/*    Copyright (c) 2015 Mirantis, Inc.

 Licensed under the Apache License, Version 2.0 (the "License"); you may
 not use this file except in compliance with the License. You may obtain
 a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 License for the specific language governing permissions and limitations
 under the License.
 */
(function() {
  angular
    .module('merlin')
    /* 'extractPanels' filter requires one argument which should be a function.
    This function is applied to the top-level elements of the object and the
    fields for which it returns a numeric value are grouped into the panels. More
    precisely, each field yielding the same numeric value is put into the same panel.
    Subclasses of Barricade.Container which don't yield a numeric value (and return
    null, for example) become the entry points of a recursive application of above
    algorithm, so eventually each field will be either:
    * put into a panel (determinant returns numeric value)
    * recursively scanned for more fields (is a container, no numeric value returned)
    * or skipped completely (neither of above conditions is met).

    Each returned panel implements at least .each() method (iterating through all key &
    field pairs of a panel) which could be later consumed by 'extractFields' filter.
    Filter results are cached, with each field explicitly put into a panel by determinant
    (i.e. yielding a numeric value) adds its unique id to the caching key. This means that
    the filter returns a new set of panels if the set of fields explicitly put into panels
    changes - i.e. a value goes away or comes in into a set or replaced in place with
    another value (any case is tracked by the unique field id).
     */
    .filter('extractPanels', extractPanels)
    .filter('extractFields', extractFields)
    .filter('chunks', chunks);

  extractPanels.$inject = ['merlin.utils'];

  function extractPanels(utils) {
    var panelProto = {
      create: function(enumerator, obj, context) {
        this.$$obj = obj;
        this.$$enumerator = enumerator;
        this.removable = false;
        if (this.$$obj) {
          this.id = this.$$obj.uid();
          this.$$objParent = context.container;
          this.removable = this.$$objParent.instanceof(Barricade.Arraylike);
          if (this.$$objParent.instanceof(Barricade.MutableObject)) {
            this.title = function() {
              if ( arguments.length ) {
                obj.setID(arguments[0]);
              } else {
                return obj.getID();
              }
            };
          } else if (this.$$objParent.instanceof(Barricade.ImmutableObject)) {
            this.title = context.indexOrKey;
          }
        } else {
          var id = '';
          this.$$enumerator(function(key, item) {
            id += item.uid();
          });
          this.id = id;
        }
        return this;
      },
      each: function(callback, comparator) {
        this.$$enumerator.call(this.$$obj, callback, comparator);
      },
      remove: function() {
        var index;
        if (this.removable) {
          index = this.$$objParent.toArray().indexOf(this.$$obj);
          this.$$objParent.remove(index);
        }
      }
    };

    return _.memoize(function(container, keyExtractor) {
      var items = [];
      var _data = {};
      var panels = [];

      /* This function recursively applies determinant 'keyExtractor' function
      to each container (given that the determinant doesn't return a numeric
      value for it), starting from the top-level. Fields for which determinant
      returns a numeric value, will be later placed into a panels (see docs for
      'extractPanels' filter).
      */
      function rec(container) {
        container.each(function(indexOrKey, item) {
          var groupingKey = keyExtractor(item, container);
          if (angular.isNumber(groupingKey)) {
            items.push(item);
            _data[item.uid()] = {
              groupingKey: groupingKey,
              container: container,
              indexOrKey: indexOrKey
            };
          } else if (item.instanceof(Barricade.Container)) {
            rec(item);
          }
        });
      }
      // top-level entry-point of recursive descent
      rec(container);

      function extractKey(item) {
        return angular.isDefined(item) && _data[item.uid()].groupingKey;
      }

      utils.groupByExtractedKey(items, extractKey).forEach(function(items) {
        var parent, enumerator, obj, context;
        if (items.length > 1 || !items[0].instanceof(Barricade.Container)) {
          parent = _data[items[0].uid()].container;
          // the enumerator function mimicking the behavior of built-in .each()
          // method which aggregate panels do not have
          enumerator = function(callback) {
            items.forEach(function(item) {
              if (_data[item.uid()].container === parent) {
                callback(_data[item.uid()].indexOrKey, item);
              }
            });
          };
        } else {
          obj = items[0];
          enumerator = obj.each;
          context = _data[obj.uid()];
        }
        panels.push(Object.create(panelProto).create(enumerator, obj, context));
      });
      return utils.condense(panels);
    }, function(container, keyExtractor) {
      var hash = '';
      function rec(container) {
        container.each(function(indexOrKey, item) {
          var groupingKey = keyExtractor(item, container);
          if (angular.isNumber(groupingKey)) {
            hash += item.uid();
          } else if (item.instanceof(Barricade.Container)) {
            rec(item);
          }
        });
      }
      rec(container);
      return hash;
    });
  }

  function extractFields() {
    return _.memoize(function(container) {
      var fields = {};
      container.each(function(key, item) {
        fields[key] = item;
      });
      return fields;
    }, function(panel) {
      var hash = '';
      panel.each(function(key, item) {
        hash += item.uid();
      });
      return hash;
    });
  }

  function chunks() {
    return _.memoize(function(fields, itemsPerChunk) {
      var chunks = [];
      var keys = Object.keys(fields);
      var i, j, chunk;
      itemsPerChunk = +itemsPerChunk;
      if (!angular.isNumber(itemsPerChunk) || itemsPerChunk < 1) {
        return chunks;
      }
      for (i = 0; i < keys.length; i++) {
        chunk = {};
        for (j = 0; j < itemsPerChunk; j++) {
          chunk[keys[i]] = fields[keys[i]];
        }
        chunks.push(chunk);
      }
      return chunks;
    }, function(fields) {
      var hash = '';
      var key;
      for (key in fields) {
        if (fields.hasOwnProperty(key)) {
          hash += fields[key].uid();
        }
      }
      return hash;
    });
  }

})();