// ext2 minidriver
// based on osdev wiki article: http://wiki.osdev.org/Ext2

#include <stdint.h>
#include <stdio.h>

typedef struct ext2_superblock_struct
{
    uint32_t inodes_count;
    uint32_t blocks_count;
    uint32_t blocks_reserved_count;
    uint32_t inodes_unalloc_count;
    uint32_t blocks_unalloc_count;
    uint32_t superblock_number;
    uint32_t block_size;
    uint32_t fragment_size;
    uint32_t blocks_per_group;
    uint32_t fragments_per_group;
    uint32_t inodes_per_group;
    uint8_t skip[12]; // maybe we will look at these fields later...
    uint16_t ext2_sig; // 0xef5
    uint16_t fs_state; 
    uint16_t error_handle; 
    uint16_t version_minor;
    uint8_t skip2[8]; // maybe we will look at these fields later...
    uint32_t os_id;
    uint32_t version_major;
    uint16_t uid_reserved;
    uint16_t gid_reserved;
}ext2_superblock;

typedef struct ext2_superblock_ext_struct
{
    uint32_t first_inode;
    uint16_t size_inode;
    uint16_t blockgroup;

    uint32_t features_opt;
    uint32_t features_req;
    uint32_t features_write;

    uint32_t blkid[4];
    char    vol_name[16];
    char    last_path[64];
    uint32_t compression;
    uint8_t prealloc_files;
    uint8_t prealloc_dirs;
    uint8_t unused[2];
    uint32_t journalid[4];
    uint32_t journal_inode;
    uint32_t journal_device;
    uint32_t orpan_head;

}ext2_superblock_ext;

typedef struct ext2_blockgroup_desc_struct
{
    uint32_t addr_block_bitmap;
    uint32_t addr_inode_bitmap;;
    uint32_t addr_inode_table;
    uint16_t unalloc_blocks_count;
    uint16_t unalloc_inodes_count;
    uint16_t dir_count;
    uint8_t unused[14];
}ext2_blockgroup_desc;

typedef struct ext2_dir_struct
{
    uint32_t inode;
    uint16_t size;
    uint8_t name_length_low;
    uint8_t name_length_high;
    // name follows
}ext2_dir;

typedef struct ext2_inode_struct
{
    uint16_t permissions;
    uint16_t user_id;
    uint32_t size_low;
    uint32_t skip[4];
    uint16_t group_id;
    uint16_t hardlink_count;
    uint32_t disk_sectors;
    uint32_t flags;
    uint32_t os_specific;
    uint32_t direct_pointer[12];
    uint32_t indirect1;
    uint32_t indirect2;
    uint32_t indirect3;
    uint32_t gen_num;
    uint32_t later1; // will be implemented later by the fooldriver
    uint32_t size_high;
    uint32_t frag;
    uint32_t os_spec2[3];
}ext2_inode;


int main()
{
    ext2_superblock super;
    ext2_superblock_ext super_ext;


    printf("ext2 fools driver\n");
    printf("reading superblock...\n\n");

    fseek(stdin,1024,SEEK_SET);
    fread(&super,sizeof(super),1,stdin);

    printf("block size: %i\n",1024<<super.block_size);
    printf("block count: %i\n",super.blocks_count);
    printf("inode count: %i\n\n",super.inodes_count);

    printf("blocks/group: %i\n",super.blocks_per_group);
    printf("inodes/group: %i\n\n",super.inodes_per_group);

    printf("signature: 0x%x\n",super.ext2_sig);
    printf("fs state: %i\n",super.fs_state);
    printf("version: %i.%i\n\n",super.version_major,super.version_minor);

    if(super.version_major>=1)
    {
	printf("getting extended fields...\n\n");
	fread(&super_ext,sizeof(super_ext),1,stdin);

	printf("first (non reserved) inode: %i\n",super_ext.first_inode);
	printf("inode size: %i\n\n",super_ext.size_inode);

	printf("opt_features: %i\n",super_ext.features_opt);
	printf("req_features: %i\n",super_ext.features_req);
	printf("write_features: %i\n\n",super_ext.features_write);

	printf("volume name: %s\n",super_ext.vol_name);
	printf("mount path: %s\n\n",super_ext.last_path);

    }

    ext2_blockgroup_desc desc;
    printf("getting block group descriptors...\n\n");
    //TODO: only correct for 1024bytes/block. read more than one!!!
    int block_size=1024;
    int descriptor_start_block=2;
    fseek(stdin,block_size*descriptor_start_block,SEEK_SET);
    fread(&desc,sizeof(desc),1,stdin);
    printf("block usage bitmap: 0x%x\n",desc.addr_block_bitmap);
    printf("inode usage bitmap: 0x%x\n",desc.addr_inode_bitmap);
    printf("inode table: 0x%x\n\n",desc.addr_inode_table);
    printf("unalloc blocks: %i\n",desc.unalloc_blocks_count);
    printf("unalloc inodes: %i\n",desc.unalloc_inodes_count);
    printf("directories: %i\n\n",desc.dir_count);

    //TODO: check for version >1
    int inode_size=128;
    ext2_inode inode;
    printf("reading inode 2 (root dir)...\n\n");
    fseek(stdin,block_size*desc.addr_inode_table,SEEK_SET);
    fread(&inode,sizeof(inode),1,stdin);

    fread(&inode,sizeof(inode),1,stdin);

    printf("---------- root ---------\n");
    printf("uid/gid: %i/%i\n",inode.user_id,inode.group_id);
    printf("hardlinks: %i\n",inode.hardlink_count);
    printf("size low/high: %i/%i\n",inode.size_low,inode.size_high);
    printf("direct block pointer 0: %i\n\n",inode.direct_pointer[0]);

    // read dir
    char buf[256];
    fseek(stdin,block_size*inode.direct_pointer[0],SEEK_SET);

    int pos=0;
    while(pos<inode.size_low)
    {
	ext2_dir dir;
	fread(&dir,sizeof(dir),1,stdin);
	printf("inode: %i\n",dir.inode);
	printf("total size: %i\n",dir.size);
	printf("length low/high: %i/%i\n\n",dir.name_length_low,dir.name_length_high);
	int l=fread(buf,sizeof(char),dir.name_length_low,stdin);
	buf[l]=0;
	printf("name: %s\n\n",buf);
	fseek(stdin,dir.size-8-dir.name_length_low,SEEK_CUR);
	pos+=dir.size;
    }


    puts("");
    puts("");

    


}