nicer plot

main_test.go

@@ -66,7 +66,7 @@ func TestHandleWriteStoresValue(t *testing.T) {
 
 func TestLoadConfig(t *testing.T) {
 	path := t.TempDir() + "/config.json"
-	if err := os.WriteFile(path, []byte(`{"write_secret":"secret","addr":":9090"}`), 0o600); err != nil {
+	if err := os.WriteFile(path, []byte(`{"write_secret":"secret","addr":":9090","chart_max_watts":750}`), 0o600); err != nil {
 		t.Fatalf("write config: %v", err)
 	}
 
@@ -80,10 +80,13 @@ func TestLoadConfig(t *testing.T) {
 	if cfg.Addr != ":9090" {
 		t.Fatalf("addr = %q, want %q", cfg.Addr, ":9090")
 	}
+	if cfg.ChartMaxWatts != 750 {
+		t.Fatalf("chart_max_watts = %d, want %d", cfg.ChartMaxWatts, 750)
+	}
 }
 
 func TestBuildHistoryChartEmpty(t *testing.T) {
-	chart := buildHistoryChart(nil)
+	chart := buildHistoryChart(nil, 0)
 	if !strings.Contains(string(chart), "No power history yet") {
 		t.Fatalf("empty chart did not contain fallback text: %s", string(chart))
 	}
@@ -96,7 +99,7 @@ func TestBuildHistoryChartRendersPolyline(t *testing.T) {
 		{at: time.Date(2026, 4, 20, 12, 0, 0, 0, time.UTC), value: 150},
 	}
 
-	chart := buildHistoryChart(history)
+	chart := buildHistoryChart(history, 0)
 	if !strings.Contains(string(chart), "<polyline") {
 		t.Fatalf("chart did not contain polyline: %s", string(chart))
 	}
@@ -109,3 +112,33 @@ func TestBuildHistoryChartRendersPolyline(t *testing.T) {
 		t.Fatalf("chart did not include zero baseline: %s", string(chart))
 	}
 }
+
+func TestBuildHistoryChartUsesConfiguredMax(t *testing.T) {
+	history := []sample{{at: time.Date(2026, 4, 20, 12, 0, 0, 0, time.UTC), value: 250}}
+	chart := buildHistoryChart(history, 1000)
+	if !strings.Contains(string(chart), "1000 W") {
+		t.Fatalf("chart did not include configured max: %s", string(chart))
+	}
+	if strings.Contains(string(chart), "250 W") {
+		t.Fatalf("chart unexpectedly used sample max instead of configured max: %s", string(chart))
+	}
+}
+
+func TestStoreTrimsHistoryToMaxPoints(t *testing.T) {
+	s := &store{}
+	base := time.Date(2026, 4, 20, 0, 0, 0, 0, time.UTC)
+	s.mu.Lock()
+	for i := 0; i < maxHistoryPoints+25; i++ {
+		s.history = append(s.history, sample{at: base.Add(time.Duration(i) * time.Second), value: i})
+	}
+	s.trimHistoryLocked(base.Add(time.Duration(maxHistoryPoints+25) * time.Second))
+	got := len(s.history)
+	s.mu.Unlock()
+
+	if got != maxHistoryPoints {
+		t.Fatalf("history length = %d, want %d", got, maxHistoryPoints)
+	}
+	if s.history[0].value != 25 {
+		t.Fatalf("oldest retained value = %d, want %d", s.history[0].value, 25)
+	}
+}