#!/usr/bin/env python3
"""Host-side verification of the laser pulse-stream emission.

Runs the native grblHAL_glowforge binary in null-sink mode with
GFSINK_DUMP capturing the shipped byte stream, drives small laser jobs
over TCP, then checks the dumps against the kernel feeder contract:

  1. a power byte (bit 7) leads the stream, before any tick byte
  2. no two consecutive power bytes (the SDMA script drops the second)
  3. the first FIRE bit (0x10) comes after a nonzero power byte
  4. power values match the S words through the core's mapping, floor
     included ($30=1000, $31=0, $35 = the board's floor), and no duty
     under FIRE falls below that floor
  5. FIRE only spans the cutting moves: none before the job, none during
     the G0 return, none at the tail
  6. step accounting survives the insertions: X returns to net zero and
     peaks at the programmed 10 mm
  7. termination: every stream ends with FIRE clear, including an M3
     (constant-power) job whose core never issues a laser-off update -
     the stream must never lean on the kernel's end-of-data backstop
  8. no FIRE bit ever rides a zero-step gap: a stepless run of stream
     bytes carrying FIRE longer than any legitimate between-step
     interval is a stationary dwell burn
  9. rules 7-8 hold across rapid cycle stop/start churn (planner-starve
     shaped jobs), where the FIRE state of the previous cycle must not
     leak into the idle-gap pad bytes
 10. a power ladder fires every rung at the duty commanded for it: no
     FIRE tick rides a duty that was never commanded (a run start resets
     the hardware duty to ~100 %, so a fire bit reaching the stream
     ahead of the rung's power byte would burn at full power), and the
     fire ticks divide evenly across the rungs, which is what fails if a
     rung's opening ticks carry the previous rung's duty
 11. under the density dose model no level ever reaches PWMSAR: every
     power byte carries full duty (one still leads each kernel run), and
     a level change inside a run costs no stream byte at all
 12. density matches the level the core commanded, rung by rung, and no
     burst is longer than the base period
 13. the model is a mask and never a source: run the same job under both
     models and every FIRE tick of the density run is a FIRE tick of the
     analog run, on an identical motion grid
 15. the minimum pulse width holds: no emitted burst is shorter than
     laser_pulse_min_ticks, and the levels too faint to fill it still
     render their exact average density - the debt is carried, so a low
     level becomes fewer full-width pulses rather than stubs
 14. a laser state change made while the stream is idle survives to the
     next run: a standalone S word between moves, from a sender slow
     enough to drain the planner, must still cut at the level it asked
     for rather than dark at a stale duty

Usage: laser_stream_test.py [path-to-binary]   (default ./build-native/grblHAL_glowforge)
"""
import os
import re
import shutil
import signal
import socket
import subprocess
import sys
import tempfile
import threading
import time

BIN = os.path.abspath(sys.argv[1] if len(sys.argv) > 1 else "build-native/grblHAL_glowforge")
PORT = 2399
STEPS_PER_MM = 53.333

# The S -> level mapping the board defaults produce: $30 = 1000, $31 = 0,
# and a $35 floor (boards/glowforge.h DEFAULT_SPINDLE_PWM_MIN_VALUE)
# against the hardware's 127-count period. The shipped floor is the
# density one; the analog sessions below select their model explicitly
# rather than inheriting the default, so both paths stay covered. Changing the board's floor
# changes every expectation below, which is why it is mirrored here
# rather than inferred from the stream.
PWM_PERIOD = 127
PWM_MIN_PCT = 10.0
PWM_MIN = int(PWM_PERIOD * PWM_MIN_PCT / 100.0)
RPM_MAX = 1000.0


def duty_for(s):
    """Duty the core computes for an S word, floor included."""
    return int(s * (PWM_PERIOD - PWM_MIN) / RPM_MAX) + PWM_MIN

# Longest stepless run allowed to carry FIRE, in machine ticks. The
# slowest legitimate between-step interval in these jobs is the first
# step of an accel-from-rest: sqrt(2 * (1/53.333 mm) / 700 mm/s^2)
# = 7.3 ms = ~206 ticks at 28160 Hz. 500 gives >2x margin while staying
# far below any idle-gap pad run.
FIRE_GAP_LIMIT_TICKS = 500

WAIT_IDLE = ("wait_idle",)

# Session A: the original M4 dynamic-power job (rules 1-6).
JOB_M4 = [
    "M4 S0",
    "G1 X5 F600 S500",
    "G1 X10 S1000",
    "G0 X0",
    "M5",
]

# Session B: M3 constant power to the end of the stream. The core never
# issues a laser-off update for M3, so the stream engine itself must
# terminate the cycle dark (rule 7).
JOB_M3_TERM = [
    "M3 S1000",
    "G1 X5 F600",
    WAIT_IDLE,
    ("sleep", 1.0),
    "M5",
]

# Session C: rapid cycle churn - many tiny laser moves sent one at a
# time with small gaps, so cycles stop and restart the way a planner
# starve produces them (rules 8-9).
JOB_CHURN = []
for _ in range(30):
    JOB_CHURN.append("G1 X0.2 F600 S800")
    JOB_CHURN.append(("sleep", 0.02))
    JOB_CHURN.append("G1 X0 S800")
    JOB_CHURN.append(("sleep", 0.02))
JOB_CHURN.insert(0, "M4 S0")
JOB_CHURN.append("M5")

# Session D: a power ladder in the shape the bench threshold drill uses -
# constant power (M3) so the commanded duty is the tested duty, rungs
# ascending, a dark G0 between them. Full power is deliberately absent
# from the ladder, so duty 127 under FIRE can only be a leak.
LADDER_S = (20, 30, 60, 120, 200, 300)
LADDER_DUTY = tuple(duty_for(s) for s in LADDER_S)
LADDER_MM = 5.0
JOB_LADDER = ["G91", "G21", "M3"]
for _i, _s in enumerate(LADDER_S):
    JOB_LADDER.append("S%d" % _s)
    JOB_LADDER.append("G1 X%g F300" % (LADDER_MM if _i % 2 == 0 else -LADDER_MM))
    JOB_LADDER.append("G0 Y1")
JOB_LADDER.append("M5")


# Sessions E-G: the density dose model. $35 = 0 for the ladder because
# the floor exists only to keep an analog duty out of the tube's dead
# band - under density every pulse is full-power, and a floor would just
# clamp the light end of the range.
ANALOG_CONF = "laser_power_model = analog\n"
DENSITY_PERIOD = 20
DENSITY_MIN_TICKS = 3
DENSITY_CONF = ("laser_power_model = density\n"
                "laser_pulse_ticks = %d\n"
                "laser_pulse_min_ticks = %d\n"
                % (DENSITY_PERIOD, DENSITY_MIN_TICKS))
DENSITY_LEVEL = tuple(int(x * PWM_PERIOD / RPM_MAX) for x in LADDER_S)
JOB_DENSITY = ["$35=0"] + JOB_LADDER

# Session H: three levels inside one kernel run. The moves are short and
# fast so the planner never drains, and each carries its own S word, so
# the level changes land mid-run. Analog pays a power byte per level;
# density pays none, because the level rides the FIRE bits.
JOB_LEVELS = ["G91", "G21", "M3"]
for _s in (100, 300, 600):
    for _ in range(20):
        JOB_LEVELS.append("G1 X0.5 F3000 S%d" % _s)
JOB_LEVELS.append("M5")


# Session I: the levels arrive on their own lines, and the moves are long
# enough that the planner drains between them, so each S is executed with
# nothing streaming. The state has no event to ride and must be
# re-asserted at the next run's first byte.
IDLE_S_LEVELS = (100, 300, 600)
IDLE_S_MM = 5.0
IDLE_S_FEED = 300
JOB_IDLE_S = ["G91", "G21", "M3"]
for _i, _s in enumerate(IDLE_S_LEVELS):
    JOB_IDLE_S.append("S%d" % _s)
    JOB_IDLE_S.append("G1 X%g F%d" % (IDLE_S_MM if _i % 2 == 0 else -IDLE_S_MM,
                                      IDLE_S_FEED))
JOB_IDLE_S.append("M5")


def fail(msg):
    print("FAIL: %s" % msg)
    sys.exit(1)


def send_line(sock, line, log):
    sock.sendall((line + "\n").encode())
    while True:
        r = read_avail(sock, log, 5.0, until=("ok", "error"))
        if r is None:
            fail("no ok/error for %r" % line)
        if r == "error":
            fail("error response to %r" % line)
        return


def read_avail(sock, log, timeout, until=None):
    end = time.time() + timeout
    buf = b""
    while time.time() < end:
        sock.settimeout(max(0.05, end - time.time()))
        try:
            data = sock.recv(4096)
        except socket.timeout:
            data = b""
        if data:
            buf += data
            log.append(data.decode(errors="replace"))
            if until:
                for token in until:
                    if re.search(r"^%s\b" % token, buf.decode(errors="replace"), re.M):
                        return token
        elif until is None:
            return None
    return None


def wait_idle(sock, log):
    for _ in range(100):
        sock.sendall(b"?")
        read_avail(sock, log, 0.3)
        if re.search(r"<Idle", "".join(log[-3:])):
            return
        time.sleep(0.2)
    fail("controller never returned to Idle")


def publish_verdicts(path, stop):
    """Publish a fresh, clean cooling verdict every 0.5 s (the arm flow
    refuses without one; freshness window is 2 s). Same-host monotonic
    clock, atomic rename so the reader never sees a torn file."""
    while not stop.is_set():
        body = ('{"ts_mono":%.3f,"fire_ok":true,"hold":false,'
                '"resume_ok":true,"reason":""}'
                % time.clock_gettime(time.CLOCK_MONOTONIC))
        tmp = path + ".tmp"
        with open(tmp, "w") as f:
            f.write(body)
        os.replace(tmp, path)
        stop.wait(0.5)


def run_session(name, steps, conf=None, workdir=None, keep=False,
                arm_required=True):
    """Launch the controller, run the job steps, return the dump bytes.

    Pass workdir + keep to chain launches over one settings file: the
    core precomputes the spindle PWM mapping once, when the spindle is
    enabled, so a $35 written at runtime only takes effect on the next
    controller start."""
    if workdir is None:
        workdir = tempfile.mkdtemp(prefix="laser-test-")
    dump = os.path.join(workdir, "stream.bin")
    verdict = os.path.join(workdir, "cooling.state")
    env = dict(os.environ, GFSINK_DUMP=dump, GF_VERDICT_FILE=verdict,
               FFLOG_STDERR="1")
    env.pop("GFSINK", None)
    if conf is not None:
        conf_path = os.path.join(workdir, "forgefirm.conf")
        with open(conf_path, "w") as f:
            f.write(conf)
        env["GFHOME_CONF"] = conf_path

    stop = threading.Event()
    pub = threading.Thread(target=publish_verdicts, args=(verdict, stop), daemon=True)
    pub.start()

    proc = subprocess.Popen([BIN, "-p", str(PORT)], cwd=workdir, env=env,
                            stdout=subprocess.DEVNULL, stderr=subprocess.PIPE)
    try:
        sock = None
        for _ in range(50):
            try:
                sock = socket.create_connection(("127.0.0.1", PORT), timeout=1)
                break
            except OSError:
                time.sleep(0.1)
        if sock is None:
            err = b""
            if proc.poll() is not None:
                err = proc.stderr.read() or b""
            fail("[%s] cannot connect to the controller (exit=%s)\n%s"
                 % (name, proc.poll(), err.decode(errors="replace")))

        log = []
        read_avail(sock, log, 0.5)          # banner / hello

        for step in steps:
            if step == WAIT_IDLE:
                wait_idle(sock, log)
            elif isinstance(step, tuple) and step[0] == "sleep":
                time.sleep(step[1])
            else:
                send_line(sock, step, log)

        # Wait for the motion to play out on the wall clock (the shipper
        # is wall-paced), then for the Idle report.
        wait_idle(sock, log)
        time.sleep(1.0)                     # let the shipper drain the tail
        text = "".join(log)

        run_session.text = text
        if arm_required and "laser armed" not in text:
            fail("[%s] no 'laser armed' message (arming flow did not run)" % name)

        sock.close()
    finally:
        proc.send_signal(signal.SIGINT)
        try:
            proc.wait(5)
        except subprocess.TimeoutExpired:
            proc.kill()
        stop.set()
        pub.join(2)

    data = open(dump, "rb").read()
    if not data and arm_required:
        fail("[%s] empty stream dump" % name)
    if not keep:
        shutil.rmtree(workdir, ignore_errors=True)
    return data


def tick_bytes(data):
    """The stream with power bytes stripped (tick bytes only)."""
    return bytes(b for b in data if not b & 0x80)


def check_fire_gaps(name, data):
    """Rule 8: no stepless run carrying FIRE longer than the limit."""
    run = 0
    worst = 0
    for tick, b in enumerate(tick_bytes(data)):
        if b & 0x10 and not b & 0x25:       # FIRE, no X/Y/Z step
            run += 1
            worst = max(worst, run)
            if run >= FIRE_GAP_LIMIT_TICKS:
                fail("[%s] FIRE carried across a %d-tick zero-step gap "
                     "ending at tick %d (stationary dwell burn)"
                     % (name, run, tick))
        else:
            run = 0
    return worst


def check_termination(name, data):
    """Rule 7: the stream's final tick byte must carry FIRE clear."""
    ticks = tick_bytes(data)
    if not ticks:
        fail("[%s] no tick bytes in the stream" % name)
    if ticks[-1] & 0x10:
        fail("[%s] stream ends with FIRE set (0x%02x) - termination "
             "rule violated, relies on the end-of-data backstop"
             % (name, ticks[-1]))


def check_m4_job(data):
    """Rules 1-6 on the original M4 job."""
    if not data[0] & 0x80:
        fail("stream does not lead with a power byte (first byte 0x%02x)" % data[0])

    prev_power = False
    cur_power = 0
    fire_ticks = []                 # (tick_index, power_at_that_tick)
    x_pos = 0
    x_min = x_max = 0
    tick = 0
    first_fire_power = None
    for b in data:
        if b & 0x80:
            if prev_power:
                fail("consecutive power bytes at tick %d" % tick)
            prev_power = True
            cur_power = b & 0x7F
            continue
        prev_power = False
        if b & 0x10:
            if first_fire_power is None:
                first_fire_power = cur_power
            fire_ticks.append((tick, cur_power))
        if b & 0x01:
            x_pos += -1 if b & 0x02 else 1
            x_min = min(x_min, x_pos)
            x_max = max(x_max, x_pos)
        if b & 0x24:
            fail("unexpected Y/Z step at tick %d (byte 0x%02x)" % (tick, b))
        tick += 1

    if not fire_ticks:
        fail("no FIRE bits in the stream")
    if first_fire_power == 0:
        fail("first FIRE bit rides duty 0 (power-before-fire violated)")

    powers = sorted(set(p for _, p in fire_ticks))
    if powers[-1] != PWM_PERIOD:
        fail("S1000 did not reach duty %d (max %d)" % (PWM_PERIOD, powers[-1]))
    want = duty_for(500)
    if not any(abs(p - want) <= 2 for p in powers):
        fail("S500 plateau (~%d) not seen (powers %s)" % (want, powers[:20]))
    if powers[0] < PWM_MIN:
        fail("duty %d under FIRE is below the $35 floor of %d: M4's ramp is "
             "commanding power the tube cannot lase at" % (powers[0], PWM_MIN))

    expect_peak = round(10 * STEPS_PER_MM)
    if abs(x_max - expect_peak) > 2:
        fail("X peak %d steps, expected ~%d" % (x_max, expect_peak))
    if x_pos != 0:
        fail("X net %d steps after return to 0" % x_pos)
    if x_min < 0:
        fail("X went negative (min %d)" % x_min)

    last_fire = fire_ticks[-1][0]
    tail_steps = 0
    tick = 0
    for b in data:
        if b & 0x80:
            continue
        if tick > last_fire and b & 0x01:
            tail_steps += 1
        tick += 1
    if tail_steps < 400:
        fail("only %d fire-free steps after the last FIRE bit - G0 return not dark" % tail_steps)

    return fire_ticks, powers, x_max, tail_steps


def check_power_ladder(name, data, expect):
    """Rule 10: every FIRE tick rides the duty commanded for its rung."""
    cur = None
    order = []                      # duties in the order they carry FIRE
    counts = {}
    for b in data:
        if b & 0x80:
            cur = b & 0x7F
            continue
        if b & 0x10:
            if cur is None:
                fail("[%s] FIRE bit ahead of any power byte" % name)
            counts[cur] = counts.get(cur, 0) + 1
            if not order or order[-1] != cur:
                order.append(cur)

    stray = sorted(d for d in counts if d not in expect)
    if stray:
        fail("[%s] FIRE rode uncommanded duty %s (commanded %s): power the "
             "job never asked for is uncommanded energy"
             % (name, stray, list(expect)))
    if order != list(expect):
        fail("[%s] duty sequence under FIRE was %s, expected %s"
             % (name, order, list(expect)))

    # Equal-length rungs at one feed burn equal numbers of fire ticks.
    # A rung whose opening ticks carry the previous rung's duty shows up
    # here as a surplus on one duty and a deficit on the next.
    lo, hi = min(counts.values()), max(counts.values())
    if hi > lo * 1.05:
        fail("[%s] fire ticks per rung uneven (%d..%d, %s): a rung is "
             "firing at its neighbor's duty" % (name, lo, hi, counts))
    return counts


def fire_spans(ticks, gap=500):
    """Tick spans carrying fire, split on dark gaps (the G0 between
    rungs). Within a rung the model's own dark stretches are at most a
    couple of base periods, far below the split."""
    spans = []
    start = last = None
    for i, b in enumerate(ticks):
        if b & 0x10:
            if start is None:
                start = i
            elif i - last > gap:
                spans.append((start, last + 1))
                start = i
            last = i
    if start is not None:
        spans.append((start, last + 1))
    return spans


def check_density(name, data, levels, period, min_ticks):
    """Rules 11-12: pinned duty, and density per rung matching the level."""
    # A power byte still leads every kernel run - the run start resets the
    # hardware duty - but under this model it only ever carries full duty:
    # the level rides the FIRE bits, never PWMSAR.
    powers = [b & 0x7F for b in data if b & 0x80]
    if not powers or set(powers) != {PWM_PERIOD}:
        fail("[%s] density mode shipped power bytes %s; every one must be "
             "full duty, or a level reached PWMSAR" % (name, sorted(set(powers))))

    ticks = tick_bytes(data)
    spans = fire_spans(ticks)
    if len(spans) != len(levels):
        fail("[%s] %d fire spans, expected one per rung (%d): %s"
             % (name, len(spans), len(levels), spans[:8]))

    out = []
    for (a, b), level in zip(spans, levels):
        seg = ticks[a:b]
        got = sum(1 for t in seg if t & 0x10) / float(len(seg))
        want = level / float(PWM_PERIOD)
        out.append((level, round(got, 4)))
        # A span is clipped to whole ticks, not whole periods, so allow a
        # little slack at the edges; the accumulator carries the rest.
        if abs(got - want) > max(0.01, want * 0.06):
            fail("[%s] level %d rendered density %.4f, expected %.4f"
                 % (name, level, got, want))
        # Burst lengths inside the span. The last one can be clipped by
        # the core turning fire off mid-burst, so it is not held to the
        # minimum; every other burst is a whole pulse the model chose.
        runs, run = [], 0
        for t in seg:
            if t & 0x10:
                run += 1
            elif run:
                runs.append(run)
                run = 0
        if run:
            runs.append(run)
        if not runs:
            fail("[%s] level %d produced no bursts at all" % (name, level))
        if max(runs) > period:
            fail("[%s] level %d burst of %d ticks exceeds the %d-tick base "
                 "period" % (name, level, max(runs), period))
        short = [r for r in runs[:-1] if r < min_ticks]
        if short:
            fail("[%s] level %d emitted %d burst(s) below the %d-tick minimum "
                 "(shortest %d): a stub too brief for the supply to strike"
                 % (name, level, len(short), min_ticks, min(short)))
    return out


def check_mask(analog, density):
    """Rule 13: same motion, and density fire is a subset of analog fire."""
    ta, td = tick_bytes(analog), tick_bytes(density)
    if len(ta) != len(td):
        fail("[mask] tick counts differ (analog %d, density %d): the two runs "
             "are not the same motion" % (len(ta), len(td)))
    for i, (a, b) in enumerate(zip(ta, td)):
        if (a & ~0x10) != (b & ~0x10):
            fail("[mask] motion differs at tick %d (analog 0x%02x, density "
                 "0x%02x)" % (i, a, b))
    stray = [i for i, (a, b) in enumerate(zip(ta, td)) if (b & 0x10) and not (a & 0x10)]
    if stray:
        fail("[mask] density fired %d tick(s) the core never commanded, first "
             "at %d - the model is acting as a source of emission, not a mask"
             % (len(stray), stray[0]))
    return sum(1 for b in td if b & 0x10), sum(1 for a in ta if a & 0x10)


def count_fire(data):
    return sum(1 for b in tick_bytes(data) if b & 0x10)


def main():
    # --- session A: M4 dynamic power, rules 1-6 + 7-8 -------------------
    data = run_session("m4", JOB_M4, conf=ANALOG_CONF)
    fire_ticks, powers, x_max, tail_steps = check_m4_job(data)
    check_termination("m4", data)
    gap_a = check_fire_gaps("m4", data)
    print("PASS [m4]: %d bytes, %d power bytes, %d fire ticks, powers %s, "
          "X peak %d steps net 0, %d dark return steps, max fire gap %d"
          % (len(data), sum(1 for b in data if b & 0x80), len(fire_ticks),
             powers, x_max, tail_steps, gap_a))

    # --- session B: M3 constant power to stream end, rule 7 -------------
    data = run_session("m3-term", JOB_M3_TERM, conf=ANALOG_CONF)
    if not count_fire(data):
        fail("[m3-term] no FIRE bits in the stream")
    check_termination("m3-term", data)
    gap_b = check_fire_gaps("m3-term", data)
    print("PASS [m3-term]: %d bytes, %d fire ticks end dark, max fire gap %d"
          % (len(data), count_fire(data), gap_b))

    # --- session C: cycle churn, rules 8-9 ------------------------------
    data = run_session("churn", JOB_CHURN, conf=ANALOG_CONF)
    if not count_fire(data):
        fail("[churn] no FIRE bits in the stream")
    check_termination("churn", data)
    gap_c = check_fire_gaps("churn", data)
    print("PASS [churn]: %d bytes, %d fire ticks, max fire gap %d"
          % (len(data), count_fire(data), gap_c))

    # --- session D: power ladder, rule 10 -------------------------------
    data = run_session("ladder", JOB_LADDER, conf=ANALOG_CONF)
    counts = check_power_ladder("ladder", data, LADDER_DUTY)
    check_termination("ladder", data)
    gap_d = check_fire_gaps("ladder", data)
    print("PASS [ladder]: %d bytes, duties %s fire ticks %s, max fire gap %d"
          % (len(data), list(LADDER_DUTY),
             [counts[d] for d in LADDER_DUTY], gap_d))

    # --- session E: the same ladder under the density model -------------
    # $35 is written by a first launch and takes effect on the second:
    # the floor exists only to keep an analog duty out of the tube's
    # dead band, and under density it would just clamp the light end.
    wd = tempfile.mkdtemp(prefix="laser-test-")
    run_session("density-setup", ["$35=0"], conf=DENSITY_CONF, workdir=wd,
                keep=True, arm_required=False)
    dens = run_session("density", JOB_DENSITY, conf=DENSITY_CONF, workdir=wd)
    rendered = check_density("density", dens, DENSITY_LEVEL, DENSITY_PERIOD,
                             DENSITY_MIN_TICKS)
    check_termination("density", dens)
    if "laser armed (density)" not in run_session.text:
        fail("[density] the arm did not select the density model")
    print("PASS [density]: %d bytes, %d power bytes all at full duty, "
          "level->density %s"
          % (len(dens), sum(1 for b in dens if b & 0x80), rendered))

    # --- rule 13: the model masks, it never sources ---------------------
    d_fire, a_fire = check_mask(data, dens)
    print("PASS [mask]: identical motion grid, %d density fire ticks all "
          "inside the %d the core commanded" % (d_fire, a_fire))

    # --- session F: full level under the model is continuous fire -------
    full = run_session("density-full", ["$35=0"] + JOB_M3_TERM, conf=DENSITY_CONF)
    ticks = tick_bytes(full)
    spans = fire_spans(ticks)
    if not spans:
        fail("[density-full] no FIRE bits in the stream")
    a, b = spans[0]
    got = sum(1 for t in ticks[a:b] if t & 0x10) / float(b - a)
    if got != 1.0:
        fail("[density-full] S1000 rendered density %.4f, expected 1.0" % got)
    check_termination("density-full", full)
    print("PASS [density-full]: S1000 -> density 1.0000 over %d ticks, ends dark"
          % (b - a))

    # --- session G: churn under the model (rules 7-9 still hold) --------
    ch = run_session("density-churn", ["$35=0"] + JOB_CHURN, conf=DENSITY_CONF)
    if not count_fire(ch):
        fail("[density-churn] no FIRE bits in the stream")
    check_termination("density-churn", ch)
    gap_e = check_fire_gaps("density-churn", ch)
    print("PASS [density-churn]: %d bytes, %d fire ticks, max fire gap %d"
          % (len(ch), count_fire(ch), gap_e))

    # --- session H: a level change inside a run costs no byte -----------
    lv_a = run_session("levels-analog", JOB_LEVELS, conf=ANALOG_CONF)
    lv_d = run_session("levels-density", JOB_LEVELS, conf=DENSITY_CONF)
    pa = [b & 0x7F for b in lv_a if b & 0x80]
    pd = [b & 0x7F for b in lv_d if b & 0x80]
    if len([d for d in set(pa) if d]) < 3:
        fail("[levels] the analog run shipped duties %s: fewer than the three "
             "commanded levels, so the job is not exercising in-run changes"
             % sorted(set(pa)))
    if set(pd) != {PWM_PERIOD}:
        fail("[levels] density shipped a level as duty: %s" % sorted(set(pd)))
    if len(pd) >= len(pa):
        fail("[levels] density shipped %d power bytes against analog's %d - "
             "the level changes are still costing stream bytes" % (len(pd), len(pa)))
    print("PASS [levels]: analog %d power bytes %s, density %d at full duty"
          % (len(pa), sorted(set(pa)), len(pd)))

    # --- session I: a level set while idle still cuts (rule 14) ---------
    idle_s = run_session("idle-s", JOB_IDLE_S, conf=ANALOG_CONF)
    fire_by_duty = {}
    cur = None
    for b in idle_s:
        if b & 0x80:
            cur = b & 0x7F
        elif b & 0x10:
            fire_by_duty[cur] = fire_by_duty.get(cur, 0) + 1
    want_ticks = IDLE_S_MM / (IDLE_S_FEED / 60.0) * 28160
    for level in IDLE_S_LEVELS:
        duty = duty_for(level)
        got = fire_by_duty.get(duty, 0)
        if got < want_ticks * 0.9:
            fail("[idle-s] S%d (duty %d) fired %d ticks, expected ~%d: a level "
                 "set while the stream was idle was dropped and the move ran "
                 "dark or at a stale duty (all: %s)"
                 % (level, duty, got, want_ticks, fire_by_duty))
    check_termination("idle-s", idle_s)
    print("PASS [idle-s]: standalone S across idle gaps -> fire ticks per duty %s"
          % {duty_for(l): fire_by_duty[duty_for(l)] for l in IDLE_S_LEVELS})

    print("PASS: all stream emission rules hold")


if __name__ == "__main__":
    main()