<?php
/** Bounded, resumable historical timestamp conversion with retained originals. @package AccessibleForms */
namespace AccessibleForms;

// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Prepared operations on the plugin's entry table and verified migration state.
if ( ! defined( 'ABSPATH' ) ) { exit(); }

class TimeMigration {
	const OPTION = 'accessible_forms_time_migration';
	const HOOK = 'accessible_forms_time_migration';
	const BATCH = 200;

	/** WordPress's native timezone menu also uses values such as UTC+5.5. */
	public static function zone_name( $value ) {
		if ( ! is_string( $value ) ) { return ''; }
		if ( preg_match( '/^UTC([+-])(\d{1,2})(?:\.(5|25|75))?$/D', $value, $match ) ) {
			$minutes = (int) $match[2] * 60 + (int) round( (float) ( '0.' . ( $match[3] ?? '0' ) ) * 60 );
			if ( $minutes > 14 * 60 ) { return ''; }
			$value = sprintf( '%s%02d:%02d', $match[1], (int) floor( $minutes / 60 ), $minutes % 60 );
		}
		return in_array( $value, \DateTimeZone::listIdentifiers( \DateTimeZone::ALL_WITH_BC ), true ) || preg_match( '/^[+-](?:0\d|1[0-3]):[0-5]\d$|^[+-]14:00$/D', $value ) ? $value : '';
	}

	public static function register() {
		add_action( self::HOOK, array( self::class, 'batch' ) );
		add_action( 'init', array( self::class, 'resume' ), 6 );
	}

	public static function pending() {
		global $wpdb;
		return (int) $wpdb->get_var( $wpdb->prepare( 'SELECT COUNT(*) FROM %i WHERE time_version <> %d', Entries::table_name(), EntryTime::VERSION ) );
	}

	/** Rollback must cover both converted entries and the option checkpoint. */
	private static function transactions_ready() {
		global $wpdb;
		$rows = $wpdb->get_results( $wpdb->prepare( 'SHOW TABLE STATUS WHERE Name IN (%s, %s)', Entries::table_name(), $wpdb->options ), ARRAY_A );
		if ( $wpdb->last_error || 2 !== count( $rows ?: array() ) ) { return false; }
		foreach ( $rows as $row ) {
			if ( ! in_array( strtolower( (string) $row['Engine'] ), array( 'innodb', 'xtradb' ), true ) ) { return false; }
		}
		return true;
	}

	public static function start( $zone, $policy, $confirmed, $form_id = 0 ) {
		if ( ! current_user_can( 'manage_accessible_forms_settings' ) || ! $confirmed ) {
			return new \WP_Error( 'confirmation', __( 'Confirm the original time zone before converting historical dates.', 'accessible-forms-by-accessible-org' ) );
		}
		$zone = self::zone_name( $zone );
		if ( ! $zone || ! in_array( $policy, array( 'preserve', 'earlier', 'later' ), true ) ) {
			return new \WP_Error( 'timezone', __( 'Choose a valid original time zone and repeated-hour policy.', 'accessible-forms-by-accessible-org' ) );
		}
		$form_id = absint( $form_id );
		if ( $form_id && ( 'accessible_form' !== get_post_type( $form_id ) || ! Capabilities::form( $form_id, 'manage_accessible_form_entries' ) ) ) {
			return new \WP_Error( 'form', __( 'Choose a form whose entries you can manage.', 'accessible-forms-by-accessible-org' ) );
		}
		if ( ! self::transactions_ready() ) {
			return new \WP_Error( 'transactions', __( 'Historical date conversion requires transactional entry and options tables. Ask your hosting provider to enable InnoDB; dates are unchanged.', 'accessible-forms-by-accessible-org' ) );
		}
		$lease = Locks::acquire( 'time_migration', 5 * MINUTE_IN_SECONDS );
		if ( ! $lease ) { return new \WP_Error( 'busy', __( 'A historical date batch is running. Try again shortly.', 'accessible-forms-by-accessible-org' ) ); }
		try {
			self::fresh_state();
			$previous = get_option( self::OPTION, array() );
			if ( 'running' === ( $previous['status'] ?? '' ) ) { return new \WP_Error( 'busy', __( 'Finish the current historical date conversion first.', 'accessible-forms-by-accessible-org' ) ); }
			global $wpdb;
			$state = array( 'version' => 1, 'zone' => $zone, 'policy' => $policy, 'form_id' => $form_id, 'cursor' => 0, 'max_id' => (int) $wpdb->get_var( $wpdb->prepare( 'SELECT MAX(id) FROM %i', Entries::table_name() ) ), 'converted' => 0, 'unconfirmed' => 0, 'status' => 'running' );
			if ( ! Persistence::option( self::OPTION, $state, false ) ) { return new \WP_Error( 'storage', __( 'The conversion could not be saved. Historical dates are unchanged.', 'accessible-forms-by-accessible-org' ) ); }
			self::resume();
			Audit::record( 'historical_dates_confirmed', $form_id );
			return true;
		} finally { Locks::release( $lease ); }
	}

	public static function resume() {
		$state = get_option( self::OPTION, array() );
		if ( 'running' === ( $state['status'] ?? '' ) && ! wp_next_scheduled( self::HOOK ) ) { wp_schedule_single_event( time() + 30, self::HOOK ); }
	}

	/** A request may have read this option before another worker advanced it. */
	private static function fresh_state() {
		wp_cache_delete( self::OPTION, 'options' );
		wp_cache_delete( 'alloptions', 'options' );
		wp_cache_delete( 'notoptions', 'options' );
	}

	public static function batch() {
		global $wpdb;
		$transaction = false;
		$lease = Locks::acquire( 'time_migration', 5 * MINUTE_IN_SECONDS );
		if ( ! $lease ) { return 0; }
		try {
			self::fresh_state();
			$state = get_option( self::OPTION, array() );
			if ( 'running' !== ( $state['status'] ?? '' ) ) { return 0; }
			if ( ! self::transactions_ready() ) { self::resume(); return 0; }
			try { $zone = new \DateTimeZone( $state['zone'] ); } catch ( \Exception $error ) { return 0; }
			$ids = $wpdb->get_col( $wpdb->prepare(
				'SELECT id FROM %i WHERE id > %d AND id <= %d AND time_version <> %d AND (%d = 0 OR form_id = %d) ORDER BY id LIMIT %d',
				Entries::table_name(), $state['cursor'], $state['max_id'], EntryTime::VERSION, $state['form_id'], $state['form_id'], self::BATCH
			) );
			if ( $wpdb->last_error ) { self::resume(); return 0; }
			if ( false === $wpdb->query( 'BEGIN' ) ) { self::resume(); return 0; }
			$transaction = true;
			$failed = false;
			$processed = 0;
			foreach ( $ids as $id ) {
				$row_lease = Locks::acquire( 'entry:' . (int) $id );
				if ( ! $row_lease ) { $failed = true; break; }
				try {
					$row = $wpdb->get_row( $wpdb->prepare( 'SELECT id, created_at, resolved_at, first_reply_at, time_version, time_original, retention_days, expires_at FROM %i WHERE id = %d FOR UPDATE', Entries::table_name(), $id ), ARRAY_A );
					if ( $wpdb->last_error ) { $failed = true; break; }
					if ( $row ) {
						$mask = (int) $row['time_version']; $data = array();
						$original = json_decode( (string) ( $row['time_original'] ?? '' ), true ) ?: array();
						foreach ( EntryTime::FIELDS as $column => $bit ) {
							if ( $mask & $bit ) { continue; }
							if ( ! $row[ $column ] && 'created_at' !== $column ) { $mask |= $bit; continue; }
							$utc = EntryTime::historical( $row[ $column ], $zone, $state['policy'] );
							if ( null === $utc ) { continue; }
							$original[ $column ] = array( 'value' => $row[ $column ], 'zone' => $state['zone'], 'policy' => $state['policy'] );
							$data[ $column ] = $utc; $mask |= $bit;
						}
						// Imported dates acquire a retention deadline only after their timezone is confirmed.
						if ( isset( $data['created_at'] ) && empty( $row['expires_at'] ) && (int) $row['retention_days'] > 0 ) {
							$data['expires_at'] = EntryTime::utc( EntryTime::parse( $data['created_at'] ) + (int) $row['retention_days'] * DAY_IN_SECONDS );
						}
						$data['time_version'] = $mask;
						$data['time_original'] = $original ? wp_json_encode( $original ) : null;
						if ( false === $wpdb->update( Entries::table_name(), $data, array( 'id' => (int) $id, 'time_version' => (int) $row['time_version'] ) ) ) { $failed = true; break; }
						++$state[ EntryTime::VERSION === $mask ? 'converted' : 'unconfirmed' ];
					}
					$state['cursor'] = (int) $id; ++$processed;
				} finally { Locks::release( $row_lease ); }
			}
			if ( count( $ids ) < self::BATCH && $processed === count( $ids ) ) { $state['status'] = $state['unconfirmed'] ? 'review' : 'complete'; }
			// Conversion and checkpoint share a transaction: failure cannot lose originals,
			// advance the cursor or inflate progress counts. Per-column bits prevent replays.
			if ( $failed || ! Persistence::option( self::OPTION, $state, false ) || false === $wpdb->query( 'COMMIT' ) ) {
				$wpdb->query( 'ROLLBACK' ); $transaction = false;
				wp_cache_delete( self::OPTION, 'options' ); wp_cache_delete( 'alloptions', 'options' );
				self::resume(); return 0;
			}
			$transaction = false;
			self::resume();
			return $processed;
		} finally {
			if ( $transaction ) { $wpdb->query( 'ROLLBACK' ); wp_cache_delete( self::OPTION, 'options' ); wp_cache_delete( 'alloptions', 'options' ); }
			Locks::release( $lease );
		}
	}
}