# 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. ```rust use mpp::{PaymentChallenge, PaymentCredential, Receipt}; ``` ## Parse a Challenge Parse a `WWW-Authenticate` header into a typed `PaymentChallenge`: ```rust 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); ``` Decode the base64url-encoded request to a typed struct: ```rust 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: ```rust 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..." ``` ## Parse a Receipt Parse the `Payment-Receipt` response header: ```rust 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: ```rust 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 |