62 lines
1.5 KiB
Ruby
62 lines
1.5 KiB
Ruby
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# frozen_string_literal: true
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class BaseConversion
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attr_reader :rates, :base
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def initialize(rates, base:)
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@rates = rates
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@base = base
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end
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def convert
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rates.group_by { |r| r[:provider] }.flat_map do |provider, group|
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converted = convert_group(group).map { |r| r.merge(provider:) }
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seen = {}
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converted.each do |r|
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key = [r[:date], r[:quote]]
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raise "ambiguous bridge: #{provider} produced #{key.inspect} twice" if seen[key]
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seen[key] = true
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end
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converted
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end
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end
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private
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def convert_group(group)
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group.filter_map do |rate|
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if rate[:base] == base
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rate.except(:provider)
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elsif rate[:quote] == base
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invert(rate)
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else
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cross_convert(rate, group)
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end
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end
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end
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def invert(rate)
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{ date: rate[:date], base:, quote: rate[:base], rate: 1.0 / rate[:rate] }
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end
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def cross_convert(rate, group)
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bridge = group.find { |r| r[:base] == base && r[:quote] == rate[:quote] }
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if bridge
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return { date: rate[:date], base:, quote: rate[:base], rate: bridge[:rate] / rate[:rate] }
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end
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bridge = group.find { |r| r[:base] == base && r[:quote] == rate[:base] }
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if bridge
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return { date: rate[:date], base:, quote: rate[:quote], rate: rate[:rate] * bridge[:rate] }
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end
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bridge = group.find { |r| r[:base] == rate[:base] && r[:quote] == base }
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if bridge
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return { date: rate[:date], base:, quote: rate[:quote], rate: rate[:rate] / bridge[:rate] }
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end
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nil
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end
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end
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