<?php
/**
 * Zone C (Cold) migration for postmeta to JSON blob cold table.
 *
 * @package WP_Data_Optimizer
 */

declare(strict_types=1);

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

/**
 * Zone C (Cold) migration — postmeta → JSON blob cold table.
 *
 * For each post, gathers all registered cold meta_keys and stores them
 * as a single JSON blob in wpdo_cold_{post_type}.
 */
class TMDO_Cold_Migration extends TMDO_Migration_Base {

	/**
	 * Post type being migrated.
	 *
	 * @var string
	 */
	private string $post_type;

	/**
	 * Constructor.
	 *
	 * @param string $post_type Post type slug to migrate.
	 */
	public function __construct( string $post_type ) {
		$this->post_type = $post_type;
	}

	/**
	 * Returns the module identifier.
	 *
	 * @return string Module name.
	 */
	public function get_module(): string {
		return TMDO_Zone_Router::module_name( 'cold', $this->post_type );
	}

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

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

		$meta_keys = TMDO_Schema_Registry::instance()->get_cold_meta_keys( $this->post_type );
		if ( empty( $meta_keys ) ) {
			return 0;
		}

		$placeholders = implode( ',', array_fill( 0, count( $meta_keys ), '%s' ) );
		$args         = array_merge( array( $this->post_type ), $meta_keys );

		// Count distinct posts that have at least one cold field.
		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- $placeholders from array_fill; $wpdb->postmeta/$wpdb->posts are core properties.
		return (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(DISTINCT pm.post_id)
				 FROM {$wpdb->postmeta} pm
				 INNER JOIN {$wpdb->posts} p ON p.ID = pm.post_id
				 WHERE p.post_type = %s AND pm.meta_key IN ({$placeholders})",
				...$args
			)
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber
	}

	/**
	 * Migrates one batch of posts to the cold table.
	 *
	 * @param int $offset Starting post offset.
	 * @return int Number of posts processed.
	 */
	protected function migrate_batch( int $offset ): int {
		global $wpdb;

		$meta_keys = TMDO_Schema_Registry::instance()->get_cold_meta_keys( $this->post_type );
		if ( empty( $meta_keys ) ) {
			return 0;
		}

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

		// Get batch of distinct post IDs.
		$args = array_merge( array( $this->post_type ), $meta_keys, array( self::BATCH_SIZE, $offset ) );
		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- $placeholders/$id_placeholders from array_fill; $wpdb->postmeta/$wpdb->posts are core properties.
		$post_ids = $wpdb->get_col(
			$wpdb->prepare(
				"SELECT DISTINCT pm.post_id
				 FROM {$wpdb->postmeta} pm
				 INNER JOIN {$wpdb->posts} p ON p.ID = pm.post_id
				 WHERE p.post_type = %s AND pm.meta_key IN ({$placeholders})
				 ORDER BY pm.post_id ASC
				 LIMIT %d OFFSET %d",
				...$args
			)
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber

		// Ensure cold table exists before any write (even if this batch is empty).
		TMDO_Zone_Cold::ensure_table( $this->post_type );

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

		// Fetch all cold meta for these posts.
		$id_placeholders = implode( ',', array_fill( 0, count( $post_ids ), '%d' ) );

		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber
		$meta_rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT post_id, meta_key, meta_value
				 FROM {$wpdb->postmeta}
				 WHERE post_id IN ({$id_placeholders}) AND meta_key IN ({$placeholders})",
				...array_merge( array_map( 'intval', $post_ids ), $meta_keys )
			),
			ARRAY_A
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber

		// Group by post_id.
		$grouped = array();
		foreach ( $meta_rows ?: array() as $row ) {
			$grouped[ $row['post_id'] ][ $row['meta_key'] ] = $row['meta_value'];
		}

		// Write each post's cold data as a JSON blob.
		foreach ( $grouped as $pid => $data ) {
			TMDO_Zone_Cold::set_many( (int) $pid, $this->post_type, $data );
		}

		return count( $post_ids );
	}

	/**
	 * Verifies that the cold 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_Cold::table( $this->post_type );
		$target = (int) $wpdb->get_var( "SELECT COUNT(*) FROM `{$table}`" ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- table name from TMDO_Zone_Cold::table()

		return $target >= $source;
	}
}