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package model.html;
import java.util.*;
import org.javatuples.*;
/**
* This class represents the state of and implements an LL(1) HTML parser.
* For convenience, the following (defo wrong) context-free grammar for HTML is below.
* <br>
* HTML ::= '<!DOCTYPE html>' (NODE)*
* NODE ::= '<'TAG (' ' WORD '=' ('"'TEXT'"' | TEXT))* '>' (NODE)* '<\/' TAG '>'
* | '<'SELF_CLOSING_TAG (' ' WORD '=' ('"'TEXT'"' | TEXT))* ('>'|'/>')
* | (TEXT | NODE)*
* TEXT ::= UNICODE - {'"'} + {'\"'}
* TAG ::= 'body' | 'div' | ...
* SELF_CLOSING_TAG ::= 'img' | ...
* (note that \forall T \in SELF_CLOSING_TAG, T \notin TAG)
*/
public class HtmlParser {
/**
* HTML is not nice to parse. We manage to get away with a relatively small number of parser states regardless.
*/
private enum ParserState {
HTML, IGNORED,
OPENING_TAG, KEY, VALUE, // TAG::OPENING_TAG, TAG::KEY, TAG::VALUE
SINGLE_QUOTES, DOUBLE_QUOTES, // VALUE::SINGLE_QUOTES, VALUE::DOUBLE_QUOTES
UNKNOWN_TAG, CLOSING_TAG,
}
// HTML documents are uniquely a list of Nodes rather than a Node themselves
private ArrayList<Node> result;
// a bunch of useful buffers. see CssParser for commentary.
private ArrayDeque<ElementNode> unfinished;
private String currentTag;
private ArrayList<Pair<String, String>> currentAttributes;
private String currentKey;
private String currentValue;
private String currentText;
// important for quote escapes, and multiple whitespace chars
private char previousChar;
private ParserState state;
public HtmlParser() {
result = new ArrayList<>();
unfinished = new ArrayDeque<>();
currentTag = "";
currentAttributes = new ArrayList<>();
currentKey = "";
currentValue = "";
currentText = "";
previousChar = '\0';
// We safely? assume to start outside of all nodes.
state = ParserState.HTML;
}
public ArrayList<Node> parseHtml(String input) {
for (char c : input.toCharArray()) {
switch (state) {
case HTML -> caseHtml(c);
case UNKNOWN_TAG -> caseUnknownTag(c);
case IGNORED -> caseIgnored(c);
case OPENING_TAG -> caseOpeningTag(c);
case CLOSING_TAG -> caseClosingTag(c);
case KEY -> caseKey(c);
case VALUE -> caseValue(c);
case SINGLE_QUOTES -> caseSingleQuotes(c);
case DOUBLE_QUOTES -> caseDoubleQuotes(c);
}
}
return result;
}
private void caseHtml(char c) {
switch (c) {
case '<' -> {
state = ParserState.UNKNOWN_TAG;
if (!currentText.equals("")) {
addNewTextNode();
}
}
case ' ', '\t', '\n' -> {
if (previousChar != ' ') {
currentText += ' ';
}
previousChar = ' ';
}
default -> {
currentText += c;
previousChar = c;
}
}
}
private void caseUnknownTag(char c) {
switch (c) {
case '/' -> state = ParserState.CLOSING_TAG;
case '>' -> { // Why would you put <> in your HTML??? go away
state = ParserState.HTML;
currentText += "<>";
}
// For now, we'll straight up ignore anything matching the <!...> syntax:
// i.e. comments, and <!DOCTYPE html>
case '!' -> state = ParserState.IGNORED;
default -> {
state = ParserState.OPENING_TAG;
currentTag += c;
}
}
}
private void caseIgnored(char c) {
switch (c) {
case '>' -> state = ParserState.HTML;
default -> {}
}
}
private void caseOpeningTag(char c) {
switch (c) {
case '>' -> addNewElementNode();
case ' ', '\t', '\n' -> state = ParserState.KEY;
default -> currentTag += c;
}
}
private void caseClosingTag(char c) {
switch (c) {
case '>' -> {
state = ParserState.HTML;
// IMPORTANT: we don't validate that closing tags correspond to an open tag
if (!isSelfClosingTag(currentTag)) {
if (unfinished.size() != 0) {
unfinished.removeLast();
}
}
currentTag = "";
}
case ' ', '\t', '\n' -> {}
default -> currentTag += c;
}
}
private void caseKey(char c) {
switch (c) {
case '>' -> addNewElementNode();
case '=' -> state = ParserState.VALUE;
case ' ', '\t', '\n' -> {}
default -> currentKey += c;
}
}
private void caseValue(char c) {
switch (c) {
case '\'' -> state = ParserState.SINGLE_QUOTES;
case '\"' -> state = ParserState.DOUBLE_QUOTES;
case ' ', '\t', '\n' -> {
state = ParserState.KEY;
currentAttributes.add(new Pair<>(currentKey, currentValue));
currentKey = "";
currentValue = "";
}
case '>' -> {
if (!currentKey.equals("") || !currentValue.equals("")) {
currentAttributes.add(new Pair<>(currentKey, currentValue));
currentKey = "";
currentValue = "";
}
addNewElementNode();
}
default -> currentValue += c;
}
}
private void caseSingleQuotes(char c) {
switch (c) {
case '\'' -> {
if (previousChar != '\\') {
state = ParserState.VALUE;
previousChar = '\0';
} else {
currentValue = currentValue.substring(0, currentValue.length() - 1);
currentValue += c;
previousChar = c;
}
}
default -> {
currentValue += c;
previousChar = c;
}
}
}
private void caseDoubleQuotes(char c) {
switch (c) {
case '\"' -> {
if (previousChar != '\\') {
state = ParserState.VALUE;
previousChar = '\0';
} else {
currentValue = currentValue.substring(0, currentValue.length() - 1);
currentValue += c;
previousChar = c;
}
}
default -> {
currentValue += c;
previousChar = c;
}
}
}
// Helper function to remove code duplication.
private void addNewElementNode() {
state = ParserState.HTML;
var node = new ElementNode(currentTag, currentAttributes);
if (unfinished.size() != 0) {
unfinished.getLast().children.add(node);
if (!isSelfClosingTag(currentTag)) {
unfinished.add(node);
}
} else {
result.add(node);
if (!isSelfClosingTag(currentTag)) {
unfinished.add((ElementNode) result.get(result.size() - 1));
}
}
currentTag = "";
currentAttributes = new ArrayList<>();
}
// Helper function to check method length boxes.
private void addNewTextNode() {
if (!currentText.equals(" ")) { // fixme
if (unfinished.size() != 0) {
unfinished.getLast().children.add(new TextNode(currentText));
} else {
result.add(new TextNode(currentText));
}
}
currentText = "";
previousChar = '\0';
}
// Simple helper function to check if a tag is self-closing.
private static boolean isSelfClosingTag(String tag) {
return switch (tag) {
case "input", "param", "br", "hr", "wbr", "img", "embed", "area",
"meta", "base", "link", "source", "track", "col" -> true;
default -> false;
};
}
}
/*
<!DOCTYPE html>
<html>
<head>
<title>j-james</title>
<meta charset="utf-8"/>
<meta name="viewport" content="width=device-width"/>
<link rel="icon" type="image/jpg" href="assets/compass.jpg"/>
<link rel="stylesheet" href="css/normalize.css"/>
<link rel="stylesheet" href="css/style.css"/>
</head>
<body>
<header>
<h1>
<a href="https://j-james.me">j-james</a>
</h1>
<nav>
<a href="https://j-james.me/about">about</a>
<a href="https://j-james.me/resume">resume</a>
<a href="https://j-james.me/posts">posts</a>
<a href="https://j-james.me/writeups">writeups</a>
</nav>
</header>
<main>
<div id="intro">
<img id="face" src="assets/compass.jpg"/>
</div>
<div id="details">
<h2>Projects</h2>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris
nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum
dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa
qui officia deserunt mollit anim id est laborum. </p>
<!-- <h2>Posts</h2>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris
nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum
dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa
qui officia deserunt mollit anim id est laborum. </p> -->
</div>
</main>
<footer>
<span><img src="assets/copyleft.svg" width="12" height="12"/> 2020-2022 j-james </span>
</footer>
</body>
</html>
*/
|
