<?php

declare(strict_types=1);

/**
 * SPDX-FileCopyrightText: Sebastian Krupinski <krupinski01@gmail.com>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

namespace KTXM\ProviderImap\Stores;

use DI\Attribute\Inject;
use FilesystemIterator;
use InvalidArgumentException;
use JsonException;
use RecursiveDirectoryIterator;
use RecursiveIteratorIterator;
use RuntimeException;

/**
 * IMAP Message Content Store
 *
 * Holds the immutable content of cached messages (message.json) on the filesystem:
 *
 *   {rootDir}/storage/{tid}/provider_imap/{sid}/{sha1(mailbox)}/{uidValidity}/{uid}/message.json
 *
 * Mailbox names are hashed because they contain delimiters and modified UTF-7.
 * Files are written atomically (temporary file + rename).
 */
class MessageFileStore
{
    private const CONTENT_FILE = 'message.json';
    private const FOLDER_PERMISSIONS = 0750;
    private const FILE_PERMISSIONS = 0640;

    public function __construct(
        #[Inject('rootDir')] private readonly string $rootDir,
    ) {}

    /**
     * Write the content of a message, replacing any existing content.
     */
    public function write(string $tenantId, string $serviceId, string $mailbox, int $uidValidity, int $uid, array $content): void
    {
        $folder = $this->messagePath($tenantId, $serviceId, $mailbox, $uidValidity, $uid);
        if (!is_dir($folder) && !@mkdir($folder, self::FOLDER_PERMISSIONS, true) && !is_dir($folder)) {
            throw new RuntimeException("Failed to create message folder: {$folder}");
        }

        try {
            $json = json_encode($content, JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_INVALID_UTF8_SUBSTITUTE);
        } catch (JsonException $e) {
            throw new RuntimeException('Failed to encode message content: ' . $e->getMessage(), 0, $e);
        }

        $file = $folder . DIRECTORY_SEPARATOR . self::CONTENT_FILE;
        $temporary = $file . '.' . bin2hex(random_bytes(6)) . '.tmp';

        if (@file_put_contents($temporary, $json, LOCK_EX) !== strlen($json)) {
            @unlink($temporary);
            throw new RuntimeException("Failed to write message content: {$file}");
        }
        @chmod($temporary, self::FILE_PERMISSIONS);

        if (!@rename($temporary, $file)) {
            @unlink($temporary);
            throw new RuntimeException("Failed to replace message content: {$file}");
        }
    }

    /**
     * Read the content of a message.
     *
     * @return array|null null when the message is not cached or its content is unreadable
     */
    public function read(string $tenantId, string $serviceId, string $mailbox, int $uidValidity, int $uid): ?array
    {
        $file = $this->messagePath($tenantId, $serviceId, $mailbox, $uidValidity, $uid) . DIRECTORY_SEPARATOR . self::CONTENT_FILE;
        if (!is_file($file)) {
            return null;
        }

        $json = @file_get_contents($file);
        if ($json === false) {
            return null;
        }

        try {
            $content = json_decode($json, true, 512, JSON_THROW_ON_ERROR);
        } catch (JsonException) {
            return null;
        }

        return is_array($content) ? $content : null;
    }

    /**
     * Delete the cached files of messages.
     */
    public function delete(string $tenantId, string $serviceId, string $mailbox, int $uidValidity, int ...$uids): void
    {
        foreach ($uids as $uid) {
            $this->removeTree($this->messagePath($tenantId, $serviceId, $mailbox, $uidValidity, $uid));
        }
    }

    /**
     * Delete the cached files of a mailbox (all UIDVALIDITY generations).
     */
    public function deleteByMailbox(string $tenantId, string $serviceId, string $mailbox): void
    {
        $this->removeTree($this->mailboxPath($tenantId, $serviceId, $mailbox));
    }

    /**
     * Delete the cached files of a service.
     */
    public function deleteByService(string $tenantId, string $serviceId): void
    {
        $this->removeTree($this->servicePath($tenantId, $serviceId));
    }

    private function servicePath(string $tenantId, string $serviceId): string
    {
        return implode(DIRECTORY_SEPARATOR, [
            rtrim($this->rootDir, DIRECTORY_SEPARATOR),
            'storage',
            self::pathSegment($tenantId, 'tenant'),
            'provider_imap',
            self::pathSegment($serviceId, 'service'),
        ]);
    }

    private function mailboxPath(string $tenantId, string $serviceId, string $mailbox): string
    {
        return $this->servicePath($tenantId, $serviceId) . DIRECTORY_SEPARATOR . sha1($mailbox);
    }

    private function messagePath(string $tenantId, string $serviceId, string $mailbox, int $uidValidity, int $uid): string
    {
        if ($uidValidity < 0 || $uid <= 0) {
            throw new InvalidArgumentException('Invalid UIDVALIDITY or UID');
        }

        return $this->mailboxPath($tenantId, $serviceId, $mailbox)
            . DIRECTORY_SEPARATOR . $uidValidity
            . DIRECTORY_SEPARATOR . $uid;
    }

    /**
     * Guard identifiers used as path segments against traversal.
     */
    private static function pathSegment(string $value, string $label): string
    {
        if (preg_match('/^[A-Za-z0-9_-]+$/', $value) !== 1) {
            throw new InvalidArgumentException("Invalid {$label} identifier for cache path");
        }

        return $value;
    }

    private function removeTree(string $path): void
    {
        if (!file_exists($path)) {
            return;
        }

        if (!is_dir($path) || is_link($path)) {
            @unlink($path);
            return;
        }

        $items = new RecursiveIteratorIterator(
            new RecursiveDirectoryIterator($path, FilesystemIterator::SKIP_DOTS),
            RecursiveIteratorIterator::CHILD_FIRST,
        );
        foreach ($items as $item) {
            $item->isDir() && !$item->isLink() ? @rmdir($item->getPathname()) : @unlink($item->getPathname());
        }
        @rmdir($path);
    }
}