use fmt;

fn do_opc(cpu: *cpu, opc: u8) void =
	if (0 <= opc && opc < op::MARK0) do_opr(cpu, opc)
	else if (op::MARK0 <= opc && opc <= op::MARK15)
		// who is mark
		do_op_mark(cpu, opc-op::MARK0)
	else if (op::LOC0 <= opc && opc <= op::LOC15)
		do_op_loc(cpu, opc-op::LOC0)
	else if (op::RET0 <= opc && opc <= op::RET15)
		do_op_ret(cpu, opc-op::RET0)
	else if (op::LIT0 <= opc && opc <= op::LIT15)
		do_op_lit(cpu, opc-op::LIT0)
	else abort("what???");

fn do_op_mark(cpu: *cpu, p: u8) void =
	cpu.rp += p*2;

fn do_op_loc(cpu: *cpu, p: u8) void =
	push(cpu, 0x100 + cpu.rp:u16 - (p-1)*2);

fn do_op_ret(cpu: *cpu, p: u8) void = {
	cpu.rp -= p*2;
	const rval = rpop(cpu);
	cpu.pc = rval;
};

fn do_op_lit(cpu: *cpu, p: u8) void = {
	push(cpu, p: u16);
};

fn do_opr(cpu: *cpu, op: u8) void = switch (op) {
	case op::NOP => yield;
	case op::ROT =>
		const a = pop(cpu);
		const b = pop(cpu);
		const c = pop(cpu);
		push(cpu, b);
		push(cpu, a);
		push(cpu, c);
	case op::NRT =>
		const a = pop(cpu);
		const b = pop(cpu);
		const c = pop(cpu);
		push(cpu, a);
		push(cpu, c);
		push(cpu, b);
	case op::DUP =>
		push(cpu, peek(cpu));
	case op::SWP =>
		const a = pop(cpu);
		const b = pop(cpu);
		push(cpu, a);
		push(cpu, b);
	case op::OVR =>
		const x = peek(cpu, 1);
		push(cpu, x);
	case op::DRP =>
		pop(cpu);
	case op::TCK =>
		const y = pop(cpu);
		const x = pop(cpu);
		push(cpu, y);
		push(cpu, x);
		push(cpu, y);
	case op::NIP =>
		const y = pop(cpu);
		pop(cpu);
		push(cpu, y);
	case op::EQU =>
		const x = pop(cpu);
		const y = pop(cpu);
		push(cpu, if (x == y) 1 else 0);
	case op::NEQ =>
		const x = pop(cpu);
		const y = pop(cpu);
		push(cpu, if (x != y) 1 else 0);
	case op::ADD =>
		const x = pop(cpu);
		const y = pop(cpu);
		push(cpu, x + y);
	case op::SUB =>
		const y = pop(cpu);
		const x = pop(cpu);
		push(cpu, x - y);
	case op::MUL =>
		// TODO: better handling mul div
		const x = pop(cpu);
		const y = pop(cpu);
		push(cpu, x * y);
	case op::DIV =>
		const y = pop(cpu);
		const x = pop(cpu);
		push(cpu, x / y);
	case op::NEG =>
		push(cpu, - pop(cpu));
	case op::SLT =>
		const x = pop(cpu): i16;
		const y = pop(cpu): i16;
		push(cpu, if (y < x) 1 else 0);
	case op::SLE =>
		const x = pop(cpu): i16;
		const y = pop(cpu): i16;
		push(cpu, if (y <= x) 1 else 0);
	case op::ULT =>
		const x = pop(cpu): u16;
		const y = pop(cpu): u16;
		push(cpu, if (y < x) 1 else 0);
	case op::ULE =>
		const x = pop(cpu): u16;
		const y = pop(cpu): u16;
		push(cpu, if (y <= x) 1 else 0);
	case op::LOD =>
		// TODO lod and sto for bytes
		const addr = pop(cpu);
		push(cpu, rmem(cpu.mem, addr));
	case op::STO =>
		const addr = pop(cpu);
		const val = pop(cpu);
		wmem(cpu.mem, addr, val);
	case op::PSH =>
		rpush(cpu, pop(cpu));
	case op::POP =>
		push(cpu, rpop(cpu));
	case op::HLT =>
		cpu.halted = true;
	case op::PUT =>
		fmt::printfln("{:_04x}",pop(cpu))!;
	case => abort("wrong opr");
};