<?php
declare(strict_types=1);
namespace App\Tests;

use App\Repository\Pdo\PdoAuditRepository;
use PDO;
use PHPUnit\Framework\TestCase;

/**
 * Tamper-evidence of the audit log.
 *
 * Runs against real sqlite rather than a double: the whole property being tested is a property of
 * what actually gets written to a database, and a PHP reimplementation of the chain would only
 * ever prove that the test agrees with itself.
 */
final class AuditChainTest extends TestCase
{
    private PDO $pdo;

    protected function setUp(): void
    {
        if (!in_array('sqlite', PDO::getAvailableDrivers(), true)) {
            $this->markTestSkipped('pdo_sqlite not available on this host');
        }
        $this->pdo = new PDO('sqlite::memory:', null, null, [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        ]);
        $this->pdo->exec(<<<'SQL'
            CREATE TABLE move_audit_log (
                id          INTEGER PRIMARY KEY AUTOINCREMENT,
                actor       TEXT NOT NULL,
                action      TEXT NOT NULL,
                target      TEXT NOT NULL,
                before_json TEXT NOT NULL,
                after_json  TEXT NOT NULL,
                ts          INTEGER NOT NULL,
                prev_hash   TEXT,
                entry_hash  TEXT
            );
        SQL);
    }

    private function rows(): array
    {
        return $this->pdo->query('SELECT * FROM move_audit_log ORDER BY id ASC')->fetchAll();
    }

    /** The verifier's core loop, mirrored here so the property is asserted, not just the tool. */
    private function chainIsIntact(): bool
    {
        $expected = null;
        $started = false;
        foreach ($this->rows() as $r) {
            if ($r['entry_hash'] === null) { if ($started) return false; continue; }
            if ($started && $r['prev_hash'] !== $expected) return false;
            $started = true;
            $recomputed = PdoAuditRepository::hash(
                $r['actor'], $r['action'], $r['target'], $r['before_json'], $r['after_json'],
                (int)$r['ts'], $r['prev_hash'] !== null && $r['prev_hash'] !== '' ? $r['prev_hash'] : null
            );
            if (!hash_equals((string)$r['entry_hash'], $recomputed)) return false;
            $expected = $r['entry_hash'];
        }
        return true;
    }

    private function appendThree(): PdoAuditRepository
    {
        $repo = new PdoAuditRepository($this->pdo);
        $repo->append('kim', 'acknowledge', 'event:1', [], ['ok' => true]);
        $repo->append('lee', 'zone_delete', 'zone:abc', ['level' => 'restricted'], []);
        $repo->append('kim', 'threshold_set', 'threshold:pi-1:fall_prone_s', ['value' => '3'], ['value' => '5']);
        return $repo;
    }

    public function testEachEntryLinksToItsPredecessor(): void
    {
        $this->appendThree();
        $rows = $this->rows();
        $this->assertCount(3, $rows);
        $this->assertNull($rows[0]['prev_hash'], '첫 행은 사슬의 시작');
        $this->assertSame($rows[0]['entry_hash'], $rows[1]['prev_hash']);
        $this->assertSame($rows[1]['entry_hash'], $rows[2]['prev_hash']);
        $this->assertTrue($this->chainIsIntact());
    }

    public function testEditingARowBreaksTheChain(): void
    {
        $this->appendThree();
        // 감사 기록을 조용히 고치는 시나리오: 확인자를 바꿔치기한다.
        $this->pdo->exec("UPDATE move_audit_log SET actor = 'park' WHERE id = 2");
        $this->assertFalse($this->chainIsIntact(), '수정이 탐지되어야 한다');
    }

    public function testDeletingARowBreaksTheChain(): void
    {
        $this->appendThree();
        $this->pdo->exec('DELETE FROM move_audit_log WHERE id = 2');
        $this->assertFalse($this->chainIsIntact(), '삭제가 탐지되어야 한다');
    }

    public function testInsertingARowWithoutTheChainIsDetected(): void
    {
        $this->appendThree();
        // 애플리케이션을 우회해 직접 INSERT — 해시가 없다.
        $this->pdo->exec("INSERT INTO move_audit_log (actor, action, target, before_json, after_json, ts)
                          VALUES ('ghost', 'acknowledge', 'event:99', '[]', '[]', 1)");
        $this->assertFalse($this->chainIsIntact());
    }

    public function testRowsPredatingTheChainAreNotReportedAsDamage(): void
    {
        // 마이그레이션 이전 구간: 해시 없는 행이 앞에 쌓여 있다.
        $this->pdo->exec("INSERT INTO move_audit_log (actor, action, target, before_json, after_json, ts)
                          VALUES ('old', 'login', 'user:1', '[]', '[]', 1)");
        $this->appendThree();
        $this->assertTrue($this->chainIsIntact(),
            '정상 시스템이 매번 빨간불을 켜면 아무도 이 도구를 보지 않게 된다');
    }

    public function testAppendIsSafeWhenTheCallerAlreadyOwnsATransaction(): void
    {
        $repo = new PdoAuditRepository($this->pdo);
        $this->pdo->beginTransaction();
        $repo->append('kim', 'zone_save', 'zone:1', [], []);
        $this->pdo->commit();
        $this->assertCount(1, $this->rows());
        $this->assertTrue($this->chainIsIntact());
    }

    public function testFieldSeparatorCannotBeForgedByAValueContainingIt(): void
    {
        // '|' 구분자였다면 actor="a|b", action="c" 와 actor="a", action="b|c" 가 같은 해시를
        // 낳는다 — 감사 항목 위조가 성립한다. 0x1F 는 텍스트 필드에 나타나지 않는다.
        $a = PdoAuditRepository::hash('a|b', 'c', 't', '[]', '[]', 1, null);
        $b = PdoAuditRepository::hash('a', 'b|c', 't', '[]', '[]', 1, null);
        $this->assertNotSame($a, $b);
    }
}