#include "fs.h"

struct Super *super;
static int debug = 0;

u_int nbitmap;		// number of bitmap blocks
u_int *bitmap;		// bitmap blocks mapped in memory

void file_flush(struct File*);
int block_is_free(u_int);

// Return the virtual address of this disk block.
u_int
diskaddr(u_int blockno)
{
	if(super && blockno >= super->s_nblocks)
		panic("bad block number %08x in diskaddr", blockno);
	return DISKMAP+blockno*BY2BLK;
}

// Is this virtual address mapped?
u_int
va_is_mapped(u_int va)
{
	return (vpd[PDX(va)]&PTE_P) && (vpt[VPN(va)]&PTE_P);
}

// Is this disk block mapped?
u_int
block_is_mapped(u_int blockno)
{
	u_int va;

	va = diskaddr(blockno);
	if (va_is_mapped(va))
		return va;
	return 0;
}

// Is this virtual address dirty?
u_int
va_is_dirty(u_int va)
{
	return vpt[VPN(va)]&PTE_D;
}

// Is this block dirty?
u_int
block_is_dirty(u_int blockno)
{
	u_int va;

	va = diskaddr(blockno);
	return va_is_mapped(va) && va_is_dirty(va);
}

// Allocate a page to hold the disk block
int
map_block(u_int blockno)
{
	if (block_is_mapped(blockno))
		return 0;
	return sys_mem_alloc(0, diskaddr(blockno), PTE_U|PTE_P|PTE_W);
}

// Make sure a particular disk block is loaded into memory.
// Return 0 on success, or a negative error code on error.
// 
// If blk!=0, set *blk to the address of the block in memory.
//
// If isnew!=0, set *isnew to 0 if the block was already in memory,
//	or to 1 if the block was loaded off disk to satisfy this request.
//
// (Isnew lets callers like file_get_block clear any memory-only
// fields from the disk blocks when they come in off disk.)
//
// Hint: use diskaddr, block_is_mapped, sys_mem_alloc, and ide_read.
int
read_block(u_int blockno, void **blk, u_int *isnew)
{
	u_int va;

	if (super && blockno >= super->s_nblocks)
		panic("reading non-existent block %08x\n", blockno);

	if (bitmap && block_is_free(blockno))
		panic("reading free block %08x\n", blockno);

	va = diskaddr(blockno);
	if (blk)
	  *blk = (void *)va;
	if (va_is_mapped(va)) {
	  if (isnew)
	    *isnew = 0;
	  return 0;
	}

	if (isnew)
	  *isnew = 1;

	if (sys_mem_alloc(0, diskaddr(blockno), PTE_U|PTE_P|PTE_W)) {
	  return -E_NO_MEM;
	}
	
	ide_read(DISKNO, blockno*SECT2BLK, (void *)va, SECT2BLK);
	return 0;
}

// Copy the current contents of the block out to disk.
// Then clear the PTE_D bit using sys_mem_map.
// The PTE_USER constant in inc/mmu.h may be useful!
void
write_block(u_int blockno)
{
	u_int va;

	if (!block_is_mapped(blockno)) {
	  if (debug) printf("write unmapped block %08x\n", blockno);
	  return;
	}
	
	va = diskaddr(blockno);
	if (va_is_dirty(va)) {
	  // write it out
	  ide_write(DISKNO, blockno*SECT2BLK, (void *)va, SECT2BLK);
	  sys_mem_map(0, va, 0, va, 
		      ((vpt[VPN(va)] & PTE_USER) & (~PTE_D)));
	}
}

// Make sure this block is unmapped.
void
unmap_block(u_int blockno)
{
	int r;

	if(!block_is_mapped(blockno))
		return;

	assert(block_is_free(blockno) || !block_is_dirty(blockno));

	if ((r = sys_mem_unmap(0, diskaddr(blockno))) < 0)
		panic("unmap_block: sys_mem_unmap: %e", r);
	assert(!block_is_mapped(blockno));
}

// Check to see if the block bitmap indicates that block 'blockno' is free.
// Return 1 if the block is free, 0 if not.
int
block_is_free(u_int blockno)
{
	if (super == 0 || blockno >= super->s_nblocks)
		return 0;
	if (bitmap[blockno / 32] & (1 << (blockno % 32)))
		return 1;
	return 0;
}

// Mark a block free in the bitmap
void
free_block(u_int blockno)
{
	// Blockno zero is the null pointer of block numbers.
	if (blockno == 0)
		panic("attempt to free zero block");
	bitmap[blockno/32] |= 1<<(blockno%32);
}

static void
flush_bitmap(void)
{
  int i;
  for (i=2; i<nbitmap+2; i++) {
    write_block(i);
  }
}

// Search the bitmap for a free block and allocate it.
// 
// Return block number allocated on success, -E_NO_DISK if we are out of blocks.
int
alloc_block_num(void)
{
  static int last_free_block = 0;
  int i;

  for (i=last_free_block; i < super->s_nblocks; i++) {
    if (block_is_free(i)) {
      last_free_block=i;      
      bitmap[i/32] &= (~(1<<(i%32)));
      flush_bitmap();
      return i;
    }
  }
  for (i=3; i < last_free_block; i++) {
    if (block_is_free(i)) {
      last_free_block=i;
      bitmap[i/32] &= (~(1<<(i%32)));
      flush_bitmap();
      return i;
    }
  }
  return -E_NO_DISK;
}

// Allocate a block -- first find a free block in the bitmap,
// then map it into memory.
int
alloc_block(void)
{
	int r, bno;

	if ((r = alloc_block_num()) < 0)
		return r;
	bno = r;

	if ((r = map_block(bno)) < 0) {
		free_block(bno);
		return r;
	}
	return bno;
}

// Read and validate the file system super-block.
void
read_super(void)
{
	int r;
	void *blk;

	if ((r = read_block(1, &blk, 0)) < 0)
		panic("cannot read superblock: %e", r);

	super = blk;
	if (super->s_magic != FS_MAGIC)
		panic("bad file system magic number");

	if (super->s_nblocks > DISKMAX/BY2BLK)
		panic("file system is too large");

	printf("superblock is good\n");
}

// Read and validate the file system bitmap.
//
// Read all the bitmap blocks into memory.
// Set the "bitmap" pointer to point at the beginning of the first bitmap block.
// 
// Check that they're all marked as inuse
// (for each block i, assert(!block_is_free(i))).
void
read_bitmap(void)
{
	u_int i;
	void *blk;

	nbitmap = ((super->s_nblocks + BIT2BLK - 1) / BIT2BLK);
	if ((read_block(2, &blk, 0)) < 0) {
	  panic("Failed to read initial system bitmap for FS\n");
	}
	bitmap = blk;

	for (i = 1; i < nbitmap; i++) {
	  if ((read_block(i+2, NULL, 0)) < 0) {
	    panic("Failed to read bitmap for FS\n");
	  }
	}

	// Make sure the reserved and root blocks are marked in-use
	assert(!block_is_free(0));
	assert(!block_is_free(1));
	assert(bitmap);
	for (i = 0; i < nbitmap; i++) {
	  assert(!block_is_free(i+2));
	}

	printf("read_bitmap is good\n");
}

// Test that write_block works, by smashing the superblock and reading it back.
void
check_write_block(void)
{
	super = 0;

	// back up super block
	read_block(0, 0, 0);
	bcopy((char*)diskaddr(1), (char*)diskaddr(0), BY2PG);

	// smash it 
	strcpy((char*)diskaddr(1), "OOPS!\n");
	write_block(1);
	assert(block_is_mapped(1));
	assert(!va_is_dirty(diskaddr(1)));

	// clear it out
	if (sys_mem_unmap(0, diskaddr(1)) < 0) {
	  printf("sys_mem_unmap in check_write_block failed\n");
	}
	assert(!block_is_mapped(1));

	// read it back in
	read_block(1, 0, 0);
	assert(strcmp((char*)diskaddr(1), "OOPS!\n") == 0);

	// fix it
	bcopy((char*)diskaddr(0), (char*)diskaddr(1), BY2PG);
	write_block(1);
	super = (struct Super*)diskaddr(1);

	printf("write_block is good\n");
}

// Initialize the file system
void
fs_init(void)
{
	read_super();
	check_write_block();
	read_bitmap();
}

// Like pgdir_walk but for files.  Set *ppdiskbno to a pointer to the disk block number
// for the filebno'th block in file f.  If alloc is set and we need an indirect
// block, allocate it.  
int
file_block_walk(struct File *f, u_int filebno, u_int **ppdiskbno, u_int alloc)
{
	int r;
	u_int *ptr;
	void *blk;

	if (filebno < NDIRECT)
		ptr = &f->f_direct[filebno];
	else if (filebno < NINDIRECT) {
		if (f->f_indirect == 0) {
			if (alloc == 0)
				return -E_NOT_FOUND;
			if ((r = alloc_block()) < 0)
				return r;
			f->f_indirect = r;
		}
		if ((r=read_block(f->f_indirect, &blk, 0)) < 0)
			return r;
		assert(blk != 0);
		ptr = (u_int*)blk + filebno;
	} else
		return -E_INVAL;

	*ppdiskbno = ptr;
	return 0;
}

// Set *diskbno to the disk block number for the filebno'th block in file f.
// If alloc is set and the block does not exist, allocate it.
int
file_map_block(struct File *f, u_int filebno, u_int *diskbno, u_int alloc)
{
	int r;
	u_int *ptr;

	if ((r = file_block_walk(f, filebno, &ptr, alloc)) < 0)
		return r;
	if (*ptr == 0) {
		if (alloc == 0)
			return -E_NOT_FOUND;
		if ((r = alloc_block()) < 0)
			return r;
		*ptr = r;
	}
	*diskbno = *ptr;
	return 0;
}

// Remove a block from file f.  If it's not there, just silently succeed.
int
file_clear_block(struct File *f, u_int filebno)
{
	int r;
	u_int *ptr;

	if ((r = file_block_walk(f, filebno, &ptr, 0)) < 0)
		return r;
	if (*ptr) {
		free_block(*ptr);
		*ptr = 0;
	}
	return 0;
}

// Set *blk to point at the filebno'th block in file f.
// 
// Hint: use file_map_block and read_block.
int
file_get_block(struct File *f, u_int filebno, void **blk)
{
	int r, isnew;
	u_int diskbno;

	if ((r = file_map_block(f, filebno, &diskbno, 1)) < 0) {
	  return -E_NOT_FOUND;
	}
	if ((r = read_block(diskbno, blk, &isnew)) < 0) {
	  return -E_NOT_FOUND;
	}

	// Don't need to maintain reference counts anymore.

	return 0;
}

// Mark the offset/BY2BLK'th block dirty in file f
// by writing its first word to itself.  
int
file_dirty(struct File *f, u_int offset)
{
	int r;
	void *blk;

	if ((r = file_get_block(f, offset/BY2BLK, &blk)) < 0)
		return r;
	*(volatile char*)blk = *(volatile char*)blk;
	return 0;
}

// Try to find a file named "name" in dir.  If so, set *file to it.
int
dir_lookup(struct File *dir, char *name, struct File **file)
{
	int r;
	u_int i, j, nblock;
	void *blk;
	struct File *f;

	// search dir for name
	nblock = dir->f_size / BY2BLK;
	for (i=0; i<nblock; i++) {
		if ((r=file_get_block(dir, i, &blk)) < 0)
			return r;
		f = blk;
		for (j=0; j<FILE2BLK; j++)
			if (strcmp(f[j].f_name, name) == 0) {
				*file = &f[j];
				f[j].f_dir = dir;
				return 0;
			}
	}
	return -E_NOT_FOUND;	
}

// Set *file to point at a free File structure in dir.
int
dir_alloc_file(struct File *dir, struct File **file)
{
	int r;
	u_int nblock, i , j;
	void *blk;
	struct File *f;

	nblock = dir->f_size / BY2BLK;
	for (i=0; i<nblock; i++) {
		if ((r=file_get_block(dir, i, &blk)) < 0)
			return r;
		f = blk;
		for (j=0; j<FILE2BLK; j++)
			if (f[j].f_name[0] == '\0') {
				*file = &f[j];
				return 0;
			}
	}
	dir->f_size += BY2BLK;
	if ((r = file_get_block(dir, i, &blk)) < 0)
		return r;
	f = blk;
	*file = &f[0];
	return 0;		
}

// Skip over slashes.
char*
skip_slash(char *p)
{
	while (*p == '/')
		p++;
	return p;
}

// Evaluate a path name, starting at the root.
// On success, set *pfile to the file we found
// and set *pdir to the directory the file is in.
// If we cannot find the file but find the directory
// it should be in, set *pdir and copy the final path
// element into lastelem.
int
walk_path(char *path, struct File **pdir, struct File **pfile, char *lastelem)
{
	char *p;
	char name[MAXNAMELEN];
	struct File *dir, *file;
	int r;

	// if (*path != '/')
	//	return -E_BAD_PATH;
	path = skip_slash(path);
	file = &super->s_root;
	dir = 0;
	name[0] = 0;

	if(pdir)
		*pdir = 0;
	*pfile = 0;
	while (*path != '\0') {
		dir = file;
		p = path;
		while (*path != '/' && *path != '\0')
			path++;
		if (path - p >= MAXNAMELEN)
			return -E_BAD_PATH;
		bcopy(p, name, path - p);
		name[path - p] = '\0';
		path = skip_slash(path);

		if (dir->f_type != FTYPE_DIR)
			return -E_NOT_FOUND;

		if ((r=dir_lookup(dir, name, &file)) < 0) {
			if(r == -E_NOT_FOUND && *path == '\0') {
				if(pdir)
					*pdir = dir;
				if (lastelem)
					strcpy(lastelem, name);
				*pfile = 0;
			}
			return r;
		}
	}

	if(pdir)
		*pdir = dir;
	*pfile = file;
	return 0;
}

// Open "path".  On success set *pfile to point at the file and return 0.
// On error return < 0.
int
file_open(char *path, struct File **file)
{
  int r;
  struct File *dir;
  char name[MAXNAMELEN];

  if ((r = walk_path(path, &dir, file, name)) == 0) {
    return 0;
  }
  return r;
}

// Create "path".  On success set *file to point at the file and return 0.
// On error return < 0.
int
file_create(char *path, struct File **file)
{
	char name[MAXNAMELEN];
	int r;
	struct File *dir, *f;

	if ((r = walk_path(path, &dir, &f, name)) == 0)
		return -E_FILE_EXISTS;
	if (r != -E_NOT_FOUND || dir == 0)
		return r;
	if (dir_alloc_file(dir, &f) < 0)
		return r;
	strcpy(f->f_name, name);
	*file = f;
	return 0;
}

// Truncate file down to newsize bytes.  
// Since the file is shorter, we can free the blocks
// that were used by the old bigger version but not
// by our new smaller self.  For both the old and new sizes,
// figure out the number of blocks required.
// and then clear the blocks from new_nblocks to old_nblocks.
// If the new_nblocks is no more than NDIRECT, free the indirect
// block too.  (Remember to clear the f->f_indirect pointer so
// you'll know whether it's valid!)
//
// Hint: use file_clear_block.
void
file_truncate(struct File *f, u_int newsize)
{
	int bno, old_nblocks, new_nblocks;

	if (f->f_size <= newsize) 
	  return;

	new_nblocks = (newsize + BY2BLK - 1)/BY2BLK;
	old_nblocks = (f->f_size + BY2BLK -1) / BY2BLK;

	for (bno = old_nblocks-1; bno >= new_nblocks; bno--) {
	  file_clear_block(f, bno);
	}
	if ((new_nblocks <= NDIRECT) && (old_nblocks > NDIRECT)) {
	  free_block(f->f_indirect);
	  f->f_indirect = 0;
	}
}

int
file_set_size(struct File *f, u_int newsize)
{
	if (f->f_size > newsize)
		file_truncate(f, newsize);
	f->f_size = newsize;
	if (f->f_dir)
		file_flush(f->f_dir);
	return 0;
}

// Flush the contents of file f out to disk.
// Loop over all the blocks in file.
// Translate the file block number into a disk block number
// and then check whether that disk block is dirty.  If so, write it out.
//
// Hint: use file_map_block, block_is_dirty, and write_block.
void
file_flush(struct File *f)
{
  u_int bno, diskbno;
  u_int nblocks;
  int r;

  nblocks = (f->f_size + BY2BLK - 1) / BY2BLK;
  for (bno = 0; bno < nblocks; bno++) {
    if ((r = file_map_block(f, bno, &diskbno, 1)) == 0) {
      // write block already checks dirty bit for us
      write_block(diskbno);
    }
  }
}

// Sync the entire file system.  A big hammer.
void
fs_sync(void)
{
	int i;

	for (i=0; i<super->s_nblocks; i++)
		if (block_is_dirty(i))
			write_block(i);
}

// Close a file.
void
file_close(struct File *f)
{
	file_flush(f);
	if (f->f_dir)
		file_flush(f->f_dir);
}

// Remove a file by truncating it and then zeroing the name.
int
file_remove(char *path)
{
	int r;
	struct File *f;

	if ((r = walk_path(path, 0, &f, 0)) < 0)
		return r;

	file_truncate(f, 0);
	f->f_name[0] = '\0';
	file_flush(f);
	if (f->f_dir)
		file_flush(f->f_dir);

	return 0;
}