"use strict";

var Matrix = require('sylvester.js').Matrix;
var Vector = require('sylvester.js').Vector;
var $M     = Matrix.create;


// augment Sylvester some
Matrix.Translation = function (v)
{
  if (v.elements.length == 2) {
    var r = Matrix.I(3);
    r.elements[2][0] = v.elements[0];
    r.elements[2][1] = v.elements[1];
    return r;
  }

  if (v.elements.length == 3) {
    var r = Matrix.I(4);
    r.elements[0][3] = v.elements[0];
    r.elements[1][3] = v.elements[1];
    r.elements[2][3] = v.elements[2];
    return r;
  }

  throw "Invalid length for Translation";
}

Matrix.prototype.flatten = function ()
{
    var result = [];
    if (this.elements.length == 0)
        return [];


    for (var j = 0; j < this.elements[0].length; j++)
        for (var i = 0; i < this.elements.length; i++)
            result.push(this.elements[i][j]);
    return result;
}

Matrix.prototype.ensure4x4 = function()
{
    if (this.elements.length == 4 &&
        this.elements[0].length == 4)
        return this;

    if (this.elements.length > 4 ||
        this.elements[0].length > 4)
        return null;

    for (var i = 0; i < this.elements.length; i++) {
        for (var j = this.elements[i].length; j < 4; j++) {
            if (i == j)
                this.elements[i].push(1);
            else
                this.elements[i].push(0);
        }
    }

    for (var i = this.elements.length; i < 4; i++) {
        if (i == 0)
            this.elements.push([1, 0, 0, 0]);
        else if (i == 1)
            this.elements.push([0, 1, 0, 0]);
        else if (i == 2)
            this.elements.push([0, 0, 1, 0]);
        else if (i == 3)
            this.elements.push([0, 0, 0, 1]);
    }

    return this;
};


Vector.prototype.flatten = function ()
{
    return this.elements;
};



//
// gluPerspective
//
function makePerspective(fovy, aspect, znear, zfar)
{
    var ymax = znear * Math.tan(fovy * Math.PI / 360.0);
    var ymin = -ymax;
    var xmin = ymin * aspect;
    var xmax = ymax * aspect;

    return makeFrustum(xmin, xmax, ymin, ymax, znear, zfar);
}

//
// glFrustum
//
function makeFrustum(left, right,
                     bottom, top,
                     znear, zfar)
{
    var X = 2*znear/(right-left);
    var Y = 2*znear/(top-bottom);
    var A = (right+left)/(right-left);
    var B = (top+bottom)/(top-bottom);
    var C = -(zfar+znear)/(zfar-znear);
    var D = -2*zfar*znear/(zfar-znear);

    return $M([[X, 0, A, 0],
               [0, Y, B, 0],
               [0, 0, C, D],
               [0, 0, -1, 0]]);
}

module.exports.makePerspective = makePerspective;