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/*
* richard-atp-engine: A saturation-based automated theorem prover for first-order logic.
* Copyright (C) 2026 Richard Qin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "atp/core/clause.h"
#include "atp/core/clause_store.h"
#include "atp/core/literal.h"
#include "atp/core/symbol_table.h"
#include "atp/core/term_bank.h"
#include "atp/core/types.h"
#include "atp/proof/proof_trace.h"
#include "atp/search/prover.h"
#include <gtest/gtest.h>
#include <string>
namespace atp {
namespace {
class ProofTraceTest : public ::testing::Test {
protected:
SymbolTable symbols;
TermBank bank{symbols};
ClauseStore store;
SymbolId sym_a{}, sym_b{};
SymbolId sym_P{}, sym_Q{};
SymbolId sym_X{};
TermId a_term{}, b_term{}, X_term{};
void SetUp() override {
sym_a = symbols.intern("a", SymbolKind::kConstant);
sym_b = symbols.intern("b", SymbolKind::kConstant);
sym_P = symbols.intern("P", SymbolKind::kPredicate, 1);
sym_Q = symbols.intern("Q", SymbolKind::kPredicate, 1);
sym_X = symbols.intern("X", SymbolKind::kVariable);
a_term = bank.makeTerm(sym_a, {});
b_term = bank.makeTerm(sym_b, {});
X_term = bank.makeVar(sym_X);
}
TermId P(TermId arg) { return bank.makeTerm(sym_P, {{arg}}); }
TermId Q(TermId arg) { return bank.makeTerm(sym_Q, {{arg}}); }
Literal pos(TermId atom) { return {.atom = atom, .is_positive = true}; }
Literal neg(TermId atom) { return {.atom = atom, .is_positive = false}; }
Clause makeClause(std::vector<Literal> lits) {
Clause cl;
cl.literals = std::move(lits);
return cl;
}
};
// ═══════════════════════════════════════════════════════════════════════════
// termToString Tests
// ═══════════════════════════════════════════════════════════════════════════
TEST_F(ProofTraceTest, TermToStringConstant) {
EXPECT_EQ(termToString(a_term, bank), "a");
}
TEST_F(ProofTraceTest, TermToStringVariable) {
EXPECT_EQ(termToString(X_term, bank), "X");
}
TEST_F(ProofTraceTest, TermToStringCompound) {
TermId pa = P(a_term);
EXPECT_EQ(termToString(pa, bank), "P(a)");
}
TEST_F(ProofTraceTest, TermToStringNested) {
SymbolId sym_f = symbols.intern("f", SymbolKind::kFunction, 1);
TermId fa = bank.makeTerm(sym_f, {{a_term}});
TermId pfa = P(fa);
EXPECT_EQ(termToString(pfa, bank), "P(f(a))");
}
// ═══════════════════════════════════════════════════════════════════════════
// clauseToString Tests
// ═══════════════════════════════════════════════════════════════════════════
TEST_F(ProofTraceTest, ClauseToStringEmpty) {
Clause empty = makeClause({});
EXPECT_EQ(clauseToString(empty, bank), "□");
}
TEST_F(ProofTraceTest, ClauseToStringSinglePositive) {
Clause c = makeClause({pos(P(a_term))});
EXPECT_EQ(clauseToString(c, bank), "P(a)");
}
TEST_F(ProofTraceTest, ClauseToStringSingleNegative) {
Clause c = makeClause({neg(P(a_term))});
EXPECT_EQ(clauseToString(c, bank), "¬P(a)");
}
TEST_F(ProofTraceTest, ClauseToStringMultipleLiterals) {
Clause c = makeClause({neg(P(X_term)), pos(Q(X_term))});
std::string s = clauseToString(c, bank);
EXPECT_EQ(s, "¬P(X) ∨ Q(X)");
}
// ═══════════════════════════════════════════════════════════════════════════
// extractProof Tests
// ═══════════════════════════════════════════════════════════════════════════
TEST_F(ProofTraceTest, ExtractProofTrivial) {
// Run a trivial proof: {P(a)} + {¬P(a)} → □
Prover prover(bank, store);
prover.addClauses({makeClause({pos(P(a_term))}), makeClause({neg(P(a_term))})});
ProverResult result = prover.prove();
ASSERT_EQ(result, ProverResult::kTheorem);
auto eid = prover.getEmptyClauseId();
ASSERT_TRUE(eid.has_value());
auto proof = extractProof(store, *eid);
ASSERT_GE(proof.size(), 3u); // At least: 2 axioms + 1 empty clause
// First steps should be axioms (kInput)
EXPECT_EQ(proof.front().rule, InferenceRule::kInput);
// Last step should be the empty clause
EXPECT_EQ(proof.back().clause_id, *eid);
// Last step should be resolution
EXPECT_EQ(proof.back().rule, InferenceRule::kResolution);
}
TEST_F(ProofTraceTest, ExtractProofTwoStep) {
// {P(a)}, {¬P(X), Q(X)}, {¬Q(a)} → □ in 2 resolution steps
Prover prover(bank, store);
prover.addClauses({makeClause({pos(P(a_term))}), makeClause({neg(P(X_term)), pos(Q(X_term))}),
makeClause({neg(Q(a_term))})});
ProverResult result = prover.prove();
ASSERT_EQ(result, ProverResult::kTheorem);
auto eid = prover.getEmptyClauseId();
ASSERT_TRUE(eid.has_value());
auto proof = extractProof(store, *eid);
// Should have axioms + intermediate + empty clause
ASSERT_GE(proof.size(), 4u); // 3 axioms + at least 1 intermediate + empty
// Last step is the empty clause
EXPECT_EQ(proof.back().clause_id, *eid);
}
// ═══════════════════════════════════════════════════════════════════════════
// formatProof Tests
// ═══════════════════════════════════════════════════════════════════════════
TEST_F(ProofTraceTest, FormatProofContainsExpectedElements) {
Prover prover(bank, store);
prover.addClauses({makeClause({pos(P(a_term))}), makeClause({neg(P(a_term))})});
prover.prove();
auto eid = prover.getEmptyClauseId();
ASSERT_TRUE(eid.has_value());
auto proof = extractProof(store, *eid);
std::string output = formatProof(proof, store, bank);
// Should contain key elements
EXPECT_NE(output.find("input"), std::string::npos) << output;
EXPECT_NE(output.find("resolution"), std::string::npos) << output;
EXPECT_NE(output.find("P(a)"), std::string::npos) << output;
// Empty clause should appear
std::string empty_marker = "□";
EXPECT_NE(output.find(empty_marker), std::string::npos) << output;
}
TEST_F(ProofTraceTest, FormatProofNoParentsForAxioms) {
Prover prover(bank, store);
prover.addClauses({makeClause({pos(P(a_term))}), makeClause({neg(P(a_term))})});
prover.prove();
auto eid = prover.getEmptyClauseId();
auto proof = extractProof(store, *eid);
std::string output = formatProof(proof, store, bank);
// The first line (an axiom) should NOT have "[from ...]"
// Find the first newline
auto first_line = output.substr(0, output.find('\n'));
EXPECT_EQ(first_line.find("[from"), std::string::npos)
<< "Axiom should not have parent info: " << first_line;
}
} // namespace
} // namespace atp
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