seismo-relay/micromate/protocol.py

"""
protocol.py — one method per Micromate (Series IV) wire command.

Returns raw payload bytes.  Interpretation belongs in ``client.py``; this layer
knows frames, offsets and sequencing, and nothing about what a field means.

Scope: **reads only.**  Nothing here writes, erases, or changes monitoring
state.  That is deliberate and worth keeping — no command has ever been
originated against a unit by this project; every write in
``docs/micromate_protocol_reference.md`` was performed by THOR while we
recorded.  The first thing this codebase ever sends to a customer's instrument
should be a decision someone made on purpose, not a side effect of a client
that grew a method.

Every offset and params layout below was read off THOR's own frames in
``bridges/captures/9-24-26 - micromate2/`` rather than taken from the spec
table, because the same exercise during the framing work found three of that
table's rules wrong.  It found three more here:

  * ``0x0A`` is the **monitor-log walk** — the same request repeated, the
    device advancing its own cursor, terminated by a short response — not the
    keyed "event header, 30 B list record" the spec describes.
  * ``0x1E``/``0x1F`` carry **token 0xFE** at ``params[7]``.  The protocol
    reference documents all-zero params for the browse walk; that was our own
    probing, and THOR does not do it that way.
  * There is **no fixed preamble**.  Sessions open with ``POLL`` and go
    straight to the operation.  ``POLL → SERIAL → 0x49 → POLL`` appears in 3 of
    8 captured sessions and is THOR's *connection check*, not a handshake.

And one useful negative: **no ``SESSION_RESET`` (``41 03``).**  Series III
needs that 2-byte signal to wake a monitoring unit or it will not answer POLL
over TCP.  THOR never sends it — 0 occurrences across all 8 sessions, including
40 frames exchanged with a unit that *was* monitoring.
"""

from __future__ import annotations

import logging
import math
import struct
import time
from typing import Optional

from minimateplus.transport import BaseTransport

from .framing import MicromateFrame, MicromateFrameParser, build_request

log = logging.getLogger(__name__)

DEFAULT_RECV_TIMEOUT = 10.0

# An acknowledgement carries an 11-byte data section and nothing else.  It is
# also how the monitor-log walk says "no more records".
ACK_DATA_LEN = 11


# ── Command SUBs ──────────────────────────────────────────────────────────────

SUB_DEVICE_INFO       = 0x01
SUB_STORAGE_RANGE     = 0x06
SUB_EVENT_INDEX       = 0x08
SUB_MONITOR_LOG       = 0x0A
SUB_EVENT_RECORD      = 0x0C
SUB_SERIAL            = 0x15
SUB_COMPLIANCE_CONFIG = 0x1A
SUB_MONITOR_STATUS    = 0x1C
SUB_EVENT_FIRST       = 0x1E
SUB_EVENT_NEXT        = 0x1F
SUB_CALL_HOME_CONFIG  = 0x2C
SUB_TRIGGER_CONFIG    = 0x2E
SUB_SETUP_FIRST       = 0x3F
SUB_SETUP_NEXT        = 0x40
SUB_SETUP_ACTIVE      = 0x41
SUB_STATE             = 0x49
SUB_BULK_DOWNLOAD     = 0x5A
SUB_POLL              = 0x5B
SUB_ARM_EVENT         = 0x93

# ⚠ Reads are SINGLE-STEP.  Series III probes at offset 0 to learn the length,
# then reads again at that length; a Micromate returns the whole block when
# asked for 0xFFFF.  THOR never probes, which is why `MicromateFrame.probe_length`
# reads 0 on live traffic.
READ_ALL = 0xFFFF

# The two commands that do NOT use READ_ALL, and the data length each returned
# on UM12947 (firmware 11.0CB).
_OFFSETS = {
    SUB_POLL:   0x0030,   # 59 B  — the one offset THOR treats as a constant
    SUB_SERIAL: 0x000A,   # 21 B
}

# Data-section lengths observed, for orientation only — deliberately NOT
# asserted.  `SUB 0x1C` is 4 bytes longer on the Thor firmware line (0x30 vs
# 0x2C declared), so a length check here would fire spuriously on half the
# fleet.  See the protocol reference, "A/B: Blastware build vs Thor build".
OBSERVED_DATA_LEN = {
    SUB_STORAGE_RANGE: 47,   SUB_EVENT_INDEX: 101,  SUB_MONITOR_LOG: 297,
    SUB_EVENT_RECORD: 221,   SUB_SERIAL: 21,        SUB_COMPLIANCE_CONFIG: 2103,
    SUB_MONITOR_STATUS: 55,  SUB_EVENT_FIRST: 19,   SUB_EVENT_NEXT: 19,
    SUB_CALL_HOME_CONFIG: 137, SUB_TRIGGER_CONFIG: 39,
    SUB_SETUP_FIRST: 266,    SUB_SETUP_NEXT: 266,   SUB_SETUP_ACTIVE: 266,
    SUB_STATE: 16,           SUB_POLL: 59,          SUB_ARM_EVENT: ACK_DATA_LEN,
}

# `1E`/`1F` carry this at params[7].  Series III uses the same value to arm its
# bulk stream; here THOR sends it on every chain read, browse or download.
EVENT_TOKEN = 0xFE

# `SUB 0x5A` chunk size, in bytes of file payload per response.
CHUNK_SIZE = 1024

# Every `0x5A` response prefixes the file bytes with 11 bytes of header.
_CHUNK_PREFIX = 11


# ── Exceptions ────────────────────────────────────────────────────────────────

class ProtocolError(Exception):
    """The device violated the expected protocol."""


class TimeoutError(ProtocolError):
    """No response arrived within the allowed time."""


class ChecksumError(ProtocolError):
    """A received frame failed its checksum."""


class UnexpectedResponse(ProtocolError):
    """The response SUB did not match the request."""


class ShortRead(ProtocolError):
    """A bulk download returned fewer bytes than the device promised."""


# ── Params builders ───────────────────────────────────────────────────────────

def token_params(token: int = EVENT_TOKEN) -> bytes:
    """`1E`/`1F`: the token sits at params[7]."""
    return bytes(7) + bytes([token]) + bytes(2)


def key_params(key4: bytes) -> bytes:
    """`0x0C`: the full 4-byte event key at params[4:8]."""
    if len(key4) != 4:
        raise ValueError(f"key4 must be 4 bytes, got {len(key4)}")
    return bytes(4) + key4 + bytes(2)


def key_lo_params(key4: bytes) -> bytes:
    """`0x0A`: only the key's **low two bytes**, at params[6:8].

    ⚠ Inferred from a single key value.  All nine captured `0x0A` frames carry
    `4a 81`, and the event key in play was `055d4a81` — so this is consistent
    with "the low half of the current key" and equally consistent with "a
    cursor handle that happened to equal it".  Both readings produce the same
    bytes for that key, so one event cannot separate them.

    It does not matter much in practice: the walk works with the same params
    repeated, so whichever it is, passing the current key is right.
    """
    if len(key4) != 4:
        raise ValueError(f"key4 must be 4 bytes, got {len(key4)}")
    return bytes(6) + key4[2:4] + bytes(2)


def chunk_params(key4: bytes, byte_offset: int) -> bytes:
    """`0x5A`: the key opens the file, then a byte offset walks it.

    Chunk 0 carries the event key at params[0:4] — that is what says "from the
    beginning".  Later chunks carry a uint16 BE byte offset at params[2:4].
    """
    if byte_offset == 0:
        if len(key4) != 4:
            raise ValueError(f"key4 must be 4 bytes, got {len(key4)}")
        return key4 + bytes(6)
    if not 0 <= byte_offset <= 0xFFFF:
        raise ValueError(f"byte_offset must fit in uint16, got {byte_offset}")
    return bytes(2) + struct.pack(">H", byte_offset) + bytes(6)


# ── Protocol ──────────────────────────────────────────────────────────────────

class MicromateProtocol:
    """Wire-level command set for one open connection to a Micromate.

    Does not own the transport; lifetime belongs to the client.

        proto = MicromateProtocol(transport)
        proto.poll()
        serial = proto.read_serial()
    """

    def __init__(
        self,
        transport: BaseTransport,
        recv_timeout: float = DEFAULT_RECV_TIMEOUT,
        strict_checksums: bool = True,
    ) -> None:
        """
        Args:
            strict_checksums: raise on a bad checksum.  **Defaults to True,
                unlike the Series III sibling**, which logs and continues
                because its parser cannot reliably tell an inner-frame
                delimiter from a checksum byte.  That excuse does not apply
                here: the Micromate rule is plain SUM8 over the de-stuffed
                payload and it holds on 251 of 251 captured frames, so a
                mismatch means something real — line noise, a desync, or a rule
                we have wrong — and all three are worth hearing about.

                The lenient Series III default is instructive: it hid the fact
                that the documented checksum rule was wrong for two days.  Set
                False only to get a field diagnosis unstuck.
        """
        self._transport = transport
        self._recv_timeout = recv_timeout
        self._strict = strict_checksums
        self._parser = MicromateFrameParser()
        self._pending: list[MicromateFrame] = []

    # ── Identity and state ────────────────────────────────────────────────────

    def poll(self) -> MicromateFrame:
        """`0x5B` → `0xA4`.  Handshake; carries the ID block and model string.

        Every captured session opens with this and nothing before it.
        """
        return self._exchange(SUB_POLL)

    def read_serial(self) -> bytes:
        """`0x15` → `0xEA`.  ASCII, null-terminated — e.g. `UM12947`."""
        return self._read(SUB_SERIAL)

    def read_device_info(self) -> bytes:
        """`0x01` → `0xFE`.  Firmware, calibration, per-channel float block.

        ⚠ THOR never sends this in any captured session, so the `0xFFFF` offset
        is from our own 2026-09-23 probes rather than from THOR's behaviour.  It
        answered correctly on both firmware lines, but it is the one read here
        with no THOR frame behind it.
        """
        return self._read(SUB_DEVICE_INFO)

    def read_state(self) -> bytes:
        """`0x49` → `0xB6`.  A cheap monitoring check; 16 B.

        ⚠ Test `data[11]` for **non-zero**, never against a constant — it has
        read both `0x0E` and `0x0C` while monitoring.
        """
        return self._read(SUB_STATE)

    def read_monitor_status(self) -> bytes:
        """`0x1C` → `0xE3`.  Flag, **device clock**, battery, memory.

        ⚠ Parse **forward** from the declared length, never backward from the
        end.  This block is 4 bytes longer on the Thor firmware line, and Series
        III's relative-to-end offsets yield a battery voltage of 577.92 V on a
        `11.0BD` unit.
        """
        return self._read(SUB_MONITOR_STATUS)

    def read_storage_range(self) -> bytes:
        """`0x06` → `0xF9`.  Event storage extent; 47 B."""
        return self._read(SUB_STORAGE_RANGE)

    def read_event_index(self) -> bytes:
        """`0x08` → `0xF7`.  101 B.  Contents not yet mapped."""
        return self._read(SUB_EVENT_INDEX)

    def read_trigger_config(self) -> bytes:
        """`0x2E` → `0xD1`.  39 B.  Series IV only; no Series III equivalent."""
        return self._read(SUB_TRIGGER_CONFIG)

    def read_compliance_config(self) -> bytes:
        """`0x1A` → `0xE5`.  The whole active setup — 2103 B on UM12947.

        One response.  Series III needs a 4-frame sequence for the same thing.
        """
        return self._read(SUB_COMPLIANCE_CONFIG)

    def read_call_home_config(self) -> bytes:
        """`0x2C` → `0xD3`.  137 B — Series III's is 124, so do not reuse its map."""
        return self._read(SUB_CALL_HOME_CONFIG)

    # ── Setups ────────────────────────────────────────────────────────────────

    def read_active_setup_name(self) -> bytes:
        """`0x41` → `0xBE`.  266 B; carries the active `.MMB` name."""
        return self._read(SUB_SETUP_ACTIVE)

    def read_first_setup(self) -> bytes:
        """`0x3F` → `0xC0`.  Head of the setup-file list."""
        return self._read(SUB_SETUP_FIRST)

    def read_next_setup(self) -> bytes:
        """`0x40` → `0xBF`.  Repeat until the record carries an empty name.

        Stateful: the device holds the cursor, so the same request walks the
        list.  22 of these appear back to back in one captured session.
        """
        return self._read(SUB_SETUP_NEXT)

    # ── Event chain ───────────────────────────────────────────────────────────

    def arm_event(self) -> MicromateFrame:
        """`0x93` → `0x6C`.  THOR sends this before **every** `1E`/`1F`.

        It replaces Series III's `1E(token=0xFE)` arming step.  No params, no
        offset payload — an 11-byte ack.

        ⚠ Whether a unit actually requires it is untested.  Do it because it is
        known-good, not because it is known-necessary.
        """
        return self._exchange(SUB_ARM_EVENT, offset=READ_ALL)

    def read_event_first(self) -> bytes:
        """`0x1E` → `0xE1`.  First event key + size; 19 B."""
        return self._read(SUB_EVENT_FIRST, params=token_params())

    def read_event_next(self) -> bytes:
        """`0x1F` → `0xE0`.  Next key + size, or the all-zero null sentinel."""
        return self._read(SUB_EVENT_NEXT, params=token_params())

    def read_event_record(self, key4: bytes) -> bytes:
        """`0x0C` → `0xF3`.  221 B — project, client, operator, timestamp, peaks.

        ⚠ The peak float in here runs 2–5% above `max(T,V,L)` and is **not** the
        vector sum; its offset was inferred, not established.  Prefer decoded
        samples.
        """
        return self._read(SUB_EVENT_RECORD, params=key_params(key4))

    def read_monitor_log_next(self, key4: bytes) -> Optional[bytes]:
        """`0x0A` → `0xF5`.  One monitor-log record, or None at end of list.

        ⚠ Not the keyed single read the spec describes.  This is a **walk**:
        the same request repeated, the device advancing its own cursor, each
        response a 297-byte record carrying serial, mode and thresholds.  The
        list ends with a bare 11-byte ack — nine captured frames, eight records
        then the terminator.

        Series III reaches the same data through a record-type discriminator on
        its event walk (`0x2C` partial vs `0x46` full).  Here it is a separate
        cursor and the event chain does not see it at all.
        """
        data = self._read(SUB_MONITOR_LOG, params=key_lo_params(key4))
        return None if len(data) <= ACK_DATA_LEN else data

    # ── Bulk download ─────────────────────────────────────────────────────────

    def read_event_file(self, key4: bytes, size: int) -> bytes:
        """`0x5A` → `0xA5`.  The `.IDFW`/`.IDFH` file, byte for byte.

        `size` is the 4 bytes after the key in the `1E`/`1F` response.  Returns
        exactly that many bytes, or raises `ShortRead`.

        A bounded chunk walk — `ceil(size / 1024)` requests, each asking for
        `min(1024, remaining)` bytes:

            offset       = the byte count wanted (NOT an address)
            params       = the key on chunk 0, then a uint16 BE byte offset
            response     = exactly `offset + 11` bytes; file bytes are data[11:]

        Verified against THOR on all six bench events (4,076 → 13,424 B):
        `sum(offsets) == size` exactly, every time.

        ⚠ Do not port the Series III `5A` walk.  Its address arithmetic caused a
        5x over-read and a `>64 KB` page-boundary bug that is *still open* on
        that side.  Neither applies here — the cursor is a byte offset into the
        file, bounded by a size the device supplied, so it cannot run past the
        event.

        The result feeds `micromate.idf_file.read_idf_file()` and
        `/db/import/idf_file` unchanged; no new codec work is needed.
        """
        if size <= 0:
            raise ValueError(f"size must be positive, got {size}")

        out = bytearray()
        n_chunks = math.ceil(size / CHUNK_SIZE)
        for i in range(n_chunks):
            want = min(CHUNK_SIZE, size - i * CHUNK_SIZE)
            data = self._read(
                SUB_BULK_DOWNLOAD,
                offset=want,
                params=chunk_params(key4, i * CHUNK_SIZE),
            )
            if len(data) < _CHUNK_PREFIX:
                raise ShortRead(
                    f"chunk {i + 1}/{n_chunks} of {key4.hex()}: "
                    f"{len(data)} B is too short to hold a chunk header"
                )
            body = data[_CHUNK_PREFIX:]
            if len(body) != want:
                # Worth being loud: a silently short event is the failure mode
                # this project has been bitten by repeatedly on the Series III
                # side, and here the expected length is known up front.
                raise ShortRead(
                    f"chunk {i + 1}/{n_chunks} of {key4.hex()}: asked for "
                    f"{want} B, got {len(body)}"
                )
            out += body

        if len(out) != size:
            raise ShortRead(
                f"{key4.hex()}: assembled {len(out)} B, device promised {size}"
            )
        log.debug("downloaded %s: %d B in %d chunks", key4.hex(), len(out), n_chunks)
        return bytes(out)

    # ── Plumbing ──────────────────────────────────────────────────────────────

    def _read(
        self,
        sub: int,
        *,
        params: bytes = bytes(10),
        offset: Optional[int] = None,
        timeout: Optional[float] = None,
    ) -> bytes:
        """Send one read command, return the response's data section."""
        return self._exchange(sub, params=params, offset=offset, timeout=timeout).data

    def _exchange(
        self,
        sub: int,
        *,
        params: bytes = bytes(10),
        offset: Optional[int] = None,
        timeout: Optional[float] = None,
    ) -> MicromateFrame:
        if offset is None:
            offset = _OFFSETS.get(sub, READ_ALL)
        # Start every exchange clean: drop any half-frame and any frame left
        # stashed by the last one.  This is a strict request/response protocol,
        # so anything already buffered when we send is by definition stale, and
        # `expected_sub` would reject it anyway — better to discard it here than
        # to raise a confusing UnexpectedResponse one command later.
        self._parser.reset()
        self._pending.clear()
        self._send(build_request(sub, offset, params))
        return self._recv_one(expected_sub=0xFF - sub, timeout=timeout,
                              reset_parser=False)

    def _send(self, frame: bytes) -> None:
        log.debug("TX %d bytes: %s", len(frame), frame.hex())
        self._transport.write(frame)

    def _recv_one(
        self,
        expected_sub: Optional[int] = None,
        timeout: Optional[float] = None,
        reset_parser: bool = True,
    ) -> MicromateFrame:
        """Read until one complete frame is parsed."""
        deadline = time.monotonic() + (timeout or self._recv_timeout)
        if reset_parser:
            self._parser.reset()
            self._pending.clear()

        if self._pending:
            return self._validate(self._pending.pop(0), expected_sub)

        while time.monotonic() < deadline:
            chunk = self._transport.read(4096)
            if not chunk:
                time.sleep(0.005)
                continue
            log.debug("RX %d bytes", len(chunk))
            frames = self._parser.feed(chunk)
            if frames:
                self._pending.extend(frames[1:])
                return self._validate(frames[0], expected_sub)

        raise TimeoutError(
            f"no frame in {timeout or self._recv_timeout:.1f}s"
            + (f" (expected SUB 0x{expected_sub:02X})" if expected_sub is not None else "")
            + f"; {self._parser.bytes_fed} bytes were received"
            # That byte count is the whole point: it separates "nothing came
            # back at all" from "bytes arrived but never framed", and those have
            # completely different causes.  It earned its keep on Series III.
        )

    def _validate(
        self, frame: MicromateFrame, expected_sub: Optional[int]
    ) -> MicromateFrame:
        if not frame.checksum_valid:
            msg = (
                f"SUB 0x{frame.sub:02X}: checksum mismatch "
                f"(got 0x{frame.chk_byte:02X}, {len(frame.data)} B data)"
            )
            if self._strict:
                raise ChecksumError(msg)
            log.warning("%s — continuing (strict_checksums=False)", msg)
        if expected_sub is not None and frame.sub != expected_sub:
            raise UnexpectedResponse(
                f"expected SUB 0x{expected_sub:02X}, got 0x{frame.sub:02X}"
            )
        return frame