mijin2/source/mijin/virtual_filesystem/mapping.hpp

#pragma once

#if !defined(MIJIN_VIRTUAL_FILESYSTEM_MAPPING_HPP_INCLUDED)
#define MIJIN_VIRTUAL_FILESYSTEM_MAPPING_HPP_INCLUDED 1

#include <algorithm>
#include "./filesystem.hpp"
#include "../internal/common.hpp"

namespace mijin
{

//
// public defines
//

//
// public constants
//

//
// public types
//

template<typename TWrapped>
class MappingFileSystemAdapter : public FileSystemAdapter
{
private:
    TWrapped wrapped_;
    fs::path root_;
public:
    template<typename... TArgs>
    explicit MappingFileSystemAdapter(fs::path root, TArgs&&... args)
            : wrapped_(std::forward<TArgs>(args)...), root_(std::move(root)) {}
    MappingFileSystemAdapter(const MappingFileSystemAdapter&) = default;
    MappingFileSystemAdapter(MappingFileSystemAdapter&&) MIJIN_NOEXCEPT = default;

    MappingFileSystemAdapter& operator=(const MappingFileSystemAdapter&) = default;
    MappingFileSystemAdapter& operator=(MappingFileSystemAdapter&&) MIJIN_NOEXCEPT = default;

    fs::path getHomeFolder() override;
    std::vector<FileInfo> listFiles(const fs::path& folder) override;
    FileInfo getFileInfo(const fs::path& file) override;
    Optional<fs::path> getNativePath(const fs::path& file) override;
    StreamError open(const fs::path& path, FileOpenMode mode, std::unique_ptr<Stream>& outStream) override;
private:
    bool adjustPath(fs::path& path) const MIJIN_NOEXCEPT;
};

//
// public functions
//

template<typename TWrapped>
fs::path MappingFileSystemAdapter<TWrapped>::getHomeFolder()
{
    return "/";
}

template<typename TWrapped>
std::vector<FileInfo> MappingFileSystemAdapter<TWrapped>::listFiles(const fs::path& folder)
{
    fs::path adjusted = folder;
    if (!adjustPath(adjusted))
    {
        return {};
    }

    std::vector<FileInfo> result;
    result = wrapped_.listFiles(adjusted);
    for (FileInfo& fileInfo : result)
    {
        fileInfo.path = root_ / fileInfo.path;
    }
    return result;
}

template<typename TWrapped>
FileInfo MappingFileSystemAdapter<TWrapped>::getFileInfo(const fs::path& file)
{
    fs::path adjusted = file;
    if (!adjustPath(adjusted))
    {
        return {};
    }

    return wrapped_.getFileInfo(adjusted);
}

template<typename TWrapped>
Optional<fs::path> MappingFileSystemAdapter<TWrapped>::getNativePath(const fs::path& file)
{
    fs::path adjusted = file;
    if (!adjustPath(adjusted))
    {
        return {};
    }

    return wrapped_.getNativePath(adjusted);
}

template<typename TWrapped>
StreamError MappingFileSystemAdapter<TWrapped>::open(const fs::path& path, FileOpenMode mode, std::unique_ptr<Stream>& outStream)
{
    fs::path adjusted = path;
    if (!adjustPath(adjusted))
    {
        return {};
    }

    return wrapped_.open(adjusted, mode, outStream);
}

template<typename TWrapped>
bool MappingFileSystemAdapter<TWrapped>::adjustPath(fs::path& path) const MIJIN_NOEXCEPT
{
    if (!path.is_absolute())
    {
        return false;
    }

    // checks whether path starts with root
    auto [itRoot, itPath] = std::mismatch(root_.begin(), root_.end(), path.begin(), path.end());
    if (itRoot != root_.end())
    {
        return false;
    }

    std::error_code error;
    fs::path wrapped = fs::relative(path, root_, error);

    if (wrapped.empty() || error)
    {
        return false;
    }
    path = std::move(wrapped);
    return true;
}

namespace vfs_pipe
{
template<typename TBase>
struct MappingBuilder : Builder<MappingBuilder<TBase>, MappingFileSystemAdapter<typename TBase::adapter_t>>
{
    fs::path root;
    TBase base;

    std::unique_ptr<MappingFileSystemAdapter<typename TBase::adapter_t>> build()
    {
        return std::make_unique<MappingFileSystemAdapter<typename TBase::adapter_t>>(root, std::move(*base.build()));
    }
};

struct MappingOptions
{
    fs::path root;
};

[[nodiscard]]
inline MappingOptions map_to(fs::path root) noexcept
{
    return {.root = std::move(root) };
}

template<typename TBase>
[[nodiscard]]
MappingBuilder<TBase> operator|(TBase other, MappingOptions options) noexcept
{
    return {.root = std::move(options.root), .base = std::move(other) };
}
}
} // namespace mijin

#endif // !defined(MIJIN_VIRTUAL_FILESYSTEM_MAPPING_HPP_INCLUDED)