<?php
/**
 * Zone D (Archive) migration for postmeta from trashed/old posts.
 *
 * @package WP_Data_Optimizer
 */

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

/**
 * Zone D (Archive) migration — postmeta from trashed/old posts → wpdo_archive.
 *
 * Unlike other zone migrations that copy specific registered meta_keys,
 * the archive migration sweeps ALL postmeta for posts that meet archival criteria:
 *   - Post is in 'trash' status
 *   - Post was last modified more than $days ago (default: 90 days)
 *
 * Data is optionally gzip-compressed before storage.
 */
class TMDO_Archive_Migration extends TMDO_Migration_Base {

	/**
	 * Minimum age in days for archival.
	 *
	 * @var int
	 */
	private int $days;

	/**
	 * Whether to gzip-compress archived values.
	 *
	 * @var bool
	 */
	private bool $compress;

	/**
	 * Constructor.
	 *
	 * @param int  $days     Minimum age in days for archival.
	 * @param bool $compress Whether to gzip-compress archived values.
	 */
	public function __construct( int $days = 90, bool $compress = true ) {
		$this->days     = $days;
		$this->compress = $compress;
	}

	/**
	 * Returns the module identifier.
	 *
	 * @return string Module name.
	 */
	public function get_module(): string {
		return 'archive';
	}

	/**
	 * Returns the zone identifier.
	 *
	 * @return string Zone name.
	 */
	public function get_zone(): string {
		return 'archive';
	}

	/**
	 * Returns the total number of archive-eligible postmeta rows.
	 *
	 * @return int Total row count.
	 */
	protected function count_source(): int {
		global $wpdb;

		$cutoff = $this->get_cutoff();

		return (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(*)
				 FROM {$wpdb->postmeta} pm
				 INNER JOIN {$wpdb->posts} p ON p.ID = pm.post_id
				 WHERE p.post_status = 'trash'
				   AND p.post_modified_gmt < %s",
				$cutoff
			)
		);
	}

	/**
	 * Migrates one batch of eligible postmeta rows to the archive table.
	 *
	 * @param int $offset Starting row offset.
	 * @return int Number of rows processed.
	 */
	protected function migrate_batch( int $offset ): int {
		global $wpdb;

		$cutoff = $this->get_cutoff();

		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT pm.meta_id, pm.post_id, pm.meta_key, pm.meta_value, p.post_type
				 FROM {$wpdb->postmeta} pm
				 INNER JOIN {$wpdb->posts} p ON p.ID = pm.post_id
				 WHERE p.post_status = 'trash'
				   AND p.post_modified_gmt < %s
				 ORDER BY pm.meta_id ASC
				 LIMIT %d OFFSET %d",
				$cutoff,
				self::BATCH_SIZE,
				$offset
			),
			ARRAY_A
		);

		if ( empty( $rows ) ) {
			return 0;
		}

		$entries = array();
		foreach ( $rows as $row ) {
			$entries[] = array(
				'post_id'    => $row['post_id'],
				'post_type'  => $row['post_type'],
				'meta_key'   => $row['meta_key'],
				'meta_value' => $row['meta_value'],
				'meta_id'    => $row['meta_id'],
			);
		}

		TMDO_Zone_Archive::archive_batch( $entries, $this->compress );

		return count( $rows );
	}

	/**
	 * Verifies that archive table has rows when eligible source rows exist.
	 *
	 * @return bool True if verification passes.
	 */
	public function verify_counts(): bool {
		global $wpdb;

		$source = $this->count_source();
		$table  = TMDO_Zone_Archive::table();
		$target = (int) $wpdb->get_var( "SELECT COUNT(*) FROM `{$table}`" ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- table name from TMDO_Zone_Archive::table()

		// Archive may have more rows than current source (trashed posts may have
		// been permanently deleted after archival). So we just check target > 0
		// when source is 0, or target >= some threshold.
		if ( 0 === $source ) {
			return true;
		}

		return $target >= $source;
	}

	// ── Private helpers ───────────────────────────────────────────────────

	/**
	 * Returns the cutoff datetime string for archival eligibility.
	 *
	 * @return string MySQL datetime string.
	 */
	private function get_cutoff(): string {
		return gmdate( 'Y-m-d H:i:s', time() - ( $this->days * DAY_IN_SECONDS ) );
	}
}