/*global define */
define(['jquery', 'underscore', 'backbone', 'd3'],
    function($, _, Backbone, d3) {
    'use strict';

    /**
    * @class MetricsChartView
    * @classdesc The MetricsChartView will render an SVG times-series chart using D3 that shows the number of metrics over time.
    * @screenshot views/MetricsChartView.png
    * @classcategory Views
    */
    var MetricsChartView = Backbone.View.extend(
      /** @lends MetricsChartView.prototype */{

        initialize: function (options) {

            if(!d3){ console.log('SVG is not supported'); return null; }

            if(typeof options !== "undefined"){

            this.model        = options.model         || null;    // TODO: figure out how to set the model on this view

            this.metricCount  = options.metricCount   || "0";     // for now, use individual arrays
            this.metricMonths = options.metricMonths  || "0";
            this.id           = options.id            || "metrics-chart";
            this.viewType     = options.type          || "dataset";
            this.width        = options.width         || 600;
            this.height       = options.height        || 370;
            this.metricName   = options.metricName;

        }
      },

        // http://stackoverflow.com/questions/9651167/svg-not-rendering-properly-as-a-backbone-view
        // Give our el a svg namespace because Backbone gives a different one automatically
        nameSpace: "http://www.w3.org/2000/svg",
        _ensureElement: function() {
           if (!this.el) {
              var attrs = _.extend({}, _.result(this, 'attributes'));
              if (this.id) attrs.id = _.result(this, 'id');
              if (this.className) attrs['class'] = _.result(this, 'className');
              var $el = $(window.document.createElementNS(_.result(this, 'nameSpace'), _.result(this, 'tagName'))).attr(attrs);
              this.setElement($el, false);
           } else {
              this.setElement(_.result(this, 'el'), false);
           }
       },

       tagName: "svg",

      /** Renders this Metric Chart view. */
      render: function(){

        //Clear out any view elements in case this is a re-render
        this.$el.empty();

          /*
          * ========================================================================
          *  NAMING CONVENTIONS:

          CONTEXT: Context refers to the mini slider chart at the bottom, that includes the d3 "brush"
          FOCUS: Focus refers to the larger main chart at the top
          BRUSH: The rectangle in the context chart that highlights what is currently in focus in the focus chart.

          * ========================================================================
          */

          // check if there have been any views/citations
          var sumMetricCount = 0;
          for (var i = 0; i < this.metricCount.length; i++) {
              sumMetricCount += this.metricCount[i]
          }

          var self = this;

          // when ther no data or no views/citations yet, just show some text:
          if(this.metricCount.length == 0 || this.metricCount == 0 || sumMetricCount ==0){

              var metricNameLemma = this.metricName.toLowerCase().substring(0, this.metricName.length - 1);
              var textMessage = "This dataset hasn’t been " + metricNameLemma + "ed yet."
              if (this.viewType != "dataset") {
                  textMessage = "These datasets have not been " + metricNameLemma + "ed yet."
              }

              var margin	= {top: 25, right: 40, bottom: 40, left: 40},
                  height	= this.height - margin.top - margin.bottom;

              //Set the chart width
              this.$el.css("width", "100%");
              var width = (this.$el.width() || this.width) - margin.left - margin.right;
              this.width = width;

              var vis = d3.select(this.el)
                  .attr("width", width + margin.left + margin.right)
                  .attr("height", height + margin.top + margin.bottom)
                	.attr("class", "line-chart no-data");

              var bkg = vis.append("svg:rect")
                  .attr("class", "no-data")
                  .attr("width", width)
                  .attr("height", height)
                  .attr("rx", 2)
                  .attr("ry", 2)
                  .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

              var msg = vis.append("text")
                  .attr("class", "no-data")
                  .text(textMessage)
                  .attr("text-anchor", "middle")
                  .attr("font-size", "20px")
                  .attr("x", width/2)
                  .attr("y", height/2)
                  .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

          // if there is data (even a series of zeros), draw the time-series chart:
      } else {

          /*
          * ========================================================================
          *  Global variables and options
          * ========================================================================
          */

          var metricName = this.metricName;

          // the format of the date in the input data
          var input_date_format 	  =		d3.time.format("%Y-%m");
          // how dates will be displayed in the chart in most cases
          var display_date_format	  = 	d3.time.format("%b %Y");

          // the length of a day/year in milliseconds
          var day_in_ms = 86400000,
          	year_in_ms = 31540000000;

          // focus chart sizing
          var margin	= {top: 30, right: 30, bottom: 95, left: 20},
              height	= this.height - margin.top - margin.bottom;

          //Set the chart width
          this.$el.css("width", "100%");
          var width = (this.$el.width() || this.width) - margin.left - margin.right;
          this.width = width;

          // context chart sizing
          var margin_context = {top: 315, right: 30, bottom: 20, left: 20},
              height_context = this.height - margin_context.top - margin_context.bottom;

          // zoom button sizing
          var button_width = 40,
          	button_height = 14,
          	button_padding = 10;

          // how wide does the tooltip div need to be to accomdate text?
          var tooltip_width = 76;

          // what proportion of a month should a bar cover?
          var bar_width_factor = 0.8;

          /*
          * ========================================================================
          *  Prepare data
          * ========================================================================
          */

          // change dates to milliseconds, to enable calculating the `d3.extent`
          var metricMonths_parsed = [];
          this.metricMonths.forEach(function(part, index, theArray) {

              try {
                  metricMonths_parsed[index] = input_date_format.parse(part).getTime();
              }
              catch {
                  // replace null with current month
                  var today = new Date();
                  var yyyy = today.getFullYear();
                  var mm = today.getMonth() + 1;
                  var updatedPart = yyyy.toString() + "-" + (mm.toString()).padStart(2, '0');

                  metricMonths_parsed[index] = input_date_format.parse(updatedPart).getTime();
              }

          });

          // input data from model doesn't list months where there were 0 counts for all metrics (views/downloads/citations)
          // construct an array of all months between min and max dates to use as x variable
          var all_months = d3.time.scale()
          				.domain(d3.extent(metricMonths_parsed))
                          .ticks(d3.time.months, 1);

          // add padding to both sides of array so that bars don't get cut off.
          // add more padding when there's just one bar (otherwise it's too wide)
          if (metricMonths_parsed.length == 1) {
              var new_min_date = new Date(d3.extent(metricMonths_parsed)[0] - day_in_ms*13),
                  new_max_date = new Date(d3.extent(metricMonths_parsed)[1] + day_in_ms*31*bar_width_factor + day_in_ms*13);
          } else {
              var new_min_date = new Date(d3.extent(metricMonths_parsed)[0] - day_in_ms*1),
                  new_max_date = new Date(d3.extent(metricMonths_parsed)[1] + day_in_ms*31*bar_width_factor);
          };

          all_months.push(new_min_date);
          // also add a little padding on the left for consistency
          all_months.push(new_max_date);

          // for each month, check whether there is a count available,
          // if so append it, otherwise append zero.
          var dataset = [];
          for(var i=0; i<all_months.length; i++){
          	var match_index = metricMonths_parsed.indexOf(all_months[i].getTime());
          	if (match_index == -1) { // no match in data
          		dataset.push({integer: i, month: all_months[i], count:0});
          	} else { // match in data
          		dataset.push({integer: i, month: all_months[i], count:this.metricCount[match_index]});
          	}
          };

          /*
          * ========================================================================
          *  x and y coordinates
          * ========================================================================
          */

          var x_full_extent = d3.extent(dataset, function(d) { return d.month; });
          var bar_width = ((day_in_ms*30)/(x_full_extent[1]-x_full_extent[0])) * width * bar_width_factor;

          /* === Focus Chart === */

          var x = d3.time.scale()
              .range([0,width])
              .domain(d3.extent(dataset, function(d) { return d.month; }));

          var y = d3.scale.linear()
          	.range([height, 0])
              .domain([0, d3.max(dataset, function(d) { return d.count; })*1.04]);

          var x_axis = d3.svg.axis()
          	.scale(x)
              .orient("bottom")
          	.tickSize(-(height))
              .ticks(generate_ticks)
          	.tickFormat(format_months);

          var y_axis = d3.svg.axis()
          	.scale(y)
              .ticks(4)
          	.tickFormat(d3.format("d"))
              .tickSize(-(width))
          	.orient("right");

          /* === Context Chart === */

          var x_context = d3.time.scale()
              .range([0, width])
              .domain(d3.extent(dataset, function(d) { return d.month; }));

          var y_context = d3.scale.linear()
          	.range([height_context, 0])
              .domain(y.domain());

          var x_axis_context = d3.svg.axis()
              .scale(x_context)
              .orient("bottom")
              .ticks(generate_ticks)
              .tickFormat(format_months);

          /*
          * ========================================================================
          *  Variables for brushing and zooming behaviour
          * ========================================================================
          */

          var brush = d3.svg.brush()
              .x(x_context)
              .on("brush", change_focus_brush)
              .on("brushend", check_bounds);

          var zoom = d3.behavior.zoom()
              .on("zoom", change_focus_zoom)
              .on("zoomend", check_bounds);

          /*
          * ========================================================================
          *  Define the SVG area ("vis") and append all the layers
          * ========================================================================
          */

          // === the main components === //

          var vis = d3.select(this.el)
              .attr("width", width + margin.left + margin.right)
              .attr("height", height + margin.top + margin.bottom)
            	.attr("class", "line-chart");

          // clipPath is used to keep elements from moving outside of plot area when viwer zooms/scrolls/brushes
          vis.append("defs").append("clipPath")
              .attr("id", "clip")
              .append("rect")
              .attr("width", width)
              .attr("height", height);

          var pane = vis.append("rect")
              .attr("class", "pane")
              .attr("width", width)
              .attr("height", height)
              .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

          var context = vis.append("g")
              .attr("class", "context")
              .attr("transform", "translate(" + margin_context.left + "," + margin_context.top + ")");

          var focus = vis.append("g")
              .attr("class", "focus")
              .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

          // === current date range text & zoom buttons === //

          var expl_text = vis.append("g")
              .attr("id", "buttons_group")
              .attr("transform", "translate(" + 0 + ","+ 0 +")");

          expl_text.append("text")
          	.attr("id", "totalCount")
              .style("text-anchor", "start")
              .attr("transform", "translate(" + 18 + ","+ 11 +")");

          expl_text.append("text")
              .attr("id", "displayDates")
              .style("text-anchor", "start")
              .attr("transform", "translate(" + 20 + ","+ 22 +")");

          update_context();

          // === the zooming/scaling buttons === //

          if ((x_full_extent[1] - x_full_extent[0]) < year_in_ms) {
              var button_data =["month","all"];
          } else {
             var button_data =["year","month","all"];
          };

          var button_count	 = button_data.length -1,
          	button_g_width	 =	(button_count*button_width) +
          						(button_count*button_padding) +
          						margin.right - button_padding;

          expl_text.append("text")
          	.attr("class", "zoomto_text")
              .text("Zoom to")
              .style("text-anchor", "start")
              .attr("transform", "translate(" + (width - button_g_width - 45) + ","+ 14 +")")
          	.style("opacity", "0");

          var button = expl_text.selectAll("g")
              .data(button_data)
              .enter().append("g")
              .attr("class", "scale_button")
              .attr("transform", function(d, i) { return "translate(" + ((width - button_g_width) + i*button_width + i*button_padding) + ",4)"; })
          	.style("opacity", "0");

          button.append("rect")
          	.attr("class", "button_rect")
          	.attr("width", button_width)
          	.attr("height", button_height)
              .attr("rx", 1)
              .attr("ry", 1);

          button.append("text")
              .attr("dy", (button_height/2 + 3))
              .attr("dx", button_width/2)
              .style("text-anchor", "middle")
              .text(function(d) { return d; });

          /* === focus chart === */

          focus.append("g")
              .attr("class", "y axis")
              .call(y_axis)
             	.attr("transform", "translate(" + (width) + ", 0)")
          	.style("text-anchor", "middle");

          // x-axis
          focus.append("g")
              .attr("class", "x axis")
              .attr("transform", "translate(0," + height + ")")
              .call(x_axis)
          	.style("text-anchor", "middle");

          // enter bars
          focus.selectAll(".bar")
          	.data(dataset)
          	.enter().append("rect")
          	  		.attr("class", "bar")
          			  .attr("id", function(d){return "bar_" + d.month.getTime()}) //id of each bar is "bar_" plus it's associated date in ms
          	  		.attr("x", function (d) {return x(d.month); })
          	  		.attr("y", height)
          	  		.attr("height", 0)
          	  		.attr("width", bar_width)
          			.style("opacity", 0)
          			.on("mouseover", function(d) {
          				var floor_month = d3.time.month.floor(d.month).getTime();
          				highlight_bar("#bar_" + floor_month);
          				highlight_label("#label_" + floor_month);
          				show_tooltip(d);
          			})
          			.on("mouseout", function(d) {
          				var floor_month = d3.time.month.floor(d.month).getTime();
          				unhighlight_bar("#bar_" + floor_month);
          				unhighlight_label("#label_" + floor_month);
          				hide_tooltip(d);
          			});

          // animate bars
          focus.selectAll(".bar")
          	.transition()
          	.duration(450)
          	.ease("elastic", 1.03, 0.98)
          	.delay(function(d, i) {
          		var max_delay = 600;
          		var z = i / (dataset.length-1);
          		var line_z =  z * max_delay * 0.4;
          		var log_z = Math.log2(z + 1) * max_delay * 0.6;
          		return(250+line_z + log_z);
          	})
          	.attr("y", function (d) {return y(d.count);	  		})
          	.attr("height", function (d) {return y(0) - y(d.count);	  		})
          	.style("opacity", 1);

          /* === context chart === */

          // enter context bars
          context.selectAll(".bar_context")
          	.data(dataset)
          	.enter().append("rect")
          	  		.attr("class", "bar_context")
          	  		.attr("x", function (d) {return x_context(d.month) })
          	  		.attr("y", height_context)
          	  		.attr("height", 0)
          	  		.attr("width", bar_width)
          			.style("opacity", 0);

          // animate context bars
          context.selectAll(".bar_context")
          	.transition()
          	.duration(450)
          	.ease("elastic", 1.03, 0.98)
          	.delay(function(d, i) {
          		var max_delay = 600;
          		var z = i / (dataset.length-1);
          		var line_z =  z * max_delay * 0.4;
          		var log_z = Math.log2(z + 1) * max_delay * 0.6;
          		return(line_z + log_z);
          	})
          	.attr("y", function (d) {return y_context(d.count);	  		})
          	.attr("height", function (d) {return y_context(0) - y_context(d.count);	  		})
          	.style("opacity", 1);

          // x-axis
          context.append("g")
              .attr("class", "x axis")
              .attr("transform", "translate(0," + height_context + ")")
              .call(x_axis_context);

          /* === brush  === */

          var brushg = context.append("g")
              .attr("class", "x brush")
              .call(brush);

          brushg.selectAll(".extent")
          	.attr("y", -6)
          	.attr("height", height_context + 8)
          	.style("opacity" , "0");

          brushg.selectAll(".resize")
              .append("rect")
              .attr("class", "handle")
              .attr("transform", "translate(0," +  -3 + ")")
              .attr('rx', 1)
          	.attr('ry', 1)
              .attr("height", 0)
              .attr("width", 3)
          	.style("opacity" , "0");

          brushg.selectAll(".resize")
              .append("rect")
              .attr("class", "handle-mini")
              .attr("transform", "translate(-2,8.5)")
              .attr('rx', 2)
              .attr('ry', 2)
              .attr("height", 0)
              .attr("width", 7)
          	.style("opacity" , "0");

          /* === y axis title === */
          vis.append("text")
              .attr("class", "y axis title")
              .text("Monthly " + this.metricName)
              .attr("x", (-((height+margin.top+margin.bottom-50)/2)))
              .attr("y", 0)
              .attr("dy", "1em")
              .attr("transform", "rotate(-90)")
              .style("text-anchor", "middle");

          // allow zoom, brush, and scale behavior after a small delay,
          // so that user does not interrupt bar entrance animation.
          // show UI elements only once user is able to interact with them.
          setTimeout(function(){

              // disable the zoom behavior on wheel zoom event
              // add behaviours
            	pane.call(zoom)
                  .call(change_focus_zoom)
                  .on("wheel.zoom", null);
            	zoom.x(x);

            	vis.selectAll(".scale_button")
            		.style("cursor", "pointer")
            		.on("click", zoom_to_interval);

            	// fade in buttons
            	vis.selectAll(".scale_button,.zoomto_text")
            		.transition()
            		.duration(100)
            		.ease("cubic")
            		.style("opacity","1");

            	// fade in brush elements
            	brushg.selectAll(".extent")
            		.transition()
            		.duration(100)
            		.ease("cubic")
            		.style("opacity" , "1");

            	brushg.selectAll(".handle-mini")
            		.transition()
            		.duration(170)
            		.ease("linear")
            		.attr("height", (height_context/2))
            		.style("opacity" , "1");

            	brushg.selectAll(".handle")
            		.transition()
            		.duration(170)
            		.ease("linear")
            		.attr("height", height_context + 6)
            		.style("opacity" , "1");

              if (self.viewType === "dataset") {
                d3.select(".metric-chart")
                    .append("div")
                        .attr("class", "metric_tooltip")
                        .style("opacity", 0)
                        .style("width", tooltip_width + "px");
              }
              else {
                d3.select("#user-" + self.id)
                    .append("div")
                        .attr("class", "metric_tooltip")
                        .style("opacity", 0)
                        .style("width", tooltip_width + "px");
              }
          	},
          900);

          /*
          * ========================================================================
          *  Functions
          * ========================================================================
          */

          /*	------------------------------------------------------
          		HELPER FUNCTIONS
          	------------------------------------------------------  */

          function get_zoom_scale(){
          // custom zoom scale needed to calculate width of bars with zoom/brush.
          // can't use zoom.scale() because this needs to be reset (to one) when using change_focus_brush()
          	var x_current_width = x.domain()[1] - x.domain()[0],
          		x_total_width = x_full_extent[1] - x_full_extent[0],
          		zoom_scale = x_total_width/x_current_width;
          	return(zoom_scale);
          };

          function convert_metric_name(n){
          // remove s from metric name if count is 1
          	if (n == 1) {
          		return metricName.slice(0, -1);
          	} else {
          		return metricName;
          	}
          };

          /*	------------------------------------------------------
          		HOVER BEHAVIOUR: X-AXIS LABELS, BARS, TOOLTIPS
          	------------------------------------------------------  */

          function highlight_bar(bar_id){
          // mouseover effect on bar
          	focus.select(bar_id)
          		.style("stroke-width", "1")
          		.style("opacity", "0.9");
          };

          function unhighlight_bar(bar_id) {
          // undo mouseover effect on bar
          	focus.select(bar_id)
          		.style("stroke-width", "0")
          		.style("opacity", "1");
          };

          function highlight_label(label_id){
          // mouseover effect on label
          	focus.select(label_id).selectAll("text")
          		.style("font-weight", "bold");
          };

          function unhighlight_label(label_id){
          // undo mouseover effect on label
          	focus.select(label_id).selectAll("text")
          		.style("font-weight", "normal");
          };

          function add_tick_behaviour() {
          // adds html ID and hover behaviour to the x-axis ticks/labels
          // this function is called each time these labels/ticks are re-generated.

          	focus.selectAll(".x.axis .tick")[0].forEach(function(tick) {
          	    d3.select(tick)
          			.attr("id", function(d,i) {
          				return "label_" + d3.time.month.floor(d).getTime();
          			})
          			.on("mouseover", function(tick) {
          				// extract the datapoint from dataset that is associated with x-axis label
          				var floor_month = d3.time.month.floor(tick).getTime();
          				var d = dataset.filter( function(d) { return d.month.getTime() === floor_month; })[0];
          				highlight_bar("#bar_" + floor_month);
          				highlight_label("#label_" + floor_month);
          				show_tooltip(d);
          			})
          	    .on("mouseout", function(tick) {
          				var floor_month = d3.time.month.floor(tick).getTime();
          				unhighlight_bar("#bar_" + floor_month);
          				unhighlight_label("#label_" + floor_month);
          				hide_tooltip(tick);
          			});
          		});
          };

          function show_tooltip(d) {

              if (self.viewType === "dataset") {

                var bar_width_px = bar_width * get_zoom_scale();

                // get the width of the modal. Need for tooltip x-position.
                var modal_width = d3.select("#metric-modal")
                    .style('width')
                    .slice(0, -2);
                var modal_width = Math.round(Number(modal_width));

                d3.select(".metric_tooltip")
                    .html("<b>" + display_date_format(d.month) + "</b><br/>"  + d.count + " " + convert_metric_name(d.count))
                    .style("left", (x(d.month) + (modal_width-(width + margin.left + margin.right)) + (bar_width_px/2) - (tooltip_width/2) + "px"))//) + 300 + ((width/dataset.length) * 0.5 * get_zoom_scale())) + "px")
                    .style("top", (y(d.count) + 19) + "px");

                d3.select(".metric_tooltip")
                    .transition()
                    .duration(60)
                    .style("opacity", 0.98);
              }
              else {
                d3.select("#user-" + self.id + " > .metric_tooltip")
                    .html("<b>" + display_date_format(d.month) + "</b><br/>"  + d.count + " " + convert_metric_name(d.count))
                    .style("left", d3.event.pageX - 150 + "px")
                    .style("top", y(d.count) - y(0) - 150 + "px");

                d3.select("#user-" + self.id + " > .metric_tooltip")
                    .transition()
                    .duration(60)
                    .style("opacity", 0.98);
              }
          };

          function hide_tooltip(d) {
            if (self.viewType === "dataset") {
              d3.select(".metric_tooltip")
                  .transition()
                  .duration(60)
                  .style("opacity", 0);
            }
            else {
              d3.select("#user-" + self.id + " > .metric_tooltip")
                  .transition()
                  .duration(60)
                  .style("opacity", 0);
            }
          };


          /*	------------------------------------------------------
          		TICK FORMATTING FUNCTIONS (focus x-axis)
          	------------------------------------------------------  */


          function generate_ticks(t0, t1, dt)  {

              var label_size_px = 45;
              var max_total_labels = Math.floor(width / label_size_px);
              // offset so that labels are at the center of each month.
          	var offset = (day_in_ms*30*bar_width_factor)/2;

              function step(date, next_step)  {
                  date.setMonth(date.getMonth() + next_step);
              }

              var time = d3.time.month.floor(t0),
          		time = new Date(time.getTime() + offset),
          		times = [],
          		monthFactors = [1,3,4,12];

              while (time < t1) { times.push(new Date(+time)), step(time, 1)};

              var timesCopy = times;
              var i;

              for(i=0 ; times.length > max_total_labels ; i++){
                  var times = _.filter(timesCopy, function(d){ return (d.getMonth()) % monthFactors[i] == 0; } )
          	};

              return times;

          };

          function format_months(d){
          	add_tick_behaviour(); // add tick hover behaviour everytime ticks are re-formatted;
          	var test = (x.domain()[1] - x.domain()[0]) > 132167493818; // when to switch from yyyy to mm-yyyy
          	if(d.getMonth()==0 & test){//if january
          		var yearOnly = d3.time.format("%Y");
          		return(yearOnly(d));
          	} else {
          		return(display_date_format(d))
          	}
          }

          /*	------------------------------------------------------
          		BRUSH & ZOOM BEHAVIOUR
          	------------------------------------------------------  */

          function change_focus_brush() {
          	// make the x domain match the brush domain
              x.domain(brush.empty() ? x_context.domain() : brush.extent());
          	// reset zoom
              zoom.x(x);
          	// re-draw axis and elements at new scale
          	update_focus();
          	// update the explanatory text (total views, date range)
              update_context();
          }

          function change_focus_zoom() {
              // make the brush range change with the x domain in focus
              brush.extent(x.domain());
              vis.select(".brush").call(brush);
          	// re-draw axis and elements at new scale
          	update_focus();
              // update the explanatory text (total views, date range)
              update_context();
          }

          function update_focus() {

              // calculate where the bar goes out of focus
              var bar_width_days = bar_width_factor*30.5;

          	var left_date = x.domain()[0];
          	if(left_date.getDate() < bar_width_days){
          		var left_date = d3.time.month.floor(left_date),
          			left_date = new Date(left_date.getTime())
          	};

          	var data_subset_focus = dataset.filter( function(d) {
          		return d.month <= x.domain()[1] && d.month >= left_date
          	});

          	var y_max_focus = d3.max(data_subset_focus, function(d) { return d.count; }) * 1.04 || 1.04;
          	var y_change_duration = 85;

          	// reset y-axis
          	y.domain([0, y_max_focus]);
          	focus.select(".y.axis")
          		.transition()
          		.duration(y_change_duration*0.95)
          		.call(y_axis);

          	// reset bar height given y-axis
          	focus.selectAll(".bar")
          		.transition()
          		.duration(y_change_duration)
          		.attr("y", function (d) {return y(d.count);	  		})
          		.attr("height", function (d) {return y(0) - y(d.count);	  		});

          	// redraw other elements
          	focus.select(".x.axis").call(x_axis);
          	focus.selectAll(".bar")
          		.attr("x", function (d) {return x(d.month); })
          		.attr("width", bar_width * get_zoom_scale())
          		.style("opacity", "1"); // incase user scrolls before entrance animation finishes.

          };

          function update_context() {

          // updates display dates, total count, and decreases opacity of context bars out of focus
              var b = brush.extent();

          	// calculate where the bar goes out of focus
              var bar_width_days = bar_width_factor*30.5;
          	if(b[0].getDate() >= bar_width_days){
          		var left_date = d3.time.month.ceil(b[0]),
          			left_date = new Date(left_date.getTime())
          	} else {
          		left_date = d3.time.month.floor(b[0])
          	};

              // get the range of data in focus
              // if there's only one data point, make sure start and end month are the same
              if (metricMonths_parsed.length == 1) {
                  var start_month = display_date_format(new Date(metricMonths_parsed[0])),
                      end_month   = start_month;
              } else {
                  var start_month = (brush.empty()) ? display_date_format(x_full_extent[0]) : display_date_format(left_date),
                      end_month   = (brush.empty()) ? display_date_format(x_full_extent[1]) : display_date_format(b[1]);
              };

          	var data_subset_focus = dataset.filter(function(d) {
                  if (metricMonths_parsed.length == 1) {
                      return d.month
                  }
                  else {
                      return d.month <= display_date_format.parse(end_month) && d.month >= left_date
                  };
          	});

          	// calcualte the total views/downloads within focus area
          	var total_count = 0;
              for (var i = 0; i < data_subset_focus.length; i++) {
                      total_count += data_subset_focus[i].count;
              }

              // Update start and end dates and total count
              vis.select("#displayDates")
                  .text(start_month == end_month ? "in " + start_month : "from " + start_month + " to " + end_month);
          	vis.select("#totalCount")
          		.text(MetacatUI.appView.commaSeparateNumber(total_count) + " " + convert_metric_name(total_count));

          	// Fade all years in the bar chart not within the brush
              context.selectAll(".bar_context")
          		.style("opacity", function(d, i) {

                      if (metricMonths_parsed.length == 1) {
                          return "1";
                      } else {
                          return  d.month <= display_date_format.parse(end_month) && d.month >= left_date || brush.empty() ? "1" : ".3";
                      }

              });

          };

          function check_bounds() {
          // when brush stops moving:

              // check whether chart was scrolled out of bounds and fix,
              var b = brush.extent();
              var out_of_bounds = brush.extent().some(function(e) { return e < x_full_extent[0] | e > x_full_extent[1]; });
              if (out_of_bounds){ b = move_in_bounds(b) };

          };

          function move_in_bounds(b) {
          // move back to boundaries if user pans outside min and max date.

              var year_in_ms = 31536000000,
                  brush_start_new,
                  brush_end_new;

              if       (b[0] < x_full_extent[0])   { brush_start_new = x_full_extent[0]; }
              else if  (b[0] > x_full_extent[1])   { brush_start_new = x_full_extent[0]; }
              else                        { brush_start_new = b[0]; };

              if       (b[1] > x_full_extent[1])   { brush_end_new = x_full_extent[1]; }
              else if  (b[1] < x_full_extent[0])   { brush_end_new = x_full_extent[1]; }
              else                        { brush_end_new = b[1]; };

              brush.extent([brush_start_new, brush_end_new]);

              brush(d3.select("#" + self.id + " > .context > .brush").transition());
              change_focus_brush();
              change_focus_zoom();

              return(brush.extent())
          };

          function zoom_to_interval(d,i) {
          // action for buttons that zoom focus to certain time interval

              var b = brush.extent(),
                  interval_ms,
                  brush_end_new,
                  brush_start_new;

              if      (d == "year")   { interval_ms = 31536000000}
              else if (d == "month")  { interval_ms = 2592000000 };

              if ( d == "year" | d == "month" )  {

                  if((x_full_extent[1].getTime() - b[1].getTime()) < interval_ms){
                  // if brush is too far to the right that increasing the right-hand brush boundary would make the chart go out of bounds....
                      brush_start_new = new Date(x_full_extent[1].getTime() - interval_ms); // ...then decrease the left-hand brush boundary...
                      brush_end_new = x_full_extent[1]; //...and set the right-hand brush boundary to the maxiumum limit.
                  } else {
                  // otherwise, increase the right-hand brush boundary.
                      brush_start_new = b[0];
                      brush_end_new = new Date(b[0].getTime() + interval_ms);
                  };

              } else if ( d == "all")  {
                  brush_start_new = x_full_extent[0];
                  brush_end_new = x_full_extent[1]
              } else {
                  brush_start_new = b[0];
                  brush_end_new = b[1];
              };

              brush.extent([brush_start_new, brush_end_new]);

              // now draw the brush to match our extent

              brush(d3.select("#" + self.id + " > .context > .brush").transition());
              // now fire the brushstart, brushmove, and check_bounds events
              brush.event(d3.select("#" + self.id + " > .context > .brush").transition());
          };

          // that's it!
      }

        //Re-render this view when the window is resized
        this.listenToWindowResize();

          return this;

      },

      /**
      * Adds a listener so when the window is resized, the chart is redrawn
      */
      listenToWindowResize: function(){

        if( !this.resizeCallback ){
          this.resizeCallback = this.render.bind(this);
          window.addEventListener('resize', this.resizeCallback, false);
        }
      },

      /**
      * Removes the window resize listener set in {@link MetricsChartView#listenToWindowResize}
      */
      stopListenToWindowResize: function(){

      //Remove the listener to window resize
      window.removeEventListener("resize", this.resizeCallback, false);
      delete this.resizeCallback;

    },

      /**
      * Cleans up listeners and other artifacts from this view
      */
      onClose: function(){
        this.stopListenToWindowResize();
      }

    });

    return MetricsChartView;

});