From 248c489a368754ac217613f742b1dc283f4f3d6f Mon Sep 17 00:00:00 2001
From: hermes <hermes@obahan.xyz>
Date: Wed, 30 Sep 2026 21:59:33 +0200
Subject: [PATCH] add internal/infra/icecast.go

---
 internal/infra/icecast.go | 119 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 internal/infra/icecast.go

diff --git a/internal/infra/icecast.go b/internal/infra/icecast.go
new file mode 100644
index 0000000..d09bfda
--- /dev/null
+++ b/internal/infra/icecast.go
@@ -0,0 +1,119 @@
+package infra
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"time"
+)
+
+// Icecast source-protocol client (SOURCE command, HTTP/1.0 style headers).
+// Spec: Icecast 2 docs, "Source Protocol". The source authenticates with the
+// source password, then writes raw MP3 bytes forever.
+
+// SourceMeta describes the stream to the icecast server.
+type SourceMeta struct {
+	Mount       string // mount point, e.g. "/ai-radio.mp3"
+	Name        string // stream name shown in the directory
+	Genre       string
+	Bitrate     string // kbps, informational
+	URL         string
+	Description string
+}
+
+// buildSourceRequest renders the SOURCE handshake request.
+func buildSourceRequest(password string, m SourceMeta) string {
+	h := []string{
+		"SOURCE " + password,
+		"ice-name: " + m.Name,
+		"ice-genre: " + m.Genre,
+		"ice-bitrate: " + m.Bitrate,
+		"ice-public: 1",
+		"ice-description: " + m.Description,
+		"ice-url: " + m.URL,
+		"content-type: audio/mpeg",
+		"mount: " + m.Mount,
+	}
+	return strings.Join(h, "\r\n") + "\r\n\r\n"
+}
+
+// parseSourceResponse inspects the first status line of the handshake reply.
+func parseSourceResponse(resp string) (bool, string) {
+	line := strings.SplitN(strings.TrimSpace(resp), "\r\n", 2)[0]
+	if strings.Contains(line, " 200") {
+		return true, line
+	}
+	return false, line
+}
+
+// IcecastSource connects and streams. Reconnection is the caller's job
+// (the streamer loop handles it).
+type IcecastSource struct {
+	Addr     string // host:port
+	Password string
+	Meta     SourceMeta
+}
+
+// Connect performs the SOURCE handshake and returns the live connection.
+// Every subsequent Write goes straight to listeners.
+func (s *IcecastSource) Connect() (net.Conn, error) {
+	conn, err := net.DialTimeout("tcp", s.Addr, 10*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("icecast dial %s: %w", s.Addr, err)
+	}
+	if _, err := conn.Write([]byte(buildSourceRequest(s.Password, s.Meta))); err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("icecast handshake write: %w", err)
+	}
+	_ = conn.SetReadDeadline(time.Now().Add(10 * time.Second))
+	br := bufio.NewReader(conn)
+	status, err := br.ReadString('\n')
+	if err != nil && status == "" {
+		conn.Close()
+		return nil, fmt.Errorf("icecast handshake read: %w", err)
+	}
+	// drain remaining headers
+	for {
+		l, err := br.ReadString('\n')
+		if err != nil || strings.TrimSpace(l) == "" {
+			break
+		}
+	}
+	ok, line := parseSourceResponse(status)
+	if !ok {
+		conn.Close()
+		return nil, fmt.Errorf("icecast rejected source: %s", line)
+	}
+	return conn, nil
+}
+
+// StreamFile sends one MP3 file paced in real time (bytes/sec ≈ bitrate).
+// Pacing keeps icecast's buffer healthy; too fast overflows, too slow starves.
+func StreamFile(w io.Writer, r io.Reader, kbps int) (int64, error) {
+	const chunk = 4096
+	bytesPerSec := int64(kbps) * 1000 / 8
+	buf := make([]byte, chunk)
+	start := time.Now()
+	var sent int64
+	for {
+		n, rerr := r.Read(buf)
+		if n > 0 {
+			if _, werr := w.Write(buf[:n]); werr != nil {
+				return sent, werr
+			}
+			sent += int64(n)
+			lead := float64(sent)/float64(bytesPerSec) - time.Since(start).Seconds()
+			if lead > 0.05 {
+				time.Sleep(time.Duration(lead*float64(time.Second)) / 2)
+			}
+		}
+		if rerr != nil {
+			if rerr == io.EOF {
+				return sent, nil
+			}
+			return sent, rerr
+		}
+	}
+}