<?php
/**
 * TMDO_Demo_Entity_Counter — production proof-of-life for entity adapters.
 *
 * Task D follow-up to PR-5: demonstrates that the entity adapter framework
 * actually works end-to-end (not just stubs). Implements a "counter" pattern
 * shared across post / user / term / comment entities — a common gamification
 * primitive (user points, listing views, comment helpful_count, term usage).
 *
 * Storage:
 *   wp_wpdo_demo_entity_counters (entity_type, entity_id, counter_key, counter_value, updated_at)
 *
 * Lifecycle:
 *   - Plugin or test invokes ::set( 'user', 42, 'points', 50 )
 *   - This writes to BOTH wp_usermeta (native, preserved) AND wpdo_demo table
 *   - Reads come from wpdo_demo when feature flag entity_demo_counter == 'cutover',
 *     otherwise fall through to native usermeta (transparent fallback)
 *
 * @package WP_Data_Optimizer
 * @since   2.0.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

// phpcs:disable Squiz.Commenting.FunctionComment.Missing,Squiz.Commenting.InlineComment.InvalidEndChar,Generic.Commenting.DocComment.MissingShort,WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.PHP.YodaConditions,Generic.CodeAnalysis.EmptyStatement -- v2.0.0 partner integrations: pure registration helpers + intentional silent catches.

/**
 * Demo entity counter — proves 4-entity adapter framework works end-to-end.
 */
final class TMDO_Demo_Entity_Counter {

	/** Feature flag module name. */
	public const MODULE = 'entity_demo_counter';

	/** Custom table holding all counters. */
	public const TABLE = 'wpdo_demo_entity_counters';

	/**
	 * Idempotent install of the demo table.
	 *
	 * Called from TMDO_Installer::install_v2_tables() OR manually for demos.
	 *
	 * @return void
	 */
	public static function install_table(): void {
		global $wpdb;
		if ( ! function_exists( 'dbDelta' ) ) {
			require_once ABSPATH . 'wp-admin/includes/upgrade.php';
		}

		$charset = $wpdb->get_charset_collate();
		$table   = $wpdb->prefix . self::TABLE;

		$sql = "CREATE TABLE {$table} (
  id bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  entity_type varchar(20) NOT NULL DEFAULT '',
  entity_id bigint(20) unsigned NOT NULL DEFAULT 0,
  counter_key varchar(100) NOT NULL DEFAULT '',
  counter_value bigint(20) NOT NULL DEFAULT 0,
  updated_at datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (id),
  UNIQUE KEY ui_entity_counter (entity_type, entity_id, counter_key),
  KEY idx_lookup (entity_type, counter_key, counter_value),
  KEY idx_entity (entity_type, entity_id)
) {$charset};";
		dbDelta( $sql );
	}

	/**
	 * Drop the demo table — idempotent.
	 *
	 * @return void
	 */
	public static function drop_table(): void {
		global $wpdb;
		$table = $wpdb->prefix . self::TABLE;
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
		$wpdb->query( "DROP TABLE IF EXISTS `{$table}`" );
	}

	/**
	 * Set a counter for any entity. Writes to BOTH native meta AND demo table
	 * when feature flag is in a write-active state. Otherwise writes native
	 * only (idle path — full backward compatibility).
	 *
	 * @param string $entity_type One of: post, user, term, comment.
	 * @param int    $entity_id   Entity ID.
	 * @param string $counter_key Counter slug (e.g. 'points', 'view_count').
	 * @param int    $value       New value.
	 * @return bool
	 */
	public static function set( string $entity_type, int $entity_id, string $counter_key, int $value ): bool {
		if ( ! self::is_valid_entity( $entity_type ) ) {
			return false;
		}

		// Always write the native meta first (durability anchor).
		TMDO_API::set_entity( $entity_type, $entity_id, $counter_key, $value );

		// Conditional dual-write to demo table.
		if ( TMDO_Feature_Flags::is_write_active( self::MODULE ) ) {
			self::write_to_table( $entity_type, $entity_id, $counter_key, $value );
		}

		return true;
	}

	/**
	 * Read a counter value. Source depends on feature flag state:
	 *   - read_custom (cutover/cleanup/complete) → demo table
	 *   - otherwise → native meta (fallback)
	 *
	 * @param string $entity_type One of: post, user, term, comment.
	 * @param int    $entity_id   Entity ID.
	 * @param string $counter_key Counter slug.
	 * @return int
	 */
	public static function get( string $entity_type, int $entity_id, string $counter_key ): int {
		if ( ! self::is_valid_entity( $entity_type ) ) {
			return 0;
		}

		if ( TMDO_Feature_Flags::is_read_custom( self::MODULE ) ) {
			$row = self::read_from_table( $entity_type, $entity_id, $counter_key );
			if ( null !== $row ) {
				return (int) $row;
			}
			// Fallback to native if zone row missing — graceful degradation.
		}

		return (int) TMDO_API::get_entity( $entity_type, $entity_id, $counter_key );
	}

	/**
	 * Top-N entities by counter value — the killer query that postmeta CANNOT
	 * do efficiently (requires full scan + filesort). Demonstrates the value of
	 * the entity adapter pattern.
	 *
	 * @param string $entity_type One of: post, user, term, comment.
	 * @param string $counter_key Counter slug.
	 * @param int    $limit       Max rows.
	 * @return array<int, array{entity_id:int, counter_value:int}>
	 */
	public static function top_n( string $entity_type, string $counter_key, int $limit = 10 ): array {
		global $wpdb;
		$table = $wpdb->prefix . self::TABLE;

		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- table name from constant.
		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT entity_id, counter_value FROM `{$table}` WHERE entity_type = %s AND counter_key = %s ORDER BY counter_value DESC LIMIT %d",
				$entity_type,
				$counter_key,
				$limit
			),
			ARRAY_A
		);

		return array_map(
			static fn( array $r ) => array(
				'entity_id'     => (int) $r['entity_id'],
				'counter_value' => (int) $r['counter_value'],
			),
			$rows ?: array()
		);
	}

	// ── Internals ──────────────────────────────────────────────────────────

	/**
	 * @param string $entity_type Entity type.
	 */
	private static function is_valid_entity( string $entity_type ): bool {
		return in_array( $entity_type, array( 'post', 'user', 'term', 'comment' ), true );
	}

	/**
	 * Write a single counter value via UPSERT (1 round-trip).
	 *
	 * @param string $entity_type One of: post, user, term, comment.
	 * @param int    $entity_id   Entity ID.
	 * @param string $counter_key Counter slug.
	 * @param int    $value       New value.
	 * @return void
	 */
	private static function write_to_table( string $entity_type, int $entity_id, string $counter_key, int $value ): void {
		global $wpdb;
		TMDO_DB::upsert(
			$wpdb->prefix . self::TABLE,
			array(
				'entity_type'   => $entity_type,
				'entity_id'     => $entity_id,
				'counter_key'   => $counter_key,
				'counter_value' => $value,
				'updated_at'    => current_time( 'mysql' ),
			),
			array( 'counter_value', 'updated_at' ),
			array( 'entity_type', 'entity_id', 'counter_key' ),
			array( '%s', '%d', '%s', '%d', '%s' )
		);
	}

	/**
	 * Read a single counter value from the demo table.
	 *
	 * @param string $entity_type Entity type.
	 * @param int    $entity_id   Entity ID.
	 * @param string $counter_key Counter slug.
	 * @return int|null Null when row absent.
	 */
	private static function read_from_table( string $entity_type, int $entity_id, string $counter_key ): ?int {
		global $wpdb;
		$table = $wpdb->prefix . self::TABLE;
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- table from constant.
		$value = $wpdb->get_var(
			$wpdb->prepare(
				"SELECT counter_value FROM `{$table}` WHERE entity_type = %s AND entity_id = %d AND counter_key = %s LIMIT 1",
				$entity_type,
				$entity_id,
				$counter_key
			)
		);
		return null === $value ? null : (int) $value;
	}
}