<?php
/**
 * TMDO_Post_Query_Router — Post entity meta_query → flat table JOIN rewriter (v2.10.1).
 *
 * Companion to legacy TMDO_Query_Router (which targets zone hot tables).
 * Independent class — does NOT modify the user side path or the legacy zone
 * router. Both routers can coexist on the same WP_Query without conflict
 * because they extract clauses on disjoint criteria:
 *
 *   - TMDO_Query_Router         → only zone-registered keys with feature_flag query_active
 *   - TMDO_Post_Query_Router    → only entity-registered keys with mode=reads_from_flat
 *
 * Mode-gated: only rewrites when post mode is `shadow_read` or `aeav_only`.
 * In `disabled` / `dual_write` modes the router is a no-op.
 *
 * Hook order:
 *   1. pre_get_posts  — strip registered keys from meta_query, store in
 *                       $query->set( 'wpdo_post_clauses', $routed )
 *   2. posts_join     — LEFT JOIN wp_wpdo_post_<group> per routed group
 *   3. posts_where    — append WHERE conditions targeting flat columns
 *
 * Flat tables hold one row per post (UNIQUE post_id), so the joins never
 * multiply rows and no GROUP BY is added.
 *
 * Status / date on the flat table (O-1): when the group's post_status /
 * post_date copies are ready (TMDO_Post_Status_Sync) and none is missing,
 * a single-post-type search with explicit statuses and date ordering
 * INNER JOINs the table, filters the copies and orders by the copied
 * post_date (ID tie-breaks read as the flat post_id), so MySQL can walk
 * `idx_post_status_date_id` and stop at the LIMIT. Not with NOT EXISTS:
 * posts without a flat row must still match.
 *
 * Found rows (O-4): routed searches drop SQL_CALC_FOUND_ROWS (it counts every
 * match inside the page query); found_posts_query answers from a COUNT of the
 * same query, kept in the object cache until a post is saved or deleted, a
 * flat write goes through TMDO_Hook_Bus (bump_count_version()) or terms'
 * last_changed moves. Not posts' last_changed: WordPress moves it on any post
 * meta write, which themes do on page views (Blocksy's dynamic CSS), and a
 * routed search reads no unmanaged meta.
 *
 * 🔒 v2.9.x → v2.10.x frozen contract: never touches user entity. Routes
 * only entity_type='post'.
 *
 * @package WP_Data_Optimizer
 * @since   2.10.1
 */

declare(strict_types=1);

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

// phpcs:disable WordPress.DB.PreparedSQL.NotPrepared,WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Internal query rewriter: table names go through Schema_Manager::sanitize_column_name, column names go through esc_sql, user-controlled values use $wpdb->prepare() in build_condition().

/**
 * Rewrites WP_Query meta_query clauses to JOIN against post entity flat tables.
 */
class TMDO_Post_Query_Router {

	/** Query var key for capturing routed clauses (consumed by posts_join/where). */
	private const QUERY_VAR = 'wpdo_post_clauses';

	/** Query var holding the status / date copy route, when one applies. */
	private const COPY_VAR = 'wpdo_post_copy_route';

	/** Query var holding the flat column a routed meta orderby sorts on. */
	private const SORT_VAR = 'wpdo_post_sort';

	/** Query var holding the COUNT for found_posts_query. */
	private const COUNT_VAR = 'wpdo_post_count_sql';

	/** Object cache group for found-rows counts. */
	private const COUNT_CACHE_GROUP = 'tmdo_found_rows';

	/** The last_changed group the cached counts follow (bump_count_version()). */
	public const COUNT_VERSION_GROUP = 'tmdo_posts';

	/** Seconds a "every post of the type has a flat row" answer is reused. */
	private const COVERAGE_TTL = 900;

	/** Comparison operators the router can express on a flat column. */
	private const COMPARES = array( '=', '!=', '<>', '<', '<=', '>', '>=', 'IN', 'NOT IN', 'LIKE', 'NOT LIKE', 'BETWEEN', 'NOT BETWEEN', 'EXISTS', 'NOT EXISTS' );

	/**
	 * Per-request answer to "are this group's copies usable?".
	 *
	 * @var array<string, bool>
	 */
	private static array $copies_usable = array();

	/**
	 * Register all WP_Query hooks.
	 *
	 * @return void
	 */
	public function register_hooks(): void {
		// Late, so meta clauses other plugins add at the default priority
		// (e.g. HivePress search filters and sorting) are already in the query.
		add_action( 'pre_get_posts', array( $this, 'pre_get_posts' ), 1000, 1 );
		add_filter( 'posts_join', array( $this, 'posts_join' ), 10, 2 );
		add_filter( 'posts_where', array( $this, 'posts_where' ), 10, 2 );
		add_filter( 'posts_orderby', array( $this, 'posts_orderby' ), 10, 2 );
		add_filter( 'posts_request', array( $this, 'posts_request' ), 10, 2 );
		add_filter( 'split_the_query', array( $this, 'split_the_query' ), 10, 4 );
		add_filter( 'posts_request_ids', array( $this, 'posts_request' ), 10, 2 );
		add_filter( 'found_posts_query', array( $this, 'found_posts_query' ), 10, 2 );
		add_action( 'wp_insert_post', array( $this, 'add_flat_rows' ), 10, 3 );
	}

	/**
	 * A new post of a type with its own groups gets an empty row in each, so
	 * that "every post of the type has a flat row" keeps holding and sort-only
	 * searches can drive from the flat table (see flat_first()).
	 *
	 * @param int      $post_id Post ID.
	 * @param \WP_Post $post    Post.
	 * @param bool     $update  Whether an existing post was updated.
	 * @return void
	 */
	public function add_flat_rows( $post_id, $post, $update ): void {
		if ( $update || ! $post instanceof \WP_Post ) {
			return;
		}
		global $wpdb;
		foreach ( TMDO_Post_Fields::groups_for_post_type( $post->post_type ) as $group ) {
			$table = TMDO_Schema_Manager::get_table_name( 'post', $group );
			if ( TMDO_Schema_Manager::table_exists( $table ) ) {
				$wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `{$table}` (`post_id`) VALUES (%d)", (int) $post_id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			}
		}
	}

	/**
	 * Strip Entity-Registry-managed meta_query keys; store routed clauses.
	 *
	 * @param \WP_Query $query Current WP_Query.
	 * @return void
	 */
	public function pre_get_posts( \WP_Query $query ): void {
		// Mode gate: only run when post mode is reads_from_flat.
		if ( ! self::is_router_active() ) {
			return;
		}

		// is_admin guard (matches legacy TMDO_Query_Router behavior).
		if ( is_admin() && ! wp_doing_ajax() ) {
			return;
		}

		// One post type only: with several, a clause may belong to one type's
		// group and the others must still match through wp_postmeta.
		$post_types = (array) $query->get( 'post_type' );
		if ( 1 !== count( $post_types ) ) {
			return;
		}
		$pt = (string) reset( $post_types );

		$raw_meta_query = (array) $query->get( 'meta_query' );

		// All or nothing: routed clauses are ANDed into the WHERE, so the
		// query is routed only when every registered clause can be, and
		// the remaining (unregistered) clauses are ANDed too.
		$relation  = strtoupper( (string) ( $raw_meta_query['relation'] ?? 'AND' ) );
		$orderby   = $query->get( 'orderby' );
		$named     = is_array( $orderby ) ? array_keys( $orderby ) : preg_split( '/[\s,]+/', trim( (string) $orderby ) );
		$sort_name = 1 === count( $named ) ? (string) reset( $named ) : '';
		$direction = 'ASC' === strtoupper( (string) ( is_array( $orderby ) ? reset( $orderby ) : $query->get( 'order' ) ) ) ? 'ASC' : 'DESC';
		$routed    = array(); // Keyed by post_type.
		$remaining = array();
		$sort      = array();

		// meta_key + orderby meta_value(_num): native INNER JOINs the key
		// (EXISTS) and orders by meta_value+0 (NUMERIC) or meta_value.
		$meta_key = $query->get( 'meta_key' );
		$take_key = is_string( $meta_key ) && in_array( $sort_name, array( 'meta_value', 'meta_value_num' ), true )
			&& null !== self::field_for( array( 'key' => $meta_key ), $pt );
		if ( $take_key ) {
			$field = self::field_for( array( 'key' => $meta_key ), $pt );
			$type  = 'meta_value_num' === $sort_name ? 'NUMERIC' : (string) $query->get( 'meta_type' );
			$route = self::route_clause(
				array(
					'key'     => $meta_key,
					'compare' => 'EXISTS',
					'type'    => $type,
				),
				$field
			);
			if ( ! $route || ! self::sortable( $route, $field ) || '' !== $query->get( 'meta_value' ) || '' !== $query->get( 'meta_compare' ) ) {
				return;
			}
			$routed[ $pt ][] = $route;
			$sort            = self::sort_for( $pt, $route, $direction );
		}
		// meta_key alone (no meta_value, not a meta_value sort): WP_Query adds a
		// clause that tests the key exists — HivePress's featured-listing lookup.
		$exists_key = ! $take_key && is_string( $meta_key ) && '' !== $meta_key
			&& '' === (string) $query->get( 'meta_value' ) && '' === (string) $query->get( 'meta_compare' )
			&& ! in_array( $sort_name, array( 'meta_value', 'meta_value_num' ), true )
			&& null !== self::field_for( array( 'key' => $meta_key ), $pt );
		if ( $exists_key ) {
			$route = self::route_clause(
				array(
					'key'     => $meta_key,
					'compare' => 'EXISTS',
				),
				self::field_for( array( 'key' => $meta_key ), $pt )
			);
			if ( ! $route ) {
				return;
			}
			$routed[ $pt ][] = $route;
		}

		foreach ( $raw_meta_query as $k => $clause ) {
			if ( 'relation' === $k || ! is_array( $clause ) ) {
				$remaining[ $k ] = $clause;
				continue;
			}
			if ( ! isset( $clause['key'] ) ) {
				// Sort shape: matches every post, only orders by the key.
				$name = 'AND' === $relation ? self::sort_shape( $clause ) : '';
				if ( '' !== $name && ! in_array( $name, $named, true ) && self::field_for( $clause[ $name ], $pt ) ) {
					continue; // Matches every post and orders nothing here (a copy of a search's meta query).
				}
				$field = '' !== $name && $name === $sort_name ? self::field_for( $clause[ $name ], $pt ) : null;
				if ( $field ) {
					$route = self::route_clause( array( 'compare' => 'EXISTS' ) + $clause[ $name ], $field );
					if ( ! $route || ! self::sortable( $route, $field ) ) {
						return;
					}
					$sort = self::sort_for( $pt, $route, $direction );
					continue;
				}
				if ( self::has_registered_key( $clause, $pt ) ) {
					return; // Nested group.
				}
				$remaining[ $k ] = $clause;
				continue;
			}

			$field = self::field_for( $clause, $pt );
			if ( ! $field ) {
				$remaining[ $k ] = $clause;
				continue;
			}
			$route = self::route_clause( $clause, $field );
			if ( ! $route || 'AND' !== $relation ) {
				return;
			}
			// Named by orderby: only as the sole ordering, on a column that
			// orders like native (otherwise the name would be lost).
			if ( is_string( $k ) && in_array( $k, $named, true ) ) {
				if ( $k !== $sort_name || ! self::sortable( $route, $field ) ) {
					return;
				}
				$sort = self::sort_for( $pt, $route, $direction );
			}
			$routed[ $pt ][] = $route;
		}

		if ( empty( $routed ) && empty( $sort ) ) {
			return;
		}
		if ( $take_key || $exists_key ) {
			$query->set( 'meta_key', '' );
		}
		if ( $sort ) {
			$query->set( self::SORT_VAR, $sort );
		}

		// Preserve relation if surviving clauses still have it.
		if ( isset( $raw_meta_query['relation'] ) && ! isset( $remaining['relation'] ) ) {
			$remaining['relation'] = $raw_meta_query['relation'];
		}

		$query->set( 'meta_query', $remaining );
		$query->set( self::QUERY_VAR, $routed );

		$copy = self::copy_route( $query, $routed );
		if ( $copy ) {
			$query->set( self::COPY_VAR, $copy );
		}
	}

	/**
	 * LEFT JOIN the flat table of each routed group.
	 *
	 * @param string|null $join  Current JOIN SQL.
	 * @param \WP_Query   $query Current WP_Query.
	 * @return string Modified JOIN SQL.
	 */
	public function posts_join( ?string $join, \WP_Query $query ): string {
		$join   = (string) ( $join ?? '' );
		$routed = $query->get( self::QUERY_VAR );
		$sort   = $query->get( self::SORT_VAR );
		$pairs  = array(); // Pairs of post type and group.
		foreach ( is_array( $routed ) ? $routed : array() as $post_type => $clauses ) {
			foreach ( array_column( $clauses, 'group' ) as $group ) {
				$pairs[] = array( $post_type, $group );
			}
		}
		if ( ! empty( $sort ) ) {
			$pairs[] = array( $sort['post_type'], $sort['group'] );
		}

		global $wpdb;

		foreach ( $pairs as list( $post_type, $group ) ) {
			$table = $wpdb->prefix . 'wpdo_post_' . sanitize_key( $group );
			$alias = self::table_alias( $post_type, $group );

			// Don't double-join.
			if ( false !== strpos( $join, "`{$alias}`" ) ) {
				continue;
			}

			// The copy route only applies to single-group searches.
			$type  = self::copy_route_for( $query, $post_type ) ? 'INNER' : 'LEFT';
			$join .= " {$type} JOIN `{$table}` AS `{$alias}` "
				. "ON (`{$wpdb->posts}`.`ID` = `{$alias}`.`post_id`)";
		}

		return $join;
	}

	/**
	 * Append WHERE conditions for routed clauses.
	 *
	 * @param string|null $where Current WHERE SQL.
	 * @param \WP_Query   $query Current WP_Query.
	 * @return string Modified WHERE SQL.
	 */
	public function posts_where( ?string $where, \WP_Query $query ): string {
		$where  = (string) ( $where ?? '' );
		$routed = $query->get( self::QUERY_VAR );
		if ( empty( $routed ) || ! is_array( $routed ) ) {
			return $where;
		}

		global $wpdb;

		foreach ( $routed as $post_type => $clauses ) {
			foreach ( $clauses as $clause ) {
				$alias   = self::table_alias( $post_type, $clause['group'] );
				$col     = '`' . $alias . '`.`' . esc_sql( $clause['column'] ) . '`';
				$compare = self::sanitize_compare( $clause['compare'] );
				$value   = $clause['value'];

				$where .= self::build_condition( $col, $compare, $value );
			}
		}

		$copy = $query->get( self::COPY_VAR );
		if ( ! empty( $copy ) ) {
			$alias  = self::table_alias( $copy['post_type'], $copy['group'] );
			$where .= self::build_condition( "`{$alias}`.`post_status`", 'IN', $copy['statuses'] );
		}

		return $where;
	}

	/**
	 * Order by the routed meta orderby column (ties by ID), or by the flat
	 * table's post_date copy when the copy route applies.
	 *
	 * @param string|null $orderby Current ORDER BY SQL.
	 * @param \WP_Query   $query   Current WP_Query.
	 * @return string Modified ORDER BY SQL.
	 */
	public function posts_orderby( ?string $orderby, \WP_Query $query ): string {
		$orderby = (string) ( $orderby ?? '' );
		$sort    = $query->get( self::SORT_VAR );
		if ( ! empty( $sort ) ) {
			global $wpdb;
			return '`' . self::table_alias( $sort['post_type'], $sort['group'] ) . '`.`' . esc_sql( $sort['column'] ) . '` '
				. $sort['order'] . ", `{$wpdb->posts}`.`ID` DESC";
		}
		$copy = $query->get( self::COPY_VAR );
		if ( empty( $copy ) ) {
			return $orderby;
		}
		return '`' . self::table_alias( $copy['post_type'], $copy['group'] ) . '`.`post_date` ' . $copy['order'];
	}

	/**
	 * Drop SQL_CALC_FOUND_ROWS from a routed search; keep its COUNT for later.
	 *
	 * @param string|null $request Full SELECT.
	 * @param \WP_Query   $query   Current WP_Query.
	 * @return string
	 */
	public function posts_request( ?string $request, \WP_Query $query ): string {
		$request = (string) ( $request ?? '' );
		$routed  = ! empty( $query->get( self::QUERY_VAR ) ) || ! empty( $query->get( self::SORT_VAR ) );
		if ( ! $routed ) {
			return $request;
		}
		$counted = false !== strpos( $request, 'SQL_CALC_FOUND_ROWS' );
		$request = self::routed_request( $request, $query );
		if ( ! $counted ) {
			return $request;
		}
		global $wpdb;
		$matches = (string) preg_replace( '/\s+LIMIT\s+\d+(\s*,\s*\d+)?\s*$/i', '', $request );
		$not_in  = " AND {$wpdb->posts}.ID NOT IN (";
		// post__not_in (HivePress sends a random set per page) would give every
		// search its own cache key: count without it (cached) minus the excluded
		// posts that match (primary-key lookups, so no forced flat-first order).
		if ( 1 === substr_count( $matches, $not_in ) && preg_match( '/' . preg_quote( $not_in, '/' ) . '([\d,]+)\)/', $matches, $m ) ) {
			$excluded = str_replace( $m[0], " AND {$wpdb->posts}.ID IN ({$m[1]})", (string) preg_replace( '/^SELECT STRAIGHT_JOIN /', 'SELECT ', $matches ) );
			$query->set(
				self::COUNT_VAR,
				array(
					'SELECT COUNT(*) FROM ( ' . str_replace( $m[0], '', $matches ) . ' ) AS tmdo_found',
					"SELECT COUNT(*) FROM ( {$excluded} ) AS tmdo_found",
				)
			);
			return $request;
		}
		$query->set( self::COUNT_VAR, "SELECT COUNT(*) FROM ( {$matches} ) AS tmdo_found" );
		return $request;
	}

	/**
	 * Keep WordPress's split query (IDs first, then cached post objects) on a
	 * routed search: posts_request only dropped SQL_CALC_FOUND_ROWS, yet
	 * WordPress takes any change for a filtered request and selects full rows
	 * (a temporary table sorting whole posts). The split ID request passes
	 * through posts_request_ids, which drops SQL_CALC_FOUND_ROWS again.
	 *
	 * @param bool                  $split       Core decision.
	 * @param \WP_Query             $query       Current WP_Query.
	 * @param string                $old_request Request before posts_request.
	 * @param array<string, string> $clauses     Query clauses (fields, limits …).
	 * @return bool
	 */
	public function split_the_query( $split, \WP_Query $query, $old_request = '', $clauses = array() ): bool {
		$routed = ! empty( $query->get( self::QUERY_VAR ) ) || ! empty( $query->get( self::SORT_VAR ) );
		if ( $split || ! $routed ) {
			return (bool) $split;
		}
		global $wpdb;
		// Core's other conditions: full rows, and a LIMIT under 500 or an external object cache.
		return "{$wpdb->posts}.*" === ( $clauses['fields'] ?? '' )
			&& self::routed_request( (string) $old_request, $query ) === $query->request
			&& ( ( '' !== ( $clauses['limits'] ?? '' ) && (int) $query->get( 'posts_per_page' ) < 500 ) || wp_using_ext_object_cache() );
	}

	/**
	 * Answer found rows from the cached COUNT of a routed search.
	 *
	 * @param string|null $sql   Default 'SELECT FOUND_ROWS()'.
	 * @param \WP_Query   $query Current WP_Query.
	 * @return string
	 */
	public function found_posts_query( ?string $sql, \WP_Query $query ): string {
		$count_sql = $query->get( self::COUNT_VAR );
		if ( empty( $count_sql ) ) {
			return (string) ( $sql ?? '' );
		}
		global $wpdb;
		list( $count_sql, $excluded_sql ) = array_pad( (array) $count_sql, 2, '' );

		// Keyword searches carry wpdb's placeholder escape for "%", which is new
		// in every request: without it the key would never match again.
		$stable = method_exists( $wpdb, 'remove_placeholder_escape' ) ? $wpdb->remove_placeholder_escape( $count_sql ) : $count_sql;
		$key    = md5( $stable ) . ':' . wp_cache_get_last_changed( self::COUNT_VERSION_GROUP ) . ':' . wp_cache_get_last_changed( 'terms' );
		$total  = wp_cache_get( $key, self::COUNT_CACHE_GROUP );
		if ( false === $total ) {
			$total = (int) $wpdb->get_var( $count_sql );
			wp_cache_set( $key, $total, self::COUNT_CACHE_GROUP, HOUR_IN_SECONDS );
		}
		if ( '' !== $excluded_sql ) {
			$total = max( 0, (int) $total - (int) $wpdb->get_var( $excluded_sql ) );
		}
		return 'SELECT ' . (int) $total;
	}

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

	/**
	 * A post was saved or deleted, or a managed key written: cached routed
	 * counts are stale. Hooked on clean_post_cache whatever the mode, so a
	 * count cached before the router was last active is not reused.
	 *
	 * @return void
	 */
	public static function bump_count_version(): void {
		wp_cache_set_last_changed( self::COUNT_VERSION_GROUP );
	}

	/**
	 * Whether the router is mode-active (post mode is shadow_read or aeav_only).
	 *
	 * @return bool
	 */
	public static function is_router_active(): bool {
		if ( ! class_exists( 'TMDO_Mode_Manager' ) ) {
			return false;
		}
		return TMDO_Mode_Manager::reads_from_flat( 'post' );
	}

	/**
	 * Forget per-request copy checks (tests, or after `post-status-sync`).
	 *
	 * @return void
	 */
	public static function flush_copy_cache(): void {
		self::$copies_usable = array();
	}

	/**
	 * Every post of the type has a row in the group's flat table. One
	 * anti-join per group, reused for COVERAGE_TTL and per post-mode change.
	 * A post inserted by direct SQL (no wp_insert_post) is seen at the next
	 * check at the latest; the `tmdo_router_flat_first` filter turns the
	 * flat-first route off.
	 *
	 * @param string $post_type Post type.
	 * @param string $group     Entity group name.
	 * @return bool
	 */
	private static function covers_all( string $post_type, string $group ): bool {
		$key = self::coverage_key( $post_type, $group );
		$hit = get_transient( $key );
		if ( false === $hit ) {
			global $wpdb;
			$table   = TMDO_Schema_Manager::get_table_name( 'post', $group );
			$missing = $wpdb->get_var( $wpdb->prepare( "SELECT 1 FROM {$wpdb->posts} p LEFT JOIN `{$table}` f ON f.post_id = p.ID WHERE p.post_type = %s AND f.post_id IS NULL LIMIT 1", $post_type ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			$hit     = null === $missing ? 'yes' : 'no';
			set_transient( $key, $hit, self::COVERAGE_TTL );
		}
		return 'yes' === $hit;
	}

	/**
	 * Forget every cached coverage answer (tests, or after bulk writes that
	 * bypass wp_insert_post).
	 *
	 * @return void
	 */
	public static function forget_coverage(): void {
		foreach ( TMDO_Entity_Registry::get_groups_for_type( 'post' ) as $group ) {
			foreach ( TMDO_Entity_Registry::get_group_post_types( 'post', $group ) as $post_type ) {
				delete_transient( self::coverage_key( $post_type, $group ) );
			}
		}
	}

	/**
	 * Transient name of a coverage answer; a post-mode change starts a new one.
	 *
	 * @param string $post_type Post type.
	 * @param string $group     Entity group name.
	 * @return string
	 */
	private static function coverage_key( string $post_type, string $group ): string {
		$entered = get_option( TMDO_Mode_Manager::OPT_ENTERED_AT, array() );
		$since   = is_array( $entered ) ? (int) ( $entered['post'] ?? 0 ) : 0;
		return 'tmdo_cov_' . md5( "{$post_type}:{$group}:{$since}" );
	}

	/**
	 * The status / date copy route for a routed query, or [] when it does not apply.
	 *
	 * @param \WP_Query                                       $query  Current WP_Query.
	 * @param array<string, array<int, array<string, mixed>>> $routed Routed clauses keyed by post type.
	 * @return array{post_type:string, group:string, statuses:string[], order:string}|array{}
	 */
	private static function copy_route( \WP_Query $query, array $routed ): array {
		if ( 1 !== count( $routed ) ) {
			return array();
		}
		$post_type = (string) array_key_first( $routed );
		$groups    = array_values( array_unique( array_column( $routed[ $post_type ], 'group' ) ) );
		if ( 1 !== count( $groups ) || ! in_array( $query->get( 'orderby' ), array( '', 'date', 'post_date' ), true )
			|| in_array( 'NOT EXISTS', array_column( $routed[ $post_type ], 'compare' ), true ) ) {
			return array();
		}
		$statuses = $query->get( 'post_status' );
		$statuses = array_values( array_filter( array_map( 'sanitize_key', is_array( $statuses ) ? $statuses : explode( ',', (string) $statuses ) ) ) );
		if ( empty( $statuses ) || in_array( 'any', $statuses, true ) || ! self::copies_usable( $groups[0] ) ) {
			return array();
		}
		return array(
			'post_type' => $post_type,
			'group'     => $groups[0],
			'statuses'  => $statuses,
			'order'     => 'ASC' === strtoupper( (string) $query->get( 'order' ) ) ? 'ASC' : 'DESC',
		);
	}

	/**
	 * Whether the copy route applies to this post type's join.
	 *
	 * @param \WP_Query $query     Current WP_Query.
	 * @param string    $post_type Post type slug.
	 * @return bool
	 */
	private static function copy_route_for( \WP_Query $query, string $post_type ): bool {
		$copy = $query->get( self::COPY_VAR );
		return ! empty( $copy ) && $copy['post_type'] === $post_type;
	}

	/**
	 * Copies are marked ready and no row lacks them (bulk writes that bypass
	 * the Hook Bus leave NULLs until `wp tmdo post-status-sync` runs again).
	 * One index probe per group per request.
	 *
	 * @param string $group Entity group name.
	 * @return bool
	 */
	private static function copies_usable( string $group ): bool {
		if ( ! isset( self::$copies_usable[ $group ] ) ) {
			global $wpdb;
			$table                         = TMDO_Schema_Manager::get_table_name( 'post', $group );
			self::$copies_usable[ $group ] = class_exists( 'TMDO_Post_Status_Sync' )
				&& 'ready' === TMDO_Post_Status_Sync::state( $group )
				&& TMDO_Schema_Manager::table_exists( $table )
				&& null === $wpdb->get_var( "SELECT 1 FROM `{$table}` WHERE `post_status` IS NULL LIMIT 1" );
		}
		return self::$copies_usable[ $group ];
	}

	/**
	 * The registered field a clause targets for this post type, or null.
	 *
	 * @param array<string, mixed> $clause    Meta query clause.
	 * @param string               $post_type Post type slug.
	 * @return array<string, mixed>|null
	 */
	private static function field_for( array $clause, string $post_type ): ?array {
		if ( ! is_string( $clause['key'] ?? null ) || ! in_array( $clause['compare_key'] ?? '=', array( '=', '' ), true ) ) {
			return null;
		}
		$field = TMDO_Entity_Registry::get_field( 'post', $clause['key'], $post_type );
		if ( ! $field ) {
			return null;
		}
		// Either cross-cutting wp_core or one of the post type's own groups.
		$group = $field['group'] ?? '';
		return ( 'wp_core' === $group || in_array( $group, TMDO_Post_Fields::groups_for_post_type( $post_type ), true ) ) ? $field : null;
	}

	/**
	 * Whether a nested meta query group references a registered key.
	 *
	 * @param array<int|string, mixed> $group     Nested group.
	 * @param string                   $post_type Post type slug.
	 * @return bool
	 */
	private static function has_registered_key( array $group, string $post_type ): bool {
		foreach ( $group as $clause ) {
			if ( ! is_array( $clause ) ) {
				continue;
			}
			if ( isset( $clause['key'] ) ? null !== self::field_for( $clause, $post_type ) : self::has_registered_key( $clause, $post_type ) ) {
				return true;
			}
		}
		return false;
	}

	/**
	 * The last `wp tmdo drift-check` found the group out of step with native
	 * meta. A group never checked keeps routing, and so does every group in
	 * aeav_only, where native is stale by design and no fallback.
	 *
	 * @param string $group Entity group name.
	 * @return bool
	 */
	private static function drifting( string $group ): bool {
		if ( TMDO_Mode_Manager::MODE_AEAV_ONLY === TMDO_Mode_Manager::get( 'post' ) ) {
			return false;
		}
		if ( TMDO_Schema_Manager::is_deferred( 'post', $group ) ) {
			return true; // Table upgrade waiting for WP-CLI / WP-Cron.
		}
		$status = get_option( TMDO_Drift_Check::OPTION, array() );
		$last   = is_array( $status ) ? ( $status['post'][ $group ] ?? null ) : null;
		return is_array( $last ) && (int) ( $last['miss'] ?? 0 ) + (int) ( $last['diff'] ?? 0 ) + (int) ( $last['extra'] ?? 0 ) > 0;
	}

	/**
	 * The routed form of a clause, or null when the flat column would not
	 * compare the way WordPress compares the meta_value string, or when the
	 * group is known to drift from native meta.
	 *
	 * Native casts meta_value by the clause type (CHAR when absent); flat
	 * columns are typed. Routed: EXISTS / NOT EXISTS; string columns with
	 * CHAR; numeric columns with a numeric type (no LIKE); integer columns
	 * with CHAR =, !=, IN, NOT IN on plain integers ("10" = "10" either way).
	 *
	 * @param array<string, mixed> $clause Meta query clause.
	 * @param array<string, mixed> $field  Registered field.
	 * @return array{group:string, column:string, value:mixed, compare:string, type:string}|null
	 */
	private static function route_clause( array $clause, array $field ): ?array {
		$compare = strtoupper( trim( (string) ( $clause['compare'] ?? '=' ) ) );
		// Without 'value', WP_Meta_Query checks only that the key exists (it adds a
		// value condition only when one is set): HivePress's featured-listing
		// lookup, run on every search page, is array( 'key' => 'hp_featured' ).
		if ( ! array_key_exists( 'value', $clause ) && ! in_array( $compare, array( 'EXISTS', 'NOT EXISTS' ), true ) ) {
			$compare = 'EXISTS';
		}
		$type  = strtoupper( trim( (string) ( $clause['type'] ?? '' ) ) );
		$type  = '' === $type ? 'CHAR' : $type;
		$value = $clause['value'] ?? '';
		$kind  = $field['type'] ?? 'text';
		$multi = in_array( $compare, array( 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ), true );

		if ( ! in_array( $compare, self::COMPARES, true ) || ( ! $multi && is_array( $value ) ) ) {
			return null;
		}

		$numeric_type = self::is_numeric_type( $type );
		if ( in_array( $compare, array( 'EXISTS', 'NOT EXISTS' ), true ) ) {
			$ok = in_array( $kind, array( 'text', 'textarea', 'enum', 'integer', 'decimal', 'boolean' ), true );
		} elseif ( in_array( $kind, array( 'text', 'textarea', 'enum' ), true ) ) {
			$ok = 'CHAR' === $type;
		} elseif ( in_array( $kind, array( 'integer', 'decimal', 'boolean' ), true ) && $numeric_type ) {
			$ok = ! in_array( $compare, array( 'LIKE', 'NOT LIKE' ), true );
		} else {
			$ok = in_array( $kind, array( 'integer', 'boolean' ), true ) && 'CHAR' === $type
				&& in_array( $compare, array( '=', '!=', '<>', 'IN', 'NOT IN' ), true )
				&& array() === array_filter( (array) $value, static fn( $v ) => ! is_scalar( $v ) || (string) (int) $v !== (string) $v );
		}
		if ( ! $ok || self::drifting( (string) $field['group'] ) ) {
			return null;
		}

		return array(
			'group'   => (string) $field['group'],
			'column'  => TMDO_Schema_Manager::sanitize_column_name( $clause['key'] ),
			'value'   => $value,
			'compare' => $compare,
			'type'    => $type,
		);
	}

	/**
	 * What posts_request makes of a routed request.
	 *
	 * @param string    $request SELECT statement.
	 * @param \WP_Query $query   Current WP_Query.
	 * @return string
	 */
	private static function routed_request( string $request, \WP_Query $query ): string {
		return self::copy_ordered( self::flat_first( self::without_found_rows( $request ), $query ), $query );
	}

	/**
	 * The copy route's request without WordPress's GROUP BY (when the flat row
	 * is the only join) and with posts.ID tie-breaks read as the flat post_id,
	 * each in its own direction, once. MariaDB then walks the
	 * (post_status, post_date, post_id) index and stops at the LIMIT instead
	 * of sorting every match (dev36, 235k of 1.3M listings: 1.7 s → 3 ms).
	 *
	 * @param string    $request SELECT statement.
	 * @param \WP_Query $query   Current WP_Query.
	 * @return string
	 */
	private static function copy_ordered( string $request, \WP_Query $query ): string {
		$copy = $query->get( self::COPY_VAR );
		if ( empty( $copy ) ) {
			return $request;
		}
		global $wpdb;
		$tie = '`' . self::table_alias( $copy['post_type'], $copy['group'] ) . '`.`post_id` ';
		return (string) preg_replace_callback(
			'/\bORDER BY\b(?!.*\bORDER BY\b).*$/s',
			static function ( $m ) use ( $wpdb, $tie ) {
				$order = (string) preg_replace_callback(
					'/`?' . preg_quote( $wpdb->posts, '/' ) . '`?\.`?ID`?(?!\w)(?:\s+(ASC|DESC)\b)?/i',
					static fn( $id ) => $tie . ( 'DESC' === strtoupper( $id[1] ?? '' ) ? 'DESC' : 'ASC' ),
					$m[0]
				);
				return (string) preg_replace( '/(,\s*' . preg_quote( $tie, '/' ) . '(ASC|DESC))(\s*,\s*' . preg_quote( $tie, '/' ) . '\2)+/', '$1', $order );
			},
			self::without_group_by( $request )
		);
	}

	/**
	 * WordPress groups by posts.ID for any tax or meta query. With a flat row
	 * (one per post) as the only join there is nothing to collapse, and the
	 * GROUP BY makes MySQL sort the whole match in a temporary table
	 * (WooCommerce's product_visibility NOT IN on searches is a subquery).
	 *
	 * @param string $request SELECT statement.
	 * @return string
	 */
	private static function without_group_by( string $request ): string {
		global $wpdb;
		if ( 1 !== preg_match_all( '/\bJOIN\b/i', $request ) ) {
			return $request;
		}
		return (string) preg_replace( '/\s+GROUP BY\s+`?' . preg_quote( $wpdb->posts, '/' ) . '`?\.`?ID`?(?=\s)/', ' ', $request, 1 );
	}

	/**
	 * Drive a filtered search ordered by a flat column from its flat table.
	 *
	 * MariaDB starts from wp_posts (the type / status index), looks every
	 * candidate up in the flat table and sorts in a temporary table. From the
	 * flat table, with the posts.ID tie-break read as the equal flat post_id,
	 * it sorts one table (dev36, 100k listings: meta_value_num 263 → 147 ms,
	 * HivePress sort + filter 300 → 36 ms). Only when the routed conditions
	 * already require a flat row (LEFT JOIN = INNER JOIN), all on the sort
	 * group, without a selective post filter; `tmdo_router_flat_first` can
	 * turn it off.
	 *
	 * @param string    $request SELECT statement.
	 * @param \WP_Query $query   Current WP_Query.
	 * @return string
	 */
	private static function flat_first( string $request, \WP_Query $query ): string {
		$routed = $query->get( self::QUERY_VAR );
		$sort   = $query->get( self::SORT_VAR );
		if ( empty( $sort ) || ! is_array( $sort ) || ! empty( $query->get( self::COPY_VAR ) ) ) {
			return $request;
		}
		if ( empty( $routed ) || ! is_array( $routed ) ) {
			// Sort only: the LEFT JOIN keeps posts without a flat row, so the
			// flat table may drive only when every post of the type has one.
			$post_type = (string) $sort['post_type'];
			$group     = (string) $sort['group'];
			if ( ! self::covers_all( $post_type, $group ) ) {
				return $request;
			}
		} else {
			$post_type = (string) array_key_first( $routed );
			$groups    = array_unique( array_column( $routed[ $post_type ], 'group' ) );
			$compares  = array_diff( array_column( $routed[ $post_type ], 'compare' ), array( 'NOT EXISTS' ) );
			if ( 1 !== count( $groups ) || empty( $compares ) || $sort['group'] !== $groups[0] ) {
				return $request;
			}
			$group = (string) $groups[0];
		}
		foreach ( array( 'p', 'page_id', 'name', 'pagename', 'attachment_id', 'post__in', 'post_parent', 'post_parent__in', 'author', 'author__in', 'author_name' ) as $var ) {
			if ( ! empty( $query->get( $var ) ) ) {
				return $request;
			}
		}
		if ( ! apply_filters( 'tmdo_router_flat_first', true, $query ) ) {
			return $request;
		}

		global $wpdb;
		$table = $wpdb->prefix . 'wpdo_post_' . sanitize_key( $group );
		$alias = self::table_alias( $post_type, $group );
		$on    = "(`{$wpdb->posts}`.`ID` = `{$alias}`.`post_id`)";
		$join  = " LEFT JOIN `{$table}` AS `{$alias}` ON {$on}";
		if ( 1 !== substr_count( $request, $join ) ) {
			return $request;
		}
		$flat_first = preg_replace(
			'/\bFROM\s+' . preg_quote( $wpdb->posts, '/' ) . '\b/',
			"FROM `{$table}` AS `{$alias}` INNER JOIN {$wpdb->posts} ON {$on}",
			str_replace( $join, '', $request ),
			1,
			$replaced
		);
		if ( 1 !== $replaced ) {
			return $request;
		}
		$flat_first = self::without_group_by( (string) $flat_first );
		// Tie-breaks on posts.ID (ours, and any a plugin appended) read the flat
		// post_id, once, in the sort's direction: a (column, post_id) index then
		// returns rows in order with no filesort. Ties are ordered by ID the same
		// way as the column (natively ID DESC); pagination stays stable.
		$tie        = "`{$alias}`.`post_id` " . ( 'ASC' === strtoupper( (string) $sort['order'] ) ? 'ASC' : 'DESC' );
		$flat_first = preg_replace_callback(
			'/\bORDER BY\b(?!.*\bORDER BY\b).*$/s',
			static function ( $m ) use ( $wpdb, $tie ) {
				$order = (string) preg_replace( '/`?' . preg_quote( $wpdb->posts, '/' ) . '`?\.`?ID`?(?!\w)(\s+(ASC|DESC)\b)?/i', $tie, $m[0] );
				return (string) preg_replace( '/(,\s*' . preg_quote( $tie, '/' ) . ')(\s*,\s*' . preg_quote( $tie, '/' ) . ')+/', '$1', $order );
			},
			(string) $flat_first
		);
		return (string) preg_replace( '/^\s*SELECT\s/', 'SELECT STRAIGHT_JOIN ', (string) $flat_first, 1 );
	}

	/**
	 * A request without its SQL_CALC_FOUND_ROWS.
	 *
	 * @param string $request SELECT statement.
	 * @return string
	 */
	private static function without_found_rows( string $request ): string {
		return (string) preg_replace( '/\bSQL_CALC_FOUND_ROWS\s+/', '', $request, 1 );
	}

	/**
	 * Whether a meta query type casts to a number (NUMERIC, SIGNED, DECIMAL(p,s) …).
	 *
	 * @param string $type Upper-cased clause type.
	 * @return bool
	 */
	private static function is_numeric_type( string $type ): bool {
		return 1 === preg_match( '/^(NUMERIC|SIGNED|UNSIGNED|DECIMAL)(\(\d+(,\s?\d+)?\))?$/', $type );
	}

	/**
	 * Whether ordering by the flat column matches native ordering by
	 * CAST(meta_value AS type): numbers by a numeric type, strings by CHAR.
	 *
	 * @param array{type:string}   $route Routed clause.
	 * @param array<string, mixed> $field Registered field.
	 * @return bool
	 */
	private static function sortable( array $route, array $field ): bool {
		$kind = $field['type'] ?? 'text';
		if ( in_array( $kind, array( 'integer', 'decimal', 'boolean' ), true ) ) {
			return self::is_numeric_type( $route['type'] );
		}
		return in_array( $kind, array( 'text', 'textarea', 'enum' ), true ) && 'CHAR' === $route['type'];
	}

	/**
	 * The ordering a routed meta orderby resolves to.
	 *
	 * @param string                             $post_type Post type slug.
	 * @param array{group:string, column:string} $route     Routed clause.
	 * @param string                             $direction ASC or DESC.
	 * @return array{post_type:string, group:string, column:string, order:string}
	 */
	private static function sort_for( string $post_type, array $route, string $direction ): array {
		return array(
			'post_type' => $post_type,
			'group'     => $route['group'],
			'column'    => $route['column'],
			'order'     => $direction,
		);
	}

	/**
	 * The clause name of a "sort by a key, keep posts without it" group —
	 * relation OR of exactly NOT EXISTS and EXISTS on one key and type, one
	 * of them named (HivePress search sorting) — or '' for any other group.
	 *
	 * @param array<int|string, mixed> $group Nested meta query group.
	 * @return string
	 */
	private static function sort_shape( array $group ): string {
		if ( 'OR' !== strtoupper( (string) ( $group['relation'] ?? '' ) ) ) {
			return '';
		}
		unset( $group['relation'] );
		if ( 2 !== count( $group ) ) {
			return '';
		}
		$name     = '';
		$compares = array();
		foreach ( $group as $k => $clause ) {
			if ( ! is_array( $clause ) || ! is_string( $clause['key'] ?? null ) ) {
				return '';
			}
			$compares[] = strtoupper( (string) ( $clause['compare'] ?? '=' ) );
			$name       = is_string( $k ) ? $k : $name;
		}
		list( $a, $b ) = array_values( $group );
		sort( $compares );
		$same = $a['key'] === $b['key'] && strtoupper( (string) ( $a['type'] ?? '' ) ) === strtoupper( (string) ( $b['type'] ?? '' ) );
		return array( 'EXISTS', 'NOT EXISTS' ) === $compares && $same ? $name : '';
	}

	/**
	 * Generate a deterministic JOIN alias for a (post_type, group) pair.
	 *
	 * @param string $post_type Post type slug.
	 * @param string $group     Entity group name.
	 * @return string SQL alias.
	 */
	private static function table_alias( string $post_type, string $group ): string {
		return 'wpdoflat_' . sanitize_key( $post_type ) . '_' . sanitize_key( $group );
	}

	/**
	 * Allow-list of comparison operators.
	 *
	 * @param string $compare Raw operator from clause.
	 * @return string Sanitized operator (defaults to '=').
	 */
	private static function sanitize_compare( string $compare ): string {
		$compare = strtoupper( trim( $compare ) );
		return in_array( $compare, self::COMPARES, true ) ? $compare : '=';
	}

	/**
	 * Build a single WHERE condition fragment (always prepended with " AND ").
	 *
	 * @param string $col_sql  Quoted column reference.
	 * @param string $compare  Sanitized comparison operator.
	 * @param mixed  $value    Raw value (scalar or array).
	 * @return string
	 */
	private static function build_condition( string $col_sql, string $compare, $value ): string {
		global $wpdb;

		if ( in_array( $compare, array( 'IN', 'NOT IN' ), true ) ) {
			$values = (array) $value;
			if ( empty( $values ) ) {
				return '';
			}
			$placeholders = implode( ',', array_fill( 0, count( $values ), '%s' ) );
			return ' AND ' . $col_sql . ' ' . $compare . ' (' . $wpdb->prepare( $placeholders, ...$values ) . ')';
		}

		if ( in_array( $compare, array( 'BETWEEN', 'NOT BETWEEN' ), true ) ) {
			$values = (array) $value;
			if ( count( $values ) < 2 ) {
				return '';
			}
			return ' AND ' . $col_sql . ' ' . $compare . ' '
				. $wpdb->prepare( '%s AND %s', $values[0], $values[1] );
		}

		if ( in_array( $compare, array( 'EXISTS', 'NOT EXISTS' ), true ) ) {
			$op = 'EXISTS' === $compare ? 'IS NOT NULL' : 'IS NULL';
			return ' AND ' . $col_sql . ' ' . $op;
		}

		if ( in_array( $compare, array( 'LIKE', 'NOT LIKE' ), true ) ) {
			$value = '%' . $wpdb->esc_like( (string) $value ) . '%';
		}

		return ' AND ' . $col_sql . ' ' . $compare . ' ' . $wpdb->prepare( '%s', (string) $value );
	}
}