Java-2-HTML converter

collapse.js

/**
 * When the window loads, insert collapse buttons.
 */
window.onload = function() {
	// Iterate code blocks:
	var codeBlocks = document.getElementsByTagName("pre");
	for (var i = 0; i < codeBlocks.length; i++) {
		// Iterate block children to identify the sections.
		// They should be the only elements with ID's in the <pre> tag.
		var pre = codeBlocks[i];
		var children = pre.getElementsByTagName("*");
		for (var c = 0; c < children.length; c++) {
			var child = children[c];
			// ID span found, add collapse to it.
			if (!isEmpty(child.id)){
				addCollapse(pre, child.id);
				c++;
			}
		}
	}
};

/**
 * containerx: 
 *			Element that holds the container marked by the ID
 * id:
 *			ID of collapseable content. Relative to the container, not the whole document.
 */
function addCollapse(containerx, id) {
	// create buttons that collapse the content of those containers.
	var container = containerx.querySelector("#" + id);
	//var parent = container.parentNode;
	var toggleBtn = document.createElement("div");
	toggleBtn.className = "toggle-open";
	// click action
	toggleBtn.onclick = function () {
		collapse(toggleBtn, container, id);
	};
	// hover to show what will be collapsed
	toggleBtn.onmouseout = function () {
		setHighlighted(container, true);
		setHighlightedDummy(id, true);
	}
	toggleBtn.onmouseover = function () {
		setHighlighted(container, false);
		setHighlightedDummy(id, false);
	}
	containerx.insertBefore(toggleBtn, container);
}

/**
 * container: 
 *			Container to be marked.
 * highlighted:
 *			If container should be highlighted, noting collapseable content.
 */
function setHighlighted(container, highlighted) {
	var cls = container.className;
	if(highlighted) {
		container.className = container.className.replace("toggle-section", "");
	} else {
		container.className += " toggle-section";
	}
}

/**
 * id: 
 *			ID of dummy content to be marked.
 * highlighted:
 *			If container should be highlighted, noting collapseable content.
 */
function setHighlightedDummy(id, highlighted) {
	var dcID = "dummy-cont-" + id;
	var container = document.getElementById(dcID);
	if (container != null) {
		setHighlighted(container, highlighted);
	}
}

/**
 * button:
 *			The button that controls the visibility of the container.
 * container:
 *			Span containing collapsable content.
 * id:
 *			ID of the container.
 */
function collapse(button, container, id) {
	// toggle button format
	var btnType = button.className;
	var dlID = "dummy-line-" + id;
	var dcID = "dummy-cont-" + id; 
	if(btnType == "toggle-open") {
		button.className = "toggle-closed";
		// replace with dummy line
		var dLine = document.createElement("span");
		var dContent = document.createElement("span");
		dLine.id = dlID;
		dLine.className = "line";
		dContent.id = dcID; 
		dContent.className = "comment-line toggle-section"; // selection included since mouse will be over
		dContent.innerHTML = "// " + id + "... ";
		container.parentNode.insertBefore(dLine, container);
		container.parentNode.insertBefore(dContent, container);
	} else{
		button.className = "toggle-open";
		// remove dummy items
		document.getElementById(dlID).outerHTML = "";
		document.getElementById(dcID).outerHTML = "";
	}
	// toggle visibility of container
	if (container.style.display === "none") {
		container.style.display = "inline";
	} else {
		container.style.display = "none";
	}
}

/**
 * Check if string is empty.
 */
function isEmpty(str) {
	return (!str || 0 === str.length);
}

Java2Html.java

package me.coley.j2h;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.SplitPane;
import javafx.scene.control.TextArea;
import javafx.stage.Stage;

// https://mvnrepository.com/artifact/org.apache.commons/commons-text
import org.apache.commons.text.StringEscapeUtils;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Basic java to HTML converter using regex
 *
 * @author Matt
 */
public class Java2Html extends Application {
	//@formatter:off
	private static final String[] KEYWORDS = new String[] { "abstract", "assert", "boolean", "break", "byte", "case", "catch",
			"char", "class", "const", "continue", "default", "do", "double", "else", "enum", "extends", "final", "finally",
			"float", "for", "goto", "if", "implements", "import", "instanceof", "int", "interface", "long", "native", "new",
			"package", "private", "protected", "public", "return", "short", "static", "strictfp", "super", "switch",
			"synchronized", "this", "throw", "throws", "transient", "try", "void", "volatile", "while" };
	//@formatter:on
	private static final String KEYWORD_PATTERN = "\\b(" + String.join("|", KEYWORDS) + ")\\b";
	private static final String STRING_PATTERN = "\"([^\"\\\\]|\\\\.)*\"";
	private static final String CONST_HEX_PATTERN = "(0[xX][0-9a-fA-F]+)+";
	private static final String CONST_VAL_PATTERN = "(\\b([\\d._]*[\\d])\\b)+|(true|false|null)";
	private static final String CONST_PATTERN = CONST_HEX_PATTERN + "|" + CONST_VAL_PATTERN;
	private static final String COMMENT_SINGLE_PATTERN = "//[^\n]*";
	private static final String COMMENT_MULTI_SINGLE_PATTERN = "/[*](.|\\R)+?\\*/";
	private static final String COMMENT_MULTI_JAVADOC_PATTERN = "/[*]{2}(.|\\R)+?\\*/";
	private static final String ANNOTATION_PATTERN = "\\B(@[\\w]+)\\b";
	//@formatter:off
	private static final Pattern PATTERN = Pattern.compile(
			 "(?<KEYWORD>" + KEYWORD_PATTERN + ")" +
			"|(?<STRING>" + STRING_PATTERN + ")" +
			"|(?<COMMENTDOC>" + COMMENT_MULTI_JAVADOC_PATTERN + ")" +
			"|(?<COMMENTMULTI>" + COMMENT_MULTI_SINGLE_PATTERN + ")" +
			"|(?<COMMENTLINE>" + COMMENT_SINGLE_PATTERN + ")" +
			"|(?<ANNOTATION>" + ANNOTATION_PATTERN + ")" +
			"|(?<CONSTPATTERN>" + CONST_PATTERN + ")");
	//@formatter:on
	public static void main(String[] args) {
		launch(args);
	}

	@Override
	public void start(Stage primaryStage) {
		TextArea input = new TextArea();
		TextArea output = new TextArea();
		input.textProperty().addListener((observable, oldValue, newValue) -> {
			update(output, newValue);
		});
		SplitPane pane = new SplitPane(input, output);
		primaryStage.setScene(new Scene(pane, 900, 800));
		primaryStage.setTitle("Java2Html");
		primaryStage.show();
	}

	/**
	 * Set the value of the TextArea <i>(output)</i> to the HTML-decorated version of the input <i>(text)</i>.
	 *
	 * @param output
	 * 		TextArea that will host the output.
	 * @param text
	 * 		Input text <i>(Java code)</i>
	 */
	private static void update(TextArea output, String text) {
		text = text.replace("\t", "    ");
		Matcher matcher = PATTERN.matcher(text);
		StringBuilder sb = new StringBuilder();
		int lastEnd = 0;
		while(matcher.find()) {
			//@formatter:off
			String styleClass =
					  matcher.group("STRING")       != null ? "string"
					: matcher.group("KEYWORD")      != null ? "keyword"
					: matcher.group("COMMENTDOC")   != null ? "comment-javadoc"
					: matcher.group("COMMENTMULTI") != null ? "comment-multi"
					: matcher.group("COMMENTLINE")  != null ? "comment-line"
					: matcher.group("CONSTPATTERN") != null ? "const"
					: matcher.group("ANNOTATION")   != null ? "annotation" : null;
			//@formatter:on
			int start = matcher.start();
			int end = matcher.end();
			// append text not matched
			if(start > lastEnd) {
				sb.append(StringEscapeUtils.escapeHtml4(text.substring(lastEnd, start)));
			}
			// append match
			sb.append("<span class=\"" + styleClass + "\">" + StringEscapeUtils.escapeHtml4(text.substring(start, end)) + "</span>");
			lastEnd = end;
		}
		sb.append(StringEscapeUtils.escapeHtml4(text.substring(lastEnd)));
		StringBuilder fmt = new StringBuilder();
		for(String line : sb.toString().split("\n")) {
			fmt.append("<span class=\"line\"></span>" + line + "\n");
		}
		output.setText("<pre>" + fmt.toString() + "</pre>");
	}
}

style.css

/* =========================== */
/*         Code block          */
/* =========================== */
/* HTML auto-gen to match this with: 
https://gist.github.com/Col-E/006ee9c807e3ded1881a39109fd16900 
*/
pre {
	font-family: monospace;
	background: rgba(0,0,0,0.04);
	border: 1px solid rgba(0,0,0,0.3);
	counter-reset: ln;
	margin-left: 2px;
	margin-right: 2px;
	overflow: auto;
}
pre * { 
	font-family: monospace;
}
/* show line numbers */
pre .line { 
	display: inline-block;
}
pre .line::before {
	counter-increment: ln;
	content: counter(ln);
	display: inline-block;
	color: black; 
	font-weight: normal; 
	font-style: normal; 
	border-right: 1px solid rgba(200,200,200,1);
	padding: 0 15;
	margin: 0 10 0 0;
	width: 20px;
	text-align: center;
	background: rgba(0,0,0,0.035);
}
/* code style for element types */
pre .keyword { 
	color: rgb(127, 0, 85);
	font-weight: bold;
	text-shadow: none;
}
pre .string { 
	color: rgb(47, 100, 31); 
	font-style: italic;
}
pre .const {
	color: rgb(173, 53, 0); 
}
pre .annotation {
	color: rgb(120, 130, 150); 
}
pre .comment-line,
pre .comment-multi {
	color: rgb(0, 111, 12); 
	font-style: italic;
}
pre .comment-javadoc { 
	color: rgb(0, 100, 114); 
	font-style: italic;
}
/* =========================== */
/*  Code block section toggle  */
/* =========================== */
/* shared button style */
.toggle-open, 
.toggle-closed {
	cursor: pointer;
	position: absolute;
	display: inline-block;
	margin-left: -15px;
	text-align: center;
	width: 13px;
	background: rgba(0,0,0,0.2);
	border: 1px solid rgba(0,0,0,0.3);
}
/* closed button is more blue */
.toggle-closed {
	background: rgba(20,20,130,0.4);
}
/* text (+/-) for open/close button operations */
.toggle-open::before {
	content: '-';
}
.toggle-closed::before {
	content: '+';
}
/* dark on hover */
.toggle-open:hover, 
.toggle-closed:hover {
	background: rgba(0,0,0,0.34);
}
/* highlight for code belonging to a toggle-button */
.toggle-section {
	background: rgba(0,0,100,0.1);
}