#include "vm.h"
#include <stdio.h>

#define MAX_EXTERNAL_CALLS	256
#define MAX_DATA_STACK		256
#define MAX_CALL_STACK		256

typedef unsigned char byte;
typedef unsigned short word;

enum OPS {
	OP_NOP = 0,
	OP_PUSH,
	OP_POP,
	OP_DUP,
	OP_SWAP,

	OP_LOAD,
	OP_LOADI,
	OP_STORE,
	OP_STOREI,

	OP_LOADXY,
	OP_STOREXY,
	OP_SETX,
	OP_SETY,
	OP_SETZ,
	OP_GETY,
	OP_GETZ,
	OP_INCX,
	OP_DECX,
	OP_INCY,
	OP_DECY,
	OP_INCZ,
	OP_DECZ,

	OP_JMP,
	OP_JNT,
	OP_JTR,
	OP_JSR,
	OP_RET,
	OP_CALL,

	OP_RJ,
	OP_RB,
	OP_RJZ,
	OP_RJN,
	OP_RBZ,
	OP_RBN,

	OP_RJYZ,
	OP_RJYN,
	OP_RBYZ,
	OP_RBYN,
	OP_RJZZ,
	OP_RJZN,
	OP_RBZZ,
	OP_RBZN,

	OP_ADD,
	OP_SUB,
	OP_MUL,
	OP_DIV,
	OP_MOD,
	OP_AND,
	OP_OR,
	OP_NOT,
	OP_NEG,
	OP_INC,
	OP_DEC,
	OP_CONCAT,

	OP_EQ,
	OP_NEQ,
	OP_LT,
	OP_GT,
	OP_LEQ,
	OP_GEQ,

	OP_IN,
	OP_OUT,
	OP_SLEEP,
};

typedef void(*t_extcall)(t_stack&);
t_extcall external_calls[MAX_EXTERNAL_CALLS];
int numcallbacks = 0;

typedef void(*t_out_port)(const byte&);
typedef byte(*t_in_port)();
t_out_port out_ports[256];
t_in_port in_ports[256];

unsigned char mem[65536];
const unsigned char* vm_program = mem;
int vm_pc = 2;
int vm_cycles = 0;
t_stack vm_datastack;
t_stack vm_callstack;
unsigned short rX = 0;
unsigned char rY = 0;
unsigned char rZ = 0;
bool sleeping = false;


static void load_rom() {
	FILE *f = fopen("rom.bin", "rb");
	fseek(f, 0, SEEK_END);
	long fsize = ftell(f);
	fseek(f, 0, SEEK_SET);
	fread(&mem[0x8000], fsize, 1, f);
	fclose(f);
}

static void load_program(const char* filename) {
	FILE *f = fopen(filename, "rb");
	fseek(f, 0, SEEK_END);
	long fsize = ftell(f);
	fseek(f, 0, SEEK_SET);
	fread(mem, fsize, 1, f);
	fclose(f);
}

void vm_init(const char* filename) {
	vm_pc = 2; rX = rY = rZ = 0;
	vm_datastack.data = &mem[0x8800];
	vm_callstack.data = &mem[0x8900];
	vm_datastack.top = vm_callstack.top = 0;
	vm_datastack.max = MAX_DATA_STACK;
	vm_callstack.max = MAX_CALL_STACK;
	load_rom();
	load_program(filename);
}

inline unsigned short WORD() { vm_pc += 2; return vm_program[vm_pc - 2] + (vm_program[vm_pc - 1] << 8); }

const int vm_step() {
	if (sleeping) return vm_cycles;

	char val, val2;
	OPS opcode = (OPS)vm_program[vm_pc++];

	switch (opcode) {

	case OP_NOP: vm_cycles++; break;
	case OP_PUSH: stack_push(vm_datastack, vm_program[vm_pc++]); vm_cycles++; break;
	case OP_POP: stack_pop(vm_datastack); vm_cycles++; break;
	case OP_DUP: stack_push(vm_datastack, stack_peek(vm_datastack)); vm_cycles++; break;
	case OP_SWAP: val = stack_pop(vm_datastack); val2 = stack_pop(vm_datastack); stack_push(vm_datastack, val); stack_push(vm_datastack, val2); vm_cycles++; break;
	case OP_LOAD: stack_push(vm_datastack, mem[WORD()]); vm_cycles++; break;
	case OP_LOADI: stack_push(vm_datastack, mem[WORD() + rY]); vm_cycles++; break;
	case OP_STORE: mem[WORD()] = stack_pop(vm_datastack); vm_cycles++; break;
	case OP_STOREI: val = stack_pop(vm_datastack); mem[WORD() + rY] = val; vm_cycles++; break;
	case OP_LOADXY: stack_push(vm_datastack, mem[rX + rY]); vm_cycles++; break;
	case OP_STOREXY: mem[rX + rY] = stack_pop(vm_datastack); vm_cycles++; break;
	case OP_SETX: rX = WORD(); vm_cycles++; break;
	case OP_SETY: rY = stack_pop(vm_datastack); vm_cycles++; break;
	case OP_SETZ: rZ = stack_pop(vm_datastack); vm_cycles++; break;
	case OP_GETY: stack_push(vm_datastack, rY); vm_cycles++; break;
	case OP_GETZ: stack_push(vm_datastack, rZ); vm_cycles++; break;
	case OP_INCX: rX++; vm_cycles++; break;
	case OP_DECX: rX--; vm_cycles++; break;
	case OP_INCY: rY++; vm_cycles++; break;
	case OP_DECY: rY--; vm_cycles++; break;
	case OP_INCZ: rZ++; vm_cycles++; break;
	case OP_DECZ: rZ--; vm_cycles++; break;
	case OP_JMP: vm_pc = WORD(); vm_cycles++; break;
	case OP_JNT: if (stack_pop(vm_datastack) == 0) { vm_pc = WORD(); } else vm_pc+=2; vm_cycles++; break;
	case OP_JTR: if (stack_pop(vm_datastack) != 0) { vm_pc = WORD(); } else vm_pc+=2; vm_cycles++; break;
	case OP_JSR: stack_push(vm_callstack, vm_pc + 2); stack_push(vm_callstack, rX & 255); stack_push(vm_callstack, rX >> 8); stack_push(vm_callstack, rY); stack_push(vm_callstack, rZ); vm_pc = WORD(); vm_cycles++; break;
	case OP_RET: rZ = stack_pop(vm_callstack); rY = stack_pop(vm_callstack); rX = (stack_pop(vm_callstack) << 8) + stack_pop(vm_callstack); vm_pc = stack_pop(vm_callstack); vm_cycles++; break;
	case OP_CALL: external_calls[vm_program[vm_pc++]](vm_datastack); vm_cycles++; break;
	case OP_RJ: vm_pc += vm_program[vm_pc]; vm_cycles++; break;
	case OP_RB: vm_pc -= vm_program[vm_pc]+1; vm_cycles++; break;
	case OP_RJZ: if (stack_pop(vm_datastack) == 0) vm_pc += vm_program[vm_pc]; else vm_pc++; vm_cycles++; break;
	case OP_RJN: if (stack_pop(vm_datastack) != 0) vm_pc += vm_program[vm_pc]; else vm_pc++; vm_cycles++; break;
	case OP_RBZ: if (stack_pop(vm_datastack) == 0) vm_pc -= vm_program[vm_pc] + 1; else vm_pc++; vm_cycles++; break;
	case OP_RBN: if (stack_pop(vm_datastack) != 0) vm_pc -= vm_program[vm_pc] + 1; else vm_pc++; vm_cycles++; break;
	case OP_RJYZ: if (rY == 0) vm_pc += vm_program[vm_pc]; else vm_pc++; vm_cycles++; break;
	case OP_RJYN: if (rY != 0) vm_pc += vm_program[vm_pc]; else vm_pc++; vm_cycles++; break;
	case OP_RBYZ: if (rY == 0) vm_pc -= vm_program[vm_pc] + 1; else vm_pc++; vm_cycles++; break;
	case OP_RBYN: if (rY != 0) vm_pc -= vm_program[vm_pc] + 1; else vm_pc++; vm_cycles++; break;
	case OP_RJZZ: if (rZ == 0) vm_pc += vm_program[vm_pc]; else vm_pc++; vm_cycles++; break;
	case OP_RJZN: if (rZ != 0) vm_pc += vm_program[vm_pc]; else vm_pc++; vm_cycles++; break;
	case OP_RBZZ: if (rZ == 0) vm_pc -= vm_program[vm_pc] + 1; else vm_pc++; vm_cycles++; break;
	case OP_RBZN: if (rZ != 0) vm_pc -= vm_program[vm_pc] + 1; else vm_pc++; vm_cycles++; break;
	case OP_ADD: stack_push(vm_datastack, stack_pop(vm_datastack) + stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_SUB: stack_push(vm_datastack, stack_pop(vm_datastack) - stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_MUL: stack_push(vm_datastack, stack_pop(vm_datastack) * stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_DIV: stack_push(vm_datastack, stack_pop(vm_datastack) / stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_MOD: stack_push(vm_datastack, stack_pop(vm_datastack) % stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_AND: stack_push(vm_datastack, stack_pop(vm_datastack) & stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_OR: stack_push(vm_datastack, stack_pop(vm_datastack) | stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_NOT: stack_push(vm_datastack, !stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_NEG: stack_push(vm_datastack, -stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_INC: stack_push(vm_datastack, stack_pop(vm_datastack)+1); vm_cycles++; break;
	case OP_DEC: stack_push(vm_datastack, stack_pop(vm_datastack) - 1); vm_cycles++; break;
	case OP_CONCAT:
		val = stack_pop(vm_datastack);
		for (int i = 0; i < val; i++) stack_push(vm_callstack, stack_pop(vm_datastack));
		val2 = stack_pop(vm_datastack);
		for (int i = 0; i < val; i++) stack_push(vm_datastack, stack_pop(vm_callstack));
		stack_push(vm_datastack, val + val2);
		vm_cycles++; break;
	case OP_EQ: stack_push(vm_datastack, stack_pop(vm_datastack) == stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_NEQ: stack_push(vm_datastack, stack_pop(vm_datastack) != stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_LT: stack_push(vm_datastack, stack_pop(vm_datastack) < stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_GT: stack_push(vm_datastack, stack_pop(vm_datastack) > stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_LEQ: stack_push(vm_datastack, stack_pop(vm_datastack) <= stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_GEQ: stack_push(vm_datastack, stack_pop(vm_datastack) >= stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_IN: stack_push(vm_datastack, in_ports[vm_program[vm_pc++]]()); vm_cycles++; break;
	case OP_OUT: out_ports[vm_program[vm_pc++]](stack_pop(vm_datastack)); vm_cycles++; break;
	case OP_SLEEP: sleeping = true; vm_cycles++; break;
	}
	return vm_cycles;
}

void vm_register_call(void(*callback)(t_stack&)) {
	external_calls[numcallbacks++] = callback;
}

void vm_register_in_port(const byte port, t_in_port callback) {
	in_ports[port] = callback;
}

void vm_register_out_port(const byte port, t_out_port callback) {
	out_ports[port] = callback;
}

void vm_call_interrupt(const char num) {
	sleeping = false;
	stack_push(vm_callstack, vm_pc);
	stack_push(vm_callstack, rX & 255);
	stack_push(vm_callstack, rX >> 8);
	stack_push(vm_callstack, rY);
	stack_push(vm_callstack, rZ);
	vm_pc = num == 0 ? 0xFFFA : 0xFFFD;
	vm_cycles++;
}