/*
 * VBSF - VirtualBox shared folders for DOS, resident interface
 * Copyright (C) 2022 Javier S. Pedro
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#ifndef SFTSR_H
#define SFTSR_H

#include <stdbool.h>
#include <stdint.h>

#include "vbox.h"
#include "int21dos.h"

/** Trace all int2F calls into dlog */
#define TRACE_CALLS   0

#define LASTDRIVE     'Z'
#define NUM_DRIVES    ((LASTDRIVE - 'A') + 1)

/** Maximum number of open files and open directories (being enumerated). */
#define NUM_FILES     60

/** Parameters used for returning disk geometry.
 *  For compatibility, better if sector_per_cluster * bytes_per_sector <= 32K. */
#define SECTORS_PER_CLUSTER      8
#define BYTES_PER_SECTOR         4096
#define BYTES_PER_CLUSTER        (SECTORS_PER_CLUSTER * BYTES_PER_SECTOR)

/** Parameters for LFN names with hash (i.e. XXXX~HHH.XXX). */
#define DEF_HASH_CHARS 3
#define MIN_HASH_CHARS 2
#define MAX_HASH_CHARS 6

/** Size of the VBox buffer. The maximum message length that may be sent.
 *  Enough to fit an HGCM connect call, which is actually larger than the other calls we use ( <= 7 args ).  */
#define VBOX_BUFFER_SIZE (200)

#define INVALID_OPENFILE (-1)

/** Options available for each mounted shared folder. */
typedef struct {
	/** Number of characters to use for the hash part of generated SFNs (between MIN_HASH_CHARS and MAX_HASH_CHARS). */
	uint8_t hash_chars : 3;
	/** Use short filenames provided by host. */
	bool use_host_sfn : 1 ;
	/** Generate (hash-based) short filenames. If false, files with LFN will not appear. */
	bool generate_sfn : 1;
	/** Generate hash SFNs for any filename with non-uppercase chars, even if otherwise fits in 8.3. */
	bool require_uppercase : 1;
} MOUNTOPTS;

/** Struct representing a (potentially) mounted drive. */
typedef struct {
	/** VirtualBox "root" for this drive, or NIL if unmounted. */
	uint32_t root;
	/** Mount options. */
	MOUNTOPTS opt;
} MOUNTEDDRIVE;

/** Struct representing a (potentially) open file. */
typedef struct {
	uint32_t root;
	uint64_t handle;
} OPENFILE;
// TODO: Technically we could reduce the size of the above struct to save a bit of mem
// In the current implementation the max handle virtualbox can give is < 4K,
// but we still waste a full uint64_t to store a value that is always < 4K.
// Similarly, at most 64 roots are supported, but we waste a uint32_t.

typedef struct {
	// TSR installation data
	/** Previous int2f ISR, storing it for uninstall. */
	void (__interrupt __far *prev_int2f_handler)();
	/** Stored pointer for the DOS SDA. */
	DOSSDA __far *dossda;

	// TSR configuration
	/** Offset (in seconds/2) of the current timezone.
	 *  As per tradition, a negative offset means east of GMT; while positive means west. */
	int32_t tz_offset;
	/** NLS support tables. */
	uint8_t __far *file_upper_case;
	FCHAR __far *file_char;
	/** Codepage to unicode lookup table. */
	uint16_t unicode_table[128];

	// Current status
	/** Array of all possible DOS drives. */
	MOUNTEDDRIVE drives[NUM_DRIVES];

	/** All currently open files. */
	OPENFILE files[NUM_FILES];

	// VirtualBox communication
	struct vboxcomm vb;
	char vbbuf[VBOX_BUFFER_SIZE];
	uint32_t hgcm_client_id;
} TSRDATA;

typedef TSRDATA * PTSRDATA;
typedef TSRDATA __far * LPTSRDATA;

extern void __declspec(naked) __far int2f_isr(void);

extern LPTSRDATA __far get_tsr_data(bool installed);

/** This symbol is always at the end of the TSR segment */
extern int resident_end;

/** This is not just data, but the entire segment. */
static inline unsigned get_resident_size(void)
{
	return FP_OFF(&resident_end);
}

#endif // SFTSR_H