MPP.Methods.Tempo.SessionReceipt (mpp v0.6.1)

Session-intent receipt for Tempo — returned in the Payment-Receipt header for session/pay-as-you-go payments.

Extends the base MPP.Receipt contract with session-specific fields: channel_id, accepted_cumulative, spent, and the optional units / tx_hash. The reference field mirrors channel_id so this receipt satisfies the base receipt shape.

Serialized as base64url-encoded JSON (no padding) for transport. Wire keys are camelCase (challengeId, channelId, acceptedCumulative, txHash) to stay compatible with the mppx and mpp-rs reference SDKs. Optional fields are omitted from the wire JSON entirely when nil (not serialized as null).

Receipts only represent success. Session failures are communicated via HTTP 402 responses with RFC 9457 Problem Details (see MPP.Errors).

Fields

method — always "tempo"
intent — always "session"
status — always "success"
timestamp — RFC 3339 datetime string (set by new/1 from DateTime.utc_now/0 unless overridden)
reference — mirrors channel_id; satisfies the base receipt contract
challenge_id — challenge identifier
channel_id — payment channel identifier (hex)
accepted_cumulative — highest accepted cumulative voucher amount (decimal string; bigint wire format)
spent — amount spent in this session (decimal string)
units — optional integer, number of units consumed
tx_hash — optional settlement transaction hash (hex)

API Functions

Function	Arity	Description	Param Kinds
`from_header`	1	Decode a base64url JSON `Payment-Receipt` header value into a session receipt.	`encoded: value`
`to_header`	1	Encode a session receipt to a base64url JSON string (no padding) for the `Payment-Receipt` header.	`receipt: value`
`new`	1	Create a new Tempo session receipt with defaults for method/intent/status/timestamp.	`opts: value`

Summary

Types

t()

Functions

from_header(encoded)

Decode a base64url JSON Payment-Receipt header value into a session receipt.

new(opts)

Create a new Tempo session receipt with defaults for method/intent/status/timestamp.

to_header(receipt)

Encode a session receipt to a base64url JSON string (no padding) for the Payment-Receipt header.

Types

t()

@type t() :: %MPP.Methods.Tempo.SessionReceipt{
  accepted_cumulative: String.t(),
  challenge_id: String.t(),
  channel_id: String.t(),
  intent: String.t(),
  method: String.t(),
  reference: String.t(),
  spent: String.t(),
  status: String.t(),
  timestamp: String.t(),
  tx_hash: String.t() | nil,
  units: non_neg_integer() | nil
}

Functions

from_header(encoded)

@spec from_header(String.t()) :: {:ok, t()} | {:error, atom()}

Decode a base64url JSON Payment-Receipt header value into a session receipt.

Parameters

encoded - Base64url-encoded JSON session receipt string (value)

Returns

{:ok, receipt} on success, {:error, reason} on failure (tagged_tuple)

Errors

:invalid_base64
:invalid_json
:missing_required_fields
:invalid_field_type
:token_too_large

Composes With

to_header

# descripex:contract
%{
  params: %{
    encoded: %{
      description: "Base64url-encoded JSON session receipt string",
      kind: :value
    }
  },
  errors: [:invalid_base64, :invalid_json, :missing_required_fields,
   :invalid_field_type, :token_too_large],
  returns: %{
    type: :tagged_tuple,
    description: "`{:ok, receipt}` on success, `{:error, reason}` on failure"
  },
  composes_with: [:to_header]
}

new(opts)

@spec new(keyword()) :: t()

Create a new Tempo session receipt with defaults for method/intent/status/timestamp.

Parameters

opts - Keyword list with :challenge_id, :channel_id, :accepted_cumulative, :spent (all required), and optional :timestamp, :units, :tx_hash. :reference defaults to channel_id. (value)

Returns

SessionReceipt struct with method "tempo", intent "session", status "success", RFC 3339 timestamp, and reference mirroring channel_id (struct)

# descripex:contract
%{
  params: %{
    opts: %{
      description: "Keyword list with `:challenge_id`, `:channel_id`, `:accepted_cumulative`, `:spent` (all required), and optional `:timestamp`, `:units`, `:tx_hash`. `:reference` defaults to `channel_id`.",
      kind: :value
    }
  },
  returns: %{
    type: :struct,
    description: "SessionReceipt struct with method `\"tempo\"`, intent `\"session\"`, status `\"success\"`, RFC 3339 timestamp, and `reference` mirroring `channel_id`"
  }
}

to_header(receipt)

@spec to_header(t()) :: String.t()

Encode a session receipt to a base64url JSON string (no padding) for the Payment-Receipt header.

Parameters

receipt - SessionReceipt struct to encode (value)

Returns

Base64url-encoded JSON string (string)

Composes With

from_header

# descripex:contract
%{
  params: %{
    receipt: %{description: "SessionReceipt struct to encode", kind: :value}
  },
  returns: %{type: :string, description: "Base64url-encoded JSON string"},
  composes_with: [:from_header]
}