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var chunker = require('./chunker')
var ndarray = require('ndarray')
 
module.exports = function(opts) {
  if (!opts.generateVoxelChunk) opts.generateVoxelChunk = function(low, high) {
    return generate(low, high, module.exports.generator['Valley'])
  }
  return chunker(opts)
}
 
module.exports.meshers = {
  culled: require('./meshers/culled').mesher,
  greedy: require('./meshers/greedy').mesher,
  transgreedy: require('./meshers/transgreedy').mesher,
  monotone: require('./meshers/monotone').mesher,
  stupid: require('./meshers/stupid').mesher
}
 
module.exports.Chunker = chunker.Chunker
module.exports.geometry = {}
module.exports.generator = {}
module.exports.generate = generate
 
function generate(lo, hi, fn, game) {
  // To fix the display gaps, we need to pad the bounds
  lo[0]--
  lo[1]--
  lo[2]--
  hi[0]++
  hi[1]++
  hi[2]++
  var dims = [hi[2]-lo[2], hi[1]-lo[1], hi[0]-lo[0]]
  var data = ndarray(new Uint16Array(dims[2] * dims[1] * dims[0]), dims)
  for (var k = lo[2]; k < hi[2]; k++)
    for (var j = lo[1]; j < hi[1]; j++)
      for(var i = lo[0]; i < hi[0]; i++) {
        data.set(k-lo[2], j-lo[1], i-lo[0], fn(i, j, k))
      }
  return data
}
 
// shape and terrain generator functions
module.exports.generator['Sphere'] = function(i,j,k) {
  return i*i+j*j+k*k <= 16*16 ? 1 : 0
}
 
module.exports.generator['Noise'] = function(i,j,k) {
  return Math.random() < 0.1 ? Math.random() * 0xffffff : 0;
}
 
module.exports.generator['Dense Noise'] = function(i,j,k) {
  return Math.round(Math.random() * 0xffffff);
}
 
module.exports.generator['Checker'] = function(i,j,k) {
  return !!((i+j+k)&1) ? (((i^j^k)&2) ? 1 : 0xffffff) : 0;
}
 
module.exports.generator['Hill'] = function(i,j,k) {
  return j <= 16 * Math.exp(-(i*i + k*k) / 64) ? 1 : 0;
}
 
module.exports.generator['Valley'] = function(i,j,k) {
  return j <= (i*i + k*k) * 31 / (32*32*2) + 1 ? 1 + (1<<15) : 0;
}
 
module.exports.generator['Hilly Terrain'] = function(i,j,k) {
  var h0 = 3.0 * Math.sin(Math.PI * i / 12.0 - Math.PI * k * 0.1) + 27;    
  if(j > h0+1) {
    return 0;
  }
  if(h0 <= j) {
    return 1;
  }
  var h1 = 2.0 * Math.sin(Math.PI * i * 0.25 - Math.PI * k * 0.3) + 20;
  if(h1 <= j) {
    return 2;
  }
  if(2 < j) {
    return Math.random() < 0.1 ? 0x222222 : 0xaaaaaa;
  }
  return 3;
}
 
module.exports.scale = function ( x, fromLow, fromHigh, toLow, toHigh ) {
  return ( x - fromLow ) * ( toHigh - toLow ) / ( fromHigh - fromLow ) + toLow
}
 
// convenience function that uses the above functions to prebake some simple voxel geometries
module.exports.generateExamples = function() {
  return {
    'Sphere': generate([-16,-16,-16], [16,16,16], module.exports.generator['Sphere']),
    'Noise': generate([0,0,0], [16,16,16], module.exports.generator['Noise']),
    'Dense Noise': generate([0,0,0], [16,16,16], module.exports.generator['Dense Noise']),
    'Checker': generate([0,0,0], [8,8,8], module.exports.generator['Checker']),
    'Hill': generate([-16, 0, -16], [16,16,16], module.exports.generator['Hill']),
    'Valley': generate([0,0,0], [32,32,32], module.exports.generator['Valley']),
    'Hilly Terrain': generate([0, 0, 0], [32,32,32], module.exports.generator['Hilly Terrain'])
  }
}