/*
 * Copyright (c) 2008 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup fs
 * @{
 */ 

/**
 * @file	fat_ops.c
 * @brief	Implementation of VFS operations for the FAT file system server.
 */

#include "fat.h"
#include "../../vfs/vfs.h"
#include <libfs.h>
#include <ipc/ipc.h>
#include <async.h>
#include <errno.h>
#include <string.h>
#include <byteorder.h>
#include <libadt/hash_table.h>
#include <libadt/list.h>
#include <assert.h>
#include <futex.h>

#define BS_BLOCK		0

#define FIN_KEY_DEV_HANDLE	0
#define FIN_KEY_INDEX		1

/** Hash table of FAT in-core nodes. */
hash_table_t fin_hash;

/** List of free FAT in-core nodes. */
link_t ffn_head;

#define FAT_NAME_LEN		8
#define FAT_EXT_LEN		3

#define FAT_PAD			' ' 

#define FAT_DENTRY_UNUSED	0x00
#define FAT_DENTRY_E5_ESC	0x05
#define FAT_DENTRY_DOT		0x2e
#define FAT_DENTRY_ERASED	0xe5

static void dentry_name_canonify(fat_dentry_t *d, char *buf)
{
	int i;

	for (i = 0; i < FAT_NAME_LEN; i++) {
		if (d->name[i] == FAT_PAD) {
			buf++;
			break;
		}
		if (d->name[i] == FAT_DENTRY_E5_ESC)
			*buf++ = 0xe5;
		else
			*buf++ = d->name[i];
	}
	if (d->ext[0] != FAT_PAD)
		*buf++ = '.';
	for (i = 0; i < FAT_EXT_LEN; i++) {
		if (d->ext[i] == FAT_PAD) {
			*buf = '\0';
			return;
		}
		if (d->ext[i] == FAT_DENTRY_E5_ESC)
			*buf++ = 0xe5;
		else
			*buf++ = d->ext[i];
	}
}

/* TODO and also move somewhere else */
typedef struct {
	void *data;
} block_t;

static block_t *block_get(dev_handle_t dev_handle, off_t offset)
{
	return NULL;	/* TODO */
}

static void block_put(block_t *block)
{
	/* TODO */
}

#define FAT_BS(b)		((fat_bs_t *)((b)->data))

#define FAT_CLST_RES0	0x0000
#define FAT_CLST_RES1	0x0001	/* internally used to mark root directory */
#define FAT_CLST_FIRST	0x0002
#define FAT_CLST_BAD	0xfff7
#define FAT_CLST_LAST1	0xfff8
#define FAT_CLST_LAST8  0xffff

static block_t *fat_block_get(fat_node_t *nodep, off_t offset)
{
	block_t *bb;
	block_t *b;
	unsigned bps;
	unsigned spc;
	unsigned rscnt;		/* block address of the first FAT */
	unsigned fatcnt;
	unsigned rde;
	unsigned rds;		/* root directory size */
	unsigned sf;
	unsigned ssa;		/* size of the system area */
	unsigned clusters;
	fat_cluster_t clst = nodep->firstc;
	unsigned i;

	bb = block_get(nodep->idx->dev_handle, BS_BLOCK);
	bps = uint16_t_le2host(FAT_BS(bb)->bps);
	spc = FAT_BS(bb)->spc;
	rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
	fatcnt = FAT_BS(bb)->fatcnt;
	rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
	sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);
	block_put(bb);

	rds = (sizeof(fat_dentry_t) * rde) / bps;
	rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
	ssa = rscnt + fatcnt * sf + rds;

	if (nodep->idx->index == FAT_CLST_RES1) {
		/* root directory special case */
		assert(offset < rds);
		b = block_get(nodep->idx->dev_handle,
		    rscnt + fatcnt * sf + offset);
		return b;
	}

	clusters = offset / spc; 
	for (i = 0; i < clusters; i++) {
		unsigned fsec;	/* sector offset relative to FAT1 */
		unsigned fidx;	/* FAT1 entry index */

		assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
		fsec = (clst * sizeof(fat_cluster_t)) / bps;
		fidx = clst % (bps / sizeof(fat_cluster_t));
		/* read FAT1 */
		b = block_get(nodep->idx->dev_handle, rscnt + fsec);
		clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
		assert(clst != FAT_CLST_BAD);
		assert(clst < FAT_CLST_LAST1);
		block_put(b);
	}

	b = block_get(nodep->idx->dev_handle, ssa +
	    (clst - FAT_CLST_FIRST) * spc + offset % spc);

	return b;
}

static void fat_node_initialize(fat_node_t *node)
{
	node->idx = NULL;
	node->type = 0;
	link_initialize(&node->fin_link);
	link_initialize(&node->ffn_link);
	node->size = 0;
	node->lnkcnt = 0;
	node->refcnt = 0;
	node->dirty = false;
}

static uint16_t fat_bps_get(dev_handle_t dev_handle)
{
	block_t *bb;
	uint16_t bps;
	
	bb = block_get(dev_handle, BS_BLOCK);
	assert(bb != NULL);
	bps = uint16_t_le2host(FAT_BS(bb)->bps);
	block_put(bb);

	return bps;
}

typedef enum {
	FAT_DENTRY_SKIP,
	FAT_DENTRY_LAST,
	FAT_DENTRY_VALID
} fat_dentry_clsf_t;

static fat_dentry_clsf_t fat_classify_dentry(fat_dentry_t *d)
{
	if (d->attr & FAT_ATTR_VOLLABEL) {
		/* volume label entry */
		return FAT_DENTRY_SKIP;
	}
	if (d->name[0] == FAT_DENTRY_ERASED) {
		/* not-currently-used entry */
		return FAT_DENTRY_SKIP;
	}
	if (d->name[0] == FAT_DENTRY_UNUSED) {
		/* never used entry */
		return FAT_DENTRY_LAST;
	}
	if (d->name[0] == FAT_DENTRY_DOT) {
		/*
		 * Most likely '.' or '..'.
		 * It cannot occur in a regular file name.
		 */
		return FAT_DENTRY_SKIP;
	}
	return FAT_DENTRY_VALID;
}

static void fat_sync_node(fat_node_t *node)
{
	/* TODO */
}

/** Instantiate a FAT in-core node. */
static void *
fat_node_get(dev_handle_t dev_handle, fs_index_t index)
{
	return NULL;	/* TODO */
}

static void fat_node_put(void *node)
{
	/* TODO */
}

static void *fat_create(int flags)
{
	return NULL;	/* not supported at the moment */
}

static int fat_destroy(void *node)
{
	return ENOTSUP;	/* not supported at the moment */
}

static bool fat_link(void *prnt, void *chld, const char *name)
{
	return false;	/* not supported at the moment */
}

static int fat_unlink(void *prnt, void *chld)
{
	return ENOTSUP;	/* not supported at the moment */
}

static void *fat_match(void *prnt, const char *component)
{
	fat_node_t *parentp = (fat_node_t *)prnt;
	char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
	unsigned i, j;
	unsigned bps;		/* bytes per sector */
	unsigned dps;		/* dentries per sector */
	unsigned blocks;
	fat_dentry_t *d;
	block_t *b;

	bps = fat_bps_get(parentp->idx->dev_handle);
	dps = bps / sizeof(fat_dentry_t);
	blocks = parentp->size / bps + (parentp->size % bps != 0);
	for (i = 0; i < blocks; i++) {
		unsigned dentries;
		
		b = fat_block_get(parentp, i);
		dentries = (i == blocks - 1) ?
		    parentp->size % sizeof(fat_dentry_t) :
		    dps;
		for (j = 0; j < dentries; j++) { 
			d = ((fat_dentry_t *)b->data) + j;
			switch (fat_classify_dentry(d)) {
			case FAT_DENTRY_SKIP:
				continue;
			case FAT_DENTRY_LAST:
				block_put(b);
				return NULL;
			default:
			case FAT_DENTRY_VALID:
				dentry_name_canonify(d, name);
				break;
			}
			if (strcmp(name, component) == 0) {
				/* hit */
				fat_idx_t *idx = fat_idx_map(
				    parentp->idx->dev_handle, parentp->firstc,
				    i * dps + j);
				void *node = fat_node_get(idx->dev_handle,
				    idx->index);
				block_put(b);
				return node;
			}
		}
		block_put(b);
	}

	return NULL;
}

static fs_index_t fat_index_get(void *node)
{
	fat_node_t *fnodep = (fat_node_t *)node;
	if (!fnodep)
		return 0;
	return fnodep->idx->index;
}

static size_t fat_size_get(void *node)
{
	return ((fat_node_t *)node)->size;
}

static unsigned fat_lnkcnt_get(void *node)
{
	return ((fat_node_t *)node)->lnkcnt;
}

static bool fat_has_children(void *node)
{
	fat_node_t *nodep = (fat_node_t *)node;
	unsigned bps;
	unsigned dps;
	unsigned blocks;
	block_t *b;
	unsigned i, j;

	if (nodep->type != FAT_DIRECTORY)
		return false;

	bps = fat_bps_get(nodep->idx->dev_handle);
	dps = bps / sizeof(fat_dentry_t);

	blocks = nodep->size / bps + (nodep->size % bps != 0);

	for (i = 0; i < blocks; i++) {
		unsigned dentries;
		fat_dentry_t *d;
	
		b = fat_block_get(nodep, i);
		dentries = (i == blocks - 1) ?
		    nodep->size % sizeof(fat_dentry_t) :
		    dps;
		for (j = 0; j < dentries; j++) {
			d = ((fat_dentry_t *)b->data) + j;
			switch (fat_classify_dentry(d)) {
			case FAT_DENTRY_SKIP:
				continue;
			case FAT_DENTRY_LAST:
				block_put(b);
				return false;
			default:
			case FAT_DENTRY_VALID:
				block_put(b);
				return true;
			}
			block_put(b);
			return true;
		}
		block_put(b);
	}

	return false;
}

static void *fat_root_get(dev_handle_t dev_handle)
{
	return fat_node_get(dev_handle, FAT_CLST_RES1);
}

static char fat_plb_get_char(unsigned pos)
{
	return fat_reg.plb_ro[pos % PLB_SIZE];
}

static bool fat_is_directory(void *node)
{
	return ((fat_node_t *)node)->type == FAT_DIRECTORY;
}

static bool fat_is_file(void *node)
{
	return ((fat_node_t *)node)->type == FAT_FILE;
}

/** libfs operations */
libfs_ops_t fat_libfs_ops = {
	.match = fat_match,
	.node_get = fat_node_get,
	.node_put = fat_node_put,
	.create = fat_create,
	.destroy = fat_destroy,
	.link = fat_link,
	.unlink = fat_unlink,
	.index_get = fat_index_get,
	.size_get = fat_size_get,
	.lnkcnt_get = fat_lnkcnt_get,
	.has_children = fat_has_children,
	.root_get = fat_root_get,
	.plb_get_char =	fat_plb_get_char,
	.is_directory = fat_is_directory,
	.is_file = fat_is_file
};

void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
{
	libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
}

/**
 * @}
 */