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98 lines
2.8 KiB
Ruby
98 lines
2.8 KiB
Ruby
class Money
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include Comparable, Arithmetic, Formatting
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include ActiveModel::Validations
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class ConversionError < StandardError
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attr_reader :from_currency, :to_currency, :date
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def initialize(from_currency:, to_currency:, date:)
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@from_currency = from_currency
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@to_currency = to_currency
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@date = date
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error_message = message || "Couldn't find exchange rate from #{from_currency} to #{to_currency} on #{date}"
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super(error_message)
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end
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end
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attr_reader :amount, :currency, :store
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validate :source_must_be_of_known_type
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class << self
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def default_currency
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@default ||= Money::Currency.new(:usd)
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end
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def default_currency=(object)
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@default = Money::Currency.new(object)
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end
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end
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def initialize(obj, currency = Money.default_currency, store: ExchangeRate)
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@source = obj
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@amount = obj.is_a?(Money) ? obj.amount : BigDecimal(obj.to_s)
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@currency = obj.is_a?(Money) ? obj.currency : Money::Currency.new(currency)
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@store = store
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validate!
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end
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# Exchange money to another currency
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# Params:
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# other_currency: target currency code (e.g. "USD")
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# date: date for historical rates (default: Date.current)
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# custom_rate: explicit exchange rate to use (skips lookup if provided, including nil check)
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# Priority:
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# 1. Use custom_rate if explicitly provided (not nil)
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# 2. Look up rate via store.find_or_fetch_rate
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# 3. Raise ConversionError if no valid rate available
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def exchange_to(other_currency, date: Date.current, custom_rate: nil)
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iso_code = currency.iso_code
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other_iso_code = Money::Currency.new(other_currency).iso_code
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if iso_code == other_iso_code
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self
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else
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# Use custom rate if provided, otherwise look it up
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if custom_rate.present?
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exchange_rate = custom_rate.to_d
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else
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exchange_rate = store.find_or_fetch_rate(from: iso_code, to: other_iso_code, date: date)&.rate
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end
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raise ConversionError.new(from_currency: iso_code, to_currency: other_iso_code, date: date) unless exchange_rate && exchange_rate > 0
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Money.new(amount * exchange_rate, other_iso_code)
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end
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end
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def as_json
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{ amount: amount, currency: currency.iso_code, formatted: format }.as_json
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end
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def <=>(other)
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raise TypeError, "Money can only be compared with other Money objects except for 0" unless other.is_a?(Money) || other.eql?(0)
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if other.is_a?(Numeric)
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amount <=> other
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else
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amount_comparison = amount <=> other.amount
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if amount_comparison == 0
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currency <=> other.currency
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else
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amount_comparison
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end
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end
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end
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private
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def source_must_be_of_known_type
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unless @source.is_a?(Money) || @source.is_a?(Numeric) || @source.is_a?(BigDecimal)
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errors.add :source, "must be a Money, Numeric, or BigDecimal"
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end
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end
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end
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