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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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