<?php
/**
 * Applies string translations on pages in another language, and collects the
 * strings that have none.
 *
 * Strings are collected only while an administrator browses the front end
 * (or runs "Scan site"), so visitors never cause database writes; and only
 * while the page renders (from template_redirect on), so post type labels and
 * other setup texts stay out of the list.
 */

declare( strict_types = 1 );

namespace AddBlack\Lang\Strings;

defined( 'ABSPATH' ) || exit;

use AddBlack\Lang\Hookable;
use AddBlack\Lang\Hooks;
use AddBlack\Lang\Routing\CurrentLanguage;

final class GettextFilter implements Hookable {

	/** Language whose translations apply ('' = none; null = not decided yet). */
	private ?string $lang = null;

	/** Recording strings in this request (null = not decided yet). */
	private ?bool $capture = null;

	/** @var array<string, array{0: string, 1: string, 2: string}> key => [ domain, context, text ]. */
	private array $found = array();

	/** Re-entrance guard: our own code may call gettext. */
	private bool $busy = false;

	public function __construct(
		private readonly CurrentLanguage $current,
		private readonly StringCatalog $catalog,
		private readonly StringRules $rules
	) {}

	public function register(): void {
		Hooks::filter( 'gettext', array( $this, 'gettext' ), 99, 3 );
		Hooks::filter( 'gettext_with_context', array( $this, 'gettext_with_context' ), 99, 4 );
		Hooks::action( 'init', array( $this, 'decide_capture' ), 1 );
		Hooks::action( 'shutdown', array( $this, 'flush' ) );
	}

	public function gettext( mixed $translation, mixed $text, mixed $domain ): mixed {
		return $this->filter( $translation, $text, '', (string) $domain );
	}

	public function gettext_with_context( mixed $translation, mixed $text, mixed $context, mixed $domain ): mixed {
		return $this->filter( $translation, $text, (string) $context, (string) $domain );
	}

	/** Language of this front-end request when it is not the default one, else ''. */
	public function active_lang(): string {
		if ( null !== $this->lang ) {
			return $this->lang;
		}
		if ( is_admin() || ! did_action( 'plugins_loaded' ) ) {
			return ''; // Too early: the URL is not known to be ours yet. Not cached.
		}
		$this->lang = $this->current->is_other_than_default() ? $this->current->get() : '';
		return $this->lang;
	}

	/** Only administrators' front-end requests record strings; filter blocklingo_strings_capture. */
	public function decide_capture(): void {
		$on            = '' !== $this->active_lang() && current_user_can( 'manage_options' );
		$this->capture = (bool) apply_filters( 'blocklingo_strings_capture', $on );
		if ( ! $this->capture ) {
			$this->found = array();
		}
	}

	/** Save the strings found in this request (new ones only). */
	public function flush(): void {
		if ( ! $this->capture || ! $this->found ) {
			return;
		}
		$this->catalog->add( array_values( $this->found ) );
		$this->found = array();
	}

	/** @return array<int, array{0: string, 1: string, 2: string}> Strings found and not saved yet. */
	public function found(): array {
		return array_values( $this->found );
	}

	/** Tests: forget per-request state. */
	public function reset(): void {
		$this->lang    = null;
		$this->capture = null;
		$this->found   = array();
		$this->rules->reset();
	}

	private function filter( mixed $translation, mixed $text, string $context, string $domain ): mixed {
		if ( $this->busy || ! is_string( $text ) || '' === $text ) {
			return $translation;
		}
		$this->busy = true;
		try {
			$lang = $this->active_lang();
			if ( '' === $lang ) {
				return $translation;
			}
			$key = StringCatalog::key( $domain, $context, $text );
			$map = $this->catalog->map( $lang );
			if ( isset( $map[ $key ] ) ) {
				return $map[ $key ];
			}
			if ( $this->capture && $translation === $text && did_action( 'template_redirect' ) && ! isset( $this->found[ $key ] ) && $this->rules->collectable( $text, $domain, $context ) ) {
				$this->found[ $key ] = array( $domain, $context, $text );
			}
			return $translation;
		} finally {
			$this->busy = false;
		}
	}
}