fm-rds-tx/internal/offline/generator_test.go

package offline

import (
	"math"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	cfgpkg "github.com/jan/fm-rds-tx/internal/config"
)

func TestGenerateFrame(t *testing.T) {
	g := NewGenerator(cfgpkg.Default())
	frame := g.GenerateFrame(50 * time.Millisecond)
	if frame == nil || len(frame.Samples) == 0 { t.Fatal("expected samples") }
}

func TestGenerateFrameFMIQ(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.FM.FMModulationEnabled = true
	frame := NewGenerator(cfg).GenerateFrame(10 * time.Millisecond)
	for i := 100; i < len(frame.Samples) && i < 200; i++ {
		s := frame.Samples[i]
		mag := math.Sqrt(float64(s.I)*float64(s.I) + float64(s.Q)*float64(s.Q))
		if math.Abs(mag-1.0) > 0.01 { t.Fatalf("sample %d: mag=%.4f", i, mag) }
	}
}

func TestGenerateFrameCompositeOnly(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.FM.FMModulationEnabled = false
	frame := NewGenerator(cfg).GenerateFrame(10 * time.Millisecond)
	for i := 0; i < len(frame.Samples) && i < 100; i++ {
		if frame.Samples[i].Q != 0 { t.Fatalf("sample %d: Q=%.6f", i, frame.Samples[i].Q) }
	}
}

func TestStereoDisabled(t *testing.T) {
	cfgS := cfgpkg.Default(); cfgS.FM.FMModulationEnabled = false; cfgS.FM.StereoEnabled = true
	cfgM := cfgS; cfgM.FM.StereoEnabled = false
	sf := NewGenerator(cfgS).GenerateFrame(20 * time.Millisecond)
	mf := NewGenerator(cfgM).GenerateFrame(20 * time.Millisecond)
	var diffEnergy float64
	for i := range sf.Samples {
		d := float64(sf.Samples[i].I - mf.Samples[i].I); diffEnergy += d * d
	}
	if diffEnergy == 0 { t.Fatal("expected difference") }
}

func TestWriteFile(t *testing.T) {
	cfg := cfgpkg.Default()
	out := filepath.Join(t.TempDir(), "test.iqf32")
	if err := NewGenerator(cfg).WriteFile(out, 20*time.Millisecond); err != nil { t.Fatal(err) }
	info, _ := os.Stat(out)
	if info.Size() == 0 { t.Fatal("empty file") }
}

func TestSummaryTones(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.Audio.InputPath = ""
	s := NewGenerator(cfg).Summary(10 * time.Millisecond)
	if !strings.Contains(s, "source=tones") { t.Fatalf("unexpected: %s", s) }
}

func TestSummaryToneFallback(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.Audio.InputPath = "missing.wav"
	s := NewGenerator(cfg).Summary(10 * time.Millisecond)
	if !strings.Contains(s, "source=tone-fallback") { t.Fatalf("unexpected: %s", s) }
}

func TestSummaryPreemph(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.FM.PreEmphasisTauUS = 50
	if !strings.Contains(NewGenerator(cfg).Summary(10*time.Millisecond), "preemph=50µs") { t.Fatal("missing preemph") }
}

func TestSummaryFMIQ(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.FM.FMModulationEnabled = true
	if !strings.Contains(NewGenerator(cfg).Summary(10*time.Millisecond), "FM-IQ") { t.Fatal("missing FM-IQ") }
}

func TestLimiterPreventsClipping(t *testing.T) {
	cfg := cfgpkg.Default()
	cfg.FM.LimiterEnabled = true; cfg.FM.LimiterCeiling = 1.0
	cfg.FM.FMModulationEnabled = false
	cfg.Audio.ToneAmplitude = 0.9; cfg.Audio.Gain = 2.0; cfg.FM.OutputDrive = 1.0
	frame := NewGenerator(cfg).GenerateFrame(50 * time.Millisecond)
	// Total composite (audio + pilot + RDS) should stay within ceiling.
	// Audio ceiling is auto-reduced to leave headroom for pilot + RDS.
	maxAllowed := cfg.FM.LimiterCeiling + 0.02 // small tolerance for limiter settling
	for i, s := range frame.Samples {
		if math.Abs(float64(s.I)) > maxAllowed { t.Fatalf("sample %d: %.4f exceeds max %.4f", i, s.I, maxAllowed) }
	}
}

// --- Operator truth tests ---

func TestRDSDisabledSuppressesRDSEnergy(t *testing.T) {
	cfgOn := cfgpkg.Default(); cfgOn.FM.FMModulationEnabled = false; cfgOn.RDS.Enabled = true
	cfgOff := cfgOn; cfgOff.RDS.Enabled = false
	fOn := NewGenerator(cfgOn).GenerateFrame(20 * time.Millisecond)
	fOff := NewGenerator(cfgOff).GenerateFrame(20 * time.Millisecond)
	var diff float64
	for i := range fOn.Samples {
		d := float64(fOn.Samples[i].I - fOff.Samples[i].I); diff += d * d
	}
	if diff == 0 { t.Fatal("rds.enabled=false should produce different output") }
}

func TestFMModDisabledMeansComposite(t *testing.T) {
	cfg := cfgpkg.Default(); cfg.FM.FMModulationEnabled = false
	frame := NewGenerator(cfg).GenerateFrame(10 * time.Millisecond)
	for i := 0; i < 100; i++ {
		if frame.Samples[i].Q != 0 { t.Fatal("Q should be 0 when FM mod is off") }
	}
}

func TestLimiterDisabledAllowsHigherPeaks(t *testing.T) {
	base := cfgpkg.Default()
	base.FM.FMModulationEnabled = false
	base.Audio.ToneAmplitude = 0.9; base.Audio.Gain = 2.0; base.FM.OutputDrive = 1.0

	cfgLim := base; cfgLim.FM.LimiterEnabled = true; cfgLim.FM.LimiterCeiling = 1.0
	cfgNoLim := base; cfgNoLim.FM.LimiterEnabled = false

	fLim := NewGenerator(cfgLim).GenerateFrame(50 * time.Millisecond)
	fNoLim := NewGenerator(cfgNoLim).GenerateFrame(50 * time.Millisecond)

	var maxLim, maxNoLim float64
	for _, s := range fLim.Samples { if math.Abs(float64(s.I)) > maxLim { maxLim = math.Abs(float64(s.I)) } }
	for _, s := range fNoLim.Samples { if math.Abs(float64(s.I)) > maxNoLim { maxNoLim = math.Abs(float64(s.I)) } }

	if maxNoLim <= maxLim { t.Fatalf("limiter disabled should allow higher peaks: lim=%.4f nolim=%.4f", maxLim, maxNoLim) }
}