From 1d4896f1f22a88c49ef116887efbe9a40a105457 Mon Sep 17 00:00:00 2001
From: Eugene Blikh <bigbes@gmail.com>
Date: Tue, 28 Apr 2026 03:38:39 +0300
Subject: [PATCH] systems-power: HUD geometry + hudHitTest with tests

systems-power
---
 hud.go      | 30 +++++++++++++++++++
 hud_test.go | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 hud.go
 create mode 100644 hud_test.go

diff --git a/hud.go b/hud.go
new file mode 100644
index 0000000000000000000000000000000000000000..6b090279801d3289cfc1b284e76aa7c7eb79cf93
--- /dev/null
+++ b/hud.go
@@ -0,0 +1,30 @@
+package main
+
+// HUD geometry constants. All values are in virtual pixels (640×360 grid).
+// HudY is the top edge of the HUD strip; the five power columns begin at HudX
+// and are each HudColW pixels wide. The reactor-readout band occupies the
+// horizontal range [0, HudX).
+const (
+	HudY        = 272
+	HudX        = 200
+	HudColW     = 40
+	HudColCount = 5
+)
+
+// hudHitTest maps a virtual-pixel coordinate to the RoomRole whose power column
+// was clicked. Returns ok=false for any coordinate outside the column strip:
+//   - py < HudY  (above the HUD)
+//   - px < HudX  (reactor-readout band to the left)
+//   - px >= HudX + HudColCount*HudColW  (right of last column)
+//
+// Columns are flush (no gutters). Column i covers [HudX+i*HudColW, HudX+(i+1)*HudColW).
+func hudHitTest(px, py int) (RoomRole, bool) {
+	if py < HudY {
+		return 0, false
+	}
+	if px < HudX || px >= HudX+HudColCount*HudColW {
+		return 0, false
+	}
+	idx := (px - HudX) / HudColW
+	return RoomRole(idx), true
+}
diff --git a/hud_test.go b/hud_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..dfda1799964660980f3ab0cf68ffc2869d0a156d
--- /dev/null
+++ b/hud_test.go
@@ -0,0 +1,83 @@
+package main
+
+import "testing"
+
+// TestHudHitTest_aboveHud verifies that a pixel above the HUD strip returns ok=false.
+func TestHudHitTest_aboveHud(t *testing.T) {
+	_, ok := hudHitTest(HudX+HudColW/2, HudY-1)
+	if ok {
+		t.Errorf("expected ok=false for py=%d (above HudY=%d)", HudY-1, HudY)
+	}
+}
+
+// TestHudHitTest_leftOfColumns verifies that a pixel in the reactor-readout band
+// to the left of the column strip returns ok=false.
+func TestHudHitTest_leftOfColumns(t *testing.T) {
+	_, ok := hudHitTest(HudX-1, HudY)
+	if ok {
+		t.Errorf("expected ok=false for px=%d (left of HudX=%d)", HudX-1, HudX)
+	}
+}
+
+// TestHudHitTest_rightOfColumns verifies that a pixel at or beyond the right edge
+// of the column strip returns ok=false.
+func TestHudHitTest_rightOfColumns(t *testing.T) {
+	px := HudX + HudColCount*HudColW
+	_, ok := hudHitTest(px, HudY)
+	if ok {
+		t.Errorf("expected ok=false for px=%d (right edge, HudX+5*HudColW=%d)", px, HudX+HudColCount*HudColW)
+	}
+}
+
+// TestHudHitTest_eachColumnCenter verifies that the pixel at the horizontal centre
+// of column i maps to RoomRole(i) with ok=true.
+func TestHudHitTest_eachColumnCenter(t *testing.T) {
+	roles := []RoomRole{RolePilot, RoleWeapons, RoleShields, RoleMedBay, RoleEngines}
+	for i, want := range roles {
+		px := HudX + i*HudColW + HudColW/2
+		py := HudY
+		got, ok := hudHitTest(px, py)
+		if !ok {
+			t.Errorf("column %d centre px=%d: expected ok=true", i, px)
+			continue
+		}
+		if got != want {
+			t.Errorf("column %d centre px=%d: got role %d, want %d", i, px, got, want)
+		}
+	}
+}
+
+// TestHudHitTest_columnEdges verifies inclusive left-edge and exclusive right-edge
+// semantics for each column.
+func TestHudHitTest_columnEdges(t *testing.T) {
+	py := HudY
+
+	for i := 0; i < HudColCount; i++ {
+		// Left edge of column i — inclusive, must return RoomRole(i).
+		leftPx := HudX + i*HudColW
+		got, ok := hudHitTest(leftPx, py)
+		if !ok {
+			t.Errorf("column %d left edge px=%d: expected ok=true", i, leftPx)
+		} else if got != RoomRole(i) {
+			t.Errorf("column %d left edge px=%d: got role %d, want %d", i, leftPx, got, RoomRole(i))
+		}
+
+		// Right edge of column i (first pixel of next column) — exclusive.
+		rightPx := HudX + (i+1)*HudColW
+		if i < HudColCount-1 {
+			// Should belong to column i+1.
+			got, ok = hudHitTest(rightPx, py)
+			if !ok {
+				t.Errorf("column %d right-exclusive px=%d: expected ok=true (belongs to col %d)", i, rightPx, i+1)
+			} else if got != RoomRole(i+1) {
+				t.Errorf("column %d right-exclusive px=%d: got role %d, want %d", i, rightPx, got, RoomRole(i+1))
+			}
+		} else {
+			// Last column: right edge is out of bounds.
+			_, ok = hudHitTest(rightPx, py)
+			if ok {
+				t.Errorf("last column right-exclusive px=%d: expected ok=false", rightPx)
+			}
+		}
+	}
+}