<?php

use PHPUnit\Framework\TestCase;

/**
 * CryptoTest — Pure logic tests for the Crypto class (AES-256-GCM).
 *
 * Requires a valid APP_KEY in app/.env (set up by bootstrap.php).
 */
class CryptoTest extends TestCase
{
    // ── Encrypt → Decrypt round-trip ──────────────────────────────────────────

    public function testEncryptDecryptRoundTrip(): void
    {
        $plain = 'Hello, World!';
        $enc = Crypto::encrypt($plain);
        $dec = Crypto::decrypt($enc);

        $this->assertSame($plain, $dec);
        $this->assertNotSame($plain, $enc, 'Ciphertext must differ from plaintext');
    }

    public function testEncryptDecryptWithUnicode(): void
    {
        $plain = 'émoji 🎉 — français & 日本語';
        $enc = Crypto::encrypt($plain);
        $dec = Crypto::decrypt($enc);

        $this->assertSame($plain, $dec);
    }

    public function testEncryptDecryptMultiline(): void
    {
        $plain = "Line 1\nLine 2\r\nLine 3\n\n";
        $enc = Crypto::encrypt($plain);
        $dec = Crypto::decrypt($enc);

        $this->assertSame($plain, $dec);
    }

    // ── Different plaintexts → different ciphertexts ──────────────────────────

    public function testDifferentPlaintextsProduceDifferentCiphertexts(): void
    {
        $a = Crypto::encrypt('alpha');
        $b = Crypto::encrypt('beta');

        $this->assertNotSame($a, $b);
    }

    public function testSamePlaintextProducesDifferentCiphertexts(): void
    {
        // IV is random every time — encrypting the same value twice should
        // never produce identical ciphertext (except in astronomically rare
        // collisions of a 12-byte IV).
        $a = Crypto::encrypt('same');
        $b = Crypto::encrypt('same');

        $this->assertNotSame($a, $b, 'IV randomness → ciphertexts must differ');
    }

    // ── isEncrypted() ─────────────────────────────────────────────────────────

    public function testIsEncryptedRecognizesEncryptedValue(): void
    {
        $enc = Crypto::encrypt('secret');
        $this->assertTrue(Crypto::isEncrypted($enc));
    }

    public function testIsEncryptedRejectsPlaintext(): void
    {
        $this->assertFalse(Crypto::isEncrypted('plaintext password'));
    }

    public function testIsEncryptedReturnsFalseForEmptyString(): void
    {
        $this->assertFalse(Crypto::isEncrypted(''));
    }

    public function testIsEncryptedRejectsInvalidBase64(): void
    {
        $this->assertFalse(Crypto::isEncrypted('not valid base64!!!'));
    }

    // ── Empty string ──────────────────────────────────────────────────────────

    public function testEncryptEmptyStringProducesCiphertext(): void
    {
        $enc = Crypto::encrypt('');
        $this->assertNotEmpty($enc, 'Encrypting empty string should still produce ciphertext');
        // Note: isEncrypted() returns false for the empty-string ciphertext
        // because the raw blob (IV+TAG+empty ciphertext) is exactly 28 bytes,
        // which is < IV_LEN + TAG_LEN + 1 (29). This is a known edge case.
        $raw = base64_decode($enc, true);
        $this->assertIsString($raw);
        $this->assertEquals(28, strlen($raw), 'IV(12) + TAG(16) + empty ciphertext(0)');
    }

    public function testDecryptEmptyStringReturnsEmpty(): void
    {
        $this->assertSame('', Crypto::decrypt(''));
    }

    // ── Invalid base64 input ──────────────────────────────────────────────────

    public function testDecryptInvalidBase64ReturnsInputGracefully(): void
    {
        // Legacy fallback: non-base64 strings are returned as-is
        $input = 'plaintext-legacy-password';
        $result = Crypto::decrypt($input);
        $this->assertSame($input, $result);
    }

    public function testDecryptTooShortBlobReturnsInputGracefully(): void
    {
        // Base64 blob that decodes to fewer bytes than IV + TAG + 1
        $tooShort = base64_encode('abc');
        $result = Crypto::decrypt($tooShort);
        $this->assertSame($tooShort, $result);
    }

    // ── Wrong key / tampering ─────────────────────────────────────────────────

    public function testDecryptWithTamperedCiphertextReturnsEmpty(): void
    {
        $enc = Crypto::encrypt('tamper me');
        $raw = base64_decode($enc, true);

        // Flip a byte inside the ciphertext portion (after IV + tag)
        $tamperOffset = 12 + 16; // after 12-byte IV + 16-byte tag
        $raw[$tamperOffset] = chr(ord($raw[$tamperOffset]) ^ 0xFF);

        $tampered = base64_encode($raw);
        $result = Crypto::decrypt($tampered);
        $this->assertSame('', $result, 'Tampered ciphertext must return empty string');
    }

    public function testDecryptValidBlobTamperedTagReturnsEmpty(): void
    {
        $enc = Crypto::encrypt('test');
        $raw = base64_decode($enc, true);

        // Tamper with the authentication tag (bytes 13-28, after the 12-byte IV)
        $raw[13] = chr(ord($raw[13]) ^ 0xFF);

        $tampered = base64_encode($raw);
        $result = Crypto::decrypt($tampered);

        $this->assertSame('', $result, 'Tag mismatch must return empty');
    }
}