lib/money/bank/openexchangerates_bank.rb
# encoding: UTF-8
# frozen_string_literal: true
require 'open-uri'
require 'money'
require 'json'
# Money gem class
class Money
# Build in memory rates store
module RatesStore
# Memory class
class Memory
# Add method to reset the build in memory store
# @param [Hash] rt Optional initial exchange rate data.
# @return [Object] store.
def reset!(rt = {})
transaction { @index = rt }
end
end
end
# https://github.com/RubyMoney/money#exchange-rate-stores
module Bank
# Invalid cache, file not found or cache empty
class InvalidCache < StandardError; end
# App id not set error
class NoAccessKey < StandardError; end
# CurrencylayerBank base class
class OpenexchangeratesBank < Money::Bank::VariableExchange
# CurrencylayerBank url
CL_URL = 'http://openexchangerates.org/api/latest.json'.freeze
# CurrencylayerBank secure url
CL_SECURE_URL = CL_URL.sub('http:', 'https:')
# Default base currency
CL_SOURCE = 'USD'.freeze
# Use https to fetch rates from CurrencylayerBank
# CurrencylayerBank only allows http as connection
# for the free plan users.
#
# @param value [Boolean] true for secure connection
# @return [Boolean] chosen secure connection
attr_accessor :secure_connection
# API must have a valid access_key
#
# @param value [String] API access key
# @return [String] chosen API access key
attr_accessor :access_key
# Cache accessor, can be a String or a Proc
#
# @param value [String,Pathname,Proc] cache system
# @return [String,Pathname,Proc] chosen cache system
attr_accessor :cache
# Parsed CurrencylayerBank result as Hash
attr_reader :rates
# Get the timestamp of rates in memory
# @return [Time] time object or nil
attr_reader :rates_mem_timestamp
# Set the seconds after than the current rates are automatically expired
# by default, they never expire.
#
# @example
# ttl_in_seconds = 86400 # will expire the rates in one day
#
# @param value [Integer] time to live in seconds
# @return [Integer] chosen time to live in seconds
attr_writer :ttl_in_seconds
# Set the base currency for all rates. By default, USD is used.
# CurrencylayerBank only allows USD as base currency
# for the free plan users.
#
# @example
# source = 'USD'
#
# @param value [String] Currency code, ISO 3166-1 alpha-3
# @return [String] chosen base currency
def source=(value)
@source = Money::Currency.find(value.to_s).try(:iso_code) || CL_SOURCE
end
# Get the base currency for all rates. By default, USD is used.
# @return [String] base currency
def source
@source ||= CL_SOURCE
end
# Set alternative system, to request alternative rates
#
# @example
# alternatives = :all
# alternatives = :only
# alternatives = nil
#
# @param value [String,Symbol] alternatives
# @return [String,nil] chosen alternative system
def alternatives=(system)
@alternatives = case system.to_sym
when :all
'show_alternative'
when :only
'only_alternative'
end
end
# Get alternative system. Default is nil
# @return [String,nil] chosen alternative system
def alternatives
@alternatives || nil
end
# Get the seconds after than the current rates are automatically expired
# by default, they never expire.
# @return [Integer] chosen time to live in seconds
def ttl_in_seconds
@ttl_in_seconds ||= 0
end
# Update all rates from CurrencylayerBank JSON
# @return [Array] array of exchange rates
def update_rates(straight = false)
store.reset!
rates = exchange_rates(straight).each do |exchange_rate|
currency = exchange_rate.first
rate = exchange_rate.last
next unless Money::Currency.find(currency)
add_rate(source, currency, rate)
add_rate(currency, source, 1.0 / rate)
end
@rates_mem_timestamp = rates_timestamp
rates
end
# Override Money `add_rate` method for caching
# @param [String] from_currency Currency ISO code. ex. 'USD'
# @param [String] to_currency Currency ISO code. ex. 'CAD'
# @param [Numeric] rate Rate to use when exchanging currencies.
# @return [Numeric] rate.
def add_rate(from_currency, to_currency, rate)
super
end
# Alias super method
alias super_get_rate get_rate
# Override Money `get_rate` method for caching
# @param [String] from_currency Currency ISO code. ex. 'USD'
# @param [String] to_currency Currency ISO code. ex. 'CAD'
# @param [Hash] opts Options hash to set special parameters.
# @return [Numeric] rate.
def get_rate(from_currency, to_currency, opts = {})
expire_rates!
rate = get_rate_or_calc_inverse(from_currency, to_currency, opts)
rate || calc_pair_rate_using_base(from_currency, to_currency, opts)
end
# Fetch new rates if cached rates are expired or stale
# @return [Boolean] true if rates are expired and updated from remote
def expire_rates!
if expired?
update_rates(true)
true
elsif stale?
update_rates
true
else
false
end
end
# Check if rates are expired
# @return [Boolean] true if rates are expired
def expired?
Time.now > rates_expiration
end
# Check if rates are stale
# Stale is true if rates are updated straight by another thread.
# The actual thread has always old rates in memory store.
# @return [Boolean] true if rates are stale
def stale?
rates_timestamp != rates_mem_timestamp
end
# Source url of CurrencylayerBank
# defined with access_key and secure_connection
# @return [String] the remote API url
def source_url
raise NoAccessKey if access_key.nil? || access_key.empty?
cl_url = CL_URL
cl_url = CL_SECURE_URL if secure_connection
params = "#{cl_url}?base=#{source}&app_id=#{access_key}&prettyprint=0"
params += "&#{alternatives}=1" unless alternatives.nil?
params
end
# Get rates expiration time based on ttl
# @return [Time] rates expiration time
def rates_expiration
rates_timestamp + ttl_in_seconds
end
# Get the timestamp of rates
# @return [Time] time object or nil
def rates_timestamp
raw = raw_rates_careful
raw.key?('timestamp') ? Time.at(raw['timestamp']) : Time.at(0)
end
protected
# Store the provided text data by calling the proc method provided
# for the cache, or write to the cache file.
#
# @example
# store_in_cache("{\"rates\": {\"AED\": 3.67304}}")
#
# @param text [String] parsed JSON content
# @return [String,Integer]
def store_in_cache(text)
if cache.is_a?(Proc)
cache.call(text)
elsif cache.is_a?(String) || cache.is_a?(Pathname)
write_to_file(text)
end
end
# Writes content to file cache
# @param text [String] parsed JSON content
# @return [String,Integer]
def write_to_file(text)
open(cache, 'w') do |f|
f.write(text)
end
rescue Errno::ENOENT
raise InvalidCache
end
# Read from cache when exist
# @return [Proc,String] parsed JSON content
def read_from_cache
if cache.is_a?(Proc)
cache.call(nil)
elsif (cache.is_a?(String) || cache.is_a?(Pathname)) &&
File.exist?(cache)
open(cache).read
end
end
# Get remote content and store in cache
# @return [String] unparsed JSON content
def read_from_url
text = open_url
store_in_cache(text) if valid_rates?(text) && cache
text
end
# Opens an url and reads the content
# @return [String] unparsed JSON content
def open_url
URI.open(source_url).read
rescue OpenURI::HTTPError
''
end
# Check validity of rates response only for store in cache
#
# @example
# valid_rates?("{\"rates\": {\"AED\": 3.67304}}")
#
# @param [String] text is JSON content
# @return [Boolean] valid or not
def valid_rates?(text)
parsed = JSON.parse(text)
parsed && parsed.key?('rates')
rescue JSON::ParserError
false
end
# Get exchange rates with different strategies
#
# @example
# exchange_rates(true)
# exchange_rates
#
# @param straight [Boolean] true for straight, default is careful
# @return [Hash] key is country code (ISO 3166-1 alpha-3) value Float
def exchange_rates(straight = false)
rates = if straight
raw_rates_straight
else
raw_rates_careful
end
if rates.key?('rates')
@rates = rates['rates']
elsif rates.key?('error')
raise Error, rates['description']
else
raise Error, 'Unknown rates situation!'
end
end
# Get raw exchange rates from cache and then from url
# @param rescue_straight [Boolean] true for rescue straight, default true
# @return [String] JSON content
def raw_rates_careful(rescue_straight = true)
JSON.parse(read_from_cache.to_s)
rescue JSON::ParserError
rescue_straight ? raw_rates_straight : { 'rates' => {} }
end
# Get raw exchange rates from url
# @return [String] JSON content
def raw_rates_straight
JSON.parse(read_from_url)
rescue JSON::ParserError
raw_rates_careful(false)
end
# Get rate or calculate it as inverse rate
# @param [String] from_currency Currency ISO code. ex. 'USD'
# @param [String] to_currency Currency ISO code. ex. 'CAD'
# @return [Numeric] rate or rate calculated as inverse rate.
def get_rate_or_calc_inverse(from_currency, to_currency, opts = {})
rate = super_get_rate(from_currency, to_currency, opts)
unless rate
# Tries to calculate an inverse rate
inverse_rate = super_get_rate(to_currency, from_currency, opts)
if inverse_rate
rate = 1.0 / inverse_rate
add_rate(from_currency, to_currency, rate)
end
end
rate
end
# Tries to calculate a pair rate using base currency rate
# @param [String] from_currency Currency ISO code. ex. 'USD'
# @param [String] to_currency Currency ISO code. ex. 'CAD'
# @return [Numeric] rate or nil if cannot calculate rate.
def calc_pair_rate_using_base(from_currency, to_currency, opts = {})
from_base_rate = get_rate_or_calc_inverse(source, from_currency, opts)
to_base_rate = get_rate_or_calc_inverse(source, to_currency, opts)
if to_base_rate && from_base_rate
rate = to_base_rate / from_base_rate
add_rate(from_currency, to_currency, rate)
return rate
end
nil
end
end
end
end