0ad/source/lib/file/vfs/vfs_lookup.cpp

/* Copyright (C) 2026 Wildfire Games.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * look up directories/files by traversing path components.
 */

#include "precompiled.h"

#include "vfs_lookup.h"

#include "lib/debug.h"
#include "lib/file/common/real_directory.h"
#include "lib/file/file.h"
#include "lib/file/file_system.h"
#include "lib/file/vfs/vfs.h"	// error codes
#include "lib/file/vfs/vfs_populate.h"
#include "lib/file/vfs/vfs_tree.h"
#include "lib/os_path.h"
#include "lib/path.h"
#include "lib/posix/posix_filesystem.h"

#include <filesystem>
#include <string>
#include <system_error>

static Status CreateDirectory(const OsPath& dirpath)
{
	const std::filesystem::path path{dirpath.string()};
	std::error_code ec{};

    if (std::filesystem::is_directory(path))
		return INFO::OK;

	std::filesystem::create_directory(path, ec);
	if (ec)
		return StatusFromSystemError(ec);

	// 0700 as prescribed by XDG basedir
	std::filesystem::permissions(path, std::filesystem::perms::owner_all, ec);
	return StatusFromSystemError(ec);
}


Status vfs_Lookup(const VfsPath& pathname, VfsDirectory* startDirectory, VfsDirectory*& directory, VfsFile** pfile, size_t flags)
{
	// extract and validate flags (ensure no unknown bits are set)
	const bool addMissingDirectories    = (flags & VFS_LOOKUP_ADD) != 0;
	const bool skipPopulate = (flags & VFS_LOOKUP_SKIP_POPULATE) != 0;
	const bool realPath = (flags & VFS_LOOKUP_REAL_PATH) != 0;
	ENSURE((flags & ~(VFS_LOOKUP_ADD|VFS_LOOKUP_SKIP_POPULATE|VFS_LOOKUP_REAL_PATH)) == 0);

	directory = startDirectory;
	if (pfile)
		*pfile = 0;

	if (!skipPopulate)
		RETURN_STATUS_IF_ERR(vfs_Populate(directory));

	// early-out for pathname == "" when mounting into VFS root
	if (pathname.empty())	// (prevent iterator error in loop end condition)
	{
		// Preserve a guarantee that if pfile then we either return an error or set *pfile,
		// and if looking for a real path ensure an associated directory.
		if (pfile || (realPath && !directory->AssociatedDirectory()))
			return ERR::VFS_FILE_NOT_FOUND;
		else
			return INFO::OK;
	}

	// for each directory component:
	size_t pos = 0;	// (needed outside of loop)
	for(;;)
	{
		const size_t nextSlash = pathname.string().find_first_of('/', pos);
		if (nextSlash == VfsPath::String::npos)
			break;
		const VfsPath subdirectoryName = pathname.string().substr(pos, nextSlash-pos);
		pos = nextSlash+1;

		VfsDirectory* subdirectory = directory->GetSubdirectory(subdirectoryName);
		if (!subdirectory)
		{
			if (addMissingDirectories)
				subdirectory = directory->AddSubdirectory(subdirectoryName);
			else
				return ERR::VFS_DIR_NOT_FOUND;	// NOWARN
		}
		// When looking for a real path, we need to keep the path of the highest priority subdirectory.
		// If the current directory has an associated directory, and the subdir does not / is lower priority,
		// we will overwrite it.
		PRealDirectory realDir = directory->AssociatedDirectory();
		if (realPath && realDir &&
		    (!subdirectory->AssociatedDirectory() ||
		    realDir->Priority() > subdirectory->AssociatedDirectory()->Priority()))
		{
			OsPath currentPath = directory->AssociatedDirectory()->Path();
			currentPath = currentPath / subdirectoryName / "";

			// Only actually create the directory if we're in LOOKUP_ADD mode.
			if (addMissingDirectories)
				RETURN_STATUS_IF_ERR(CreateDirectory(currentPath));
			else if (!DirectoryExists(currentPath))
				return ERR::VFS_DIR_NOT_FOUND;

			// Propagate priority and flags to the subdirectory.
			// If it already existed, it will be replaced & the memory freed.
			PRealDirectory realDirectory(new RealDirectory(currentPath,
				realDir ? realDir->Priority() : 0,
				realDir ? realDir->Flags() : 0)
			);
			RETURN_STATUS_IF_ERR(vfs_Attach(subdirectory, realDirectory));
		}

		if (!skipPopulate)
			RETURN_STATUS_IF_ERR(vfs_Populate(subdirectory));

		directory = subdirectory;
	}

	if (realPath && !directory->AssociatedDirectory())
		return ERR::VFS_DIR_NOT_FOUND;

	if (pfile)
	{
		ENSURE(!pathname.IsDirectory());
		const VfsPath filename = pathname.string().substr(pos);
		*pfile = directory->GetFile(filename);
		if (!*pfile)
			return ERR::VFS_FILE_NOT_FOUND;	// NOWARN
	}

	return INFO::OK;
}