Add Money and Money Series (#505)

* Add Money class

* Standardize creation of money series

* Formatting

* Fix test

app/models/account.rb

@@ -28,29 +28,17 @@ class Account < ApplicationRecord
   end
 
   def balance_series(period)
-    filtered_balances = balances.in_period(period).order(:date)
-    return nil if filtered_balances.empty?
-
-    series_data = [ nil, *filtered_balances ].each_cons(2).map do |previous, current|
-      trend = current&.trend(previous)
-      { data: current, trend: { amount: trend&.amount, direction: trend&.direction, percent: trend&.percent } }
-    end
-
-    last_balance = series_data.last[:data]
-
-    {
-      series_data: series_data,
-      last_balance: last_balance.balance,
-      trend: last_balance.trend(series_data.first[:data])
-    }
+    MoneySeries.new(
+      balances.in_period(period).order(:date),
+      { trend_type: classification }
+    )
   end
 
   def valuation_series
-    series_data = [ nil, *valuations.order(:date) ].each_cons(2).map do |previous, current|
-      { value: current, trend: current&.trend(previous) }
-    end
-
-    series_data.reverse_each
+    MoneySeries.new(
+      valuations.order(:date),
+      { trend_type: classification, amount_accessor: :value }
+    )
   end
 
   def check_currency

app/models/money.rb

@@ -0,0 +1,32 @@
+class Money
+    attr_reader :amount, :currency
+
+    def self.from_amount(amount, currency = "USD")
+        Money.new(amount, currency)
+    end
+
+    def initialize(amount, currency = :USD)
+        @amount = amount
+        @currency = currency
+    end
+
+    def cents(precision: nil)
+        _precision = precision || CURRENCY_OPTIONS[@currency.to_sym][:precision]
+        return "" unless _precision.positive?
+
+        fractional_part = @amount.to_s.split(".")[1] || ""
+        fractional_part = fractional_part[0, _precision].ljust(_precision, "0")
+    end
+
+    def symbol
+        CURRENCY_OPTIONS[@currency.to_sym][:symbol]
+    end
+
+    def separator
+        CURRENCY_OPTIONS[@currency.to_sym][:separator]
+    end
+
+    def precision
+        CURRENCY_OPTIONS[@currency.to_sym][:precision]
+    end
+end

app/models/money_series.rb

@@ -0,0 +1,60 @@
+class MoneySeries
+    def initialize(series, options = {})
+        @trend_type = options[:trend_type] || :asset # Defines whether a positive trend is good or bad
+        @accessor = options[:amount_accessor] || :balance
+        @series = series
+    end
+
+    def valid?
+        @series.length > 1
+    end
+
+    def data
+        [ nil, *@series ].each_cons(2).map do |previous, current|
+            {
+                raw: current,
+                date: current.date,
+                value: Money.from_amount(current.send(@accessor), current.currency),
+                trend: Trend.new(
+                    current: current.send(@accessor),
+                    previous: previous&.send(@accessor),
+                    type: @trend_type
+                )
+            }
+        end
+    end
+
+    def trend
+        return Trend.new(current: 0, type: @trend_type) unless valid?
+
+        Trend.new(
+            current: @series.last.send(@accessor),
+            previous: @series.first&.send(@accessor),
+            type: @trend_type
+        )
+    end
+
+    def serialize_for_d3_chart
+        {
+            data: data.map do |datum|
+                {
+                    date: datum[:date],
+                    amount: datum[:value].amount,
+                    currency: datum[:value].currency,
+                    trend: {
+                        amount: datum[:trend].amount,
+                        percent: datum[:trend].percent,
+                        direction: datum[:trend].direction,
+                        type: datum[:trend].type
+                    }
+                }
+            end,
+            trend: {
+                amount: trend.amount,
+                percent: trend.percent,
+                direction: trend.direction,
+                type: trend.type
+            }
+        }.to_json
+    end
+end

app/models/trend.rb

@@ -1,26 +1,27 @@
 class Trend
-    attr_reader :current, :previous
+  attr_reader :current, :previous, :type
 
-    def initialize(current, previous)
-        @current = current
-        @previous = previous
-    end
+  def initialize(current:, previous: nil, type: :asset)
+    @current = current
+    @previous = previous
+    @type = type # :asset means positive trend is good, :liability means negative trend is good
+  end
 
-    def direction
-        return "flat" unless @previous
-        return "up" if @current > @previous
-        return "down" if @current < @previous
-        "flat"
-    end
+  def direction
+    return "flat" unless @previous
+    return "up" if @current > @previous
+    return "down" if @current < @previous
+    "flat"
+  end
 
-    def amount
-      return 0 if @previous.nil?
-      @current - @previous
-    end
+  def amount
+    return 0 if @previous.nil?
+    @current - @previous
+  end
 
-    def percent
-      return 0 if @previous.nil?
-      return Float::INFINITY if @previous == 0
-      ((@current - @previous).abs / @previous.to_f * 100).round(1)
-    end
+  def percent
+    return 0 if @previous.nil?
+    return Float::INFINITY if @previous == 0
+    ((@current - @previous).abs / @previous.to_f * 100).round(1)
+  end
 end

app/models/valuation.rb

@@ -4,7 +4,7 @@ class Valuation < ApplicationRecord
   after_commit :sync_account
 
   def trend(previous)
-    Trend.new(value, previous&.value)
+    Trend.new(current: value, previous: previous&.value, type: account.classification)
   end
 
   private