Download files via post request

Currently, download requests are handled via a get request which can
break in various ways.

For example, if the GET URL is too long and the servers MAX_URL_LENGTH (size)
is reached a 404 is thrown as reported in #7935

Resolves: #7935

Signed-off-by: fenn-cs <fenn25.fn@gmail.com>

apps/files/js/filelist.js

@@ -1051,7 +1051,7 @@
 			};
 
 			if(this.getSelectedFiles().length > 1) {
-				OCA.Files.Files.handleDownload(this.getDownloadUrl(files, dir, true), disableLoadingState);
+				OCA.Files.Files.handleDownload(this.getDownloadUrl(files, dir, true), disableLoadingState, files, dir);
 			}
 			else {
 				var first = this.getSelectedFiles()[0];

apps/files/js/files.js

@@ -364,7 +364,7 @@
 		 * @param {string} url download URL
 		 * @param {Function} callback function to call once the download has started
 		 */
-		handleDownload: function(url, callback) {
+		handleDownload: function(url, callback, files = null, dir = null)  {
 			var randomToken = Math.random().toString(36).substring(2),
 				checkForDownloadCookie = function() {
 					if (!OC.Util.isCookieSetToValue('ocDownloadStarted', randomToken)){
@@ -380,6 +380,10 @@
 			} else {
 				url += '?';
 			}
+			filesClient = OC.Files.getClient();
+			filesClient = filesClient.getClient();
+			// Method signature : request: function (method, url, headers, body, responseType, options) 
+			filesClient.request('POST', url, [], []);
 			OC.redirect(url + 'downloadStartSecret=' + randomToken);
 			OC.Util.waitFor(checkForDownloadCookie, 500);
 		}