package itemimage

import (
	"encoding/base64"
	"fmt"
	"net/http"
	"regexp"
	"strings"

	"printer.backend/internal/model"
	"printer.backend/internal/svgtemplate"
)

var maskGroupRE = regexp.MustCompile(`(?s)(<g clip-path="url\(#item-mask\)">).*?(</g>)`)

// Embed replaces the green placeholder in an item SVG with the given raster image,
// clipped to the product mask (same area as the green preview rect).
func Embed(itemSVG []byte, spec model.ItemSpec, imageData []byte, contentType string) ([]byte, error) {
	if len(imageData) == 0 {
		return nil, fmt.Errorf("empty image data")
	}
	if err := spec.Normalize(); err != nil {
		return nil, err
	}

	d := svgtemplate.Build(
		spec.WidthMM, spec.HeightMM,
		spec.BleedMM, spec.MarginMM, spec.PaddingMM,
		spec.CornerRadiusMM,
	)
	prepared, mime, err := prepareRaster(imageData, d)
	if err != nil {
		return nil, err
	}
	if mime == "" {
		mime = normalizeMIME(contentType, prepared)
	}
	href := fmt.Sprintf("data:%s;base64,%s", mime, base64.StdEncoding.EncodeToString(prepared))

	inner := fmt.Sprintf(
		`<image x="%.4f" y="%.4f" width="%.4f" height="%.4f" preserveAspectRatio="xMidYMid slice" href="%s"/>`,
		d.OuterOffsetX, d.OuterOffsetY, d.OuterWidth, d.OuterHeight, href,
	)

	out := maskGroupRE.ReplaceAll(itemSVG, []byte("${1}"+inner+"${2}"))
	if string(out) == string(itemSVG) {
		return nil, fmt.Errorf("item svg has no printable mask group")
	}
	return out, nil
}

func normalizeMIME(contentType string, data []byte) string {
	if ct := strings.TrimSpace(strings.Split(contentType, ";")[0]); ct != "" {
		return ct
	}
	return http.DetectContentType(data)
}