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third_party/sendspin-go/pkg/audio/decode/flac_integration_test.go

@@ -0,0 +1,157 @@
+// ABOUTME: Integration test for FLAC decoder using real FLAC files
+// ABOUTME: Skipped when no FLAC fixture is available
+package decode
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+
+	"github.com/Sendspin/sendspin-go/pkg/audio"
+	"github.com/mewkiz/flac"
+)
+
+// findFLACFixture looks for a FLAC test file in known locations.
+func findFLACFixture() string {
+	candidates := []string{
+		// conformance repo fixture (relative to pkg/audio/decode/)
+		"../../../conformance/repos/sendspin-cli/tests/fixtures/almost_silent.flac",
+		"../../../../conformance/repos/sendspin-cli/tests/fixtures/almost_silent.flac",
+		"../../../conformance/fixtures/almost-silent-5s-48000-2-24.flac",
+		"../../../../conformance/fixtures/almost-silent-5s-48000-2-24.flac",
+	}
+	for _, candidate := range candidates {
+		abs, err := filepath.Abs(candidate)
+		if err != nil {
+			continue
+		}
+		if _, err := os.Stat(abs); err == nil {
+			return abs
+		}
+	}
+	return ""
+}
+
+// splitFLACFile reads a FLAC file and returns the codec_header (fLaC +
+// all metadata blocks) and the raw frame data (everything after metadata).
+func splitFLACFile(path string) (codecHeader []byte, frameData []byte, sampleRate, channels, bitDepth int, totalSamples uint64, err error) {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return nil, nil, 0, 0, 0, 0, err
+	}
+	if len(raw) < 4 || string(raw[:4]) != "fLaC" {
+		return nil, nil, 0, 0, 0, 0, io.ErrUnexpectedEOF
+	}
+
+	// Parse metadata blocks to find where frame data starts.
+	offset := 4
+	for {
+		if offset+4 > len(raw) {
+			return nil, nil, 0, 0, 0, 0, io.ErrUnexpectedEOF
+		}
+		header := raw[offset : offset+4]
+		lastBlock := header[0]&0x80 != 0
+		blockLength := int(header[1])<<16 | int(header[2])<<8 | int(header[3])
+		offset += 4 + blockLength
+		if lastBlock {
+			break
+		}
+	}
+
+	codecHeader = make([]byte, offset)
+	copy(codecHeader, raw[:offset])
+
+	// Get stream info for verification
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, nil, 0, 0, 0, 0, err
+	}
+	defer f.Close()
+	stream, err := flac.New(f)
+	if err != nil {
+		return nil, nil, 0, 0, 0, 0, err
+	}
+
+	return codecHeader, raw[offset:], int(stream.Info.SampleRate), int(stream.Info.NChannels), int(stream.Info.BitsPerSample), stream.Info.NSamples, nil
+}
+
+func TestFLACDecoder_RealFile(t *testing.T) {
+	fixturePath := findFLACFixture()
+	if fixturePath == "" {
+		t.Skip("no FLAC fixture found — skipping integration test")
+	}
+
+	codecHeader, frameData, sampleRate, channels, bitDepth, totalSamples, err := splitFLACFile(fixturePath)
+	if err != nil {
+		t.Fatalf("splitFLACFile: %v", err)
+	}
+
+	t.Logf("Fixture: %s", filepath.Base(fixturePath))
+	t.Logf("Format: %dHz %dch %dbit, %d total samples", sampleRate, channels, bitDepth, totalSamples)
+	t.Logf("Codec header: %d bytes, frame data: %d bytes", len(codecHeader), len(frameData))
+
+	format := audio.Format{
+		Codec:       "flac",
+		SampleRate:  sampleRate,
+		Channels:    channels,
+		BitDepth:    bitDepth,
+		CodecHeader: codecHeader,
+	}
+
+	dec, err := NewFLAC(format)
+	if err != nil {
+		t.Fatalf("NewFLAC: %v", err)
+	}
+
+	// The FLACDecoder uses an io.Pipe internally: Decode() writes to the
+	// pipe then drains decoded samples from a channel. With a full file's
+	// worth of frame data, the internal sample channel (buffer 16) fills
+	// before the pipe write completes, causing deadlock in a single
+	// goroutine. To test the full pipeline we access the unexported fields
+	// directly: write frame data to the pipe from a goroutine, then
+	// collect decoded samples from the channel until it closes.
+	flacDec := dec.(*FLACDecoder)
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, writeErr := flacDec.pipeWriter.Write(frameData)
+		if writeErr != nil {
+			t.Errorf("pipe write: %v", writeErr)
+		}
+		// Close the writer so the decoder sees EOF and stops.
+		flacDec.pipeWriter.Close()
+	}()
+
+	var allSamples []int32
+	for samples := range flacDec.sampleCh {
+		allSamples = append(allSamples, samples...)
+	}
+
+	wg.Wait()
+
+	if len(allSamples) == 0 {
+		t.Fatal("expected decoded samples, got empty")
+	}
+
+	expectedSamples := int(totalSamples) * channels
+	t.Logf("Decoded %d samples (expected ~%d)", len(allSamples), expectedSamples)
+
+	// Verify sample count is in the right ballpark.
+	if len(allSamples) < expectedSamples/2 {
+		t.Errorf("decoded far fewer samples than expected: %d vs %d", len(allSamples), expectedSamples)
+	}
+
+	// Verify samples aren't all zero (sanity check — the fixture is
+	// "almost silent" but should have some non-zero values).
+	nonZero := 0
+	for _, s := range allSamples {
+		if s != 0 {
+			nonZero++
+		}
+	}
+	t.Logf("Non-zero samples: %d / %d", nonZero, len(allSamples))
+}