkl. Steuern")
+// is handled separately so the inclusive total stays usable.
+var taxLineRe = regexp.MustCompile(`(?i)%|\bMwSt\b|\bUSt\b|\bProzent\b`)
+
+// steuerRe finds "Steuer"/"Umsatzsteuer" etc. RE2 has no lookahead, so the
+// plural "Steuern" is excluded in isTaxLine.
+var steuerRe = regexp.MustCompile(`(?i)steuer`)
+
+// percentAfterRe detects a percent sign directly after a number (spaces ok).
+var percentAfterRe = regexp.MustCompile(`^\s*%`)
 
 func main() {
 	if len(os.Args) < 2 {
@@ -138,20 +154,116 @@ func pdfAmount(ctx context.Context, c *onlyoffice.Client, id string) (string, er
 }
 
 // extractAmount returns the normalised ("1234.56") payable amount found in
-// text, or "" if no known label matches.
+// text, or "" if no usable amount matches.
+//
+// DKV invoices are special-cased first: they repeat a per-vehicle "TOTAL:" line
+// and carry the real total only in the "Gesamtsummenaufstellung" section.
 func extractAmount(text string) string {
-	for _, re := range amountRes {
-		ms := re.FindAllStringSubmatch(text, -1)
-		if len(ms) == 0 {
-			continue
+	if v, ok := dkvGrandTotal(text); ok {
+		return v
 	}
-		if v, ok := normalizeAmount(ms[len(ms)-1][1]); ok {
+	for _, re := range amountRes {
+		if v, ok := lastUsableAmount(text, re); ok {
 			return v
 		}
 	}
 	return ""
 }
 
+// dkvGrandTotal extracts the total of a DKV "Gesamtsummenaufstellung" section.
+//
+// Rule: DKV invoices repeat a per-vehicle "TOTAL:" line, so the last TOTAL is
+// not the invoice total. When a "Gesamtsummenaufstellung" section exists, its
+// total wins over every "TOTAL:" line: the first amount after the "»" marker,
+// or, if there is none, the last amount in the section. The section ends at the
+// page break (form feed) or end of text.
+func dkvGrandTotal(text string) (string, bool) {
+	idx := strings.Index(strings.ToLower(text), "gesamtsummenaufstellung")
+	if idx < 0 {
+		return "", false
+	}
+	section := text[idx:]
+	if ff := strings.IndexByte(section, '\f'); ff >= 0 {
+		section = section[:ff]
+	}
+	if m := strings.Index(section, "»"); m >= 0 {
+		if v, ok := firstAmount(section[m:]); ok {
+			return v, true
+		}
+	}
+	return lastAmount(section)
+}
+
+// lastUsableAmount returns the last amount matched by re that is not a tax rate
+// or percentage. Within one label the last usable amount wins.
+func lastUsableAmount(text string, re *regexp.Regexp) (string, bool) {
+	ms := re.FindAllStringSubmatchIndex(text, -1)
+	for i := len(ms) - 1; i >= 0; i-- {
+		m := ms[i]
+		if isTaxRate(text, m[2], m[3]) {
+			continue
+		}
+		if v, ok := normalizeAmount(text[m[2]:m[3]]); ok {
+			return v, true
+		}
+	}
+	return "", false
+}
+
+// isTaxRate reports whether the number at text[start:end] is a tax rate or a
+// percentage instead of a payable amount. A candidate is rejected when the
+// token right after the number is "%" or the number's line carries a percent
+// sign or a tax keyword. Rejecting is deliberate: office matching treats a
+// known-but-different amount as a hard disqualifier, so an empty result is
+// safer than the VAT rate.
+func isTaxRate(text string, start, end int) bool {
+	if percentAfterRe.MatchString(text[end:]) {
+		return true
+	}
+	lineStart := strings.LastIndexByte(text[:start], '\n') + 1
+	line := text[lineStart:]
+	if n := strings.IndexByte(text[end:], '\n'); n >= 0 {
+		line = text[lineStart : end+n]
+	}
+	return isTaxLine(line)
+}
+
+// isTaxLine reports whether a line looks like a tax rate rather than a payable
+// amount. "Steuern" is treated as a qualifier ("inkl. Steuern"), not a rate.
+func isTaxLine(line string) bool {
+	if taxLineRe.MatchString(line) {
+		return true
+	}
+	for _, loc := range steuerRe.FindAllStringIndex(line, -1) {
+		if loc[1] >= len(line) || (line[loc[1]] != 'n' && line[loc[1]] != 'N') {
+			return true
+		}
+	}
+	return false
+}
+
+// numberRe finds bare numbers (with optional thousands/decimal separators).
+var numberRe = regexp.MustCompile(`[0-9]+(?:[.,][0-9]+)*`)
+
+func firstAmount(s string) (string, bool) {
+	for _, m := range numberRe.FindAllString(s, -1) {
+		if v, ok := normalizeAmount(m); ok {
+			return v, true
+		}
+	}
+	return "", false
+}
+
+func lastAmount(s string) (string, bool) {
+	ms := numberRe.FindAllString(s, -1)
+	for i := len(ms) - 1; i >= 0; i-- {
+		if v, ok := normalizeAmount(ms[i]); ok {
+			return v, true
+		}
+	}
+	return "", false
+}
+
 // normalizeAmount turns "1.234,56" (DE), "1,234.56" (EN) or "1234.56" into
 // "1234.56". The rightmost separator is decimal only when followed by one or
 // two digits; otherwise every separator is a thousands separator.

cmd/pdfamount/main_test.go

@@ -76,6 +76,51 @@ func TestExtractAmount(t *testing.T) {
 			text: "Kundenbezogene Daten\n» TOTAL: 123,45 100,00 23,45 123,45\n",
 			want: "123.45",
 		},
+		{
+			name: "dkv gesamtsummenaufstellung grand total after marker",
+			text: "» TOTAL: 111,11 100,00 11,11 111,11\n" +
+				"» TOTAL: 222,22 200,00 22,22 222,22\n" +
+				"Gesamtsummenaufstellung\n" +
+				"Netto 240,00\n" +
+				"MwSt 47,25\n" +
+				"» 287,25\n",
+			want: "287.25",
+		},
+		{
+			name: "dkv gesamtsummenaufstellung total on next line",
+			text: "» TOTAL: 111,11\nGesamtsummenaufstellung\n»\n287,25\n",
+			want: "287.25",
+		},
+		{
+			name: "tax rate with percent sign is not an amount",
+			text: "Betrag: 19,00 % MwSt",
+			want: "",
+		},
+		{
+			name: "mehrwertsteuer rate is not an amount",
+			text: "Gesamtsumme: 19,00% MwSt",
+			want: "",
+		},
+		{
+			name: "steuer word on the number line rejects it",
+			text: "Betrag: 2,83 Steuer",
+			want: "",
+		},
+		{
+			name: "rejected primary falls back to a usable label",
+			text: "Gesamtsumme: 19,00 % MwSt\nEndbetrag: 42,00",
+			want: "42.00",
+		},
+		{
+			name: "labeled zu zahlender betrag beats unlabeled larger number",
+			text: "unlabeled 999,99\nZu zahlender Betrag: 10,00",
+			want: "10.00",
+		},
+		{
+			name: "labeled zu zahlender betrag beats lower label larger number",
+			text: "Endbetrag: 999,99\nZu zahlender Betrag: 10,00",
+			want: "10.00",
+		},
 		{
 			name: "diashop style gesamtsumme with comment",
 			text: "Zwischensumme\n12,34 €\nZwischensumme\n12,34 €\nVersand & Bearbeitung\n4,95 €\nGesamtsumme (inkl. Steuern)\n17,29 €\n",