fix: reject low-confidence automatic metadata matches

internal/service/metadata_match_trust.go

@@ -0,0 +1,98 @@
+package service
+
+import (
+	"regexp"
+	"strings"
+)
+
+var (
+	metadataTrustTokenRE           = regexp.MustCompile(`[\p{L}\p{N}]+`)
+	metadataTrustDanglingEpisodeRE = regexp.MustCompile(`(?i)^s\d{1,2}e$`)
+)
+
+func automaticMetadataTitleTrusted(query string, match *Match) bool {
+	queryKey := metadataTrustKey(query)
+	if queryKey == "" || match == nil {
+		return false
+	}
+	for _, title := range []string{match.Title, match.OriginalName} {
+		titleKey := metadataTrustKey(title)
+		if titleKey == "" {
+			continue
+		}
+		if queryKey == titleKey || metadataTrustTokenOverlap(queryKey, titleKey) {
+			return true
+		}
+	}
+	return false
+}
+
+func metadataTrustKey(value string) string {
+	value = strings.ToLower(strings.TrimSpace(value))
+	if value == "" {
+		return ""
+	}
+	value = bracketedTag.ReplaceAllString(value, " ")
+	value = yearPattern.ReplaceAllString(value, " ")
+	for _, re := range []*regexp.Regexp{patSEnE, patNxE, patEP, patCN, patSeasonOnly, patCNSeason} {
+		value = re.ReplaceAllString(value, " ")
+	}
+	tokens := metadataTrustTokenRE.FindAllString(value, -1)
+	out := make([]string, 0, len(tokens))
+	for _, token := range tokens {
+		token = strings.TrimSpace(token)
+		if token == "" || metadataTrustNoiseToken(token) {
+			continue
+		}
+		out = append(out, token)
+	}
+	return strings.Join(out, " ")
+}
+
+func metadataTrustNoiseToken(token string) bool {
+	if token == "x" || token == "×" {
+		return true
+	}
+	if _, ok := noiseTokenSet[token]; ok {
+		return true
+	}
+	if metadataTrustDanglingEpisodeRE.MatchString(token) {
+		return true
+	}
+	return false
+}
+
+func metadataTrustTokenOverlap(queryKey, titleKey string) bool {
+	queryTokens := metadataTrustSignificantTokens(queryKey)
+	titleTokens := metadataTrustSignificantTokens(titleKey)
+	if len(queryTokens) <= 1 || len(titleTokens) <= 1 {
+		return false
+	}
+	titleSet := make(map[string]struct{}, len(titleTokens))
+	for _, token := range titleTokens {
+		titleSet[token] = struct{}{}
+	}
+	overlap := 0
+	for _, token := range queryTokens {
+		if _, ok := titleSet[token]; ok {
+			overlap++
+		}
+	}
+	queryCoverage := float64(overlap) / float64(len(queryTokens))
+	titleCoverage := float64(overlap) / float64(len(titleTokens))
+	return queryCoverage >= 0.80 && titleCoverage >= 0.50
+}
+
+func metadataTrustSignificantTokens(key string) []string {
+	fields := strings.Fields(key)
+	out := make([]string, 0, len(fields))
+	for _, field := range fields {
+		switch field {
+		case "the", "a", "an", "of", "and":
+			continue
+		default:
+			out = append(out, field)
+		}
+	}
+	return out
+}