Multi-currency support (#425)

* Initial foundational pass at multi-currency

* Default format currency

* More work on currency and exchanging

* Re-build currencies on change

* Currency import/setup

* Background job overhaul + cheaper OXR plan support

* Lint fixes

* Test fixes

* Multi-currency setup instructions

* Allow decimals in the balance field

* Spacing fix for form

---------

Signed-off-by: Josh Pigford <josh@joshpigford.com>

lib/tasks/currencies.rake

@@ -0,0 +1,28 @@
+namespace :currencies do
+  desc "Seed Currencies"
+  task seed: :environment do
+    currencies = ENV["CURRENCIES"].split(",")
+
+    if currencies.count > 1 && ENV["OPEN_EXCHANGE_APP_ID"].present?
+      url = "https://openexchangerates.org/api/currencies.json"
+
+      response = Faraday.get(url) do |req|
+        req.params["app_id"] = ENV["OPEN_EXCHANGE_APP_ID"]
+      end
+
+      oxr_currencies = JSON.parse(response.body)
+
+      currencies.each do |iso_code|
+        Currency.find_or_create_by(iso_code: iso_code) do |c|
+          c.name = oxr_currencies[iso_code]
+        end
+      end
+
+      puts "Currencies created: #{Currency.count}"
+    elsif currencies.count == 1
+      Currency.find_or_create_by(iso_code: currencies.first)
+    else
+      puts "No currencies found in ENV['CURRENCIES']"
+    end
+  end
+end

lib/tasks/exchange_rates.rake

@@ -0,0 +1,83 @@
+namespace :exchange_rates do
+  desc "Fetch exchange rates from openexchangerates.org"
+  task sync: :environment do
+    app_id = ENV["OPEN_EXCHANGE_APP_ID"]
+    MININUM_DATE_RANGE = 30.days
+    MAXIMUM_DATE_RANGE = 120.days
+
+    # First, check what plan the user is on at OXR
+    # If the user is on the Developer plan, we can only fetch exchange rates for the past 30 days and must use the historical endpoint
+    account_check = Faraday.get("https://openexchangerates.org/api/usage.json") do |req|
+      req.params["app_id"] = app_id
+    end
+    account_details = JSON.parse(account_check.body)
+    quota_limit = account_details["data"]["usage"]["requests_quota"]
+
+    if quota_limit <= 10000
+      # First loop through all Currency records and fetch exchange rates for each, but use the historical endpoint, which only allows fetching one day at a time. For each currency, set the base currency to the currency's iso_code and the symbols to all other currencies' iso_codes
+      Currency.all.each do |currency|
+        (Date.today - MININUM_DATE_RANGE).upto(Date.today) do |date|
+          response = Faraday.get("https://openexchangerates.org/api/historical/#{date}.json") do |req|
+            req.params["app_id"] = app_id
+            req.params["base"] = currency.iso_code
+            req.params["symbols"] = Currency.where.not(iso_code: currency.iso_code).pluck(:iso_code).join(",")
+          end
+
+          if response.success?
+            rates = JSON.parse(response.body)["rates"]
+
+            rates.each do |currency_iso_code, value|
+              ExchangeRate.find_or_create_by(date: date, base_currency: currency.iso_code, converted_currency: currency_iso_code) do |exchange_rate|
+                exchange_rate.rate = value
+              end
+              puts "#{currency.iso_code} to #{currency_iso_code} on #{date}: #{value}"
+            end
+          else
+            puts "Failed to fetch exchange rates for #{currency.iso_code} on #{date}: #{response.status}"
+          end
+        end
+      end
+    else
+      # Use Faraday to make a request openexchangerates.org time series endpoint
+      # Use the response to create or update exchange rates in the database
+      url = "https://openexchangerates.org/api/time-series.json"
+      start_date = (Date.today - MAXIMUM_DATE_RANGE).to_s
+      end_date = Date.today.to_s
+
+      # Loop through all Currency records and fetch exchange rates for each
+      Currency.all.each do |currency|
+        start_period = Date.parse(start_date)
+        end_period = Date.parse(end_date)
+
+        while start_period < end_period
+          current_end_date = [ start_period + 30.days, end_period ].min
+
+          response = Faraday.get(url) do |req|
+            req.params["app_id"] = app_id
+            req.params["start"] = start_period.to_s
+            req.params["end"] = current_end_date.to_s
+            req.params["base"] = currency.iso_code
+            req.params["symbols"] = Currency.where.not(iso_code: currency.iso_code).pluck(:iso_code).join(",")
+          end
+
+          if response.success?
+            rates = JSON.parse(response.body)["rates"]
+
+            rates.each do |date, rate|
+              rate.each do |currency_iso_code, value|
+                ExchangeRate.find_or_create_by(date: date, base_currency: currency.iso_code, converted_currency: currency_iso_code) do |exchange_rate|
+                  exchange_rate.rate = value
+                end
+                puts "#{currency.iso_code} to #{currency_iso_code} on #{date}: #{value}"
+              end
+            end
+          else
+            puts "Failed to fetch exchange rates for period #{start_period} to #{current_end_date}: #{response.status}"
+          end
+
+          start_period = current_end_date + 1.day
+        end
+      end
+    end
+  end
+end