/*
 * A very simple 16-bit TSR (POP-UP) calculator, featuring automatic entry
 * of last result into DOS applications. This feature works only on AT or
 * higher class machines with a recent BIOS.
 * 
 * Use 'calc' with no operands for NON-TSR operation.
 * 
 * If HOTKEYS are specified on the command line, CALC will install
 * itself as a TSR (Ram-Resident) program, which can be invoked at
 * any time by pressing the HOTKEYS. Available HOTKEYS are:
 * 		L - Left SHIFT
 * 		R - Right SHIFT
 * 		A - ALT
 * 		C - CONTROL
 * 		S - SysRq (Caution: some systems may not like this one)
 * 
 * 	eg: CALC LR	(Install with LEFT+RIGHT SHIFT for hotkeys)
 * 
 * Keys used:
 * 	+		Addition
 * 	-		Subtraction
 * 	*		Multiply
 * 	/		Divide
 * 	%		Modulus
 * 	&		Bitwise AND
 * 	|		Bitwise OR
 * 	^		Bitwise EXCLUSIVE OR
 * 	<		Shift left
 * 	>		Shift right
 * 	=		Display result
 * 	0-9		Decimal input digits
 * 	A-F		Hexidecimal input digits
 * 	'c		Enter a single ASCII character value
 * 	"cc		Enter a dual ASCII character value
 * 	K		Clear display
 * 	R		Read value from memory
 * 	S		Store value in memory
 * 	BKSP	Clear last digit
 * 	SPACE	Toggle HEX/DECIMAL
 * 	ESC		Exit, no entry
 * 	ENTER	Exit, enter value to DOS application (works only on AT or higher)
 * 	UP		Move display up
 * 	DOWN	Move display down
 * 	RIGHT	Move display right
 * 	LEFT	Move display left
 *
 * Copyright 1990-1995 Dave Dunfield
 * All rights reserved.
 *
 * Permission granted for personal (non-commercial) use only.
 *
 * Compile command: cc calc -fop
 */
#include <stdio.h>
#include <window.h>
#include <tsr.h>

	int x=33, y=10, acc = 0, acc1, memory = 0;
	char op, mode = 0;

	/* Scan codes for entered digit values */
	char scans[] = {
		0x0B, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
		0x09, 0x0A, 0x1E, 0x30, 0x2E, 0x20, 0x12, 0x21 };

/*
 * Main calculator program
 */
calc()
{
	char c, buffer[7];

	op = acc ? '=' : ' ';		/* Use '=' reset mode if value left over */

redraw:
	wopen(x, y, 9, 4, (WSAVE|WBOX2|WCOPEN|WSCROLL)+REVERSE);
	wcursor_off();
	for(;;) {
		wprintf(mode ? "\r%c $%04x" : "\r%c%6d", op, acc);
		switch(c = toupper(wgetc())) {
			case '+' :		/* Record all operators */
			case '-' :
			case '*' :
			case '/' :
			case '%' :
			case '&' :
			case '|' :
			case '^' :
			case '<' :
			case '>' :
				doeval();
				wprintf(mode ? "\r  $%04x\n" : "\r %6d\n", acc1);
				acc = 0;
				op = c;
				break;
			case '=' :		/* Display partial result */
				doeval();
				wclwin();
				acc = acc1;
				op = '=';
				break;
			case '\'' :		/* Single ASCII character */
				acc = wgetc();
				break;
			case '"' :		/* Double ASCII character */
				acc = (wgetc() << 8) | wgetc();
				break;
			case _KBS :		/* Delete last entered digit */
				acc /= mode ? 16 : 10;
				break;
			case _KUA :		/* Move display up */
				if(y) --y;
				goto move;
			case _KDA :		/* Move display down */
				if(y < 21) ++y;
				goto move;
			case _KLA :		/* Move display left */
				if(x) --x;
				goto move;
			case _KRA :		/* Move display right */
				if(x < 71)
					++x;
			move:
				wclose();
				goto redraw;
			case ' ' :		/* Toggle hex/decmal mode */
				mode = !mode;
				break;
			case '\n' :		/* Exit and enter value */
				doeval();
				sprintf(buffer, mode ? "%x" : "%d", acc = acc1);
				for(acc1 = 0; c = buffer[acc1]; ++acc1)
					pushkey(c, scans[c]);
				wclose();
				return;
			case '\x1B' :	/* Exit and don't enter value */
				doeval();
				acc = acc1;
				wclose();
				return;
			case 'K' :		/* Clear the calculator display */
				acc = acc1 = 0;
				op = ' ';
				break;
			case 'S' :		/* Save to memory */
				memory = acc;
				break;
			case 'R' :		/* Restore from memory */
				acc = memory;
				break;
			default:
				if(op == '=') {		/* Previous result to clear */
					acc = acc1 = 0;
					op = ' '; }
				if(mode) {				/* Hex input */
					if(isdigit(c))
						acc = (acc * 16) + (c - '0');
					else if((c >= 'A') && (c <= 'F'))
						acc = (acc * 16) + (c - ('A'-10)); }
				else if(isdigit(c))		/* Decimal input */
					acc = (acc * 10) + (c - '0'); } }
}

/*
 * Evaluate the last recorded operation
 */
doeval()
{
	switch(op) {
		case '+' : acc1 += acc; break;
		case '-' : acc1 -= acc; break;
		case '*' : acc1 *= acc; break;
		case '/' : if(!acc) goto dbz; acc1 /= acc; break;
		case '%' : if(!acc) goto dbz; acc1 %= acc; break;
		case '&' : acc1 &= acc; break;
		case '|' : acc1 |= acc; break;
		case '^' : acc1 ^= acc; break;
		case '<' : acc1 <<=acc; break;
		case '>' : acc1 >>=acc; break;
		default  : acc1 = acc; break;
		dbz: wprintf("\n? / 0\nError"); wgetc(); }
}

/*
 * Shove a key (char & scancode) into the BIOS keyboard buffer
 */
pushkey(c, s) asm
{
		MOV		CH,4[BP]		; Get Scan code
		MOV		CL,6[BP]		; Get character
		MOV		AH,05h			; Push key...
		INT		16h				; Ask BIOS
}

/*
 * Main program, either TSR or execute main tty program menu
 */
main(int argc, char *argv[])
{
	int hot_keys;
	char *ptr;

/* If RAM-resident, print startup message & TSR */
	if(argc > 1) {
		fputs("POP-UP Calculator\n\nCopyright 1990-1995 Dave Dunfield\nAll rights reserved.", stderr);
		hot_keys = 0;
		ptr = argv[1];
		while(*ptr) switch(toupper(*ptr++)) {
			case 'A' : hot_keys |= ALT;		break;
			case 'C' : hot_keys |= CONTROL;	break;
			case 'L' : hot_keys |= L_SHIFT;	break;
			case 'R' : hot_keys |= R_SHIFT; break;
			case 'S' : hot_keys |= SYS_REQ;	break;
			default: abort("\n\nInvalid HOTKEY"); }
		tsr(&calc, hot_keys, 2000); }

/* Not RAM-resident, execute the program */
	calc();
}