<?php
declare(strict_types=1);

use PHPUnit\Framework\TestCase;

/**
 * Unit tests for WPDO_Cache_Layer — Object Cache integration for Zone C (Cold).
 */
class CacheLayerTest extends TestCase {

	/** Rows returned by get_results() for the bulk-fetch query. */
	public static array $db_rows = [];

	/** Whether SHOW TABLES reports the cold table. */
	public static bool $table_exists = true;

	/** Queries that read the cold table (get_var / get_results on it). */
	public static int $cold_queries = 0;

	protected function setUp(): void {
		self::$db_rows        = [];
		self::$table_exists   = true;
		self::$cold_queries   = 0;
		$GLOBALS['_wp_cache'] = [];

		// Reset Schema Registry singleton.
		$ref = new ReflectionClass( WPDO_Schema_Registry::class );
		$ref->getProperty( 'instance' )->setValue( null, null );

		// The cold module is write-active unless a test says otherwise.
		$this->set_cold_module( 'dual_write' );
		WPDO_Schema_Manager::flush_table_exists_cache();

		$this->setup_wpdb_mock();
	}

	private function set_cold_module( string $state ): void {
		$GLOBALS['_wp_options']['wpdo_features'] = array( 'cold_hp_listing' => $state );
		$prop = new ReflectionProperty( WPDO_Feature_Flags::class, 'cache' );
		$prop->setValue( null, null );
	}

	private function setup_wpdb_mock(): void {
		global $wpdb;

		$wpdb = new class {
			public string $prefix = 'wp_';

			public function prepare( string $sql, ...$args ): string {
				$i = 0;
				return preg_replace_callback( '/%([sd])/', function ( $m ) use ( &$i, $args ) {
					$val = $args[ $i++ ] ?? '';
					return $m[1] === 'd' ? (string) (int) $val : "'" . addslashes( (string) $val ) . "'";
				}, $sql );
			}

			public function get_var( string $sql ): ?string {
				if ( preg_match( "/^SHOW TABLES LIKE '(.+)'$/", $sql, $m ) ) {
					return CacheLayerTest::$table_exists ? stripslashes( $m[1] ) : null;
				}
				if ( str_contains( $sql, 'wpdo_cold_' ) ) {
					++CacheLayerTest::$cold_queries;
				}
				return null;
			}
			public function get_row( string $sql, $output = OBJECT ) { return null; }
			public function insert( string $table, array $data, $format = null ): int|false { return 1; }
			public function update( string $table, array $data, array $where, $f = null, $wf = null ): int|false { return 1; }
			public function delete( string $table, array $where, $format = null ): int|false { return 1; }
			public function query( string $sql ): int|bool { return 1; }

			public function get_results( string $sql, $output = OBJECT ): array {
				if ( str_contains( $sql, 'wpdo_cold_' ) ) {
					++CacheLayerTest::$cold_queries;
				}
				return CacheLayerTest::$db_rows;
			}
		};
	}

	// ── Zero side effect while the cold module is not active ─────────────────

	public function test_prefetch_does_not_query_while_module_idle(): void {
		$this->register_cold_field();
		$this->set_cold_module( 'idle' );

		WPDO_Cache_Layer::prefetch( [ 1, 2 ], 'hp_listing' );

		$this->assertSame( 0, self::$cold_queries );
		$this->assertEmpty( $GLOBALS['_wp_cache'] );
	}

	public function test_warm_post_does_not_query_while_module_idle(): void {
		$this->register_cold_field();
		$this->set_cold_module( 'idle' );

		WPDO_Cache_Layer::warm_post( 20, 'hp_listing' );

		$this->assertSame( 0, self::$cold_queries );
	}

	public function test_no_query_when_cold_table_is_missing(): void {
		$this->register_cold_field();
		self::$table_exists = false;

		WPDO_Cache_Layer::prefetch( [ 1 ], 'hp_listing' );
		WPDO_Cache_Layer::warm_post( 1, 'hp_listing' );

		$this->assertSame( 0, self::$cold_queries );
	}

	// ── Helper: register cold field ──────────────────────────────────────────

	private function register_cold_field( string $post_type = 'hp_listing', string $meta_key = 'hp_description' ): void {
		WPDO_Schema_Registry::instance()->register( 'test', [
			'post_type' => $post_type,
			'meta_key'  => $meta_key,
			'zone'      => 'cold',
		] );
	}

	// ── prefetch() ───────────────────────────────────────────────────────────

	public function test_prefetch_returns_early_for_empty_post_ids(): void {
		$this->register_cold_field();
		WPDO_Cache_Layer::prefetch( [], 'hp_listing' );
		$this->assertEmpty( $GLOBALS['_wp_cache'] );
	}

	public function test_prefetch_returns_early_when_no_cold_keys_for_type(): void {
		// 'unknown_type' has no registered cold fields.
		WPDO_Cache_Layer::prefetch( [ 1, 2, 3 ], 'unknown_type' );
		$this->assertEmpty( $GLOBALS['_wp_cache'] );
	}

	public function test_prefetch_skips_already_cached_post_ids(): void {
		$this->register_cold_field();
		$group = 'wpdo_cold_hp_listing';

		// Pre-warm cache for post 1.
		$GLOBALS['_wp_cache'][ $group ]['cold_1'] = [ 'hp_description' => 'cached' ];

		// DB returns no extra rows — all were already cached.
		self::$db_rows = [];
		WPDO_Cache_Layer::prefetch( [ 1 ], 'hp_listing' );

		// Cache should remain unchanged (no new entry written).
		$this->assertSame( [ 'hp_description' => 'cached' ], $GLOBALS['_wp_cache'][ $group ]['cold_1'] );
	}

	public function test_prefetch_stores_fetched_data_in_cache(): void {
		$this->register_cold_field();
		self::$db_rows = [
			[ 'post_id' => '5', 'data' => json_encode( [ 'hp_description' => 'Fetched!' ] ) ],
		];

		WPDO_Cache_Layer::prefetch( [ 5 ], 'hp_listing' );

		$group  = 'wpdo_cold_hp_listing';
		$cached = $GLOBALS['_wp_cache'][ $group ]['cold_5'] ?? false;
		$this->assertIsArray( $cached );
		$this->assertSame( 'Fetched!', $cached['hp_description'] );
	}

	public function test_prefetch_stores_empty_array_for_post_with_no_cold_row(): void {
		$this->register_cold_field();
		// DB returns nothing for post 7.
		self::$db_rows = [];

		WPDO_Cache_Layer::prefetch( [ 7 ], 'hp_listing' );

		$group  = 'wpdo_cold_hp_listing';
		$cached = $GLOBALS['_wp_cache'][ $group ]['cold_7'] ?? 'NOT_SET';
		$this->assertSame( [], $cached );
	}

	// ── warm_post() ──────────────────────────────────────────────────────────

	public function test_warm_post_returns_early_when_no_cold_keys(): void {
		// 'no_cold_type' has no cold fields → warm_post returns immediately.
		WPDO_Cache_Layer::warm_post( 1, 'no_cold_type' );
		$this->assertEmpty( $GLOBALS['_wp_cache'] );
	}

	public function test_warm_post_clears_stale_cache_entry(): void {
		$this->register_cold_field();
		$group     = 'wpdo_cold_hp_listing';
		$cache_key = 'cold_20';

		// Pre-populate with stale data.
		$GLOBALS['_wp_cache'][ $group ][ $cache_key ] = [ 'stale' => true ];

		WPDO_Cache_Layer::warm_post( 20, 'hp_listing' );

		// Stale cache must be replaced (warm_post deletes then re-reads from DB,
		// which returns null in mock, yielding empty array).
		$this->assertNotSame( [ 'stale' => true ], $GLOBALS['_wp_cache'][ $group ][ $cache_key ] ?? null );
	}

	/**
	 * Flushing bumps the post type's cache version instead of asking the
	 * object cache to scan the group (a server-side script on Redis that
	 * blocks it on a large group); older entries expire by their TTL.
	 */
	public function test_flush_group_moves_to_new_keys_without_a_group_flush(): void {
		$group                                   = 'wpdo_cold_hp_listing';
		$old_key                                 = WPDO_Zone_Cold::cache_key( 1, 'hp_listing' );
		$GLOBALS['_wp_cache'][ $group ][ $old_key ] = array( 'stale' => true );

		WPDO_Cache_Layer::flush_group( 'hp_listing' );

		$new_key = WPDO_Zone_Cold::cache_key( 1, 'hp_listing' );
		$this->assertNotSame( $old_key, $new_key );
		$this->assertFalse( wp_cache_get( $new_key, $group ) );
		$this->assertSame( 'cold_2', WPDO_Zone_Cold::cache_key( 2, 'other_type' ), 'other post types keep their keys' );
		$this->assertArrayHasKey( $old_key, $GLOBALS['_wp_cache'][ $group ], 'nothing scanned or deleted' );
	}

	// ── get_stats() ──────────────────────────────────────────────────────────

	public function test_get_stats_includes_required_keys(): void {
		$stats = WPDO_Cache_Layer::get_stats();

		$this->assertArrayHasKey( 'groups', $stats );
		$this->assertArrayHasKey( 'prefetch_support', $stats );
		$this->assertArrayHasKey( 'flush_support', $stats );
	}

	public function test_get_stats_groups_reflect_registered_cold_types(): void {
		$this->register_cold_field( 'hp_listing', 'hp_description' );
		$this->register_cold_field( 'hp_listing', 'hp_website' );

		$stats      = WPDO_Cache_Layer::get_stats();
		$post_types = array_column( $stats['groups'], 'post_type' );
		$this->assertContains( 'hp_listing', $post_types );
	}
}