Textpattern textile syntax highlighting of body and excerpt textareas using in-built prism js (v4.6) – first pass

gistfile1.txt

<!-- paste this in the "additional js code" window of write_tab_customize or include via theme -->

<style>
#main_content .text .microcode-wrapper {
  position: relative;
  height:auto;
  margin-bottom
}
#main_content .text .microcode-wrapper .code-input,
#main_content .text .microcode-wrapper .code-output {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 100%;
  padding: 1rem;
  background: transparent;
  white-space: pre-wrap;
  font-family: Consolas,Menlo,Monaco,monospace;
  font-size: 14px;
  line-height: 1.5em;
  word-wrap: break-word;
}
#main_content .text .microcode-wrapper .code-input {
  opacity: 0.7;
  margin: 0;
  color: #999;
  resize: none;
}
#main_content .text .microcode-wrapper .code-output {
  pointer-events: none;
  border-color: transparent;
  z-index: 3;
  margin: 0;
  overflow-y: auto;
  line-height: 1.5;
}
#main_content .text .microcode-wrapper .code-output code {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  margin: 0;
  padding: 1rem;
  display: block;
  color: #666;
  font-size: 14px;
  font-family: Consolas,Menlo,Monaco,monospace;
  word-wrap: break-word;
  white-space: pre-wrap;
}
</style>
<script>
;var MicroCode = (function(){
	return {
		init: function(inputSel, outputSel){
			this.focusInput(inputSel);
			this.resizeOutput(outputSel, $(inputSel).outerHeight() );
			this.listenForInput(inputSel, outputSel);
			this.renderOutput(outputSel, $(inputSel)[0].value);
			this.listenerForScroll(inputSel, outputSel);
			this.listenerForResize(inputSel, outputSel);
		},
		
		listenForInput: function(inputSel, outputSel){
			var self = this;

			$(inputSel).on('input keydown', function(key){
				var input = this,
					selStartPos = input.selectionStart,
					inputVal = input.value;

				if(key.keyCode === 9){
					input.value = inputVal.substring(0, selStartPos) + "    " + inputVal.substring(selStartPos, input.value.length);
					input.selectionStart = selStartPos + 4;
					input.selectionEnd = selStartPos + 4;
					key.preventDefault();
				}

				self.renderOutput(outputSel, this.value);
			});

			Prism.highlightAll();
		},
		
		listenerForScroll: function(inputSel, outputSel){
			$(inputSel).on('scroll', function(){
				console.log(this.scrollTop);
				$(outputSel)[0].scrollTop = this.scrollTop;
			});
		},
		
		listenerForResize: function(inputSel, outputSel){
		  var self = this;
			$(inputSel).on('autosize:resized', function() {
				self.resizeOutput(outputSel, $(inputSel).outerHeight() );
			});
		},
		
		resizeOutput: function(outputSel, value){
		  $(outputSel).add($(outputSel).parent()).height(value);
		},
		
		renderOutput: function(outputSel, value){
			$('code', outputSel)
				.html(value
				.replace(/&/g, "&amp;")
				.replace(/</g, "&lt;")
				.replace(/>/g, "&gt;") + "\n");
			
			Prism.highlightAll();
		},
		
		focusInput: function(inputSel){
			var input = $(inputSel);
			
			input.focus();
			
			input[0].selectionStart = input[0].value.length;
			input[0].selectionEnd = input[0].value.length;
		}
	}
})();

$(function() {
  // change "textile" to "markdown" to use markdown syntax highlighting
  var MicroCodeSyntax = 'textile';
  var $Textareas = $('#body').add('#excerpt');
  
  // add wrapper and input class
  $Textareas.addClass('code-input').wrap('<div class="microcode-wrapper"></div>');

  // add styled code output container
  $('<pre class="body-output code-output language-' + MicroCodeSyntax + '"><code class="language-' + MicroCodeSyntax + '"></code></pre>').insertAfter('#body');
  $('<pre class="excerpt-output code-output language-' + MicroCodeSyntax + '"><code class="language-' + MicroCodeSyntax + '"></code></pre>').insertAfter('#excerpt');
  
  // initiate MicroCode syntax highlighting
  MicroCode.init('#body', '.body-output');
  MicroCode.init('#excerpt', '.excerpt-output');

});
</script>

Based on @kazzkiq's codepen.