// Reads wires into an array then calls fn().
function readFile(file, fn) {
	require('readline').createInterface({
		input: require('fs').createReadStream(file)
	})
	.on('line', function (line) {
		var pieces = line.split(' -> ');
		wires[pieces[1]] = pieces[0];
	})
	.on('close', fn);
}

var wires = {}, calculated = {}, mask = 65535;

var ops = {
	AND: function(a, b) { return a & b; },
	OR: function (a, b) { return a | b; },
	XOR: function (a, b) { return a ^ b; },
	NOT: function (a) { return ~ a; },
	LSHIFT: function (a, b) { return a << b; },
	RSHIFT: function (a, b) { return a >> b; }
};

// Recursively calculate the signal to this wire.
function calculate(wire) {
	if (!isNaN(wire))   return parseInt(wire);
	if (calculated[wire]) return calculated[wire];

	var input = wires[wire].split(' '), length = input.length; // Note: inputs must only be strings.
	if (length === 1) calculated[wire] = calculate(input[0]);
	else if (length === 2) calculated[wire] = ops.AND(ops[input[0]](calculate(input[1])), mask);
	else if (length === 3) calculated[wire] = ops.AND(ops[input[1]](calculate(input[0]), calculate(input[2])), mask);

	return calculated[wire];
}

// Accept wire and file as arguments. Can also use "all" instead of a wire.
var wire = process.argv[2] ? process.argv[2] : 'a';
var file = process.argv[3] ? process.argv[3] : 'day7_input';
readFile(file, function() {
	if (wire === 'all') {
		Object.keys(wires).map(calculate);
		console.log(calculated);
	}
	else {
		calculate(wire);
		console.log(calculated[wire])
	}
});