feat(radio): add ICY HTTP metadata reader

Closes #2

Signed-off-by: hiyukoim <11803292+hiyukoim@users.noreply.github.com>

core/radio/icy/reader.go

@@ -0,0 +1,55 @@
+package icy
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"strconv"
+)
+
+var ErrMissingMetaInt = errors.New("missing icy metadata interval")
+
+type ResponseStatusError struct {
+	StatusCode int
+	Status     string
+}
+
+func (e *ResponseStatusError) Error() string {
+	return fmt.Sprintf("icy stream returned %s", e.Status)
+}
+
+// ReadHTTPStreamTitles requests ICY metadata from streamURL and emits changed StreamTitle values.
+func ReadHTTPStreamTitles(ctx context.Context, client *http.Client, streamURL string, handleTitle func(string)) error {
+	if client == nil {
+		client = http.DefaultClient
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, streamURL, nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Icy-MetaData", "1")
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
+		return &ResponseStatusError{StatusCode: resp.StatusCode, Status: resp.Status}
+	}
+
+	metaIntHeader := resp.Header.Get("icy-metaint")
+	if metaIntHeader == "" {
+		return ErrMissingMetaInt
+	}
+
+	metaInt, err := strconv.Atoi(metaIntHeader)
+	if err != nil || metaInt <= 0 {
+		return fmt.Errorf("%w: %q", ErrInvalidMetaInt, metaIntHeader)
+	}
+
+	return ReadStreamTitles(ctx, resp.Body, metaInt, handleTitle)
+}

core/radio/icy/reader_test.go

@@ -0,0 +1,124 @@
+package icy
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("ReadHTTPStreamTitles", func() {
+	const metaInt = 5
+
+	It("requests ICY metadata and parses stream titles", func() {
+		var icyHeader string
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			icyHeader = r.Header.Get("Icy-MetaData")
+			w.Header().Set("icy-metaint", "5")
+			_, _ = w.Write(icyStream(metaInt, "StreamTitle='Artist - Title';"))
+		}))
+		defer server.Close()
+
+		var titles []string
+		err := ReadHTTPStreamTitles(context.Background(), server.Client(), server.URL, func(title string) {
+			titles = append(titles, title)
+		})
+
+		Expect(err).ToNot(HaveOccurred())
+		Expect(icyHeader).To(Equal("1"))
+		Expect(titles).To(Equal([]string{"Artist - Title"}))
+	})
+
+	It("follows redirects before reading stream metadata", func() {
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if r.URL.Path == "/redirect" {
+				http.Redirect(w, r, "/stream", http.StatusFound)
+				return
+			}
+
+			Expect(r.URL.Path).To(Equal("/stream"))
+			Expect(r.Header.Get("Icy-MetaData")).To(Equal("1"))
+			w.Header().Set("Icy-MetaInt", "5")
+			_, _ = w.Write(icyStream(metaInt, "StreamTitle='Redirected - Title';"))
+		}))
+		defer server.Close()
+
+		var titles []string
+		err := ReadHTTPStreamTitles(context.Background(), server.Client(), server.URL+"/redirect", func(title string) {
+			titles = append(titles, title)
+		})
+
+		Expect(err).ToNot(HaveOccurred())
+		Expect(titles).To(Equal([]string{"Redirected - Title"}))
+	})
+
+	It("returns an error when icy-metaint is missing", func() {
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			_, _ = w.Write([]byte("not an icy stream"))
+		}))
+		defer server.Close()
+
+		err := ReadHTTPStreamTitles(context.Background(), server.Client(), server.URL, func(string) {})
+
+		Expect(errors.Is(err, ErrMissingMetaInt)).To(BeTrue())
+	})
+
+	It("returns an error when icy-metaint is invalid", func() {
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("icy-metaint", "zero")
+			_, _ = w.Write([]byte("not an icy stream"))
+		}))
+		defer server.Close()
+
+		err := ReadHTTPStreamTitles(context.Background(), server.Client(), server.URL, func(string) {})
+
+		Expect(errors.Is(err, ErrInvalidMetaInt)).To(BeTrue())
+	})
+
+	It("returns response status errors for non-2xx responses", func() {
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			http.Error(w, "offline", http.StatusServiceUnavailable)
+		}))
+		defer server.Close()
+
+		err := ReadHTTPStreamTitles(context.Background(), server.Client(), server.URL, func(string) {})
+
+		var statusErr *ResponseStatusError
+		Expect(errors.As(err, &statusErr)).To(BeTrue())
+		Expect(statusErr.StatusCode).To(Equal(http.StatusServiceUnavailable))
+	})
+
+	It("stops when context is cancelled", func() {
+		ctx, cancel := context.WithCancel(context.Background())
+		cancel()
+
+		err := ReadHTTPStreamTitles(ctx, http.DefaultClient, "https://example.test/stream", func(string) {})
+
+		Expect(errors.Is(err, context.Canceled)).To(BeTrue())
+	})
+
+	It("stops a body read when context is cancelled", func() {
+		started := make(chan struct{})
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("icy-metaint", "5")
+			w.(http.Flusher).Flush()
+			close(started)
+			<-r.Context().Done()
+		}))
+		defer server.Close()
+
+		ctx, cancel := context.WithCancel(context.Background())
+		errC := make(chan error, 1)
+		go func() {
+			errC <- ReadHTTPStreamTitles(ctx, server.Client(), server.URL, func(string) {})
+		}()
+
+		Eventually(started).Should(BeClosed())
+		cancel()
+
+		Eventually(errC).Should(Receive(MatchError(ContainSubstring("context canceled"))))
+	})
+})