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-rw-r--r--bbc-on-ice.go253
1 files changed, 253 insertions, 0 deletions
diff --git a/bbc-on-ice.go b/bbc-on-ice.go
new file mode 100644
index 0000000..cf290d7
--- /dev/null
+++ b/bbc-on-ice.go
@@ -0,0 +1,253 @@
+package main
+
+import (
+ "encoding/json"
+ "errors"
+ "fmt"
+ "io"
+ "io/ioutil"
+ "log"
+ "net/http"
+ "os"
+ "path"
+ "regexp"
+ "strings"
+ "time"
+ "unicode/utf8"
+)
+
+type meta struct {
+ title string // What's playing right now
+ timeout uint // Timeout for the next poll in ms
+}
+
+// Retrieve and decode metadata information from an independent webservice
+func getMeta(name string) (*meta, error) {
+ const metaBaseURI = "http://polling.bbc.co.uk/radio/nhppolling/"
+ resp, err := http.Get(metaBaseURI + name)
+ if err != nil {
+ return nil, err
+ }
+ b, err := ioutil.ReadAll(resp.Body)
+ resp.Body.Close()
+ if len(b) < 2 {
+ // There needs to be an enclosing () pair
+ return nil, errors.New("invalid metadata response")
+ }
+
+ // TODO: also retrieve richtracks/is_now_playing, see example file
+ type broadcast struct {
+ Title string `json:"title"` // Title of the broadcast
+ Percentage int `json:"percentage"` // How far we're in
+ }
+ var v struct {
+ Packages struct {
+ OnAir struct {
+ Broadcasts []broadcast `json:"broadcasts"`
+ BroadcastNowIndex uint `json:"broadcastNowIndex"`
+ } `json:"on-air"`
+ } `json:"packages"`
+ Timeouts struct {
+ PollingTimeout uint `json:"polling_timeout"`
+ } `json:"timeouts"`
+ }
+ err = json.Unmarshal(b[1:len(b)-1], &v)
+ if err != nil {
+ return nil, errors.New("invalid metadata response")
+ }
+ onAir := v.Packages.OnAir
+ if onAir.BroadcastNowIndex >= uint(len(onAir.Broadcasts)) {
+ return nil, errors.New("no active broadcast")
+ }
+ return &meta{
+ timeout: v.Timeouts.PollingTimeout,
+ title: onAir.Broadcasts[onAir.BroadcastNowIndex].Title,
+ }, nil
+}
+
+// Resolve an M3U8 playlist to the first link that seems to be playable
+func resolveM3U8(target string) (out []string, err error) {
+ resp, err := http.Get(target)
+ if err != nil {
+ return nil, err
+ }
+ b, err := ioutil.ReadAll(resp.Body)
+ resp.Body.Close()
+ if !utf8.Valid(b) {
+ return nil, errors.New("invalid UTF-8")
+ }
+ lines := strings.Split(string(b), "\n")
+ for _, line := range lines {
+ if strings.HasPrefix(line, "#") {
+ continue
+ }
+ if !strings.Contains(line, "/") {
+ // Seems to be a relative link, let's make it absolute
+ dir, _ := path.Split(target)
+ line = dir + line
+ }
+ if strings.HasSuffix(line, "m3u8") {
+ // The playlist seems to recurse, and so do we
+ return resolveM3U8(line)
+ }
+ out = append(out, line)
+ }
+ return out, nil
+}
+
+var pathRE = regexp.MustCompile("^/(.*?)/(.*?)/(.*?)$")
+
+func proxy(w http.ResponseWriter, req *http.Request) {
+ const targetURI = "http://a.files.bbci.co.uk/media/live/manifesto/" +
+ "audio/simulcast/hls/%s/%s/ak/%s.m3u8"
+ const metaint = 1 << 16
+ m := pathRE.FindStringSubmatch(req.URL.Path)
+ if m == nil {
+ http.NotFound(w, req)
+ return
+ }
+ hijacker, ok := w.(http.Hijacker)
+ if !ok {
+ // We're not using TLS where HTTP/2 could have caused this
+ panic("cannot hijack connection")
+ }
+
+ // E.g. `nonuk`, `sbr_low` `bbc_radio_one`, or `uk`, `sbr_high`, `bbc_1xtra`
+ region, quality, name := m[1], m[2], m[3]
+ // This validates the params as a side-effect
+ target, err := resolveM3U8(fmt.Sprintf(targetURI, region, quality, name))
+ if err == nil && len(target) == 0 {
+ err = errors.New("cannot resolve playlist")
+ }
+ if err != nil {
+ http.Error(w, err.Error(), http.StatusInternalServerError)
+ return
+ }
+
+ wantMeta := false
+ if icyMeta, ok := req.Header["Icy-MetaData"]; ok {
+ wantMeta = len(icyMeta) == 1 && icyMeta[0] == "1"
+ }
+ resp, err := http.Get(target[0])
+ if err != nil {
+ http.Error(w, err.Error(), http.StatusInternalServerError)
+ return
+ }
+
+ conn, bufrw, err := hijacker.Hijack()
+ if err != nil {
+ http.Error(w, err.Error(), http.StatusInternalServerError)
+ return
+ }
+ defer conn.Close()
+
+ // TODO: retrieve some general information from somewhere?
+ // There's nothing interesting in the playlist files.
+ fmt.Fprintf(bufrw, "ICY 200 OK\r\n")
+ fmt.Fprintf(bufrw, "icy-name:%s\r\n", name)
+ // BBC marks this as a video type, maybe just force audio/mpeg
+ fmt.Fprintf(bufrw, "content-type:%s\r\n", resp.Header["Content-Type"][0])
+ fmt.Fprintf(bufrw, "icy-pub:%d\r\n", 0)
+ if wantMeta {
+ fmt.Fprintf(bufrw, "icy-metaint: %d\r\n", metaint)
+ }
+ fmt.Fprintf(bufrw, "\r\n")
+
+ // TODO: move to a normal function
+ metaChan := make(chan string)
+ go func() {
+ var current, last string
+ var interval time.Duration
+ for {
+ meta, err := getMeta(name)
+ if err != nil {
+ current = "Error: " + err.Error()
+ interval = 30 * time.Second
+ } else {
+ current = meta.title
+ interval = time.Duration(meta.timeout)
+ }
+ if current != last {
+ metaChan <- current
+ last = current
+ }
+
+ select {
+ case <-time.After(time.Duration(interval) * time.Millisecond):
+ case <-req.Context().Done():
+ return
+ }
+ }
+ }()
+
+ // TODO: move to a normal function
+ // FIXME: this will load a few seconds (one URL) and die
+ // - we can either try to implement this and hope for the best
+ // https://tools.ietf.org/html/draft-pantos-http-live-streaming-20
+ // then like https://github.com/kz26/gohls/blob/master/main.go
+ // - or we can become more of a proxy, which complicates ICY
+ chunkChan := make(chan []byte)
+ go func() {
+ defer resp.Body.Close()
+ defer close(chunkChan)
+ for {
+ chunk := make([]byte, metaint)
+ n, err := io.ReadFull(resp.Body, chunk)
+ chunkChan <- chunk[:n]
+ if err != nil {
+ return
+ }
+
+ select {
+ default:
+ case <-req.Context().Done():
+ return
+ }
+ }
+ }()
+
+ var queuedMeta []byte
+ makeMetaChunk := func() []byte {
+ meta := queuedMeta
+ queuedMeta = nil
+ for len(meta)%16 != 0 {
+ meta = append(meta, 0)
+ }
+ if len(meta) > 16*255 {
+ meta = meta[:16*255]
+ }
+ chunk := []byte{byte(len(meta) / 16)}
+ return append(chunk, meta...)
+ }
+
+ for {
+ select {
+ case title := <-metaChan:
+ queuedMeta = []byte(fmt.Sprintf("StreamTitle='%s'", title))
+ case chunk, connected := <-chunkChan:
+ if !connected {
+ return
+ }
+ if wantMeta {
+ chunk = append(chunk, makeMetaChunk()...)
+ }
+ if _, err := bufrw.Write(chunk); err != nil {
+ return
+ }
+ if err := bufrw.Flush(); err != nil {
+ return
+ }
+ }
+ }
+}
+
+func main() {
+ // TODO: also try to support systemd socket activation
+ address := ":8000"
+ if len(os.Args) == 2 {
+ address = os.Args[1]
+ }
+
+ http.HandleFunc("/", proxy)
+ log.Fatal(http.ListenAndServe(address, nil))
+}