server.js

var express = require('express');
var app = express();
var fs = require('fs');
var lepath = require('path');

app.use('/elmer', express.static(__dirname + '/elmer'));
app.use('/images', express.static(__dirname + '/images'));

app.use(express.urlencoded({ extended: true }));
app.use(express.json());

if (typeof String.prototype.reverse !== 'function') {
  String.prototype.reverse = function () {
    return this.split("").reverse().join("");
  };
}

if (typeof String.prototype.startsWith !== 'function') {
  String.prototype.startsWith = function (str) {
    return this.lastIndexOf(str, 0) === 0
  };
}

if (typeof String.prototype.endsWith !== 'function') {
  String.prototype.endsWith = function (suffix) {
    return this.indexOf(suffix, this.length - suffix.length) !== -1;
  };
}

var adventures = {};
var masterWizardName = "Edsger";

function book_name(index) {
  if (index === 1) {
    return "Plain JSON REST APIs for fun and profit";
  }
  if (index === 2) {
    return "Level 2 REST FTW";
  }
  if (index === 3) {
    return "No REST till Hypermedia!";
  }
}

String.prototype.endsWith = function(suffix) {
    return this.indexOf(suffix, this.length - suffix.length) !== -1;
};

function get_reps() {
  var files = fs.readdirSync("reps");
  var reps = [];
  for (var i = 0; i < files.length; i++) {
    var f = files[i];
    var suffixIndex = f.indexOf(".json");
    if (f.endsWith(".json")) {
      var resource = f.substring(0, f.length - ".json".length);
      reps.push(resource);
    }
  }
  return reps;
}

function has_rep(rep) {
  var reps = get_reps();
  for (var i = 0; i < reps.length; i++) {
    if (reps[i] === rep) {
      return true;
    }
  }
  return false;
}

function init_state(adv_id, old_state) {

  var bridge = false;
  var skeleton = false;
  if (old_state) {
    bridge = old_state.bridge;
    skeleton = old_state.skeleton;
  }

  var mirrors = [1, 2, 3, 4, 5, 6, 7];
  var unbreakable = Math.floor((Math.random()*mirrors.length)+1);
  var state = {
    "id": adv_id,
    "timestamp": new Date().getTime(),
    "mirrors": mirrors,
    "broken_mirrors": [],
    "unbreakable": unbreakable,
    "room": false,
    "closed": true,
    "bridge": bridge,
    "skeleton": skeleton,
    "old_state": old_state
  };

  return state;
}

var permanent_aid = 1337;

adventures[permanent_aid] = init_state(permanent_aid);

var local_port = 1337;

var base_url = 'http://localhost:' + local_port;

var port = process.env.PORT || local_port;

if (process.env.PORT) {
  base_url = 'https://hyperwizard.azurewebsites.net';
}

var game_url = base_url + '/hywit/';

function hylink(relative) {
  return game_url + relative;
}

function advlink(adv_id, relative) {
  return hylink(adv_id + '/' + relative);
}

function imglink(imgfile) {
  return base_url + '/images/' + imgfile;
}

function s4() {
  return Math.floor((1 + Math.random()) * 0x10000)
             .toString(16)
             .substring(1);
}

function setFsmImage(dir, imageName) {
  //console.log('Set FSM image ' + imageName);
  var pngFile = imageName + ".png";
  var basePath = lepath.join(__dirname, '../hub/fsmwatcher');
  var srcPath = lepath.join(basePath, 'graphs', dir, pngFile);
  var dstPath = lepath.join(basePath, 'fsmimages', pngFile);
  fs.stat(srcPath, function (err, stat) {
    if (err == null) {
      fs.copyFileSync(srcPath, dstPath);
    } else if(err.code == 'ENOENT') {
      console.log("FSM image doesn't exist. " + srcPath);
    } else {
      console.log('Some other error: ', err.code);
    }
  });
}

function acceptsHtml(req) {
  return req.headers.accept.indexOf("text/html") >= 0;
}

function acceptsJson(req) {
  const acceptsAll = req.headers.accept.startsWith("*/*");
  return acceptsAll || req.headers.accept.indexOf("application/json") >= 0;
}

function acceptsSiren(req) {
  const acceptsAll = req.headers.accept.startsWith("*/*");
  return acceptsAll || req.headers.accept.indexOf("application/vnd.siren+json") >= 0;
}

function toActionForm(act) {
  var s = "";
  var field;
  var httpMethod = "POST";
  if (act.method === "GET") {
    httpMethod = "GET";
  }

  s += "<p>" + act.title + '</p>';
  s += '<form action="' + act.href + '" method="' + httpMethod + '">';

  if ('undefined' === typeof act.method) {
    s += '<select name="httpmethod">';
    s += '<option value="GET">GET</option>';
    s += '<option value="POST">POST</option>';
    s += '<option value="PUT">PUT</option>';
    s += '<option value="DELETE">DELETE</option>';
    s += '<option value="PATCH">PATCH</option>';
    s += '</select>';
  }

  if ('undefined' !== typeof act.fields) {
    for (var i = 0, len = act.fields.length; i < len; i++) {
      field = act.fields[i];
      s += field.name + '<br />';
      s += '<input type="' + field.type + '" name="' + field.name + '" />';
      s += '<br />';
    }
  }

  s += '<br />';
  s += '<input type="submit" value="Submit" />';

  s += '</form>';
  return s;
}

function toHtml(srn) {
  var s = "";
  var props = srn.properties;
  var links = srn.links;
  var alink;
  var actions = srn.actions;
  var act;
  var title = "Hypermedia in the Wizard's Tower";
  if ('undefined' !== typeof srn.title) {
    title += ": " + srn.title;
  }

  s += "<!DOCTYPE html>";
  s += "<html>";
  s += "<head>";
  s += "<title>" + title + "</title>";
  s += '<meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1">';
  s += "</head>";

  s += "<body>";

  var imageLinks = [];
  if ('undefined' !== typeof links) {
    for (var i = 0, len = links.length; i < len; i++) {
      alink = links[i];
      if ('undefined' !== typeof alink.type) {
        if (alink.rel.indexOf("view") >= 0) {
          imageLinks.push(alink);
        }
      }
    }
  }

  var imgCount = imageLinks.length;
  if (imgCount > 0) {
    s += '<div class="images">';
    for (var imgIndex = 0; imgIndex < imgCount; imgIndex++) {
      var animage = imageLinks[imgIndex];
      s += '<img src="' + animage.href + '" />';
    }
    s += '</div>';
  }


  if ('undefined' !== typeof props) {
    s += "<div>";
    s += '<p class="name">' + props.name + '</p>';
    s += '<p class="description">' + props.description + '</p>';
    var keys = Object.keys(props);
    for (var k = 0; k < keys.length; k++) {
      var propname = keys[k];
      if (propname !== 'name' && propname !== 'description') {
        s += '<p class="' + propname + '">' + propname + ": " + props[propname] + '</p>';
      }
    }
    s += "</div>";
  }
  else {
    s += "<div>";
    var keys = Object.keys(srn);
    for (var k = 0; k < keys.length; k++) {
      var propname = keys[k];
      s += '<p class="' + propname + '">' + srn[propname] + '</p>';
    }
    s += "</div>";
  }

  if ('undefined' !== typeof links) {
    s += '<div class="links">';
    s += '<p>Places to go:</p>'
    s += '<ul>';

    for (var i = 0, len = links.length; i < len; i++) {
      alink = links[i];
      var linkText = alink.title || alink.rel;
      s += '<li>' + '<a href="' + alink.href + '">' + linkText + '</a>' + '</li>';
    }

    s += '</ul>';
    s += '</div>';
  }

  if ('undefined' !== typeof actions) {
    s += '<div class="actions">';
    s += '<p>Things to do:</p>'
    s += '<ul>';

    for (var i = 0, len = actions.length; i < len; i++) {
      act = actions[i];
      s += '<li>' + toActionForm(act) + '</li>';
    }

    s += '</ul>';
    s += '</div>';
  }

  s += "</body>";
  s += "</html>";

  return s;
}

function toResponse(req, res, siren, statusCode) {
  var sc = statusCode || 200;
  var ct = "application/vnd.siren+json";
  var transform = JSON.stringify;

  if (acceptsHtml(req)) {
    ct = "text/html";
    transform = toHtml;
  } 

  if (statusCode === 401) {
    res.set('WWW-Authenticate', 'Basic realm="tower"');
  }

  res.header('Access-Control-Allow-Origin', '*');

  if (acceptsSiren(req) || acceptsJson(req)) {
    res.contentType(ct);
    res.status(sc).send(transform(siren));
    return;
  }

  res.contentType("text/plain");
  res.status(406).send("application/vnd.siren+json\napplication/json\ntext/html");
}

function toJsonResponse(req, res, siren, statusCode) {
  var sc = statusCode || 200;
  var ct = "application/json";
  var transform = JSON.stringify;

  if (acceptsHtml(req)) {
    ct = "text/html";
    transform = toHtml;
  }

  res.contentType(ct);
  res.status(sc).send(transform(siren));
}

app.get('/', function(req, res) {
  res.contentType("text/plain");
  res.send("Visit http://github.com/einarwh/hyperwizard");
});

app.get('/hywit/void', function(req, res) {
  var voidUrl = hylink('void');
  if (req.headers.accept === "text/plain") {
    var text = "The Magical Void\n\nYou're in The Magical Void, a place beyond space and time. This is where adventures begin.\n\nTo start a new adventure, post name, class and race to " + voidUrl;
    res.contentType(req.headers.accept);
    res.send(text);
    return;
  }
  else if (req.headers.accept === "application/json") {
    var plainJson = {
      "title": "The Magical Void",
      "description": "You're in The Magical Void, a place beyond space and time. This is where adventures begin.",
      "link":
      {
        "title": "Start a new adventure",
        "url": voidUrl
      }
    };
    res.contentType(req.headers.accept);
    res.send(JSON.stringify(plainJson));
    return;
  }
  var siren = {
    "title": "The Magical Void",
    "class": [ "location" ],
    "properties": {
      "name": "The Magical Void",
      "description": "You\'re in The Magical Void, a place beyond space and time. This is where adventures begin.",
    },
    "actions": [
      {
        "name": "start-adventure",
        "method": "POST",
        "title": "Start adventure",
        "href": hylink('void'),
        "fields": [
          { "name": "name", "type": "text" },
          { "name": "class", "type": "text" },
          { "name": "race", "type": "text" }
        ]
      }
    ],
    "links": [
      { "rel": [ "self" ], "href": hylink('void') },
      { "rel": [ "view" ], "href": imglink('magical-void.png'), "type": "image/png" }
    ]
  };

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/hall/teapot', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  res.status(418).location(alink('hall')).send("What did you expect?");
});

// Not in use?
app.post('/hywit/:adv_id/hall/teapot', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  res.status(418).location(alink('hall')).send("What did you expect?");
});

app.get('/hywit/:adv_id/divide', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var self_link = alink('divide');
  var act = {
    "name": "pull-lever",
    "method": "POST",
    "title": "Pull the lever.",
    "href": self_link
  }
  var siren = {
    "title": "The Great Divide",
    "class": [ "location" ],
    "properties": {
      "name": "The Great Divide",
      "description": "You're standing on the edge of a great divide. You can see a rusty lever."
    },
    "actions": [ act ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "move", "south" ], "title": "Go south to the hill.", "href": alink("hill") }
    ]
  };

  if (adv_state.bridge) {
    siren.properties.description = siren.properties.description + " There is a bridge crossing the divide.";
    if (adv_state.skeleton) {
      siren.properties.description = siren.properties.description + " You see a skeleton on the bridge.";
    } else {
      siren.links.push({ "rel": [ "move" ], "title": "Cross the bridge.", "href": alink('bridge') });
    }

    setFsmImage('divide', 'divide-1-crossable');
  }
  else {
    siren.properties.description = siren.properties.description + " There seems to be a strange bridge hovering in the air, parallel to the divide.";
    if (adv_state.skeleton) {
      siren.properties.description = siren.properties.description + " You see a skeleton on the bridge.";
    }
  }

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.post('/hywit/:adv_id/divide', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  adv_state.bridge = !adv_state.bridge;
  if (adv_state.old_state) {
    adv_state.old_state.bridge = !adv_state.old_state.bridge;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var self_link = alink('divide');
  var act = {
    "name": "pull-lever",
    "method": "POST",
    "title": "Pull the lever.",
    "href": self_link
  }
  var siren = {
    "title": "The Great Divide",
    "class": [ "location" ],
    "properties": {
      "name": "The Great Divide",
      "description": "You're standing on the edge of a great divide. You can see a rusty lever."
    },
    "actions": [ act ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "move", "south" ], "title": "Go south to the hill.", "href": alink("hill") }
    ]
  };

  if (adv_state.bridge) {
    siren.properties.description = siren.properties.description + " There is a bridge crossing the divide.";
    if (adv_state.skeleton) {
      siren.properties.description = siren.properties.description + " You see a skeleton on the bridge.";
    } else {
      siren.links.push({ "rel": [ "move" ], "title": "Cross the bridge.", "href": alink('bridge') });
    }
  }
  else {
    siren.properties.description = siren.properties.description + " There seems to be a strange bridge hovering in the air, parallel to the divide.";
    if (adv_state.skeleton) {
      siren.properties.description = siren.properties.description + " You see a skeleton on the bridge.";
    }
  }

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  var fsmImageName = "divide-0-inaccessible";
  if (adv_state.bridge) {
    fsmImageName = "divide-1-crossable";
  }

  setFsmImage('divide', fsmImageName);

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/lake', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var self_link = alink('lake');
  var siren = {
    "title": "The Lake",
    "class": [ "location" ],
    "properties": {
      "name": "The Lake",
      "description": ""
    },
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "move", "north" ], "title": "Follow the brook north.", "href": alink("brook") }
    ]
  };

  if (undefined === adv_state.boat) {
    siren.properties.description = "You're standing on the shore of a lake. There's small island in the middle, where you can see a rowing boat tied to a pole. Unfortunately, the current is too strong for you to venture swimming over. Every now and then, the head of an otter emerges from the water.";

    if (undefined === adv_state.otter) {
      var otter = {
        name: "send-otter",
        title: "Send the otter to fetch the boat.",
        method: "POST",
        href: self_link
      }

      siren.actions = [ otter ];
    }
    else {
      siren.properties.description = "You're standing on the shore of a lake. There's small island in the middle. Unfortunately, the current is too strong for you to venture swimming over. An otter with superior swimming skills is swimming in the water.";

      siren.links.push({
        "rel": [ "look" ],
        "title": "Look at the otter.",
        "href": alink('otter')
      });

      setFsmImage('lake', 'lake-1-waiting');
    }
  }
  else {
    siren.properties.description = "You're standing on the shore of a lake. There's small island in the middle. There is a boat here. Every now and then, the head of an otter emerges from the water.";

    var row = {
      "rel": [ "move" ],
      "title": "Row to the island.",
      "href": alink('island')
    };

    siren.links.push(row);

    setFsmImage('lake', 'lake-2-boat');
  }

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.post('/hywit/:adv_id/lake', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  adv_state.otter = Date.now() / 1000;

  res.status(202).location(alink('otter')).send();
});

app.get('/hywit/:adv_id/otter', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  if ('undefined' === typeof adv_state.otter) {
    res.status(403).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var current = Date.now() / 1000;
  var elapsed = current - adv_state.otter;
  var totalTime = 6; // 120
  var halfTime = 3; // 60
  var otterReturned = elapsed > totalTime;
  if (otterReturned) {
    adv_state.boat = current;
    res.status(303).location(alink('lake')).send();

    setFsmImage('otter', 'otter-3-back');

    return;
  }

  var otterReturning = elapsed > halfTime;

  var self_link = alink('otter');
  var siren = {    
    "title": "The Swimming Otter",
    "class": [ "entity" ],
    "properties": {
      "name": "The Swimming Otter",
      "description": "The otter is on its way to fetch the rowing boat. It has spent " + Math.floor(elapsed) + " seconds so far."
    },
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "previous" ], "href": alink('lake') },
      { "rel": [ "view" ], "href": imglink("otter.png"), type: "image/png" }
    ]
  };

  if (otterReturning) {
    siren.properties.description += " Currently, it is on the way back, towing the boat.";
    setFsmImage('otter', 'otter-2-returning');
  }
  else {
    siren.properties.description += " Currently, it is swimming towards the island.";
    setFsmImage('otter', 'otter-1-fetching');
  }

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/hall', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  var act = {
    "name": "make-coffee",
    "title": "Use teapot to brew some coffee.",
    "href": alink('hall/teapot')
  }

  var self_link = alink('hall');
  var siren = {
    "title": "The Great Hall",
    "class": [ "location" ],
    "properties": {
      "name": "The Great Hall",
      "description": "You find yourself in a great hall. There's a table here. You see some cutlery of no interest to you, as well as a beautiful silver tea pot. Could it be magical? A door leads to the east from here."
    },
    "actions": [ act ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "move", "east" ], "href": alink("mirrors"), "title": "Go through the door to the east." },
      { "rel": [ "move", "exit" ], "href": alink("entrance"), "title": "Exit the tower." }
    ]
  };

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/grue', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];
  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }
  var alink = function (relative) {
    return advlink(adv_id, relative);
  };
  if (undefined === adv_state.grue) {
    var act = {
      "name": "kill-grue",
      "title": "Light a handy torch lying nearby.",
      "href": alink('gruesome')
    }
    var siren = {
      "title": "A terrifying grue.",
      "class": [ "location" ],
      "properties": {
        "name": "A terrifying grue.",
        "description": "Uh-oh. A terrifying grue has appeared in front of you. This could be fatal, unless you know your HTTP methods."
      },
      "actions": [ act ],
      "links": [
        { "rel": [ "view" ], "href": imglink("grue.png"), type: "image/png" }
      ]
    };

    if (adv_state.old_state) {
      siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
    }

    toResponse(req, res, siren);
  } else {
    setFsmImage('grue', 'grue-2-gone');
    res.status(410).send("The grue has vanished permanently.");
  }
});

function killGrue(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];
  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }
  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  setFsmImage('grue', 'grue-2-gone');

  adv_state.grue = "dead";
  res.status(204).location(alink('brook')).send("The grue is gone.");
}

function eatenByGrue(res) {
  setFsmImage('grue', 'grue-1-deadly');
  res.status(405).send("You've been eaten by a grue.");
}

app.post('/hywit/:adv_id/gruesome', function(req, res) {
  var verb = req.body.httpmethod;

  if (verb === 'DELETE') {
    killGrue(req, res);
    return;
  }

  eatenByGrue(res);
});

app.get('/hywit/:adv_id/gruesome', function(req, res) {
  eatenByGrue(res);
});

app.patch('/hywit/:adv_id/gruesome', function(req, res) {
  eatenByGrue(res);
});

app.put('/hywit/:adv_id/gruesome', function(req, res) {
  eatenByGrue(res);
});

app.delete('/hywit/:adv_id/gruesome', function(req, res) {
  killGrue(req, res);
});

app.get('/hywit/:adv_id/study', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  var self_link = alink('study');

  var book_action = function(book_number) {
    return {
      "name": "take-book-" + book_number,
      "title": "Take '" + book_name(book_number) + "'",
      "method": "POST",
      "href": alink("study/books/" + book_number)
    };
  };

  var siren = { "class": [ "location" ],
    "title": "The Wizard's Study",
    "properties": {
      "name": "The Wizard's Study",
      "description": "You have entered the Wizard's Study. Luckily, the Wizard is not in, or he would surely have deleted you. This means that you have conquered the Wizard's Tower. Congratulations! You may pick a prize, by choosing a book from the Wizard's shelf. Choose wisely."
    },
    "actions": [
      book_action(1),
      book_action(2),
      book_action(3)
    ],
    "links": [
      { "rel": [ "self" ], "href": self_link }
    ]
  };

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  if (adv_state.book_id !== undefined) {
    setFsmImage('book', 'book-0-choice');
  }

  toResponse(req, res, siren);
});

app.post('/hywit/:adv_id/study/books/:book_id', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  var book_id = parseInt(req.params.book_id, 10);
  adv_state.book_id = book_id;

  var siren;
  if (book_id === 3) {
    siren = {
      "class": [ "location" ],
      "title": book_name(book_id),
      "properties": {
        "name": book_name(book_id),
        "description": "Well done. You may return to The Magical Void with your prize."
      },
      "links": [
        { "rel": [ "return" ], "href": hylink('void'), "title": "Return to the void." }
      ]
    };

    if (adv_state.old_state) {
      siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
    }

    setFsmImage('book', 'book-2-free');

    toResponse(req, res, siren);
  }
  else if (book_id === 1 || book_id === 2) {
    var plainJson = {
      "book": book_name(book_id),
      "text": "Well, that's unfortunate. You see, without hyperlinks, you're just stuck here forever."
    };

    setFsmImage('book', 'book-1-stuck');

    toJsonResponse(req, res, plainJson);
  }
  else {
    res.status(400).send();
    return;
  }
});

app.get('/hywit/:adv_id/mirrors/:mirror', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];
  var mirror = parseInt(req.params.mirror, 10);

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  if (adv_state.mirrors.indexOf(mirror) < 0) {
    if (adv_state.broken_mirrors.indexOf(mirror) < 0) {
      res.status(404).send();
    }
    else {
      res.status(410).send();
    }
    return;
  }

  var self_link = alink('mirrors/' + mirror);

  var siren = { "class": [ "location" ],
    "title": "Mirror #" + mirror,
    "properties": {
      "name": "Mirror #" + mirror,
      "description": "You see a reflection of yourself."
    },
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "previous" ], "href": alink('mirrors') },
      { "rel": [ "view" ], "href": imglink('mirror.png'), "type": "image/png" }
    ]
  };

  if (mirror === adv_state.unbreakable) {
    siren.properties.description = "You see a reflection of yourself, upside-down.";
    if (adv_state.mirrors.length === 1) {
      var enter_action = {
        "name": "enter-mirror",
        "title": "Enter the mirror!",
        "method": "POST",
        "href": alink("mirrors/" + adv_state.unbreakable)
      };
      siren.actions = [ enter_action ];
    }
  }

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/mirrors', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  var self_link = alink('mirrors');

  var smash_mirror = function (mirr) {
    return {
      "name": "smash-mirror-" + mirr,
      "title": "Smash the mirror!",
      "method": "DELETE",
      "href": alink("mirrors/" + mirr)
    };
  };

  var look_mirror = function (mirr) {
    return {
      "rel": [ "look" ],
      "title": "Look into the mirror.",
      "href": alink("mirrors/" + mirr)
    };
  };

  var mirror_actions = [];
  var links = [];

  for (var i=0, len=adv_state.mirrors.length; i<len; i++)
  {
    var mrr = adv_state.mirrors[i];
    if (mrr !== adv_state.unbreakable) {
      mirror_actions.push(smash_mirror(mrr));
    }
    links.push(look_mirror(mrr));
  }

  var desc = "You're in a room of mirrors. You see infinite variations of yourself disappearing into nowhere. Somewhere in the distance you even see your own image upside-down. It is rather confusing. There are doors to the north and to the west.";
  if (mirror_actions.length === 0) {
    desc = "You're in a room with a single mirror. There are doors to the north and to the west.";
    //var enter_action = {
    //  "name": "enter-mirror-" + adv_state.unbreakable,
    //  "title": "Enter the mirror!",
    //  "method": "POST",
    //  "href": alink("mirrors/" + adv_state.unbreakable)
    //};
    //mirror_actions.push(enter_action);
  }

  links.unshift(
    { "rel": [ "self" ], "href": self_link },
    { "rel": [ "move", "north" ], "title": "Go north.", "href": alink("room") },
    { "rel": [ "move", "west" ], "title": "Go east.", "href": alink("hall") },
    { "rel": [ "view" ], "href": imglink("mirrors.png"), "type": "image/png" }
  );

  var siren = { "class": [ "location" ],
    "title": "The Mirror Room",
    "properties": {
      "name": "The Mirror Room",
      "description": desc
    },
    "links": links
  };

  if (mirror_actions.length > 0) {
    siren.actions = mirror_actions;
  }

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.post('/hywit/:adv_id/mirrors/:mirror', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  var mirror = parseInt(req.params.mirror, 10);

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  if (mirror !== adv_state.unbreakable) {
    if (adv_state.mirrors.length > 1) {
      breakMirror(req, res);
      return;
    }
    res.status(405).send();
    return;
  }

  adv_state.room = !adv_state.room;

  setFsmImage('mirror', 'mirror-1-open');

  res.status(302).location(alink('mirrors')).send();
});


function breakMirror(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];
  var mirror = parseInt(req.params.mirror, 10);

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  if (adv_state.mirrors.indexOf(mirror) < 0) {
    if (adv_state.broken_mirrors.indexOf(mirror) < 0) {
      res.status(404).send();
    }
    else {
      res.status(410).send();
    }
    return;
  }

  if (mirror === adv_state.unbreakable) {
    res.status(405).send();
    return;
  }

  adv_state.broken_mirrors.push(mirror);

  var index = adv_state.mirrors.indexOf(mirror);
  if (index > -1) {
    adv_state.mirrors.splice(index, 1);
  }

  var imagesLeft = adv_state.mirrors.length;
  var imageNo = 7 - imagesLeft;
  var imageFileName = 'mirrors-' + imageNo + '-left-' + imagesLeft;
  setFsmImage('mirrors', imageFileName);

  res.status(204).location(alink('mirrors')).send();
}

app.delete('/hywit/:adv_id/mirrors/:mirror', function(req, res) {
  breakMirror(req, res);
});

app.get('/hywit/:adv_id/room', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (adv_state.closed) {
    res.status(302).location(alink('hill')).send();
    return;
  }

  var self_link = alink('room');

  var siren = {
    "title": "The Unassuming Room",
    "class": [ "location" ],
    "properties": {
      "name": "The Unassuming Room",
      "description": "You're in a plain room. It's not particularly interesting, but the HTTP acolyte in you senses something eerie. There's a door to the south. You also notice that there is a square hole in the ceiling."
    },
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "move", "south" ], "href": alink('mirrors'), "title": "Go back to the room of mirrors." }
    ]
  };

  var roomImage = { "rel": [ "view" ], "href": imglink('room-roof.png'), "type": "image/png" };

  if (adv_state.room) {
    roomImage = { "rel": [ "view" ], "href": imglink('room-floor.png'), "type": "image/png" };
    siren.properties.description = "You're in a plain room. There's a door to the south. More interestingly, there is also a square hole in the floor.";
    siren.links.push({ "rel": [ "move", "down" ], "href": alink("study"), "title": "Enter the hole in the floor." });

    setFsmImage('room', 'room-1-floor');
  }

  siren.links.push(roomImage);

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

var ltrSignText = 'thetowerofthemightywizardedsgeristhatway';
var rtlSignText = ltrSignText.reverse();
var signText = rtlSignText;
var ltrOrientation = 'Left-to-right';
var rtlOrientation = 'Right-to-left';
var signOrientation = rtlOrientation;

app.get('/hywit/:adv_id/sign', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];
  var alink = function (relative) {
    return advlink(adv_id, relative);
  };
  var self_link = alink('sign');
  var signDesc = "The sign says '" + signText + "'.";
  var siren = {
    "title": "The Mysterious Sign",
    "class": [ "entity" ],
    "properties": {
      "name": "The Mysterious Sign",
      "description": signDesc,
      "orientation": signOrientation
    },
    "actions": [
      {
        "name": "turn-sign",
        "title": "Reorient the sign.",
        "method": "PUT",
        "href": self_link,
        "fields": [
          { "name": "orientation", "type": "text" }
        ]
      }
    ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "previous"], "href": alink("island") },
      { "rel": [ "view" ], "href": imglink('sign.png'), "type": "image/png" }
    ]
  };

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/entrance', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var self_link = alink('entrance');
  var siren = {
    "title": "The Tower Entrance",
    "class": [ "location" ],
    "properties": {
      "name": "The Tower Entrance",
      "description": "You're standing in front of the tower of the mighty wizard. There's a great oak door in front of you. The door has no door knob. A skull floats ominously in front of the door.",
    },
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "move", "enter" ], "href": alink("tower"), "title": "Enter the tower." },
      { "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('snacks') },
      { "rel": [ "view" ], "href": imglink('entrance.png'), "type": "image/png" }
    ]
  };

  if (adv_state.bridge) {
    adv_state.skeleton = true;
    siren = {
      "title": "The Tower Entrance",
      "class": [ "location" ],
      "properties": {
        "name": "The Tower Entrance",
        "description": "As you reach the end of the bridge, you hear a great rattling of bones. A skeleton has risen in the middle of the bridge and is coming toward you. You better think quickly what to do."
      },
      "links": [
        { "rel": [ "self" ], "href": self_link },
        { "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('snacks') },
        { "rel": [ "view" ], "href": imglink('entrance.png'), "type": "image/png" }
      ]
    };
  }
  else {
    siren.properties.description = siren.properties.description + " The skeleton is pacing back and forth, trapped on the floating bridge.";
    if (adv_state.old_state) {
      siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
    }

    setFsmImage('entrance', 'entrance-1-safe');
  }

  toResponse(req, res, siren);
});

app.get('/hywit/:adv_id/snacks', function(req, res) {
  var adv_id = req.params.adv_id;
  var alink = function (relative) {
    return advlink(adv_id, relative);
  };
  var self_link = alink('snacks');
  var siren = {
    "title": "A bag of popcorn?",
    "class": [ "location" ],
    "properties": {
      "name": "A bag of popcorn?",
      "description": "Incredibly, it seems someone has left a bag of popcorn here. The bag says 'Dr Hofstadter's snacks'.",
    },
    "actions": [
      {
        "name": "eat-snacks",
        "title": "Eat some of Dr Hofstadter's popcorn.",
        "method": "POST",
        "href": self_link
      }
    ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "previous"], "href": alink("entrance") }
    ]
  };

  toResponse(req, res, siren);
});

app.post('/hywit/:adv_id/snacks', function(req, res) {
  var siren = {
    "title": "Pushcorn",
    "class": [ "location" ],
    "properties": {
      "name": "Pushcorn",
      "description": "Popcorn and pushcorn are incredibly hard to tell apart. You have a strange sensation as you seem to fall through into a new world, except it's remarkably like the old world. Somewhere, a turtle is laughing."
    }
  };

  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  adv_state.location = alink('entrance');

  startGame(req, res, adv_state, siren);
});

app.get('/hywit/:adv_id/skcans', function(req, res) {
  var adv_id = req.params.adv_id;
  var alink = function (relative) {
    return advlink(adv_id, relative);
  };
  var self_link = alink('skcans');
  var siren = {
    "title": "A bag of popcorn?",
    "class": [ "location" ],
    "properties": {
      "name": "A bag of popcorn?",
      "description": "You still have the bag of 'Dr Hofstadter's snacks'."
    },
    "actions": [
      {
        "name": "eat-snacks",
        "title": "Eat some of Dr Hofstadter's popcorn.",
        "method": "POST",
        "href": self_link
      }
    ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "previous"], "href": alink("entrance") }
    ]
  };

  toResponse(req, res, siren);
});

app.post('/hywit/:adv_id/skcans', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var loc = adv_state.old_state.location;

  var siren = {
    "title": "Popcorn",
    "class": [ "location" ],
    "properties": {
      "name": "Popcorn",
      "description": "Popcorn and pushcorn are incredibly hard to tell apart. You have a strange sensation as you seem to fall out from the new world and back to the old one. Somewhere, a laugh is turtleing."
    }
  };

  setFsmImage('pcorn', 'pcorn-0');

  res.status(302).location(adv_state.old_state.location).contentType('application/vnd.siren+json').send(siren);
});

app.get('/hywit/:adv_id/tower', function(req, res){
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (req.headers.authorization) {
    var authHeader = req.headers.authorization;
    var encodedAuthString = authHeader.substring("Basic ".length);
    var decodedAuthString = Buffer.from(encodedAuthString, 'base64').toString('ascii');
    //console.log(decodedAuthString)
    var decomp = decodedAuthString.split(':');
    var username = decomp[0];
    var password = decomp[1];
    tryEnterTower(req, res, password);
    return;
  }

  var self_link = alink('tower');
  var siren = {
    "title": "The Guardian Skull",
    "class": [ "challenge" ],
    "properties": {
      "name": "The Guardian Skull",
      "description": "The eyes of the floating skull ignite and a voice booms 'Who is my master?', sending shivers down your spine.",
    },
    "actions": [
      {
        "name": "answer-skull",
        "title": "State the name of the skull's master.",
        "method": "POST",
        "href": self_link,
        "fields": [
          { "name": "master", "type": "text" }
        ]
      }
    ],
    "links": [
      { "rel": [ "self" ], "href": self_link },
      { "rel": [ "previous" ], "href": alink("entrance") },
      { "rel": [ "view" ], "href": imglink("guardian-skull.png"), type: "image/png" }
    ]
  };

  if (adv_state.old_state) {
    siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
  }

  setFsmImage('auth', 'auth-401');

  toResponse(req, res, siren, 401);
});

function tryEnterTower(req, res, master) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  if (masterWizardName === master) {
    adv_state.closed = false;
    setFsmImage('auth', 'auth-200');
    res.status(302).location(alink('hall')).send('You may enter.');
  }
  else {
    var siren = {
      "title": "The Guardian Skull",
      "class": [ "challenge" ],
      "properties": {
        "name": "The Guardian Skull",
        "description": `The skull shrieks 'Wrong answer, ${master} is not my Master!', and the red glow in its eyes fades out.`,
      },
      "links": [
        { "rel": [ "self" ], "href": alink('tower') },
        { "rel": [ "previous" ], "href": alink('entrance') },
        { "rel": [ "view" ], "href": imglink('guardian-skull.png'), "type": "image/png" }
      ]
    };

    setFsmImage('auth', 'auth-403');

    toResponse(req, res, siren, 403);
  }
}

app.post('/hywit/:adv_id/tower', function(req, res) {
  tryEnterTower(req, res, req.body.master);
});

function turnSign(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];
  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };
  var self_link = alink('sign');
  var orientation = req.body.orientation;

  if (orientation === rtlOrientation || orientation === ltrOrientation) {
    // Legal value at least!
    if (orientation === signOrientation) {
      console.log("No changes to be made.");
    }
    else {
      if (orientation === rtlOrientation) {
        signOrientation = rtlOrientation;
        signText = rtlSignText;
      }
      else {
        // This is the legible way.
        adv_state.wizardname = masterWizardName;
        signOrientation = ltrOrientation;
        signText = ltrSignText;
      }
    }

    var signDesc = "The sign says '" + signText + "'.";
    var siren = {
      "title": "The Mysterious Sign",
      "class": [ "entity" ],
      "properties": {
        "name": "The Mysterious Sign",
        "description": signDesc,
        "orientation": signOrientation
      },
      "actions": [
        {
          "name": "turn-sign",
          "title": "Reorient the sign.",
          "method": "PUT",
          "href": self_link,
          "fields": [
            { "name": "orientation", "type": "text" }
          ]
        }
      ],
      "links": [
        { "rel": [ "self" ], "href": self_link },
        { "rel": [ "previous"], "href": alink("island") },
        { "rel": [ "view" ], "href": imglink('sign.png'), "type": "image/png" }
      ]
    };

    if (adv_state.old_state) {
      siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
    }

    toResponse(req, res, siren);
  }
  else {
    res.status(400).send("Illegal value for 'orientation': " + orientation);
  }

  var fsmImage = 'sign-0-gibberish';
  if (signOrientation === ltrOrientation) {
    fsmImage = 'sign-1-readable';
  }

  setFsmImage('sign', fsmImage);
}

app.put('/hywit/:adv_id/sign', function(req, res) {
  turnSign(req, res);
});

app.post('/hywit/:adv_id/sign', function(req, res) {
  turnSign(req, res);
});

function startGame(req, res, old_state, siren) {

  var adv_id = s4();
  var ts = new Date().getTime();
  var one_hour_in_millis = 60*60*1000;
  var age_limit = 3 * one_hour_in_millis;
  var existing_states = 0;
  var max_existing_states = 20;

  for (var aid in adventures)
  {
    ++existing_states;
    var st = adventures[aid];
    var age = ts - st.timestamp;
    if (aid !== permanent_aid && age > age_limit) {
      adventures[aid] = undefined;
    }
  }

  if (existing_states >= max_existing_states) {
    res.status(503).send();
    return;
  }

  adventures[adv_id] = init_state(adv_id, old_state);
  var url = hylink(adv_id + '/hill');
  if (siren) {
    setFsmImage('pcorn', 'pcorn-1');
    res.status(201).location(url).contentType('application/vnd.siren+json').send(siren);
  }
  else {
    setFsmImage('game', 'game-1');
    res.status(201).location(url).send();
  }
}

app.post('/hywit/void', function(req, res) {
  console.log("POST /hywit/void");
  // console.log(req);
  startGame(req, res);
});

app.get('/hywit/:adv_id/:resource', function(req, res) {
  var adv_id = req.params.adv_id;
  var adv_state = adventures[adv_id];

  if ('undefined' === typeof adv_state) {
    res.status(404).send();
    return;
  }

  var alink = function (relative) {
    return advlink(adv_id, relative);
  };

  var resource = req.params.resource;

  if (resource === 'brook') {

    var referer = req.headers['x-alt-referer'];
    if ('undefined' === typeof referer) {
      referer = req.headers.referer;
    }

    if (referer !== undefined) {
      if (referer.endsWith('cave')) {
        if (undefined === adv_state.grue) {
          res.status(302).location(alink('grue')).send("Uh oh.");
          return;
        }
      }
    }
  }

  if (!has_rep(resource)) {
    res.status(404).send();
    return;
  }

  var self_link = alink(resource);

  fs.readFile("reps/" + resource + ".json", 'utf8', function (err, data) {
    if (err) {
      return console.log(err);
    }
    var siren = JSON.parse(data);

    if (siren.actions) {
      var numActions = siren.actions.length;
      for (var i = 0; i < numActions; i++) {
        var action = siren.actions[i];
        if (action.href === "self") {
          action.href = self_link;
        }
        else {
          action.href = alink(action.href);
        }
      }
    }

    if (siren.links) {
      var numLinks = siren.links.length;
      for (var i = 0; i < numLinks; i++) {
        var hlink = siren.links[i];
        if (hlink.href === "self") {
          hlink.href = self_link;
        }
        else {
          if ('string' === typeof hlink.type && hlink.type.startsWith('image/')) {
            hlink.href = imglink(hlink.href);
          }
          else {
            hlink.href = alink(hlink.href);
          }
        }
      }

      if (adv_state.old_state) {
        siren.links.push({ "rel": [ "look" ], "title": "A bag of popcorn?", "href": alink('skcans') });
      }
    }

    if (resource === 'hill') {
      if (adv_state.wizardname !== undefined) {
        // console.log("replace!");
        siren.properties.description = siren.properties.description.replace("Unnamed Wizard", "Wizard " + masterWizardName);
        setFsmImage('hill', 'hill-1-known');
      }
      else if (adv_state.old_state !== undefined) {
        if (adv_state.old_state.wizardname !== undefined) {
          // console.log("replace!");
          siren.properties.description = siren.properties.description.replace("Unnamed Wizard", "Wizard " + masterWizardName);
        }
      }
    }

    toResponse(req, res, siren);
  });
});

var integerstr = "";
var fractionstr = "";
var dotSymbol = ".";
var stateEmptyNumber = { name: "empty-number", legal: false };
var stateBuildingInteger = { name: "building-integer", legal: true };
var stateDot = { name: "dot", legal: false };
var stateBuildingFraction = { name: "building-fraction", legal: true };
var state = stateEmptyNumber;

function getNonZeroDigit(s) {
  var d = getDigit(s);
  if (d === 0) {
    return undefined;
  }

  return d;
}

function getDigit(s) {
  var num = parseInt(s, 10);
  if (isNaN(num)) {
    return undefined;
  }

  if (num >= 0 && num < 10) {
    return num;
  }

  return undefined;
}

function handleStateEmptyNumber(symbol, res) {
  var d = getNonZeroDigit(symbol);
  if (d === undefined) {
    res.status(400).send();
    return;
  }

  state = stateBuildingInteger;
  setFsmImage('number', 'number-1-integer');
  integerstr = integerstr + symbol;

  res.status(200).send();
}

function handleStateBuildingInteger(symbol, res) {
  if (symbol === dotSymbol) {
    state = stateDot;
    setFsmImage('number', 'number-2-dot');
    res.status(200).send();
    return;
  }
  else {
    var d = getDigit(symbol);
    if (d === undefined) {
      res.status(400).send();
      return;
    }

    integerstr = integerstr + symbol;
    res.status(200).send();
  }
}

function handleStateDot(symbol, res) {
  var d = getDigit(symbol);
  if (d === undefined) {
    res.status(400).send();
    return;
  }

  state = stateBuildingFraction;
  setFsmImage('number', 'number-3-fraction');
  fractionstr = fractionstr + symbol;
  res.status(200).send();
}

function handleStateBuildingFraction(symbol, res) {
  var d = getDigit(symbol);
  if (d === undefined) {
    res.status(400).send();
    return;
  }

  fractionstr = fractionstr + symbol;
  res.status(200).send();
}

app.get('/number', function(req, res) {
  if (state.legal) {
    var num = integerstr;
    if (state === stateBuildingFraction) {
      num = integerstr + dotSymbol + fractionstr;
    }

    res.status(200).send(num);
    return;
  }

  if (state === stateEmptyNumber) {
    setFsmImage('number', 'number-0-empty');
  }
  res.status(404).send();
});

app.post('/number', function(req, res) {
  var symbol = req.body.symbol;

  if (state === stateEmptyNumber) {
    handleStateEmptyNumber(symbol, res);
    return;
  }

  if (state === stateBuildingInteger) {
    handleStateBuildingInteger(symbol, res);
    return;
  }

  if (state === stateDot) {
    handleStateDot(symbol, res);
    return;
  }

  if (state === stateBuildingFraction) {
    handleStateBuildingFraction(symbol, res);
    return;
  }

  res.status(500).send();
});

app.listen(port);