Improving all side of app

internal/datasource/synthetic/timestamp_test.go

@@ -0,0 +1,154 @@
+package synthetic
+
+import (
+	"context"
+	"log/slog"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// seqSource is a test DataSource that emits a fixed sequence of values, each
+// carrying its own timestamp, so tests can control upstream sample times.
+type seqSource struct {
+	name string
+	seq  []datasource.Value
+}
+
+func (s *seqSource) Name() string                                          { return s.name }
+func (s *seqSource) Connect(context.Context) error                         { return nil }
+func (s *seqSource) ListSignals(context.Context) ([]datasource.Metadata, error) { return nil, nil }
+func (s *seqSource) GetMetadata(context.Context, string) (datasource.Metadata, error) {
+	return datasource.Metadata{Name: "x", Type: datasource.TypeFloat64}, nil
+}
+func (s *seqSource) Write(context.Context, string, any) error { return datasource.ErrNotWritable }
+func (s *seqSource) History(context.Context, string, time.Time, time.Time, int) ([]datasource.Value, error) {
+	return nil, datasource.ErrHistoryUnavailable
+}
+func (s *seqSource) Subscribe(ctx context.Context, _ string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
+	go func() {
+		for _, v := range s.seq {
+			select {
+			case ch <- v:
+			case <-ctx.Done():
+				return
+			}
+			time.Sleep(8 * time.Millisecond)
+		}
+	}()
+	return func() {}, nil
+}
+
+// TestSubscribePreservesUpstreamTimestamp verifies a single-source synthetic
+// emits each computed value with the upstream sample's timestamp.
+func TestSubscribePreservesUpstreamTimestamp(t *testing.T) {
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	base := time.Date(2026, 6, 19, 10, 0, 0, 0, time.UTC)
+	src := &seqSource{name: "src", seq: []datasource.Value{
+		{Timestamp: base.Add(1 * time.Second), Data: 1.0, Quality: datasource.QualityGood},
+		{Timestamp: base.Add(2 * time.Second), Data: 2.0, Quality: datasource.QualityGood},
+		{Timestamp: base.Add(3 * time.Second), Data: 3.0, Quality: datasource.QualityGood},
+	}}
+
+	brk := broker.New(ctx, log)
+	brk.Register(src)
+	syn := New(t.TempDir(), brk, log)
+	if err := syn.Connect(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if err := syn.AddSignal(SignalDef{
+		Name: "g", DS: "src", Signal: "x",
+		Pipeline: []NodeDef{{Type: "gain", Params: map[string]any{"gain": 10.0}}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	ch := make(chan datasource.Value, 8)
+	if _, err := syn.Subscribe(ctx, "g", ch); err != nil {
+		t.Fatal(err)
+	}
+
+	want := []time.Time{base.Add(1 * time.Second), base.Add(2 * time.Second), base.Add(3 * time.Second)}
+	for i, w := range want {
+		select {
+		case v := <-ch:
+			if !v.Timestamp.Equal(w) {
+				t.Errorf("emit #%d timestamp: want %s, got %s", i, w, v.Timestamp)
+			}
+		case <-time.After(2 * time.Second):
+			t.Fatalf("timeout waiting for emit #%d", i)
+		}
+	}
+}
+
+// TestSubscribeMultiSourceUsesLatestTimestamp verifies that a synthetic combining
+// two independent sources stamps each output with the MOST RECENT contributing
+// sample time — not the timestamp of whichever source happened to trigger the
+// computation. A slow source carrying a stale timestamp must not drag the output
+// backwards in time (which previously produced wrong/non-monotonic plot points).
+func TestSubscribeMultiSourceUsesLatestTimestamp(t *testing.T) {
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	now := time.Date(2026, 6, 19, 12, 0, 0, 0, time.UTC)
+	// Fast source A with current timestamps.
+	a := &seqSource{name: "A", seq: []datasource.Value{
+		{Timestamp: now.Add(10 * time.Second), Data: 1.0, Quality: datasource.QualityGood},
+		{Timestamp: now.Add(11 * time.Second), Data: 2.0, Quality: datasource.QualityGood},
+		{Timestamp: now.Add(12 * time.Second), Data: 3.0, Quality: datasource.QualityGood},
+		{Timestamp: now.Add(13 * time.Second), Data: 4.0, Quality: datasource.QualityGood},
+	}}
+	// Slow source B: a single sample with a much older timestamp.
+	b := &seqSource{name: "B", seq: []datasource.Value{
+		{Timestamp: now.Add(1 * time.Second), Data: 100.0, Quality: datasource.QualityGood},
+	}}
+
+	brk := broker.New(ctx, log)
+	brk.Register(a)
+	brk.Register(b)
+	syn := New(t.TempDir(), brk, log)
+	if err := syn.Connect(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if err := syn.AddSignal(SignalDef{
+		Name: "diff",
+		Graph: &Graph{Output: "out", Nodes: []GraphNode{
+			{ID: "sa", Kind: "source", DS: "A", Signal: "x"},
+			{ID: "sb", Kind: "source", DS: "B", Signal: "x"},
+			{ID: "sub", Kind: "op", Op: "subtract", Inputs: []string{"sa", "sb"}},
+			{ID: "out", Kind: "output", Inputs: []string{"sub"}},
+		}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	ch := make(chan datasource.Value, 16)
+	if _, err := syn.Subscribe(ctx, "diff", ch); err != nil {
+		t.Fatal(err)
+	}
+
+	var last time.Time
+	for i := 0; i < 4; i++ {
+		select {
+		case v := <-ch:
+			// The stale source-B timestamp (t=1s) must never be used: every output
+			// is stamped with the newest input time, so emits stay monotonic.
+			if v.Timestamp.Equal(now.Add(1 * time.Second)) {
+				t.Errorf("emit #%d used the stale source-B timestamp %s", i, v.Timestamp)
+			}
+			if !last.IsZero() && v.Timestamp.Before(last) {
+				t.Errorf("emit #%d went backwards: %s before previous %s", i, v.Timestamp, last)
+			}
+			last = v.Timestamp
+		case <-time.After(2 * time.Second):
+			t.Fatalf("timeout waiting for emit #%d", i)
+		}
+	}
+}