essential-check 0.15.0

Core logic related to validating Essential state transitions.
Documentation 
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//! Items related to the validation of [`Predicate`]s.

use crate::sign::secp256k1;
#[cfg(feature = "tracing")]
use essential_hash::content_addr;
use essential_types::{contract, predicate::Predicate};
use thiserror::Error;

/// [`check_signed_contract`] error.
#[derive(Debug, Error)]
pub enum InvalidSignedContract {
    /// Failed to validate the signature over the contract.
    #[error("invalid signature: {0}")]
    Signature(#[from] secp256k1::Error),
    /// The contract was invalid.
    #[error("invalid contract: {0}")]
    Set(#[from] InvalidContract),
}

/// [`check_contract`] error.
#[derive(Debug, Error)]
pub enum InvalidContract {
    /// The number of predicates in the contract exceeds the limit.
    #[error("the number of predicates ({0}) exceeds the limit ({MAX_PREDICATES})")]
    TooManyPredicates(usize),
    /// The predicate at the given index was invalid.
    #[error("predicate at index {0} is invalid: {1}")]
    Predicate(usize, InvalidPredicate),
}

/// [`check`] error.
#[derive(Debug, Error)]
pub enum InvalidPredicate {
    /// The number of nodes in the predicate exceeds the limit.
    #[error(
        "the number of nodes ({0}) exceeds the limit ({})",
        Predicate::MAX_NODES
    )]
    TooManyNodes(usize),
    /// The number of edges in the predicate exceeds the limit.
    #[error(
        "the number of edges ({0}) exceeds the limit ({})",
        Predicate::MAX_EDGES
    )]
    TooManyEdges(usize),
}

/// Maximum number of predicates in a contract.
pub const MAX_PREDICATES: usize = 100;

/// Validate a signed contract of predicates.
///
/// Verifies the signature and then validates the contract.
#[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(addr = %content_addr(&signed_contract.contract)), err))]
pub fn check_signed_contract(
    signed_contract: &contract::SignedContract,
) -> Result<(), InvalidSignedContract> {
    essential_sign::contract::verify(signed_contract)?;
    check_contract(signed_contract.contract.as_ref())?;
    Ok(())
}

/// Validate a contract of predicates.
///
/// Checks the size of the contract and then validates each predicate.
pub fn check_contract(predicates: &[Predicate]) -> Result<(), InvalidContract> {
    if predicates.len() > MAX_PREDICATES {
        return Err(InvalidContract::TooManyPredicates(predicates.len()));
    }
    for (ix, predicate) in predicates.iter().enumerate() {
        check(predicate).map_err(|e| InvalidContract::Predicate(ix, e))?;
    }
    Ok(())
}

/// Validate a single predicate.
///
/// Validates the slots, state reads, and constraints.
pub fn check(predicate: &Predicate) -> Result<(), InvalidPredicate> {
    if predicate.nodes.len() > Predicate::MAX_NODES.into() {
        return Err(InvalidPredicate::TooManyNodes(predicate.nodes.len()));
    }
    if predicate.edges.len() > Predicate::MAX_EDGES.into() {
        return Err(InvalidPredicate::TooManyEdges(predicate.edges.len()));
    }
    // FIXME: Update this to check DAG validity.
    Ok(())
}