hamann-ausgabe-core/HaWeb/FileHelpers/MultipartRequestHelper.cs

namespace HaWeb.FileHelpers;
using System;
using System.IO;
using Microsoft.Net.Http.Headers;

public static class MultipartRequestHelper {
    // Content-Type: multipart/form-data; boundary="----WebKitFormBoundarymx2fSWqWSd0OxQqq"
    // The spec at https://tools.ietf.org/html/rfc2046#section-5.1 states that 70 characters is a reasonable limit.
    public static string GetBoundary(MediaTypeHeaderValue contentType, int lengthLimit) {
        var boundary = HeaderUtilities.RemoveQuotes(contentType.Boundary).Value;

        if (string.IsNullOrWhiteSpace(boundary))
            throw new InvalidDataException("Missing content-type boundary.");

        if (boundary.Length > lengthLimit)
            throw new InvalidDataException($"Multipart boundary length limit {lengthLimit} exceeded.");

        return boundary;
    }

    public static bool IsMultipartContentType(string? contentType)
        => !string.IsNullOrEmpty(contentType) && contentType.IndexOf("multipart/", StringComparison.OrdinalIgnoreCase) >= 0;

    public static bool HasFormDataContentDisposition(ContentDispositionHeaderValue contentDisposition) {
        // Content-Disposition: form-data; name="key";
        return contentDisposition != null
            && contentDisposition.DispositionType.Equals("form-data")
            && string.IsNullOrEmpty(contentDisposition.FileName.Value)
            && string.IsNullOrEmpty(contentDisposition.FileNameStar.Value);
    }

    public static bool HasFileContentDisposition(ContentDispositionHeaderValue? contentDisposition) {
        return contentDisposition != null
            && contentDisposition.DispositionType.Equals("form-data")
            && (!string.IsNullOrEmpty(contentDisposition.FileName.Value)
                || !string.IsNullOrEmpty(contentDisposition.FileNameStar.Value));
    }
}