<?php

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

class AIEO_Space_Reclaim {

	
	const OPTION = 'aieo_space_reclaim';

	
	const STATE = 'aieo_space_reclaim_state';

	
	const HOOK = 'aieo_space_reclaim_run';

	const MIN_FREE_MB    = 64;
	const MIN_FREE_SHARE = 0.10;
	const LOCK_WAIT      = 10;

	
	const SKIP = array( 'aieo_temp_orders', 'aieo_customer_purchases', 'aieo_customer_purchases_staging', 'aieo_repair_sessions', 'aieo_repair_statics', 'aieo_repair_journeys', 'aieo_repair_engagement' );

	

	
	public static function schedule_choice() {
		$saved = get_option( self::OPTION );
		$value = is_array( $saved ) ? (string) ( $saved['schedule'] ?? '' ) : '';
		return in_array( $value, array( 'off', 'weekly', 'monthly' ), true ) ? $value : 'monthly';
	}

	
	public static function save( $schedule ) {
		$schedule = in_array( $schedule, array( 'off', 'weekly', 'monthly' ), true ) ? $schedule : 'monthly';
		update_option( self::OPTION, array( 'schedule' => $schedule ), true ); 
		self::schedule( true );
		return $schedule;
	}

	
	public static function schedule( $again = false ) {
		$choice = self::schedule_choice();
		$next   = wp_next_scheduled( self::HOOK );
		if ( $next && ! $again && 'off' !== $choice ) {
			return;
		}
		wp_clear_scheduled_hook( self::HOOK );
		if ( 'off' === $choice ) {
			return;
		}
		$schedules = wp_get_schedules();
		$recur     = isset( $schedules[ $choice ] ) ? $choice : 'weekly';
		$hour      = class_exists( 'AIEO_Data_Retention' ) ? ( AIEO_Data_Retention::settings()['hour'] + 1 ) % 24 : 5;
		$at        = strtotime( gmdate( 'Y-m-d' ) . sprintf( ' %02d:30:00 UTC', $hour ) );
		if ( $at <= time() ) {
			$at += DAY_IN_SECONDS;
		}
		wp_schedule_event( $at, $recur, self::HOOK );
	}

	

	
	public static function unavailable() {
		global $wpdb;
		$fpt = strtoupper( (string) $wpdb->get_var( 'SELECT @@innodb_file_per_table' ) );
		if ( '1' !== $fpt && 'ON' !== $fpt ) {
			return __( 'This database keeps its tables in one shared file, so rebuilding a table gives no space back to the disk.', 'ai-eshop-optimizer' );
		}
		return '';
	}

	
	public static function candidates() {
		global $wpdb;
		if ( '' !== self::unavailable() ) {
			return array();
		}
		$rows = $wpdb->get_results( $wpdb->prepare(
			"SELECT TABLE_NAME AS t, TABLE_ROWS AS r, DATA_LENGTH AS d, INDEX_LENGTH AS i, DATA_FREE AS f, ENGINE AS e
			   FROM INFORMATION_SCHEMA.TABLES
			  WHERE TABLE_SCHEMA = DATABASE() AND TABLE_TYPE = 'BASE TABLE' AND TABLE_NAME LIKE %s",
			$wpdb->esc_like( $wpdb->prefix . 'aieo_' ) . '%'
		), ARRAY_A );
		return self::pick( (array) $rows, $wpdb->prefix );
	}

	
	public static function pick( array $rows, $prefix ) {
		$skip = self::SKIP;
		if ( class_exists( 'AIEO_Analytics_Collation' ) ) {
			$skip = array_merge( $skip, AIEO_Analytics_Collation::built_tables() );
		}
		$out = array();
		foreach ( $rows as $row ) {
			$table = (string) ( $row['t'] ?? '' );
			$short = substr( $table, strlen( $prefix ) );
			if ( 0 !== strpos( $table, $prefix . 'aieo_' ) || in_array( $short, $skip, true ) || 'InnoDB' !== (string) ( $row['e'] ?? '' ) || ! preg_match( '/^[A-Za-z0-9_]+$/', $table ) ) {
				continue;
			}
			$size = (float) ( $row['d'] ?? 0 ) + (float) ( $row['i'] ?? 0 );
			$free = (float) ( $row['f'] ?? 0 );
			if ( $free < self::MIN_FREE_MB * 1048576 || $free < self::MIN_FREE_SHARE * ( $size + $free ) ) {
				continue;
			}
			$out[] = array(
				'table'    => $table,
				'rows'     => (int) ( $row['r'] ?? 0 ),
				'data_mb'  => round( (float) ( $row['d'] ?? 0 ) / 1048576, 1 ),
				'index_mb' => round( (float) ( $row['i'] ?? 0 ) / 1048576, 1 ),
				'free_mb'  => round( $free / 1048576, 1 ),
			);
		}
		usort( $out, static function ( $a, $b ) { return $b['free_mb'] <=> $a['free_mb']; } );
		return $out;
	}

	

	
	public static function step( array $tried = array() ) {
		$tried = array_flip( array_map( 'strval', $tried ) );
		$list  = array_values( array_filter( self::candidates(), static function ( $c ) use ( $tried ) { return ! isset( $tried[ $c['table'] ] ); } ) );
		if ( ! $list ) {
			return array( 'table' => '', 'freed_mb' => 0.0, 'error' => '', 'left' => 0 );
		}
		$done         = self::rebuild( $list[0] );
		$done['left'] = count( $list ) - 1;
		self::remember( $done );
		return $done;
	}

	
	public static function run( $budget = 600.0 ) {
		$t0    = microtime( true );
		$tried = array();
		while ( microtime( true ) - $t0 < $budget ) {
			$list = array_values( array_filter( self::candidates(), static function ( $c ) use ( $tried ) { return ! isset( $tried[ $c['table'] ] ); } ) );
			if ( ! $list ) {
				break;
			}
			$done                    = self::rebuild( $list[0] );
			$tried[ $done['table'] ] = true;
			self::remember( $done );
		}
	}

	
	private static function rebuild( array $c ) {
		global $wpdb;
		$table = (string) $c['table'];
		$need  = ( (float) $c['data_mb'] + (float) $c['index_mb'] ) * 1048576 * 1.2;
		$room  = self::disk_room();
		if ( null !== $room && $room < $need ) {
			return array( 'table' => $table, 'freed_mb' => 0.0, 'error' => __( 'not enough free disk for the copy', 'ai-eshop-optimizer' ) );
		}
		$wpdb->query( $wpdb->prepare( 'SET SESSION lock_wait_timeout = %d', self::LOCK_WAIT ) );
		$ok  = $wpdb->query( "ALTER TABLE `{$table}` ENGINE=InnoDB, ALGORITHM=INPLACE, LOCK=NONE" );
		$err = false === $ok ? (string) $wpdb->last_error : '';
		$after = (float) $wpdb->get_var( $wpdb->prepare( 'SELECT DATA_FREE FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = %s', $table ) );
		return array(
			'table'    => $table,
			'freed_mb' => '' === $err ? max( 0.0, round( (float) $c['free_mb'] - $after / 1048576, 1 ) ) : 0.0,
			'error'    => $err,
		);
	}

	
	private static function disk_room() {
		global $wpdb;
		$dir = (string) $wpdb->get_var( 'SELECT @@datadir' );
		if ( '' === $dir || ! function_exists( 'disk_free_space' ) || ! @is_dir( $dir ) ) { 
			return null;
		}
		$free = @disk_free_space( $dir ); 
		return false === $free ? null : (float) $free;
	}

	
	private static function remember( array $done ) {
		$state = (array) get_option( self::STATE, array() );
		$list  = isset( $state['tables'] ) && is_array( $state['tables'] ) ? $state['tables'] : array();
		array_unshift( $list, array( 'table' => $done['table'], 'freed_mb' => $done['freed_mb'], 'error' => $done['error'], 'at' => gmdate( 'Y-m-d H:i:s' ) ) );
		update_option( self::STATE, array( 'at' => gmdate( 'Y-m-d H:i:s' ), 'tables' => array_slice( $list, 0, 20 ) ), false );
	}
}