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third_party/sendspin-go/pkg/sendspin/source.go

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+// ABOUTME: Audio source abstraction for Sendspin streaming
+// ABOUTME: Provides AudioSource interface and common implementations
+package sendspin
+
+import (
+	"fmt"
+	"math"
+	"sync"
+)
+
+// AudioSource provides PCM audio samples for streaming
+type AudioSource interface {
+	// Read reads PCM samples into the buffer (int32 for 24-bit support).
+	// Returns number of samples read or error.
+	Read(samples []int32) (int, error)
+
+	// SampleRate returns the sample rate of the audio
+	SampleRate() int
+
+	// Channels returns the number of channels
+	Channels() int
+
+	// Metadata returns title, artist, album
+	Metadata() (title, artist, album string)
+
+	// Close closes the audio source
+	Close() error
+}
+
+type TestToneSource struct {
+	sampleIndex uint64
+	sampleMu    sync.Mutex
+	frequency   float64
+	sampleRate  int
+	channels    int
+}
+
+// NewTestTone creates a new test tone generator
+// Generates a 440Hz sine wave at the specified sample rate and channels
+func NewTestTone(sampleRate, channels int) *TestToneSource {
+	if sampleRate == 0 {
+		sampleRate = DefaultSampleRate
+	}
+	if channels == 0 {
+		channels = DefaultChannels
+	}
+
+	return &TestToneSource{
+		frequency:  440.0, // A4 note
+		sampleRate: sampleRate,
+		channels:   channels,
+	}
+}
+
+func (s *TestToneSource) Read(samples []int32) (int, error) {
+	s.sampleMu.Lock()
+	defer s.sampleMu.Unlock()
+
+	numSamples := len(samples) / s.channels
+
+	for i := 0; i < numSamples; i++ {
+		t := float64(s.sampleIndex+uint64(i)) / float64(s.sampleRate)
+		sample := math.Sin(2 * math.Pi * s.frequency * t)
+
+		// Scale to 24-bit range; 50% amplitude avoids clipping on decode
+		const max24bit = 8388607 // 2^23 - 1
+		pcmValue := int32(sample * max24bit * 0.5)
+
+		for ch := 0; ch < s.channels; ch++ {
+			samples[i*s.channels+ch] = pcmValue
+		}
+	}
+
+	s.sampleIndex += uint64(numSamples)
+
+	return len(samples), nil
+}
+
+func (s *TestToneSource) SampleRate() int { return s.sampleRate }
+func (s *TestToneSource) Channels() int   { return s.channels }
+func (s *TestToneSource) Metadata() (string, string, string) {
+	return "Test Tone", "Sendspin", "Test Signal"
+}
+func (s *TestToneSource) Close() error { return nil }
+
+// FileSource streams audio from a file
+// Note: This is a placeholder - users should use server.NewAudioSource() for file streaming
+// which supports MP3, FLAC, and other formats
+type FileSource struct {
+	// This is intentionally not implemented in the public API yet
+	// Users can use internal/server.NewAudioSource() for now
+	// TODO: Move file source implementations to pkg/audio/decode
+}
+
+// NewFileSource creates an audio source from a file
+// Supported formats: MP3, FLAC
+// Returns an error if the file cannot be opened or decoded
+func NewFileSource(path string) (AudioSource, error) {
+	// For now, we use the internal implementation
+	// TODO: Migrate file sources to pkg/audio/decode
+	return nil, fmt.Errorf("file source not implemented: use internal/server.NewAudioSource()")
+}