feat: add disk I/O stats (read/write throughput bars, hotkey 5, auto-scale)

Add a new disk stats category that reads /proc/diskstats, shows read/write
throughput as colored bars (purple/darker purple like network RX/TX), with
optional utilization % overlay in extended mode. Hotkey 5 cycles: aggregate
(sum all whole-disk devices) → per-device → off. Auto-scale with decay and
optional fixed override via --diskmax / diskmax config key.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/internal/app/store_test.go b/internal/app/store_test.go
new file mode 100644
index 0000000..037d7d4
--- /dev/null
+++ b/internal/app/store_test.go
@@ -0,0 +1,71 @@
+package app
+
+import (
+	"testing"
+
+	"codeberg.org/snonux/loadbars/internal/collector"
+	"codeberg.org/snonux/loadbars/internal/stats"
+)
+
+func TestSetDisk(t *testing.T) {
+	s := NewStore()
+	disk := collector.DiskLine{
+		Device:       "sda",
+		SectorsRead:  1000,
+		SectorsWrite: 2000,
+		IoTicks:      50,
+	}
+	s.SetDisk("host1", "sda", disk, 1.0)
+
+	snap := s.Snapshot()
+	h := snap["host1"]
+	if h == nil {
+		t.Fatal("expected host1 in snapshot")
+	}
+	ds, ok := h.Disk["sda"]
+	if !ok {
+		t.Fatal("expected sda in Disk map")
+	}
+	if ds.SectorsRead != 1000 || ds.SectorsWrite != 2000 || ds.IoTicks != 50 || ds.Stamp != 1.0 {
+		t.Errorf("disk stamp mismatch: got %+v", ds)
+	}
+}
+
+func TestSnapshotDiskDeepCopy(t *testing.T) {
+	s := NewStore()
+	disk := collector.DiskLine{
+		Device:       "sda",
+		SectorsRead:  100,
+		SectorsWrite: 200,
+	}
+	s.SetDisk("host1", "sda", disk, 1.0)
+
+	snap1 := s.Snapshot()
+
+	// Mutate the store after snapshot
+	disk2 := collector.DiskLine{
+		Device:       "sda",
+		SectorsRead:  999,
+		SectorsWrite: 888,
+	}
+	s.SetDisk("host1", "sda", disk2, 2.0)
+
+	// snap1 should be unchanged (deep copy)
+	ds := snap1["host1"].Disk["sda"]
+	if ds.SectorsRead != 100 || ds.SectorsWrite != 200 {
+		t.Errorf("snapshot was mutated: got sr=%d sw=%d, want sr=100 sw=200",
+			ds.SectorsRead, ds.SectorsWrite)
+	}
+
+	// Verify new snapshot has updated values
+	snap2 := s.Snapshot()
+	ds2 := snap2["host1"].Disk["sda"]
+	if ds2.SectorsRead != 999 || ds2.SectorsWrite != 888 {
+		t.Errorf("snap2: got sr=%d sw=%d, want sr=999 sw=888",
+			ds2.SectorsRead, ds2.SectorsWrite)
+	}
+}
+
+// Ensure Store still satisfies the collector.StatsStore interface (which now includes SetDisk).
+var _ collector.StatsStore = (*Store)(nil)
+var _ stats.Source = (*Store)(nil)