feat: idnorm and playlist support

idnorm.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"strings"
+	"unicode"
+)
+
+// Trailing dotted suffixes that EPG providers commonly append to channel ids
+// (e.g. "Italia 1.it"). Conservative allow-list to avoid eating real id chars.
+var idSuffixes = []string{".it", ".uk", ".de", ".com", ".us", ".fr", ".es", ".tv"}
+
+// Trailing video-quality markers commonly appended by either the playlist or
+// the EPG (e.g. open-epg uses "Italia 1 HD.it" while the playlist may say
+// "Italia 1"). Stripped symmetrically from both sides. Order matters: longer
+// markers first so " full hd" wins over a partial " hd" match.
+var qualitySuffixes = []string{" full hd", " uhd", " fhd", " hd", " 4k", " sd"}
+
+// normalizeChannelID returns a stable lookup key for a channel identifier,
+// collapsing cosmetic divergences across sources:
+//
+//	"Italia 1" / "Italia 1.it" / "Italia 1 HD.it" / "italia1" → "italia1"
+func normalizeChannelID(id string) string {
+	s := strings.ToLower(strings.TrimSpace(id))
+
+	for _, suf := range idSuffixes {
+		if strings.HasSuffix(s, suf) {
+			s = s[:len(s)-len(suf)]
+			break
+		}
+	}
+
+	// Strip trailing quality markers, possibly stacked ("Italia 1 Full HD HD").
+	for {
+		matched := false
+		for _, suf := range qualitySuffixes {
+			if strings.HasSuffix(s, suf) {
+				s = s[:len(s)-len(suf)]
+				matched = true
+				break
+			}
+		}
+		if !matched {
+			break
+		}
+	}
+
+	var b strings.Builder
+	b.Grow(len(s))
+	for _, r := range s {
+		if unicode.IsLetter(r) || unicode.IsDigit(r) {
+			b.WriteRune(r)
+		}
+	}
+	return b.String()
+}
+
+// buildIDMap turns a list of playlist tvg-ids into a normalized→canonical
+// lookup. The canonical form is the playlist's exact tvg-id string; the EPG
+// merger uses it to rewrite incoming channel/programme references.
+func buildIDMap(tvgIDs []string) map[string]string {
+	m := make(map[string]string, len(tvgIDs))
+	for _, id := range tvgIDs {
+		key := normalizeChannelID(id)
+		if key == "" {
+			continue
+		}
+		if _, exists := m[key]; !exists {
+			m[key] = id
+		}
+	}
+	return m
+}