Refactor TimeSeries artifacts (#651)

* Reindent TimeSeries classes

* Fix spacing in time series tests

* Remove trend tests where current is nil

I think if we've gotten this far with a nil value for current, there's a data integrity problem.

If we allow this, we'll have to be very defensive in our code. Best to raise and fix early.

* Reindent Money class

* Refactor TimeSeries artifacts

* Use as_json in TimeSeries

* Bring back tests for trends where current is nil

* Bring back trend test

* Correctly enumerate trend test

* Use favorable_direction for trend_styles helper

* Make trend public in TimeSeries::Value

* Allow nil current values in trends

I think I might've gotten it wrong before, nils might appear in trends if values are unavailable for snapshots

* Clean up TimeSeries::Trend

* Skip trend values same class validations if any values are nil

* Refactor Money

* Remove object parsing in TimeSeries::Value

We're only every passing hashes

app/models/time_series.rb

@@ -1,83 +1,57 @@
-
 class TimeSeries
-    attr_reader :type
+  DIRECTIONS = %w[ up down ].freeze
 
-    def self.from_collection(collection, value_method, options = {})
-        data = collection.map do |obj|
-            { date: obj.date, value: obj.public_send(value_method), original: obj }
-        end
-        new(data, options)
+  attr_reader :values, :favorable_direction
+
+  def self.from_collection(collection, value_method)
+    collection.map do |obj|
+      {
+        date: obj.date,
+        value: obj.public_send(value_method),
+        original: obj
+      }
+    end.then { |data| new(data) }
+  end
+
+  def initialize(data, favorable_direction: "up")
+    @favorable_direction = (favorable_direction.presence_in(DIRECTIONS) || "up").inquiry
+    @values = initialize_values data
+  end
+
+  def first
+    values.first
+  end
+
+  def last
+    values.last
+  end
+
+  def on(date)
+    values.find { |v| v.date == date }
+  end
+
+  def trend
+    TimeSeries::Trend.new \
+      current: last&.value,
+      previous: first&.value,
+      series: self
+  end
+
+  # `as_json` returns the data shape used by D3 charts
+  def as_json
+    {
+      values: values.map(&:as_json),
+      trend: trend.as_json,
+      favorable_direction: favorable_direction
+    }.as_json
+  end
+
+  private
+    def initialize_values(data)
+      [ nil, *data ].each_cons(2).map do |previous, current|
+        TimeSeries::Value.new **current,
+          previous_value: previous.try(:[], :value),
+          series: self
+      end
     end
-
-    def initialize(data, options = {})
-        @type = options[:type] || :normal
-        initialize_series_data(data)
-    end
-
-    def values
-        @values ||= add_trends_to_series
-    end
-
-    def first
-        values.first
-    end
-
-    def last
-        values.last
-    end
-
-    def on(date)
-        values.find { |v| v.date == date }
-    end
-
-    def trend
-        TimeSeries::Trend.new(
-            current: last&.value,
-            previous: first&.value,
-            type: @type
-        )
-    end
-
-    # Data shape that frontend expects for D3 charts
-    def to_json(*_args)
-        {
-            values: values.map do |v|
-                {
-                    date: v.date,
-                    value: JSON.parse(v.value.to_json),
-                    trend: {
-                        type: v.trend.type,
-                        direction: v.trend.direction,
-                        value: JSON.parse(v.trend.value.to_json),
-                        percent: v.trend.percent
-                    }
-                }
-            end,
-            trend: {
-                type: @type,
-                direction: trend.direction,
-                value: JSON.parse(trend.value.to_json),
-                percent: trend.percent
-            },
-            type: @type
-        }.to_json
-    end
-
-    private
-        def initialize_series_data(data)
-            @series_data = data.nil? || data.empty? ? [] : data.map { |d| TimeSeries::Value.new(d) }.sort_by(&:date)
-        end
-
-        def add_trends_to_series
-            [ nil, *@series_data ].each_cons(2).map do |previous, current|
-                unless current.trend
-                    current.trend = TimeSeries::Trend.new(
-                        current: current.value,
-                        previous: previous&.value,
-                        type: @type
-                    )
-                end
-                current
-            end
-        end
 end