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
}