angular.module('mm.foundation.typeahead', ['mm.foundation.position', 'mm.foundation.bindHtml'])

/**
 * A helper service that can parse typeahead's syntax (string provided by users)
 * Extracted to a separate service for ease of unit testing
 */
  .factory('typeaheadParser', ['$parse', function ($parse) {

  //                      00000111000000000000022200000000000000003333333333333330000000000044000
  var TYPEAHEAD_REGEXP = /^\s*(.*?)(?:\s+as\s+(.*?))?\s+for\s+(?:([\$\w][\$\w\d]*))\s+in\s+(.*)$/;

  return {
    parse:function (input) {

      var match = input.match(TYPEAHEAD_REGEXP);
      if (! match) {
        throw new Error(
          "Expected typeahead specification in form of '_modelValue_ (as _label_)?  for _item_ in _collection_'" +
            " but got '" + input + "'."); 
      }

      return {
        itemName:match[3],
        source:$parse(match[4]),
        viewMapper:$parse(match[2] || match[1]),
        modelMapper:$parse(match[1])
      };
    }
  };
}])

  .directive('typeahead', ['$compile', '$parse', '$q', '$timeout', '$document', '$position', 'typeaheadParser',
    function ($compile, $parse, $q, $timeout, $document, $position, typeaheadParser) {

  var HOT_KEYS = [9, 13, 27, 38, 40];

  return {
    require:'ngModel',
    link:function (originalScope, element, attrs, modelCtrl) {

      //SUPPORTED ATTRIBUTES (OPTIONS)

      //minimal no of characters that needs to be entered before typeahead kicks-in
      var minSearch = originalScope.$eval(attrs.typeaheadMinLength) || 1;

      //minimal wait time after last character typed before typehead kicks-in
      var waitTime = originalScope.$eval(attrs.typeaheadWaitMs) || 0;

      //should it restrict model values to the ones selected from the popup only? 
      var isEditable = originalScope.$eval(attrs.typeaheadEditable) ! == false;

      //binding to a variable that indicates if matches are being retrieved asynchronously
      var isLoadingSetter = $parse(attrs.typeaheadLoading).assign || angular.noop;

      //a callback executed when a match is selected
      var onSelectCallback = $parse(attrs.typeaheadOnSelect);

      var inputFormatter = attrs.typeaheadInputFormatter ?  $parse(attrs.typeaheadInputFormatter) : undefined;

      var appendToBody =  attrs.typeaheadAppendToBody ?  $parse(attrs.typeaheadAppendToBody) : false;

      var focusFirst = originalScope.$eval(attrs.typeaheadFocusFirst) ! == false;

      //INTERNAL VARIABLES

      //model setter executed upon match selection
      var $setModelValue = $parse(attrs.ngModel).assign;

      //expressions used by typeahead
      var parserResult = typeaheadParser.parse(attrs.typeahead);

      var hasFocus;

      //pop-up element used to display matches
      var popUpEl = angular.element('<div typeahead-popup></div>');
      popUpEl.attr({
        matches: 'matches',
        active: 'activeIdx',
        select: 'select(activeIdx)',
        query: 'query',
        position: 'position'
      });
      //custom item template
      if (angular.isDefined(attrs.typeaheadTemplateUrl)) {
        popUpEl.attr('template-url', attrs.typeaheadTemplateUrl);
      }

      //create a child scope for the typeahead directive so we are not polluting original scope
      //with typeahead-specific data (matches, query etc.) 
      var scope = originalScope.$new();
      originalScope.$on('$destroy', function(){
        scope.$destroy();
      });

      var resetMatches = function() {
        scope.matches = [];
        scope.activeIdx = -1;
      };

      var getMatchesAsync = function(inputValue) {

        var locals = {$viewValue: inputValue};
        isLoadingSetter(originalScope, true);
        $q.when(parserResult.source(originalScope, locals)).then(function(matches) {

          //it might happen that several async queries were in progress if a user were typing fast
          //but we are interested only in responses that correspond to the current view value
          if (inputValue === modelCtrl.$viewValue && hasFocus) {
            if (matches.length > 0) {

              scope.activeIdx = focusFirst ?  0 : -1;
              scope.matches.length = 0;

              //transform labels
              for(var i=0; i<matches.length; i++) {
                locals[parserResult.itemName] = matches[i];
                scope.matches.push({
                  label: parserResult.viewMapper(scope, locals),
                  model: matches[i]
                });
              }

              scope.query = inputValue;
              //position pop-up with matches - we need to re-calculate its position each time we are opening a window
              //with matches as a pop-up might be absolute-positioned and position of an input might have changed on a page
              //due to other elements being rendered
              scope.position = appendToBody ?  $position.offset(element) : $position.position(element);
              scope.position.top = scope.position.top + element.prop('offsetHeight');

            } else {
              resetMatches();
            }
          }
        }, function(){
          resetMatches();
        }).finally(function() {
          isLoadingSetter(originalScope, false);
        });
      };

      resetMatches();

      //we need to propagate user's query so we can higlight matches
      scope.query = undefined;

      //Declare the timeout promise var outside the function scope so that stacked calls can be cancelled later
      var timeoutPromise;

      //plug into $parsers pipeline to open a typeahead on view changes initiated from DOM
      //$parsers kick-in on all the changes coming from the view as well as manually triggered by $setViewValue
      modelCtrl.$parsers.unshift(function (inputValue) {

        if (inputValue && inputValue.length >= minSearch) {
          if (waitTime > 0) {
            if (timeoutPromise) {
              $timeout.cancel(timeoutPromise);//cancel previous timeout
            }
            timeoutPromise = $timeout(function () {
              getMatchesAsync(inputValue);
            }, waitTime);
          } else {
            getMatchesAsync(inputValue);
          }
        } else {
          isLoadingSetter(originalScope, false);
          resetMatches();
        }

        if (isEditable) {
          return inputValue;
        } else {
          if (! inputValue) {
            // Reset in case user had typed something previously. 
            modelCtrl.$setValidity('editable', true);
            return inputValue;
          } else {
            modelCtrl.$setValidity('editable', false);
            return undefined;
          }
        }
      });

      modelCtrl.$formatters.push(function (modelValue) {

        var candidateViewValue, emptyViewValue;
        var locals = {};

        if (inputFormatter) {

          locals['$model'] = modelValue;
          return inputFormatter(originalScope, locals);

        } else {

          //it might happen that we don't have enough info to properly render input value
          //we need to check for this situation and simply return model value if we can't apply custom formatting
          locals[parserResult.itemName] = modelValue;
          candidateViewValue = parserResult.viewMapper(originalScope, locals);
          locals[parserResult.itemName] = undefined;
          emptyViewValue = parserResult.viewMapper(originalScope, locals);

          return candidateViewValue!== emptyViewValue ?  candidateViewValue : modelValue;
        }
      });

      scope.select = function (activeIdx) {
        //called from within the $digest() cycle
        var locals = {};
        var model, item;

        locals[parserResult.itemName] = item = scope.matches[activeIdx].model;
        model = parserResult.modelMapper(originalScope, locals);
        $setModelValue(originalScope, model);
        modelCtrl.$setValidity('editable', true);

        onSelectCallback(originalScope, {
          $item: item,
          $model: model,
          $label: parserResult.viewMapper(originalScope, locals)
        });

        resetMatches();

        //return focus to the input element if a mach was selected via a mouse click event
        element[0].focus();
      };

      //bind keyboard events: arrows up(38) / down(40), enter(13) and tab(9), esc(27)
      element.bind('keydown', function (evt) {

        //typeahead is open and an "interesting" key was pressed
        if (scope.matches.length === 0 || HOT_KEYS.indexOf(evt.which) === -1) {
          return;
        }

        // if there's nothing selected (i.e. focusFirst) and enter is hit, don't do anything
        if (scope.activeIdx == -1 && (evt.which === 13 || evt.which === 9)) {
          return;
        }

        evt.preventDefault();

        if (evt.which === 40) {
          scope.activeIdx = (scope.activeIdx + 1) % scope.matches.length;
          scope.$digest();

        } else if (evt.which === 38) {
          scope.activeIdx = (scope.activeIdx > 0 ?  scope.activeIdx : scope.matches.length) - 1;
          scope.$digest();

        } else if (evt.which === 13 || evt.which === 9) {
          scope.$apply(function () {
            scope.select(scope.activeIdx);
          });

        } else if (evt.which === 27) {
          evt.stopPropagation();

          resetMatches();
          scope.$digest();
        }
      });

      element.bind('blur', function (evt) {
        hasFocus = false;
      });

      element.bind('focus', function (evt) {
        hasFocus = true;
      });

      // Keep reference to click handler to unbind it. 
      var dismissClickHandler = function (evt) {
        if (element[0] ! == evt.target) {
          resetMatches();
          scope.$digest();
        }
      };

      $document.bind('click', dismissClickHandler);

      originalScope.$on('$destroy', function(){
        $document.unbind('click', dismissClickHandler);
      });

      var $popup = $compile(popUpEl)(scope);
      if ( appendToBody ) {
        $document.find('body').append($popup);
      } else {
        element.after($popup);
      }
    }
  };

}])

  .directive('typeaheadPopup', function () {
    return {
      restrict:'EA',
      scope:{
        matches:'=',
        query:'=',
        active:'=',
        position:'=',
        select:'&'
      },
      replace:true,
      templateUrl:'template/typeahead/typeahead-popup.html',
      link:function (scope, element, attrs) {

        scope.templateUrl = attrs.templateUrl;

        scope.isOpen = function () {
          return scope.matches.length > 0;
        };

        scope.isActive = function (matchIdx) {
          return scope.active == matchIdx;
        };

        scope.selectActive = function (matchIdx) {
          scope.active = matchIdx;
        };

        scope.selectMatch = function (activeIdx) {
          scope.select({activeIdx:activeIdx});
        };
      }
    };
  })

  .directive('typeaheadMatch', ['$http', '$templateCache', '$compile', '$parse', function ($http, $templateCache, $compile, $parse) {
    return {
      restrict:'EA',
      scope:{
        index:'=',
        match:'=',
        query:'='
      },
      link:function (scope, element, attrs) {
        var tplUrl = $parse(attrs.templateUrl)(scope.$parent) || 'template/typeahead/typeahead-match.html';
        $http.get(tplUrl, {cache: $templateCache}).success(function(tplContent){
           element.replaceWith($compile(tplContent.trim())(scope));
        });
      }
    };
  }])

  .filter('typeaheadHighlight', function() {

    function escapeRegexp(queryToEscape) {
      return queryToEscape.replace(/([.?*+^$[\]\\(){}|-])/g, "\\$1");
    }

    return function(matchItem, query) {
      return query ?  matchItem.replace(new RegExp(escapeRegexp(query), 'gi'), '<strong>$&</strong>') : matchItem;
    };
  });
