(function (factory) {
  'use strict';
  if (typeof define === 'function' && define.amd) {
    // AMD. Register as an anonymous module.
    define(['angular', 'chart.js'], factory);
  } else if (typeof exports === 'object') {
    // Node/CommonJS
    module.exports = factory(require('angular'), require('chart.js'));
  } else {
    // Browser globals
    factory(angular, Chart);
  }
}(function (angular, Chart) {
  'use strict';

  Chart.defaults.global.responsive = true;
  Chart.defaults.global.multiTooltipTemplate = '<%if (datasetLabel){%><%=datasetLabel%>: <%}%><%= value %>';

  Chart.defaults.global.colours = [
    '#97BBCD', // blue
    '#DCDCDC', // light grey
    '#F7464A', // red
    '#46BFBD', // green
    '#FDB45C', // yellow
    '#949FB1', // grey
    '#4D5360'  // dark grey
  ];

  angular.module('chart.js', [])
    .provider('ChartJs', ChartJsProvider)
    .factory('ChartJsFactory', ['ChartJs', ChartJsFactory])
    .directive('chartBase', function (ChartJsFactory) { return new ChartJsFactory(); })
    .directive('chartLine', function (ChartJsFactory) { return new ChartJsFactory('Line'); })
    .directive('chartBar', function (ChartJsFactory) { return new ChartJsFactory('Bar'); })
    .directive('chartRadar', function (ChartJsFactory) { return new ChartJsFactory('Radar'); })
    .directive('chartDoughnut', function (ChartJsFactory) { return new ChartJsFactory('Doughnut'); })
    .directive('chartPie', function (ChartJsFactory) { return new ChartJsFactory('Pie'); })
    .directive('chartPolarArea', function (ChartJsFactory) { return new ChartJsFactory('PolarArea'); });

  /**
   * Wrapper for chart.js
   * Allows configuring chart js using the provider
   *
   * angular.module('myModule', ['chart.js']).config(function(ChartJsProvider) {
   *   ChartJsProvider.setOptions({ responsive: true });
   *   ChartJsProvider.setOptions('Line', { responsive: false });
   * })))
   */
  function ChartJsProvider () {
    var options = {};
    var ChartJs = {
      Chart: Chart,
      getOptions: function (type) {
        var typeOptions = type && options[type] || {};
        return angular.extend({}, options, typeOptions);
      }
    };

    /**
     * Allow to set global options during configuration
     */
    this.setOptions = function (type, customOptions) {
      // If no type was specified set option for the global object
      if (! customOptions) {
        customOptions = type;
        options = angular.extend(options, customOptions);
        return;
      }
      // Set options for the specific chart
      options[type] = angular.extend(options[type] || {}, customOptions);
    };

    this.$get = function () {
      return ChartJs;
    };
  }

  function ChartJsFactory (ChartJs) {
    return function chart (type) {
      return {
        restrict: 'CA',
        scope: {
          data: '=',
          labels: '=',
          options: '=',
          series: '=',
          colours: '=?',
          getColour: '=?',
          chartType: '=',
          legend: '@',
          click: '=',
          hover: '='
        },
        link: function (scope, elem/*, attrs */) {
          var chart, container = document.createElement('div');
          container.className = 'chart-container';
          elem.replaceWith(container);
          container.appendChild(elem[0]);

          if (typeof window.G_vmlCanvasManager === 'object' && window.G_vmlCanvasManager !== null) {
            if (typeof window.G_vmlCanvasManager.initElement === 'function') {
              window.G_vmlCanvasManager.initElement(elem[0]);
            }
          }

          // Order of setting "watch" matter

          scope.$watch('data', function (newVal, oldVal) {
            if (! newVal || ! newVal.length || (Array.isArray(newVal[0]) && ! newVal[0].length)) return;
            var chartType = type || scope.chartType;
            if (! chartType) return;

            if (chart) {
              if (canUpdateChart(newVal, oldVal)) return updateChart(chart, newVal, scope);
              chart.destroy();
            }

            chart = createChart(chartType, scope, elem);
          }, true);

          scope.$watch('series', resetChart, true);
          scope.$watch('labels', resetChart, true);
          scope.$watch('options', resetChart, true);
          scope.$watch('colours', resetChart, true);

          scope.$watch('chartType', function (newVal, oldVal) {
            if (isEmpty(newVal)) return;
            if (angular.equals(newVal, oldVal)) return;
            if (chart) chart.destroy();
            chart = createChart(newVal, scope, elem);
          });

          scope.$on('$destroy', function () {
            if (chart) chart.destroy();
          });

          function resetChart (newVal, oldVal) {
            if (isEmpty(newVal)) return;
            if (angular.equals(newVal, oldVal)) return;
            var chartType = type || scope.chartType;
            if (! chartType) return;

            // chart.update() doesn't work for series and labels
            // so we have to re-create the chart entirely
            if (chart) chart.destroy();

            chart = createChart(chartType, scope, elem);
          }
        }
      };
    };

    function canUpdateChart (newVal, oldVal) {
      if (newVal && oldVal && newVal.length && oldVal.length) {
        return Array.isArray(newVal[0]) ?
        newVal.length === oldVal.length && newVal[0].length === oldVal[0].length :
          oldVal.reduce(sum, 0) > 0 ? newVal.length === oldVal.length : false;
      }
      return false;
    }

    function sum (carry, val) {
      return carry + val;
    }

    function createChart (type, scope, elem) {
      if (! scope.data || ! scope.data.length) return;
      scope.getColour = typeof scope.getColour === 'function' ? scope.getColour : getRandomColour;
      scope.colours = getColours(type, scope);
      var cvs = elem[0], ctx = cvs.getContext('2d');
      var data = Array.isArray(scope.data[0]) ?
        getDataSets(scope.labels, scope.data, scope.series || [], scope.colours) :
        getData(scope.labels, scope.data, scope.colours);
      var options = angular.extend({}, ChartJs.getOptions(type), scope.options);
      var chart = new ChartJs.Chart(ctx)[type](data, options);
      scope.$emit('create', chart);

      ['hover', 'click'].forEach(function (action) {
        if (scope[action]) cvs[action === 'click' ? 'onclick' : 'onmousemove'] = getEventHandler(scope, chart, action);
      });
      if (scope.legend && scope.legend !== 'false') setLegend(elem, chart);
      return chart;
    }

    function getEventHandler (scope, chart, action) {
      return function (evt) {
        var atEvent = chart.getPointsAtEvent || chart.getBarsAtEvent || chart.getSegmentsAtEvent;
        if (atEvent) {
          var activePoints = atEvent.call(chart, evt);
          scope[action](activePoints, evt);
          scope.$apply();
        }
      };
    }

    function getColours (type, scope) {
      var colours = angular.copy(scope.colours ||
        ChartJs.getOptions(type).colours ||
        Chart.defaults.global.colours
      );
      while (colours.length < scope.data.length) {
        colours.push(scope.getColour());
      }
      return colours.map(convertColour);
    }

    function convertColour (colour) {
      if (typeof colour === 'object' && colour !== null) return colour;
      if (typeof colour === 'string' && colour[0] === '#') return getColour(hexToRgb(colour.substr(1)));
      return getRandomColour();
    }

    function getRandomColour () {
      var colour = [getRandomInt(0, 255), getRandomInt(0, 255), getRandomInt(0, 255)];
      return getColour(colour);
    }

    function getColour (colour) {
      return {
        fillColor: rgba(colour, 0.2),
        strokeColor: rgba(colour, 1),
        pointColor: rgba(colour, 1),
        pointStrokeColor: '#fff',
        pointHighlightFill: '#fff',
        pointHighlightStroke: rgba(colour, 0.8)
      };
    }

    function getRandomInt (min, max) {
      return Math.floor(Math.random() * (max - min + 1)) + min;
    }

    function rgba (colour, alpha) {
      return 'rgba(' + colour.concat(alpha).join(',') + ')';
    }

    // Credit: http://stackoverflow.com/a/11508164/1190235
    function hexToRgb (hex) {
      var bigint = parseInt(hex, 16),
        r = (bigint >> 16) & 255,
        g = (bigint >> 8) & 255,
        b = bigint & 255;

      return [r, g, b];
    }

    function getDataSets (labels, data, series, colours) {
      return {
        labels: labels,
        datasets: data.map(function (item, i) {
          return angular.extend({}, colours[i], {
            label: series[i],
            data: item
          });
        })
      };
    }

    function getData (labels, data, colours) {
      return labels.map(function (label, i) {
        return angular.extend({}, colours[i], {
          label: label,
          value: data[i],
          color: colours[i].strokeColor,
          highlight: colours[i].pointHighlightStroke
        });
      });
    }

    function setLegend (elem, chart) {
      var $parent = elem.parent(),
          $oldLegend = $parent.find('chart-legend'),
          legend = '<chart-legend>' + chart.generateLegend() + '</chart-legend>';
      if ($oldLegend.length) $oldLegend.replaceWith(legend);
      else $parent.append(legend);
    }

    function updateChart (chart, values, scope) {
      if (Array.isArray(scope.data[0])) {
        chart.datasets.forEach(function (dataset, i) {
          (dataset.points || dataset.bars).forEach(function (dataItem, j) {
            dataItem.value = values[i][j];
          });
        });
      } else {
        chart.segments.forEach(function (segment, i) {
          segment.value = values[i];
        });
      }
      chart.update();
      scope.$emit('update', chart);
    }

    function isEmpty (value) {
      return ! value ||
        (Array.isArray(value) && ! value.length) ||
        (typeof value === 'object' && ! Object.keys(value).length);
    }

  }
}));