/* Copyright (c) 2015, Brandon Jones, Colin MacKenzie IV.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE. */

import * as glMatrix from "./common.js";

/**
 * 2 Dimensional Vector
 * @module vec2
 */

/**
 * Creates a new, empty vec2
 *
 * @returns {vec2} a new 2D vector
 */
export function create() {
  let out = new glMatrix.ARRAY_TYPE(2);
  out[0] = 0;
  out[1] = 0;
  return out;
}

/**
 * Creates a new vec2 initialized with values from an existing vector
 *
 * @param {vec2} a vector to clone
 * @returns {vec2} a new 2D vector
 */
export function clone(a) {
  let out = new glMatrix.ARRAY_TYPE(2);
  out[0] = a[0];
  out[1] = a[1];
  return out;
}

/**
 * Creates a new vec2 initialized with the given values
 *
 * @param {Number} x X component
 * @param {Number} y Y component
 * @returns {vec2} a new 2D vector
 */
export function fromValues(x, y) {
  let out = new glMatrix.ARRAY_TYPE(2);
  out[0] = x;
  out[1] = y;
  return out;
}

/**
 * Copy the values from one vec2 to another
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the source vector
 * @returns {vec2} out
 */
export function copy(out, a) {
  out[0] = a[0];
  out[1] = a[1];
  return out;
}

/**
 * Set the components of a vec2 to the given values
 *
 * @param {vec2} out the receiving vector
 * @param {Number} x X component
 * @param {Number} y Y component
 * @returns {vec2} out
 */
export function set(out, x, y) {
  out[0] = x;
  out[1] = y;
  return out;
}

/**
 * Adds two vec2's
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec2} out
 */
export function add(out, a, b) {
  out[0] = a[0] + b[0];
  out[1] = a[1] + b[1];
  return out;
}

/**
 * Subtracts vector b from vector a
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec2} out
 */
export function subtract(out, a, b) {
  out[0] = a[0] - b[0];
  out[1] = a[1] - b[1];
  return out;
}

/**
 * Multiplies two vec2's
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec2} out
 */
export function multiply(out, a, b) {
  out[0] = a[0] * b[0];
  out[1] = a[1] * b[1];
  return out;
};

/**
 * Divides two vec2's
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec2} out
 */
export function divide(out, a, b) {
  out[0] = a[0] / b[0];
  out[1] = a[1] / b[1];
  return out;
};

/**
 * Math.ceil the components of a vec2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a vector to ceil
 * @returns {vec2} out
 */
export function ceil(out, a) {
  out[0] = Math.ceil(a[0]);
  out[1] = Math.ceil(a[1]);
  return out;
};

/**
 * Math.floor the components of a vec2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a vector to floor
 * @returns {vec2} out
 */
export function floor(out, a) {
  out[0] = Math.floor(a[0]);
  out[1] = Math.floor(a[1]);
  return out;
};

/**
 * Returns the minimum of two vec2's
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec2} out
 */
export function min(out, a, b) {
  out[0] = Math.min(a[0], b[0]);
  out[1] = Math.min(a[1], b[1]);
  return out;
};

/**
 * Returns the maximum of two vec2's
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec2} out
 */
export function max(out, a, b) {
  out[0] = Math.max(a[0], b[0]);
  out[1] = Math.max(a[1], b[1]);
  return out;
};

/**
 * Math.round the components of a vec2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a vector to round
 * @returns {vec2} out
 */
export function round (out, a) {
  out[0] = Math.round(a[0]);
  out[1] = Math.round(a[1]);
  return out;
};

/**
 * Scales a vec2 by a scalar number
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the vector to scale
 * @param {Number} b amount to scale the vector by
 * @returns {vec2} out
 */
export function scale(out, a, b) {
  out[0] = a[0] * b;
  out[1] = a[1] * b;
  return out;
};

/**
 * Adds two vec2's after scaling the second operand by a scalar value
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @param {Number} scale the amount to scale b by before adding
 * @returns {vec2} out
 */
export function scaleAndAdd(out, a, b, scale) {
  out[0] = a[0] + (b[0] * scale);
  out[1] = a[1] + (b[1] * scale);
  return out;
};

/**
 * Calculates the euclidian distance between two vec2's
 *
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {Number} distance between a and b
 */
export function distance(a, b) {
  var x = b[0] - a[0],
    y = b[1] - a[1];
  return Math.sqrt(x*x + y*y);
};

/**
 * Calculates the squared euclidian distance between two vec2's
 *
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {Number} squared distance between a and b
 */
export function squaredDistance(a, b) {
  var x = b[0] - a[0],
    y = b[1] - a[1];
  return x*x + y*y;
};

/**
 * Calculates the length of a vec2
 *
 * @param {vec2} a vector to calculate length of
 * @returns {Number} length of a
 */
export function length(a) {
  var x = a[0],
    y = a[1];
  return Math.sqrt(x*x + y*y);
};

/**
 * Calculates the squared length of a vec2
 *
 * @param {vec2} a vector to calculate squared length of
 * @returns {Number} squared length of a
 */
export function squaredLength (a) {
  var x = a[0],
    y = a[1];
  return x*x + y*y;
};

/**
 * Negates the components of a vec2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a vector to negate
 * @returns {vec2} out
 */
export function negate(out, a) {
  out[0] = -a[0];
  out[1] = -a[1];
  return out;
};

/**
 * Returns the inverse of the components of a vec2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a vector to invert
 * @returns {vec2} out
 */
export function inverse(out, a) {
  out[0] = 1.0 / a[0];
  out[1] = 1.0 / a[1];
  return out;
};

/**
 * Normalize a vec2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a vector to normalize
 * @returns {vec2} out
 */
export function normalize(out, a) {
  var x = a[0],
    y = a[1];
  var len = x*x + y*y;
  if (len > 0) {
    //TODO: evaluate use of glm_invsqrt here?
    len = 1 / Math.sqrt(len);
    out[0] = a[0] * len;
    out[1] = a[1] * len;
  }
  return out;
};

/**
 * Calculates the dot product of two vec2's
 *
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {Number} dot product of a and b
 */
export function dot(a, b) {
  return a[0] * b[0] + a[1] * b[1];
};

/**
 * Computes the cross product of two vec2's
 * Note that the cross product must by definition produce a 3D vector
 *
 * @param {vec3} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @returns {vec3} out
 */
export function cross(out, a, b) {
  var z = a[0] * b[1] - a[1] * b[0];
  out[0] = out[1] = 0;
  out[2] = z;
  return out;
};

/**
 * Performs a linear interpolation between two vec2's
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the first operand
 * @param {vec2} b the second operand
 * @param {Number} t interpolation amount between the two inputs
 * @returns {vec2} out
 */
export function lerp(out, a, b, t) {
  var ax = a[0],
    ay = a[1];
  out[0] = ax + t * (b[0] - ax);
  out[1] = ay + t * (b[1] - ay);
  return out;
};

/**
 * Generates a random vector with the given scale
 *
 * @param {vec2} out the receiving vector
 * @param {Number} [scale] Length of the resulting vector. If ommitted, a unit vector will be returned
 * @returns {vec2} out
 */
export function random(out, scale) {
  scale = scale || 1.0;
  var r = glMatrix.RANDOM() * 2.0 * Math.PI;
  out[0] = Math.cos(r) * scale;
  out[1] = Math.sin(r) * scale;
  return out;
};

/**
 * Transforms the vec2 with a mat2
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the vector to transform
 * @param {mat2} m matrix to transform with
 * @returns {vec2} out
 */
export function transformMat2(out, a, m) {
  var x = a[0],
    y = a[1];
  out[0] = m[0] * x + m[2] * y;
  out[1] = m[1] * x + m[3] * y;
  return out;
};

/**
 * Transforms the vec2 with a mat2d
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the vector to transform
 * @param {mat2d} m matrix to transform with
 * @returns {vec2} out
 */
export function transformMat2d(out, a, m) {
  var x = a[0],
    y = a[1];
  out[0] = m[0] * x + m[2] * y + m[4];
  out[1] = m[1] * x + m[3] * y + m[5];
  return out;
};

/**
 * Transforms the vec2 with a mat3
 * 3rd vector component is implicitly '1'
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the vector to transform
 * @param {mat3} m matrix to transform with
 * @returns {vec2} out
 */
export function transformMat3(out, a, m) {
  var x = a[0],
    y = a[1];
  out[0] = m[0] * x + m[3] * y + m[6];
  out[1] = m[1] * x + m[4] * y + m[7];
  return out;
};

/**
 * Transforms the vec2 with a mat4
 * 3rd vector component is implicitly '0'
 * 4th vector component is implicitly '1'
 *
 * @param {vec2} out the receiving vector
 * @param {vec2} a the vector to transform
 * @param {mat4} m matrix to transform with
 * @returns {vec2} out
 */
export function transformMat4(out, a, m) {
  let x = a[0];
  let y = a[1];
  out[0] = m[0] * x + m[4] * y + m[12];
  out[1] = m[1] * x + m[5] * y + m[13];
  return out;
}

/**
 * Returns a string representation of a vector
 *
 * @param {vec2} a vector to represent as a string
 * @returns {String} string representation of the vector
 */
export function str(a) {
  return 'vec2(' + a[0] + ', ' + a[1] + ')';
}

/**
 * Returns whether or not the vectors exactly have the same elements in the same position (when compared with ===)
 *
 * @param {vec2} a The first vector.
 * @param {vec2} b The second vector.
 * @returns {Boolean} True if the vectors are equal, false otherwise.
 */
export function exactEquals(a, b) {
  return a[0] === b[0] && a[1] === b[1];
}

/**
 * Returns whether or not the vectors have approximately the same elements in the same position.
 *
 * @param {vec2} a The first vector.
 * @param {vec2} b The second vector.
 * @returns {Boolean} True if the vectors are equal, false otherwise.
 */
export function equals(a, b) {
  let a0 = a[0], a1 = a[1];
  let b0 = b[0], b1 = b[1];
  return (Math.abs(a0 - b0) <= glMatrix.EPSILON*Math.max(1.0, Math.abs(a0), Math.abs(b0)) &&
          Math.abs(a1 - b1) <= glMatrix.EPSILON*Math.max(1.0, Math.abs(a1), Math.abs(b1)));
}

/**
 * Alias for {@link vec2.length}
 * @function
 */
export const len = length;

/**
 * Alias for {@link vec2.subtract}
 * @function
 */
export const sub = subtract;

/**
 * Alias for {@link vec2.multiply}
 * @function
 */
export const mul = multiply;

/**
 * Alias for {@link vec2.divide}
 * @function
 */
export const div = divide;

/**
 * Alias for {@link vec2.distance}
 * @function
 */
export const dist = distance;

/**
 * Alias for {@link vec2.squaredDistance}
 * @function
 */
export const sqrDist = squaredDistance;

/**
 * Alias for {@link vec2.squaredLength}
 * @function
 */
export const sqrLen = squaredLength;

/**
 * Perform some operation over an array of vec2s.
 *
 * @param {Array} a the array of vectors to iterate over
 * @param {Number} stride Number of elements between the start of each vec2. If 0 assumes tightly packed
 * @param {Number} offset Number of elements to skip at the beginning of the array
 * @param {Number} count Number of vec2s to iterate over. If 0 iterates over entire array
 * @param {Function} fn Function to call for each vector in the array
 * @param {Object} [arg] additional argument to pass to fn
 * @returns {Array} a
 * @function
 */
export const forEach = (function() {
  let vec = create();

  return function(a, stride, offset, count, fn, arg) {
    let i, l;
    if(!stride) {
      stride = 2;
    }

    if(!offset) {
      offset = 0;
    }

    if(count) {
      l = Math.min((count * stride) + offset, a.length);
    } else {
      l = a.length;
    }

    for(i = offset; i < l; i += stride) {
      vec[0] = a[i]; vec[1] = a[i+1];
      fn(vec, vec, arg);
      a[i] = vec[0]; a[i+1] = vec[1];
    }

    return a;
  };
})();
