// Copyright 2024-2025, Amlal El Mahrouss (amlal@nekernel.org)
// Licensed under the Apache License, Version 2.0 (see LICENSE file)
// Official repository: https://github.com/ne-foss-org/nekernel

#ifndef FSKIT_EXT2_H
#define FSKIT_EXT2_H

#include <CompilerKit/CompilerKit.h>
#include <KernelKit/DriveMgr.h>
#include <NeKit/Config.h>
#include <NeKit/KString.h>
#include <hint/CompilerHint.h>

/// @file Ext2.h
/// @brief EXT2 filesystem structures, constants, and base wrappers.

/// EXT2 Constants
#define kExt2FSMagic (0xEF53)
#define kExt2FSMaxFileNameLen (255U)
#define kExt2FSSuperblockOffset (1024)
#define kExt2FSRootInodeNumber (2)
#define kExt2FSInodeSize (128U)
#define kExt2FSBlockSizeBase (1024U)

#define kExt2FSRev0 (0)
#define kExt2FSRev1 (1)

/// EXT2 file types
enum {
  kExt2FileTypeUnknown      = 0,
  kExt2FileTypeRegular      = 1,
  kExt2FileTypeDirectory    = 2,
  kExt2FileTypeCharDevice   = 3,
  kExt2FileTypeBlockDevice  = 4,
  kExt2FileTypeFIFO         = 5,
  kExt2FileTypeSocket       = 6,
  kExt2FileTypeSymbolicLink = 7
};

typedef struct EXT2_GROUP_DESCRIPTOR final {
  UInt32 fBlockBitmap;
  UInt32 fInodeBitmap;
  UInt32 fInodeTable;
  UInt16 fFreeBlocksCount;
  UInt16 fFreeInodesCount;
  UInt16 fBgUsedDirsCount;
  UInt16 fBgPad;
  UInt32 fBgReserved[3];
} EXT2_GROUP_DESCRIPTOR;

struct PACKED EXT2_SUPER_BLOCK final {
  Kernel::UInt32 fInodeCount;
  Kernel::UInt32 fBlockCount;
  Kernel::UInt32 fReservedBlockCount;
  Kernel::UInt32 fFreeBlockCount;
  Kernel::UInt32 fFreeInodeCount;
  Kernel::UInt32 fFirstDataBlock;
  Kernel::UInt32 fLogBlockSize;
  Kernel::UInt32 fLogFragmentSize;
  Kernel::UInt32 fBlocksPerGroup;
  Kernel::UInt32 fFragmentsPerGroup;
  Kernel::UInt32 fInodesPerGroup;
  Kernel::UInt32 fMountTime;
  Kernel::UInt32 fWriteTime;
  Kernel::UInt16 fMountCount;
  Kernel::UInt16 fMaxMountCount;
  Kernel::UInt16 fMagic;
  Kernel::UInt16 fState;
  Kernel::UInt16 fErrors;
  Kernel::UInt16 fMinorRevision;
  Kernel::UInt32 fLastCheck;
  Kernel::UInt32 fCheckInterval;
  Kernel::UInt32 fCreatorOS;
  Kernel::UInt32 fRevisionLevel;
  Kernel::UInt16 fDefaultUID;
  Kernel::UInt16 fDefaultGID;

  // EXT2_DYNAMIC_REV fields
  Kernel::UInt32 fFirstInode;
  Kernel::UInt16 fInodeSize;
  Kernel::UInt16 fBlockGroupNumber;
  Kernel::UInt32 fFeatureCompat;
  Kernel::UInt32 fFeatureIncompat;
  Kernel::UInt32 fFeatureROCompat;
  Kernel::UInt8  fUUID[16];
  Kernel::Char   fVolumeName[16];
  Kernel::Char   fLastMounted[64];
  Kernel::UInt32 fAlgoBitmap;

  Kernel::UInt8  fPreallocBlocks;
  Kernel::UInt8  fPreallocDirBlocks;
  Kernel::UInt16 fReservedGDTBlocks;

  Kernel::UInt8  fJournalUUID[16];
  Kernel::UInt32 fJournalInode;
  Kernel::UInt32 fJournalDevice;
  Kernel::UInt32 fLastOrphan;

  Kernel::UInt32 fHashSeed[4];
  Kernel::UInt8  fDefHashVersion;
  Kernel::UInt8  fReservedCharPad;
  Kernel::UInt16 fReservedWordPad;
  Kernel::UInt32 fDefaultMountOpts;
  Kernel::UInt32 fFirstMetaBlockGroup;

  Kernel::UInt8 fReserved[760];  // Padding to make 1024 bytes
};

struct PACKED EXT2_INODE final {
  Kernel::UInt16 fMode;
  Kernel::UInt16 fUID;
  Kernel::UInt32 fSize;
  Kernel::UInt32 fAccessTime;
  Kernel::UInt32 fCreateTime;
  Kernel::UInt32 fModifyTime;
  Kernel::UInt32 fDeleteTime;
  Kernel::UInt16 fGID;
  Kernel::UInt16 fLinksCount;
  Kernel::UInt32 fBlocks;
  Kernel::UInt32 fFlags;
  Kernel::UInt32 fOSD1;

  Kernel::UInt32 fBlock[15];  // direct 0-11, indirect 12, double 13, triple 14

  Kernel::UInt32 fGeneration;
  Kernel::UInt32 fFileACL;
  Kernel::UInt32 fDirACL;
  Kernel::UInt32 fFragmentAddr;

  Kernel::UInt8 fOSD2[12];
};

/// Directory entry
struct PACKED EXT2_DIR_ENTRY final {
  Kernel::UInt32 fInode;
  Kernel::UInt16 fRecordLength;
  Kernel::UInt8  fNameLength;
  Kernel::UInt8  fFileType;
  Kernel::Char   fName[kExt2FSMaxFileNameLen];
};

/// VFS usage
struct Ext2Node {
  Kernel::UInt32 inodeNumber;
  EXT2_INODE     inode;
  Kernel::UInt32 cursor{0};
};

#endif