57 lines
1.8 KiB
Ruby
57 lines
1.8 KiB
Ruby
require 'net/http'
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require 'json'
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require 'uri'
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require 'bigdecimal'
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# Fetches the current Litecoin price from CoinGecko (free, no API key).
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#
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# CoinGecko's simple/price supports usd and eur directly. GEL is not a
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# CoinGecko vs_currency we rely on, so GEL is derived from the invoice's own
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# captured gel_rate (USD->GEL): ltc_in_gel = ltc_in_usd * gel_rate.
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module LtcRate
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ENDPOINT = 'https://api.coingecko.com/api/v3/simple/price'.freeze
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SUPPORTED = %w[USD EUR].freeze
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TIMEOUT = 6 # seconds
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class Error < StandardError; end
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module_function
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# Returns a BigDecimal: the price of 1 LTC in `currency`.
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# `gel_rate` (USD->GEL) is required only when currency == 'GEL'.
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def fetch(currency, gel_rate: nil)
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currency = currency.to_s.upcase
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if currency == 'GEL'
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raise Error, 'gel_rate required to derive LTC/GEL' if gel_rate.nil?
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usd = fetch_simple('usd')
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(usd * BigDecimal(gel_rate.to_s)).round(8)
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elsif SUPPORTED.include?(currency)
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fetch_simple(currency.downcase).round(8)
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else
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raise Error, "Unsupported currency: #{currency}"
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end
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end
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def fetch_simple(vs)
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uri = URI(ENDPOINT)
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uri.query = URI.encode_www_form(ids: 'litecoin', vs_currencies: vs)
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res = Net::HTTP.start(uri.host, uri.port, use_ssl: true,
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open_timeout: TIMEOUT, read_timeout: TIMEOUT) do |http|
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http.get(uri.request_uri, 'Accept' => 'application/json')
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end
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raise Error, "CoinGecko HTTP #{res.code}" unless res.is_a?(Net::HTTPSuccess)
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data = JSON.parse(res.body)
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price = data.dig('litecoin', vs)
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raise Error, "No price for #{vs} in response" if price.nil?
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BigDecimal(price.to_s)
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rescue JSON::ParserError => e
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raise Error, "Bad JSON from CoinGecko: #{e.message}"
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rescue Net::OpenTimeout, Net::ReadTimeout
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raise Error, 'CoinGecko timed out'
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end
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end
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