"""Contract conformance tests (SPEC.md 0.1.x). Platform-agnostic: framebuffer

dimensions come from the PPM header, addresses use $0000, and `bank` is

exercised but banking is not required."""

import urllib.error

import urllib.request

from emu_control import parse_ppm_header

def _raw(emu, method, path):

    """Raw request returning (status_code, body) without the client's wrapping,

    so we can assert on 4xx status codes."""

    req = urllib.request.Request(emu.base + path, method=method)

    try:

        with urllib.request.urlopen(req, timeout=emu.timeout) as r:

            return r.status, r.read()

    except urllib.error.HTTPError as e:

        return e.code, e.read()

def test_status_contract(emu):

    st = emu.status()

    for k in ("contract", "emulator", "platform", "frame", "paused", "running"):

        assert k in st, f"missing /status.{k}"

    assert str(st["contract"]).split(".")[0] == "0", "unexpected contract MAJOR"

    assert isinstance(st["platform"], str) and st["platform"]

    assert isinstance(st["frame"], int)

    assert isinstance(st["paused"], bool)

def test_regs_object(emu):

    r = emu.regs()

    assert isinstance(r, dict) and r, "regs must be a non-empty JSON object"

    assert all(isinstance(v, int) for v in r.values()), "register values must be ints"

def test_mem_exact_length(emu):

    assert len(emu.mem(0x0000, 32)) == 32

    assert len(emu.mem(0x0000, 256)) == 256

    assert len(emu.mem(0x0000, 0)) == 0

def test_mem_bank_param_returns_length(emu):

    # bank is optional (ignored on flat platforms) but must still honour len.

    assert len(emu.mem(0x0000, 8, bank=0)) == 8

def test_screenshot_ppm(emu):

    data = emu.screenshot_ppm()

    w, h, maxval, off = parse_ppm_header(data)

    assert w > 0 and h > 0, f"bad dimensions {w}x{h}"

    assert maxval == 255

    assert len(data) == off + 3 * w * h, "PPM body size mismatches dimensions"

def test_step_is_deterministic(emu):

    emu.pause()

    try:

        a = emu.frame()

        b = emu.step(2); c = emu.frame()

        assert b == c, "/step must return the halted frame counter"

        d = emu.step(2); e = emu.frame()

        assert d == e

        assert c - a > 0, "/step must advance the frame counter"

        assert (c - a) == (e - c), "equal steps must advance by equal amounts"

    finally:

        emu.resume()

def test_pause_resume_toggle(emu):

    emu.pause()

    assert emu.status()["paused"] is True

    emu.resume()

    assert emu.status()["paused"] is False

def test_unknown_path_404(emu):

    code, _ = _raw(emu, "GET", "/no-such-endpoint")

    assert code == 404

def test_step_requires_post(emu):

    code, _ = _raw(emu, "GET", "/step?frames=1")

    assert code == 405