Added Configuration from Item and Plate

internal/layout/layout.go

@@ -0,0 +1,75 @@
+package layout
+
+import (
+	"printer.backend/internal/model"
+)
+
+// Footprint returns the physical width and height one item occupies on the plate (mm).
+// Includes bleed on all sides and the item's margin as a safe zone.
+func Footprint(spec model.ItemSpec) (width, height float64) {
+	w := spec.SizeMM + 2*spec.BleedMM + 2*spec.MarginMM
+	return w, w
+}
+
+// CellPitch returns width and height of one grid cell (footprint + spacing between items).
+func CellPitch(spec model.ItemSpec, spacingMM float64) (width, height float64) {
+	fw, fh := Footprint(spec)
+	return fw + spacingMM, fh + spacingMM
+}
+
+// Pack computes the maximum grid of items that fit on the plate.
+func Pack(plate model.Plate, spec model.ItemSpec, spacingMM float64) model.LayoutPreview {
+	pw := plate.PrintableWidth()
+	ph := plate.PrintableHeight()
+	fw, fh := Footprint(spec)
+	cw, ch := CellPitch(spec, spacingMM)
+
+	cols, rows := gridCount(pw, ph, cw, ch)
+	count := cols * rows
+
+	ox := plate.MarginLeft
+	oy := plate.MarginTop
+
+	positions := make([]model.LayoutPosition, 0, count)
+	for row := 0; row < rows; row++ {
+		for col := 0; col < cols; col++ {
+			positions = append(positions, model.LayoutPosition{
+				XMM: ox + float64(col)*cw,
+				YMM: oy + float64(row)*ch,
+			})
+		}
+	}
+
+	return model.LayoutPreview{
+		PlateWidthMM:  plate.WidthMM,
+		PlateHeightMM: plate.HeightMM,
+		PrintableXMM:  ox,
+		PrintableYMM:  oy,
+		PrintableWMM:  pw,
+		PrintableHMM:  ph,
+		CellWidthMM:   cw,
+		CellHeightMM:  ch,
+		FootprintWMM:  fw,
+		FootprintHMM:  fh,
+		SpacingMM:     spacingMM,
+		Columns:       cols,
+		Rows:          rows,
+		Count:         count,
+		Positions:     positions,
+	}
+}
+
+func gridCount(printableW, printableH, cellW, cellH float64) (cols, rows int) {
+	if printableW <= 0 || printableH <= 0 || cellW <= 0 || cellH <= 0 {
+		return 0, 0
+	}
+	cols = int(printableW / cellW)
+	rows = int(printableH / cellH)
+	if cols < 0 {
+		cols = 0
+	}
+	if rows < 0 {
+		rows = 0
+	}
+	return cols, rows
+}

internal/layout/layout_test.go

@@ -0,0 +1,46 @@
+package layout
+
+import (
+	"testing"
+
+	"printer.backend/internal/model"
+)
+
+func TestPack(t *testing.T) {
+	plate := model.Plate{
+		WidthMM:      300,
+		HeightMM:     400,
+		MarginTop:    10,
+		MarginRight:  10,
+		MarginBottom: 10,
+		MarginLeft:   10,
+	}
+	spec := model.ItemSpec{SizeMM: 80, BleedMM: 2, MarginMM: 5}
+	// footprint = 80+4+10 = 94, cell = 94+2 = 96
+	// printable 280x380 -> cols=2, rows=3 -> 6
+	preview := Pack(plate, spec, 2)
+	if preview.Columns != 2 {
+		t.Fatalf("columns: got %d want 2", preview.Columns)
+	}
+	if preview.Rows != 3 {
+		t.Fatalf("rows: got %d want 3", preview.Rows)
+	}
+	if preview.Count != 6 {
+		t.Fatalf("count: got %d want 6", preview.Count)
+	}
+	if len(preview.Positions) != 6 {
+		t.Fatalf("positions: got %d want 6", len(preview.Positions))
+	}
+	if preview.Positions[0].XMM != 10 || preview.Positions[0].YMM != 10 {
+		t.Fatalf("first position: got (%v,%v)", preview.Positions[0].XMM, preview.Positions[0].YMM)
+	}
+}
+
+func TestPackZeroCell(t *testing.T) {
+	plate := model.Plate{WidthMM: 10, HeightMM: 10}
+	spec := model.ItemSpec{SizeMM: 100}
+	preview := Pack(plate, spec, 0)
+	if preview.Count != 0 {
+		t.Fatalf("expected 0 items, got %d", preview.Count)
+	}
+}