<?php

declare(strict_types=1);

/**
 * SPDX-FileCopyrightText: 2026 Lukas Schaefer
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

namespace OCA\Shortcuts\Service;

use OCA\Shortcuts\AppInfo\Application;
use OCA\Shortcuts\Exception\ConflictException;
use OCA\Shortcuts\Exception\ForbiddenException;
use OCA\Shortcuts\Exception\InvalidPathException;
use OCA\Shortcuts\Exception\NotFoundException;
use OCP\Constants;
use OCP\Files\File;
use OCP\Files\Folder;
use OCP\Files\IRootFolder;
use OCP\Files\Node;
use OCP\Files\NotFoundException as FilesNotFoundException;
use OCP\Files\NotPermittedException as FilesNotPermittedException;
use OCP\IUser;

class ShortcutService {
	/** @psalm-suppress PossiblyUnusedMethod */
	public function __construct(
		private IRootFolder $rootFolder,
	) {
	}

	/**
	 * @return array{fileId: int, name: string, path: string, targetFileId: int, targetType: 'file'|'folder'}
	 *
	 * @throws ConflictException
	 * @throws ForbiddenException
	 * @throws InvalidPathException
	 * @throws NotFoundException
	 */
	public function create(IUser $user, int $targetFileId, string $destinationPath, ?string $shortcutName = null): array {
		$userFolder = $this->rootFolder->getUserFolder($user->getUID());
		$target = $this->resolveAccessibleNode($userFolder, $targetFileId);
		$target = $this->canonicalizeTarget($userFolder, $target);

		$destinationFolder = $this->resolveDestinationFolder($userFolder, $destinationPath);
		if (($destinationFolder->getPermissions() & Constants::PERMISSION_CREATE) !== Constants::PERMISSION_CREATE) {
			throw new ForbiddenException('No create permission on destination folder');
		}

		if ($shortcutName === null) {
			$shortcutName = $target->getName() . '.' . Application::SHORTCUT_EXTENSION;
		}
		$this->assertValidName($shortcutName);
		$this->assertNoCollision($destinationFolder, $shortcutName);

		try {
			$file = $destinationFolder->newFile($shortcutName, (string)$target->getId());
		} catch (FilesNotPermittedException $e) {
			throw new ForbiddenException('Cannot create shortcut file in destination folder', 0, $e);
		}

		$relativePath = $this->getRelativePath($userFolder, $file);
		return [
			'fileId' => $file->getId(),
			'name' => $file->getName(),
			'path' => $relativePath,
			'targetFileId' => $target->getId(),
			'targetType' => $target instanceof Folder ? 'folder' : 'file',
		];
	}

	/**
	 * Resolve a shortcut stub file to its target.
	 *
	 * @return array{targetFileId: int, targetType: 'file'|'folder', name: string, path: string, dirname: string}
	 *
	 * @throws ForbiddenException
	 * @throws InvalidPathException
	 * @throws NotFoundException
	 */
	public function resolve(IUser $user, int $shortcutFileId): array {
		$userFolder = $this->rootFolder->getUserFolder($user->getUID());
		$shortcut = $this->resolveAccessibleNode($userFolder, $shortcutFileId);
		if (!($shortcut instanceof File)) {
			throw new InvalidPathException('Shortcut must be a file');
		}
		if (!$this->isShortcutFile($shortcut)) {
			throw new InvalidPathException('Not a shortcut file');
		}

		$targetId = $this->parseTargetId($shortcut->getContent());
		$target = $this->resolveAccessibleNode($userFolder, $targetId);
		// Follow one level if the target is itself a shortcut.
		$target = $this->canonicalizeTarget($userFolder, $target);

		$relativePath = $this->getRelativePath($userFolder, $target);
		$dirname = $this->getRelativePath($userFolder, $target->getParent());

		return [
			'targetFileId' => $target->getId(),
			'targetType' => $target instanceof Folder ? 'folder' : 'file',
			'name' => $target->getName(),
			'path' => $relativePath,
			'dirname' => $dirname === '' ? '/' : $dirname,
		];
	}

	/**
	 * Checks if a node is a shortcut file.
	 */
	public function isShortcutFile(Node $node): bool {
		if (!($node instanceof File)) {
			return false;
		}
		return $node->getMimeType() === Application::SHORTCUT_MIME;
	}

	/**
	 * @throws ForbiddenException
	 * @throws NotFoundException
	 */
	private function resolveAccessibleNode(Folder $userFolder, int $fileId): Node {
		$node = $userFolder->getFirstNodeById($fileId);
		if ($node === null) {
			throw new NotFoundException('File not found');
		}
		return $node;
	}

	/**
	 * @throws ForbiddenException
	 * @throws InvalidPathException
	 * @throws NotFoundException
	 */
	private function canonicalizeTarget(Folder $userFolder, Node $node): Node {
		if (!$this->isShortcutFile($node) || !($node instanceof File)) {
			return $node;
		}
		$targetId = $this->parseTargetId($node->getContent());
		$target = $this->resolveAccessibleNode($userFolder, $targetId);
		if ($this->isShortcutFile($target)) {
			throw new InvalidPathException('Nested shortcuts are not supported beyond one level');
		}
		return $target;
	}

	/**
	 * @throws InvalidPathException
	 */
	private function parseTargetId(string $content): int {
		$content = trim($content);
		if ($content === '' || strlen($content) > 100 || !ctype_digit($content)) {
			throw new InvalidPathException('Invalid shortcut contents');
		}
		return (int)$content;
	}

	/**
	 * @throws InvalidPathException
	 * @throws NotFoundException
	 */
	private function resolveDestinationFolder(Folder $userFolder, string $path): Folder {
		try {
			$node = $userFolder->get($path);
		} catch (FilesNotFoundException|FilesNotPermittedException $e) {
			throw new NotFoundException('Destination folder not found', 0, $e);
		}
		if (!($node instanceof Folder)) {
			throw new InvalidPathException('Destination is not a folder');
		}
		return $node;
	}

	/**
	 * Ensures that the name is a valid shortcut name.
	 *
	 * @throws InvalidPathException
	 */
	private function assertValidName(string $name): void {
		$ext = '.' . Application::SHORTCUT_EXTENSION;
		if ($name === '' || $name === '.' || $name === '..' || str_contains($name, '/')) {
			throw new InvalidPathException('Invalid shortcut name');
		}
		if (!str_ends_with(strtolower($name), $ext)) {
			throw new InvalidPathException('Shortcut name must end with ' . $ext);
		}
		$base = substr($name, 0, -strlen($ext));
		if ($base === '' || $base === '.' || $base === '..') {
			throw new InvalidPathException('Invalid shortcut name');
		}
	}

	/**
	 * Ensures that the file doesn't already exist in the destination folder.
	 *
	 * @throws ConflictException
	 */
	private function assertNoCollision(Folder $destinationFolder, string $name): void {
		if ($destinationFolder->nodeExists($name)) {
			throw new ConflictException('A file with this name already exists');
		}
	}

	/**
	 * Turns /alice/files/Documents/foo.txt into /Documents/foo.txt.
	 */
	private function getRelativePath(Folder $userFolder, Node $node): string {
		$path = $userFolder->getRelativePath($node->getPath());
		if ($path === null || $path === '') {
			return '/';
		}
		return $path;
	}
}