<?php
/**
 * Caption track storage: one WebVTT file per attachment and language.
 *
 * Files live in uploads/captionwright/{attachment-id}-{lang}.vtt so they work the
 * same whether or not the media file itself is stored locally.
 *
 * @package Captionwright
 */

namespace Captionwright;

defined( 'ABSPATH' ) || exit;

const META = '_captionwright_tracks';

// The free plugin and Pro share this folder, so Pro keeps the free plugin's captions.
const UPLOAD_DIR = 'captionwright';

// Pro 1.0.0 and 1.0.1 saved caption files here by mistake; they are moved to UPLOAD_DIR.
const LEGACY_DIR = 'captionwright-pro';

/**
 * Filesystem helper (direct access, as uploads must be writable anyway).
 *
 * @return \WP_Filesystem_Base|false
 */
function fs() {
	global $wp_filesystem;
	if ( ! function_exists( 'WP_Filesystem' ) ) {
		require_once ABSPATH . 'wp-admin/includes/file.php';
	}
	if ( ! $wp_filesystem && ! WP_Filesystem( false, false, true ) ) {
		return false;
	}
	return $wp_filesystem;
}

/**
 * Uploads sub-directory for caption files.
 *
 * @return array{dir:string,url:string}
 */
function storage() {
	$up = wp_upload_dir( null, false );
	return array(
		'dir' => trailingslashit( $up['basedir'] ) . UPLOAD_DIR,
		'url' => trailingslashit( $up['baseurl'] ) . UPLOAD_DIR,
	);
}

/**
 * Move caption files saved by Pro 1.0.0–1.0.1 (uploads/captionwright-pro/) into
 * the shared folder. A newer file already in the shared folder wins. The old
 * folder is removed only when no caption file is left in it.
 */
function move_legacy_files() {
	if ( get_option( 'captionwright_folder_checked' ) ) {
		return;
	}
	$fs = fs();
	if ( ! $fs ) {
		return;
	}
	$up     = wp_upload_dir( null, false );
	$legacy = trailingslashit( $up['basedir'] ) . LEGACY_DIR;
	if ( $fs->is_dir( $legacy ) ) {
		$st = storage();
		if ( ! $fs->is_dir( $st['dir'] ) && ! wp_mkdir_p( $st['dir'] ) ) {
			return;
		}
		foreach ( array_keys( (array) $fs->dirlist( $legacy ) ) as $name ) {
			if ( ! preg_match( '/^\d+-[a-z0-9-]+\.vtt$/', $name ) ) {
				continue;
			}
			$old = $legacy . '/' . $name;
			$new = $st['dir'] . '/' . $name;
			if ( $fs->exists( $new ) && $fs->mtime( $new ) >= $fs->mtime( $old ) ) {
				$fs->delete( $old );
			} else {
				$fs->move( $old, $new, true );
			}
		}
		if ( ! $fs->exists( $st['dir'] . '/.htaccess' ) ) {
			$fs->put_contents( $st['dir'] . '/.htaccess', "AddType text/vtt .vtt\nAddCharset utf-8 .vtt\n", FS_CHMOD_FILE );
		}
		$left = array_filter( array_keys( (array) $fs->dirlist( $legacy ) ), fn( $n ) => '.htaccess' !== $n );
		if ( $left ) {
			return; // Something could not be moved: keep the folder and try again next time.
		}
		$fs->rmdir( $legacy, true );
	}
	update_option( 'captionwright_folder_checked', 1, true );
}
add_action( 'init', __NAMESPACE__ . '\move_legacy_files' );

/**
 * Whether a language code looks valid (en, sv, pt-br …).
 *
 * @param string $lang Code.
 * @return bool
 */
function valid_lang( $lang ) {
	return (bool) preg_match( '/^[a-z]{2,3}(-[a-z0-9]{2,8})?$/', (string) $lang );
}

/**
 * Tracks saved for an attachment, keyed by language.
 *
 * @param int $id Attachment ID.
 * @return array<string, array{label:string,updated:int,cues:int,url:string}>
 */
function get_tracks( $id ) {
	$meta = get_post_meta( (int) $id, META, true );
	if ( ! is_array( $meta ) ) {
		return array();
	}
	$base = storage();
	$out  = array();
	foreach ( $meta as $lang => $t ) {
		if ( ! valid_lang( $lang ) || ! is_array( $t ) ) {
			continue;
		}
		$updated      = isset( $t['updated'] ) ? (int) $t['updated'] : 0;
		$out[ $lang ] = array(
			'label'   => isset( $t['label'] ) ? (string) $t['label'] : $lang,
			'updated' => $updated,
			'cues'    => isset( $t['cues'] ) ? (int) $t['cues'] : 0,
			'url'     => add_query_arg( 'ver', $updated, $base['url'] . '/' . (int) $id . '-' . $lang . '.vtt' ),
		);
	}
	return $out;
}

/**
 * Normalise and check WebVTT text from the browser.
 *
 * @param string $vtt Raw text.
 * @return string|\WP_Error
 */
function clean_vtt( $vtt ) {
	$vtt = str_replace( array( "\r\n", "\r" ), "\n", (string) $vtt );
	$vtt = preg_replace( '/^\xEF\xBB\xBF/', '', $vtt );
	if ( strlen( $vtt ) > 2 * MB_IN_BYTES ) {
		return new \WP_Error( 'captionwright_too_big', __( 'The caption file is larger than 2 MB.', 'captionwright' ), array( 'status' => 400 ) );
	}
	if ( 0 !== strpos( ltrim( $vtt ), 'WEBVTT' ) ) {
		return new \WP_Error( 'captionwright_not_vtt', __( 'Captions must be in WebVTT format and start with "WEBVTT".', 'captionwright' ), array( 'status' => 400 ) );
	}
	if ( ! parse_vtt( $vtt ) ) {
		return new \WP_Error( 'captionwright_empty', __( 'The caption file has no cues.', 'captionwright' ), array( 'status' => 400 ) );
	}
	return trim( $vtt ) . "\n";
}

/**
 * Save a track for an attachment.
 *
 * @param int    $id    Attachment ID.
 * @param string $lang  Language code.
 * @param string $vtt   WebVTT text (already cleaned).
 * @param string $label Human label shown in the player.
 * @return true|\WP_Error
 */
function save_track( $id, $lang, $vtt, $label ) {
	$fs = fs();
	$st = storage();
	if ( ! $fs ) {
		return new \WP_Error( 'captionwright_fs', __( 'Could not access the uploads folder.', 'captionwright' ), array( 'status' => 500 ) );
	}
	if ( ! $fs->is_dir( $st['dir'] ) && ! wp_mkdir_p( $st['dir'] ) ) {
		return new \WP_Error( 'captionwright_mkdir', __( 'Could not create the captions folder in uploads.', 'captionwright' ), array( 'status' => 500 ) );
	}
	// Some browsers want text/vtt; many hosts serve unknown types as octet-stream.
	if ( ! $fs->exists( $st['dir'] . '/.htaccess' ) ) {
		$fs->put_contents( $st['dir'] . '/.htaccess', "AddType text/vtt .vtt\nAddCharset utf-8 .vtt\n", FS_CHMOD_FILE );
	}
	$file = $st['dir'] . '/' . (int) $id . '-' . $lang . '.vtt';
	if ( ! $fs->put_contents( $file, $vtt, FS_CHMOD_FILE ) ) {
		return new \WP_Error( 'captionwright_write', __( 'Could not write the caption file.', 'captionwright' ), array( 'status' => 500 ) );
	}
	$meta = get_post_meta( (int) $id, META, true );
	$meta = is_array( $meta ) ? $meta : array();

	$meta[ $lang ] = array(
		'label'   => $label,
		'updated' => time(),
		'cues'    => count( parse_vtt( $vtt ) ),
	);
	update_post_meta( (int) $id, META, $meta );
	return true;
}

/**
 * Delete one track (or all tracks when $lang is null).
 *
 * @param int         $id   Attachment ID.
 * @param string|null $lang Language code.
 */
function delete_track( $id, $lang = null ) {
	$fs   = fs();
	$st   = storage();
	$meta = get_post_meta( (int) $id, META, true );
	$meta = is_array( $meta ) ? $meta : array();
	$gone = null === $lang ? array_keys( $meta ) : array( $lang );
	foreach ( $gone as $l ) {
		if ( $fs && valid_lang( $l ) ) {
			$fs->delete( $st['dir'] . '/' . (int) $id . '-' . $l . '.vtt' );
		}
		unset( $meta[ $l ] );
	}
	if ( $meta ) {
		update_post_meta( (int) $id, META, $meta );
	} else {
		delete_post_meta( (int) $id, META );
	}
}
add_action(
	'delete_attachment',
	function ( $id ) {
		delete_track( $id );
	}
);

/**
 * Read a saved track's WebVTT text.
 *
 * @param int    $id   Attachment ID.
 * @param string $lang Language code.
 * @return string
 */
function read_track( $id, $lang ) {
	$fs = fs();
	if ( ! $fs || ! valid_lang( $lang ) ) {
		return '';
	}
	$file = storage()['dir'] . '/' . (int) $id . '-' . $lang . '.vtt';
	return $fs->exists( $file ) ? (string) $fs->get_contents( $file ) : '';
}

/**
 * Turn "01:02:03.456" or "02:03.456" into seconds.
 *
 * @param string $t Timestamp.
 * @return float
 */
function vtt_seconds( $t ) {
	$parts = array_reverse( explode( ':', trim( str_replace( ',', '.', $t ) ) ) );
	$secs  = 0.0;
	foreach ( $parts as $i => $p ) {
		$secs += (float) $p * pow( 60, $i );
	}
	return $secs;
}

/**
 * Parse WebVTT into cues.
 *
 * @param string $vtt WebVTT text.
 * @return array<int, array{start:float,end:float,text:string}>
 */
function parse_vtt( $vtt ) {
	$cues   = array();
	$blocks = preg_split( "/\n\s*\n/", str_replace( array( "\r\n", "\r" ), "\n", (string) $vtt ) );
	foreach ( $blocks as $block ) {
		$lines = explode( "\n", trim( $block ) );
		foreach ( $lines as $i => $line ) {
			if ( ! preg_match( '/^\s*([\d:.,]+)\s+-->\s+([\d:.,]+)/', $line, $m ) ) {
				continue;
			}
			$text = trim( wp_strip_all_tags( implode( ' ', array_slice( $lines, $i + 1 ) ) ) );
			if ( '' !== $text ) {
				$cues[] = array(
					'start' => vtt_seconds( $m[1] ),
					'end'   => vtt_seconds( $m[2] ),
					'text'  => $text,
				);
			}
			break;
		}
	}
	return $cues;
}