init

internal/classification/privacy.go

@@ -0,0 +1,104 @@
+package classification
+
+import (
+	"regexp"
+	"sort"
+	"strings"
+	"unicode"
+
+	"finance-duck/internal/domain"
+)
+
+var bankingPatterns = []*regexp.Regexp{
+	// Apply before tokenization to capture formatted identifiers as a unit.
+	regexp.MustCompile(`(?i)\b[a-z]{2}\s*\d{2}(?:[ -]?[a-z0-9]){11,30}\b`),
+	regexp.MustCompile(`(?i)\b[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\b`),
+	regexp.MustCompile(`(?i)\b(?:iban|bic|swift|account(?:\s*(?:number|no))?|konto(?:nummer)?|reference|ref|payment\s*(?:id|reference)|end\s*to\s*end(?:\s*id)?|e2e|eref|mref|kref|cred|mandate|mandat(?:sreferenz)?|kunden(?:nummer|referenz)|kreditornummer|glaeubiger\s*id|gläubiger\s*id)\b[^;\n|]*`),
+	regexp.MustCompile(`(?i)\b[A-Z]{6}[A-Z0-9]{2}(?:[A-Z0-9]{3})?\b`),
+	regexp.MustCompile(`(?i)\b(?:https?://|www\.)\S+|\b[^\s@]+@[^\s@]+\b`),
+}
+
+// No raw bank object is serialized. Known private values are removed from every
+// allowlisted text field; all digit-bearing tokens are additionally discarded.
+// This deliberately sacrifices numeric/BIC-shaped merchant names and reference-heavy text.
+// It is data minimization, not a guarantee of anonymization of arbitrary prose.
+func newSanitizer(facts domain.Facts, data domain.Dataset, publicMerchantLabels bool) func(string) string {
+	secrets := map[string]bool{}
+	publicNames := map[string]bool{}
+	if publicMerchantLabels {
+		for _, merchant := range data.Merchants {
+			publicNames[normalize(merchant.Name)] = true
+		}
+	}
+	add := func(value string) {
+		normalized := normalize(value)
+		if normalized != "" {
+			secrets[normalized] = true
+		}
+		for _, part := range strings.Fields(normalized) {
+			if len([]rune(part)) >= 2 {
+				secrets[part] = true
+			}
+		}
+	}
+	addFacts := func(f domain.Facts) {
+		add(f.ID)
+		add(f.Source)
+		add(f.AccountID)
+		add(f.ExternalID)
+		add(f.Fingerprint)
+		add(f.CounterpartyIBAN)
+		// This exception applies only to registered public merchant labels, never
+		// transaction prose or raw payee fields. Banking identifiers remain private.
+		if !publicNames[normalize(f.Counterparty)] {
+			add(f.Counterparty)
+		}
+	}
+	addFacts(facts)
+	for _, tx := range data.Transactions {
+		addFacts(tx.Facts)
+	}
+	for _, account := range data.Accounts {
+		add(account.ID)
+		add(account.ExternalAccountID)
+		add(account.IBAN)
+		add(account.DisplayName)
+		add(account.Institution)
+	}
+	values := make([]string, 0, len(secrets))
+	for value := range secrets {
+		values = append(values, value)
+	}
+	sort.Slice(values, func(i, j int) bool {
+		if len(values[i]) != len(values[j]) {
+			return len(values[i]) > len(values[j])
+		}
+		return values[i] < values[j]
+	})
+	return func(text string) string {
+		for _, pattern := range bankingPatterns {
+			text = pattern.ReplaceAllString(text, " ")
+		}
+		text = " " + normalize(text) + " "
+		for _, value := range values {
+			needle := " " + value + " "
+			for strings.Contains(text, needle) {
+				text = strings.ReplaceAll(text, needle, " ")
+			}
+		}
+		tokens := strings.Fields(text)
+		kept := make([]string, 0, len(tokens))
+		length := 0
+		for _, token := range tokens {
+			if strings.IndexFunc(token, unicode.IsDigit) >= 0 || len([]rune(token)) > 40 {
+				continue
+			}
+			if length+len(token) > 500 {
+				break
+			}
+			kept = append(kept, token)
+			length += len(token) + 1
+		}
+		return strings.Join(kept, " ")
+	}
+}