#!/usr/bin/python3
"""ft-gazed: the gaze service. The headset's eye tracking, corrected, for the pointer.

Two settings in ~/.config/frametop.conf (the Gaze page of Frametop Input Settings), read
again when the file changes:
  GAZE_TRACKER=steam|own   SteamVR's eye tracker (default), or our own (gaze/tracker/ft-eyes,
                           ft-gaze's source "own"; this service runs it, see below)
  GAZE_EYE=auto|left|right the eye bias (gazecal.EyeWeights): auto weights each eye by how far
                           off it was at your recent nudges; left or right counts that eye twice
                           as much as the other. Either eye alone carries the gaze when the
                           other isn't seen.

Runs ft-gaze (in the dev container), and for every eye tracker sample (90 Hz):

  1. drops blinks: both eyes' openness under half its running median (each eye its own),
     or both lost (the tracker's variance for them, ft-gaze's "unc", over EYE_LOST);
     Looks down past the screens (pitch under KEYBOARD_PITCH, on no Frametop screen: at the
     keyboard, through the gap by the nose) aren't sent, so the pointer stays where it was
     instead of following you down; the tracker often loses an eye there (the lids come
     down), and that isn't counted as a lost eye either;
  2. combines the eyes, each corrected on its own. With SteamVR, that's each eye's own
     reading (set 2, ft-gaze's "left" and "right"), corrected by its calibration from
     ft-gazeprobe (calibration.json, reloaded when the probe changes it) plus what the
     pointer's corrections have taught that eye since (LiveCorrection, saved in
     pointer-lessons.json), then weighted by the eye bias. A lost or closed eye drops out.
     Our own tracker keeps its own calibration, so its eyes are used as they come;
  3. smooths it with a fixation lock (the running mean of the current fixation, 1 degree);
  4. sends it to the pointer helper: "gz <yaw> <pitch> <raw yaw> <raw pitch>", head-relative
     degrees (yaw +left, pitch +up). The helper uses it only in gaze mode.

Without per-eye calibrations (a calibration from before the probe had the eyes as sources),
or with --source, it's the older path: one source, SteamVR's combined gaze (mmap set 1) by
default, corrected as a whole. There, with one eye lost or closed, the gaze comes from the
other (EyeFallback: that eye's own reading from set 2, plus what it usually reads against
the combined gaze, learned while both are seen). SteamVR's combined gaze (set 1) keeps going
on one eye too, but holds the lost eye's yaw, so it moves half as far sideways as the eyes
do. Before the fallback has learned an eye, set 1 is used as it is; set 2's combined
direction is the mean of the eyes' own (off by half of whatever the lost eye reads), so with
set 2 that sample is dropped, as is one where the angle between the eyes jumps more than 1.5
degrees from its median.

Lessons come back from the helper: when you nudge the gaze-placed pointer with the mouse and
click, it sends "lesson <raw yaw> <raw pitch> <true yaw> <true pitch>": where the raw gaze
was when the mouse took over, and where the pointer was when you clicked (you were looking
there). The gap is the tracker's error there. The raw gaze is the one sent, so it also says
when that look was (the history of what was sent), and so what each eye read then:
  - SteamVR: each eye learns its own error, unless the gaze was more than
    POINTER_GAZE_NUDGE_MAX degrees (frametop.conf, 15 by default; the helper's limit too)
    past the correction (then it wasn't a nudge onto what you looked at);
  - our tracker: unless it was more than POINTER_GAZE_NUDGE_MAX off, the look goes to it as
    a click ("click T YAW PITCH" on @ft_eyes), as the
    probe's clicks do, and it learns how far the headset has moved on your face. That's
    what it gets wrong, and after the headset was off, the first click resets it;
  - either way, how far off each eye was (before the lesson taught it anything) goes to the
    eye bias, for auto.

SteamVR's eye tracking log is followed for the headset going on (its eye model starts over,
and the error moves): lessons from before count less then, so the first few after it
relearn the offset.

Our own tracker (gaze/tracker/ft-eyes) runs here too, in the dev container, while
GAZE_TRACKER=own or the gaze probe asks for it ("eyes SECONDS", a lease the probe renews). It
reads the eye-camera frames the root service frametop-eyegrab copies (gaze/tracker/install.sh),
which copies them only while ft-eyes runs.

Checks and calibration (gaze/gazecheck.py): a one-dot quick check when the headset goes on or
our tracker asks for a click, and the full calibration when gaze mode comes on without one,
both in a panel fixed to the headset (gaze/panel/ft-gazepanel, which this service runs too).

Nothing here writes to SteamVR, its eye tracker, or its files: ft-gaze reads the eye
tracker's shared memory read-only.

Control socket: abstract unix datagram "@ft_gazed":
  lesson <rhy> <rhp> <thy> <thp>   from the pointer helper (see above)
  calverify <rhy> <rhp> <thy> <thp>  the same, the quick check's second step (gazecheck.py)
  recheck <deg>                    a keyboard correction past POINTER_GAZE_NUDGE_MAX: a quick check
  status                           reply: one JSON object
  forget                           drop what the lessons taught (the calibration stays)
  reload                           read calibration.json and the settings again
  eyes <seconds>                   keep our own tracker running that much longer (at most 120),
                                   whatever GAZE_TRACKER says: the probe's lease. Reply: "ok"
  quickcal                         the one-dot check now (the calibration if there's none)
  calibrate                        the full calibration in the panel
  calaccept | calquit              from the pointer helper while the panel is up: take this dot
                                   now (a left click, Meta+J) | close it (a right click, Meta+K)

Options: --source action|mmap1|mmap2 (the older one-source path with that source, whatever
the settings say; set 2 was a little quieter in the probe, but loses the pointer whenever
the tracker loses an eye), -v (a status line every 5 s on stderr), --to NAME (send the gaze
to the abstract socket @NAME instead of the pointer helper; for testing: a helper without
gaze mode forwards what it doesn't know to its driver).
"""

import argparse
import json
import math
import os
import selectors
import signal
import socket
import statistics
import subprocess
import sys
import time
from collections import deque
from pathlib import Path

sys.path.insert(0, str(Path(__file__).resolve().parent))
from gazecal import (DEFAULT_MODEL, EYE_FOUND, EYE_LOST, MODELS, STATE, Correction, EyeFallback,  # noqa: E402
                     EyeWeights, Fixation, LiveCorrection, SteamEyeLog)
from gazecheck import Checks  # noqa: E402

REPO = Path(__file__).resolve().parents[1]
HELPER = REPO / "gaze" / "build" / "ft-gaze"
ME = "\0ft_gazed"
POINTER = "\0ft_pointer_helper"
EYES_PROG = REPO / "gaze" / "tracker" / "ft-eyes"  # our own tracker
EYES_PYTHON = REPO / "gaze" / "tracker" / "build" / "venv" / "bin" / "python"  # numpy, OpenCV (build.sh)
EYES_SOCKET = "\0ft_eyes"                      # its control socket
EYES_CAMS = Path("/dev/shm/frametop-eyes-cams")  # the frames it reads (frametop-eyegrab.service)
CONF = Path.home() / ".config" / "frametop.conf"
CALIBRATION = STATE / "calibration.json"
LESSONS = STATE / "pointer-lessons.json"
LESSON_LOG = STATE / "pointer-lessons.jsonl"
SOURCES = ("action", "mmap1", "mmap2", "left", "right")  # the ones with a calibration here
SIDES = ("left", "right")  # ft-gaze's order, and the sources for each eye alone
TRACKERS = ("steam", "own")
BIASES = ("auto", "left", "right")
NUDGE_MAX = 15.0  # degrees: POINTER_GAZE_NUDGE_MAX's default, the largest lesson taken
HISTORY = 12.0    # seconds of the gaze sent, to find a lesson's look (the helper sends it up to 10 s later)
LOOK = 0.3        # seconds of samples before that moment make the look (the probe's fixation)
RETRY = 3.0       # seconds before starting ft-gaze again
EYES_RETRY = 10.0  # seconds before starting ft-eyes again after it stopped on its own
EYES_LEASE_MAX = 120.0
SETTLE = 0.3      # seconds after an eye is found again before the fallback learns from it
KEYBOARD_PITCH = -20.0  # degrees: gaze under this, on no screen, is a look at the keyboard


class PointerLessons(LiveCorrection):
    """LiveCorrection, with the offset held back: one lesson moves the whole correction by a
    third of what it measured, not all of it (two alike, half; three, three fifths). In the
    probe, clicks came thick and fast on a stale calibration, where the error was mostly one
    offset. Here lessons are few and the calibration is often fresh: in the first live test a
    6 degree lesson shifted everything 6 degrees, and the next target, 10 degrees away and
    1.4 off before, was 7.1 off (3.6 with this). Near the lesson, the kernel still takes up
    most of it (5.1 of the 6 degrees)."""

    RIDGE = [2.0] + LiveCorrection.RIDGE[1:]


def log(msg):
    print(f"ft-gazed: {msg}", file=sys.stderr, flush=True)


def read_settings():
    """(tracker, eye bias, nudge max) from frametop.conf, defaults for anything missing or unknown."""
    conf = {}
    try:
        for line in CONF.read_text().splitlines():
            line = line.split("#", 1)[0].strip()
            if "=" in line:
                k, v = line.split("=", 1)
                conf[k.strip()] = v.strip().lower()
    except OSError:
        pass
    tracker = conf.get("GAZE_TRACKER", "steam")
    bias = conf.get("GAZE_EYE", "auto")
    try:
        nudge = min(max(float(conf.get("POINTER_GAZE_NUDGE_MAX", NUDGE_MAX)), 1.0), 30.0)  # the helper's range
    except ValueError:
        nudge = NUDGE_MAX
    return tracker if tracker in TRACKERS else "steam", bias if bias in BIASES else "auto", nudge


def mtime(path):
    try:
        return path.stat().st_mtime
    except OSError:
        return None


class Service:
    def __init__(self, source, verbose, to=POINTER):
        self.override, self.verbose, self.to = source, verbose, to
        self.source = source or "mmap1"  # the older path's source
        STATE.mkdir(parents=True, exist_ok=True)
        self.tracker, self.bias, self.nudge_max = read_settings()
        self.conf_mtime = mtime(CONF)
        self.models = {name: Correction() for name in SOURCES}
        self.mode = DEFAULT_MODEL
        self.cal_mtime = None
        self.lives = {name: PointerLessons() for name in SOURCES}
        self.weights = {t: EyeWeights(self.bias) for t in TRACKERS}
        self.dirty = False
        self.load_calibration()
        self.load_lessons()
        self.steam = SteamEyeLog()
        self.steam.poll()
        self.refit()
        self.fix = Fixation(radius=1.0)
        self.opens = (deque(maxlen=90), deque(maxlen=90))  # left, right
        self.vergence = deque(maxlen=90)
        self.fallback = EyeFallback()
        self.lost = [False, False]
        self.bad_at = [0.0, 0.0]    # sample time an eye was last lost or closed
        self.counts = {"samples": 0, "sent": 0, "blinks": 0, "one_eye": 0, "one_eye_used": 0, "lost_left": 0,
                       "lost_right": 0, "looking_down": 0, "dropped": 0, "lessons_taken": 0, "refused": 0}
        self.last_sample = 0.0
        self.last = None
        self.last_kind = None
        # What was sent, for finding a lesson's look: (sample time, raw as sent, each eye's reading).
        self.history = deque()
        self.own = {}        # our tracker's last status reply
        self.own_at = 0.0
        self.eyes_proc = None  # ft-eyes, while it runs
        self.eyes_until = 0.0  # the probe's lease (monotonic time)
        self.eyes_restart_at = 0.0

        self.sock = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM | socket.SOCK_CLOEXEC | socket.SOCK_NONBLOCK)
        self.sock.bind(ME)
        self.out = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM | socket.SOCK_CLOEXEC | socket.SOCK_NONBLOCK)
        # To our tracker, with an address of its own, so its replies don't land on @ft_gazed.
        self.eyes_sock = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM | socket.SOCK_CLOEXEC | socket.SOCK_NONBLOCK)
        self.eyes_sock.bind("")
        self.sel = selectors.DefaultSelector()
        self.sel.register(self.sock, selectors.EVENT_READ, "control")
        self.sel.register(self.eyes_sock, selectors.EVENT_READ, "own")
        self.checks = Checks(self, self.sel)
        self.proc = None
        self.buf = b""
        self.restart_at = 0.0
        self.running = True

    @property
    def kind(self):
        """"own" (our tracker), "eyes" (SteamVR's eyes, each corrected), or "source" (the
        older path: one SteamVR source, corrected as a whole)."""
        if self.override:
            return "source"
        if self.tracker == "own":
            return "own"
        return "eyes" if all(self.models[e].samples for e in SIDES) else "source"

    # --- Settings, calibration and lessons ---

    def load_settings(self):
        self.conf_mtime = mtime(CONF)
        tracker, bias, self.nudge_max = read_settings()
        if (tracker, bias) != (self.tracker, self.bias):
            log(f"tracker {tracker}, eye bias {bias}" + (f" (--source {self.override} wins)" if self.override else ""))
            self.tracker, self.bias = tracker, bias
            for w in self.weights.values():
                w.bias = bias
            self.fix.reset()

    def load_calibration(self):
        try:
            mt = CALIBRATION.stat().st_mtime
            d = json.loads(CALIBRATION.read_text())
        except (OSError, ValueError):
            return
        self.cal_mtime = mt
        for name in SOURCES:
            if name in d:
                self.models[name].from_json(d[name])
        mode = d.get("_meta", {}).get("model")
        self.mode = mode if mode in MODELS else DEFAULT_MODEL
        log(f"calibration: {self.mode}, " + ", ".join(f"{n} {self.models[n].samples}" for n in (self.source,) + SIDES)
            + " samples")

    def load_lessons(self):
        try:
            d = json.loads(LESSONS.read_text())
        except (OSError, ValueError):
            d = {}
        # The first version kept one source's: {"source": NAME, "samples": [...]}.
        sources = d.get("sources") or ({d["source"]: d.get("samples", [])} if "source" in d else {})
        for name, samples in sources.items():
            if name in self.lives:
                self.lives[name].samples = samples[-PointerLessons.KEEP:]
        for t, misses in (d.get("misses") or {}).items():
            if t in self.weights:
                self.weights[t] = EyeWeights(self.bias, misses)
        log(", ".join(f"{n} {len(self.lives[n].samples)}" for n in (self.source,) + SIDES) + " lessons")

    def save_lessons(self):
        tmp = LESSONS.with_suffix(".tmp")
        tmp.write_text(json.dumps({"version": 2, "sources": {n: lv.samples for n, lv in self.lives.items() if lv.samples},
                                   "misses": {t: w.misses for t, w in self.weights.items()}}))
        tmp.replace(LESSONS)
        self.dirty = False

    def forget_lessons(self):
        """Drop what the lessons taught (the calibration stays)."""
        self.lives = {name: PointerLessons() for name in SOURCES}
        self.weights = {t: EyeWeights(self.bias) for t in TRACKERS}
        self.refit()
        self.save_lessons()

    def refit(self):
        for name, live in self.lives.items():
            live.wear_time = self.steam.worn()
            live.refit(self.models[name], self.mode)

    def correction(self, name, hy, hp):
        by, bp = self.models[name].get(hy, hp, self.mode)
        ly, lp = self.lives[name].get(hy, hp)
        return by + ly, bp + lp

    def look(self, ry, rp):
        """When the gaze sent as raw (ry, rp) was last sent, and each eye's median reading over
        the LOOK before it: (t, [(yaw, pitch) or None] * 2), or (None, None)."""
        key = f"{ry:.3f} {rp:.3f}"
        t = next((h[0] for h in reversed(self.history) if h[1] == key), None)
        if t is None:
            return None, None
        eyes = []
        for k in (0, 1):
            seen = [h[2][k] for h in self.history if t - LOOK <= h[0] <= t and h[2] and h[2][k]]
            eyes.append((statistics.median(e[0] for e in seen), statistics.median(e[1] for e in seen)) if seen else None)
        return t, eyes

    def lesson(self, rhy, rhp, thy, thp, limit=True):
        """Learn a lesson; limit=False takes it whatever its size (the quick check's own)."""
        kind = self.kind
        limit = self.nudge_max if limit else math.inf
        rec = {"time": time.time(), "kind": kind, "raw": [rhy, rhp], "true": [thy, thp], "wear": self.steam.worn()}
        if kind == "source":
            dy, dp = thy - rhy, thp - rhp  # the whole error there
            cy, cp = self.correction(self.source, rhy, rhp)
            left = math.hypot(dy - cy, dp - cp)
            rec.update(source=self.source, model=self.mode, correction=[cy, cp], lesson_deg=left)
            if left > limit:
                rec["refused"] = f"more than {limit} deg past the correction"
            else:
                self.lives[self.source].add({"time": rec["time"], "hy": rhy, "hp": rhp, "dy": dy, "dp": dp,
                                             "wy": 1.0, "wp": 1.0, "how": "pointer"}, self.models[self.source], self.mode)
            return self.taken(rec)
        # The raw gaze sent here is the corrected, combined one: its whole error is left.
        left = math.hypot(thy - rhy, thp - rhp)
        t, eyes = self.look(rhy, rhp)
        weights = self.weights[self.tracker if kind == "own" else "steam"]
        rec.update(tracker=self.tracker if kind == "own" else "steam", bias=self.bias, lesson_deg=left, look_t=t,
                   eyes=eyes, weights=[round(w, 3) for w in weights.weights()])
        if t is None:
            rec["refused"] = "that gaze isn't in the last few seconds sent"
        elif left > limit:
            rec["refused"] = f"more than {limit} deg off"
        if "refused" in rec:
            return self.taken(rec)
        if kind == "own":
            # Its eyes come calibrated: how far off each was is its miss. The click goes to it.
            miss = [math.hypot(thy - e[0], thp - e[1]) if e else None for e in eyes]
            try:
                self.eyes_sock.sendto(f"click {t:.6f} {thy:.4f} {thp:.4f}".encode(), EYES_SOCKET)
            except OSError as e:
                rec["refused"] = f"our tracker isn't running ({e})"
                return self.taken(rec)
        else:
            miss = []
            for name, e in zip(SIDES, eyes):
                if not e:
                    miss.append(None)
                    continue
                cy, cp = self.correction(name, *e)
                miss.append(math.hypot(thy - e[0] - cy, thp - e[1] - cp))
                self.lives[name].add({"time": rec["time"], "hy": e[0], "hp": e[1], "dy": thy - e[0], "dp": thp - e[1],
                                      "wy": 1.0, "wp": 1.0, "how": "pointer"}, self.models[name], self.mode)
        rec["miss"] = miss
        weights.add(miss)
        return self.taken(rec)

    def taken(self, rec):
        if "refused" in rec:
            self.counts["refused"] += 1
        else:
            self.counts["lessons_taken"] += 1
            self.dirty = True
        try:
            with open(LESSON_LOG, "a") as f:
                f.write(json.dumps(rec) + "\n")
        except OSError as e:
            log(f"lesson log: {e}")
        return rec

    # --- ft-gaze ---

    def start_helper(self):
        if not HELPER.exists():
            log(f"ft-gaze isn't built: run {REPO}/gaze/build.sh")
            self.restart_at = time.monotonic() + 30
            return
        env = dict(os.environ)
        env["XDG_RUNTIME_DIR"] = f"/run/user/{os.getuid()}"  # podman needs the real one
        subprocess.run([str(REPO / "scripts" / "container-up.sh")], env=env, check=False)
        distrobox = Path.home() / ".local" / "bin" / "distrobox"
        # ft-gaze quits when its stdin closes: the one thing distrobox passes on.
        self.proc = subprocess.Popen([str(distrobox), "enter", "dev", "--", str(HELPER), "--watch-stdin"], env=env,
                                     stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                                     start_new_session=True)
        os.set_blocking(self.proc.stdout.fileno(), False)
        os.set_blocking(self.proc.stderr.fileno(), False)
        self.sel.register(self.proc.stdout, selectors.EVENT_READ, "stdout")
        self.sel.register(self.proc.stderr, selectors.EVENT_READ, "stderr")
        self.buf = b""
        log("ft-gaze started")

    def stop_helper(self):
        if not self.proc:
            return
        for f in (self.proc.stdout, self.proc.stderr):
            try:
                self.sel.unregister(f)
            except (KeyError, ValueError):
                pass
        if self.proc.stdin and not self.proc.stdin.closed:
            self.proc.stdin.close()
        try:
            self.proc.wait(timeout=2)
        except subprocess.TimeoutExpired:
            try:
                os.killpg(self.proc.pid, signal.SIGTERM)
            except ProcessLookupError:
                pass
        self.proc = None

    def eyes_wanted(self):
        return (self.tracker == "own" and not self.override) or time.monotonic() < self.eyes_until

    def start_eyes(self):
        """Our own tracker, in the dev container, with build/venv's numpy and OpenCV. Like
        ft-gaze, it quits when its stdin closes."""
        if not EYES_PYTHON.exists():
            log(f"ft-eyes isn't built: run {REPO}/gaze/tracker/build.sh")
            self.eyes_restart_at = time.monotonic() + 30
            return
        env = dict(os.environ)
        env["XDG_RUNTIME_DIR"] = f"/run/user/{os.getuid()}"
        subprocess.run([str(REPO / "scripts" / "container-up.sh")], env=env, check=False)
        distrobox = Path.home() / ".local" / "bin" / "distrobox"
        self.eyes_proc = subprocess.Popen([str(distrobox), "enter", "dev", "--", str(EYES_PYTHON), str(EYES_PROG), "-v",
                                           "--watch-stdin"], env=env, stdin=subprocess.PIPE,
                                          stdout=subprocess.DEVNULL, stderr=subprocess.PIPE, start_new_session=True)
        os.set_blocking(self.eyes_proc.stderr.fileno(), False)
        self.sel.register(self.eyes_proc.stderr, selectors.EVENT_READ, "eyes")
        log("ft-eyes started" + ("" if EYES_CAMS.exists() else
                                 f": no {EYES_CAMS} yet (the frame grabber: gaze/tracker/install.sh)"))

    def stop_eyes(self):
        if not self.eyes_proc:
            return
        try:
            self.sel.unregister(self.eyes_proc.stderr)
        except (KeyError, ValueError):
            pass
        if self.eyes_proc.stdin and not self.eyes_proc.stdin.closed:
            self.eyes_proc.stdin.close()
        try:
            self.eyes_proc.wait(timeout=3)
        except subprocess.TimeoutExpired:
            try:
                os.killpg(self.eyes_proc.pid, signal.SIGTERM)
            except ProcessLookupError:
                pass
        self.eyes_proc = None
        self.own = {}

    def read_eyes(self):
        try:
            data = os.read(self.eyes_proc.stderr.fileno(), 65536)
        except BlockingIOError:
            return
        if not data:
            log(f"ft-eyes stopped (exit {self.eyes_proc.poll()}); again in {EYES_RETRY:.0f} s if still wanted")
            self.stop_eyes()
            self.eyes_restart_at = time.monotonic() + EYES_RETRY
            return
        for line in data.decode("utf-8", "replace").splitlines():
            if line.strip() and (self.verbose or "fps" not in line):
                log(line)

    def read_stdout(self):
        try:
            data = os.read(self.proc.stdout.fileno(), 65536)
        except BlockingIOError:
            return
        if not data:
            log(f"ft-gaze stopped (exit {self.proc.poll()}); again in {RETRY:.0f} s")
            self.stop_helper()
            self.restart_at = time.monotonic() + RETRY
            return
        self.buf += data
        *lines, self.buf = self.buf.split(b"\n")
        for line in lines:
            try:
                self.on_sample(json.loads(line))
            except (ValueError, KeyError, TypeError) as e:
                log(f"bad sample: {e}")

    def read_stderr(self):
        try:
            data = os.read(self.proc.stderr.fileno(), 65536)
        except BlockingIOError:
            return
        for line in data.decode("utf-8", "replace").splitlines():
            if line.strip():
                log(line)

    def judge_eyes(self, m1, down):
        """Which eyes (left, right) are closed, from SteamVR's openness (set 1); updates
        self.lost from its variances. Blinks and lost eyes are judged against the last second
        (see steady_samples: relative, because the lids come down looking down). An eye's
        floor comes from its good readings, so a lost eye doesn't drag it to 0."""
        low = [False, False]
        o = m1.get("open")
        if o and len(o) == 2:
            for k in (0, 1):
                hist = self.opens[k]
                good = [v for v in hist if v >= 0.12]
                floor = max(0.12, 0.5 * statistics.median(good)) if len(good) >= 30 else 0.12
                low[k] = o[k] < floor
                hist.append(o[k])
        unc = m1.get("unc")
        if unc and len(unc) == 2:
            for k in (0, 1):
                self.lost[k] = unc[k] > (EYE_FOUND if self.lost[k] else EYE_LOST)
            if not down:
                self.counts["lost_left"] += self.lost[0]
                self.counts["lost_right"] += self.lost[1]
        return low

    def on_sample(self, s):
        self.checks.on_sample(s)
        kind = self.kind
        if kind != self.last_kind:
            log({"own": "our own tracker", "eyes": "SteamVR's eyes, each calibrated",
                 "source": f"SteamVR's {self.source}, calibrated as a whole"}[kind]
                + (f", eye bias {self.bias}" if kind != "source" else ""))
            self.last_kind = kind
            self.fix.reset()
        if kind == "source":
            self.on_source_sample(s)
        else:
            self.on_eyes_sample(s, kind == "own")

    def on_eyes_sample(self, s, own):
        m1 = s["src"].get("mmap1") or {}
        if own:
            src = s["src"].get("own") or {}
            if "hy" not in src:
                return
            eyes = [tuple(e) if e else None for e in (src.get("eyes") or [None, None])]
            hp, hit = src["hp"], src.get("hit")
        else:
            per = [s["src"].get(name) or {} for name in SIDES]
            eyes = [(p["hy"], p["hp"]) if "hy" in p else None for p in per]
            if not any(eyes):
                return
            hp, hit = next(e[1] for e in eyes if e), m1.get("hit")
        self.counts["samples"] += 1
        self.last_sample = time.monotonic()
        down = hp < KEYBOARD_PITCH and not hit
        low = self.judge_eyes(m1, down)
        if down:
            self.counts["looking_down"] += 1
            return
        # Our tracker finds the pupils itself; SteamVR's openness still marks the blinks.
        bad = [eyes[k] is None or low[k] or (not own and self.lost[k]) for k in (0, 1)]
        if all(bad):
            self.counts["blinks"] += 1
            return
        if any(bad):
            self.counts["one_eye"] += 1
            self.counts["one_eye_used"] += 1
        seen = [None if bad[k] else eyes[k] for k in (0, 1)]
        if own:
            corrected = seen
        else:
            corrected = []
            for name, e in zip(SIDES, seen):
                c = self.correction(name, *e) if e else None
                corrected.append((e[0] + c[0], e[1] + c[1]) if e else None)
        gy, gp = self.weights["own" if own else "steam"].combine(corrected)
        fy, fp = self.fix(gy, gp, s["t"], 1.0)
        self.send(s["t"], fy, fp, fy, fp, seen)

    def on_source_sample(self, s):
        src = s["src"].get(self.source) or {}
        if "hy" not in src:
            return
        self.counts["samples"] += 1
        self.last_sample = time.monotonic()
        m1 = s["src"].get("mmap1") or {}
        lr = src.get("lr", m1.get("lr"))
        down = src["hp"] < KEYBOARD_PITCH and not src.get("hit")
        low = self.judge_eyes(m1, down)
        if down:
            self.counts["looking_down"] += 1
            for k in (0, 1):
                self.bad_at[k] = s["t"]  # the fallback doesn't learn from these either
            return
        bad = [low[k] or self.lost[k] for k in (0, 1)]
        if all(bad):
            self.counts["blinks"] += 1
            return
        hy, hp = src["hy"], src["hp"]
        eyes = (s["src"].get("mmap2") or {}).get("eyes")
        for k in (0, 1):
            if bad[k]:
                self.bad_at[k] = s["t"]
        if any(bad):
            self.counts["one_eye"] += 1
            seen = 1 if bad[0] else 0
            est = self.fallback.get(seen, eyes[seen][0], eyes[seen][1]) if eyes else None
            if est:
                hy, hp = est
                self.counts["one_eye_used"] += 1
            elif self.source == "mmap2":
                self.counts["dropped"] += 1
                return
        else:
            if self.source == "mmap2":
                jump = (lr is not None and len(self.vergence) >= 30
                        and abs(lr - statistics.median(self.vergence)) > 1.5)
                if lr is not None:
                    self.vergence.append(lr)
                if jump:
                    self.counts["dropped"] += 1
                    return
            # Learn only once both have been seen for a moment: the tracker's filter starts
            # an eye over when it finds it again.
            if eyes and s["t"] - max(self.bad_at) > SETTLE:
                for k in (0, 1):
                    self.fallback.update(k, eyes[k][0], eyes[k][1], hy, hp)
        # The fixation lock works in degrees here (1 degree per "pixel").
        fy, fp = self.fix(hy, hp, s["t"], 1.0)
        cy, cp = self.correction(self.source, fy, fp)
        self.send(s["t"], fy + cy, fp + cp, fy, fp, None)

    def send(self, t, hy, hp, rhy, rhp, eyes):
        self.last = (hy, hp, rhy, rhp)
        raw = f"{rhy:.3f} {rhp:.3f}"
        self.history.append((t, raw, eyes))
        while self.history and self.history[0][0] < t - HISTORY:
            self.history.popleft()
        try:
            self.out.sendto(f"gz {hy:.3f} {hp:.3f} {raw}".encode(), self.to)
            self.counts["sent"] += 1
        except OSError:
            pass  # the pointer helper isn't running

    # --- Control ---

    def on_control(self):
        while True:
            try:
                data, addr = self.sock.recvfrom(512)
            except BlockingIOError:
                return
            words = data.decode("utf-8", "replace").split()
            reply = None
            if words[:1] == ["lesson"] and len(words) == 5:
                try:
                    rec = self.lesson(*map(float, words[1:]))
                    self.checks.after_lesson(rec)
                    reply = "refused" if "refused" in rec else f"ok {rec['lesson_deg']:.2f}"
                    log(f"lesson {rec['lesson_deg']:.2f} deg at {rec['raw'][0]:+.1f},{rec['raw'][1]:+.1f}"
                        + (f", eyes off {', '.join('-' if m is None else f'{m:.2f}' for m in rec['miss'])}"
                           if rec.get("miss") else "")
                        + (f": {rec['refused']}" if "refused" in rec else ""))
                except ValueError:
                    reply = "error bad lesson"
            elif words[:1] == ["status"]:
                reply = json.dumps(self.status())
            elif words[:1] == ["forget"]:
                self.forget_lessons()
                reply = "ok"
            elif words[:1] and words[0] in ("quickcal", "calibrate", "calaccept", "calquit", "calverify", "recheck"):
                reply = self.checks.command(words)
            elif words[:1] == ["eyes"] and len(words) == 2:
                try:
                    secs = min(max(float(words[1]), 0.0), EYES_LEASE_MAX)
                    self.eyes_until = max(self.eyes_until, time.monotonic() + secs)
                    reply = "ok"
                except ValueError:
                    reply = "error bad seconds"
            elif words[:1] == ["reload"]:
                self.load_settings()
                self.load_calibration()
                self.refit()
                reply = "ok"
            else:
                reply = "error unknown command"
            if reply and addr:
                try:
                    self.sock.sendto(reply.encode(), addr)
                except OSError:
                    pass

    def on_own(self):
        """Replies from our tracker: its status (JSON), or a click's "ok ..."/"fail ..."."""
        while True:
            try:
                data = self.eyes_sock.recv(4096).decode("utf-8", "replace")
            except (BlockingIOError, OSError):
                return
            if data.startswith("{"):
                try:
                    self.own, self.own_at = json.loads(data), time.monotonic()
                except ValueError:
                    pass
            else:
                log(f"our tracker: {data}")

    def status(self):
        kind = self.kind
        tracker = "own" if kind == "own" else "steam"
        w = self.weights[tracker]
        st = {"tracker": tracker, "kind": kind, "source": "own" if kind == "own" else self.source if kind == "source"
              else "left+right", "model": self.mode, "eye_bias": self.bias}
        if kind == "source":
            ly, lp = self.lives[self.source].offset()
            st.update(calibration_samples=self.models[self.source].samples, lessons=len(self.lives[self.source].samples),
                      lesson_offset=[round(ly, 3), round(lp, 3)])
        else:
            st.update(eye_weights=[round(v, 3) for v in w.weights()], eye_misses=[len(m) for m in w.misses],
                      eye_rms=[None if r is None else round(r, 2) for r in w.rms()])
        if kind == "eyes":
            st.update(calibration_samples=min(self.models[e].samples for e in SIDES),
                      lessons=max(len(self.lives[e].samples) for e in SIDES))
        if kind == "own":
            own = self.own if time.monotonic() - self.own_at < 5 else {}
            cal = own.get("calibration") or {}
            st.update(calibration_samples=cal.get("dots", 0), calibration_made=cal.get("made"),
                      lessons=max(len(m) for m in w.misses), own_running=bool(own),
                      own_reseat=any(e.get("reseat") for e in own.get("eyes", {}).values()))
        st.update(eyes_process=self.eyes_proc is not None, eyegrab=EYES_CAMS.exists())
        st.update({"ft_gaze": self.proc is not None, "sample_age_s": round(time.monotonic() - self.last_sample, 2)
                   if self.last_sample else None, "headset_on": self.steam.wearing(),
                   "headset_on_since": self.steam.worn(), "last": [round(v, 2) for v in self.last] if self.last else None,
                   "eyes_lost": self.lost, "fallback_ready": [self.fallback.ready(0), self.fallback.ready(1)],
                   "checks": self.checks.status(), **self.counts})
        return st

    def periodic(self):
        if self.steam.poll() or any(lv.wear_time != self.steam.worn() for lv in self.lives.values()):
            if any(lv.wear_time != self.steam.worn() for lv in self.lives.values()):
                log("headset on again: older lessons count less until new ones come in")
            self.refit()
        if mtime(CALIBRATION) != self.cal_mtime:
            self.load_calibration()
            self.refit()
        if mtime(CONF) != self.conf_mtime:
            self.load_settings()
        want = self.eyes_wanted()
        if want and not self.eyes_proc and time.monotonic() >= self.eyes_restart_at:
            self.start_eyes()
        elif not want and self.eyes_proc:
            log("ft-eyes no longer wanted: stopping it")
            self.stop_eyes()
        if self.eyes_proc:
            try:
                self.eyes_sock.sendto(b"status", EYES_SOCKET)
            except OSError:
                pass  # not up yet: status() says so once the last answer is old
        self.checks.periodic()
        if self.dirty:
            self.save_lessons()

    def run(self):
        next_periodic = time.monotonic()
        next_verbose = time.monotonic() + 5
        while self.running:
            now = time.monotonic()
            if not self.proc and now >= self.restart_at:
                self.start_helper()
            for key, _ in self.sel.select(timeout=0.05 if self.checks.active else 0.5):
                if key.data == "control":
                    self.on_control()
                elif key.data == "checks":
                    self.checks.on_readable()
                elif key.data == "panel" and self.checks.panel_proc:
                    self.checks.read_panel()
                elif key.data == "own":
                    self.on_own()
                elif key.data == "eyes" and self.eyes_proc:
                    self.read_eyes()
                elif key.data == "stdout" and self.proc:
                    self.read_stdout()
                elif key.data == "stderr" and self.proc:
                    self.read_stderr()
            self.checks.tick()
            if now >= next_periodic:
                self.periodic()
                next_periodic = now + 1.0
            if self.verbose and now >= next_verbose:
                log(json.dumps(self.status()))
                next_verbose = now + 5
        self.checks.stop()
        self.stop_helper()
        self.stop_eyes()
        if self.dirty:
            self.save_lessons()


def main():
    ap = argparse.ArgumentParser(description="The gaze service: corrected eye tracking for the pointer")
    ap.add_argument("--source", choices=["action", "mmap1", "mmap2"],
                    help="the older one-source path with this SteamVR source, whatever the settings say")
    ap.add_argument("-v", "--verbose", action="store_true")
    ap.add_argument("--to", default="ft_pointer_helper", help="abstract socket to send the gaze to")
    args = ap.parse_args()
    try:
        service = Service(args.source, args.verbose, "\0" + args.to)
    except OSError as e:
        log(f"can't bind @ft_gazed (already running?): {e}")
        sys.exit(1)

    def stop(*_):
        service.running = False
    signal.signal(signal.SIGTERM, stop)
    signal.signal(signal.SIGINT, stop)
    service.run()


if __name__ == "__main__":
    main()