gui_file_system.h

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#pragma once
 
// File systems a file view browses and changes, behind one interface: a folder's entries,
// moving, renaming and copying in from the disk. A view relists when Generation() changes.
//
// Paths are relative to the file system's root, with '/' between names; "" is the root.
 
#include <cstdint>
#include <filesystem>
#include <memory>
#include <string>
#include <string_view>
#include <vector>
 
namespace tachyon
{

    struct FileEntry
    {
        std::string name;
        bool        isFolder = false;
        uint64_t    size     = 0;   
        std::filesystem::path           disk;
        std::filesystem::file_time_type modified {};   
    };

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

        virtual std::vector<FileEntry> List(std::string_view path) = 0;
        virtual bool Move(std::string_view path, std::string_view toFolder, std::string& error) = 0;
        virtual bool Rename(std::string_view path, std::string_view newName, std::string& error) = 0;
        virtual bool Import(const std::filesystem::path& source, std::string_view toFolder, std::string& error) = 0;
        virtual uint64_t Generation() const = 0;
    };

    std::string JoinPath(std::string_view folder, std::string_view name);
    std::string_view ParentPath(std::string_view path);
    std::string_view FileName(std::string_view path);

    class MemoryFileSystem final : public IFileSystem
    {
    public:
        MemoryFileSystem();
        explicit MemoryFileSystem(std::filesystem::path diskRoot);
        ~MemoryFileSystem() override;

        bool AddFolder(std::string_view path);
        bool AddFile(std::string_view path, uint64_t size = 0);
 
        std::vector<FileEntry> List(std::string_view path) override;
        bool Move(std::string_view path, std::string_view toFolder, std::string& error) override;
        bool Rename(std::string_view path, std::string_view newName, std::string& error) override;
        bool Import(const std::filesystem::path& source, std::string_view toFolder, std::string& error) override;
        uint64_t Generation() const override { return m_generation; }
 
    private:
        struct Node;
        Node* Find(std::string_view path);
        Node* AddPath(std::string_view path, bool isFolder);
        void  Load(Node& folder);
 
        std::unique_ptr<Node> m_root;
        uint64_t              m_generation = 0;
    };

}