<?php
/**
 * Zone A (Hot) handler for flat-column custom tables.
 *
 * @package WP_Data_Optimizer
 */

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

/**
 * Zone A (Hot) handler — flat-column custom tables for search/filter fields.
 *
 * Each post type gets its own table: wpdo_hot_{post_type}
 * Columns are defined by the Schema Registry and created via TMDO_Installer.
 *
 * Key advantage over HPCT's KV table (hpct_listing_meta):
 *   KV table: N meta_query conditions = N LEFT JOINs
 *   Flat table: N conditions = 1 LEFT JOIN + N WHERE clauses
 */
class TMDO_Zone_Hot {

	/**
	 * Get the table name for a post type.
	 *
	 * @param string $post_type Post type slug.
	 * @return string Full table name.
	 */
	public static function table( string $post_type ): string {
		return TMDO_DB::table( 'wpdo_hot_' . sanitize_key( $post_type ) );
	}

	/**
	 * Ensure the hot table exists for a post type.
	 * Creates it dynamically from Schema Registry if missing.
	 *
	 * @param string $post_type Post type slug.
	 * @return void
	 */
	public static function ensure_table( string $post_type ): void {
		$columns = TMDO_Schema_Registry::instance()->get_hot_columns( $post_type );
		if ( empty( $columns ) ) {
			return;
		}

		global $wpdb;
		$table = self::table( $post_type );

		// Quick existence check.
		if ( TMDO_IS_SQLITE ) {
			$exists = $wpdb->get_var(
				$wpdb->prepare( "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name=%s", $table )
			);
		} else {
			$exists = $wpdb->get_var(
				$wpdb->prepare( 'SELECT COUNT(*) FROM information_schema.TABLES WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = %s', $table )
			);
		}

		if ( ! $exists ) {
			TMDO_Installer::create_hot_table( $post_type, $columns );
			return;
		}

		// v2.1.2 critical fix: ensure existing tables have all columns declared
		// by Schema_Registry. Partner plugins registering new hot fields after
		// the initial migration would otherwise silently fall back to postmeta.
		//
		// v2.1.3 optimization: schema fingerprint stored in option. When the hash
		// of declared columns matches the stored hash, skip SHOW COLUMNS entirely.
		// Only diff + ALTER fires when fingerprint actually changed (drift detected).
		// This avoids per-request SHOW COLUMNS overhead on stable production sites.
		static $checked = array();
		if ( isset( $checked[ $post_type ] ) ) {
			return;
		}

		$fingerprint = self::compute_fingerprint( $columns );
		$opt_key     = 'wpdo_hot_fp_' . $post_type;
		$stored_fp   = (string) get_option( $opt_key, '' );

		if ( $stored_fp === $fingerprint ) {
			// Schema unchanged since last successful ensure → no need to SHOW COLUMNS.
			$checked[ $post_type ] = true;
			return;
		}

		// Fingerprint mismatch (or first run) → run diff + ALTER, then store new hash.
		TMDO_Installer::ensure_hot_columns( $post_type, $columns );
		update_option( $opt_key, $fingerprint, false );
		$checked[ $post_type ] = true;
	}

	/**
	 * Stable hash of declared column definitions. Used to short-circuit SHOW COLUMNS
	 * when Schema_Registry hasn't changed since the last successful ensure.
	 *
	 * @param array $columns column_name => sql_type map.
	 * @return string Short SHA-1 prefix (10 chars — collision-safe at our scale).
	 *
	 * @since 2.1.3
	 */
	private static function compute_fingerprint( array $columns ): string {
		ksort( $columns );
		return substr( sha1( wp_json_encode( $columns ) ?: '' ), 0, 10 );
	}

	/**
	 * Read a single field value from the hot table.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @param string $column    Column name in hot table.
	 * @return mixed|null Value or null if not found.
	 */
	public static function get( int $post_id, string $post_type, string $column ): mixed {
		global $wpdb;
		$table  = self::table( $post_type );
		$column = sanitize_key( $column );

		return $wpdb->get_var(
			$wpdb->prepare(
				"SELECT `{$column}` FROM `{$table}` WHERE post_id = %d LIMIT 1", // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- column from sanitize_key(); table from TMDO_DB::table().
				$post_id
			)
		);
	}

	/**
	 * Read all hot fields for a post as an associative array.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @return array|null Column => value pairs, or null.
	 */
	public static function get_row( int $post_id, string $post_type ): ?array {
		global $wpdb;
		$table = self::table( $post_type );

		$row = $wpdb->get_row(
			$wpdb->prepare( "SELECT * FROM `{$table}` WHERE post_id = %d LIMIT 1", $post_id ), // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name from TMDO_Zone_Hot::table() via TMDO_DB::table().
			ARRAY_A
		);

		return $row ?: null;
	}

	/**
	 * Upsert a single field into the hot table.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @param string $column    Column name.
	 * @param mixed  $value     Value to set.
	 */
	public static function set( int $post_id, string $post_type, string $column, mixed $value ): void {
		$table  = self::table( $post_type );
		$column = sanitize_key( $column );
		$now    = TMDO_DB::now();

		TMDO_DB::upsert(
			$table,
			array(
				'post_id'    => $post_id,
				$column      => $value,
				'updated_at' => $now,
			),
			array( $column, 'updated_at' ),
			'post_id'
		);
	}

	/**
	 * Upsert multiple fields at once for a post.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @param array  $data      Column => value pairs.
	 */
	public static function set_many( int $post_id, string $post_type, array $data ): void {
		$table = self::table( $post_type );
		$now   = TMDO_DB::now();

		$data['post_id']    = $post_id;
		$data['updated_at'] = $now;
		$update_cols        = array_diff( array_keys( $data ), array( 'post_id' ) );

		TMDO_DB::upsert( $table, $data, $update_cols, 'post_id' );
	}

	/**
	 * Delete a post's row from the hot table.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type slug.
	 * @return void
	 */
	public static function delete( int $post_id, string $post_type ): void {
		global $wpdb;
		$wpdb->delete( self::table( $post_type ), array( 'post_id' => $post_id ), array( '%d' ) );
	}

	/**
	 * Get all post types that have hot zone tables registered.
	 *
	 * @return string[]
	 */
	public static function get_post_types(): array {
		return TMDO_Schema_Registry::instance()->get_hot_post_types();
	}
}