mekanika/query

module.exports = mixin;

/**
  Match operators
*/

var operators = [
  'eq',  // ===
  'is',  // Alias 'eq' (more fluent for non-numeric)
  'not', // Alias 'neq' (more fluent for non-numeric)
  'neq', // !==
  'in',  // has
  'nin', // !has
  'lt',  // <
  'gt',  // >
  'lte', // <=
  'gte', // >=
  'all', // has every (tags:['action','adventure'])
  'any'  // has any of {tags:['action','adventure']}
];

/**
  Mixin operators as methods on `target` that modify
*/

function mixin (target, loc) {
  if (!target) throw new Error('Must specify target');

  // Protects scope
  var each = function (arr, fn) {
    for (var i = 0; i < arr.length; i++) fn(arr[i]);
  };

  // Add each `operator` as a function on `target`
  each(operators, function (op) {
    target[ op ] = function (value) {
      // Normalise aliases
      if (op === 'is') op = 'eq';
      if (op === 'not') op = 'neq';

      // Enforce array entries for `in, nin, all`
      if (/in$|^all|^any/.test(op)) {
        if (!(value instanceof Array)) {
          throw new Error('Operator "' + op + '" requires value as array');
        }
      }

      // Get the most recent 'match' constraint
      // Where to look?
      var store = loc ? this.qe.match : this;
      if (!store) throw new Error('No Qe .match field setup');

      // All the `Object.keys(obj)[0]` references are simply trying
      // `object[ 0 ]`
      // Of course, that doesn't work. For objects with known key length of 1
      // we can list the keys as an array, and fetch the first one.
      // Convoluted perhaps, performant, no.
      // @todo Write a util to speed this up
      // @see http://jsperf.com/unknown-object-key

      var mos = store[ Object.keys(store)[0] ];

      var _renameSoloKey = function (obj, newKey) {
        var oldkey = Object.keys(obj)[0];
        obj[ newKey ] = obj[ oldkey ];
        delete obj[ oldkey ];
      };

      var lastmo = mos[ mos.length - 1 ];

      var mod = lastmo[ Object.keys(lastmo)[0] ];
      _renameSoloKey(mod, op);
      mod[op] = value;

      return this;
    };

  });
}