<?php
declare(strict_types=1);

use PHPUnit\Framework\TestCase;

/**
 * Unit test: WPDO_Crypto AES-256-GCM v2 + AES-256-CBC v1 backward compat (v2.15.0).
 *
 * Verifies:
 *   - v2 GCM round-trip (encrypt/decrypt)
 *   - v2 GCM tamper detection (auth tag verification)
 *   - v1 CBC backward compat read
 *   - Plaintext passthrough
 *   - Empty input handling
 *   - Invalid input safe failure
 */
class CryptoV2Test extends TestCase {

	public static function setUpBeforeClass(): void {
		// Define WP auth constants for stable key derivation in tests.
		if ( ! defined( 'AUTH_KEY' ) ) {
			define( 'AUTH_KEY', 'test_auth_key_for_phpunit_long_enough_string_xxxxxxxxxxxxxxxx' );
		}
		if ( ! defined( 'SECURE_AUTH_SALT' ) ) {
			define( 'SECURE_AUTH_SALT', 'test_secure_auth_salt_for_phpunit_xxxxxxxxxxxxxxxxxxxxxxx' );
		}
	}

	// ── v2 GCM happy paths ───────────────────────────────────────────────────

	public function test_v2_round_trip_simple_string(): void {
		$plain     = 'https://hooks.slack.com/services/T00000000/B00000000/abc123';
		$encrypted = WPDO_Crypto::encrypt( $plain );

		$this->assertStringStartsWith( WPDO_Crypto::PREFIX_V2, $encrypted );
		$this->assertSame( $plain, WPDO_Crypto::decrypt( $encrypted ) );
	}

	public function test_v2_round_trip_unicode(): void {
		$plain     = '中文密碼 + emoji 🔐 + special chars !@#$%^&*()';
		$encrypted = WPDO_Crypto::encrypt( $plain );

		$this->assertSame( $plain, WPDO_Crypto::decrypt( $encrypted ) );
	}

	public function test_v2_round_trip_long_string(): void {
		$plain     = str_repeat( 'A', 4096 );
		$encrypted = WPDO_Crypto::encrypt( $plain );

		$this->assertSame( $plain, WPDO_Crypto::decrypt( $encrypted ) );
	}

	public function test_v2_each_encryption_produces_unique_ciphertext(): void {
		// Random IV → repeated encrypts of the same plaintext yield different blobs.
		$plain = 'identical plaintext';
		$ct1   = WPDO_Crypto::encrypt( $plain );
		$ct2   = WPDO_Crypto::encrypt( $plain );

		$this->assertNotSame( $ct1, $ct2, 'IV randomness should produce unique ciphertexts' );
		$this->assertSame( $plain, WPDO_Crypto::decrypt( $ct1 ) );
		$this->assertSame( $plain, WPDO_Crypto::decrypt( $ct2 ) );
	}

	// ── v2 GCM tamper detection ──────────────────────────────────────────────

	public function test_v2_tampered_ciphertext_returns_original(): void {
		$plain     = 'sensitive webhook url';
		$encrypted = WPDO_Crypto::encrypt( $plain );

		// Decode the base64 payload, flip the FIRST byte of the GCM auth tag
		// (which lives at offset 12 right after the IV), re-encode. This
		// guarantees a real ciphertext modification regardless of base64
		// alphabet (vs str_replace which can be a no-op for some random IVs).
		$prefix_len = strlen( WPDO_Crypto::PREFIX_V2 );
		$encoded    = substr( $encrypted, $prefix_len );
		$raw        = base64_decode( $encoded, true );
		$this->assertNotFalse( $raw, 'Setup precondition: ciphertext must be valid base64' );
		$raw[12]      = chr( ord( $raw[12] ) ^ 0x55 ); // flip 4 bits of the auth tag.
		$tampered     = WPDO_Crypto::PREFIX_V2 . base64_encode( $raw );

		$result = WPDO_Crypto::decrypt( $tampered );
		$this->assertNotSame( $plain, $result, 'Tampered GCM ciphertext must NOT decrypt to original plaintext' );
		$this->assertSame( $tampered, $result, 'On auth failure decrypt() must return original blob' );
	}

	public function test_v2_truncated_blob_safe_failure(): void {
		$encrypted = WPDO_Crypto::encrypt( 'some value' );
		// Truncate to less than min size (12 IV + 16 tag + 1 byte ciphertext).
		$truncated = substr( $encrypted, 0, strlen( WPDO_Crypto::PREFIX_V2 ) + 5 );

		// Should not throw; should return original.
		$result = WPDO_Crypto::decrypt( $truncated );
		$this->assertSame( $truncated, $result );
	}

	// ── v1 CBC backward compat ───────────────────────────────────────────────

	public function test_v1_legacy_blob_decrypts_successfully(): void {
		// Hand-craft a v1 CBC blob using the same key derivation.
		$plain = 'legacy webhook url from pre-v2.15';
		$key   = $this->derive_key();
		$iv    = random_bytes( 16 );
		$ct    = openssl_encrypt( $plain, 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv );
		$blob  = WPDO_Crypto::PREFIX_V1 . base64_encode( $iv . $ct );

		$this->assertSame( $plain, WPDO_Crypto::decrypt( $blob ) );
	}

	public function test_v1_blob_with_garbage_returns_original(): void {
		$bad = WPDO_Crypto::PREFIX_V1 . 'not_valid_base64!!!';
		$this->assertSame( $bad, WPDO_Crypto::decrypt( $bad ) );
	}

	// ── Plaintext passthrough ────────────────────────────────────────────────

	public function test_plaintext_passthrough(): void {
		$plain = 'https://example.com/raw';
		$this->assertSame( $plain, WPDO_Crypto::decrypt( $plain ) );
	}

	public function test_empty_input(): void {
		$this->assertSame( '', WPDO_Crypto::encrypt( '' ) );
		$this->assertSame( '', WPDO_Crypto::decrypt( '' ) );
	}

	// ── format_version ───────────────────────────────────────────────────────

	public function test_format_version_classification(): void {
		// Use option-API stubs from bootstrap.
		$GLOBALS['_wp_options']['test_v2_opt']    = WPDO_Crypto::encrypt( 'foo' );
		$GLOBALS['_wp_options']['test_plain_opt'] = 'plaintext_value';
		$GLOBALS['_wp_options']['test_empty_opt'] = '';

		// Hand-craft a v1 blob.
		$key                                   = $this->derive_key();
		$iv                                    = random_bytes( 16 );
		$ct                                    = openssl_encrypt( 'bar', 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv );
		$GLOBALS['_wp_options']['test_v1_opt'] = WPDO_Crypto::PREFIX_V1 . base64_encode( $iv . $ct );

		$this->assertSame( 'v2', WPDO_Crypto::format_version( 'test_v2_opt' ) );
		$this->assertSame( 'v1', WPDO_Crypto::format_version( 'test_v1_opt' ) );
		$this->assertSame( 'plaintext', WPDO_Crypto::format_version( 'test_plain_opt' ) );
		$this->assertSame( 'empty', WPDO_Crypto::format_version( 'test_empty_opt' ) );
		$this->assertSame( 'empty', WPDO_Crypto::format_version( 'nonexistent_opt' ) );
	}

	// ── migrate_option_v1_to_v2 ──────────────────────────────────────────────

	public function test_migrate_option_v1_to_v2_round_trip(): void {
		$plain = 'webhook to migrate';
		$key   = $this->derive_key();
		$iv    = random_bytes( 16 );
		$ct    = openssl_encrypt( $plain, 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv );
		$blob  = WPDO_Crypto::PREFIX_V1 . base64_encode( $iv . $ct );

		$GLOBALS['_wp_options']['migrate_test'] = $blob;

		$result = WPDO_Crypto::migrate_option_v1_to_v2( 'migrate_test' );
		$this->assertSame( 'migrated', $result );

		// After migration: v2 blob, decrypts to original plaintext.
		$this->assertSame( 'v2', WPDO_Crypto::format_version( 'migrate_test' ) );
		$this->assertSame( $plain, WPDO_Crypto::get_option( 'migrate_test' ) );
	}

	public function test_migrate_option_already_v2_is_noop(): void {
		$GLOBALS['_wp_options']['already_v2'] = WPDO_Crypto::encrypt( 'foo' );
		$result                                = WPDO_Crypto::migrate_option_v1_to_v2( 'already_v2' );
		$this->assertSame( 'already_v2', $result );
	}

	public function test_migrate_option_plaintext_skipped(): void {
		$GLOBALS['_wp_options']['plain_opt'] = 'just plaintext';
		$result                              = WPDO_Crypto::migrate_option_v1_to_v2( 'plain_opt' );
		$this->assertSame( 'plaintext_skipped', $result );
		// Original value preserved.
		$this->assertSame( 'just plaintext', $GLOBALS['_wp_options']['plain_opt'] );
	}

	public function test_migrate_option_empty_returns_empty(): void {
		$GLOBALS['_wp_options']['empty_opt'] = '';
		$result                              = WPDO_Crypto::migrate_option_v1_to_v2( 'empty_opt' );
		$this->assertSame( 'empty', $result );
	}

	// ── Helper ───────────────────────────────────────────────────────────────

	/**
	 * Replicates WPDO_Crypto::derived_key() to craft test fixtures.
	 *
	 * @return string 32 raw bytes.
	 */
	private function derive_key(): string {
		$salt = AUTH_KEY . SECURE_AUTH_SALT;
		return substr( hash_hmac( 'sha256', 'wpdo_notifier_secrets_v1', $salt, true ), 0, 32 );
	}
}