<?php
/**
 * Zone B (Warm) migration for postmeta to KV warm table.
 *
 * @package WP_Data_Optimizer
 */

declare(strict_types=1);

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

/**
 * Zone B (Warm) migration — postmeta → wpdo_warm KV table with TTL.
 *
 * Reads registered warm fields from Schema Registry,
 * copies their postmeta values into the warm table with optional TTL.
 */
class TMDO_Warm_Migration extends TMDO_Migration_Base {

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

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

	/**
	 * Returns the total number of warm meta rows to migrate.
	 *
	 * @return int Total row count.
	 */
	protected function count_source(): int {
		global $wpdb;

		$meta_keys = $this->get_meta_keys();
		if ( empty( $meta_keys ) ) {
			return 0;
		}

		$placeholders = implode( ',', array_fill( 0, count( $meta_keys ), '%s' ) );

		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- $placeholders from array_fill; $wpdb->postmeta is a core property.
		return (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(*) FROM {$wpdb->postmeta} WHERE meta_key IN ({$placeholders})", // phpcs:ignore WPDO.AntiEAV.no-direct-postmeta-select -- Warm migration: postmeta → Zone B path.
				...$meta_keys
			)
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber
	}

	/**
	 * Migrates one batch of warm meta rows.
	 *
	 * @param int $offset Starting row offset.
	 * @return int Number of rows processed.
	 */
	protected function migrate_batch( int $offset ): int {
		global $wpdb;

		$meta_keys = $this->get_meta_keys();
		if ( empty( $meta_keys ) ) {
			return 0;
		}

		$registry     = TMDO_Schema_Registry::instance();
		$placeholders = implode( ',', array_fill( 0, count( $meta_keys ), '%s' ) );

		$args = array_merge( $meta_keys, array( self::BATCH_SIZE, $offset ) );
		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- $placeholders from array_fill; $wpdb->postmeta is a core property.
		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT post_id, meta_key, meta_value
				 FROM {$wpdb->postmeta}
				 WHERE meta_key IN ({$placeholders})
				 ORDER BY meta_id ASC
				 LIMIT %d OFFSET %d",
				...$args
			),
			ARRAY_A
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber

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

		foreach ( $rows as $row ) {
			$field = $registry->get_warm_field( $row['meta_key'] );
			$ttl   = $field['ttl'] ?? null;

			TMDO_Zone_Warm::set(
				(int) $row['post_id'],
				$row['meta_key'],
				$row['meta_value'],
				$ttl
			);
		}

		return count( $rows );
	}

	/**
	 * Verifies that the warm table row count is at least as large as the source.
	 *
	 * @return bool True if verification passes.
	 */
	public function verify_counts(): bool {
		global $wpdb;

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

		return $target >= $source;
	}

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

	/**
	 * Get all registered warm meta_keys.
	 *
	 * @return array List of meta key strings.
	 */
	private function get_meta_keys(): array {
		$fields = TMDO_Schema_Registry::instance()->get_zone_fields( 'warm' );
		return array_column( $fields, 'meta_key' );
	}
}