parse-css.js

"use strict";
(function (root, factory) {
    // Universal Module Definition (UMD) to support AMD, CommonJS/Node.js,
    // Rhino, and plain browser loading.
    if (typeof define === 'function' && define.amd) {
        define(['exports'], factory);
    } else if (typeof exports !== 'undefined') {
        factory(exports);
    } else {
        factory(root);
    }
}(this, function (exports) {

function between(num, first, last) { return num >= first && num <= last; }
function digit(code) { return between(code, 0x30,0x39); }
function hexdigit(code) { return digit(code) || between(code, 0x41,0x46) || between(code, 0x61,0x66); }
function uppercaseletter(code) { return between(code, 0x41,0x5a); }
function lowercaseletter(code) { return between(code, 0x61,0x7a); }
function letter(code) { return uppercaseletter(code) || lowercaseletter(code); }
function nonascii(code) {
	return (
		code == 0xb7 ||
		between(code, 0xc0, 0xd6) ||
		between(code, 0xd8, 0xf6) ||
		between(code, 0xf8, 0x37d) ||
		between(code, 0x37f, 0x1fff) ||
		code == 0x200c ||
		code == 0x200d ||
		code == 0x203f ||
		code == 0x2040 ||
		between(code, 0x2070, 0x218f) ||
		between(code, 0x2c00, 0x2fef) ||
		between(code, 0x3001, 0xd7ff) ||
		between(code, 0xf900, 0xfdcf) ||
		between(code, 0xfdf0, 0xfffd) ||
		code >= 0x10000
	);
}
function namestartchar(code) { return letter(code) || nonascii(code) || code == 0x5f; }
function namechar(code) { return namestartchar(code) || digit(code) || code == 0x2d; }
function nonprintable(code) { return between(code, 0,8) || code == 0xb || between(code, 0xe,0x1f) || code == 0x7f; }
function newline(code) { return code == 0xa; }
function whitespace(code) { return newline(code) || code == 9 || code == 0x20; }
function badescape(code) { return newline(code) || isNaN(code); }
function surrogate(code) { return between(code, 0xd800, 0xdfff); }

var maximumallowedcodepoint = 0x10ffff;

class InvalidCharacterError extends Error {
	constructor(message) {
		super();
		this.name = "InvalidCharacterError";
		this.message = message;
	}
}

function preprocess(str) {
	// Turn a string into an array of code points,
	// following the preprocessing cleanup rules.
	var codepoints = [];
	for(var i = 0; i < str.length; i++) {
		var code = str.charCodeAt(i);
		if(code == 0xd && str.charCodeAt(i+1) == 0xa) {
			code = 0xa; i++;
		}
		if(code == 0xd || code == 0xc) code = 0xa;
		if(code == 0x0) code = 0xfffd;
		if(between(code, 0xd800, 0xdbff) && between(str.charCodeAt(i+1), 0xdc00, 0xdfff)) {
			// Decode a surrogate pair into an astral codepoint.
			var lead = code - 0xd800;
			var trail = str.charCodeAt(i+1) - 0xdc00;
			code = Math.pow(2, 16) + lead * Math.pow(2, 10) + trail;
			i++;
		}
		codepoints.push(code);
	}
	return codepoints;
}

function asciiCaselessMatch(s1, s2) {
	return s1.toLowerCase() == s2.toLowerCase();
}

function tokenize(str) {
	str = preprocess(str);
	var i = -1;
	var tokens = [];
	var code;

	// Line number information.
	var line = 0;
	var column = 0;
	// The only use of lastLineLength is in reconsume().
	var lastLineLength = 0;
	var incrLineno = function() {
		line += 1;
		lastLineLength = column;
		column = 0;
	};
	var locStart = {line:line, column:column};

	var codepoint = function(i) {
		if(i >= str.length) {
			return -1;
		}
		return str[i];
	}
	var next = function(num) {
		if(num === undefined)
			num = 1;
		if(num > 3)
			throw "Spec Error: no more than three codepoints of lookahead.";
		return codepoint(i+num);
	};
	var consume = function(num) {
		if(num === undefined)
			num = 1;
		i += num;
		code = codepoint(i);
		if(newline(code)) incrLineno();
		else column += num;
		//console.log('Consume '+i+' '+String.fromCharCode(code) + ' 0x' + code.toString(16));
		return true;
	};
	var reconsume = function() {
		i -= 1;
		if (newline(code)) {
			line -= 1;
			column = lastLineLength;
		} else {
			column -= 1;
		}
		locStart.line = line;
		locStart.column = column;
		return true;
	};
	var eof = function(codepoint) {
		if(codepoint === undefined) codepoint = code;
		return codepoint == -1;
	};
	var donothing = function() {};
	var parseerror = function() { console.log("Parse error at index " + i + ", processing codepoint 0x" + code.toString(16) + ".");return true; };

	var consumeAToken = function() {
		consumeComments();
		consume();
		if(whitespace(code)) {
			while(whitespace(next())) consume();
			return new WhitespaceToken;
		}
		else if(code == 0x22) return consumeAStringToken();
		else if(code == 0x23) {
			if(namechar(next()) || areAValidEscape(next(1), next(2))) {
				const isIdent = wouldStartAnIdentifier(next(1), next(2), next(3));
				return new HashToken(consumeAName(), isIdent);
			} else {
				return new DelimToken(code);
			}
		}
		else if(code == 0x27) return consumeAStringToken();
		else if(code == 0x28) return new OpenParenToken();
		else if(code == 0x29) return new CloseParenToken();
		else if(code == 0x2b) {
			if(startsWithANumber()) {
				reconsume();
				return consumeANumericToken();
			} else {
				return new DelimToken(code);
			}
		}
		else if(code == 0x2c) return new CommaToken();
		else if(code == 0x2d) {
			if(startsWithANumber()) {
				reconsume();
				return consumeANumericToken();
			} else if(next(1) == 0x2d && next(2) == 0x3e) {
				consume(2);
				return new CDCToken();
			} else if(startsWithAnIdentifier()) {
				reconsume();
				return consumeAnIdentlikeToken();
			} else {
				return new DelimToken(code);
			}
		}
		else if(code == 0x2e) {
			if(startsWithANumber()) {
				reconsume();
				return consumeANumericToken();
			} else {
				return new DelimToken(code);
			}
		}
		else if(code == 0x3a) return new ColonToken;
		else if(code == 0x3b) return new SemicolonToken;
		else if(code == 0x3c) {
			if(next(1) == 0x21 && next(2) == 0x2d && next(3) == 0x2d) {
				consume(3);
				return new CDOToken();
			} else {
				return new DelimToken(code);
			}
		}
		else if(code == 0x40) {
			if(wouldStartAnIdentifier(next(1), next(2), next(3))) {
				return new AtKeywordToken(consumeAName());
			} else {
				return new DelimToken(code);
			}
		}
		else if(code == 0x5b) return new OpenSquareToken();
		else if(code == 0x5c) {
			if(startsWithAValidEscape()) {
				reconsume();
				return consumeAnIdentlikeToken();
			} else {
				parseerror();
				return new DelimToken(code);
			}
		}
		else if(code == 0x5d) return new CloseSquareToken();
		else if(code == 0x7b) return new OpenCurlyToken();
		else if(code == 0x7d) return new CloseCurlyToken();
		else if(digit(code)) {
			reconsume();
			return consumeANumericToken();
		}
		else if(namestartchar(code)) {
			reconsume();
			return consumeAnIdentlikeToken();
		}
		else if(eof()) return new EOFToken();
		else return new DelimToken(code);
	};

	var consumeComments = function() {
		while(next(1) == 0x2f && next(2) == 0x2a) {
			consume(2);
			while(true) {
				consume();
				if(code == 0x2a && next() == 0x2f) {
					consume();
					break;
				} else if(eof()) {
					parseerror();
					return;
				}
			}
		}
	};

	var consumeANumericToken = function() {
		var {value, isInteger, sign} = consumeANumber();
		if(wouldStartAnIdentifier(next(1), next(2), next(3))) {
			const unit = consumeAName();
			return new DimensionToken(value, unit, sign);
		} else if(next() == 0x25) {
			consume();
			return new PercentageToken(value, sign);
		} else {
			return new NumberToken(value, isInteger, sign);
		}
	};

	var consumeAnIdentlikeToken = function() {
		var str = consumeAName();
		if(str.toLowerCase() == "url" && next() == 0x28) {
			consume();
			while(whitespace(next(1)) && whitespace(next(2))) consume();
			if(next() == 0x22 || next() == 0x27) {
				return new FunctionToken(str);
			} else if(whitespace(next()) && (next(2) == 0x22 || next(2) == 0x27)) {
				return new FunctionToken(str);
			} else {
				return consumeAURLToken();
			}
		} else if(next() == 0x28) {
			consume();
			return new FunctionToken(str);
		} else {
			return new IdentToken(str);
		}
	};

	var consumeAStringToken = function(endingCodePoint) {
		if(endingCodePoint === undefined) endingCodePoint = code;
		var string = "";
		while(consume()) {
			if(code == endingCodePoint || eof()) {
				return new StringToken(string);
			} else if(newline(code)) {
				parseerror();
				reconsume();
				return new BadStringToken();
			} else if(code == 0x5c) {
				if(eof(next())) {
					donothing();
				} else if(newline(next())) {
					consume();
				} else {
					string += String.fromCodePoint(consumeEscape())
				}
			} else {
				string += String.fromCodePoint(code);
			}
		}
	};

	var consumeAURLToken = function() {
		var token = new URLToken("");
		while(whitespace(next())) consume();
		if(eof(next())) return token;
		while(consume()) {
			if(code == 0x29 || eof()) {
				return token;
			} else if(whitespace(code)) {
				while(whitespace(next())) consume();
				if(next() == 0x29 || eof(next())) {
					consume();
					return token;
				} else {
					consumeTheRemnantsOfABadURL();
					return new BadURLToken();
				}
			} else if(code == 0x22 || code == 0x27 || code == 0x28 || nonprintable(code)) {
				parseerror();
				consumeTheRemnantsOfABadURL();
				return new BadURLToken();
			} else if(code == 0x5c) {
				if(startsWithAValidEscape()) {
					token.value += String.fromCodePoint(consumeEscape());
				} else {
					parseerror();
					consumeTheRemnantsOfABadURL();
					return new BadURLToken();
				}
			} else {
				token.value += String.fromCodePoint(code);
			}
		}
	};

	var consumeEscape = function() {
		// Assume the the current character is the \
		// and the next code point is not a newline.
		consume();
		if(hexdigit(code)) {
			// Consume 1-6 hex digits
			var digits = [code];
			for(var total = 0; total < 5; total++) {
				if(hexdigit(next())) {
					consume();
					digits.push(code);
				} else {
					break;
				}
			}
			if(whitespace(next())) consume();
			var value = parseInt(digits.map(function(x){return String.fromCharCode(x);}).join(''), 16);
			if( value > maximumallowedcodepoint ) value = 0xfffd;
			return value;
		} else if(eof()) {
			return 0xfffd;
		} else {
			return code;
		}
	};

	var areAValidEscape = function(c1, c2) {
		if(c1 != 0x5c) return false;
		if(newline(c2)) return false;
		return true;
	};
	var startsWithAValidEscape = function() {
		return areAValidEscape(code, next());
	};

	var wouldStartAnIdentifier = function(c1, c2, c3) {
		if(c1 == 0x2d) {
			return namestartchar(c2) || c2 == 0x2d || areAValidEscape(c2, c3);
		} else if(namestartchar(c1)) {
			return true;
		} else if(c1 == 0x5c) {
			return areAValidEscape(c1, c2);
		} else {
			return false;
		}
	};
	var startsWithAnIdentifier = function() {
		return wouldStartAnIdentifier(code, next(1), next(2));
	};

	var wouldStartANumber = function(c1, c2, c3) {
		if(c1 == 0x2b || c1 == 0x2d) {
			if(digit(c2)) return true;
			if(c2 == 0x2e && digit(c3)) return true;
			return false;
		} else if(c1 == 0x2e) {
			if(digit(c2)) return true;
			return false;
		} else if(digit(c1)) {
			return true;
		} else {
			return false;
		}
	};
	var startsWithANumber = function() {
		return wouldStartANumber(code, next(1), next(2));
	};

	var consumeAName = function() {
		var result = "";
		while(consume()) {
			if(namechar(code)) {
				result += String.fromCodePoint(code);
			} else if(startsWithAValidEscape()) {
				result += String.fromCodePoint(consumeEscape());
			} else {
				reconsume();
				return result;
			}
		}
	};

	var consumeANumber = function() {
		let isInteger = true;
		let sign;
		let numberPart = "";
		let exponentPart = "";
		if(next() == 0x2b || next() == 0x2d) {
			consume();
			sign = String.fromCodePoint(code);
			numberPart += sign;
		}
		while(digit(next())) {
			consume();
			numberPart += String.fromCodePoint(code);
		}
		if(next(1) == 0x2e && digit(next(2))) {
			consume();
			numberPart += ".";
			while(digit(next())) {
				consume();
				numberPart += String.fromCodePoint(code);
			}
			isInteger = false;
		}
		var c1 = next(1), c2 = next(2), c3 = next(3);
		const eDigit = (c1 == 0x45 || c1 == 0x65) && digit(c2);
		const eSignDigit = (c1 == 0x45 || c1 == 0x65) && (c2 == 0x2b || c2 == 0x2d) && digit(c3);
		if(eDigit || eSignDigit) {
			consume();
			if(eSignDigit) {
				consume();
				exponentPart += String.fromCodePoint(code);
			}
			while(digit(next())) {
				consume();
				exponentPart += String.fromCodePoint(code);
			}
			isInteger = false;
		}
		let value = +numberPart;
		if(exponentPart) value = value * Math.pow(10, +exponentPart);

		return {value, isInteger, sign};
	};

	var consumeTheRemnantsOfABadURL = function() {
		while(consume()) {
			if(code == 0x29 || eof()) {
				return;
			} else if(startsWithAValidEscape()) {
				consumeEscape();
				donothing();
			} else {
				donothing();
			}
		}
	};



	var iterationCount = 0;
	while(!eof(next())) {
		tokens.push(consumeAToken());
		iterationCount++;
		if(iterationCount > str.length*2) return "I'm infinite-looping!";
	}
	return tokens;
}

class CSSParserToken {
	constructor(type) {
		this.type = type;
	}

	toJSON() { return {type:this.type}; }
	toString() { return this.type; }
	toSource() { throw new Exception("Not implemented."); }
}
//toJSON()
//toString()
//toSource()

class BadStringToken extends CSSParserToken {
	constructor() {
		super("BADSTRING");
	}
	toSource() { return '"\n"'; }
}

class BadURLToken extends CSSParserToken {
	constructor() {
		super("BADURL");
	}
	toSource() { return "url(BADURL '')"}
}
BadURLToken.prototype.tokenType = "BADURL";

class WhitespaceToken extends CSSParserToken {
	constructor() {
		super("WHITESPACE");
	}
	toString() { return "WS"; }
	toSource() { return " "; }
}

class CDOToken extends CSSParserToken {
	constructor() {
		super("CDO");
	}
	toSource() { return "<!--"; }
}

class CDCToken extends CSSParserToken {
	constructor() {
		super("CDC");
	}
	toSource() { return "-->"; }
}

class ColonToken extends CSSParserToken {
	constructor() {
		super("COLON");
	}
	toSource() { return ":"; }
}

class SemicolonToken extends CSSParserToken {
	constructor() {
		super("SEMICOLON");
	}
	toSource() { return ";" };
}

class CommaToken extends CSSParserToken {
	constructor() {
		super("COMMA");
	}
	toSource() { return "," }
}

class OpenCurlyToken extends CSSParserToken {
	constructor() {
		super("OPEN-CURLY");
		this.grouping = true;
		this.mirror = CloseCurlyToken;
	}
	toSource() { return "{"; }
}

class CloseCurlyToken extends CSSParserToken {
	constructor() {
		super("CLOSE-CURLY");
	}
	toSource() { return "}"; }
}

class OpenSquareToken extends CSSParserToken {
	constructor() {
		super("OPEN-SQUARE");
		this.grouping = true;
		this.mirror = CloseSquareToken;
	}
	toSource() { return "["; }
}

class CloseSquareToken extends CSSParserToken {
	constructor() {
		super("CLOSE-SQUARE");
	}
	toSource() { return "]"; }
}

class OpenParenToken extends CSSParserToken {
	constructor() {
		super("OPEN-PAREN");
		this.grouping = true;
		this.mirror = CloseParenToken;
	}
	toSource() { return "("; }
}

class CloseParenToken extends CSSParserToken {
	constructor() {
		super("CLOSE-PAREN");
	}
	toSource() { return ")"; }
}

class EOFToken extends CSSParserToken {
	constructor() {
		super("EOF");
	}
	toSource() { return ""; }
}

class DelimToken extends CSSParserToken {
	constructor(val) {
		super("DELIM");
		if(typeof val == "number") {
			val = String.fromCodePoint(val);
		} else {
			val = String(val);
		}
		this.value = val;
	}
	toString() { return `DELIM(${this.val})`; }
	toJSON() { return {type:this.type, value:this.value}; }
	toSource() {
		if(this.value == "\\") return "\\\n";
		return this.value;
	}
}

class IdentToken extends CSSParserToken {
	constructor(val) {
		super("IDENT");
		this.value = val;
	}
	toString() { return `IDENT(${this.value})`; }
	toJSON() { return {type:this.type, value:this.value}; }
	toSource() { return escapeIdent(this.value); }
}

class FunctionToken extends CSSParserToken {
	constructor(val) {
		super("FUNCTION");
		this.value = val;
		this.mirror = CloseParenToken;
	}
	toString() { return `FUNCTION(${this.value})`; }
	toJSON() { return {type:this.type, value:this.value}; }
	toSource() { return escapeIdent(this.value) + "("; }
}

class AtKeywordToken extends CSSParserToken {
	constructor(val) {
		super("AT-KEYWORD");
		this.value = val;
	}
	toString() { return `AT(${this.value})`; }
	toJSON() { return {type:this.type, value:this.value }; }
	toSource() { return "@" + escapeIdent(this.value); }
}

class HashToken extends CSSParserToken {
	constructor(val, isIdent) {
		super("HASH");
		this.value = val;
		this.isIdent = isIdent;
	}
	toString() { return `HASH(${this.value})`; }
	toJSON() { return {type:this.type, value:this.value, isIdent:this.isIdent}; }
	toSource() {
		if(this.isIdent) {
			return "#" + escapeIdent(this.value);
		}
		return "#" + escapeHash(this.value);
	}
}

class StringToken extends CSSParserToken {
	constructor(val) {
		super("STRING");
		this.value = val;
	}
	toString() { return `STRING(${this.value})`; }
	toJSON() { return {type:this.type, value:this.value}; }
	toSource() { return `"${escapeString(this.value)}"`; }
}

class URLToken extends CSSParserToken {
	constructor(val) {
		super("URL");
		this.value = val;
	}
	toString() { return `URL(${this.value})`; }
	toJSON() { return {type:this.type, value:this.value}; }
	toSource() { return `url("${escapeString(this.value)}")`; }
}

class NumberToken extends CSSParserToken {
	constructor(val, isInteger, sign=undefined) {
		super("NUMBER");
		this.value = val;
		this.isInteger = isInteger;
		this.sign = sign;
	}
	toString() {
		const name = this.isInteger ? "INT" : "NUMBER";
		const sign = this.sign == "+" ? "+" : "";
		return `${name}(${sign}${this.value})`;
	}
	toJSON() { return {type:this.type, value:this.value, isInteger:this.isInteger, sign:this.sign}; }
	toSource() { return formatNumber(this.value, this.sign); }
}

class PercentageToken extends CSSParserToken {
	constructor(val, sign=undefined) {
		super("PERCENTAGE");
		this.value = val;
		this.sign = sign;
	}
	toString() {
		const sign = this.sign == "+" ? "+" : "";
		return `PERCENTAGE(${sign}${this.value})`;
	}
	toJSON() { return {type:this.type, value:this.value, sign:this.sign}; }
	toSource() { return `${formatNumber(this.value, this.sign)}%`; }
}

class DimensionToken extends CSSParserToken {
	constructor(val, unit, sign=undefined) {
		super("DIMENSION");
		this.value = val;
		this.unit = unit;
		this.sign = sign;
	}
	toString() {
		const sign = this.sign == "+" ? "+" : "";
		return `DIM(${sign}${this.value}, ${this.unit})`;
	}
	toJSON() { return {type:this.type, value:this.value, unit:this.unit}; }
	toSource() {
		let unit = escapeIdent(this.unit);
		if(unit[0].toLowerCase() == "e" && (unit[1] == "-" || digit(unit[1]))) {
			// Unit is ambiguous with scinot
			// Remove the leading "e", replace with escape.
			unit = "\\65 " + unit.slice(1, unit.length);
		}
		return `${formatNumber(this.value, this.sign)}${unit}`;
	}
}

function escapeIdent(string) {
	return Array.from(String(string), (e,i)=>{
		const code = e.codePointAt(0);
		if(i == 0) {
			if(namestartchar(code)) return e;
			return escapeIdentCode(code);
		}
		if(namechar(code)) return e;
		return escapeIdentCode(code);
	}).join("");
}

function escapeIdentCode(code) {
	if(digit(code) || letter(code)) {
		return `\\${code.toString(16)} `;
	}
	return "\\"+String.fromCodePoint(code);
}

function escapeHash(string) {
	// Escapes the value (after the #) of a hash.
	return Array.from(String(string), e=>{
		const code = e.codePointAt(0);
		if(namechar(code)) return e;
		return escapeIdentCode(code);
	}).join("");
}

function escapeString(string) {
	// Escapes the contents (between the quotes) of a string
	return Array.from(String(string), e=>{
		const code = e.codePointAt(0);
		if(between(code, 0x0, 0x1f)
			|| code == 0x7f
			|| code == 0x22
			|| code == 0x5c
		) {
			return "\\" + code.toString(16) + " ";
		}
		return e;
	}).join("");
}

function formatNumber(num, sign=undefined) {
	// TODO: Fix this to match CSS stringification behavior.
	return (sign == "+" ? "+" : "") + String(num);
}

// Exportation.
exports.tokenize = tokenize;
exports.IdentToken = IdentToken;
exports.FunctionToken = FunctionToken;
exports.AtKeywordToken = AtKeywordToken;
exports.HashToken = HashToken;
exports.StringToken = StringToken;
exports.BadStringToken = BadStringToken;
exports.URLToken = URLToken;
exports.BadURLToken = BadURLToken;
exports.DelimToken = DelimToken;
exports.NumberToken = NumberToken;
exports.PercentageToken = PercentageToken;
exports.DimensionToken = DimensionToken;
exports.WhitespaceToken = WhitespaceToken;
exports.CDOToken = CDOToken;
exports.CDCToken = CDCToken;
exports.ColonToken = ColonToken;
exports.SemicolonToken = SemicolonToken;
exports.CommaToken = CommaToken;
exports.OpenParenToken = OpenParenToken;
exports.CloseParenToken = CloseParenToken;
exports.OpenSquareToken = OpenSquareToken;
exports.CloseSquareToken = CloseSquareToken;
exports.OpenCurlyToken = OpenCurlyToken;
exports.CloseCurlyToken = CloseCurlyToken;
exports.EOFToken = EOFToken;
exports.CSSParserToken = CSSParserToken;

class TokenStream {
	constructor(tokens) {
		// Assume that tokens is an array.
		this.tokens = tokens;
		this.i = 0;
		this.marks = [];
	}
	nextToken() {
		if(this.i < this.tokens.length) return this.tokens[this.i];
		return new EOFToken();
	}
	empty() {
		return this.i >= this.tokens.length;
	}
	consumeToken() {
		const tok = this.nextToken();
		this.i++;
		return tok;
	}
	discardToken() {
		this.i++;
	}
	mark() {
		this.marks.push(this.i);
		return this;
	}
	restoreMark() {
		if(this.marks.length) {
			this.i = this.marks.pop();
			return this;
		}
		throw new Error("No marks to restore.");
	}
	discardMark() {
		if(this.marks.length) {
			this.marks.pop();
			return this;
		}
		throw new Error("No marks to restore.");
	}
	discardWhitespace() {
		while(this.nextToken() instanceof WhitespaceToken) {
			this.discardToken();
		}
		return this;
	}
}

function parseerror(s, msg) {
	console.log("Parse error at token " + s.i + ": " + s.tokens[i] + ".\n" + msg);
	return true;
}

function consumeAStylesheetsContents(s) {
	const rules = [];
	while(1) {
		const token = s.nextToken();
		if(token instanceof WhitespaceToken) {
			s.discardToken();
		} else if(token instanceof EOFToken) {
			return rules;
		} else if(token instanceof CDOToken || token instanceof CDCToken) {
			s.discardToken();
		} else if(token instanceof AtKeywordToken) {
			const rule = consumeAnAtRule(s)
			if(rule) rules.push(rule);
		} else {
			const rule = consumeAQualifiedRule(s);
			if(rule) rules.push(rule);
		}
	}
}

function consumeAnAtRule(s, nested=false) {
	const token = s.consumeToken();
	if(!token instanceof AtKeywordToken)
		throw new Error("consumeAnAtRule() called with an invalid token stream state.");
	const rule = new AtRule(token.value);
	while(1) {
		const token = s.nextToken();
		if(token instanceof SemicolonToken || token instanceof EOFToken) {
			s.discardToken();
			return filterValid(rule);
		} else if(token instanceof CloseCurlyToken) {
			if(nested) return filterValid(rule);
			else {
				parseerror(s, "Hit an unmatched } in the prelude of an at-rule.");
				rule.prelude.push(consumeToken(s));
			}
		} else if(token instanceof OpenCurlyToken) {
			[rule.declarations, rule.rules] = consumeABlock(s);
			return filterValid(rule);
		} else {
			rule.prelude.push(consumeAComponentValue(s));
		}
	}
}

function consumeAQualifiedRule(s, nested=false, stopToken=EOFToken) {
	var rule = new QualifiedRule();
	while(1) {
		const token = s.nextToken();
		if(token instanceof EOFToken || token instanceof stopToken) {
			parseerror(s, "Hit EOF or semicolon when trying to parse the prelude of a qualified rule.");
			return;
		} else if(token instanceof CloseCurlyToken) {
			parseerror("Hit an unmatched } in the prelude of a qualified rule.");
			if(nested) return;
			else {
				rule.prelude.push(consumeToken(s));
			}
		} else if(token instanceof OpenCurlyToken) {
			if(looksLikeACustomProperty(rule.prelude)) {
				consumeTheRemnantsOfABadDeclaration(s, nested);
				return;
			}
			[rule.declarations, rule.rules] = consumeABlock(s);
			return filterValid(rule);
		} else {
			rule.prelude.push(consumeAComponentValue(s));
		}
	}
}

function looksLikeACustomProperty(tokens) {
	let foundDashedIdent = false;
	for(const token of tokens) {
		if(token instanceof WhitespaceToken) continue;
		if(!foundDashedIdent && token instanceof IdentToken && token.value.slice(0, 2) == "--") {
			foundDashedIdent = true;
			continue;
		}
		if(foundDashedIdent && token instanceof ColonToken) {
			return true;
		}
		return false;
	}
	return false;
}

function consumeABlock(s) {
	if(!s.nextToken() instanceof OpenCurlyToken) {
		throw new Error("consumeABlock() called with an invalid token stream state.");
	}
	s.discardToken();
	const [decls, rules] = consumeABlocksContents(s);
	s.discardToken();
	return [decls, rules];
}

function consumeABlocksContents(s) {
	const decls = [];
	const rules = [];
	while(1) {
		const token = s.nextToken();
		if(token instanceof WhitespaceToken || token instanceof SemicolonToken) {
			s.discardToken();
		} else if(token instanceof EOFToken || token instanceof CloseCurlyToken) {
			return [decls, rules];
		} else if(token instanceof AtKeywordToken) {
			const rule = consumeAnAtRule(s, true);
			if(rule) rules.push(rule);
		} else {
			s.mark();
			const decl = consumeADeclaration(s, true);
			if(decl) {
				decls.push(decl);
				s.discardMark();
				continue;
			}
			s.restoreMark();
			const rule = consumeAQualifiedRule(s, true, SemicolonToken);
			if(rule) rules.push(rule);
		}
	}
}

function consumeADeclaration(s, nested=false) {
	let decl;
	if(s.nextToken() instanceof IdentToken) {
		decl = new Declaration(s.consumeToken().value);
	} else {
		consumeTheRemnantsOfABadDeclaration(s, nested);
		return;
	}
	s.discardWhitespace();
	if(s.nextToken() instanceof ColonToken) {
		s.discardToken();
	} else {
		consumeTheRemnantsOfABadDeclaration(s, nested);
		return;
	}
	s.discardWhitespace();
	decl.value = consumeAListOfComponentValues(s, nested, SemicolonToken);

	var foundImportant = false;
	for(var i = decl.value.length - 1; i >= 0; i--) {
		if(decl.value[i] instanceof WhitespaceToken) {
			continue;
		} else if(!foundImportant && decl.value[i] instanceof IdentToken && asciiCaselessMatch(decl.value[i].value, "important")) {
			foundImportant = true;
		} else if(foundImportant && decl.value[i] instanceof DelimToken && decl.value[i].value == "!") {
			decl.value.length = i;
			decl.important = true;
			break;
		} else {
			break;
		}
	}

	var i = decl.value.length - 1;
	while(decl.value[i] instanceof WhitespaceToken) {
		decl.value.length = i;
		i--;
	}
	return filterValid(decl);
}

function consumeTheRemnantsOfABadDeclaration(s, nested) {
	while(1) {
		const token = s.nextToken();
		if(token instanceof EOFToken || token instanceof SemicolonToken) {
			s.discardToken();
			return;
		} else if(token instanceof CloseCurlyToken) {
			if(nested) return;
			else s.discardToken();
		} else {
			consumeAComponentValue(s);
		}
	}
}

function consumeAListOfComponentValues(s, nested=false, stopToken=EOFToken) {
	const values = [];
	while(1) {
		const token = s.nextToken();
		if(token instanceof EOFToken || token instanceof stopToken) {
			return values;
		} else if(token instanceof CloseCurlyToken) {
			if(nested) return values;
			else {
				parseerror(s, "Hit an unmatched } in a declaration value.");
				values.push(s.consumeToken());
			}
		} else {
			values.push(consumeAComponentValue(s));
		}
	}
}

function consumeAComponentValue(s) {
	const token = s.nextToken();
	if(token instanceof OpenCurlyToken || token instanceof OpenSquareToken || token instanceof OpenParenToken)
		return consumeASimpleBlock(s);
	if(token instanceof FunctionToken)
		return consumeAFunction(s);
	return s.consumeToken();
}

function consumeASimpleBlock(s) {
	if(!s.nextToken().mirror) {
		throw new Error("consumeASimpleBlock() called with an invalid token stream state.");
	}
	const start = s.nextToken();
	const block = new SimpleBlock(start.toSource());
	s.discardToken();
	while(1) {
		const token = s.nextToken();
		if(token instanceof EOFToken || token instanceof start.mirror) {
			s.discardToken();
			return block;
		} else {
			block.value.push(consumeAComponentValue(s));
		}
	}
}

function consumeAFunction(s) {
	if(!s.nextToken() instanceof FunctionToken) {
		throw new Error("consumeAFunction() called with an invalid token stream state.");
	}
	var func = new Func(s.consumeToken().value);
	while(1) {
		const token = s.nextToken();
		if(token instanceof EOFToken || token instanceof CloseParenToken) {
			s.discardToken();
			return func;
		} else {
			func.value.push(consumeAComponentValue(s));
		}
	}
}

function isValidInContext(construct, context) {
	// Trivial validator, without any special CSS knowledge.

	// All at-rules are valid, who cares.
	if(construct.type == "AT-RULE") return true;

	// Exclude qualified rules that ended up with a semicolon
	// in their prelude.
	// (Can only happen at the top level of a stylesheet.)
	if(construct.type == "QUALIFIED-RULE") {
		for(const val of construct.prelude) {
			if(val.type == "SEMICOLON") return false;
		}
		return true;
	}

	// Exclude properties that ended up with a {}-block
	// in their value, unless they're custom.
	if(construct.type == "DECLARATION") {
		if(construct.name.slice(0, 2) == "--") return true;
		for(const val of construct.value) {
			if(val.type == "BLOCK" && val.name == "{") return false;
		}
		return true;
	}
}

function filterValid(construct, context) {
	if(isValidInContext(construct, context)) return construct;
	return;
}

function normalizeInput(input) {
	if(typeof input == "string")
		return new TokenStream(tokenize(input));
	if(input instanceof TokenStream)
		return input;
	if(input.length !== undefined)
		return new TokenStream(input);
	else throw SyntaxError(input);
}

function parseAStylesheet(s) {
	s = normalizeInput(s);
	var sheet = new Stylesheet();
	sheet.rules = consumeAStylesheetsContents(s);
	return sheet;
}

function parseAStylesheetsContents(s) {
	s = normalizeInput(s);
	return consumeAStylesheetsContents(s);
}

function parseABlocksContents(s) {
	s = normalizeInput(s);
	return consumeABlocksContents(s);
}

function parseARule(s) {
	s = normalizeInput(s);
	let rule;
	s.discardWhitespace();
	if(s.nextToken() instanceof EOFToken) throw SyntaxError();
	if(s.nextToken() instanceof AtKeywordToken) {
		rule = consumeAnAtRule(s);
	} else {
		rule = consumeAQualifiedRule(s);
		if(!rule) throw SyntaxError();
	}
	s.discardWhitespace();
	if(s.nextToken() instanceof EOFToken) return rule;
	throw SyntaxError();
}

function parseADeclaration(s) {
	s = normalizeInput(s);
	s.discardWhitespace();
	const decl = consumeADeclaration(s);
	if(decl) return decl
	throw SyntaxError();
}

function parseAComponentValue(s) {
	s = normalizeInput(s);
	s.discardWhitespace();
	if(s.empty()) throw SyntaxError();
	const val = consumeAComponentValue(s);
	s.discardWhitespace();
	if(s.empty()) return val;
	throw SyntaxError();
}

function parseAListOfComponentValues(s) {
	s = normalizeInput(s);
	return consumeAListOfComponentValues(s);
}

function parseACommaSeparatedListOfComponentValues(s) {
	s = normalizeInput(s);
	const groups = [];
	while(!s.empty()) {
		groups.push(consumeAListOfComponentValues(s, false, CommaToken));
		s.discardToken();
	}
	return groups;
}


class CSSParserRule {
	constructor(type) { this.type = type; }
	toString(indent) {
		return JSON.stringify(this,null,indent);
	}
}

class Stylesheet extends CSSParserRule {
	constructor() {
		super("STYLESHEET");
		this.rules = [];
		return this;
	}
	toJSON() {
		return {
			type: this.type,
			rules: this.rules,
		}
	}
	toSource() {
		return this.rules.map(x=>x.toSource()).join("\n");
	}
}

class AtRule extends CSSParserRule {
	constructor(name) {
		super("AT-RULE");
		this.name = name;
		this.prelude = [];
		this.declarations = null;
		this.rules = null;
		return this;
	}
	toJSON() {
		return {
			type: this.type,
			name: this.name,
			prelude: this.prelude,
			declarations: this.declarations,
			rules: this.rules,
		}
	}
	toSource(indent=0) {
		let s = printIndent(indent) + "@" + escapeIdent(this.name);
		s += this.prelude.map(x=>x.toSource()).join("");
		if(this.declarations == null) {
			s += ";\n";
			return s;
		}
		s += "{\n";
		if(this.declarations.length) {
			s += this.declarations.map(x=>x.toSource(indent+1)).join("\n") + "\n";
		}
		if(this.rules.length) {
			s += this.rules.map(x=>x.toSource(indent+1)).join("\n") + "\n";
		}
		s += printIndent(indent) + "}";
		return s;
	}
}

class QualifiedRule extends CSSParserRule {
	constructor() {
		super("QUALIFIED-RULE");
		this.prelude = [];
		this.declarations = [];
		this.rules = [];
		return this;
	}
	toJSON() {
		return {
			type: this.type,
			prelude: this.prelude,
			declarations: this.declarations,
			rules: this.rules,
		}
	}
	toSource(indent=0) {
		let s = printIndent(indent);
		s += this.prelude.map(x=>x.toSource()).join("");
		s += "{\n";
		if(this.declarations.length) {
			s += this.declarations.map(x=>x.toSource(indent+1)).join("\n") + "\n";
		}
		if(this.rules.length) {
			s += this.rules.map(x=>x.toSource(indent+1)).join("\n") + "\n";
		}
		s += printIndent(indent) + "}";
		return s;
	}
}

class Declaration extends CSSParserRule {
	constructor(name) {
		super("DECLARATION")
		this.name = name;
		this.value = [];
		this.important = false;
		return this;
	}
	toJSON() {
		return {
			type: this.type,
			name: this.name,
			value: this.value,
			important: this.important,
		}
	}
	toSource(indent=0) {
		let s = printIndent(indent) + escapeIdent(this.name) + ": ";
		s += this.value.map(x=>x.toSource()).join("");
		if(this.important) {
			s += "!important";
		}
		s += ";";
		return s;
	}
}

class SimpleBlock extends CSSParserRule {
	constructor(type) {
		super("BLOCK");
		this.name = type;
		this.value = [];
		return this;
	}
	toJSON() {
		return {
			type: this.type,
			name: this.name,
			value: this.value,
		}
	}
	toSource() {
		const mirror = {"{":"}", "[":"]", "(":")"};
		return this.name + this.value.map(x=>x.toSource()).join("") + mirror[this.name];
	}
}

class Func extends CSSParserRule {
	constructor(name) {
		super("FUNCTION");
		this.name = name;
		this.value = [];
		return this;
	}
	toJSON() {
		return {
			type: this.type,
			name: this.name,
			value: this.value,
		}
	}
	toSource() {
		return escapeIdent(this.name) + "(" + this.value.map(x=>x.toSource()).join("") + ")";
	}
}

function printIndent(level) {
	return "\t".repeat(level);
}


// Exportation.
exports.CSSParserRule = CSSParserRule;
exports.Stylesheet = Stylesheet;
exports.AtRule = AtRule;
exports.QualifiedRule = QualifiedRule;
exports.Declaration = Declaration;
exports.SimpleBlock = SimpleBlock;
exports.Func = Func;
exports.parseAStylesheet = parseAStylesheet;
exports.parseAStylesheetsContents = parseAStylesheetsContents;
exports.parseABlocksContents = parseABlocksContents;
exports.parseARule = parseARule;
exports.parseADeclaration = parseADeclaration;
exports.parseAComponentValue = parseAComponentValue;
exports.parseAListOfComponentValues = parseAListOfComponentValues;
exports.parseACommaSeparatedListOfComponentValues = parseACommaSeparatedListOfComponentValues;

}));