/*
 * VBMouse - Interface to some DOS int 21h services
 * 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 INT21DOS_H
#define INT21DOS_H

#include <stddef.h>
#include <stdbool.h>
#include <stdint.h>
#include <dos.h>
#include "sassert.h"

#define DOS_PSP_SIZE 256

enum dos_error {
	DOS_ERROR_SUCCESS = 0,
	DOS_ERROR_INVALID_FUNCTION = 1,
	DOS_ERROR_FILE_NOT_FOUND = 2,
	DOS_ERROR_PATH_NOT_FOUND = 3,
	DOS_ERROR_TOO_MANY_OPEN_FILES = 4,
	DOS_ERROR_ACCESS_DENIED = 5,
	DOS_ERROR_INVALID_HANDLE = 6,
	DOS_ERROR_ARENA_TRASHED = 7,
	DOS_ERROR_NOT_ENOUGH_MEMORY = 8,
	DOS_ERROR_INVALID_BLOCK = 9,
	DOS_ERROR_BAD_ENVIRONMENT = 10,
	DOS_ERROR_BAD_FORMAT = 11,
	DOS_ERROR_INVALID_ACCESS = 12,
	DOS_ERROR_INVALID_DATA = 13,
	DOS_ERROR_OUT_OF_MEMORY = 14,
	DOS_ERROR_INVALID_DRIVE = 15,
	DOS_ERROR_CURRENT_DIRECTORY = 16,
	DOS_ERROR_NOT_SAME_DEVICE = 17,
	DOS_ERROR_NO_MORE_FILES = 18,
	DOS_ERROR_WRITE_PROTECT = 19,
	DOS_ERROR_BAD_UNIT = 20,
	DOS_ERROR_NOT_READY = 21,
	DOS_ERROR_BAD_COMMAND = 22,
	DOS_ERROR_CRC = 23,
	DOS_ERROR_BAD_LENGTH = 24,
	DOS_ERROR_SEEK = 25,
	DOS_ERROR_NOT_DOS_DISK = 26,
	DOS_ERROR_SECTOR_NOT_FOUND = 27,

	DOS_ERROR_GEN_FAILURE = 31,

	DOS_ERROR_HANDLE_EOF = 38,
	DOS_ERROR_HANDLE_DISK_FULL = 39,

	DOS_ERROR_FILE_EXISTS = 80,
	DOS_ERROR_CANNOT_MAKE = 82,
};

// General functions

static inline void dos_print_char(char c);
#pragma aux dos_print_char = \
	"mov ah, 0x02" \
	"int 0x21" \
	__parm [dl] \
	__modify [ah]

static inline uint8_t dos_read_char(void);
#pragma aux dos_read_char = \
	"mov ah, 0x08" \
	"int 0x21" \
	__value [al] \
	__modify [ax]

static inline void dos_print_string(const char *s);
#pragma aux dos_print_string = \
	"mov ah, 0x09" \
	"int 0x21" \
	__parm [dx] \
	__modify [ah]

static inline uint16_t dos_get_version(void);
#pragma aux dos_get_version = \
	"mov ah, 0x30" \
	"int 0x21" \
	__value [ax] \
	__modify [bx cx]

// Memory manipulation functions

typedef __segment segment_t;

enum dos_allocation_strategy {
	DOS_FIT_FIRST    = 0,
	DOS_FIT_BEST     = 1,
	DOS_FIT_LAST     = 2,

	DOS_FIT_HIGH     = 0x80,
	DOS_FIT_HIGHONLY = 0x40,
};

/** Converts bytes to paragraphs (16 bytes), rounding up. */
static inline unsigned get_paragraphs(unsigned bytes)
{
	return (bytes + 15) / 16;
}

static unsigned dos_query_allocation_strategy(void);
#pragma aux dos_query_allocation_strategy = \
	"mov ax, 0x5800" \
	"int 0x21" \
	__value [ax]

static int dos_set_allocation_strategy(unsigned strategy);
#pragma aux dos_set_allocation_strategy = \
	"clc" \
	"mov ax, 0x5801" \
	"int 0x21" \
	"jc end" \
	"mov ax, 0" \
	"end:" \
	__parm [bx] \
	__value [ax]

static bool dos_query_umb_link_state(void);
#pragma aux dos_query_umb_link_state = \
	"mov ax, 0x5802" \
	"int 0x21" \
	__value [al]

static int dos_set_umb_link_state(bool state);
#pragma aux dos_set_umb_link_state = \
	"clc" \
	"mov ax, 0x5803" \
	"int 0x21" \
	"jc end" \
	"mov ax, 0" \
	"end:" \
	__parm [bx] \
	__value [ax]

/** Allocates a new DOS segment.
 *  @returns either the allocated segment or 0 if any error. */
static __segment dos_alloc(unsigned paragraphs);
#pragma aux dos_alloc = \
	"clc" \
	"mov ah, 0x48" \
	"int 0x21" \
	"jnc end" \
	"mov ax, 0xB" \
	"end:" \
	__parm [bx] \
	__value [ax]

/** Frees DOS segment. */
static void dos_free(segment_t segment);
#pragma aux dos_free = \
	"mov ah, 0x49" \
	"int 0x21" \
	__parm [es] \
	__modify [ax]

/** Sets a given PSP as the current active process. */
static void dos_set_psp(segment_t psp);
#pragma aux dos_set_psp = \
	"mov ah, 0x50" \
	"int 0x21" \
	__parm [bx] \
	__modify [ax]

#endif // INT21DOS_H