"""emu_control.py — shared client for the Retro Remote Debug Controller.

One client for every port's pytest suite. Speaks the HTTP contract in

../SPEC.md (0.1.x). Depends only on the stdlib; Pillow is optional and only

needed for .screenshot().

    from emu_control import EmuControl

    emu = EmuControl(port=8080)      # emulator started with -controlport 8080

    emu.wait_ready()

    emu.step(frames=120)

    assert emu.regs()["a"] == 0

    data = emu.mem(0x0400, 256, bank=1)

    img = emu.screenshot()           # PIL.Image (requires Pillow)

"""

from __future__ import annotations

import io

import json

import time

import urllib.error

import urllib.parse

import urllib.request

CONTRACT_MAJOR = 0

class EmuControlError(RuntimeError):

    pass

def parse_ppm_header(data: bytes):

    """Parse a binary PPM (P6) header. Returns (width, height, maxval, offset)

    where offset is the index of the first pixel byte. Raises on malformed

    input. Stdlib-only — no Pillow needed."""

    if data[:2] != b"P6":

        raise EmuControlError(f"not a P6 PPM (magic {data[:2]!r})")

    fields, i, n = [], 2, len(data)

    while len(fields) < 3 and i < n:

        while i < n and data[i:i + 1].isspace():

            i += 1

        if i < n and data[i:i + 1] == b"#":            # comment to end of line

            while i < n and data[i:i + 1] not in (b"\n", b"\r"):

                i += 1

            continue

        start = i

        while i < n and not data[i:i + 1].isspace():

            i += 1

        fields.append(int(data[start:i]))

    if len(fields) < 3:

        raise EmuControlError("truncated PPM header")

    return fields[0], fields[1], fields[2], i + 1        # +1: single whitespace

class EmuControl:

    def __init__(self, port: int, host: str = "127.0.0.1", timeout: float = 5.0):

        self.base = f"http://{host}:{port}"

        self.timeout = timeout

    # -- transport ---------------------------------------------------------

    def _get(self, path: str) -> tuple[bytes, str]:

        try:

            with urllib.request.urlopen(self.base + path, timeout=self.timeout) as r:

                return r.read(), r.headers.get_content_type()

        except urllib.error.HTTPError as e:

            raise EmuControlError(f"GET {path} -> {e.code}: {e.read()!r}") from e

    def _post(self, path: str) -> bytes:

        req = urllib.request.Request(self.base + path, method="POST", data=b"")

        try:

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

                return r.read()

        except urllib.error.HTTPError as e:

            raise EmuControlError(f"POST {path} -> {e.code}: {e.read()!r}") from e

    # -- endpoints ---------------------------------------------------------

    def status(self) -> dict:

        body, _ = self._get("/status")

        st = json.loads(body)

        major = int(str(st.get("contract", "0")).split(".")[0])

        if major != CONTRACT_MAJOR:

            raise EmuControlError(

                f"contract major mismatch: emulator {st.get('contract')} "

                f"vs client {CONTRACT_MAJOR}.x"

            )

        return st

    def frame(self) -> int:

        return int(self.status()["frame"])

    def regs(self) -> dict:

        body, _ = self._get("/regs")

        return json.loads(body)

    def mem(self, addr: int, length: int, bank: int | None = None) -> bytes:

        path = f"/mem?addr={addr}&len={length}"

        if bank is not None:

            path += f"&bank={bank}"

        body, _ = self._get(path)

        return body

    def step(self, frames: int = 1) -> int:

        body = self._post(f"/step?frames={frames}")

        return int(json.loads(body)["frame"])

    def pause(self) -> None:

        self._post("/pause")

    def resume(self) -> None:

        self._post("/resume")

    def key(self, text: str | None = None, code: int | None = None,

            down: bool | None = None) -> None:

        """Inject a key (contract 0.2). Provide `text` (a single character) or

        `code` (a raw platform key code). down=True presses/holds, False

        releases, None taps (press then release). Hold across step() frames for

        a program that samples input each frame."""

        parts = []

        if text is not None:

            # Percent-encode so a '+' isn't decoded to a space and '&'/'#'/'%'

            # don't truncate or corrupt the value. safe="" encodes '+' too.

            parts.append(f"text={urllib.parse.quote(text, safe='')}")

        if code is not None:

            parts.append(f"code={code}")

        if down is not None:

            parts.append(f"down={1 if down else 0}")

        if not parts:

            raise EmuControlError("key() needs text= or code=")

        self._post("/key?" + "&".join(parts))

    def reset(self) -> None:

        """Soft/cold reset the machine (contract 0.2)."""

        self._post("/reset")

    def screenshot_ppm(self) -> bytes:

        """Return the live screen as raw PPM (P6) bytes. Stdlib-only."""

        body, _ = self._get("/screenshot")

        return body

    def screenshot(self):

        """Return the live screen as a PIL.Image (requires Pillow)."""

        body = self.screenshot_ppm()

        try:

            from PIL import Image

        except ImportError as e:  # pragma: no cover

            raise EmuControlError("screenshot() needs Pillow (pip install pillow)") from e

        return Image.open(io.BytesIO(body))

    # -- helpers -----------------------------------------------------------

    def wait_ready(self, tries: int = 100, delay: float = 0.05) -> dict:

        """Poll /status until the server answers (emulator boot race)."""

        last = None

        for _ in range(tries):

            try:

                return self.status()

            except (EmuControlError, urllib.error.URLError, ConnectionError) as e:

                last = e

                time.sleep(delay)

        raise EmuControlError(f"emulator control port never came up: {last}")

    def run_to_frame(self, target: int) -> int:

        """Step until the frame counter reaches >= target."""

        cur = self.frame()

        if target > cur:

            self.step(frames=target - cur)

        return self.frame()