gfse: edit abstract syntax in text mode with instant syntax error reporting

This is an experimental feature. It requires server support for parsing and is
thus not available while offline, unlike most other editing functionality.

src/www/gfse/cloud2.js

@@ -193,6 +193,12 @@ function gfshell(cmd,cont) {
     })
 }
 
+// Check the syntax of a source module
+function check_module(path,source,cont) {
+    var enc=encodeURIComponent;
+    http_get_json("/parse?"+enc(path)+"="+enc(source),cont)
+}
+
 // Check the syntax of an expression
 function check_exp(s,cont) {
     function check(gf_message) {

src/www/gfse/editor.js

@@ -453,7 +453,7 @@ function draw_abstract(g) {
 	timestamp(g.abstract);
 	save_grammar(g);
     }
-    return div_id("file",
+    var file=div_id("file",
 		  [kw("abstract "),ident(g.basename),sep(" = "),
 		   draw_timestamp(g.abstract),
 		   draw_extends(g),
@@ -462,6 +462,65 @@ function draw_abstract(g) {
 				       indent(draw_cats(g))]),
 			   extensible([kw_fun,
 				       indent_sortable(draw_funs(g),sort_funs)])])]);
+    if(navigator.onLine) {
+	var mode_button=text_mode(g,file);
+	insertBefore(mode_button,file.firstChild)
+    }
+    return file;
+}
+
+function text_mode(g,file) {
+    var path=g.basename+".gf"
+    function switch_to_guided_mode() {
+	edit_grammar(g); // !!
+    }
+    function store_parsed(parse_results) {
+	var dst=compiler_output;
+	var msg=parse_results[path];
+	if(dst) dst.innerHTML=""
+	console.log(msg)
+	if(dst && msg.error)
+	    dst.appendChild(span_class("error_message",
+				       text(msg.location+": "+msg.error)))
+	else if(dst && msg.parsed)
+	    dst.innerHTML=
+	      "Accepted by GF, but not by this editor ("+msg.parsed+")"
+	else if(msg.converted) {
+	    var gnew=msg.converted;
+	    g.abstract=gnew.abstract;
+	    g.extends=gnew.extends;
+	    timestamp(g.abstract);
+	    save_grammar(g);
+	}
+	else if(dst) dst.innerHTML="unexpected parse result";
+    }
+    var last_source=show_abstract(g);
+    function parse(source) {
+	if(source!=last_source) {
+	    if(navigator.onLine) {
+		//compiler_output.innerHTML="";
+		last_source=source;
+		check_module(path,source,store_parsed)
+	    }
+	    else if(compiler_output)
+		compiler_output.innerHTML="Offline, edits will not be saved"
+	}
+    }
+    function switch_to_text_mode() {
+	var ta=node("textarea",{class:"text_mode",rows:25,cols:80},
+		[text(show_abstract(g))])
+	var timeout;
+	ta.onkeyup=function() {
+	    if(timeout) clearTimeout(timeout);
+	    timeout=setTimeout(function(){parse(ta.value)},400)
+	}
+	var mode_button=div_class("right",[button("Guided mode",switch_to_guided_mode)])
+	file.innerHTML="";
+	appendChildren(file,[mode_button,ta])
+	ta.focus();
+    }
+    var mode_button=div_class("right",[button("Text mode",switch_to_text_mode)])
+    return mode_button;
 }
 
 function add_cat(g,el) {