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defmodule WalletLimitsFees.FeePolicy do |
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@moduledoc """ |
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Struct representing a fee policy for a given tier, currency, and transfer type. |
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Supports flat fee, percentage fee (as a float), min, and max fee ceilings. |
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Versioned to support audit traceability per ADR 0011. |
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""" |
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alias WalletSharedKernel.TypedId |
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@valid_transfer_types [:internal, :p2p, :external] |
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@enforce_keys [ |
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:policy_id, :tier, :currency, :transfer_type, |
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:flat_fee, :percentage_fee, :min_fee, :max_fee, |
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:version, :active, :created_at, :updated_at |
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] |
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defstruct [ |
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:policy_id, :tier, :currency, :transfer_type, :created_at, :updated_at, |
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flat_fee: 0, |
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percentage_fee: 0.0, |
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min_fee: 0, |
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max_fee: 0, |
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version: 1, |
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active: true |
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] |
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@type t :: %__MODULE__{ |
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policy_id: String.t(), |
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tier: atom(), |
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currency: String.t(), |
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transfer_type: :internal | :p2p | :external, |
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flat_fee: non_neg_integer(), |
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percentage_fee: float(), |
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min_fee: non_neg_integer(), |
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max_fee: non_neg_integer(), |
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version: pos_integer(), |
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active: boolean(), |
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created_at: DateTime.t(), |
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updated_at: DateTime.t() |
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} |
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@doc "Creates a new fee policy." |
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@spec new(tier :: atom(), currency :: String.t(), transfer_type :: atom(), attrs :: map()) :: t() |
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def new(tier, currency, transfer_type, attrs \\ %{}) do |
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now = DateTime.utc_now() |
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%__MODULE__{ |
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policy_id: TypedId.generate("fp"), |
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tier: tier, |
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currency: currency, |
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transfer_type: transfer_type, |
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flat_fee: Map.get(attrs, :flat_fee, 0), |
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percentage_fee: Map.get(attrs, :percentage_fee, 0.0), |
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min_fee: Map.get(attrs, :min_fee, 0), |
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max_fee: Map.get(attrs, :max_fee, 0), |
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version: 1, |
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active: true, |
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created_at: now, |
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updated_at: now |
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} |
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end |
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@doc "Bumps version and applies new attribute values from a map." |
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@spec bump_version(t(), attrs :: map()) :: t() |
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def bump_version(%__MODULE__{} = policy, attrs) do |
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%{policy | |
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version: policy.version + 1, |
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updated_at: DateTime.utc_now(), |
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flat_fee: Map.get(attrs, :flat_fee, policy.flat_fee), |
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percentage_fee: Map.get(attrs, :percentage_fee, policy.percentage_fee), |
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min_fee: Map.get(attrs, :min_fee, policy.min_fee), |
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max_fee: Map.get(attrs, :max_fee, policy.max_fee) |
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} |
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end |
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@doc "Returns the list of valid transfer types." |
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def valid_transfer_types, do: @valid_transfer_types |
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end |