feat: idnorm and playlist support

playlist.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"regexp"
+	"strings"
+)
+
+var (
+	tvgIDRe  = regexp.MustCompile(`tvg-id="([^"]*)"`)
+	urlTvgRe = regexp.MustCompile(`url-tvg="([^"]*)"`)
+)
+
+// processPlaylist streams in→out, rewriting the #EXTM3U header so url-tvg
+// points at epgURL. Returns the playlist's tvg-ids (in order, with duplicates)
+// and the URL the playlist already declared in url-tvg (empty if absent).
+//
+// If epgURL is empty the header is passed through unchanged. The playlist
+// must start with #EXTM3U after any leading blank lines, otherwise an error
+// is returned without writing the header.
+func processPlaylist(in io.Reader, out io.Writer, epgURL string) (tvgIDs []string, originalEPG string, err error) {
+	r := bufio.NewReader(in)
+	headerDone := false
+
+	for {
+		line, readErr := r.ReadString('\n')
+
+		if line != "" {
+			switch {
+			case !headerDone && strings.TrimSpace(line) == "":
+				// leading blank line — write through, keep looking for header
+
+			case !headerDone:
+				if !strings.HasPrefix(strings.TrimSpace(line), "#EXTM3U") {
+					return nil, "", errors.New("playlist: missing #EXTM3U header")
+				}
+				line, originalEPG = rewriteHeader(line, epgURL)
+				headerDone = true
+
+			default:
+				if strings.HasPrefix(line, "#EXTINF:") {
+					if m := tvgIDRe.FindStringSubmatch(line); m != nil {
+						if id := strings.TrimSpace(m[1]); id != "" {
+							tvgIDs = append(tvgIDs, id)
+						}
+					}
+				}
+			}
+
+			if _, werr := out.Write([]byte(line)); werr != nil {
+				return nil, "", werr
+			}
+		}
+
+		if readErr == io.EOF {
+			if !headerDone {
+				return nil, "", errors.New("playlist: missing #EXTM3U header")
+			}
+			return tvgIDs, originalEPG, nil
+		}
+		if readErr != nil {
+			return nil, "", readErr
+		}
+	}
+}
+
+func rewriteHeader(line, epgURL string) (rewritten, original string) {
+	if m := urlTvgRe.FindStringSubmatch(line); m != nil {
+		original = m[1]
+		if epgURL != "" {
+			line = urlTvgRe.ReplaceAllLiteralString(line, `url-tvg="`+epgURL+`"`)
+		}
+		return line, original
+	}
+	if epgURL == "" {
+		return line, ""
+	}
+	body, eol := splitEOL(line)
+	return body + ` url-tvg="` + epgURL + `"` + eol, ""
+}
+
+func splitEOL(s string) (body, eol string) {
+	n := len(s)
+	for n > 0 && (s[n-1] == '\n' || s[n-1] == '\r') {
+		n--
+	}
+	return s[:n], s[n:]
+}