var step_delay = 0;
var port = 35209;
var verbose = false;
var printtape = false;


// TODO: Do better than this?
var trans_done = 0;
var tape_done = 0;


var head_loc = 0;
var state = 0;
var tape = ["_"];
var transitions = {};

var steps = 0;

var pretty_tape = "";

var fs = require('fs');
var readline = require('readline');
var express = require('express');
var web = express();


var transitionReader = readline.createInterface({
    input: fs.createReadStream('transitions')
});
var tapeReader = readline.createInterface({
    input: fs.createReadStream('tape')
});

transitionReader.on('line', function(line) {
    if (verbose) console.log(line);
    var file_transitions = line.split(/[\s,]/);
    
    if (!transitions[file_transitions[0]]) transitions[file_transitions[0]] = {};

    transitions[file_transitions[0]][file_transitions[1]] = {
	to:file_transitions[2],
	write:file_transitions[3],
	move:file_transitions[4]
    };
});


transitionReader.on('close', function() {
    console.log("Done reading TRANSITIONS!");
    trans_done = 1;
});


tapeReader.on('line', function(line) {
    var symbols = line;
    for (var i = 0; i < symbols.length; i++) {
	if (symbols[i] == " ") {
	    tape[i+1] = "_";
	} else {
	    tape[i+1] = symbols[i];
	}
    }
});

tapeReader.on('close', function() {
    console.log("Done reading TAPE!");
    tape_done = 1;
});



var step = function() {
    steps++;
    
    if (verbose) console.log("START step");

    if (tape[head_loc] == undefined) {
	tape[head_loc] = "_";
    }

    if (verbose) {
	pretty_tape = "";
	for (i = 0; i < tape.length; i++) {
	    if (i == head_loc) pretty_tape = pretty_tape + "[";
	    pretty_tape = pretty_tape + tape[i];
	    if (i == head_loc) pretty_tape = pretty_tape + "]";
	}
    }
    if (verbose) console.log(pretty_tape);

    var cur_symbol = tape[head_loc];

    if (verbose) console.log("Symbol: %s | State: %s",cur_symbol,state);

    // Get the transition based on the current state and symbol
    var transition = transitions[state][cur_symbol];

    // Write to tape
    tape[head_loc] = transition.write;

    // Change state
    state = transition.to;

    // Move head
    if (transition.move == 'R') {
	head_loc++;
    } else if (transition.move == 'L') {
	head_loc--;
    }
    
    if (verbose) console.log("State: %s | Head: %s",state,head_loc)

    // Throw error if head was moved over the left edge of the tape
    if (head_loc == -1) {
	throw "head_loc error";
    }

    if (printtape) console.log("Tape %s",tape);
    

    if (verbose) console.log("END step!");
    setTimeout(step, step_delay);
}


var prestep = function() {
    // Check if the transitions and tape have been initialised
    if (trans_done == 1 && tape_done == 1) {
	if (verbose) console.log(transitions);
	if (verbose) console.log(tape);
	console.log("Ready! Stepping!");
	step();
    } else {
	console.log("Not ready! Waiting 100 ms...");
	setTimeout(prestep, 100);
    }
}

prestep();


// Set up web server
web.get('', function(req, res) {
    var webtape = "";
    for (i = 0; i < tape.length; i++) {
	if (i == head_loc) webtape = webtape + "[";
	webtape = webtape + tape[i];
	if (i == head_loc) webtape = webtape + "]";
    }
    res.send(webtape + "<br><br>" + "Steps: " + steps);
});

web.listen(port, function () {
    console.log("Server listening on port %s",port);
});