// vfat.c
// Author: Josh Holtrop
// Date: 03/11/04
// Modified: 03/22/04

#include "vfat.h"
#include "hos_defines.h"
#include "fs/vfs.h"
#include "mm/vmm.h"
#include "lang/cstring.h"

//From Microsoft's FAT32 File System Specification
DSKSZTOSECPERCLUS DskTableFAT16 [] =
{
	{ 8400, 0}, /* disks up to 4.1 MB, the 0 value for SecPerClusVal trips an error */
	{ 32680, 2}, /* disks up to 16 MB, 1k cluster */
	{ 262144, 4}, /* disks up to 128 MB, 2k cluster */
	{ 524288, 8}, /* disks up to 256 MB, 4k cluster */
	{ 1048576, 16}, /* disks up to 512 MB, 8k cluster */
	/* The entries after this point are not used unless FAT16 is forced */
//	{ 2097152, 32}, /* disks up to 1 GB, 16k cluster */
//	{ 4194304, 64}, /* disks up to 2 GB, 32k cluster */
	{ 0xFFFFFFFF, 0} /* any disk greater than 2GB, 0 value for SecPerClusVal trips an error */
};

//From Microsoft's FAT32 File System Specification
DSKSZTOSECPERCLUS DskTableFAT32 [] =
{
	{ 66600, 0}, /* disks up to 32.5 MB, the 0 value for SecPerClusVal trips an error */
	{ 532480, 1}, /* disks up to 260 MB, .5k cluster */
	{ 16777216, 8}, /* disks up to 8 GB, 4k cluster */
	{ 33554432, 16}, /* disks up to 16 GB, 8k cluster */
	{ 67108864, 32}, /* disks up to 32 GB, 16k cluster */
	{ 0xFFFFFFFF, 64}/* disks greater than 32GB, 32k cluster */
};

int	vfat_identify(vfat_bpb *bpb)
{
	int rootDirSectors = ((bpb->rootEntries * 32) + (bpb->bytesPerSector - 1)) / bpb->bytesPerSector;
	int totalSectors = bpb->totalSectors16 ? bpb->totalSectors16 : bpb->totalSectors32;
	int fatSectors = bpb->sectorsPerFAT16 ? bpb->sectorsPerFAT16 : bpb->sectorsPerFAT32;
	int dataSectors = totalSectors - (bpb->reservedSectors + bpb->numFATs * fatSectors + rootDirSectors);
	int clusters = dataSectors / bpb->sectorsPerCluster;
	if (clusters < 4085)
		return 12;
	if (clusters < 65525)
		return 16;
	return 32;
}


int	vfat_format(Volume *vol)
{

}

FILE	*vfat_open(char *fileName, dword attributes, Volume *vol)
{
	while (*fileName == '/')
		++fileName;
	if (strlen(fileName) < 1)
		return 0;
	vfat_bpb *bpb = vfat_getBootSector(vol);
	if (!bpb) return 0;
	byte *fat = vfat_loadFAT(vol, bpb);
	if (!fat)
	{
		free(bpb);
		return 0;
	}
	int segs = string_split(fileName);	//number of sections of path (1=file is in root directory)
	int me = vfat_identify(bpb);
	if (me != 32)
	{
		if (segs == 1)			//we are looking for the file in the root directory
		{
			vfat_getEntryInRoot(vol, bpb, fileName, 0);
		}
	}
	else
	{
	}
}

byte	*vfat_loadFAT(Volume *vol, vfat_bpb *bpb)
{
	int fatSize = bpb->sectorsPerFAT16 ? bpb->sectorsPerFAT16 : bpb->sectorsPerFAT32;
	byte *fat = malloc(fatSize << 9);	//512 bytes per sector
	if (!fat) return 0;
	if (vfs_readSectorn(vol, bpb->reservedSectors, fat, fatSize))
	{
		free(fat);
		return 0;
	}
	return fat;
}

vfat_bpb *vfat_getBootSector(Volume *vol)
{
	vfat_bpb *bs;
	if (!(bs = malloc(512)))
		return 0;
	vfs_readSector(vol, 0, bs);
	return bs;
}

int	vfat_close(FILE *fp)
{
	return free(fp);
}