// ext2.c
// Author: Josh Holtrop
// Date: 08/22/04
// Modified: 12/24/04

#include "hos_defines.h"
#include "fs/devices.h"
#include "kout.h"
#include "ext2.h"
#include "mm/vmm.h"
#include "fs/vfs.h"
#include "lang/asmfuncs.h"
#include "functions.h"

/* Turning an inode number into a (group, inode_index) pair:
 * group = (inode - 1) / s_inodes_per_group
 * index = (inode - 1) % s_inodes_per_group
 */
   

// initialize the filesystem driver
int	ext2_init(int fsID)
{
	vfs_fs_t *fs;
	if (( fs = New(vfs_fs_t) ))			// give the VFS system our FS structure
	{
		fs->mount_super = ext2_mount_super;
		fs->umount_super = ext2_umount_super;
		fs->mkfs = ext2_mkfs;
		fs->stat = ext2_stat;
		vfs_register_fs(fsID, fs);
		return 0;
	}
	return -1;
}


// create an ext2 filesystem on the given device
int	ext2_mkfs(major_t major, minor_t minor)
{
	return 0;
}


// mount the superblock of the filesystem and return a pointer to it, if valid
void	*ext2_mount_super(major_t major, minor_t minor)
{
	ext2_super_block_t *super = kmalloc(1024);
	block_read(major, minor, 2, 2, super);
	if (super->s_magic != EXT2_MAGIC)			// not an ext2 filesystem
	{
		kfree(super);
		return NULL;
	}
	return super;
}

// stat a file, return a structure of info about it
int	ext2_stat(vfs_mount_t *mount, char *file, vfs_stat_t *stat)
{
	u32_t	inode_number = ext2_get_inode_number(mount, file);
	if (!inode_number)
		return -1;
	ext2_inode_t inode = ext2_get_inode(mount, inode_number);

	switch(inode.i_mode & EXT2_I_MODE_TYPE_MASK)
	{
		case EXT2_I_MODE_FIFO:	stat->type = VFS_FT_FIFO;
		case EXT2_I_MODE_CHAR:	stat->type = VFS_FT_CHAR;
		case EXT2_I_MODE_DIR:	stat->type = VFS_FT_DIR;
		case EXT2_I_MODE_BLOCK:	stat->type = VFS_FT_BLOCK;
		case EXT2_I_MODE_FILE:	stat->type = VFS_FT_FILE;
		case EXT2_I_MODE_SYM:	stat->type = VFS_FT_SYMLINK;
		case EXT2_I_MODE_SOCK:	stat->type = VFS_FT_SOCK;
		default:		stat->type = VFS_FT_UNKNOWN;
	}
	stat->size	= inode.i_size;
	stat->inode	= inode_number;
	stat->permissions = inode.i_mode & EXT2_I_MODE_ATTR_MASK;
	stat->uid	= inode.i_uid;
	stat->gid	= inode.i_gid;
	stat->atime	= inode.i_atime;
	stat->mtime	= inode.i_mtime;
	stat->ctime	= inode.i_ctime;
	stat->links	= inode.i_links_count;

	return 0;
}

// returns the inode number that the given file name points to
u32_t	ext2_get_inode_number(vfs_mount_t *mount, char *file)
{
	if (file[0] != '/')
		return 0;
	int length = strlen(file);
	if (length == 1)
		return 2;
	char *fil = kmalloc(length + 1);
	strcpy(fil, file);
	if (fil[length-1] == '/')
	{
		length--;
		fil[length] = 0;
	}
	u32_t inode_number = 0;
	// TODO: get inode number
	
	kfree(fil);
	return inode_number;
}

// open an inode for reading
ext2_open_inode_t *ext2_open_inode(vfs_mount_t *mount, u32_t inode_number)
{
	ext2_inode_t inode = ext2_get_inode(mount, inode_number);
	ext2_open_inode_t *open_inode = New(ext2_open_inode_t);
	open_inode->inode = inode;
	open_inode->block = 0;
	open_inode->block_pointers = NULL;
	open_inode->block_pointers_start = 0;
	mount->refs++;
	return open_inode;
}

// seek to a certain block of an open inode
int	ext2_inode_seek(ext2_open_inode_t *open_inode, u32_t block_number)
{
	if (open_inode->inode.i_size <= (block_number << (10 + super->s_log_block_size)))
		return -1;	// at or past EOF
	open_inode->block = block_number;
	return 0;
}

// returns number of bytes read
int	ext2_read_inode_block(vfs_mount_t *mount, ext2_open_inode_t *open_inode, void *block)
{
	ext2_super_block_t *super = mount->super;
	if (open_inode->inode.i_size <= (open_inode->block << (10 + super->s_log_block_size)))
		return 0;	// at or past EOF
	u32_t	leftover_bytes = open_inode->inode.i_size - (open_inode->block << (10 + super->s_log_block_size));
	u32_t	block_number = ext2_block_number(mount, open_inode);
	block_read(mount->major, mount->minor, ext2_FSToDiskBlock(block_number, super),
		2 << super->s_log_block_size, block);
	open_inode->block++;
	return min(leftover_bytes, 1024 << super->s_log_block_size);
}

// transform open_inode->block (a relative block number) to an absolute block number for the filesystem
u32_t	ext2_block_number(vfs_mount_t *mount, ext2_open_inode_t *open_inode)
{
	if (open_inode->block < 12)
		return open_inode->inode.i_block[open_inode->block];
	ext2_super_block_t *super = mount->super;
	int pointersPerBlock = 256 << super->s_log_block_size;
	if (open_inode->block_pointers &&			// there is a block pointers cache block allocated
		(open_inode->block >= open_inode->block_pointers_start) &&	// and the block number is in it
		(open_inode->block < (open_inode->block_pointers_start + pointersPerBlock)))
		return open_inode->block_pointers[open_inode->block - open_inode->block_pointers_start];
	u32_t	rel_block = open_inode->block - 12;
	if (!open_inode->block_pointers)
		open_inode->block_pointers = kmalloc(pointersPerBlock << 2);
	if (rel_block < pointersPerBlock)			// indirect block in i_block[12]
	{
		block_read(mount->major, mount->minor, ext2_FSToDiskBlock(open_inode->inode.i_block[12], super),
			2 << super->s_log_block_size, open_inode->block_pointers);
		open_inode->block_pointers_start = 12;
		return open_inode->block_pointers[rel_block];
	}
	rel_block -= pointersPerBlock;
	if (rel_block < (pointersPerBlock * pointersPerBlock))	// double-indirect block in i_block[13]
	{
		block_read(mount->major, mount->minor, ext2_FSToDiskBlock(open_inode->inode.i_block[13], super),
			2 << super->s_log_block_size, open_inode->block_pointers);
		u32_t	real_block = open_inode->block_pointers[rel_block / pointersPerBlock];
		block_read(mount->major, mount->minor, ext2_FSToDiskBlock(real_block, super),
			2 << super->s_log_block_size, open_inode->block_pointers);
		open_inode->block_pointers_start = 12 + pointersPerBlock + rel_block - (rel_block % pointersPerBlock);
		return open_inode->block_pointers[rel_block % pointersPerBlock];
	}
	// this code shouldn't run unless we are dealing with a 65+mb file ...
	rel_block -= pointersPerBlock * pointersPerBlock;
	block_read(mount->major, mount->minor, ext2_FSToDiskBlock(open_inode->inode.i_block[14], super),
		2 << super->s_log_block_size, open_inode->block_pointers);
	u32_t	index_1 = rel_block / (pointersPerBlock * pointersPerBlock);
	u32_t	leftover_1 = rel_block % (pointersPerBlock * pointersPerBlock);
	u32_t	block_1 = open_inode->block_pointers[index_1];
	block_read(mount->major, mount->minor, ext2_FSToDiskBlock(block_1, super),
		2 << super->s_log_block_size, open_inode->block_pointers);
	u32_t	index_2 = leftover_1 / pointersPerBlock;
	u32_t	leftover_2 = leftover_1 % pointersPerBlock;
	u32_t	block_2 = open_inode->block_pointers[index_2];
	block_read(mount->major, mount->minor, ext2_FSToDiskBlock(block_2, super),
		2 << super->s_log_block_size, open_inode->block_pointers);
	open_inode->block_pointers_start = 12 + (pointersPerBlock + 1) * pointersPerBlock + rel_block - (rel_block % pointersPerBlock);
	return open_inode->block_pointers[leftover_2];
}

// close an open inode
int	ext2_close_inode(vfs_mount_t *mount, ext2_open_inode_t *open_inode)
{
	mount->refs--;
	if (open_inode->block_pointers)
		kfree(open_inode->block_pointers);		// free the block pointers cache
	kfree(open_inode);
	return 0;
}

// read the inode structure from the device and return it
ext2_inode_t	ext2_get_inode(vfs_mount_t *mount, u32_t inode)
{
	ext2_super_block_t *super = mount->super;
	inode--;				// turn inode into a 0-based index
	u32_t group = inode / super->s_inodes_per_group;
	u32_t index = inode % super->s_inodes_per_group;
	u32_t inodeAddr = (ext2_get_group_desc(mount, group).bg_inode_table <<
			 (10 + super->s_log_block_size)) + (index << 7);
	void *block = kmalloc(512);
	block_read(mount->major, mount->minor, inodeAddr >> 9, 1, block);
	ext2_inode_t in = *(ext2_inode_t *)(block + (inodeAddr & 0x1FF));
	kfree(block);
	return in;
}

// read the group descriptor structure from the device and return it
ext2_group_desc_t	ext2_get_group_desc(vfs_mount_t *mount, u32_t group)
{
	ext2_super_block_t *super = mount->super;
	u32_t groupDescAddr = ((1 + super->s_first_data_block) << (10 + super->s_log_block_size)) + (group << 5);
	void *block = kmalloc(512);
	block_read(mount->major, mount->minor, groupDescAddr >> 9, 1, block);
	ext2_group_desc_t gd = *(ext2_group_desc_t *)(block + (groupDescAddr & 0x1FF));
	kfree(block);
	return gd;
}

// called when we are unmounting this filesystem mount
int	ext2_umount_super(vfs_mount_t *mount)
{
	return kfree(mount->super);			// free memory that the superblock was taking
}