<?php
/** Bounded, resumable indexing and migration of legacy managed recordings. */
namespace Accessibility_Audio_TTS\Core;

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

class Private_Audio_Migration {
	const STATE = 'accessibility_audio_tts_private_audio_migration_state';
	const FILES_META = '_accessibility_audio_tts_legacy_files';
	const RETRY_META = '_accessibility_audio_tts_migration_retry';
	const HOOK = 'accessibility_audio_tts_private_audio_migration_tick';

	private static function initial_state() {
		return array( 'phase' => 'index', 'stack' => array( array( 'directory' => '', 'offset' => 0, 'last' => null ) ), 'cursor' => 0, 'indexed_files' => 0, 'processed' => 0, 'next_run' => 0, 'error' => '' );
	}

	private static function state() {
		$state = get_option( self::STATE, array() );
		if ( ! is_array( $state ) || ! isset( $state['phase'] ) || ( 'complete' === $state['phase'] && '1' !== get_option( 'accessibility_audio_tts_private_audio_migration', '' ) ) ) { return self::initial_state(); }
		return $state;
	}

	public static function index_complete() { return 'index' !== self::state()['phase']; }

	/** A failed query is never an empty queue or proof that migration finished. */
	private static function read_ids( $query ) {
		global $wpdb;
		$ids = $wpdb->get_col( $query );
		if ( $wpdb->last_error || ! is_array( $ids ) ) { throw new \RuntimeException( 'The audio migration database scan failed. Check the database and retry migration.' ); }
		return $ids;
	}

	private static function pending_count() {
		global $wpdb;
		$count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM {$wpdb->postmeta} WHERE meta_key = %s", self::RETRY_META ) );
		if ( $wpdb->last_error || null === $count || ! is_numeric( $count ) ) { throw new \RuntimeException( 'The audio migration retry count could not be read. Check the database and retry migration.' ); }
		return (int) $count;
	}

	private static function save_state( $state ) {
		global $wpdb;
		update_option( self::STATE, $state, false );
		if ( $wpdb->last_error ) { throw new \RuntimeException( 'The audio migration checkpoint could not be saved. Check the database and retry migration.' ); }
		wp_cache_delete( self::STATE, 'options' );
		if ( get_option( self::STATE ) !== $state || $wpdb->last_error ) { throw new \RuntimeException( 'The audio migration checkpoint could not be saved. Check the database and retry migration.' ); }
	}

	private static function save_retry( $id, $when = null ) {
		global $wpdb;
		if ( null === $when ) { delete_post_meta( $id, self::RETRY_META ); }
		else { update_post_meta( $id, self::RETRY_META, $when ); }
		if ( $wpdb->last_error ) { throw new \RuntimeException( 'The audio migration retry could not be saved. Check the database and retry migration.' ); }
		wp_cache_delete( $id, 'post_meta' );
		$actual = get_post_meta( $id, self::RETRY_META, true );
		if ( $wpdb->last_error || ( null === $when ? '' !== $actual : (string) $actual !== (string) $when ) ) { throw new \RuntimeException( 'The audio migration retry could not be saved. Check the database and retry migration.' ); }
	}

	public static function status() {
		$state = self::state();
		$pending = null;
		try { $pending = self::pending_count(); }
		catch ( \Throwable $error ) { $state['error'] = $error->getMessage(); }
		$complete = 'complete' === $state['phase'] && 0 === $pending && empty( $state['error'] );
		return array( 'complete' => $complete, 'state' => $complete ? 'complete' : ( $pending || ! empty( $state['error'] ) ? 'needs_attention' : 'pending' ), 'phase' => $state['phase'], 'processed' => (int) $state['processed'], 'indexed_files' => (int) $state['indexed_files'], 'cursor' => (int) $state['cursor'], 'pending_failures' => $pending, 'next_run' => (int) $state['next_run'], 'error' => $state['error'] ?? '', 'message' => $complete
			? __( 'Existing audio migration is complete.', 'accessibility-audio-tts-text-to-speech-for-articles' )
			: __( 'Existing audio migration is pending. Some old static audio URLs may still be public. Finish migration during maintenance before reopening protected content.', 'accessibility-audio-tts-text-to-speech-for-articles' ) );
	}

	private static function schedule() {
		if ( ! wp_next_scheduled( self::HOOK ) ) { wp_schedule_single_event( time() + 60, self::HOOK ); }
	}

	/** One request processes at most 250 directory entries and 20 posts by default. */
	public static function run_batch( $force = false, $post_limit = 20, $file_limit = 250 ) {
		$state = self::state();
		if ( 'complete' === $state['phase'] ) { return self::status(); }
		if ( ! $force && $state['next_run'] > time() ) { self::schedule(); return self::status(); }
		// Reserved post 0 is never a generated article. Reuse the atomic token-owned lease.
		$lease = Generation_Lease::acquire( 0 );
		if ( ! $lease ) { $status = self::status(); $status['busy'] = true; return $status; }
		$deadline = microtime( true ) + 3;
		$post_limit = max( 1, min( 100, (int) $post_limit ) );
		$file_limit = max( 1, min( 1000, (int) $file_limit ) );
		$failed = 0;
		$batch_error = '';
		try {
			// Re-read only after exclusive ownership; an earlier request may have advanced it.
			$state = self::state();
			$checkpoint = $state;
			$state['error'] = '';
			if ( 'index' === $state['phase'] ) {
				$checkpoint = $state;
				try { self::index_files( $state, $file_limit, $deadline, $lease ); }
				catch ( \Throwable $error ) { $state = $checkpoint; throw $error; }
			}
			if ( 'posts' === $state['phase'] && microtime( true ) < $deadline ) {
				global $wpdb;
				$ids = self::read_ids( $wpdb->prepare( "SELECT DISTINCT post_id FROM {$wpdb->postmeta} WHERE post_id > %d AND meta_key IN ('accessibility_audio_tts_url','accessibility_audio_tts_file_data','accessibility_audio_tts_generated','_accessibility_audio_tts_legacy_files') ORDER BY post_id ASC LIMIT %d", $state['cursor'], $post_limit ) );
				foreach ( $ids as $id ) {
					if ( microtime( true ) >= $deadline || ! $lease->renew() ) { break; }
					if ( ! self::migrate_post( (int) $id ) ) { ++$failed; }
					$state['cursor'] = (int) $id;
					++$state['processed'];
				}
				if ( empty( $ids ) ) { $state['phase'] = 'retry'; }
			}
			if ( 'retry' === $state['phase'] && microtime( true ) < $deadline ) {
				global $wpdb;
				$due = $force ? PHP_INT_MAX : time();
				$ids = self::read_ids( $wpdb->prepare( "SELECT DISTINCT post_id FROM {$wpdb->postmeta} WHERE meta_key = %s AND CAST(meta_value AS UNSIGNED) <= %d ORDER BY post_id ASC LIMIT %d", self::RETRY_META, $due, $post_limit ) );
				foreach ( $ids as $id ) {
					if ( microtime( true ) >= $deadline || ! $lease->renew() ) { break; }
					if ( ! self::migrate_post( (int) $id ) ) { ++$failed; }
				}
				$pending = self::pending_count();
				if ( 0 === $pending ) { $state['phase'] = 'complete'; }
			}
			$state['next_run'] = time() + 10;
			if ( $lease->owns() ) {
				self::save_state( $state );
				if ( 'complete' === $state['phase'] ) { update_option( 'accessibility_audio_tts_private_audio_migration', '1', false ); wp_clear_scheduled_hook( self::HOOK ); }
				else { self::schedule(); }
			}
		} catch ( \Throwable $error ) {
			$state = $checkpoint ?? $state;
			$batch_error = $error->getMessage();
			$state['error'] = $batch_error; $state['next_run'] = time() + 300;
			if ( $lease->owns() ) { delete_option( 'accessibility_audio_tts_private_audio_migration' ); update_option( self::STATE, $state, false ); self::schedule(); }
		} finally { $lease->release(); }
		$status = self::status(); $status['failed_in_batch'] = $failed;
		if ( $batch_error ) { $status['complete'] = false; $status['state'] = 'needs_attention'; $status['error'] = $batch_error; }
		return $status;
	}

	private static function index_files( &$state, $limit, $deadline, $lease ) {
		$uploads = wp_upload_dir();
		$root = realpath( $uploads['basedir'] . '/accessibility-audio-tts' );
		if ( false === $root ) { $state['stack'] = array(); $state['phase'] = 'posts'; return; }
		$count = 0;
		$indexed = array();
		$walkers = array();
		while ( $state['stack'] && $count < $limit && microtime( true ) < $deadline ) {
			$key = count( $state['stack'] ) - 1;
			$frame = $state['stack'][ $key ];
			$directory = $root . ( '' === $frame['directory'] ? '' : '/' . $frame['directory'] );
			$real = realpath( $directory );
			if ( ! $real || is_link( $directory ) || 0 !== strpos( wp_normalize_path( $real ) . '/', rtrim( wp_normalize_path( $root ), '/' ) . '/' ) ) { array_pop( $state['stack'] ); continue; }
			$offset = (int) $frame['offset'];
			// Anchor the cursor to its previous filename. Deletions between requests reset
			// only this directory, so a protection transition cannot make us skip entries.
			if ( ! isset( $walkers[ $directory ] ) ) {
				$iterator = new \DirectoryIterator( $directory );
				if ( $offset > 0 ) {
					try { $iterator->seek( $offset - 1 ); if ( ! $iterator->valid() || $iterator->getFilename() !== $frame['last'] ) { $offset = 0; } }
					catch ( \OutOfBoundsException $error ) { $offset = 0; }
				}
				try { $iterator->seek( $offset ); } catch ( \OutOfBoundsException $error ) { array_pop( $state['stack'] ); continue; }
				$walkers[ $directory ] = $iterator;
			}
			$iterator = $walkers[ $directory ];
			if ( ! $iterator->valid() ) { array_pop( $state['stack'] ); continue; }
			$name = $iterator->getFilename();
			$entry = $iterator->getFileInfo();
			$iterator->next();
			$state['stack'][ $key ]['offset'] = $offset + 1;
			$state['stack'][ $key ]['last'] = $name;
			++$count;
			if ( '.' === $name || '..' === $name || $entry->isLink() ) { continue; }
			$relative = ltrim( $frame['directory'] . '/' . $name, '/' );
			if ( $entry->isDir() ) { $state['stack'][] = array( 'directory' => $relative, 'offset' => 0, 'last' => null ); continue; }
			if ( ! $entry->isFile() || ! in_array( strtolower( $entry->getExtension() ), array( 'mp3', 'wav', 'ogg' ), true ) ) { continue; }
			if ( preg_match( '/^(?:accessibility_audio_tts_(\d+)_|post_(\d+)_chunk_|post[-_](\d+)[-_]audio|audio_(\d+)\.)/', $name, $matches ) ) {
				$id = max( array_map( 'intval', array_slice( $matches, 1 ) ) );
				if ( $id > 0 && get_post( $id ) ) { $indexed[ $id ][] = $relative; ++$state['indexed_files']; }
			}
		}
		foreach ( $indexed as $id => $files ) {
			if ( ! $lease->renew() ) { throw new \RuntimeException( 'The audio migration lease changed owner. This batch stopped.' ); }
			$old = get_post_meta( $id, self::FILES_META, true );
			$expected = array_values( array_unique( array_merge( is_array( $old ) ? $old : array(), $files ) ) );
			update_post_meta( $id, self::FILES_META, $expected );
			if ( get_post_meta( $id, self::FILES_META, true ) !== $expected ) { throw new \RuntimeException( 'The legacy audio index could not be saved. Check the database before continuing migration.' ); }
		}
		if ( ! $state['stack'] ) { $state['phase'] = 'posts'; }
	}

	private static function migrate_post( $id ) {
		$post = get_post( $id );
		if ( ! $post || ! Audio_Access::is_restricted( $post ) ) { self::save_retry( $id ); return true; }
		$lease = Generation_Lease::acquire( $id );
		if ( ! $lease ) { self::save_retry( $id, time() + 60 ); return false; }
		$previous = $lease->activate();
		try {
			Audio_Access::protect_post( $id, false, true );
			self::save_retry( $id );
			return true;
		} catch ( \Throwable $error ) {
			self::save_retry( $id, time() + 300 );
			Audio_Access::remember_migration_error( $id, $error );
			return false;
		} finally { $lease->deactivate( $previous ); $lease->release(); }
	}
}