/*
 * Copyright (c) Camden Dixie O'Brien
 * SPDX-License-Identifier: AGPL-3.0-only
 */

#include "convert.h"
#include "testing.h"

static bool is_deterministic(const fsa_t *fsa)
{
	for (int i = 0; i < fsa->count; ++i) {
		bool seen[CHAR_COUNT] = { 0 };
		fsa_state_t *state = &fsa->states[i];
		for (int j = 0; j < state->count; ++j) {
			const int input = state->rules[j].input;
			if (EPSILON == input)
				return false;
			if (seen[input])
				return false;
			seen[input] = true;
		}
	}
	return true;
}

static bool accepts(const fsa_t *dfa, const char *input)
{
	int current = dfa->initial;
	while ('\0' != *input) {
		bool found = false;
		const fsa_rule_t *rules = dfa->states[current].rules;
		for (int i = 0; i < dfa->states[current].count; ++i) {
			if (rules[i].input == *input) {
				current = rules[i].next;
				found = true;
				break;
			}
		}
		if (!found)
			return false;
		++input;
	}
	return dfa->states[current].final;
}

static void test_trivial_case(void)
{
	fsa_t nfa;
	fsa_init(&nfa);
	const int a = nfa.initial;
	const int b = fsa_add_state(&nfa);
	nfa.states[b].final = true;
	fsa_add_rule(&nfa, a, b, 'a');

	fsa_t dfa;
	convert_to_dfa(&nfa, &dfa);

	ASSERT_TRUE(is_deterministic(&dfa));
	ASSERT_TRUE(accepts(&dfa, "a"));
	ASSERT_FALSE(accepts(&dfa, "aa"));
	ASSERT_FALSE(accepts(&dfa, "b"));

	fsa_free(&nfa);
	fsa_free(&dfa);
}

static void test_epsilon_move(void)
{
	fsa_t nfa;
	fsa_init(&nfa);
	const int a = nfa.initial;
	const int b = fsa_add_state(&nfa);
	const int c = fsa_add_state(&nfa);
	nfa.states[c].final = true;
	fsa_add_rule(&nfa, a, b, EPSILON);
	fsa_add_rule(&nfa, a, c, 'a');
	fsa_add_rule(&nfa, b, c, 'b');

	fsa_t dfa;
	convert_to_dfa(&nfa, &dfa);

	ASSERT_TRUE(is_deterministic(&dfa));
	ASSERT_TRUE(accepts(&dfa, "a"));
	ASSERT_TRUE(accepts(&dfa, "b"));
	ASSERT_FALSE(accepts(&dfa, "aa"));
	ASSERT_FALSE(accepts(&dfa, "bb"));
	ASSERT_FALSE(accepts(&dfa, "ab"));
	ASSERT_FALSE(accepts(&dfa, "ba"));
	ASSERT_FALSE(accepts(&dfa, "c"));

	fsa_free(&nfa);
	fsa_free(&dfa);
}

static void test_branch(void)
{
	fsa_t nfa;
	fsa_init(&nfa);
	const int a = nfa.initial;
	const int b = fsa_add_state(&nfa);
	const int c = fsa_add_state(&nfa);
	const int d = fsa_add_state(&nfa);
	nfa.states[d].final = true;
	fsa_add_rule(&nfa, a, b, 'a');
	fsa_add_rule(&nfa, a, c, 'a');
	fsa_add_rule(&nfa, b, d, 'b');
	fsa_add_rule(&nfa, c, d, 'a');

	fsa_t dfa;
	convert_to_dfa(&nfa, &dfa);

	ASSERT_TRUE(is_deterministic(&dfa));
	ASSERT_TRUE(accepts(&dfa, "aa"));
	ASSERT_TRUE(accepts(&dfa, "ab"));
	ASSERT_FALSE(accepts(&dfa, "a"));
	ASSERT_FALSE(accepts(&dfa, "aaa"));
	ASSERT_FALSE(accepts(&dfa, "abb"));
	ASSERT_FALSE(accepts(&dfa, "c"));
	ASSERT_FALSE(accepts(&dfa, "ac"));

	fsa_free(&nfa);
	fsa_free(&dfa);
}

static void test_nfa_a(void)
{
	fsa_t nfa;
	fsa_init(&nfa);
	const int a = nfa.initial;
	const int b = fsa_add_state(&nfa);
	const int c = fsa_add_state(&nfa);
	const int d = fsa_add_state(&nfa);
	nfa.states[c].final = true;
	nfa.states[d].final = true;
	fsa_add_rule(&nfa, a, b, 'a');
	fsa_add_rule(&nfa, a, c, EPSILON);
	fsa_add_rule(&nfa, b, b, 'b');
	fsa_add_rule(&nfa, b, d, 'b');
	fsa_add_rule(&nfa, c, b, EPSILON);
	fsa_add_rule(&nfa, c, d, 'a');
	fsa_add_rule(&nfa, d, c, 'a');

	fsa_t dfa;
	convert_to_dfa(&nfa, &dfa);

	ASSERT_TRUE(is_deterministic(&dfa));

	ASSERT_TRUE(accepts(&dfa, ""));
	ASSERT_TRUE(accepts(&dfa, "a"));
	ASSERT_TRUE(accepts(&dfa, "b"));
	ASSERT_TRUE(accepts(&dfa, "ab"));
	ASSERT_TRUE(accepts(&dfa, "ba"));
	ASSERT_TRUE(accepts(&dfa, "aaaab"));

	ASSERT_FALSE(accepts(&dfa, "aaab"));
	ASSERT_FALSE(accepts(&dfa, "aaaba"));
	ASSERT_FALSE(accepts(&dfa, "aaabb"));
	ASSERT_FALSE(accepts(&dfa, "aaaaab"));
	ASSERT_FALSE(accepts(&dfa, "aaaaaba"));
	ASSERT_FALSE(accepts(&dfa, "aaaaabb"));

	fsa_free(&nfa);
	fsa_free(&dfa);
}

static void test_nfa_b(void)
{
	fsa_t nfa;
	fsa_init(&nfa);
	const int a = nfa.initial;
	const int b = fsa_add_state(&nfa);
	const int c = fsa_add_state(&nfa);
	const int d = fsa_add_state(&nfa);
	nfa.states[c].final = true;
	fsa_add_rule(&nfa, a, b, 'a');
	fsa_add_rule(&nfa, a, c, EPSILON);
	fsa_add_rule(&nfa, b, c, EPSILON);
	fsa_add_rule(&nfa, c, b, 'b');
	fsa_add_rule(&nfa, c, d, 'a');
	fsa_add_rule(&nfa, d, b, 'a');

	fsa_t dfa;
	convert_to_dfa(&nfa, &dfa);

	ASSERT_TRUE(is_deterministic(&dfa));

	ASSERT_TRUE(accepts(&dfa, ""));
	ASSERT_TRUE(accepts(&dfa, "a"));
	ASSERT_TRUE(accepts(&dfa, "aaaaaa"));
	ASSERT_TRUE(accepts(&dfa, "b"));
	ASSERT_TRUE(accepts(&dfa, "bbbbb"));
	ASSERT_TRUE(accepts(&dfa, "aaaaaa"));
	ASSERT_TRUE(accepts(&dfa, "aaaaabaa"));
	ASSERT_TRUE(accepts(&dfa, "aaaaabaab"));

	ASSERT_FALSE(accepts(&dfa, "ba"));
	ASSERT_FALSE(accepts(&dfa, "aba"));
	ASSERT_FALSE(accepts(&dfa, "abab"));
	ASSERT_FALSE(accepts(&dfa, "aaaaaba"));
	ASSERT_FALSE(accepts(&dfa, "aaaaabaaa"));
	ASSERT_FALSE(accepts(&dfa, "aaaaabbaabbaaa"));

	fsa_free(&nfa);
	fsa_free(&dfa);
}

static void test_nfa_c(void)
{
	fsa_t nfa;
	fsa_init(&nfa);
	const int a = nfa.initial;
	const int b = fsa_add_state(&nfa);
	const int c = fsa_add_state(&nfa);
	const int d = fsa_add_state(&nfa);
	const int e = fsa_add_state(&nfa);
	nfa.states[e].final = true;
	fsa_add_rule(&nfa, a, b, 'a');
	fsa_add_rule(&nfa, a, c, 'a');
	fsa_add_rule(&nfa, a, d, 'b');
	fsa_add_rule(&nfa, b, b, 'a');
	fsa_add_rule(&nfa, b, d, 'b');
	fsa_add_rule(&nfa, b, e, EPSILON);
	fsa_add_rule(&nfa, d, b, 'a');
	fsa_add_rule(&nfa, d, c, 'b');
	fsa_add_rule(&nfa, d, d, 'a');
	fsa_add_rule(&nfa, e, a, 'b');

	fsa_t dfa;
	convert_to_dfa(&nfa, &dfa);

	ASSERT_TRUE(is_deterministic(&dfa));

	ASSERT_TRUE(accepts(&dfa, "a"));
	ASSERT_TRUE(accepts(&dfa, "aba"));
	ASSERT_TRUE(accepts(&dfa, "aaba"));
	ASSERT_TRUE(accepts(&dfa, "abaaba"));
	ASSERT_TRUE(accepts(&dfa, "ba"));
	ASSERT_TRUE(accepts(&dfa, "babba"));
	ASSERT_TRUE(accepts(&dfa, "baaa"));
	ASSERT_TRUE(accepts(&dfa, "baba"));
	ASSERT_TRUE(accepts(&dfa, "babaa"));

	ASSERT_FALSE(accepts(&dfa, ""));
	ASSERT_FALSE(accepts(&dfa, "ab"));
	ASSERT_FALSE(accepts(&dfa, "aab"));
	ASSERT_FALSE(accepts(&dfa, "abbab"));
	ASSERT_FALSE(accepts(&dfa, "b"));
	ASSERT_FALSE(accepts(&dfa, "bb"));
	ASSERT_FALSE(accepts(&dfa, "baaabab"));
	ASSERT_FALSE(accepts(&dfa, "aabababab"));

	fsa_free(&nfa);
	fsa_free(&dfa);
}

int main(void)
{
	TESTING_BEGIN();

	// Base cases
	test_trivial_case();
	test_epsilon_move();
	test_branch();

	// Compound cases
	test_nfa_a();
	test_nfa_b();
	test_nfa_c();

	return TESTING_END();
}