#pragma once

#if !defined(MIJIN_VIRTUAL_FILESYSTEM_FILESYSTEM_HPP_INCLUDED)
#define MIJIN_VIRTUAL_FILESYSTEM_FILESYSTEM_HPP_INCLUDED 1

#include <array>
#include <cmath>
#include <filesystem>
#include <sstream>
#include <string>
#include <vector>
#include "../container/optional.hpp"
#include "../io/stream.hpp"
#include "../internal/common.hpp"
#include "../util/hash.hpp"

namespace fs = std::filesystem;

namespace mijin
{

//
// public defines
//

//
// public constants
//

//
// public types
//

struct FileInfo
{
    fs::path path;
    std::size_t size = 0;
    bool exists : 1 = false;
    bool isFolder : 1 = false;
    bool isSymlink : 1 = false;
    bool isSpecial : 1 = false;
    bool isHidden : 1 = false;
};

// basically just a thin wrapper around adapter + path, for utility
class PathReference
{
private:
    class FileSystemAdapter* adapter_ = nullptr;
    fs::path path_ = {};
public:
    PathReference() = default;
    PathReference(const PathReference&) = default;
    PathReference(PathReference&&) = default;
    PathReference(class FileSystemAdapter* adapter, fs::path path) MIJIN_NOEXCEPT : adapter_(adapter), path_(std::move(path)) {}

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

    auto operator<=>(const PathReference& other) const MIJIN_NOEXCEPT = default;

    [[nodiscard]] bool empty() const MIJIN_NOEXCEPT { return adapter_ == nullptr; }
    [[nodiscard]] class FileSystemAdapter* getAdapter() const noexcept { return adapter_; }
    [[nodiscard]] const fs::path& getPath() const MIJIN_NOEXCEPT { return path_; }
    [[nodiscard]] inline FileInfo getInfo() const;
    [[nodiscard]] inline Optional<fs::path> getNativePath() const;
    [[nodiscard]] inline StreamError open(FileOpenMode mode, std::unique_ptr<Stream>& outStream) const;

    [[nodiscard]]
    PathReference operator/(const fs::path& more) const
    {
        return PathReference(adapter_, path_ / more);
    }
};

class FileSystemAdapter
{
public:
    virtual ~FileSystemAdapter() = default;

    [[nodiscard]] virtual std::vector<fs::path> getRoots() = 0;
    [[nodiscard]] virtual fs::path getHomeFolder() = 0;
    [[nodiscard]] virtual std::vector<FileInfo> listFiles(const fs::path& folder) = 0;
    [[nodiscard]] virtual FileInfo getFileInfo(const fs::path& file) = 0;
    [[nodiscard]] virtual Optional<fs::path> getNativePath(const fs::path& /* file */) { return NULL_OPTIONAL; }
    [[nodiscard]] virtual StreamError open(const fs::path& path, FileOpenMode mode, std::unique_ptr<Stream>& outStream) = 0;

    [[nodiscard]] PathReference getPath(fs::path path) MIJIN_NOEXCEPT { return PathReference(this, std::move(path)); }
};

class OSFileSystemAdapter : public FileSystemAdapter
{
public:
    std::vector<fs::path> getRoots() override;
    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;

    static OSFileSystemAdapter& getInstance();
};

//
// public functions
//

inline FileInfo PathReference::getInfo() const
{
    return adapter_->getFileInfo(path_);
}

Optional<fs::path> PathReference::getNativePath() const
{
    return adapter_->getNativePath(path_);
}

inline StreamError PathReference::open(FileOpenMode mode, std::unique_ptr<Stream>& outStream) const
{
    return adapter_->open(path_, mode, outStream);
}

inline std::string formatFileType(const FileInfo& info)
{
    if (info.isFolder) {
        return "Folder";
    }
    if (info.isSpecial) {
        return "Special";
    }
    return "File";
}

inline std::string formatFileSize(std::size_t sizeInBytes)
{
    static constexpr std::array suffixes = {"bytes", "KiB", "MiB", "GiB", "TiB"}; // enough?

    if (sizeInBytes == 0) {
        return "0 bytes";
    }
    const std::size_t pos = std::min(static_cast<std::size_t>(std::ceil(std::log2(sizeInBytes))) / 10, suffixes.size() - 1);
    std::stringstream oss;
    oss << std::setprecision(2) << std::fixed;
    if (pos == 0) {
        oss << sizeInBytes << " bytes";
    }
    else
    {
        const float converted = static_cast<float>(sizeInBytes) / std::pow(2.f, 10.f * static_cast<float>(pos));
        oss << converted << " " << suffixes[pos];
    }
    return oss.str();
}

} // namespace mijin

template<>
struct std::hash<mijin::PathReference>
{
    std::size_t operator()(const mijin::PathReference& pathRef) const MIJIN_NOEXCEPT
    {
        std::size_t hash = 0;
        mijin::hashCombine(hash, pathRef.getAdapter());
        mijin::hashCombine(hash, pathRef.getPath());
        return hash;
    }
};

#endif // !defined(MIJIN_VIRTUAL_FILESYSTEM_FILESYSTEM_HPP_INCLUDED)