var error = require('../../util/error.js'),
    collection = require('../../type/collection.js'),
    array = require('../../util/array.js'),
    Matrix = require('../../type/Matrix.js');

/**
 * Compute the minimum value of a list of values
 *
 *     min(a, b, c, ...)
 *     min([a, b, c, ...])
 *
 * @param {... *} args  A single matrix or multiple scalars
 * @return {*} res
 */
module.exports = function min(args) {
  if (arguments.length == 0) {
    throw new Error('Function min requires one or more parameters (0 provided)');
  }

  if (collection.isCollection(args)) {
    // min([a, b, c, d, ...]])
    if (arguments.length > 1) {
      throw Error('Wrong number of parameters (1 matrix or multiple scalars expected)');
    }

    var size = array.size(args.valueOf());

    if (size.length == 1) {
      // vector
      if (args.length == 0) {
        throw new Error('Cannot calculate min of an empty vector');
      }

      return _min(args.valueOf());
    }
    else if (size.length == 2) {
      // 2 dimensional matrix
      if (size[0] == 0 || size[1] == 0) {
        throw new Error('Cannot calculate min of an empty matrix');
      }

      // TODO: make a generic collection method for this
      if (Matrix.isMatrix(args)) {
        return new Matrix(_min2(args.valueOf(), size[0], size[1]));
      }
      else {
        return _min2(args, size[0], size[1]);
      }
    }
    else {
      // TODO: implement min for n-dimensional matrices
      throw new RangeError('Cannot calculate min for multi dimensional matrix');
    }
  }
  else {
    // min(a, b, c, d, ...)
    return _min(arguments);
  }
};

/**
 * Calculate the min of a one dimensional array
 * @param {Array} array
 * @return {Number} min
 * @private
 */
function _min(array) {
  var res = array[0];
  for (var i = 1, iMax = array.length; i < iMax; i++) {
    var value = array[i];
    if (smaller(value, res)) {
      res = value;
    }
  }
  return res;
}

/**
 * Calculate the min of a two dimensional array
 * @param {Array} array
 * @param {Number} rows
 * @param {Number} cols
 * @return {Number[]} min
 * @private
 */
function _min2(array, rows, cols) {
  var res = [];
  for (var c = 0; c < cols; c++) {
    var min = array[0][c];
    for (var r = 1; r < rows; r++) {
      var value = array[r][c];
      if (smaller(value, min)) {
        min = value;
      }
    }
    res[c] = min;
  }
  return res;
}

// require after module.exports because of possible circular references
var smaller = require('../arithmetic/smaller.js');