/*

-> Design credit goes to Jaroslav Getman
-> https://dribbble.com/shots/2334270-004-Calculator

Calculator 2.0

This is the second iteration of this calculator, built with Vue and Vuex. You can find the code for this new version of the calculator and the old calculator here.

github.com/anthonykoch/calculator

TODO:
1. Make buttons show keypress when a keybind is pressed

FIXME:
1. Fix error where Expressions = ['(', '5', '*', '3', ')'] and mode is APPEND after ")". It should be insert
2. Even though pressing delete causes mutation CLEAR_ENTRY to fire, changing the state does nothing until a button has been pressed. Not sure if this is a problem with Vuex or the way I'm doing it.

*/

function main() {
	'use strict';

	const $ = document.querySelector.bind(document);

	const $app = $('.js-app');

	const templates = {

		calculatorButton: $(`[data-template="calculatorbutton"]`).innerHTML

	};

	const ACTION_CLEAR           = 'clear';
	const ACTION_CLEAR_ENTRY     = 'clearEntry';
	const ACTION_NEGATE          = 'negate';
	const ACTION_UPDATE_OPERATOR = 'updateOperator';
	const ACTION_APPEND_OPERAND  = 'appendOperand';
	const ACTION_ADD_PAREN       = 'addParen';
	const ACTION_BACKSPACE       = 'backspace';
	const ACTION_SHOW_TOTAL      = 'showTotal';

	const buttons = [
		{
			text: 'C',
			className: 'clear',
			action: ACTION_CLEAR
		},
		{
			text: '+/-',
			className: 'negation',
			action: ACTION_NEGATE
		},
		{
			text: '%',
			className: 'modulo',
			action: ACTION_UPDATE_OPERATOR,
			payload: {
				operator: '%',
			}
		},
		{
			text: '√',
			className: 'square',
			action: ACTION_UPDATE_OPERATOR,
			payload: {
				operator: 'yroot',
			}
		},


		{
			text: '7',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '7',
			}
		},
		{
			text: '8',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '8',
			}
		},
		{
			text: '9',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '9',
			}
		},
		{
			text: '/',
			className: 'division',
			action: ACTION_UPDATE_OPERATOR,
			payload: {
				operator: '/',
			}
		},


		{
			text: '4',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '4',
			}
		},
		{
			text: '5',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '5',
			}
		},
		{
			text: '6',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '6',
			}
		},
		{
			text: '',
			className: 'multiplication',
			icon: 'ion-ios-close-empty',
			action: ACTION_UPDATE_OPERATOR,
			payload: {
				operator: '*',
			}
		},


		{
			text: '1',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '1',
			}
		},
		{
			text: '2',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '2',
			}
		},
		{
			text: '3',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '3',
			}
		},
		{
			text: '',
			className: 'subtraction',
			icon: 'ion-ios-minus-empty',
			action: ACTION_UPDATE_OPERATOR,
			payload: {
				operator: '-',
			}
		},


		{
			text: '0',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '0',
			}
		},
		{
			className: 'paren',
			children: [
				{
					text: '(', className: 'open-paren',
					action: ACTION_ADD_PAREN,
					payload: {
						operator: '(',
					}
				},
				{
					text: ')', className: 'close-paren',
					action: ACTION_ADD_PAREN,
					payload: {
						operator: ')',
					}
				}
			]
		},
		{
			text: '.',
			action: ACTION_APPEND_OPERAND,
			payload: {
				value: '.',
			}
		},
		{
			text: '',
			className: 'addition',
			icon: 'ion-ios-plus-empty',
			action: ACTION_UPDATE_OPERATOR,
			payload: {
				operator: '+',
			}
		}
	];


	// Mode show total causes the total to be displayed in the current operand display
	const MODE_SHOW_TOTAL     = 1 << 1;
	// Mode insert operand causes the current operand to be overwritten. After the first character has been written, the mode should go to mode append operand
	const MODE_INSERT_OPERAND = 1 << 2;
	// Mode append operand causes any operand parts to be appended to the current operand
	const MODE_APPEND_OPERAND = 1 << 3;


	// The maximum number of digits the current operand may be
	const MAX_NUMBER_LENGTH = Number.MAX_SAFE_INTEGER.toString().length;


	const initialState = {

		activeButtons: [],

		buttons,

		expressions: ['5', '+', '7', '-', '45', '+', '3', '+', '177', '-'],

		currentOperand: '147',

		currentOperator: '-',

		mode: MODE_SHOW_TOTAL|MODE_INSERT_OPERAND,

		openParenStack: 0,

		error: null,

		total: 147,

	};

	const mutations = {

		CLEAR(state) {
			state.expressions = [];
			state.currentOperand = '0';
			state.currentOperator = '';
			state.openParenStack = 0;
			state.mode = MODE_SHOW_TOTAL|MODE_INSERT_OPERAND;
			state.error = null;
			state.total = 0;
		},

		BACKSPACE(state) {
			let operand = state.currentOperand.slice(0, -1);

			if (operand.length === 0) {
				operand = '0';
			}

			state.currentOperand = operand;
		},

		CLEAR_ENTRY(state) {
			state.currentOperand = '0';
		},

		NEGATE(state) {
			// Only add negative sign if not zero
			if (state.currentOperand !== 0) {
				state.currentOperand = (-state.currentOperand).toString();
			}
		},

		UPDATE_OPERATOR(state, { operator }) {
			const length = state.expressions.length;
			const last = state.expressions[length - 1] || '';
			const { mode, currentOperand } = state;

			if (mode & MODE_INSERT_OPERAND) {
				console.log('MODE_INSERT_OPERAND');

				if (length === 0) {
					state.expressions.push(currentOperand, operator);
				} else if (isOperator(last)) {
					// console.log('isoplast');                            // APPEND_OP LOG
					state.expressions.pop();
					state.expressions.push(operator);
				} else if (last === ')') {
					// console.log('nope');                                // APPEND_OP LOG
					state.expressions.push(operator);
				} else if (last === '(') {
					state.expressions.push(currentOperand, operator);
				} else {
					// console.log('else');                                // APPEND_OP LOG
				}
			} else if (mode & MODE_APPEND_OPERAND) {
				console.log('MODE_APPEND_OPERAND');

				if (length === 0) {
					console.log('length 0');                            // APPEND_OP LOG
					state.expressions.push(currentOperand, operator);
				} else if (isOperator(last)) {
					// console.log('isOperator(last)');                    // APPEND_OP LOG
					state.expressions.push(currentOperand, operator);
				} else if (last === ')') {
					// console.log('last === )');                          // APPEND_OP LOG
					state.expressions.push(operator);
				} else if (last === '(') {
					// console.log('last === (');                          // APPEND_OP LOG
					state.expressions.push(currentOperand, operator);
				} else {
					// console.log('else');
					// state.expressions.push(operator, currentOperand);
				}
			}

			state.currentOperator = operator;
			state.mode = MODE_INSERT_OPERAND|MODE_SHOW_TOTAL;

			console.log('UPDATE_OPERATOR:', state.expressions);
		},

		ADD_PAREN(state, { operator }) {
			const last = state.expressions[state.expressions.length - 1] || '';
			const { currentOperand, openParenStack } = state;

			// console.log('ADD_PAREN:', {last, operator});

			if (operator === ')' && openParenStack === 0) {
				// No need to add closing paren if there is no open paren
				return;
			} else if (operator === '(' && last === ')') {
				// FIXME: Look at real calculator for semantics
				return;
			}

			if (last === '(' && operator === ')') {
				// Handle immediate closed parens
				state.expressions.push(currentOperand, operator);
			} else if (isOperator(last) && operator === ')') {
				// Automatically append current operand when expressions
				// is "(5 *" so result is "(5 * 5)"
				state.expressions.push(currentOperand, operator);
			} else if ((isOperator(last) || length === 0) && operator === '(') {
				// Handle "5 *" where the result is "5 * (" and "(" is the beginning
				// of a new group expression
				state.expressions.push(operator);
			}

			if (operator === '(') {
				state.openParenStack++;
			} else if (operator === ')') {
				state.openParenStack--;
			}

			console.log('ADD_PAREN');
		},

		APPEND_OPERAND(state, { value, operator }) {
			const currentOperand = state.currentOperand;
			let newOperand = currentOperand;
			let newMode;

			// Don't append 0 to 0
			if (value === '0' && currentOperand[0] === '0') {
				return;
			} else if (value === '.' && currentOperand.includes('.')) {
				// Avoid appending multiple decimals
				return;
			}

			// Switch modes from showing the total to the current operand
			if (state.mode & MODE_SHOW_TOTAL) {
				newMode = MODE_INSERT_OPERAND;
			}

			if (state.mode & MODE_INSERT_OPERAND) {
				// console.log('INSERT');
				newOperand = value.toString();
				state.mode = MODE_APPEND_OPERAND;
			} else {
				// console.log('APPEND');
				newOperand += value.toString();
			}

			// TODO: Update font size, actually should do that in the vm
			state.currentOperand = newOperand.substring(0, MAX_NUMBER_LENGTH);
		},

		SHOW_TOTAL(state, { $commit, explicit }={}) {
			const last             = state.expressions[state.expressions.length - 1] || '';
			const expressions      = state.expressions.slice(0);
			const currentOperand   = state.currentOperand;
			const mode             = state.mode;
			const currentTotal     = state.total;
			const openParenStack   = state.openParenStack;
			const isFirstNumber    = typeof Number(expressions[0]) === 'number';
			const isSecondOperator = isOperator(expressions[1] || '');
			const length           = expressions.length;
			let times              = openParenStack;
			let total;

			if (expressions.length === 0) {
				return;
			}
			else if (explicit && isFirstNumber && isSecondOperator && length === 2) {
				// Handle case where expressions is 5 *

				// console.log('explicit && isFirstNumber && isSecondOperator');
				expressions.push(currentOperand);
			}
			else if (explicit && isOperator(last)) {
				// Handle case where expressions is ['5', '*', '4', '+'] and
				// the total is being explicitly being requested

				// console.log('explicit && isOperator(last)', isOperator(last), last);
				if (mode & MODE_INSERT_OPERAND) {
					expressions.push(currentTotal);
				} else if (mode & MODE_APPEND_OPERAND) {
					expressions.push(currentOperand);
				}
			}
			else if (isOperator(last)) {
				// Handle case where expressions is ['5', '*', '4', '+']

				// console.log('isOperator(last)');
				expressions.pop();
			}

			if (explicit) {
				// Automatically close parens when explicitly requesting
				// the total
				let times = openParenStack;

				while (times-- > 0) {
					expressions.push(')');
				}
			} else if ( ! explicit && openParenStack === 1) {
				// Auto close if there is only one missing paren
				expressions.push(')');
			}

			try {
				total = MathParser.eval(expressions.join(' '));

				if (explicit) {
					$commit('CLEAR');
				}

				state.total = total;
			} catch (err) {
				if (explicit) {
					$commit('CLEAR');
					state.error = err;
					console.log(err);
				}
			}

			console.log(
				'SHOW_TOTAL; Expressions: "%s"; Total: %s; Explicit: %s',
					expressions.join(' '),
					total,
					!! explicit);
		}

	};

	const actions = {

		clear({ commit }) {
			commit('CLEAR');
			console.log('');
		},

		backspace({ commit }) {
			commit('BACKSPACE');
			console.log('');
		},

		clearEntry({ commit }) {
			commit('CLEAR_ENTRY');
			console.log('');
		},

		negate({ commit }) {
			commit('NEGATE');
			console.log('');
		},

		updateOperator({ commit }, payload) {
			commit('UPDATE_OPERATOR', payload);
			commit('SHOW_TOTAL', {
				...payload,
				$commit: commit,
			});
			console.log('');
		},

		appendOperand({ commit }, payload) {
			commit('APPEND_OPERAND', payload);
			commit('SHOW_TOTAL', {
				...payload,
				$commit: commit,
			});
			console.log('');
		},

		showTotal({ commit }, payload) {
			// FIXME: Probably not supposed to pass commit, but idk
			//        how else to do it
			commit('SHOW_TOTAL', {
				...payload,
				$commit: commit,
			});
			console.log('');
		},

		addParen({ commit }, payload) {
			commit('ADD_PAREN', payload);
			commit('SHOW_TOTAL', {
				...payload,
				$commit: commit,
			});
			console.log('');
		}

	};

	const store = window.store = new Vuex.Store({

		state: initialState,

		actions,

		mutations,

	});


	Vue.component('calculatorbutton', {

		props: ['button'],

		template: templates.calculatorButton,

		computed: {

			className() {
				const button = this.button;
				let className = '';

				if (button.children) {
					className += ' has-children ';
				}

				if (button.className) {
					className += ` Calculator-button--${button.className} `;
				}

				return className;
			}

		},

		methods: {

			emitAction($event, button) {
				this.$store.dispatch(button.action, button.payload);
			}

		}

	});


	// [...document.querySelectorAll('.btest')].forEach(item => {
	// 	item.addEventListener('click', () => {
	// 		console.log('btest');
	// 	});
	// })

	const app = new Vue({

		el: $app,

		store,

		mounted() {
			setTimeout(() => this.appLoaded = true, 100)
		},

		data: {

			console,

			appLoaded: false,

		},

		computed: {

			...Vuex.mapState([
				'buttons',
				'expressions',
				'currentOperand',
				'currentOperator',
				'openParenStack',
				'total',
				'error',
				'mode'
			]),

			operand() {
				let operand;

				if (this.error) {
					return 'Error';
				}

				console.log('Flags:', getFlags(this.mode));

				if (this.mode & MODE_SHOW_TOTAL) {
					operand = this.total.toString();
					console.log('DISPLAY_TOTAL', this.total.toString());
				} else {
					operand = this.currentOperand;
					console.log('DISPLAY_CURRENT', this.currentOperand);
				}

				return operand;
			},

			expressionList() {
				return this.expressions.map((str, index, array) => {
					const s = str.trim();

					if (array[index -1] === '(') {
						return s;
					} else if (s === ')') {
						return s
					} else if (s[0] === '-' && isNumberPart(s[1])) {
						return ' ' + str;
					} else {
						return ' ' + s;
					}

					return str;
				})
				.join('');
			},

			font() {
				let length;

				if (this.mode & MODE_SHOW_TOTAL) {
					length = this.total.toString().length;
				} else {
					length = this.currentOperand.toString().length;
				}

				let size;
				let weight;

				if (length < 8) {
					size = '60px';
					weight = '200';
				} else if (length <= MAX_NUMBER_LENGTH) {
					size = '28px';
					weight = '300';
				} else if (length >= MAX_NUMBER_LENGTH) {
					size = '24px';
					weight = '300';
				}

				return { size, weight };

			},

		}

	});

	const Key = {
		Backspace:       8,
		Delete:         46,
		Enter:          13,
		Escape:         27,

		Multiply:      106,
		Add:           107,
		Subtract:      109,
		Decimal:       110,
		Divide:        111,

		Equals:        187,
		Dash:          189,
		ForwardSlash:  191,

		0:             48,
		1:             49,
		2:             50,
		3:             51,
		4:             52,
		5:             53,
		6:             54,
		7:             55,
		8:             56,
		9:             57,

		Numpad0:       96,
		Numpad1:       97,
		Numpad2:       98,
		Numpad3:       99,
		Numpad4:      100,
		Numpad5:      101,
		Numpad6:      102,
		Numpad7:      103,
		Numpad8:      104,
		Numpad9:      105,
	};

	const KeyTranslate = {
		48:  '0',
		49:  '1',
		50:  '2',
		51:  '3',
		52:  '4',
		53:  '5',
		54:  '6',
		55:  '7',
		56:  '8',
		57:  '9',

		96:  '0',
		97:  '1',
		98:  '2',
		99:  '3',
		100: '4',
		101: '5',
		102: '6',
		103: '7',
		104: '8',
		105: '9',

		106: '*',
		107: '+',
		109: '-',
		111: '/',

		189: '-',
		191: '/',
	};

	const OperatorKeys = [Key.Multiply, Key.Add, Key.Subtract, Key.Divide];

	window.addEventListener('keydown', function onWindowKeydown(e) {
		const { keyCode: key,
				ctrlKey,
				shiftKey } = e;

		// console.log(key, e.key, e.which);

		if (shiftKey && key === Key['9']) {
			store.dispatch(ACTION_ADD_PAREN, {
				operator: '('
			});
		}
		else if (shiftKey && key === Key['0']) {
			store.dispatch(ACTION_ADD_PAREN, {
				operator: ')'
			});
		}
		else if (shiftKey && key === Key['8']) {
			store.dispatch(ACTION_UPDATE_OPERATOR, {
				operator: '*'
			});
		}
		else if (shiftKey && key === Key.Equals) {
			store.dispatch(ACTION_UPDATE_OPERATOR, {
				operator: '+'
			});
		}
		else if (key === Key.Dash) {
			store.dispatch(ACTION_UPDATE_OPERATOR, {
				operator: '-'
			});
		}
		else if ((key >= 48 && key <= 57) || (key >= 96 && key <= 105)) {
			store.dispatch(ACTION_APPEND_OPERAND, {
				value: KeyTranslate[key]
			});
		}
		else if (key === Key.Decimal) {
			store.dispatch(ACTION_APPEND_OPERAND, {
				value: '.'
			});
		}
		else if ([Key.Multiply, Key.Add, Key.Subtract, Key.Divide].includes(key)) {
			store.dispatch(ACTION_UPDATE_OPERATOR, {
				operator: KeyTranslate[key]
			});
		}
		else if (key === Key.Backspace) {
			store.dispatch(ACTION_BACKSPACE);
			return e.preventDefault();
		}
		else if (key === Key.Delete) {
			store.dispatch(ACTION_CLEAR_ENTRY);
			return e.preventDefault();
		}
		else if (key === Key.Enter) {
			store.dispatch(ACTION_SHOW_TOTAL, {
				explicit: true
			});
			return e.preventDefault();
		}
		else if (key === Key.Escape) {
			store.dispatch(ACTION_CLEAR);
			return e.preventDefault();
		}
	});

	// Debug function for flags
	function getFlags(flags) {
		let arr = [];

		if (flags & MODE_SHOW_TOTAL) {
			arr.push('MODE_SHOW_TOTAL');
		}
		if (flags & MODE_INSERT_OPERAND) {
			arr.push('MODE_INSERT_OPERAND');
		}

		if (flags & MODE_APPEND_OPERAND) {
			arr.push('MODE_APPEND_OPERAND');
		}

		return arr.join('|');
	}
};


// TODO NEXT:
function getTotal(cb) {
	try {
		const total = MathParser.eval(this.expressions.join(''));
		return cb(null, total);
	} catch (err) {
		cb(err);
		console.log(err);
	}
}

function isNumberPart(str) {
	return (/^[0-9.]/).test(str);
}

setTimeout(main, 100);


// Have to mock commonjs because this was developed in node

const { MathParser, isOperator, operators } = (function (module) {
var exports = module.exports;

'use strict';

const Token = exports.Token = {
	NumericLiteral: 'NumericLiteral',
	Punctuator: 'Punctuator'
};

/**
 * Regex for numeric decimal literal constructed from ECMAScript spec
 */

const RE_NUMERIC_LITERAL = exports.RE_NUMERIC_LITERAL =
	/^(?:(?:0x[0-9a-fA-F]+|0X[0-9a-fA-F]+)|(?:0[oO][0-7]+)|(?:0[bB][01]+)|(?:(?:0|[1-9](?:[0-9]+)?)\.(?:[0-9]+)?|\.[0-9]+|(?:0|[1-9](?:[0-9]+)?))(?:[eE](?:[-+][0-9]+))?)/;

const operators =
	exports.operators = ['/', '*', '**', '-', '+', 'yroot', '%'];

const punctuation =
	exports.punctuation = ['(', ')', ...operators];

// All the operators, sorted by longest string length
const RE_PUNCTUATION = exports.RE_PUNCTUATION =
	new RegExp(
		'^(?:'
		+ punctuation.slice(0)
			.sort((a, b) => b.length - a.length)
			.map(str => escapeRegExp(str))
			.join('|')

		+ ')'
	);

const isOperator =
	exports.isOperator = (str) => operators.includes(str);

/**
 * Courtesy of
 * http://stackoverflow.com/questions/3446170/escape-string-for-use-in-javascript-regex
 */

function escapeRegExp(str) {
  return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
}

function isWhitespace(str) {
	return /^\s$/.test(str);
}

/**
 * A Lexer
 * @param {String} data
 * @param {Object} options
 */

const Lexer = exports.Lexer = class Lexer {

	constructor(data, options) {
		let source = data;

		if (source.charAt(0) === '\uFEFF') {
			source = source.slice(1);
		}

		source = source.replace(/\r\n|[\n\r]/g, '\n');

		this.source        = source;
		this.input         = source;
		this.position      = 0;
		this.stash         = [];
		this.column        = 0;
		this.line          = 1;
	}

	static all(data, options) {
		const lexer = new Lexer(data, options);
		const tokens = [];
		let token;

		while (token = lexer.nextToken()) {
			tokens.push(token);
		}

		return tokens;
	}

	lex() {
		const token =
			null
			|| this.getPunctuationToken()
			|| this.getNumericToken()

		if (token == null) {
			this.error(`Unexpected token at (${this.position})`);
			// this.error(`Unexpected token (${this.line}:${this.column})`);
		}

		return token;
	}

	forward(index) {
		this.position += index;
		this.input = this.input.substring(index, this.source.length);
	}

	getPunctuationToken() {
		const position = this.position;
		const match = this.input.match(RE_PUNCTUATION);

		if (match) {
			this.forward(match[0].length);

			return {
				type: Token.Punctuator,
				value: match[0],
				start: position,
				end: this.position
			};
		}

		return null;
	}

	getNumericToken() {
		const position = this.position;
		const match = this.input.match(RE_NUMERIC_LITERAL);

		if (match) {
			this.forward(match[0].length);

			return {
				type: Token.NumericLiteral,
				raw: match[0],
				value: Number(match[0]),
				start: position,
				end: this.position
			};
		}

		return null;
	}

	hasEnded() {
		return this.input.length === 0;
	}

	skipWhitespace() {
		let position = this.position;
		let times = 0;
		let char;

		while (position < this.source.length) {
			char = this.input[times];

			if (isWhitespace(char)) {
				position++;
				times++;

				if (char === '\n') {
					this.line++;
					this.column = 0;
				}
			} else {
				break;
			}
		}

		this.position = position;
		this.input = this.input.substring(times, this.source.length);
	}

	/**
	 * Returns the next token without consuming the token or null if no
	 * tokens can be found.
	 *
	 * @return {Object|null}
	 */

	peek() {
		return this.lookahead(1);
	}

	/**
	 * Returns the token at `index` or `null` if there are no more tokens.
	 *
	 * @param  {Number} index - The number of tokens to look ahead
	 * @return {Object|null}
	 */

	lookahead(index) {
		const { stash } = this;
		let times = index - stash.length;
		let token;

		if (index < 0) {
			this.error('Lookahead index can not be less than 0');
		}

		if (stash[index - 1] !== undefined) {
			return stash[index - 1];
		}

		while (times-- > 0) {
			this.skipWhitespace();

			if (this.hasEnded()) {
				break;
			}

			token = this.lex();

			if (token) {
				stash.push(token);
			}
		}

		return stash[index - 1] || null;
	}

	nextToken() {
		if (this.stash.length) {
			return this.stash.shift();
		} else if (this.hasEnded()) {
			return null;
		}

		this.skipWhitespace();

		if (this.hasEnded()) {
			return null;
		}

		return this.lex();
	}

	error(message) {
		const err = new Error(message);
		throw err;
	}

};

const Parser = exports.Parser = class Parser {

	constructor(data, options) {
		this.lexer = new Lexer(data, options);
	}

	peek() {
		return this.lexer.peek();
	}

	next() {
		return this.lexer.nextToken();
	}

	error(message) {
		const err = new Error(message);
		throw err;
	}

	parsePrimary() {
		let token = this.peek();
		let expression;

		if (token == null) {
			this.error('Unexpected end of input');
		}

		if (token.value === '(') {
			token = this.next();
			expression = this.parseExpression();
			token = this.next();

			if (token == null) {
				this.error(`Unexpected end of input`);
			} else if (token.value !== ')') {
				this.error(`Unexpected token ${token.value}`);
			}

			return expression;
		} else if (token.type === Token.NumericLiteral) {
			token = this.next();
			return new Literal(token.raw, token.value);
		}

		this.error(`Unexpected token "${token.value}"`);
	}

	parseUnary() {
		let token = this.peek();

		if (token && (token.value === '-' || token.value === '+')) {
			token = this.next();

			return new UnaryExpression(token.value, this.parseUnary());
		}

		return this.parsePrimary();
	}

	// I'm not sure what these pow and nth square root operators are classified as
	parsePowAndSquare() {
		let expression = this.parseUnary();
		let token = this.peek();

		if (token == null) {
			return expression;
		}

		while (token && (token.value === '**' || token.value == 'yroot')) {
			token = this.next();

			const operator = token.value;
			const left = expression;
			const right = this.parseUnary();

			expression = new BinaryExpression(operator, left, right);

			token = this.peek();
		}

		return expression;
	}

	parseMultiplicative() {
		let expression = this.parsePowAndSquare();
		let token = this.peek();

		if (token == null) {
			return expression;
		}

		while (token && (token.value === '*' || token.value == '/' || token.value === '%')) {
			token = this.next();

			const operator = token.value;
			const left = expression;
			const right = this.parsePowAndSquare();

			expression = new BinaryExpression(operator, left, right);
			token = this.peek();
		}

		return expression;
	}

	parseAdditive() {
		let expression = this.parseMultiplicative();
		let token = this.peek();

		while (token && (token.value === '+' || token.value === '-')) {
			token = this.next();

			const operator = token.value;
			const left = expression;
			const right = this.parseMultiplicative();

			expression = new BinaryExpression(operator, left, right, token.start, token.end);
			token = this.peek();
		}

		return expression;
	}

	parseExpression() {
		return this.parseAdditive();
	}

	parse() {
		return this.parseExpression();
	}

}

class UnaryExpression {

	constructor(operator, expression) {
		this.type = 'UnaryExpression';
		this.operator = operator;
		this.expression = expression;
	}

}

class BinaryExpression {

	constructor(op, left, right, start, end) {
		this.type = 'BinaryExpression';
		this.operator = op;
		this.left = left;
		this.right = right;
		this.start = start;
		this.end = end;
	}

}

class Literal {

	constructor(raw, value) {
		this.type = 'Literal';
		this.raw = raw;
		this.value = value;
	}

}

const operations = {
	'+': (a, b) => a + b,
	'-': (a, b) => a - b,
	'*': (a, b) => a * b,
	'/': (a, b) => a / b,
	'%': (a, b) => a % b,
	'**': (a, b) => Math.pow(a, b),
	// NOTE: Apparently this is a naive implementation of nth root
	// http://stackoverflow.com/questions/7308627/javascript-calculate-the-nth-root-of-a-number
	'yroot': (a, b) => Math.pow(a, 1 / b),
};

/**
 * Evaluates the AST produced from the parser and returns its result
 * @return {Number}
 */

const evaluateAST = exports.evaluateAST = (node) => {
	let a;

	switch (node.type) {
		case 'Expression':
			return evaluateAST(node.expression);
		case 'Literal':
			return parseFloat(node.value);
		case 'UnaryExpression':
			a = evaluateAST(node.expression);

			switch (node.operator) {
				case '+':
					return +a;
				case '-':
					return -a;
				default:
					throw new Error(`Parsing error: Unrecognized unary operator "${node.operator}"`);
			}
		case 'BinaryExpression':
			const { left, right, operator } = node;
			const operation = operations[operator];

			if (operation === undefined) {
				throw new Error('Unsupported operand');
			}

			return operation(evaluateAST(left), evaluateAST(right));
		default:
			throw new Error(`Parsing error: Unrecognized node type "${node.type}"`);
	}
};

/**
 * Evaluates the expression passed and returns its result.
 *
 * @param {String} expression - The expression to evaluate
 * @return {Number}
 */

const MathParser = exports.MathParser = {

	eval(expression) {
		const ast = new Parser(expression).parse();

		return evaluateAST(ast);
	}

}


if (typeof window === 'object' && window) {
	window.MathParser = MathParser;

	window.e = function () {
		return MathParser.eval(...arguments);
	};

	window.parse = function () {
		return Parser.parse(...arguments);
	};

	window.lex = function () {
		return Lexer.all(...arguments);
	};
}

return module.exports;
}({ exports: {} }));