"""The write pipeline: every packet write is one transaction through `packet_write`.

Inside one transaction: lock the packet row (SELECT ... FOR UPDATE), build the policy's PacketState, check the
caller's expected step (409 stale_step), check the packet version when If-Match is given (409 version_conflict),
ask the policy (403, 400 or 422 with the decision's code), take the signature when the rule needs one, hand the caller a
`Write`, then bump the version, write the packet_log row, the transition row and its side effects, the audit row and
the NOTIFY. The policy decides; a handler never does.

A wrong signature secret is the one failure that commits: the step-up failure count and the attempt row must stay,
so the three-strike rule works. Nothing else has been written at that point.

Child-row endpoints build on the same pieces: `check_row_version`, `next_counter`, `apply_field_cas`, `parse_if_match`.
"""

from __future__ import annotations

import contextlib
import hashlib
import hmac
import logging
import os
import tempfile
from collections.abc import Iterator, Mapping, Sequence
from contextlib import contextmanager
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Literal

from fastapi import Request
from psycopg.types.json import Jsonb
from pydantic import BaseModel, Field

from .. import audit, events, policy
from ..api import deps
from ..api.errors import ApiError
from ..auth import signatures
from ..auth.signatures import Signature
from ..policy.engine import MSG_FILED
from ..settings import SecretFileError
from ..text import LIMITS, clean_opt, reason_ok
from . import checklists, packets
from . import qc as qc_dom

log = logging.getLogger(__name__)

A = policy.Action

MSG_STALE = "Someone else already took this step."
MSG_VERSION = "The packet changed since you opened it. Reload and try again."
MSG_ROW = "Someone else changed this line. Reload and try again."
MSG_FIELD = "Someone else changed this since you opened it."
MSG_DATABOOK = "The data book could not be built: {reason}. Nothing was filed."


# Codes that answer 400 (the UI asks for input and retries); every other refusal answers 403.
ASK_CODES = frozenset({"it_reason_required", "reason_required"})

COUNTERS = {"weld": "next_weld_no", "heat": "next_heat_no", "page": "next_page_no", "co": "next_co_no"}

# The packet_log label per action, when the caller gives none.
LABELS: dict[policy.Action, str] = {
    A.SEND_TO_WAREHOUSE: "Sent to warehouse",
    A.RELEASE_TO_SHOP: "Sent straight to the shop",
    A.SEND_DRAFT_TO_QC: "Sent straight to Q.C.",
    A.WH_SEND_BACK: "Sent back to Clerical",
    A.RETURN_TO_CLERICAL: "Sent back to Clerical",
    A.WH_RELEASE: "Released to supervisor",
    A.SEND_BACK_TO_WAREHOUSE: "Sent back to the warehouse",
    A.ASSIGN: "Sent to a station",
    A.UNASSIGN: "Taken off the station",
    A.PULL_BACK: "Pulled back from the station",
    A.START: "Work started",
    A.SUBMIT: "Submitted to supervisor",
    A.RETURN_TO_STATION: "Returned to the station",
    A.SEND_TO_QC: "Sent to Q.C.",
    A.ROUTE_FROM_REVIEW: "Routed to another department",
    A.QC_REJECT: "Q.C. rejected",
    A.QC_ACCEPT: "Q.C. accepted",
    A.QC_ACCEPT_AND_ROUTE: "Q.C. accepted and routed",
    A.FILE: "Filed in the data book",
    A.ADMIN_REOPEN: "Reopened by IT",
    A.EDIT_HEADER: "Details changed",
    A.EDIT_DRAWING_REF: "Drawing number changed",
    A.EDIT_DEPT: "Department changed",
    A.MOVE_UNIT: "Moved to another unit",
    A.EDIT_WOS: "Work orders changed",
    A.EDIT_DOCUMENT_SET: "Drawing attached by hand",
    A.DOC_ADD: "Document added",
    A.DOC_REMOVE: "Document removed",
    A.SET_VCLOSED: "Job closed in VISUAL",
    A.SET_DATABOOK_AT: "Data book date set",
    A.REMOVE: "Packet removed",
}

AUDIT_ACTIONS: dict[policy.Action, str] = {A.REMOVE: "packet.removed", A.MOVE_UNIT: "packet.moved"}


# ---------------------------------------------------------------- request bodies


class SignBody(BaseModel):
    factor: Literal["pin", "password"]
    secret: str = Field(max_length=1024)


class Expect(BaseModel):
    status: str = Field(max_length=20)
    dept: str = Field(max_length=10)


# ---------------------------------------------------------------- the Write object


@dataclass
class Write:
    conn: Any  # the request connection, inside one transaction
    principal: deps.Principal  # the session principal
    policy_principal: policy.Principal
    packet: dict[str, Any]  # the packets row, locked FOR UPDATE
    state: policy.PacketState
    decision: policy.Decision
    signature: Signature | None
    version: int  # the new version after the bump (set on exit)
    action: policy.Action
    extra: Mapping[str, Any]
    it_reason: str | None  # the cleaned IT reason, kept only when the admin bypass was used
    request: Request
    label: str | None = None
    note: str | None = None
    fields: list[str] = field(default_factory=list)
    detail: dict[str, Any] = field(default_factory=dict)
    transitioned: bool = False
    transition_id: int | None = None
    noop: bool = False
    from_status: str = ""
    from_dept: str = ""
    children: Any = None  # packets.Children loaded under the lock (full=False)
    more_logs: list[tuple[str, str | None]] = field(default_factory=list)

    @property
    def id(self) -> int:
        return int(self.packet["id"])

    @property
    def user_id(self) -> Any:
        return self.principal.user_id

    @property
    def rule(self) -> policy.Rule:
        return policy.RULES[self.action]

    @property
    def settings(self) -> Any:
        return _settings(self)

    @property
    def actor_ref(self) -> Any:
        """The signed-in person as the PDF builders' WhoRef: id, display name and employee number."""
        from . import prints

        return prints.who_of(self.principal)

    def log(self, action_label: str, note: str | None = None) -> None:
        """Override the packet_log label (and note) for this write."""
        self.label = action_label
        if note is not None:
            self.note = note

    def log_also(self, action_label: str, note: str | None = None) -> None:
        """One more packet_log line for this write, written after the main one (same user, no signature)."""
        self.more_logs.append((action_label, note))

    def changed(self, *names: str) -> None:
        """Record the fields this write changed (they go into the audit detail)."""
        for n in names:
            if n not in self.fields:
                self.fields.append(n)

    def skip(self) -> None:
        """Nothing changed: no version bump, no log, audit or event."""
        self.noop = True

    def check(self, action: policy.Action, extra: Mapping[str, Any] | None = None) -> policy.Decision:
        """Check one more action on the same locked packet (for a write that touches several rules)."""
        d = policy.check(self.policy_principal, self.state, action, extra=extra or self.extra, it_reason=self.it_reason)
        refuse(d)
        return d


# ---------------------------------------------------------------- helpers for callers


def refuse(decision: policy.Decision) -> None:
    """Raise the API error for a failed policy decision."""
    if decision.ok:
        return
    status = 400 if decision.code in ASK_CODES else 422 if decision.code == "ncr_required" else 403
    raise ApiError(status, decision.code, decision.why)


def current_of(row: Mapping[str, Any]) -> dict[str, Any]:
    return {"status": str(row["status"]), "dept": str(row["dept_code"]), "version": int(row["version"])}


def parse_if_match(request: Request) -> int | None:
    """The If-Match header as a plain integer (quotes and a W/ prefix are tolerated), or None when absent."""
    raw = request.headers.get("if-match")
    if raw is None:
        return None
    text = raw.strip().removeprefix("W/").strip().strip('"')
    try:
        return int(text)
    except ValueError:
        raise ApiError(400, "bad_if_match", "If-Match must be a version number.") from None


def require_if_match(request: Request) -> int:
    v = parse_if_match(request)
    if v is None:
        raise ApiError(428, "if_match_required", "Send If-Match with the version you started from.")
    return v


def check_row_version(row: Mapping[str, Any] | None, if_match: int | None, *, current: Any = None) -> None:
    """409 row_conflict with the current row when its row_version differs from If-Match.

    `current` is what goes into the error (defaults to the row itself, JSON-shaped by the caller if needed).
    A missing If-Match is 428 if_match_required.
    """
    if row is None:
        raise ApiError(404, "not_found", "No such line.")
    if if_match is None:
        raise ApiError(428, "if_match_required", "Send If-Match with the version you started from.")
    if int(row["row_version"]) != int(if_match):
        raise ApiError(
            409, "row_conflict", MSG_ROW, extra={"current": jsonable(current if current is not None else row)}
        )


def next_counter(conn: Any, packet_id: int, kind: str, n: int = 1) -> int:
    """Take `n` consecutive numbers from a packet counter (weld, heat, page, co); returns the first one.

    Call it inside packet_write: the packet row is locked FOR UPDATE, so concurrent writers serialise on it.
    Outside a pipeline the UPDATE itself takes the row lock for the rest of the transaction.
    """
    col = COUNTERS.get(kind)
    if col is None:
        raise ValueError(f"unknown counter {kind!r}")
    if n < 1:
        raise ValueError("n must be at least 1")
    row = conn.execute(
        f"UPDATE packets SET {col} = {col} + %s WHERE id = %s RETURNING {col} - %s",  # noqa: S608 (col from COUNTERS)
        (n, packet_id, n),
    ).fetchone()
    if row is None:
        raise ApiError(404, "not_found", "No such packet.")
    return int(row[0])


def _norm(value: Any) -> Any:
    """Comparable form of a value: uuid and dates as text, numbers as numbers, '' as None."""
    if value is None or value == "":
        return None
    if isinstance(value, bool | int | float | str):
        return value
    return str(value)


def apply_field_cas(
    current: Mapping[str, Any], set_: Mapping[str, Any], base: Mapping[str, Any] | None
) -> dict[str, Any]:
    """Field-level compare-and-set. For every key in set_ that base also has, base must equal current.

    Conflicts raise 409 field_conflict with `current: {key: value}` for the conflicting keys. Keys without a base
    entry are written without a check (the old merge3: mine wins). Returns the keys whose value actually changes.
    """
    base = base or {}
    conflicts = {k: current.get(k) for k in set_ if k in base and _norm(base[k]) != _norm(current.get(k))}
    if conflicts:
        raise ApiError(409, "field_conflict", MSG_FIELD, extra={"current": jsonable(conflicts)})
    return {k: v for k, v in set_.items() if _norm(v) != _norm(current.get(k))}


def jsonable(value: Any) -> Any:
    from fastapi.encoders import jsonable_encoder

    return jsonable_encoder(value)


# ---------------------------------------------------------------- the pipeline


@contextmanager
def packet_write(
    d: deps.Db,
    p: deps.Principal,
    packet_id: int,
    action: policy.Action,
    *,
    request: Request,
    extra: Mapping[str, Any] | None = None,
    it_reason: str | None = None,
    sign: SignBody | None = None,
    expect: Expect | None = None,
    sign_content: Any = None,
    if_match: int | None = None,
    also: Sequence[policy.Action] = (),
    require_sign: bool | None = None,
    policy_principal: policy.Principal | None = None,
) -> Iterator[Write]:
    """One packet write. See the module docstring for the order of steps.

    `also` lists more actions the same write needs (each is checked; the first action is the one logged).
    `require_sign` overrides the rule's signature: False skips it (removing a hand-attached drawing), True forces it.
    """
    conn = d.conn
    extra = dict(extra or {})
    pp = policy_principal or packets.policy_principal_for(conn, p)
    failure: ApiError | None = None
    with conn.transaction():
        row = packets.load_row(conn, packet_id, lock=True)
        if row is None:
            raise ApiError(404, "not_found", "No such packet.")
        ch = packets.load_children(conn, row, full=False)
        state = packets.state_from(row, ch)
        if expect is not None and (expect.status != row["status"] or expect.dept != row["dept_code"]):
            raise ApiError(409, "stale_step", MSG_STALE, extra={"current": current_of(row)})
        extra.setdefault("holder_name", packets.holder_text(state, ch))
        rule = policy.RULES[action]
        if not state.removed and state.status == "filed" and not rule.filed_ok:
            # Say "filed" rather than "wrong status" or "give an IT reason": nothing but a reopen changes it.
            raise ApiError(403, "filed", MSG_FILED)
        cleaned_it = reason_ok(it_reason)
        decision = policy.check(pp, state, action, extra=extra, it_reason=it_reason)
        refuse(decision)
        bypass = decision.admin_bypass
        for other in also:
            dd = policy.check(pp, state, other, extra=extra, it_reason=it_reason)
            refuse(dd)
            bypass = bypass or dd.admin_bypass
        if if_match is not None and int(if_match) != int(row["version"]):
            raise ApiError(409, "version_conflict", MSG_VERSION, extra={"current": current_of(row)})
        w = Write(
            conn=conn,
            principal=p,
            policy_principal=pp,
            packet=row,
            state=state,
            decision=decision,
            signature=None,
            version=int(row["version"]),
            action=action,
            extra=extra,
            it_reason=cleaned_it if bypass else None,
            request=request,
            from_status=str(row["status"]),
            from_dept=str(row["dept_code"]),
            children=ch,
        )
        meaning = decision.signature
        needs = bool(meaning) if require_sign is None else require_sign
        if needs:
            if sign is None:
                raise ApiError(
                    400,
                    "signature_required",
                    "This step needs your signature.",
                    extra={"meaning": meaning or LABELS.get(action, str(action))},
                )
            try:
                w.signature = signatures.sign(
                    conn,
                    deps.directory_of(request),
                    p.actor,
                    factor=sign.factor,
                    secret=sign.secret,
                    action=f"packet.{action}",
                    meaning=meaning,
                    packet_id=packet_id,
                    subject_type="packet",
                    subject_id=packet_id,
                    content=sign_content
                    if sign_content is not None
                    else {"action": str(action), "packet_id": packet_id, "version": int(row["version"])},
                    ip=p.ip,
                    settings=deps.settings_of(request),
                )
            except ApiError as e:
                failure = e  # commit the step-up failure records, then raise below
        if failure is None:
            yield w
            _finish(w)
    if failure is not None:
        raise failure


def _finish(w: Write) -> None:
    if w.noop:
        return
    if w.rule.transition and not w.transitioned:
        apply_transition(w)
    conn = w.conn
    w.version = int(
        conn.execute("UPDATE packets SET version = version + 1 WHERE id = %s RETURNING version", (w.id,)).fetchone()[0]
    )
    after = conn.execute("SELECT status::text, dept_code FROM packets WHERE id = %s", (w.id,)).fetchone()
    status, dept = str(after[0]), str(after[1])
    label = w.label or LABELS.get(w.action, str(w.action).replace("_", " ").capitalize())
    note = clean_opt(w.note, LIMITS["note"]) if w.note else None
    sig_id = w.signature.id if w.signature else None
    conn.execute(
        "INSERT INTO packet_log (packet_id, by, by_name, role, action, note, it_reason, signature_id, transition_id)"
        " VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s)",
        (
            w.id,
            w.user_id,
            w.principal.user["display_name"],
            w.principal.role_snapshot,
            label,
            note,
            w.it_reason,
            sig_id,
            w.transition_id,
        ),
    )
    for extra_label, extra_note in w.more_logs:
        conn.execute(
            "INSERT INTO packet_log (packet_id, by, by_name, role, action, note, it_reason)"
            " VALUES (%s, %s, %s, %s, %s, %s, %s)",
            (
                w.id,
                w.user_id,
                w.principal.user["display_name"],
                w.principal.role_snapshot,
                extra_label,
                clean_opt(extra_note, LIMITS["note"]) if extra_note else None,
                w.it_reason,
            ),
        )
    detail: dict[str, Any] = {"from": w.from_status, "to": status, "dept": dept}
    if w.from_dept != dept:
        detail["from_dept"] = w.from_dept
    if w.fields:
        detail["fields"] = w.fields
    if note:
        detail["note"] = note
    if sig_id:
        detail["signature_id"] = sig_id
    detail.update(w.detail)
    audit.append(
        conn,
        action=AUDIT_ACTIONS.get(w.action, f"packet.{w.action}"),
        user_id=w.user_id,
        session_id=w.principal.session_id,
        role_snapshot=w.principal.role_snapshot,
        subject_type="packet",
        subject_id=w.id,
        packet_id=w.id,
        detail=detail,
        it_reason=w.it_reason,
        ip=w.principal.ip,
    )
    events.publish(conn, {"event": "changed", "packet_id": w.id, "version": w.version, "status": status, "dept": dept})


# ---------------------------------------------------------------- transitions and their side effects


CLOCK_STOP = (
    "clock_elapsed_ms = clock_elapsed_ms + CASE WHEN clock_running_since IS NULL THEN 0"
    " ELSE (extract(epoch FROM (now() - clock_running_since)) * 1000)::bigint END, clock_running_since = NULL"
)


def _reason(w: Write) -> str | None:
    return reason_ok(w.extra.get("reason"))


def _note(w: Write) -> str | None:
    return clean_opt(w.extra.get("note"), LIMITS["note"])


def _wh_incoming(w: Write) -> None:
    w.conn.execute("UPDATE packet_wh SET closed_at = now() WHERE packet_id = %s AND closed_at IS NULL", (w.id,))
    w.conn.execute(
        "INSERT INTO packet_wh (packet_id, stage, by, note) VALUES (%s, 'incoming', %s, %s)",
        (w.id, w.user_id, _note(w)),
    )


def _wh_close(w: Write) -> None:
    w.conn.execute("UPDATE packet_wh SET closed_at = now() WHERE packet_id = %s AND closed_at IS NULL", (w.id,))


def _open_stage(w: Write, dept: str) -> None:
    w.conn.execute("INSERT INTO packet_stages (packet_id, dept_code) VALUES (%s, %s)", (w.id, dept))


def _close_stage(w: Write, qc_snapshot: Any = None) -> None:
    w.conn.execute(
        f"UPDATE packet_stages SET {CLOCK_STOP}, closed_at = now(), qc_snapshot = coalesce(%s, qc_snapshot),"  # noqa: S608
        " row_version = row_version + 1 WHERE packet_id = %s AND closed_at IS NULL",
        (None if qc_snapshot is None else Jsonb(jsonable(qc_snapshot)), w.id),
    )


def _stage_update(w: Write, assignments: str, params: Sequence[Any] = ()) -> None:
    w.conn.execute(
        f"UPDATE packet_stages SET {assignments}, row_version = row_version + 1"  # noqa: S608 (fixed fragments)
        " WHERE packet_id = %s AND closed_at IS NULL",
        (*params, w.id),
    )


def _open_inspection(w: Write) -> dict[str, Any] | None:
    return packets.one(w.conn, "SELECT * FROM qc_inspections WHERE packet_id = %s AND closed_at IS NULL", (w.id,))


def _close_inspection(w: Write, insp: Mapping[str, Any] | None, dept: str) -> None:
    """Close the open inspection; when it had a result, keep it in qc_history."""
    if insp is None:
        return
    w.conn.execute(
        "UPDATE qc_inspections SET closed_at = now(), row_version = row_version + 1 WHERE id = %s", (insp["id"],)
    )
    if insp.get("result"):
        w.conn.execute(
            "INSERT INTO qc_history (packet_id, result, inspector, note, dept_code, snapshot)"
            " VALUES (%s, %s, %s, %s, %s, %s)",
            (w.id, insp["result"], insp.get("inspector"), insp.get("result_note"), dept, Jsonb(jsonable(dict(insp)))),
        )


def _set_result(w: Write, insp: Mapping[str, Any] | None, result: str, note: str | None) -> dict[str, Any] | None:
    if insp is None:
        return None
    return packets.one(
        w.conn,
        "UPDATE qc_inspections SET result = %s, result_at = now(), result_by = %s, result_note = %s,"
        " signature_id = %s, row_version = row_version + 1 WHERE id = %s RETURNING *",
        (result, w.user_id, note, w.signature.id if w.signature else None, insp["id"]),
    )


def _set_ncr(w: Write, insp: Mapping[str, Any] | None) -> None:
    """The NCR number the step carries (a reject, or the accept after a reject without one), on the inspection."""
    ncr = w.extra.get("ncr") or None
    if insp is not None and (ncr or w.action is A.QC_REJECT):
        w.conn.execute("UPDATE qc_inspections SET ncr = %s WHERE id = %s", (ncr, insp["id"]))


def _set_packet(w: Write, assignments: str, params: Sequence[Any] = ()) -> None:
    w.conn.execute(f"UPDATE packets SET {assignments} WHERE id = %s", (*params, w.id))  # noqa: S608 (fixed fragments)


def _settings(w: Write) -> Any:
    return deps.settings_of(w.request)


def seal_key_id(key: bytes) -> str:
    return hashlib.sha256(key).hexdigest()[:8]


def seal_hash(key: bytes, content: Any) -> bytes:
    return hmac.new(key, signatures.canonical_json(content), hashlib.sha256).digest()


def _seal_key(w: Write) -> bytes:
    try:
        key: bytes = _settings(w).seal_key()
    except SecretFileError as e:
        log.error("seal key unavailable: %s", e)
        raise ApiError(503, "server_misconfigured", "The server is missing its seal key.") from None
    return key


def qty_text(value: Any) -> str:
    """A quantity without trailing zeros: 4, 2.5."""
    if value is None:
        return "0"
    try:
        f = float(value)
    except (TypeError, ValueError):
        return str(value)
    return str(int(f)) if f.is_integer() else f"{f:g}"


def _release_text(w: Write) -> None:
    """The old release label and note.

    Label "Released to supervisor", or "... with {n} short"; note "{heats} heats recorded", plus " · SHORT: ..."
    when shorts are open.
    """
    lines = packets.rows(
        w.conn,
        "SELECT b.item, b.heat, s.qty_open, s.reason FROM bom_lines b LEFT JOIN bom_shorts s"
        " ON s.bom_line_id = b.id AND s.closed_at IS NULL WHERE b.packet_id = %s ORDER BY b.item",
        (w.id,),
    )
    heats = sum(1 for b in lines if str(b["heat"] or "").strip())
    shorts = [b for b in lines if b["qty_open"] is not None]
    note = f"{heats} heats recorded"
    if shorts:
        note += " · SHORT: " + ", ".join(
            f"item {b['item']} ×{qty_text(b['qty_open'])} ({b['reason'] or ''})" for b in shorts
        )
        w.log(f"{LABELS[A.WH_RELEASE]} with {len(shorts)} short", note)
    else:
        w.log(LABELS[A.WH_RELEASE], note)


def hours_text(ms: Any) -> str:
    """Stage clock hours with one decimal: 1.5 h."""
    return f"{int(ms or 0) / 3600000:.1f} h"


def _station_name(w: Write, station_id: Any) -> str | None:
    if station_id is None:
        return None
    ch = w.children
    if ch is not None and ch.station and ch.station.get("id") == station_id:
        return str(ch.station["name"])
    r = w.conn.execute("SELECT name FROM stations WHERE id = %s", (station_id,)).fetchone()
    return str(r[0]) if r else None


def _dept_text(w: Write, code: str) -> str:
    labels = getattr(w.children, "dept_labels", None) or packets.dept_labels(w.conn)
    return str(labels.get(code, code))


def _shop_texts(w: Write, a: policy.Action, to_dept: str, stamp: str | None = None) -> None:
    """The packet_log label and note of a shop step (the old click handlers' texts)."""
    ex = w.extra
    here = _station_name(w, w.packet["station_id"]) or "the station"
    note = _note(w)
    if a is A.ASSIGN:
        station = _station_name(w, int(ex["station_id"])) or "a station"
        r = w.conn.execute("SELECT display_name FROM users WHERE id = %s", (str(ex["welder_id"]),)).fetchone()
        who = str(r[0]) if r else ""
        w.log(f"Sent to {station}", f"{who} [{stamp}]" if stamp else who)
    elif a is A.UNASSIGN:
        w.log(f"Taken off {here}", note)
    elif a is A.PULL_BACK:
        w.log(f"Pulled back from {here}", note)
    elif a is A.START:
        w.log(LABELS[A.START], " · ".join(x for x in (here if w.packet["station_id"] else None, note) if x) or None)
    elif a is A.SUBMIT:
        r = w.conn.execute(
            "SELECT clock_elapsed_ms FROM packet_stages WHERE packet_id = %s AND closed_at IS NULL", (w.id,)
        ).fetchone()
        n = packets.dept_welds(w.packet, w.children) if w.children is not None else 0
        text = f"{n} welds · {hours_text(r[0] if r else 0)}"
        w.log(LABELS[A.SUBMIT], f"{text} · {note}" if note else text)
    elif a is A.RETURN_TO_STATION:
        w.log(f"Returned to {here}", _reason(w))
    elif a is A.SEND_TO_QC:
        loc = clean_opt(ex.get("location"), LIMITS["location"])
        w.log(LABELS[A.SEND_TO_QC], " · ".join(x for x in (f"Spool at {loc}" if loc else None, note) if x) or None)
    elif a is A.ROUTE_FROM_REVIEW:
        text = f"Supervisor, Q.C. skipped · from {_dept_text(w, w.from_dept)}"
        w.log(f"Routed to {_dept_text(w, to_dept)}", f"{text} · {note}" if note else text)


SHOP_TEXTS = frozenset(
    {A.ASSIGN, A.UNASSIGN, A.PULL_BACK, A.START, A.SUBMIT, A.RETURN_TO_STATION, A.SEND_TO_QC, A.ROUTE_FROM_REVIEW}
)
QC_TEXTS = frozenset({A.QC_ACCEPT, A.QC_ACCEPT_AND_ROUTE, A.QC_REJECT})


def apply_transition(w: Write) -> None:
    """Set status, status_at and dept, write the packet_transitions row and run the action's side effects."""
    if w.transitioned:
        return
    w.transitioned = True
    a = w.action
    rule = w.rule
    to_status = rule.to_status
    assert to_status is not None
    ex = w.extra
    reason = _reason(w)
    if a is A.QC_REJECT and reason and ex.get("ncr"):
        reason = f"{ex['ncr']} · {reason}"  # the supervisor's return note leads with the NCR number
    from_dept = w.from_dept
    to_dept = from_dept
    if rule.dept_change != "no" and isinstance(ex.get("dept"), str) and ex.get("dept"):
        to_dept = str(ex["dept"])

    stamp: str | None = None
    if a in SHOP_TEXTS and a is not A.ASSIGN and a is not A.SUBMIT:
        _shop_texts(w, a, to_dept)  # before the side effects clear the station
    if a in QC_TEXTS:
        qc_dom.qc_texts(w, a, to_dept)  # before the side effects close the inspection

    if a in (A.SEND_TO_WAREHOUSE, A.VIS_AUTO_RELEASE):
        _set_packet(w, "wh_skipped = false, wh_sent_at = now(), return_note = NULL")
        _wh_incoming(w)
    elif a is A.RELEASE_TO_SHOP:
        _set_packet(
            w,
            "wh_skipped = true, for_sup_id = %s, return_note = %s",
            (ex.get("for_sup_id") or None, _note(w)),
        )
        _close_stage(w)
        _open_stage(w, to_dept)
    elif a is A.SEND_DRAFT_TO_QC:
        _set_packet(w, "wh_skipped = true")
        _close_inspection(w, _open_inspection(w), from_dept)
        w.conn.execute(
            "INSERT INTO qc_inspections (packet_id, sent_by, sent_note) VALUES (%s, %s, %s)",
            (w.id, w.user_id, _note(w)),
        )
    elif a is A.WH_SEND_BACK:
        _set_packet(w, "return_note = %s", (reason,))
        _wh_close(w)
    elif a is A.RETURN_TO_CLERICAL:
        _set_packet(w, "return_note = %s", (reason,))
        _close_stage(w)
    elif a is A.WH_RELEASE:
        _release_text(w)
        _wh_close(w)
        _close_stage(w)
        _open_stage(w, to_dept)
    elif a is A.SEND_BACK_TO_WAREHOUSE:
        _set_packet(w, "return_note = %s, wh_skipped = false", (reason,))
        _close_stage(w)
        _wh_incoming(w)
    elif a is A.ASSIGN:
        station_id = int(ex["station_id"])
        welder_id = str(ex["welder_id"])
        stamp = clean_opt(ex.get("stamp"), LIMITS["stamp"])
        if stamp is None:
            r = w.conn.execute("SELECT welder_stamp FROM users WHERE id = %s", (welder_id,)).fetchone()
            stamp = r[0] if r else None
        _set_packet(w, "station_id = %s, welder_id = %s, welder_stamp = %s", (station_id, welder_id, stamp))
        if not packets.one(w.conn, "SELECT id FROM packet_stages WHERE packet_id = %s AND closed_at IS NULL", (w.id,)):
            _open_stage(w, from_dept)
        _stage_update(w, "station_id = %s, welder_id = %s, welder_stamp = %s", (station_id, welder_id, stamp))
        _shop_texts(w, a, to_dept, stamp)
    elif a in (A.UNASSIGN, A.PULL_BACK):
        _set_packet(w, "station_id = NULL, welder_id = NULL, welder_stamp = NULL")
        _stage_update(w, f"{CLOCK_STOP}, station_id = NULL, welder_id = NULL, welder_stamp = NULL")
    elif a is A.START:
        # A clock that is already running keeps its start; only the server sets it.
        _stage_update(
            w,
            "clock_running_since = coalesce(clock_running_since, now()),"
            " clock_started_at = coalesce(clock_started_at, now())",
        )
        # change C8: the stage keeps the checklist it started with
        checklists.freeze_on_start(w.conn, w.id)
    elif a is A.SUBMIT:
        _set_packet(w, "return_note = NULL")
        _stage_update(w, CLOCK_STOP)
        _shop_texts(w, a, to_dept)
    elif a is A.RETURN_TO_STATION:
        _set_packet(w, "return_note = %s", (reason,))
    elif a is A.SEND_TO_QC:
        _close_inspection(w, _open_inspection(w), from_dept)
        stage = packets.one(w.conn, "SELECT id FROM packet_stages WHERE packet_id = %s AND closed_at IS NULL", (w.id,))
        w.conn.execute(
            "INSERT INTO qc_inspections (packet_id, stage_id, sent_by, book, spool, location, sent_note)"
            " VALUES (%s, %s, %s, %s, %s, %s, %s)",
            (
                w.id,
                stage["id"] if stage else None,
                w.user_id,
                ex.get("book") is True,
                ex.get("spool") is True,
                clean_opt(ex.get("location"), LIMITS["location"]),
                _note(w),
            ),
        )
    elif a in (A.ROUTE_FROM_REVIEW, A.QC_ACCEPT_AND_ROUTE):
        insp = _open_inspection(w)
        if a is A.QC_ACCEPT_AND_ROUTE:
            _set_ncr(w, insp)
            insp = _set_result(w, insp, "accepted", _note(w))
        _close_stage(w, qc_snapshot=insp)
        _close_inspection(w, insp, from_dept)
        _open_stage(w, to_dept)
        _set_packet(w, "station_id = NULL, welder_id = NULL, welder_stamp = NULL, return_note = NULL, routed_to = NULL")
    elif a is A.QC_REJECT:
        # The reject closes the inspection into qc_history at once; the next SEND_TO_QC opens a fresh one.
        insp = _open_inspection(w)
        _set_ncr(w, insp)
        insp = _set_result(w, insp, "rejected", reason)
        _close_inspection(w, insp, from_dept)
        _set_packet(w, "return_note = %s", (reason,))
        if not packets.one(w.conn, "SELECT id FROM packet_stages WHERE packet_id = %s AND closed_at IS NULL", (w.id,)):
            _open_stage(w, from_dept)  # a draft sent straight to Q.C. has no stage yet
    elif a is A.QC_ACCEPT:
        insp = _open_inspection(w)
        _set_ncr(w, insp)
        insp = _set_result(w, insp, "accepted", _note(w))
        _close_inspection(w, insp, from_dept)
        _close_stage(w, qc_snapshot=insp)
        _set_packet(w, "routed_to = %s::route_kind", (str(ex["routed_to"]),))

    _set_packet(w, "status = %s::packet_status, status_at = now(), dept_code = %s", (to_status, to_dept))

    if a is A.FILE:
        _file(w)
    elif a is A.ADMIN_REOPEN:
        w.conn.execute(
            "UPDATE packet_seals SET broken_at = now(), broken_by = %s, broken_reason = %s"
            " WHERE packet_id = %s AND broken_at IS NULL",
            (w.user_id, reason, w.id),
        )

    tid = w.conn.execute(
        "INSERT INTO packet_transitions (packet_id, by, action, from_status, to_status, from_dept, to_dept, reason,"
        " signature_id, it_reason) VALUES (%s, %s, %s, %s::packet_status, %s::packet_status, %s, %s, %s, %s, %s)"
        " RETURNING id",
        (
            w.id,
            w.user_id,
            str(a),
            w.from_status,
            to_status,
            from_dept,
            to_dept,
            reason or _note(w),
            w.signature.id if w.signature else None,
            w.it_reason,
        ),
    ).fetchone()
    w.transition_id = int(tid[0])
    if w.note is None:
        w.note = reason or _note(w)


def _file(w: Write) -> None:
    """FILE: the data book date, the seal, and the data book built and stored on the seal, all in this transaction.

    A data book that cannot be built answers 500 databook_failed and the whole filing rolls back."""
    key = _seal_key(w)
    _set_packet(w, "databook_at = now()")
    row = packets.load_row(w.conn, w.id)
    assert row is not None
    content = packets.seal_content(w.conn, row)
    digest = seal_hash(key, content)
    kid = seal_key_id(key)
    seal_id, sealed_at = w.conn.execute(
        "INSERT INTO packet_seals (packet_id, hash, key_id, sealed_by, signature_id)"
        " VALUES (%s, %s, %s, %s, %s) RETURNING id, sealed_at",
        (w.id, digest, kid, w.user_id, w.signature.id if w.signature else None),
    ).fetchone()
    pages = _file_databook(w, row, {"hash": digest.hex(), "key_id": kid, "sealed_at": sealed_at}, int(seal_id))
    w.log_also("Data book filed", f"{pages} pages")
    w.detail["seal_id"] = int(seal_id)
    w.detail["databook_pages"] = pages


def _file_databook(w: Write, row: Mapping[str, Any], seal: dict[str, Any], seal_id: int) -> int:
    """Build the filed data book, store it as an asset and put it on the seal row. Returns its page count."""
    from ..pdf import databook
    from ..pdf.style import PdfError
    from . import assets
    from . import prints as prints_dom

    settings = _settings(w)
    try:
        built = databook.build(w.conn, settings, w.id, who=w.actor_ref, seal=seal, mode="filed")
    except PdfError as e:
        log.warning("data book for packet %s failed: %s", w.id, e)
        raise ApiError(500, "databook_failed", MSG_DATABOOK.format(reason=_reason_text(e))) from None
    read = packets.read_packet(w.conn, w.id, None, include_children=False)
    name = prints_dom.databook_name(read)
    tmp_dir = Path(settings.assets_dir) / "tmp"
    tmp_dir.mkdir(parents=True, exist_ok=True)
    fd, tmp_name = tempfile.mkstemp(prefix="databook-", suffix=".pdf", dir=tmp_dir)
    with os.fdopen(fd, "wb") as f:
        f.write(built.bytes)
    try:
        stored = assets.store_file(
            w.conn,
            settings,
            Path(tmp_name),
            mime=assets.PDF,
            original_name=name,
            source="databook",
            source_ref={"packet_id": w.id, "seal_id": seal_id},
            uploaded_by=w.user_id,
            packet_id=w.id,
        )
    except ApiError as e:
        log.warning("data book for packet %s was not stored: %s", w.id, e.detail)
        raise ApiError(500, "databook_failed", MSG_DATABOOK.format(reason=e.detail.rstrip("."))) from None
    finally:
        with contextlib.suppress(OSError):
            Path(tmp_name).unlink()
    pages = int(built.pages)
    w.conn.execute(
        "UPDATE packet_seals SET databook_asset_id = %s, databook_pages = %s WHERE id = %s",
        (stored["id"], pages, seal_id),
    )
    w.detail["databook_asset_id"] = str(stored["id"])
    return pages


def _reason_text(e: BaseException) -> str:
    text = " ".join(str(e).split()).rstrip(".")
    return text[:300] or "an unknown error"


def verify_seal(conn: Any, settings: Any, packet_id: int) -> dict[str, Any]:
    """The seal history of a packet and whether the current unbroken seal still matches the packet."""
    seals = packets.rows(conn, "SELECT * FROM packet_seals WHERE packet_id = %s ORDER BY id DESC", (packet_id,))
    people = packets.People(conn, [s["sealed_by"] for s in seals] + [s["broken_by"] for s in seals])
    current = next((s for s in seals if s["broken_at"] is None), None)
    valid: bool | None = None
    if current is not None:
        try:
            key = settings.seal_key()
        except SecretFileError:
            key = None
        if key is not None and seal_key_id(key) == current["key_id"]:
            row = packets.load_row(conn, packet_id)
            assert row is not None
            valid = hmac.compare_digest(seal_hash(key, packets.seal_content(conn, row)), bytes(current["hash"]))

    def shape(s: Mapping[str, Any]) -> dict[str, Any]:
        return {
            "id": s["id"],
            "sealed_at": s["sealed_at"],
            "sealed_by": people.ref(s["sealed_by"]),
            "key_id": s["key_id"],
            "hash": bytes(s["hash"]).hex(),
            "signed": s["signature_id"] is not None,
            "broken_at": s["broken_at"],
            "broken_by": people.ref(s["broken_by"]),
            "broken_reason": s["broken_reason"],
            "open_wos": None if s.get("open_wos") is None else list(s["open_wos"]),
            "databook_asset_id": None if s.get("databook_asset_id") is None else str(s["databook_asset_id"]),
            "databook_pages": s.get("databook_pages"),
        }

    return {"seal": shape(current) if current else None, "valid": valid, "seals": [shape(s) for s in seals]}