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defmodule WalletLimitsFees.Queries.CalculateFee do |
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@moduledoc """ |
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Query handler for calculating the applicable fee for a transfer. |
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Delegates to PolicyEngine and captures a PolicyDecisionCaptured event. |
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""" |
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alias WalletLimitsFees.PolicyEngine |
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alias WalletLimitsFees.Events.PolicyDecisionCaptured |
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@doc """ |
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Calculates the fee for the given tier, currency, transfer type, and amount. |
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Returns `{:ok, fee_amount}` where fee_amount is 0 when no policy exists. |
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""" |
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@spec execute( |
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tier :: atom(), |
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currency :: String.t(), |
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transfer_type :: atom(), |
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amount :: non_neg_integer() |
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) :: {:ok, non_neg_integer()} |
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def execute(tier, currency, transfer_type, amount) do |
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result = PolicyEngine.calculate_fee(tier, currency, transfer_type, amount) |
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{:ok, fee} = result |
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emit_event( |
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PolicyDecisionCaptured.build(:fee_calculation, {:ok, fee}, |
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tier: tier, |
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currency: currency, |
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amount: amount, |
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details: %{transfer_type: transfer_type, fee: fee} |
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) |
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) |
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result |
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end |
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defp emit_event(event) do |
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pubsub = Application.get_env(:wallet_limits_fees, :pubsub, WalletWeb.PubSub) |
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apply(Phoenix.PubSub, :broadcast, [pubsub, "wallet_limits_fees:events", {:domain_event, event}]) |
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rescue |
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_ -> :ok |
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end |
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end |