/* ext2.h - Read-only ext2 filesystem driver for Pactor64 */
#ifndef _EXT2_H
#define _EXT2_H

#include "pactor64.h"

/* ext2 magic number */
#define EXT2_SUPER_MAGIC 0xEF53

/* ext2 superblock (at byte offset 1024 from start of partition) */
typedef struct {
    uint32_t s_inodes_count;
    uint32_t s_blocks_count;
    uint32_t s_r_blocks_count;
    uint32_t s_free_blocks_count;
    uint32_t s_free_inodes_count;
    uint32_t s_first_data_block;
    uint32_t s_log_block_size;
    uint32_t s_log_frag_size;
    uint32_t s_blocks_per_group;
    uint32_t s_frags_per_group;
    uint32_t s_inodes_per_group;
    uint32_t s_mtime;
    uint32_t s_wtime;
    uint16_t s_mnt_count;
    uint16_t s_max_mnt_count;
    uint16_t s_magic;
    uint16_t s_state;
    uint16_t s_errors;
    uint16_t s_minor_rev_level;
    uint32_t s_lastcheck;
    uint32_t s_checkinterval;
    uint32_t s_creator_os;
    uint32_t s_rev_level;
    uint16_t s_def_resuid;
    uint16_t s_def_resgid;
    /* Extended fields (rev >= 1) */
    uint32_t s_first_ino;
    uint16_t s_inode_size;
    uint16_t s_block_group_nr;
    uint32_t s_feature_compat;
    uint32_t s_feature_incompat;
    uint32_t s_feature_ro_compat;
    uint8_t  s_uuid[16];
    char     s_volume_name[16];
    char     s_last_mounted[64];
    uint32_t s_algo_usage_bitmap;
} __attribute__((packed)) ext2_superblock_t;

/* Block group descriptor */
typedef struct {
    uint32_t bg_block_bitmap;
    uint32_t bg_inode_bitmap;
    uint32_t bg_inode_table;
    uint16_t bg_free_blocks_count;
    uint16_t bg_free_inodes_count;
    uint16_t bg_used_dirs_count;
    uint16_t bg_pad;
    uint8_t  bg_reserved[12];
} __attribute__((packed)) ext2_bgd_t;

/* Inode */
typedef struct {
    uint16_t i_mode;
    uint16_t i_uid;
    uint32_t i_size;
    uint32_t i_atime;
    uint32_t i_ctime;
    uint32_t i_mtime;
    uint32_t i_dtime;
    uint16_t i_gid;
    uint16_t i_links_count;
    uint32_t i_blocks;
    uint32_t i_flags;
    uint32_t i_osd1;
    uint32_t i_block[15]; /* 0-11 direct, 12 indirect, 13 double, 14 triple */
    uint32_t i_generation;
    uint32_t i_file_acl;
    uint32_t i_dir_acl;
    uint32_t i_faddr;
    uint8_t  i_osd2[12];
} __attribute__((packed)) ext2_inode_t;

/* Directory entry */
typedef struct {
    uint32_t inode;
    uint16_t rec_len;
    uint8_t  name_len;
    uint8_t  file_type;
    char     name[];
} __attribute__((packed)) ext2_dirent_t;

/* Directory entry file types */
#define EXT2_FT_UNKNOWN  0
#define EXT2_FT_REG_FILE 1
#define EXT2_FT_DIR      2
#define EXT2_FT_CHRDEV   3
#define EXT2_FT_BLKDEV   4
#define EXT2_FT_FIFO     5
#define EXT2_FT_SOCK     6
#define EXT2_FT_SYMLINK  7

/* Inode mode bits */
#define EXT2_S_IFREG  0x8000
#define EXT2_S_IFDIR  0x4000
#define EXT2_S_IFLNK  0xA000

/* Root inode */
#define EXT2_ROOT_INO 2

/* Maximum path component length */
#define EXT2_NAME_LEN 255

/* Block device read function type */
typedef int (*block_read_fn)(uint64_t lba, uint32_t count, void *buf);

/* ext2 filesystem context */
typedef struct {
    block_read_fn   read_block;
    ext2_superblock_t sb;
    ext2_bgd_t     *bgdt;       /* Block group descriptor table */
    uint32_t        block_size;
    uint32_t        inodes_per_group;
    uint32_t        inode_size;
    uint32_t        groups_count;
} ext2_fs_t;

/* File handle */
typedef struct {
    ext2_fs_t      *fs;
    ext2_inode_t    inode;
    uint32_t        inode_num;
    uint32_t        size;
    uint32_t        position;
} ext2_file_t;

/* Directory entry callback */
typedef void (*ext2_dirent_cb)(const char *name, uint8_t name_len,
                               uint32_t inode, uint8_t file_type, void *ctx);

/* Initialize ext2 filesystem from block device */
int ext2_init(ext2_fs_t *fs, block_read_fn read_fn);

/* Open a file by path (returns 0 on success) */
int ext2_open(ext2_fs_t *fs, const char *path, ext2_file_t *file);

/* Read from an open file */
int ext2_read(ext2_file_t *file, void *buf, uint32_t size);

/* Close an open file */
void ext2_close(ext2_file_t *file);

/* Read directory entries (callback-based) */
int ext2_readdir(ext2_fs_t *fs, uint32_t dir_inode, ext2_dirent_cb cb, void *ctx);

/* Read a raw inode by number */
int ext2_read_inode(ext2_fs_t *fs, uint32_t inode_num, ext2_inode_t *inode);

/* Mount ext2 from ATA disk at given partition LBA offset */
int ext2_mount(ext2_fs_t *fs, uint32_t part_lba);

#endif /* _EXT2_H */