package web

import (
	"bytes"
	"encoding/base64"
	"image/png"
	"net/http"

	"github.com/boombuler/barcode"
	"github.com/boombuler/barcode/code128"
	qrcode "github.com/skip2/go-qrcode"
)

// qrDataURI renders content as a QR code PNG and returns it as a data: URI
// suitable for an <img src>, so labels need no separate image requests.
func qrDataURI(content string, size int) (string, error) {
	png, err := qrcode.Encode(content, qrcode.Medium, size)
	if err != nil {
		return "", err
	}
	return "data:image/png;base64," + base64.StdEncoding.EncodeToString(png), nil
}

// barcodeDataURI renders content as a Code128 linear barcode PNG, scaled to
// widthPx x heightPx, and returns it as a data: URI.
func barcodeDataURI(content string, widthPx, heightPx int) (string, error) {
	bc, err := code128.Encode(content)
	if err != nil {
		return "", err
	}
	scaled, err := barcode.Scale(bc, widthPx, heightPx)
	if err != nil {
		return "", err
	}
	var buf bytes.Buffer
	if err := png.Encode(&buf, scaled); err != nil {
		return "", err
	}
	return "data:image/png;base64," + base64.StdEncoding.EncodeToString(buf.Bytes()), nil
}

// requestOrigin reconstructs the scheme+host the request arrived on, for
// building absolute URLs (e.g. QR codes need a full URL, not a path).
func requestOrigin(r *http.Request) string {
	scheme := "http"
	if r.TLS != nil {
		scheme = "https"
	}
	if proto := r.Header.Get("X-Forwarded-Proto"); proto != "" {
		scheme = proto
	}
	return scheme + "://" + r.Host
}