imgproxy/options/url.go

package options

import (
	"encoding/base64"
	"errors"
	"fmt"
	"net/url"
	"strings"

	"github.com/imgproxy/imgproxy/v2/config"
)

const urlTokenPlain = "plain"

func decodeBase64URL(parts []string) (string, string, error) {
	var format string

	encoded := strings.Join(parts, "")
	urlParts := strings.Split(encoded, ".")

	if len(urlParts[0]) == 0 {
		return "", "", errors.New("Image URL is empty")
	}

	if len(urlParts) > 2 {
		return "", "", fmt.Errorf("Multiple formats are specified: %s", encoded)
	}

	if len(urlParts) == 2 && len(urlParts[1]) > 0 {
		format = urlParts[1]
	}

	imageURL, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(urlParts[0], "="))
	if err != nil {
		return "", "", fmt.Errorf("Invalid url encoding: %s", encoded)
	}

	fullURL := fmt.Sprintf("%s%s", config.BaseURL, string(imageURL))

	return fullURL, format, nil
}

func decodePlainURL(parts []string) (string, string, error) {
	var format string

	encoded := strings.Join(parts, "/")
	urlParts := strings.Split(encoded, "@")

	if len(urlParts[0]) == 0 {
		return "", "", errors.New("Image URL is empty")
	}

	if len(urlParts) > 2 {
		return "", "", fmt.Errorf("Multiple formats are specified: %s", encoded)
	}

	if len(urlParts) == 2 && len(urlParts[1]) > 0 {
		format = urlParts[1]
	}

	unescaped, err := url.PathUnescape(urlParts[0])
	if err != nil {
		return "", "", fmt.Errorf("Invalid url encoding: %s", encoded)
	}

	fullURL := fmt.Sprintf("%s%s", config.BaseURL, unescaped)

	return fullURL, format, nil
}

func DecodeURL(parts []string) (string, string, error) {
	if len(parts) == 0 {
		return "", "", errors.New("Image URL is empty")
	}

	if parts[0] == urlTokenPlain && len(parts) > 1 {
		return decodePlainURL(parts[1:])
	}

	return decodeBase64URL(parts)
}