/*
             LUFA Library
     Copyright (C) Dean Camera, 2013.

  dean [at] fourwalledcubicle [dot] com
           www.lufa-lib.org
*/

/*
  Copyright 2013  Dean Camera (dean [at] fourwalledcubicle [dot] com)

  Permission to use, copy, modify, distribute, and sell this
  software and its documentation for any purpose is hereby granted
  without fee, provided that the above copyright notice appear in
  all copies and that both that the copyright notice and this
  permission notice and warranty disclaimer appear in supporting
  documentation, and that the name of the author not be used in
  advertising or publicity pertaining to distribution of the
  software without specific, written prior permission.

  The author disclaims all warranties with regard to this
  software, including all implied warranties of merchantability
  and fitness.  In no event shall the author be liable for any
  special, indirect or consequential damages or any damages
  whatsoever resulting from loss of use, data or profits, whether
  in an action of contract, negligence or other tortious action,
  arising out of or in connection with the use or performance of
  this software.
*/

#include "VirtualFAT.h"

static const FATBootBlock_t BootBlock =
	{
		.Bootstrap               = {0xEB, 0x3C, 0x90},
		.Description             = "mkdosfs",
		.SectorSize              = SECTOR_SIZE_BYTES,
		.SectorsPerCluster       = SECTOR_PER_CLUSTER,
		.ReservedSectors         = 1,
		.FATCopies               = 2,
		.RootDirectoryEntries    = (SECTOR_SIZE_BYTES / sizeof(FATDirectoryEntry_t)),
		.TotalSectors16          = LUN_MEDIA_BLOCKS,
		.MediaDescriptor         = 0xF8,
		.SectorsPerFAT           = 1,
		.SectorsPerTrack         = LUN_MEDIA_BLOCKS % 64,
		.Heads                   = LUN_MEDIA_BLOCKS / 64,
		.HiddenSectors           = 0,
		.TotalSectors32          = 0,
		.PhysicalDriveNum        = 0,
		.ExtendedBootRecordSig   = 0x29,
		.VolumeSerialNumber      = 0x12345678,
		.VolumeLabel             = "LUFA BOOT  ",
		.FilesystemIdentifier    = "FAT12   ",
		.BootstrapProgram        = {0},
		.MagicSignature          = 0xAA55,
	};

static FATDirectoryEntry_t FirmwareFileEntry =
	{
		.Filename               = "FIRMWARE",
		.Extension              = "BIN",
		.Attributes             = 0,
		.Reserved               = {0},
		.CreationTime           = FAT_TIME(1, 1, 0),
		.CreationDate           = FAT_DATE(14, 2, 1989),
		.StartingCluster        = 2,
		.FileSizeBytes          = FIRMWARE_FILE_SIZE,
	};


static void UpdateFAT12ClusterEntry(uint8_t* FATTable,
                                    const uint16_t Index,
                                    const uint16_t ChainEntry)
{
	/* Calculate the starting offset of the cluster entry in the FAT12 table */
	uint8_t FATOffset   =   (Index * 3) / 2;
	bool    UpperNibble = (((Index * 3) % 2) != 0);

	/* Check if the start of the entry is at an upper nibble of the byte, fill
	 * out FAT12 entry as required */
	if (UpperNibble)
	{
		FATTable[FATOffset]     = (FATTable[FATOffset] & 0x0F) | ((ChainEntry & 0x0F) << 4);
		FATTable[FATOffset + 1] = (ChainEntry >> 4);
	}
	else
	{
		FATTable[FATOffset]     = ChainEntry;
		FATTable[FATOffset + 1] = (FATTable[FATOffset] & 0xF0) | (ChainEntry >> 8);
	}
}

static void WriteBlock(const uint16_t BlockNumber)
{
	uint8_t BlockBuffer[SECTOR_SIZE_BYTES];

	/* Buffer the entire block to be written from the host */
	Endpoint_Read_Stream_LE(BlockBuffer, sizeof(BlockBuffer), NULL);
	Endpoint_ClearOUT();

	if ((BlockNumber >= 4) && (BlockNumber < (4 + (FIRMWARE_FILE_SIZE / SECTOR_SIZE_BYTES))))
	{
		uint32_t WriteFlashAddress = (uint32_t)(BlockNumber - 4) * SECTOR_SIZE_BYTES;

		for (uint16_t i = 0; i < SECTOR_SIZE_BYTES; i += 2)
		{
			/* Disallow writing to the bootloader section */
			if (WriteFlashAddress > BOOT_START_ADDR)
			  continue;

			if ((WriteFlashAddress % SPM_PAGESIZE) == 0)
			{
				/* Erase the given FLASH page, ready to be programmed */
				boot_page_erase(WriteFlashAddress);
				boot_spm_busy_wait();
			}

			/* Write the next data word to the FLASH page */
			boot_page_fill(WriteFlashAddress, (BlockBuffer[i + 1] << 8) | BlockBuffer[i]);
			WriteFlashAddress += 2;

			if ((WriteFlashAddress % SPM_PAGESIZE) == 0)
			{
				/* Write the filled FLASH page to memory */
				boot_page_write(WriteFlashAddress - SPM_PAGESIZE);
				boot_spm_busy_wait();
			}
		}
	}
}

static void ReadBlock(const uint16_t BlockNumber)
{
	uint8_t BlockBuffer[SECTOR_SIZE_BYTES];
	memset(BlockBuffer, 0x00, sizeof(BlockBuffer));

	switch (BlockNumber)
	{
		case 0: /* Block 0: Boot block sector */
			memcpy(BlockBuffer, &BootBlock, sizeof(FATBootBlock_t));
			break;

		case 1: /* Block 1: First FAT12 cluster chain copy */
		case 2: /* Block 2: Second FAT12 cluster chain copy */
			/* Cluster 0: Media type/Reserved */
			UpdateFAT12ClusterEntry(BlockBuffer, 0, 0xF00 | BootBlock.MediaDescriptor);

			/* Cluster 1: Reserved */
			UpdateFAT12ClusterEntry(BlockBuffer, 1, 0xFFF);

			/* Cluster 2 onwards: Cluster chain of FIRMWARE.BIN */
			for (uint16_t i = 0; i < FILE_CLUSTERS(FIRMWARE_FILE_SIZE); i++)
			  UpdateFAT12ClusterEntry(BlockBuffer, i+2, i+3);

			/* Mark last cluster as end of file */
			UpdateFAT12ClusterEntry(BlockBuffer, FILE_CLUSTERS(FIRMWARE_FILE_SIZE) + 1, 0xFFF);
			break;

		case 3: /* Block 3: Root file entries */
			memcpy(BlockBuffer, &FirmwareFileEntry, sizeof(FATDirectoryEntry_t));
			break;

		default: /* Blocks 4 onwards: Data allocation section */
			if ((BlockNumber >= 4) && (BlockNumber < (4 + (FIRMWARE_FILE_SIZE / SECTOR_SIZE_BYTES))))
			{
				uint32_t ReadFlashAddress = (uint32_t)(BlockNumber - 4) * SECTOR_SIZE_BYTES;

				for (uint16_t i = 0; i < SECTOR_SIZE_BYTES; i++)
				  BlockBuffer[i] = pgm_read_byte_far(ReadFlashAddress++);
			}

			break;
	}

	/* Write the entire read block Buffer to the host */
	Endpoint_Write_Stream_LE(BlockBuffer, sizeof(BlockBuffer), NULL);
	Endpoint_ClearIN();
}

void VirtualFAT_WriteBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
                            const uint32_t BlockAddress,
                            uint16_t TotalBlocks)
{
	uint16_t CurrentBlock = (uint16_t)BlockAddress;

	/* Emulated FAT is performed per-block, pass each requested block index
	 * to the emulated FAT block write function */
	while (TotalBlocks--)
	  WriteBlock(CurrentBlock++);
}

void VirtualFAT_ReadBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
                           const uint32_t BlockAddress,
                           uint16_t TotalBlocks)
{
	uint16_t CurrentBlock = (uint16_t)BlockAddress;

	/* Emulated FAT is performed per-block, pass each requested block index
	 * to the emulated FAT block read function */
	while (TotalBlocks--)
	  ReadBlock(CurrentBlock++);
}