Accrue.Connect.PlatformFee (accrue v0.3.0)

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Pure Accrue.Money math for platform fee computation.

Caller-inject semantics. This helper computes the platform fee amount as a value. It does NOT auto-apply to charges or transfers. Callers thread the result into application_fee_amount: on their own charge/transfer calls so the fee line is always auditable at the call site.

Computation order

Stripe's documented order of operations for a flat-rate platform fee (percent + fixed, optionally clamped):

  1. Percent component — gross * (percent / 100) in minor units, with banker's rounding (:half_even) at integer precision. Minor units are integer across all currencies, so this is currency-exponent agnostic: JPY (0-decimal), USD (2-decimal), and KWD (3-decimal) all round at the same integer boundary.
  2. Fixed component — if present, added verbatim (same currency).
  3. Floor clamp — if :min is present and the result is below it, raise to the min.
  4. Ceiling clamp — if :max is present and the result exceeds it, lower to the max.

Zero gross short-circuits to zero fee before any math.

Config

Opts override per-call; unset opts fall back to Accrue.Config.get!(:connect) |> Keyword.get(:platform_fee).

Summary

Types

opts()

Functions

compute(gross, opts \\ [])
compute!(gross, opts \\ [])

Bang variant. Raises on validation failure.

Types

opts()

@type opts() :: [
  percent: Decimal.t(),
  fixed: Accrue.Money.t() | nil,
  min: Accrue.Money.t() | nil,
  max: Accrue.Money.t() | nil
]

Functions

compute(gross, opts \\ [])

@spec compute(
  Accrue.Money.t(),
  keyword()
) :: {:ok, Accrue.Money.t()} | {:error, Exception.t()}

compute!(gross, opts \\ [])

@spec compute!(
  Accrue.Money.t(),
  keyword()
) :: Accrue.Money.t()

Bang variant. Raises on validation failure.