#pragma once
// io_file.h - VFS layer
// Filesystem drivers register an IO_FILESYSTEM vtable via IoRegisterFilesystem.
// Kernel and user code open files through IoOpenFile.
#include <stdint.h>
#include <stddef.h>
#include <ke_status.h>
#include <ob_object.h>

// ---------------------------------------------------------------------------
// Filesystem driver vtable - filled in by fat32.sys (or any future fs driver)
// ---------------------------------------------------------------------------
typedef struct IO_FILESYSTEM {
    // Open a file by absolute path (e.g. "apps\\shell.exe").
    // Returns an opaque per-file driver cookie in* fileCtx.
    KSTATUS (*Open)(struct IO_FILESYSTEM* fs,
                    const char* path, void **fileCtx);

    // Read up to 'size' bytes at 'offset' into 'buf'.
    // Sets* bytesRead to actual bytes copied.
    KSTATUS (*Read)(struct IO_FILESYSTEM* fs, void* fileCtx,
                    uint64_t offset, void* buf,
                    size_t size, size_t* bytesRead);

    // Return the file size in bytes.
    uint64_t (*GetSize)(struct IO_FILESYSTEM* fs, void* fileCtx);

    // Release any resources the driver allocated for fileCtx.
    void (*Close)(struct IO_FILESYSTEM* fs, void* fileCtx);

    // Optional driver-private data.
    void* DriverCtx;
} IO_FILESYSTEM;

// ---------------------------------------------------------------------------
// FILE_OBJECT - the kernel object returned to callers
// ---------------------------------------------------------------------------
typedef struct FILE_OBJECT {
    OBJECT        Header;          // must be first
    IO_FILESYSTEM* Fs;
    void* FileCtx;        // driver cookie
    uint64_t       Size;
    uint64_t       Offset;         // current position for sequential reads
} FILE_OBJECT;

typedef struct IO_VOLUME_PARAMS {
    uint8_t  DiskIndex;      // which disk in HAL_DISK table
    uint64_t PartitionLba;   // starting LBA of this partition
    uint64_t PartitionSize;  // sectors, for bounds checking
} IO_VOLUME_PARAMS;

// ---------------------------------------------------------------------------
// Registration - called by fat32.sys from DriverEntry
// ---------------------------------------------------------------------------
// driveIndex matches the index passed to IoRegisterDisk.
KSTATUS IoRegisterFilesystem(uint8_t driveIndex, IO_FILESYSTEM* fs, const IO_VOLUME_PARAMS *vol);

// ---------------------------------------------------------------------------
// Kernel-side API
// ---------------------------------------------------------------------------
KSTATUS  IoOpenFile(const char* path, FILE_OBJECT **out);
KSTATUS  IoReadFile(FILE_OBJECT* file, void* buf,
                    size_t size, size_t* bytesRead);
KSTATUS  IoSeekFile(FILE_OBJECT* file, uint64_t offset);
uint64_t IoGetFileSize(FILE_OBJECT* file);
void     IoCloseFile(FILE_OBJECT* file);