index logic

gistfile1.js

  /*
    "crime":
    {
      "equals": "arson"
    }

    index -> specific index that references the property keyword
    query -> object containing the specific queries for the index
    set -> object containing keys of all of the id's matching currently

    callback -> object containing keys of all of the id's still matching:
    {
      1: true,
      23: true
    }

    TODO: add functionality for
    "crime":
    {
      "or": {
        "equals": "arson",
        "equals": "theft"
      }
    }
   */
  function eliminateForIndex(index, query, set, callback) {
    var queryKeys = Object.keys(query);
    var count = 0;

    for (var i = 0; i < queryKeys.length; i++) {
      if (typeof index[queryKeys[i]] !== "function") {
        callback("Index does not have a method matching " + queryKeys[i]);
        return;
      }

      index[queryKeys[i]](query[i], function (err, data) {
        count++;

        if (err) {
          callback(err);

          // short-circuit the scan, we hit an error. this is fatal.
          count = queryKeys.length;
          return;
        } else {
          var setKeys = Object.keys(set);
          for (var j = 0; j < setKeys.length; j++) {
            if (!data[setKeys[j]]) {
              delete set[setKeys[j]];
            }
          }
        }

        if (count === queryKeys.length) {
          callback(null, set);
        }
      });
    }
  }