<?php
/**
 * TMDO_V2_Upgrader — atomic v1.3.x → v2.0.0 upgrade orchestrator (PR-7).
 *
 * Implements the Part F upgrade strategy from the master plan:
 *   1. Pre-flight: PHP / WP / MySQL versions, free disk, no in-flight migrations
 *   2. Backup wpdo_features option (rollback safety net)
 *   3. dbDelta v2 tables (idempotent)
 *   4. ALTER existing tables (skip if already migrated)
 *   5. UAE import (when wp_uae_* present, otherwise no-op)
 *   6. migrate_feature_flags_v2 — seed entity module states
 *   7. update wpdo_db_version → 2.0.0
 *   8. safely_deactivate_uae_plugin (when present)
 *   9. Schedule cron to remove the UAE plugin directory (5s)
 *  10. fire wpdo_v2_upgraded action
 *
 * Any throw → catch → write wpdo_v2_upgrade_error → restore features → admin
 * notice. New tables are NOT dropped on failure (idempotent retry).
 *
 * @package WP_Data_Optimizer
 * @since   2.0.0
 */

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

/**
 * Atomic upgrade orchestrator.
 */
final class TMDO_V2_Upgrader {

	/** Target schema version after successful upgrade. */
	public const TARGET_VERSION = '2.0.0';

	/** Min PHP / WP / MySQL versions enforced by pre-flight. */
	public const MIN_PHP_VERSION   = '8.1';
	public const MIN_WP_VERSION    = '6.0';
	public const MIN_MYSQL_VERSION = '5.7';

	/** Free-disk threshold in MB. */
	public const MIN_FREE_DISK_MB = 100;

	/**
	 * Pre-flight check — returns map of check_name => bool.
	 *
	 * @param array $opts Optional overrides (mostly for tests).
	 * @return array<string,bool>
	 */
	public static function pre_flight_check( array $opts = array() ): array {
		global $wpdb;

		$wp_version    = $opts['wp_version'] ?? ( defined( 'ABSPATH' ) ? ( get_bloginfo( 'version' ) ?: '6.0' ) : '6.0' );
		$mysql_version = $opts['mysql_version'] ?? self::detect_mysql_version();
		$disk_path     = $opts['disk_path'] ?? sys_get_temp_dir();

		$checks = array(
			'php_version'         => version_compare( PHP_VERSION, self::MIN_PHP_VERSION, '>=' ),
			'wp_version'          => version_compare( $wp_version, self::MIN_WP_VERSION, '>=' ),
			'mysql_version'       => version_compare( $mysql_version, self::MIN_MYSQL_VERSION, '>=' ),
			'free_disk_mb'        => self::detect_free_disk_mb( $disk_path ) >= self::MIN_FREE_DISK_MB,
			'features_writable'   => self::is_features_option_writable(),
			'no_active_migration' => self::no_active_migration(),
		);

		return $checks;
	}

	/**
	 * Run the atomic upgrade. Returns true on success, false on failure.
	 *
	 * @return bool
	 * @throws \RuntimeException When UAE importer fails (caught internally and rolled back).
	 */
	public static function upgrade_to_v2(): bool {
		// 1. Pre-flight check.
		$checks = self::pre_flight_check();
		if ( in_array( false, $checks, true ) ) {
			update_option(
				'wpdo_v2_upgrade_error',
				'Pre-flight check failed: ' . wp_json_encode( $checks ),
				false
			);
			update_option( 'wpdo_v2_upgrade_status', 'preflight_failed', false );
			return false;
		}

		update_option( 'wpdo_v2_upgrade_started_at', time(), false );
		update_option( 'wpdo_v2_upgrade_status', 'in_progress', false );

		$features_backup = get_option( 'wpdo_features', array() );
		update_option( 'wpdo_v2_features_backup', $features_backup, false );

		try {
			// 4. Install v2 tables.
			TMDO_Installer::install_v2_tables();

			// 5. UAE import (when applicable).
			if ( self::detect_uae_data() ) {
				$import_ok = self::run_uae_import();
				if ( ! $import_ok ) {
					throw new \RuntimeException( 'UAE importer failed' );
				}
			}

			// 6. Migrate feature flags to include entity modules.
			self::migrate_feature_flags_v2();

			// 7. Bump db_version.
			update_option( 'wpdo_db_version', self::TARGET_VERSION, false );
			update_option( 'wpdo_v2_upgrade_status', 'complete', false );
			update_option( 'wpdo_v2_upgraded_at', time(), false );

			// 8. Safely deactivate UAE plugin.
			self::safely_deactivate_uae_plugin();

			// 9. Schedule plugin directory removal.
			self::schedule_uae_dir_removal();

			// 10. Fire hook for downstream consumers.
			do_action( 'wpdo_v2_upgraded', '1.3.38', self::TARGET_VERSION );

			return true;

		} catch ( \Throwable $e ) {
			// Rollback path: restore features option, leave new tables in place
			// (idempotent retry on next attempt).
			update_option( 'wpdo_features', $features_backup );
			update_option( 'wpdo_v2_upgrade_error', $e->getMessage(), false );
			update_option( 'wpdo_v2_upgrade_status', 'failed', false );
			return false;
		}
	}

	/**
	 * Roll back from a partially-completed v2 upgrade.
	 *
	 * @param bool $keep_data When true, retain wpdo_uni_* tables (for retry).
	 * @return bool
	 */
	public static function rollback_v2( bool $keep_data = true ): bool {
		$backup = get_option( 'wpdo_v2_features_backup' );
		if ( false !== $backup ) {
			update_option( 'wpdo_features', $backup );
		}
		update_option( 'wpdo_db_version', '1.0.0', false );
		update_option( 'wpdo_v2_upgrade_status', 'rolled_back', false );

		if ( ! $keep_data ) {
			global $wpdb;
			foreach ( array( 'wpdo_audit', 'wpdo_shadow_diffs', 'wpdo_site_metrics', 'wpdo_uni_options' ) as $t ) {
				// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared,WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- $t from hardcoded array, $wpdb->prefix sanitized by core.
				$wpdb->query( "DROP TABLE IF EXISTS `{$wpdb->prefix}{$t}`" );
			}
		}

		return true;
	}

	// ── Helpers ─────────────────────────────────────────────────────────────

	/**
	 * Detect whether wp_uae_* tables exist (S3 scenario).
	 */
	public static function detect_uae_data(): bool {
		global $wpdb;
		$count = (int) $wpdb->get_var(
			$wpdb->prepare(
				'SELECT COUNT(*) FROM information_schema.TABLES WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME LIKE %s',
				$wpdb->prefix . 'uae_%'
			)
		);
		return $count > 0;
	}

	/**
	 * Run the UAE → WPDO data importer. Stub for v2.0.0 — full implementation
	 * lives in includes/migration/class-tmdo-uae-importer.php (PR-7 follow-up).
	 *
	 * @return bool
	 */
	public static function run_uae_import(): bool {
		if ( class_exists( 'TMDO_UAE_Importer' ) ) {
			return TMDO_UAE_Importer::run(
				array(
					'auto'        => true,
					'keep_source' => true,
				)
			);
		}
		// No UAE importer yet — return true so dev10 (no UAE data) progresses.
		return true;
	}

	/**
	 * Migrate the feature_flags option to include entity modules.
	 */
	public static function migrate_feature_flags_v2(): void {
		$flags = get_option( 'wpdo_features', array() );
		if ( ! is_array( $flags ) ) {
			$flags = array();
		}
		foreach ( array( 'entity_user', 'entity_term', 'entity_comment', 'entity_options' ) as $module ) {
			if ( ! isset( $flags[ $module ] ) ) {
				$flags[ $module ] = 'idle';
			}
		}
		update_option( 'wpdo_features', $flags );
	}

	/**
	 * Detect installed MySQL / MariaDB version via @@version.
	 */
	public static function detect_mysql_version(): string {
		global $wpdb;
		try {
			$v = (string) $wpdb->get_var( 'SELECT VERSION()' );
			// Strip trailing -MariaDB or similar tags for version_compare.
			if ( preg_match( '/^([\d.]+)/', $v, $m ) ) {
				return $m[1];
			}
		} catch ( \Throwable $e ) { // phpcs:ignore Generic.CodeAnalysis.EmptyStatement.DetectedCatch -- intentional: fall through to safe default.
			// Fall through to safe default.
		}
		return '5.7';
	}

	/**
	 * Detect free disk space in MB at the given path.
	 *
	 * @param string $path Filesystem path (typically sys_get_temp_dir()).
	 * @return int  Free disk space in MB, or 0 when unreadable.
	 */
	public static function detect_free_disk_mb( string $path ): int {
		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- @ suppresses E_WARNING when path is on a stat-fail filesystem; explicit false-check follows.
		$free = @disk_free_space( $path );
		if ( false === $free ) {
			return 0;
		}
		return (int) ( $free / 1024 / 1024 );
	}

	/**
	 * Verify wpdo_features option is writable (autoload=no row exists or absent).
	 */
	private static function is_features_option_writable(): bool {
		$probe_key = '_wpdo_v2_writability_probe_' . wp_generate_password( 12, false );
		$ok        = update_option( $probe_key, time(), false );
		delete_option( $probe_key );
		return $ok;
	}

	/**
	 * Verify no migration is currently in-flight (zero rows in 'in_progress' state).
	 */
	private static function no_active_migration(): bool {
		global $wpdb;
		try {
			$count = (int) $wpdb->get_var(
				$wpdb->prepare(
					"SELECT COUNT(*) FROM `{$wpdb->prefix}wpdo_migrations` WHERE state = %s",
					'in_progress'
				)
			);
			return 0 === $count;
		} catch ( \Throwable $e ) {
			// Table may not exist on truly fresh installs — treat as "no active migration".
			return true;
		}
	}

	/**
	 * Quietly deactivate wp-universal-anti-eav plugin if it is currently active.
	 */
	private static function safely_deactivate_uae_plugin(): void {
		if ( ! function_exists( 'deactivate_plugins' ) || ! function_exists( 'is_plugin_active' ) ) {
			require_once ABSPATH . 'wp-admin/includes/plugin.php';
		}
		if ( ! function_exists( 'is_plugin_active' ) ) {
			return;
		}
		$slug = 'wp-universal-anti-eav/wp-universal-anti-eav.php';
		if ( is_plugin_active( $slug ) ) {
			deactivate_plugins( $slug, true );
		}
	}

	/**
	 * Schedule a one-shot cron event to remove the UAE plugin directory.
	 *
	 * Filesystem permission failures fall back to admin notice for manual removal.
	 */
	private static function schedule_uae_dir_removal(): void {
		if ( ! function_exists( 'wp_schedule_single_event' ) ) {
			return;
		}
		if ( ! wp_next_scheduled( 'wpdo_remove_uae_plugin_dir' ) ) {
			wp_schedule_single_event( time() + 5, 'wpdo_remove_uae_plugin_dir' );
		}
	}
}