Core types

Challenge, Credential, and Receipt primitives

These types map directly to HTTP headers—WWW-Authenticate, Authorization, and Payment-Receipt—and can be used independently of the higher-level client and server APIs.

use mpp::{PaymentChallenge, PaymentCredential, Receipt};

Parse a Challenge

Parse a WWW-Authenticate header into a typed PaymentChallenge:

use mpp::parse_www_authenticate;
 
let header = r#"Payment id="abc", realm="api.example.com", method="tempo", intent="charge", request="eyJhbW91bnQiOiIxMDAwIn0""#;
let challenge = parse_www_authenticate(header)?;
 
println!("Method: {}", challenge.method);
println!("Intent: {}", challenge.intent);

On the wire, request and optional opaque are base64url-encoded JSON strings in the WWW-Authenticate header. mpp-rs stores them as Base64UrlJson, so you can decode them when you need structured values.

Decode the base64url-encoded request to a typed struct:

use mpp::ChargeRequest;
 
let request: ChargeRequest = challenge.request.decode()?;
println!("Amount: {}", request.amount);

Create a Credential

Build a PaymentCredential from a Challenge echo and payment proof:

use mpp::{PaymentCredential, PaymentPayload, format_authorization};
 
let credential = PaymentCredential::with_source(
    challenge.to_echo(),
    "did:pkh:eip155:42431:0xa726a1...",
    PaymentPayload::transaction("0xf86c..."),
);
 
let header = format_authorization(&credential)?;
// header = "Payment eyJ..."

challenge.to_echo() preserves the original wire values. In the serialized Credential, challenge.request and challenge.opaque remain base64url strings inside the Authorization payload.

Parse a Receipt

Parse the Payment-Receipt response header:

use mpp::parse_receipt;
 
let receipt = parse_receipt(receipt_header)?;
println!("Status: {:?}", receipt.status);
println!("Reference: {}", receipt.reference);

Serialize a Receipt back to a header value:

use mpp::format_receipt;
 
let header = format_receipt(&receipt)?;

Type reference

Type	Description
`PaymentChallenge`	Server Challenge parsed from `WWW-Authenticate`
`PaymentCredential`	Client Credential for the `Authorization` header
`PaymentPayload`	Payment proof—either `transaction` (signed tx) or `hash` (tx hash)
`ChallengeEcho`	Echoed Challenge fields in a Credential
`Receipt`	Server Receipt parsed from `Payment-Receipt`
`ChargeRequest`	Decoded charge intent request data
`SessionRequest`	Decoded session intent request data
`Base64UrlJson`	JSON value encoded as base64url

Header functions

Function	Description
`format_authorization`	Serialize a Credential to an `Authorization` header value
`format_receipt`	Serialize a Receipt to a `Payment-Receipt` header value
`format_www_authenticate`	Serialize a Challenge to a `WWW-Authenticate` header value
`parse_authorization`	Parse an `Authorization` header into a Credential
`parse_receipt`	Parse a `Payment-Receipt` header into a Receipt
`parse_www_authenticate`	Parse a `WWW-Authenticate` header into a Challenge

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