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+package model.css;
+
+import org.javatuples.*;
+
+import java.util.*;
+
+/*
+ * RULES ::= (RULE)+
+ * RULE ::= SELECTORS '{' (PROPERTY | (PROPERTY ';')*) '}'
+ * SELECTORS ::= SELECTOR (COMBINATOR SELECTOR)*
+ * SELECTOR ::= TAG | '#' WORD | '.' WORD
+ * COMBINATOR ::= '<' | '*' | '~' | ' ' | ...
+ * PROPERTY ::= ATTRIBUTE ':' VALUE
+ * ATTRIBUTE ::= 'color' | 'text' | ...
+ * VALUE ::= ??? idk lol
+ */
+
+/*
+ * body {
+ * background-color: #f0f0f2;
+ * margin: 0;
+ * padding: 0;
+ * font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI",
+ * "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
+ *
+ * }
+ * div {
+ * width: 600px;
+ * margin: 5em auto;
+ * padding: 2em;
+ * background-color: #fdfdff;
+ * border-radius: 0.5em;
+ * box-shadow: 2px 3px 7px 2px rgba(0,0,0,0.02);
+ * }
+ * a:link, a:visited {
+ * color: #38488f;
+ * text-decoration: none;
+ * }
+ * @media (max - width : 700px) {
+ * div {
+ * margin: 0 auto;
+ * width: auto;
+ * }
+ * }
+ */
+
+/**
+ * This class assumes that it is getting _valid CSS_: that is, the style between two tags
+ * of a style block, or the raw content of a .css file.
+ * Making sure this assumption holds is extremely important for program robustness.
+ * We do not check for validity, i.e. throw any exceptions - the driving principle of web standards is to "fail softly".
+ */
+public class CssParser {
+
+ /**
+ * CSS is nice to parse, and so we have a relatively small number of parser states.
+ */
+ private enum ParserState {
+ SELECTORS, MEDIA_SELECTORS,
+ ATTRIBUTE, VALUE, // PROPERTIES::PROPERTY::ATTRIBUTE, PROPRETIES::PROPERTY::VALUE
+ SINGLE_QUOTES, DOUBLE_QUOTES, // VALUE::SINGLE_QUOTES, VALUE::DOUBLE_QUOTES
+ }
+
+ /**
+ * Parses a (valid) CSS file in a left-to-right, leftmost-derivation style.
+ * It should be fast - I'd say something about time complexity if I knew anything about time complexity.
+ * No guarantees are made about invalid CSS files. Also, no guarantees are made about valid CSS files, lol.
+ */
+ public static ArrayList<Pair<String, ArrayList<Pair<String, String>>>> parseLL(String input) {
+
+ // parser buffers
+ // essentially the CssTree type
+ var result = new ArrayList<Pair<String, ArrayList<Pair<String, String>>>>();
+ var currentSelector = "";
+ var currentRule = new ArrayList<Pair<String, String>>();
+ var currentProperty = "";
+ var currentValue = "";
+
+ // We safely assume to start by reading a selector.
+ ParserState state = ParserState.SELECTORS;
+
+ for (char c : input.toCharArray()) {
+ // System.out.print(state);
+ // System.out.println(" " + c);
+ switch (state) {
+ case SELECTORS:
+ switch (c) {
+ case '@':
+ if (currentSelector.equals("")) {
+ state = ParserState.MEDIA_SELECTORS;
+ } else {
+ currentSelector += c;
+ }
+ break;
+ case '{':
+ state = ParserState.ATTRIBUTE;
+ break;
+ case ' ': case '\n':
+ break;
+ // todo: do better than blindly create a string; pattern match on css selectors
+ default:
+ currentSelector += c;
+ break;
+ }
+ break;
+ case MEDIA_SELECTORS:
+ switch (c) {
+ // todo: don't entirely disregard media queries, also split between @media/@...
+ case '{':
+ state = ParserState.SELECTORS;
+ // discard currentSelector
+ currentSelector = "";
+ break;
+ default:
+ currentSelector += c;
+ break;
+ }
+ break;
+ case ATTRIBUTE:
+ switch (c) {
+ case ':':
+ state = ParserState.VALUE;
+ break;
+ case '}':
+ state = ParserState.SELECTORS;
+ if (!currentValue.equals("") || !currentProperty.equals("")) {
+ System.out.println("something's wrong");
+ currentProperty = "";
+ currentValue = "";
+ }
+ result.add(new Pair<>(currentSelector, currentRule));
+ System.out.println(currentRule);
+ currentSelector = "";
+ currentRule = new ArrayList<>();
+ break;
+ case ' ': case '\n':
+ break;
+ default:
+ currentProperty += c;
+ break;
+ }
+ break;
+ case VALUE:
+ switch (c) {
+ case ';':
+ state = ParserState.ATTRIBUTE;
+ currentRule.add(new Pair<>(currentProperty, currentValue));
+ currentProperty = "";
+ currentValue = "";
+ break;
+ case '}':
+ state = ParserState.SELECTORS;
+ if (!currentValue.equals("") || !currentProperty.equals("")) {
+ currentRule.add(new Pair<>(currentProperty, currentValue));
+ currentProperty = "";
+ currentValue = "";
+ }
+ result.add(new Pair<>(currentSelector, currentRule));
+ currentSelector = "";
+ currentRule = new ArrayList<>();
+ break;
+ case '\'':
+ state = ParserState.SINGLE_QUOTES;
+ currentValue += c;
+ break;
+ case '\"':
+ state = ParserState.DOUBLE_QUOTES;
+ currentValue += c;
+ break;
+ case ' ': case '\n':
+ break;
+ default:
+ currentValue += c;
+ break;
+ }
+ break;
+ // quotes in css are exclusively? for paths: so we want to include the quotes themselves
+ case SINGLE_QUOTES:
+ switch (c) {
+ case '\'':
+ state = ParserState.VALUE;
+ currentValue += c;
+ break;
+ default:
+ currentValue += c;
+ break;
+ }
+ break;
+ case DOUBLE_QUOTES:
+ switch (c) {
+ case '\"':
+ state = ParserState.VALUE;
+ currentValue += c;
+ break;
+ default:
+ currentValue += c;
+ break;
+ }
+ break;
+ }
+ }
+ return result;
+ }
+
+ /**
+ * Takes an input string with units and returns out the value in pixels.
+ * This is a fault-tolerant system.
+ * When given an invalid string (i.e. "12p53x"), it will produce an invalid result instead of throwing.
+ * However, it should parse every valid string correctly.
+ */
+ private double parseUnits(String input) {
+ String numbers = "";
+ String units = "";
+ // imagine making a language without iterable strings, fml
+ for (int i = 0; i < input.length(); i++) {
+ char c = input.charAt(i);
+ if (Character.isDigit(c) || c == '.' || c == '-') {
+ numbers += c;
+ } else {
+ units += c;
+ }
+ }
+ double value;
+ try {
+ value = Float.parseFloat(numbers);
+ } catch (NumberFormatException e) {
+ System.out.printf("Did not parse a float from %s, proceeding with value 0.0...%n", numbers);
+ value = 0.0;
+ }
+ // god case/break is such a fault-provoking design i hate it
+ // good thing we avoid breaks entirely here lmao
+ switch (units) {
+ // absolute units
+ case "px": return value;
+ case "pc": return value * 16;
+ case "pt": return value * (4.0 / 3.0);
+ case "cm": return value * 37.8;
+ case "mm": return value * 378;
+ case "Q": return value * 1512;
+ case "in": return value * 96;
+ // not handled: % em ex ch rem lh rlh vw vh vmin vmax vb vi svw svh lvw lvh dvw dvh
+ default:
+ System.out.printf("Unit %s not implemented, defaulting to %s in pixels...%n", units, value);
+ return value;
+ }
+ }
+}
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