Class: RwandaNationalBank::HistoricRates

Inherits:
Object
  • Object
show all
Defined in:
lib/rwanda_national_bank/historic_rates.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ HistoricRates

Returns a new instance of HistoricRates.



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 12

def initialize options = {}
  @as_of = options[:as_of] || Date.yesterday
end

Instance Attribute Details

#as_of ⇒ Object (readonly)

Returns the value of attribute as_of.



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 10

def as_of
  @as_of
end

Class Method Details

.scrape(as_of) ⇒ Object

Scrapes the RNB website for the historic exchange rates of a given day



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 56

def self.scrape as_of
  # POST /index.php?id=384
  uri = URI('http://www.bnr.rw/index.php?id=384')

  # fday=30&fmonth=NOV&fyear=2015&history=Get+History
  params = {
    'fday'    => as_of.strftime('%d'),
    'fmonth'  => as_of.strftime('%b').upcase,
    'fyear'   => as_of.strftime('%Y'),
    'history' => 'Get History'
  }

  response = Net::HTTP.post_form(uri, params)
  dom = Nokogiri::HTML(response.body)
  rows = dom.css('#middlebar > table > tr') # will always return an []

  # RNB does not really use ISO codes thoroughly so we have to map some of their symbols
  translate_currency_symbols = {
    'KD' => 'KWD', # Kuwait Dinar
    'RS' => 'INR', # Indian Rupees
    'LD' => 'LRD' # Lybian Dinar
  }

  Hash[rows.map do |row|
    currency = row.css(':nth-child(1) > a').text
    next if currency.empty?
    avrg = row.css(':nth-child(4)').text
    next if avrg.empty?

    # translate currency to ISO symbol
    currency = translate_currency_symbols[currency.upcase] || currency

    [currency, Float(avrg)] rescue nil
  end.compact]
end

Instance Method Details

#currencies ⇒ Object

Returns a list of ISO currencies



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 29

def currencies
  fail MissingRates unless has_rates?
  @rates.keys
end

#has_rates? ⇒ Boolean

Returns true when reading the website was successful

Returns:

  • (Boolean) 


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# File 'lib/rwanda_national_bank/historic_rates.rb', line 41

def has_rates?
  !@rates.nil? && !@rates.empty?
end

#import! ⇒ Object

Triggers the srcaping



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 46

def import!
  @rates = scrape(@as_of)
  has_rates?
end

#rate(iso_from, iso_to) ⇒ Object 



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 16

def rate(iso_from, iso_to)
  fail MissingRates unless has_rates?

  if iso_from == 'RWF'
    rates[iso_to] ? 1/rates[iso_to] : nil
  elsif iso_to == 'RWF'
    rates[iso_from]
  else
    nil
  end
end

#rates ⇒ Object

Returns all rates returned



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 35

def rates
  fail MissingRates unless has_rates?
  @rates
end

#scrape(as_of) ⇒ Object 



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# File 'lib/rwanda_national_bank/historic_rates.rb', line 51

def scrape as_of
  self.class.scrape(@as_of)
end