Chunk large Messages to the Companion

WebRTC can only safely send messages of 16K. So we will only send up to
8K characters (ok, a margin of safety). Most projects do not need to
send YAIL forms larger then this, but a few do.

To “chunk” the code into smaller pieces would normally require changes
both on the browser side and the Companion side. However we wish to
avoid changing the Companion at this time. So instead, we break the
large YAIL forms into smaller YAIL forms that can each be evaled on the
device correctly.

Change-Id: I865e39cad3c55ea35b2a56582d50136f8303e90e

appinventor/blocklyeditor/src/replmgr.js

@@ -441,6 +441,41 @@ Blockly.ReplMgr.putYail = (function() {
             poll();
 
         },
+        'chunker' : (function() {
+            var seq = 0;
+            var gensym = function() {
+                seq += 1;
+                return 'Q' + seq;
+            };
+
+            var chunker = function(input) {
+                var length = input.length;
+                var chunklen = 15000; // purposely smaller then 16K because we
+                if (length <= chunklen) { // add overhead
+                    return [input];
+                }
+                var chunks = [];
+                while (length > 0) {
+                    var clen = Math.min(length, chunklen);
+                    chunks.push(input.substring(0, clen));
+                    input = input.substring(clen);
+                    length = input.length;
+                }
+                var symbol = gensym();
+                var retval = [];
+                retval.push('(define ' + symbol + ' "")');
+                chunks.forEach(function(item, index) {
+                    item = item.replace(/\\/g, '\\\\');
+                    item = item.replace(/"/g, '\\"');
+                    var code = '(set! ' + symbol + ' (string-append ' + symbol + ' "' + item + '"))';
+                    retval.push(code);
+                });
+                retval.push('(eval (read (open-input-string ' + symbol + ')))');
+                retval.push('(set! ' + symbol + ' #!null)'); // so memory is gc'd
+                return retval;
+            };
+            return (chunker);
+        })(),
         'pollphone' : function() {
             if (!rs.didversioncheck) {
                 engine.doversioncheck();
@@ -479,7 +514,15 @@ Blockly.ReplMgr.putYail = (function() {
                     sendcode = "(begin (require <com.google.youngandroid.runtime>) (process-repl-input " +
                         blockid + " (begin " + work.code + ")))";
                     console.log(sendcode);
-                    webrtcdata.send(sendcode); // Send the code!
+                    // sendcode is a string of all of the scheme code
+                    sendcode = engine.chunker(sendcode);
+                    // sendcode is now an array of strings, also scheme
+                    // code, but guaranteed that each will fit in a
+                    // webrtc message
+                    sendcode.forEach(function(item) {
+                        console.log('Chunk: ' + item);
+                        webrtcdata.send(item);
+                    });
                 }
                 if (rs.state == Blockly.ReplMgr.rsState.CONNECTED) {
                     while ((work = rs.phoneState.phoneQueue.shift())) {
@@ -491,7 +534,15 @@ Blockly.ReplMgr.putYail = (function() {
                         sendcode = "(begin (require <com.google.youngandroid.runtime>) (process-repl-input " +
                             blockid + " (begin " + work.code + ")))";
                         console.log(sendcode);
-                        webrtcdata.send(sendcode); // Send the code!
+                        // sendcode is a string of all of the scheme code
+                        sendcode = engine.chunker(sendcode);
+                        // sendcode is now an array of strings, also scheme
+                        // code, but guaranteed that each will fit in a
+                        // webrtc message
+                        sendcode.forEach(function(item) {
+                            console.log('Chunk: ' + item);
+                            webrtcdata.send(item);
+                        });
                     }
                 }
                 rs.phoneState.ioRunning = false;