x402-rs 0.12.2

//! Local facilitator implementation for x402 payments.
//!
//! This module provides [`FacilitatorLocal`], a [`Facilitator`] implementation that
//! validates x402 payment payloads and performs on-chain settlements using the
//! registered scheme handlers.
//!
//! # Architecture
//!
//! The local facilitator delegates payment processing to scheme handlers registered
//! in a [`SchemeRegistry`]. Each handler is responsible for:
//!
//! - Verifying payment signatures and requirements
//! - Checking on-chain balances
//! - Executing settlement transactions
//!
//! # Example
//!
//! ```ignore
//! use x402::facilitator_local::FacilitatorLocal;
//! use x402::scheme::SchemeRegistry;
//!
//! let registry = SchemeRegistry::build(chains, blueprints, &config);
//! let facilitator = FacilitatorLocal::new(registry);
//! ```

use std::collections::HashMap;

use crate::facilitator::Facilitator;
use crate::proto;
use crate::proto::PaymentVerificationError;
use crate::scheme::{SchemeRegistry, X402SchemeFacilitatorError};

/// A local [`Facilitator`] implementation that delegates to scheme handlers.
///
/// This type wraps a [`SchemeRegistry`] and routes payment verification and
/// settlement requests to the appropriate scheme handler based on the payment's
/// chain ID and scheme name.
///
/// # Type Parameter
///
/// - `A` - The handler registry type (typically [`SchemeRegistry`])
pub struct FacilitatorLocal<A> {
    handlers: A,
}

impl<A> FacilitatorLocal<A> {
    /// Creates a new [`FacilitatorLocal`] with the given scheme handler registry.
    pub fn new(handlers: A) -> Self {
        FacilitatorLocal { handlers }
    }
}

impl Facilitator for FacilitatorLocal<SchemeRegistry> {
    type Error = FacilitatorLocalError;

    async fn verify(
        &self,
        request: &proto::VerifyRequest,
    ) -> Result<proto::VerifyResponse, Self::Error> {
        let handler = request
            .scheme_handler_slug()
            .and_then(|slug| self.handlers.by_slug(&slug))
            .ok_or(FacilitatorLocalError::Verification(
                PaymentVerificationError::UnsupportedScheme.into(),
            ))?;
        let response = handler
            .verify(request)
            .await
            .map_err(FacilitatorLocalError::Verification)?;
        Ok(response)
    }

    async fn settle(
        &self,
        request: &proto::SettleRequest,
    ) -> Result<proto::SettleResponse, Self::Error> {
        let handler = request
            .scheme_handler_slug()
            .and_then(|slug| self.handlers.by_slug(&slug))
            .ok_or(FacilitatorLocalError::Verification(
                PaymentVerificationError::UnsupportedScheme.into(),
            ))?;
        let response = handler
            .settle(request)
            .await
            .map_err(FacilitatorLocalError::Settlement)?;
        Ok(response)
    }

    async fn supported(&self) -> Result<proto::SupportedResponse, Self::Error> {
        let mut kinds = vec![];
        let mut signers = HashMap::new();
        for provider in self.handlers.values() {
            let supported = provider.supported().await.ok();
            if let Some(mut supported) = supported {
                kinds.append(&mut supported.kinds);
                for (chain_id, signer_addresses) in supported.signers {
                    signers.entry(chain_id).or_insert(signer_addresses);
                }
            }
        }
        Ok(proto::SupportedResponse {
            kinds,
            extensions: Vec::new(),
            signers,
        })
    }
}

/// Errors that can occur during local facilitator operations.
#[derive(Debug, thiserror::Error)]
pub enum FacilitatorLocalError {
    /// Payment verification failed.
    #[error(transparent)]
    Verification(X402SchemeFacilitatorError),
    /// Payment settlement failed.
    #[error(transparent)]
    Settlement(X402SchemeFacilitatorError),
}