/*
    * Vfs.hpp
    * Virtual File System with numerical logical drive identifiers
    * Copyright (c) 2025 Daniel Hammer
*/

#pragma once
#include <cstdint>
#include <cstddef>

namespace Fs::Vfs {

    static constexpr int MaxDrives = 16;

    struct BackendFile {
        int driveNumber;
        int localHandle;
        uint32_t generation;
    };

    // Metadata for a single path, filled by FsDriver::Stat. Timestamps are UTC
    // unix seconds; a filesystem that does not record a given time leaves it 0.
    struct StatInfo {
        uint64_t size;    // file size in bytes
        int64_t  mtime;   // last data modification time
        int64_t  ctime;   // last inode (metadata) change time
        int64_t  atime;   // last access time
        uint32_t mode;    // ext2/POSIX i_mode bits (type + permissions)
        bool     isDir;   // true if the entry is a directory
    };

    struct FsDriver {
        int (*Open)(const char* path);
        int (*Read)(int handle, uint8_t* buffer, uint64_t offset, uint64_t size);
        uint64_t (*GetSize)(int handle);
        void (*Close)(int handle);
        int (*ReadDir)(const char* path, const char** outNames, int maxEntries);
        int (*Write)(int handle, const uint8_t* buffer, uint64_t offset, uint64_t size);
        int (*Create)(const char* path);
        int (*Delete)(const char* path);
        int (*Mkdir)(const char* path);
        int (*Rename)(const char* oldPath, const char* newPath);
        const char* (*GetLabel)();
        // Optional: paginated directory read returning entries [startIndex, startIndex+maxEntries).
        // Drivers that leave this null are read via ReadDir at startIndex 0 only.
        int (*ReadDirAt)(const char* path, const char** outNames, int maxEntries, int startIndex);
        // Optional: fill metadata for a path. Drivers that leave this null do
        // not support stat and VfsStat returns -1 for their paths.
        int (*Stat)(const char* path, StatInfo* out);
    };

    void Initialize();
    bool IsInitialized();
    int RegisterDrive(int driveNumber, FsDriver* driver);
    int UnregisterDrive(int driveNumber);
    bool IsDriveRegistered(int driveNumber);
    int FindLowestAvailableDrive(int firstDrive = 0);

    int OpenBackendFile(const char* path, BackendFile& outFile);
    int CreateBackendFile(const char* path, BackendFile& outFile);
    int ReadBackendFile(const BackendFile& file, uint8_t* buffer, uint64_t offset, uint64_t size);
    int WriteBackendFile(const BackendFile& file, const uint8_t* buffer, uint64_t offset, uint64_t size);
    uint64_t GetBackendFileSize(const BackendFile& file);
    bool BackendFileCanWrite(const BackendFile& file);
    void CloseBackendFile(BackendFile& file);

    int VfsDelete(const char* path);
    int VfsStat(const char* path, StatInfo& out);
    int VfsReadDir(const char* path, const char** outNames, int maxEntries);
    int VfsReadDirAt(const char* path, const char** outNames, int maxEntries, int startIndex);
    int VfsMkdir(const char* path);
    int VfsRename(const char* oldPath, const char* newPath);

    // Returns number of registered drives, fills outDrives[] with their indices
    int VfsDriveList(int* outDrives, int maxEntries);
    int VfsDriveLabel(int driveNumber, char* outLabel, int maxLen);

}