#include "uxn.h"

/*
Copyright (u) 2022-2024 Devine Lu Linvega, Andrew Alderwick, Andrew Richards

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE.
*/

#define FLP { s = ins & 0x40 ? &uxn.wst : &uxn.rst; }
#define JMP(x) { if(m2) pc = (x); else pc += (Sint8)(x); }
#define PO1(o) { o = s->dat[--*sp]; }
#define PO2(o) { o = s->dat[--*sp] | (s->dat[--*sp] << 8); }
#define POx(o) { if(m2) { PO2(o) } else PO1(o) }
#define PU1(y) { s->dat[s->ptr++] = (y); }
#define PU2(y) { tt = (y); s->dat[s->ptr++] = tt >> 0x8; s->dat[s->ptr++] = tt; }
#define PUx(y) { if(m2) { PU2(y) } else PU1(y) }
#define PEK(o, x, r) { if(m2) { r = (x); o = uxn.ram[r++] << 8 | uxn.ram[r]; } else o = uxn.ram[(x)]; }
#define POK(x, y, r) { if(m2) { r = (x); uxn.ram[r++] = y >> 8; uxn.ram[r] = y; } else uxn.ram[(x)] = (y); }
#define DEI(o, p) { if(m2) { o = (emu_dei(p) << 8) | emu_dei(p + 1); } else o = emu_dei(p); }
#define DEO(p, y) { if(m2) { emu_deo(p, y >> 8); emu_deo(p + 1, y); } else emu_deo(p, y); }

#define OPC(op, body) { \
	case 0x00|0x00|0x00|op: {m2 = 0, s = &uxn.wst, sp = &s->ptr; body break;}\
	case 0x00|0x00|0x20|op: {m2 = 1, s = &uxn.wst, sp = &s->ptr; body break;}\
	case 0x00|0x40|0x00|op: {m2 = 0, s = &uxn.rst, sp = &s->ptr; body break;}\
	case 0x00|0x40|0x20|op: {m2 = 1, s = &uxn.rst, sp = &s->ptr; body break;}\
	case 0x80|0x00|0x00|op: {m2 = 0, s = &uxn.wst, kp = s->ptr, sp = &kp; body break;}\
	case 0x80|0x00|0x20|op: {m2 = 1, s = &uxn.wst, kp = s->ptr, sp = &kp; body break;}\
	case 0x80|0x40|0x00|op: {m2 = 0, s = &uxn.rst, kp = s->ptr, sp = &kp; body break;}\
	case 0x80|0x40|0x20|op: {m2 = 1, s = &uxn.rst, kp = s->ptr, sp = &kp; body break;}\
}

int
uxn_eval(Uint16 pc)
{
	if(!pc || uxn.dev[0x0f]) return 0;
	for(;;) {
		Uint16 tt, a, b, c;
		Uint8 t, kp, *sp, ins = uxn.ram[pc++];
		int m2 = 0;
		Stack *s;
		switch(ins) {
		/* BRK */ case 0x00: return 1;
		/* JCI */ case 0x20: if(uxn.wst.dat[--uxn.wst.ptr]) goto JMI; pc += 2; break;
		/* JMI */ case 0x40: JMI: a = uxn.ram[pc++] << 8 | uxn.ram[pc++]; pc += a; break;
		/* JSI */ case 0x60: tt = pc + 2; uxn.rst.dat[uxn.rst.ptr++] = tt >> 8; uxn.rst.dat[uxn.rst.ptr++] = tt; goto JMI;
		/* LIT2  */ case 0xa0: uxn.wst.dat[uxn.wst.ptr++] = uxn.ram[pc++], uxn.wst.dat[uxn.wst.ptr++] = uxn.ram[pc++]; break;
		/* LIT2r */ case 0xe0: uxn.rst.dat[uxn.rst.ptr++] = uxn.ram[pc++], uxn.rst.dat[uxn.rst.ptr++] = uxn.ram[pc++]; break;
		/* LIT   */ case 0x80: uxn.wst.dat[uxn.wst.ptr++] = uxn.ram[pc++]; break;
		/* LITr  */ case 0xc0: uxn.rst.dat[uxn.rst.ptr++] = uxn.ram[pc++]; break;
		/* INC */ OPC(0x01, POx(a) PUx(a + 1))
		/* POP */ OPC(0x02, POx(a))
		/* NIP */ OPC(0x03, POx(a) POx(b) PUx(a))
		/* SWP */ OPC(0x04, POx(a) POx(b) PUx(a) PUx(b))
		/* ROT */ OPC(0x05, POx(a) POx(b) POx(c) PUx(b) PUx(a) PUx(c))
		/* DUP */ OPC(0x06, POx(a) PUx(a) PUx(a))
		/* OVR */ OPC(0x07, POx(a) POx(b) PUx(b) PUx(a) PUx(b))
		/* EQU */ OPC(0x08, POx(a) POx(b) PU1(b == a))
		/* NEQ */ OPC(0x09, POx(a) POx(b) PU1(b != a))
		/* GTH */ OPC(0x0a, POx(a) POx(b) PU1(b > a))
		/* LTH */ OPC(0x0b, POx(a) POx(b) PU1(b < a))
		/* JMP */ OPC(0x0c, POx(a) JMP(a))
		/* JCN */ OPC(0x0d, POx(a) PO1(b) if(b) JMP(a))
		/* JSR */ OPC(0x0e, POx(a) FLP PU2(pc) JMP(a))
		/* STH */ OPC(0x0f, POx(a) FLP PUx(a))
		/* LDZ */ OPC(0x10, PO1(a) PEK(b, a, t) PUx(b))
		/* STZ */ OPC(0x11, PO1(a) POx(b) POK(a, b, t))
		/* LDR */ OPC(0x12, PO1(a) PEK(b, pc + (Sint8)a, tt) PUx(b))
		/* STR */ OPC(0x13, PO1(a) POx(b) POK(pc + (Sint8)a, b, tt))
		/* LDA */ OPC(0x14, PO2(a) PEK(b, a, tt) PUx(b))
		/* STA */ OPC(0x15, PO2(a) POx(b) POK(a, b, tt))
		/* DEI */ OPC(0x16, PO1(a) DEI(b, a) PUx(b))
		/* DEO */ OPC(0x17, PO1(a) POx(b) DEO(a, b))
		/* ADD */ OPC(0x18, POx(a) POx(b) PUx(b + a))
		/* SUB */ OPC(0x19, POx(a) POx(b) PUx(b - a))
		/* MUL */ OPC(0x1a, POx(a) POx(b) PUx(b * a))
		/* DIV */ OPC(0x1b, POx(a) POx(b) PUx(a ? b / a : 0))
		/* AND */ OPC(0x1c, POx(a) POx(b) PUx(b & a))
		/* ORA */ OPC(0x1d, POx(a) POx(b) PUx(b | a))
		/* EOR */ OPC(0x1e, POx(a) POx(b) PUx(b ^ a))
		/* SFT */ OPC(0x1f, PO1(a) POx(b) PUx(b >> (a & 0xf) << (a >> 4)))
		}
	}
}