Class: Straight::ExchangeRate::Adapter

Inherits:
Object
  • Object
show all
Includes:
Singleton
Defined in:
lib/straight/exchange_rate_adapter.rb

Defined Under Namespace

Classes: CurrencyNotSupported, FetchingFailed

Instance Method Summary collapse

Constructor Details

#initialize(rates_expire_in: 1800) ⇒ Adapter

Returns a new instance of Adapter.



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# File 'lib/straight/exchange_rate_adapter.rb', line 11

def initialize(rates_expire_in: 1800)
  @rates_expire_in = rates_expire_in # in seconds
end

Instance Method Details

#convert_from_currency(amount_in_currency, btc_denomination: :satoshi, currency: 'USD') ⇒ Object 



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# File 'lib/straight/exchange_rate_adapter.rb', line 15

def convert_from_currency(amount_in_currency, btc_denomination: :satoshi, currency: 'USD')
  btc_amount = amount_in_currency.to_f/rate_for(currency)
  Satoshi.new(btc_amount, from_unit: :btc, to_unit: btc_denomination).to_unit
end

#convert_to_currency(amount, btc_denomination: :satoshi, currency: 'USD') ⇒ Object 



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# File 'lib/straight/exchange_rate_adapter.rb', line 20

def convert_to_currency(amount, btc_denomination: :satoshi, currency: 'USD')
  amount_in_btc = Satoshi.new(amount.to_f, from_unit: btc_denomination).to_btc
  amount_in_btc*rate_for(currency)
end

#fetch_rates! ⇒ Object 



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# File 'lib/straight/exchange_rate_adapter.rb', line 25

def fetch_rates!
  raise "FETCH_URL is not defined!" unless self.class::FETCH_URL
  uri = URI.parse(self.class::FETCH_URL)
  begin
    @rates            = JSON.parse(uri.read(read_timeout: 4))
    @rates_updated_at = Time.now
  rescue OpenURI::HTTPError => e
    raise FetchingFailed
  end
end

#get_rate_value_from_hash(rates_hash, *keys) ⇒ Object

This method will get value we are interested in from hash and prevent failing with ‘undefined method [] for Nil’ if at some point hash doesn’t have such key value pair



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# File 'lib/straight/exchange_rate_adapter.rb', line 45

def get_rate_value_from_hash(rates_hash, *keys)
  keys.inject(rates_hash) do |intermediate, key|
    if intermediate.respond_to?(:[])
      intermediate[key]
    else
      raise CurrencyNotSupported 
    end
  end
end

#rate_for(currency_code) ⇒ Object 



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# File 'lib/straight/exchange_rate_adapter.rb', line 36

def rate_for(currency_code)
  if !@rates_updated_at || (Time.now - @rates_updated_at) > @rates_expire_in
    fetch_rates!
  end
  nil # this should be changed in descendant classes
end

#rate_to_f(rate) ⇒ Object

We dont want to have false positive rate, because nil.to_f is 0.0 This method checks that rate value is not nil



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# File 'lib/straight/exchange_rate_adapter.rb', line 57

def rate_to_f(rate)
  rate ? rate.to_f : raise(CurrencyNotSupported)
end