_metadata.js

var Map     = require('./es6.map')
  , $export = require('./_export')
  , shared  = require('./_shared')('metadata')
  , store   = shared.store || (shared.store = new (require('./es6.weak-map')));

var getOrCreateMetadataMap = function(target, targetKey, create){
  var targetMetadata = store.get(target);
  if(!targetMetadata){
    if(!create)return undefined;
    store.set(target, targetMetadata = new Map);
  }
  var keyMetadata = targetMetadata.get(targetKey);
  if(!keyMetadata){
    if(!create)return undefined;
    targetMetadata.set(targetKey, keyMetadata = new Map);
  } return keyMetadata;
};
var ordinaryHasOwnMetadata = function(MetadataKey, O, P){
  var metadataMap = getOrCreateMetadataMap(O, P, false);
  return metadataMap === undefined ? false : metadataMap.has(MetadataKey);
};
var ordinaryGetOwnMetadata = function(MetadataKey, O, P){
  var metadataMap = getOrCreateMetadataMap(O, P, false);
  return metadataMap === undefined ? undefined : metadataMap.get(MetadataKey);
};
var ordinaryDefineOwnMetadata = function(MetadataKey, MetadataValue, O, P){
  getOrCreateMetadataMap(O, P, true).set(MetadataKey, MetadataValue);
};
var ordinaryOwnMetadataKeys = function(target, targetKey){
  var metadataMap = getOrCreateMetadataMap(target, targetKey, false)
    , keys        = [];
  if(metadataMap)metadataMap.forEach(function(_, key){ keys.push(key); });
  return keys;
};
var toMetaKey = function(it){
  return it === undefined || typeof it == 'symbol' ? it : String(it);
};
var exp = function(O){
  $export($export.S, 'Reflect', O);
};

module.exports = {
  store: store,
  map: getOrCreateMetadataMap,
  has: ordinaryHasOwnMetadata,
  get: ordinaryGetOwnMetadata,
  set: ordinaryDefineOwnMetadata,
  keys: ordinaryOwnMetadataKeys,
  key: toMetaKey,
  exp: exp
};