veripb 3.0.0

//! This file contains useful helper functions that can be used in multiple places for the checker.

use std::rc::Rc;

use veripb_formula::prelude::*;
use veripb_propagator::propagation_engine::PropagationEngine;

use crate::{
    context::{CORE, DERIVED},
    prelude::*,
};

/// Set up a new propagation engine for VeriPB.
#[inline]
pub fn new_veripb_propagation_engine() -> PropagationEngine {
    let mut propagation_engine = PropagationEngine::default();
    propagation_engine.add_set();
    propagation_engine.add_set();
    propagation_engine.add_set();
    propagation_engine.enable_back(CORE);
    propagation_engine.enable_back(DERIVED);
    propagation_engine
}

/// Check the given solution and return it as an assignment.
#[inline]
pub fn check_solution(
    context: &mut Context,
    database: &mut Database,
    solution: &Vec<Lit>,
) -> Result<Assignment<BooleanVar>, CheckingError> {
    let mut assignment = Assignment::from(solution).ok_or(CheckingError::SolutionIsConflicting)?;
    assignment.resize(context.var_names.len());

    database.update_unique_index(&mut context.propagation_engine)?;
    if solution_satisfies_all_constraints(database, &assignment)? {
        return Ok(assignment);
    }

    database.update_propagation_index(&mut context.propagation_engine)?;
    let assignment = context.propagation_engine.propagate_solution(
        solution,
        &context.var_names,
        context.args.trace_failed,
    )?;

    let used_vars = database.get_used_vars();
    for var_idx in used_vars {
        if assignment.get_value(var_idx) == BoolValue::Unassigned {
            return Err(CheckingError::SolutionNotComplete(
                context.var_names.get_name(var_idx).to_string(),
            ));
        }
    }
    Ok(assignment)
}

/// Check the given complete solution and return it as an assignment.
#[inline]
fn solution_satisfies_all_constraints(
    database: &mut Database,
    assignment: &Assignment<BooleanVar>,
) -> Result<bool, CheckingError> {
    for constraint in database.unique_constraints.iter() {
        if !constraint.is_satisfied(assignment) {
            if constraint.is_falsified(assignment) {
                return Err(CheckingError::SolutionFalsifyingConstraint(
                    constraint.get_some_id(),
                ));
            }
            return Ok(false);
        }
    }
    Ok(true)
}

/// Do a weak syntactic implication check. This weak implication check reflects what is supported as implication in the kernel format.
///
/// Returns the constraint ID of the constraint that implies `constraint`.
#[inline]
pub fn check_implication(
    prop_engine: &mut PropagationEngine,
    database: &mut Database,
    target: &Rc<DBConstraint>,
    hint: Option<isize>,
) -> Result<isize, CheckingError> {
    match hint {
        Some(hint) => {
            let entry = database.get_entry(hint)?;
            if !entry.implies(target) {
                return Err(CheckingError::not_implied(target, entry));
            }
            Ok(entry.get_some_id() as isize)
        }
        None => {
            database.update_unique_index(prop_engine)?;
            if let Some(constraint) = database.lookup(target) {
                return Ok(constraint.get_some_id() as isize);
            }

            for constraint in database.unique_constraints.iter() {
                if constraint.implies(target) {
                    return Ok(constraint.get_some_id() as isize);
                }
            }
            Err(CheckingError::not_implied_db(target, false))
        }
    }
}

/// Do the syntactic implication check with saturation.
///
/// This check is stronger than the syntactic implication check, since it can derive a constraint `target` from another constraint `source` by adding literal axioms to it, performing saturation and another round of adding literal axioms.
///
/// Already takes care to check if the `source` constraint is a core constraint in a core only subproof.
#[inline]
pub fn check_implication_strong(
    context: &mut Context,
    database: &mut Database,
    target: &Rc<DBConstraint>,
    hint: Option<isize>,
) -> Result<(), CheckingError> {
    let mut proof_buf = if let Some(elaborator) = context.elaborator.as_mut() {
        Some(&mut elaborator.proof_buf)
    } else {
        None
    };
    match hint {
        Some(hint) => {
            let index = database.normalize_id(hint);
            let entry = database.get_entry_usize(index as usize)?;
            if context.only_core && !entry.is_core_constraint_id(index as usize) {
                return Err(CheckingError::CoreSubproofUsingNonCoreConstraint(hint));
            }
            if !entry.implies_strong(target, &mut proof_buf, &context.var_names) {
                return Err(CheckingError::not_implied(target, entry));
            }
            Ok(())
        }
        None => {
            database.update_unique_index(&mut context.propagation_engine)?;
            if let Some(constraint) = database.lookup(target) {
                if !context.only_core || constraint.is_core_constraint() {
                    if let Some(proof_buf) = proof_buf {
                        proof_buf.push_str(
                            &constraint
                                .get_out_id(constraint.get_some_id())
                                .unwrap()
                                .to_string(),
                        );
                    }
                    return Ok(());
                }
            }

            if let Some(proof_buf) = proof_buf {
                for constraint in database.unique_constraints.iter() {
                    if (!context.only_core || constraint.is_core_constraint())
                        && constraint.implies_strong(
                            target,
                            &mut Some(proof_buf),
                            &context.var_names,
                        )
                    {
                        return Ok(());
                    }

                    proof_buf.clear();
                }
            } else {
                for constraint in database.unique_constraints.iter() {
                    if (!context.only_core || constraint.is_core_constraint())
                        && constraint.implies_strong(target, &mut None, &context.var_names)
                    {
                        return Ok(());
                    }
                }
            }

            Err(CheckingError::not_implied_db(target, context.only_core))
        }
    }
}