package platepdf

import (
	"bytes"
	"encoding/base64"
	"fmt"

	"printer.backend/internal/model"
)

const renderDPI = 300

// BuildCompositeSVG assembles a plate-sized SVG by embedding each item as a PNG
// rendered by rsvg-convert (identical to the standalone item file).
func BuildCompositeSVG(plate model.Plate, spec model.ItemSpec, itemSVG []byte, preview model.LayoutPreview) ([]byte, error) {
	itemW, itemH, err := svgViewportMM(itemSVG)
	if err != nil {
		return nil, err
	}
	if itemW <= 0 || itemH <= 0 {
		itemW, itemH = spec.SizeMM, spec.SizeMM
	}

	itemPNG, err := svgToPNGViaRsvg(itemSVG, renderDPI)
	if err != nil {
		return nil, fmt.Errorf("render item: %w", err)
	}
	itemB64 := base64.StdEncoding.EncodeToString(itemPNG)

	var b bytes.Buffer
	fmt.Fprintf(&b, `<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 %.4f %.4f" width="%.4fmm" height="%.4fmm">
  <rect width="%.4f" height="%.4f" fill="#ffffff"/>
  <rect x="%.4f" y="%.4f" width="%.4f" height="%.4f" fill="none" stroke="#cccccc" stroke-width="0.2"/>
`,
		plate.WidthMM, plate.HeightMM, plate.WidthMM, plate.HeightMM,
		plate.WidthMM, plate.HeightMM,
		preview.PrintableXMM, preview.PrintableYMM, preview.PrintableWMM, preview.PrintableHMM,
	)

	for _, pos := range preview.Positions {
		fmt.Fprintf(&b,
			`<image x="%.4f" y="%.4f" width="%.4f" height="%.4f" href="data:image/png;base64,%s"/>`,
			pos.XMM, pos.YMM, itemW, itemH, itemB64,
		)
	}

	b.WriteString("\n</svg>")
	return b.Bytes(), nil
}