Team:Lethbridge/randomize js

/* A 16-bit random number generator. This outputs an non-negative integer on the interval [0, n). This enjoys the property that it will never produce the same number twice in a row.

• /

function nonRedundantRandom(n) {

   // Give this function a member that stores the last computed random
   // number. This number will not be be generated this time. If it is
   // generated, the function will recurse until it generates a different
   // number.
   if (typeof nonRedundantRandom.last === 'undefined') {
       nonRedundantRandom.last = -1;
   }

   // Handle the case where n is less than 2. If n is 1, then the function
   // will perform infinte recursions, and if it is negative the behaviour
   // will be undefined. Return 0 and forgeet about these silly inputs :)
   if (n < 2) {
       return 0;
   }

   // Generate some random 16-bit numbers based of of the largest unsigned
   // 16-bit prime
   var large_prime = 65521;
   var twist0 = Math.floor(Math.random() * 65521);
   var twist1 = Math.floor(Math.random() * 65521);
   var twist2 = Math.floor(Math.random() * 65521);

   // Do a series of bit shifts, swaps, flips, and other goofy things
   twist0 = (twist1 >> (twist0 << Math.floor(Math.random() * 16)));
   twist0 = ((twist0 >> Math.floor(Math.random() * 16)) ^ twist2);
   twist1 = twist0 & twist2;
   twist2 = twist1 ^ (twist2 & ((twist0 >> 8) + (twist0 << 8)));

   // This is a random number on the interval [0, n - 1]
   var random_number = Math.abs((twist0 * twist1) ^ twist2) % n;
   if (random_number != nonRedundantRandom.last) {
       nonRedundantRandom.last = random_number;
       return random_number;
   }
   else {
       return nonRedundantRandom(n);
   }

}

/* Returns a random color from its set

• /

function randomColor() {

   var colors = [
       '#fd6769', // red
       '#fec66a', // tangerine
       '#6ce980', // green
       '#898cd2', // blue
       '#9e68cc'  // purple
   ];
   var index = nonRedundantRandom(colors.length);
   return colors[index];

}

/* Returns a random texture from its set

• /

function randomTexture() {

   var textures = [
       'url(../img/tiled_dots.png)',
       'url(../img/tiled_holes.png)',
       'url(../img/tiled_dlstripes.png)',
       'url(../img/tiled_drstripes.png)',
       'url(../img/tiled_hstripes.png)',
       'url(../img/tiled_vstripes.png)',
       'url(../img/tiled_diamond.png)',
       'none'
   ];
   var index = nonRedundantRandom(textures.length);
   return textures[index];

}