Multi-Currency Part 2 (#543)

* Support all currencies, handle outside DB

* Remove currencies from seed

* Fix account balance namespace

* Set default currency on authentication

* Cache currency instances

* Implement multi-currency syncs with tests

* Series fallback, passing tests

* Fix conflicts

* Make value group concrete class that works with currency values

* Fix migration conflict

* Update tests to expect multi-currency results

* Update account list to use group method

* Namespace updates

* Fetch unknown exchange rates from API

* Fix date range bug

* Ensure demo data works without external API

* Enforce cascades only at DB level

app/models/value_group.rb

@@ -1,29 +1,29 @@
   class ValueGroup
-    attr_accessor :parent
-    attr_reader :name, :children, :value, :original
+    attr_accessor :parent, :original
+    attr_reader :name, :children, :value, :currency
 
-    def initialize(name = "Root", value: nil, original: nil)
+    def initialize(name, currency = Money.default_currency)
         @name = name
-        @value = value
+        @currency = Money::Currency.new(currency)
         @children = []
-        @original = original
     end
 
     def sum
         return value if is_value_node?
-        return 0 if children.empty? && value.nil?
+        return Money.new(0, currency) if children.empty? && value.nil?
         children.sum(&:sum)
     end
 
     def avg
         return value if is_value_node?
-        return 0 if children.empty? && value.nil?
+        return Money.new(0, currency) if children.empty? && value.nil?
         leaf_values = value_nodes.map(&:value)
-        leaf_values.compact.sum.to_f / leaf_values.compact.size
+        leaf_values.compact.sum / leaf_values.compact.size
     end
 
     def series
-        return @raw_series || TimeSeries.new([]) if is_value_node?
+        return @series if is_value_node?
+
         summed_by_date = children.each_with_object(Hash.new(0)) do |child, acc|
             child.series.values.each do |series_value|
                 acc[series_value.date] += series_value.value
@@ -31,43 +31,63 @@
         end
 
         summed_series = summed_by_date.map { |date, value| { date: date, value: value } }
+
         TimeSeries.new(summed_series)
     end
 
+    def series=(series)
+        raise "Cannot set series on a non-leaf node" unless is_value_node?
+
+        _series = series || TimeSeries.new([])
+
+        raise "Series must be an instance of TimeSeries" unless _series.is_a?(TimeSeries)
+        raise "Series must contain money values in the node's currency" unless _series.values.all? { |v| v.value.currency == currency }
+        @series = _series
+    end
+
     def value_nodes
         return [ self ] unless value.nil?
         children.flat_map { |child| child.value_nodes }
     end
 
+    def empty?
+        value_nodes.empty?
+    end
+
     def percent_of_total
         return 100 if parent.nil? || parent.sum.zero?
 
         ((sum / parent.sum) * 100).round(1)
     end
 
-    def leaf?
-        children.empty?
-    end
-
-    def add_child_node(name)
+    def add_child_group(name, currency = Money.default_currency)
         raise "Cannot add subgroup to node with a value" if is_value_node?
-        child = self.class.new(name)
+        child = self.class.new(name, currency)
         child.parent = self
         @children << child
         child
     end
 
-    def add_value_node(obj)
+    def add_value_node(original, value, series = nil)
         raise "Cannot add value node to a non-leaf node" unless can_add_value_node?
-        child = create_value_node(obj)
+        child = self.class.new(original.name)
+        child.original = original
+        child.value = value
+        child.series = series
         child.parent = self
         @children << child
         child
     end
 
-    def attach_series(raw_series)
-        validate_attached_series(raw_series)
-        @raw_series = raw_series
+    def value=(value)
+        raise "Cannot set value on a non-leaf node" unless is_leaf_node?
+        raise "Value must be an instance of Money" unless value.is_a?(Money)
+        @value = value
+        @currency = value.currency
+    end
+
+    def is_leaf_node?
+        children.empty?
     end
 
     def is_value_node?
@@ -79,23 +99,4 @@
             return false if is_value_node?
             children.empty? || children.all?(&:is_value_node?)
         end
-
-        def create_value_node(obj)
-            value = if obj.respond_to?(:value)
-                obj.value
-            elsif obj.respond_to?(:balance)
-                obj.balance
-            elsif obj.respond_to?(:amount)
-                obj.amount
-            else
-                raise ArgumentError, "Object must have a value, balance, or amount"
-            end
-
-            self.class.new(obj.name, value: value, original: obj)
-        end
-
-        def validate_attached_series(series)
-            raise "Cannot add series to a node without a value" unless is_value_node?
-            raise "Attached series must be a TimeSeries" unless series.is_a?(TimeSeries)
-        end
   end