/// S2 Geometry functions
// the regional scoreboard is based on a level 6 S2 Cell
// - https://docs.google.com/presentation/d/1Hl4KapfAENAOf4gv-pSngKwvS_jwNVHRPZTTDzXXn6Q/view?pli=1#slide=id.i22
// at the time of writing there's no actual API for the intel map to retrieve scoreboard data,
// but it's still useful to plot the score cells on the intel map


// the S2 geometry is based on projecting the earth sphere onto a cube, with some scaling of face coordinates to
// keep things close to approximate equal area for adjacent cells
// to convert a lat,lng into a cell id:
// - convert lat,lng to x,y,z
// - convert x,y,z into face,u,v
// - u,v scaled to s,t with quadratic formula
// - s,t converted to integer i,j offsets
// - i,j converted to a position along a Hubbert space-filling curve
// - combine face,position to get the cell id

//NOTE: compared to the google S2 geometry library, we vary from their code in the following ways
// - cell IDs: they combine face and the hilbert curve position into a single 64 bit number. this gives efficient space
//             and speed. javascript doesn't have appropriate data types, and speed is not cricical, so we use
//             as [face,[bitpair,bitpair,...]] instead
// - i,j: they always use 30 bits, adjusting as needed. we use 0 to (1<<level)-1 instead
//        (so GetSizeIJ for a cell is always 1)

(function (exports) {
'use strict';

var S2 = exports.S2 = { L: {} };

S2.L.LatLng = function (/*Number*/ rawLat, /*Number*/ rawLng, /*Boolean*/ noWrap) {
  var lat = parseFloat(rawLat, 10);
  var lng = parseFloat(rawLng, 10);

  if (isNaN(lat) || isNaN(lng)) {
    throw new Error('Invalid LatLng object: (' + rawLat + ', ' + rawLng + ')');
  }

  if (noWrap !== true) {
    lat = Math.max(Math.min(lat, 90), -90);                 // clamp latitude into -90..90
    lng = (lng + 180) % 360 + ((lng < -180 || lng === 180) ? 180 : -180);   // wrap longtitude into -180..180
  }

  return { lat: lat, lng: lng };
};

S2.L.LatLng.DEG_TO_RAD = Math.PI / 180;
S2.L.LatLng.RAD_TO_DEG = 180 / Math.PI;

/*
S2.LatLngToXYZ = function(latLng) {
  // http://stackoverflow.com/questions/8981943/lat-long-to-x-y-z-position-in-js-not-working
  var lat = latLng.lat;
  var lon = latLng.lng;
  var DEG_TO_RAD = Math.PI / 180.0;

  var phi = lat * DEG_TO_RAD;
  var theta = lon * DEG_TO_RAD;

  var cosLat = Math.cos(phi);
  var sinLat = Math.sin(phi);
  var cosLon = Math.cos(theta);
  var sinLon = Math.sin(theta);
  var rad = 500.0;

  return [
    rad * cosLat * cosLon
  , rad * cosLat * sinLon
  , rad * sinLat
  ];
};
*/
S2.LatLngToXYZ = function(latLng) {
  var d2r = S2.L.LatLng.DEG_TO_RAD;

  var phi = latLng.lat*d2r;
  var theta = latLng.lng*d2r;

  var cosphi = Math.cos(phi);

  return [Math.cos(theta)*cosphi, Math.sin(theta)*cosphi, Math.sin(phi)];
};

S2.XYZToLatLng = function(xyz) {
  var r2d = S2.L.LatLng.RAD_TO_DEG;

  var lat = Math.atan2(xyz[2], Math.sqrt(xyz[0]*xyz[0]+xyz[1]*xyz[1]));
  var lng = Math.atan2(xyz[1], xyz[0]);

  return S2.L.LatLng(lat*r2d, lng*r2d);
};

var largestAbsComponent = function(xyz) {
  var temp = [Math.abs(xyz[0]), Math.abs(xyz[1]), Math.abs(xyz[2])];

  if (temp[0] > temp[1]) {
    if (temp[0] > temp[2]) {
      return 0;
    } else {
      return 2;
    }
  } else {
    if (temp[1] > temp[2]) {
      return 1;
    } else {
      return 2;
    }
  }

};

var faceXYZToUV = function(face,xyz) {
  var u,v;

  switch (face) {
    case 0: u =  xyz[1]/xyz[0]; v =  xyz[2]/xyz[0]; break;
    case 1: u = -xyz[0]/xyz[1]; v =  xyz[2]/xyz[1]; break;
    case 2: u = -xyz[0]/xyz[2]; v = -xyz[1]/xyz[2]; break;
    case 3: u =  xyz[2]/xyz[0]; v =  xyz[1]/xyz[0]; break;
    case 4: u =  xyz[2]/xyz[1]; v = -xyz[0]/xyz[1]; break;
    case 5: u = -xyz[1]/xyz[2]; v = -xyz[0]/xyz[2]; break;
    default: throw {error: 'Invalid face'};
  }

  return [u,v];
};




S2.XYZToFaceUV = function(xyz) {
  var face = largestAbsComponent(xyz);

  if (xyz[face] < 0) {
    face += 3;
  }

  var uv = faceXYZToUV (face,xyz);

  return [face, uv];
};

S2.FaceUVToXYZ = function(face,uv) {
  var u = uv[0];
  var v = uv[1];

  switch (face) {
    case 0: return [ 1, u, v];
    case 1: return [-u, 1, v];
    case 2: return [-u,-v, 1];
    case 3: return [-1,-v,-u];
    case 4: return [ v,-1,-u];
    case 5: return [ v, u,-1];
    default: throw {error: 'Invalid face'};
  }
};

var singleSTtoUV = function(st) {
  if (st >= 0.5) {
    return (1/3.0) * (4*st*st - 1);
  } else {
    return (1/3.0) * (1 - (4*(1-st)*(1-st)));
  }
};

S2.STToUV = function(st) {
  return [singleSTtoUV(st[0]), singleSTtoUV(st[1])];
};


var singleUVtoST = function(uv) {
  if (uv >= 0) {
    return 0.5 * Math.sqrt (1 + 3*uv);
  } else {
    return 1 - 0.5 * Math.sqrt (1 - 3*uv);
  }
};
S2.UVToST = function(uv) {
  return [singleUVtoST(uv[0]), singleUVtoST(uv[1])];
};


S2.STToIJ = function(st,order) {
  var maxSize = (1<<order);

  var singleSTtoIJ = function(st) {
    var ij = Math.floor(st * maxSize);
    return Math.max(0, Math.min(maxSize-1, ij));
  };

  return [singleSTtoIJ(st[0]), singleSTtoIJ(st[1])];
};


S2.IJToST = function(ij,order,offsets) {
  var maxSize = (1<<order);

  return [
    (ij[0]+offsets[0])/maxSize,
    (ij[1]+offsets[1])/maxSize
  ];
};



var rotateAndFlipQuadrant = function(n, point, rx, ry)
{
	var newX, newY;
	if(ry == 0)
	{
		if(rx == 1){
			point.x = n - 1 - point.x;
			point.y = n - 1 - point.y

		}

    var x = point.x;
		point.x = point.y
		point.y = x;
	}

}





// hilbert space-filling curve
// based on http://blog.notdot.net/2009/11/Damn-Cool-Algorithms-Spatial-indexing-with-Quadtrees-and-Hilbert-Curves
// note: rather then calculating the final integer hilbert position, we just return the list of quads
// this ensures no precision issues whth large orders (S3 cell IDs use up to 30), and is more
// convenient for pulling out the individual bits as needed later
var pointToHilbertQuadList = function(x,y,order,face) {
  var hilbertMap = {
    'a': [ [0,'d'], [1,'a'], [3,'b'], [2,'a'] ],
    'b': [ [2,'b'], [1,'b'], [3,'a'], [0,'c'] ],
    'c': [ [2,'c'], [3,'d'], [1,'c'], [0,'b'] ],
    'd': [ [0,'a'], [3,'c'], [1,'d'], [2,'d'] ]
  };

  if ('number' !== typeof face) {
    console.warn(new Error("called pointToHilbertQuadList without face value, defaulting to '0'").stack);
  }
  var currentSquare = (face % 2) ? 'd' : 'a';
  var positions = [];

  for (var i=order-1; i>=0; i--) {

    var mask = 1<<i;

    var quad_x = x&mask ? 1 : 0;
    var quad_y = y&mask ? 1 : 0;

    var t = hilbertMap[currentSquare][quad_x*2+quad_y];

    positions.push(t[0]);

    currentSquare = t[1];
  }

  return positions;
};

// S2Cell class

S2.S2Cell = function(){};

S2.S2Cell.FromHilbertQuadKey = function(hilbertQuadkey) {
  var parts = hilbertQuadkey.split('/');
  var face = parseInt(parts[0]);
  var position = parts[1];
  var maxLevel = position.length;
  var point = {
    x : 0,
    y: 0
  };
  var i;
  var level;
  var bit;
  var rx, ry;
  var val;

	for(i = maxLevel - 1; i >= 0; i--) {

		level = maxLevel - i;
		bit = position[i];
		rx = 0;
    ry = 0;
		if (bit === '1') {
			ry = 1;
		}
		else if (bit === '2') {
			rx = 1;
			ry = 1;
		}
		else if (bit === '3') {
			rx = 1;
		}

		val = Math.pow(2, level - 1);
		rotateAndFlipQuadrant(val, point, rx, ry);

		point.x += val * rx;
		point.y += val * ry;

	}

  if (face % 2 === 1) {
    var t = point.x;
    point.x = point.y;
    point.y = t;
  }


  return S2.S2Cell.FromFaceIJ(parseInt(face), [point.x, point.y], level);
};

//static method to construct
S2.S2Cell.FromLatLng = function(latLng, level) {
  if ((!latLng.lat && latLng.lat !== 0) || (!latLng.lng && latLng.lng !== 0)) {
    throw new Error("Pass { lat: lat, lng: lng } to S2.S2Cell.FromLatLng");
  }
  var xyz = S2.LatLngToXYZ(latLng);

  var faceuv = S2.XYZToFaceUV(xyz);
  var st = S2.UVToST(faceuv[1]);

  var ij = S2.STToIJ(st,level);

  return S2.S2Cell.FromFaceIJ (faceuv[0], ij, level);
};

/*
S2.faceIjLevelToXyz = function (face, ij, level) {
  var st = S2.IJToST(ij, level, [0.5, 0.5]);
  var uv = S2.STToUV(st);
  var xyz = S2.FaceUVToXYZ(face, uv);

  return S2.XYZToLatLng(xyz);
  return xyz;
};
*/

S2.S2Cell.FromFaceIJ = function(face,ij,level) {
  var cell = new S2.S2Cell();
  cell.face = face;
  cell.ij = ij;
  cell.level = level;

  return cell;
};


S2.S2Cell.prototype.toString = function() {
  return 'F'+this.face+'ij['+this.ij[0]+','+this.ij[1]+']@'+this.level;
};

S2.S2Cell.prototype.getLatLng = function() {
  var st = S2.IJToST(this.ij,this.level, [0.5,0.5]);
  var uv = S2.STToUV(st);
  var xyz = S2.FaceUVToXYZ(this.face, uv);

  return S2.XYZToLatLng(xyz);
};

S2.S2Cell.prototype.getCornerLatLngs = function() {
  var result = [];
  var offsets = [
    [ 0.0, 0.0 ],
    [ 0.0, 1.0 ],
    [ 1.0, 1.0 ],
    [ 1.0, 0.0 ]
  ];

  for (var i=0; i<4; i++) {
    var st = S2.IJToST(this.ij, this.level, offsets[i]);
    var uv = S2.STToUV(st);
    var xyz = S2.FaceUVToXYZ(this.face, uv);

    result.push ( S2.XYZToLatLng(xyz) );
  }
  return result;
};


S2.S2Cell.prototype.getFaceAndQuads = function () {
  var quads = pointToHilbertQuadList(this.ij[0], this.ij[1], this.level, this.face);

  return [this.face,quads];
};
S2.S2Cell.prototype.toHilbertQuadkey = function () {
  var quads = pointToHilbertQuadList(this.ij[0], this.ij[1], this.level, this.face);

  return this.face.toString(10) + '/' + quads.join('');
};

S2.latLngToNeighborKeys = S2.S2Cell.latLngToNeighborKeys = function (lat, lng, level) {
  return S2.S2Cell.FromLatLng({ lat: lat, lng: lng }, level).getNeighbors().map(function (cell) {
    return cell.toHilbertQuadkey();
  });
};
S2.S2Cell.prototype.getNeighbors = function() {

  var fromFaceIJWrap = function(face,ij,level) {
    var maxSize = (1<<level);
    if (ij[0]>=0 && ij[1]>=0 && ij[0]<maxSize && ij[1]<maxSize) {
      // no wrapping out of bounds
      return S2.S2Cell.FromFaceIJ(face,ij,level);
    } else {
      // the new i,j are out of range.
      // with the assumption that they're only a little past the borders we can just take the points as
      // just beyond the cube face, project to XYZ, then re-create FaceUV from the XYZ vector

      var st = S2.IJToST(ij,level,[0.5,0.5]);
      var uv = S2.STToUV(st);
      var xyz = S2.FaceUVToXYZ(face,uv);
      var faceuv = S2.XYZToFaceUV(xyz);
      face = faceuv[0];
      uv = faceuv[1];
      st = S2.UVToST(uv);
      ij = S2.STToIJ(st,level);
      return S2.S2Cell.FromFaceIJ (face, ij, level);
    }
  };

  var face = this.face;
  var i = this.ij[0];
  var j = this.ij[1];
  var level = this.level;


  return [
    fromFaceIJWrap(face, [i-1,j], level),
    fromFaceIJWrap(face, [i,j-1], level),
    fromFaceIJWrap(face, [i+1,j], level),
    fromFaceIJWrap(face, [i,j+1], level)
  ];

};

//
// Functional Style
//
S2.FACE_BITS = 3;
S2.MAX_LEVEL = 30;
S2.POS_BITS = (2 * S2.MAX_LEVEL) + 1; // 61 (60 bits of data, 1 bit lsb marker)

S2.facePosLevelToId = S2.S2Cell.facePosLevelToId = S2.fromFacePosLevel = function (faceN, posS, levelN) {
  var Long = exports.dcodeIO && exports.dcodeIO.Long || require('long');
  var faceB;
  var posB;
  var bin;

  if (!levelN) {
    levelN = posS.length;
  }
  if (posS.length > levelN) {
    posS = posS.substr(0, levelN);
  }

  // 3-bit face value
  faceB = Long.fromString(faceN.toString(10), true, 10).toString(2);
  while (faceB.length < S2.FACE_BITS) {
    faceB = '0' + faceB;
  }

  // 60-bit position value
  posB = Long.fromString(posS, true, 4).toString(2);
  while (posB.length < (2 * levelN)) {
    posB = '0' + posB;
  }

  bin = faceB + posB;
  // 1-bit lsb marker
  bin += '1';
  // n-bit padding to 64-bits
  while (bin.length < (S2.FACE_BITS + S2.POS_BITS)) {
    bin += '0';
  }

  return Long.fromString(bin, true, 2).toString(10);
};

S2.keyToId = S2.S2Cell.keyToId
= S2.toId = S2.toCellId = S2.fromKey
= function (key) {
  var parts = key.split('/');

  return S2.fromFacePosLevel(parts[0], parts[1], parts[1].length);
};

S2.idToKey = S2.S2Cell.idToKey
= S2.S2Cell.toKey = S2.toKey
= S2.fromId = S2.fromCellId
= S2.S2Cell.toHilbertQuadkey  = S2.toHilbertQuadkey
= function (idS) {
  var Long = exports.dcodeIO && exports.dcodeIO.Long || require('long');
  var bin = Long.fromString(idS, true, 10).toString(2);

  while (bin.length < (S2.FACE_BITS + S2.POS_BITS)) {
    bin = '0' + bin;
  }

  // MUST come AFTER binstr has been left-padded with '0's
  var lsbIndex = bin.lastIndexOf('1');
  // substr(start, len)
  // substring(start, end) // includes start, does not include end
  var faceB = bin.substring(0, 3);
  // posB will always be a multiple of 2 (or it's invalid)
  var posB = bin.substring(3, lsbIndex);
  var levelN = posB.length / 2;

  var faceS = Long.fromString(faceB, true, 2).toString(10);
  var posS = Long.fromString(posB, true, 2).toString(4);

  while (posS.length < levelN) {
    posS = '0' + posS;
  }

  return faceS + '/' + posS;
};

S2.keyToLatLng = S2.S2Cell.keyToLatLng = function (key) {
  var cell2 = S2.S2Cell.FromHilbertQuadKey(key);
  return cell2.getLatLng();
};

S2.idToLatLng = S2.S2Cell.idToLatLng = function (id) {
  var key = S2.idToKey(id);
  return S2.keyToLatLng(key);
};

S2.S2Cell.latLngToKey = S2.latLngToKey
= S2.latLngToQuadkey = function (lat, lng, level) {
  if (isNaN(level) || level < 1 || level > 30) {
    throw new Error("'level' is not a number between 1 and 30 (but it should be)");
  }
  // TODO
  //
  // S2.idToLatLng(id)
  // S2.keyToLatLng(key)
  // S2.nextFace(key)     // prevent wrapping on nextKey
  // S2.prevFace(key)     // prevent wrapping on prevKey
  //
  // .toKeyArray(id)  // face,quadtree
  // .toKey(id)       // hilbert
  // .toPoint(id)     // ij
  // .toId(key)       // uint64 (as string)
  // .toLong(key)     // long.js
  // .toLatLng(id)    // object? or array?, or string (with comma)?
  //
  // maybe S2.HQ.x, S2.GPS.x, S2.CI.x?
  return S2.S2Cell.FromLatLng({ lat: lat, lng: lng }, level).toHilbertQuadkey();
};

S2.stepKey = function (key, num) {
  var Long = exports.dcodeIO && exports.dcodeIO.Long || require('long');
  var parts = key.split('/');

  var faceS = parts[0];
  var posS = parts[1];
  var level = parts[1].length;

  var posL = Long.fromString(posS, true, 4);
  // TODO handle wrapping (0 === pos + 1)
  // (only on the 12 edges of the globe)
  var otherL;
  if (num > 0) {
    otherL = posL.add(Math.abs(num));
  }
  else if (num < 0) {
    otherL = posL.subtract(Math.abs(num));
  }
  var otherS = otherL.toString(4);

  if ('0' === otherS) {
    console.warning(new Error("face/position wrapping is not yet supported"));
  }

  while (otherS.length < level) {
    otherS = '0' + otherS;
  }

  return faceS + '/' + otherS;
};

S2.S2Cell.prevKey = S2.prevKey = function (key) {
  return S2.stepKey(key, -1);
};

S2.S2Cell.nextKey = S2.nextKey = function (key) {
  return S2.stepKey(key, 1);
};

})('undefined' !== typeof module ? module.exports : window);