"""Unified session/lease/lock/worktree inventory for the web console (#636).

Leases (#433), worktrees (#432), and runtime (#430) each ship their own MVP
view, each with its own shape and its own idea of what "owned" means. A
traffic-control or recovery operator has to read all three and correlate them
by hand, which is exactly the step that goes wrong under collision pressure.

This module aggregates them into one versioned, read-only snapshot so the
console, and any worker asking "what is safe to do next", read the same
inventory from the same authority.

Field authority is explicit and never blended. Every section declares where its
rows came from:

* ``control_plane_db`` — the #613 substrate: sessions, leases, assignments.
  Authoritative for *exclusive ownership* (#600/#601).
* ``filesystem`` — durable per-issue lock files (:mod:`issue_lock_store`) and
  registered git worktrees. Authoritative for *what exists on this machine*.
* ``gitea`` — remote issue/PR state, reached only through existing loaders.

Safety invariants:

* **Read-only.** The control-plane database is opened through a ``mode=ro``
  URI. :class:`control_plane_db.ControlPlaneDB` creates directories and runs
  migrations in its constructor, which an inventory read must never do, so this
  module talks to sqlite directly rather than through that class.
* **Fail-soft, never fail-silent.** A subsystem that cannot be read degrades to
  a section carrying ``status`` and ``reason``. It never raises, and it never
  produces an empty list that reads like "nothing is there".
* **Never invent active ownership.** This is the invariant that matters most.
  A degraded ownership source sets ``ownership_authority_complete`` false, and
  while that flag is false no work item is reported unowned and no collision is
  asserted. Absence of evidence is reported as absence of evidence.
* **Redaction at the boundary.** Absolute paths are collapsed against the home
  directory, URLs lose userinfo and query strings, and no credential-shaped
  value is emitted. No session token exists in these sources and none is read.

Phase 1 is read-only. Lease steal/release and worktree deletion are Phase 2+
and deliberately have no representation here, not even a disabled one.
"""

from __future__ import annotations

import os
import re
import sqlite3
import time
from dataclasses import dataclass, field
from datetime import datetime, timezone
from typing import Any, Callable
from urllib.parse import urlparse

import control_plane_db
import issue_lock_store

SCHEMA_VERSION = 1
API_VERSION = "v1"

#: Sections whose absence would make an ownership claim unprovable. If any of
#: these is not ``ok``, the snapshot refuses to describe anything as unowned.
OWNERSHIP_SECTIONS = ("sessions", "leases", "locks")

SECTION_NAMES = ("sessions", "leases", "locks", "worktrees", "namespaces")

STATUS_OK = "ok"
STATUS_DEGRADED = "degraded"
STATUS_UNAVAILABLE = "unavailable"

AUTHORITY_CONTROL_PLANE_DB = "control_plane_db"
AUTHORITY_FILESYSTEM = "filesystem"
AUTHORITY_GITEA = "gitea"

_CREDENTIAL_KEY_RE = re.compile(
    r"(token|secret|password|passwd|api[_-]?key|authorization|bearer|credential)",
    re.IGNORECASE,
)
_REDACTED = "[redacted]"


@dataclass(frozen=True)
class InventorySection:
    """One subsystem's contribution, with its authority and health."""

    name: str
    authority: str
    status: str
    items: tuple[dict[str, Any], ...] = ()
    reason: str | None = None
    scan_ms: float | None = None

    @property
    def ok(self) -> bool:
        return self.status == STATUS_OK

    def to_dict(self) -> dict[str, Any]:
        return {
            "name": self.name,
            "authority": self.authority,
            "status": self.status,
            "count": len(self.items),
            "reason": self.reason,
            "scan_ms": self.scan_ms,
            "items": [dict(item) for item in self.items],
        }


@dataclass(frozen=True)
class CollisionSignal:
    """A detected conflict between two ownership records."""

    kind: str
    message: str
    severity: str = "warning"
    issue_number: int | None = None
    branch: str | None = None
    worktree_path: str | None = None
    session_ids: tuple[str, ...] = ()

    def to_dict(self) -> dict[str, Any]:
        return {
            "kind": self.kind,
            "severity": self.severity,
            "message": self.message,
            "issue_number": self.issue_number,
            "branch": self.branch,
            "worktree_path": self.worktree_path,
            "session_ids": list(self.session_ids),
        }


@dataclass(frozen=True)
class InventorySnapshot:
    """Versioned aggregate of every inventory section."""

    generated_at: str
    sections: tuple[InventorySection, ...]
    collisions: tuple[CollisionSignal, ...] = ()
    correlations: tuple[dict[str, Any], ...] = ()
    schema_version: int = SCHEMA_VERSION
    api_version: str = API_VERSION
    scan_ms: float | None = None
    _section_index: dict[str, InventorySection] = field(
        default_factory=dict, repr=False, compare=False
    )

    def section(self, name: str) -> InventorySection | None:
        return self._section_index.get(name)

    @property
    def degraded_sections(self) -> tuple[str, ...]:
        return tuple(s.name for s in self.sections if not s.ok)

    @property
    def ownership_authority_complete(self) -> bool:
        """True only when every ownership-bearing section read cleanly.

        While this is false the snapshot must not describe any work item as
        unowned: a lease the reader could not load is not an absent lease.
        """
        for name in OWNERSHIP_SECTIONS:
            section = self._section_index.get(name)
            if section is None or not section.ok:
                return False
        return True

    @property
    def status(self) -> str:
        if all(s.ok for s in self.sections):
            return STATUS_OK
        return STATUS_DEGRADED


# ── redaction ────────────────────────────────────────────────────────────────


def redact_path(path: str | None) -> str | None:
    """Collapse an absolute path against ``$HOME`` for browser display."""
    if not path:
        return path
    text = str(path)
    home = os.path.expanduser("~")
    if home and home != "/" and text.startswith(home):
        return "~" + text[len(home) :]
    return text


def redact_url(value: str | None) -> str | None:
    """Strip userinfo and query string from a URL."""
    if not value:
        return value
    text = str(value)
    try:
        parsed = urlparse(text)
    except ValueError:
        return _REDACTED
    if not parsed.scheme or not parsed.netloc:
        return text
    netloc = parsed.hostname or ""
    if parsed.port:
        netloc = f"{netloc}:{parsed.port}"
    rebuilt = f"{parsed.scheme}://{netloc}{parsed.path}"
    return rebuilt.rstrip("/") or rebuilt


def scrub(value: Any, *, key: str | None = None) -> Any:
    """Recursively drop credential-shaped values and redact paths/URLs.

    Never raises: an unexpected object degrades to its ``repr`` rather than
    propagating out of a read-only view.
    """
    if key and _CREDENTIAL_KEY_RE.search(key):
        return _REDACTED
    if isinstance(value, dict):
        return {str(k): scrub(v, key=str(k)) for k, v in value.items()}
    if isinstance(value, (list, tuple)):
        return [scrub(v, key=key) for v in value]
    if isinstance(value, str):
        if value.startswith(("http://", "https://")):
            return redact_url(value)
        if value.startswith("/") or value.startswith("~"):
            return redact_path(value)
        return value
    if isinstance(value, (int, float, bool)) or value is None:
        return value
    return repr(value)


# ── control-plane database (read-only) ───────────────────────────────────────


def _open_readonly(db_path: str) -> sqlite3.Connection:
    """Open the control-plane DB without creating or migrating anything."""
    conn = sqlite3.connect(f"file:{db_path}?mode=ro", uri=True, timeout=5)
    conn.row_factory = sqlite3.Row
    return conn


def _table_names(conn: sqlite3.Connection) -> set[str]:
    rows = conn.execute(
        "SELECT name FROM sqlite_master WHERE type = 'table'"
    ).fetchall()
    return {str(row[0]) for row in rows}


def _load_cp_db_sections(
    *,
    db_path: str | None = None,
    limit: int = 200,
) -> tuple[InventorySection, InventorySection]:
    """Return the ``sessions`` and ``leases`` sections from the #613 DB."""
    path = (db_path or control_plane_db.default_db_path()).strip()

    def _both_unavailable(reason: str) -> tuple[InventorySection, InventorySection]:
        return (
            InventorySection(
                name="sessions",
                authority=AUTHORITY_CONTROL_PLANE_DB,
                status=STATUS_UNAVAILABLE,
                reason=reason,
            ),
            InventorySection(
                name="leases",
                authority=AUTHORITY_CONTROL_PLANE_DB,
                status=STATUS_UNAVAILABLE,
                reason=reason,
            ),
        )

    if not path:
        return _both_unavailable("control-plane database path is not configured")
    if not os.path.exists(path):
        return _both_unavailable(
            f"control-plane database not present at {redact_path(path)}; "
            "no session or lease authority available"
        )

    started = time.perf_counter()
    try:
        conn = _open_readonly(path)
    except sqlite3.Error as exc:
        return _both_unavailable(f"control-plane database could not be opened: {exc}")

    try:
        tables = _table_names(conn)
        if "sessions" not in tables or "leases" not in tables:
            missing = sorted({"sessions", "leases"} - tables)
            return _both_unavailable(
                "control-plane database is missing required tables: "
                + ", ".join(missing)
            )

        session_rows = [
            dict(row)
            for row in conn.execute(
                "SELECT session_id, role, profile, namespace, pid, started_at,"
                " last_heartbeat_at, status FROM sessions"
                " ORDER BY last_heartbeat_at DESC LIMIT ?",
                (max(1, int(limit)),),
            ).fetchall()
        ]

        has_work_items = "work_items" in tables
        if has_work_items:
            lease_sql = (
                "SELECT l.lease_id, l.session_id, l.role, l.phase, l.status,"
                " l.expires_at, w.remote, w.org, w.repo, w.kind AS work_kind,"
                " w.number AS work_number, w.state AS work_state,"
                " s.pid AS session_pid, s.profile AS session_profile,"
                " s.namespace AS session_namespace, s.status AS session_status"
                " FROM leases l"
                " JOIN work_items w ON w.work_item_id = l.work_item_id"
                " LEFT JOIN sessions s ON s.session_id = l.session_id"
                " ORDER BY l.expires_at DESC LIMIT ?"
            )
        else:
            lease_sql = (
                "SELECT l.lease_id, l.session_id, l.role, l.phase, l.status,"
                " l.expires_at FROM leases l"
                " ORDER BY l.expires_at DESC LIMIT ?"
            )
        lease_rows = [
            dict(row)
            for row in conn.execute(lease_sql, (max(1, int(limit)),)).fetchall()
        ]
    except sqlite3.Error as exc:
        return _both_unavailable(f"control-plane database read failed: {exc}")
    finally:
        conn.close()

    elapsed = (time.perf_counter() - started) * 1000.0
    now = datetime.now(timezone.utc)

    sessions = tuple(
        scrub(
            {
                "session_id": row.get("session_id"),
                "role": row.get("role"),
                "profile": row.get("profile"),
                "namespace": row.get("namespace"),
                "pid": row.get("pid"),
                "pid_alive": issue_lock_store.is_process_alive(row.get("pid")),
                "started_at": row.get("started_at"),
                "last_heartbeat_at": row.get("last_heartbeat_at"),
                "status": row.get("status"),
            }
        )
        for row in session_rows
    )

    leases = tuple(
        scrub(
            {
                "lease_id": row.get("lease_id"),
                "session_id": row.get("session_id"),
                "role": row.get("role"),
                "phase": row.get("phase"),
                "status": row.get("status"),
                "expires_at": row.get("expires_at"),
                "expired": _is_expired(row.get("expires_at"), now=now),
                "remote": row.get("remote"),
                "org": row.get("org"),
                "repo": row.get("repo"),
                "work_kind": row.get("work_kind"),
                "work_number": row.get("work_number"),
                "work_state": row.get("work_state"),
                "session_pid": row.get("session_pid"),
                "session_profile": row.get("session_profile"),
                "session_namespace": row.get("session_namespace"),
                "session_status": row.get("session_status"),
            }
        )
        for row in lease_rows
    )

    degraded_reason = (
        None
        if has_work_items
        else "work_items table absent; lease rows carry no work linkage"
    )
    lease_status = STATUS_OK if has_work_items else STATUS_DEGRADED

    return (
        InventorySection(
            name="sessions",
            authority=AUTHORITY_CONTROL_PLANE_DB,
            status=STATUS_OK,
            items=sessions,
            scan_ms=round(elapsed, 3),
        ),
        InventorySection(
            name="leases",
            authority=AUTHORITY_CONTROL_PLANE_DB,
            status=lease_status,
            items=leases,
            reason=degraded_reason,
            scan_ms=round(elapsed, 3),
        ),
    )


def _is_expired(expires_at: str | None, *, now: datetime) -> bool | None:
    if not expires_at:
        return None
    text = str(expires_at).strip().replace("Z", "+00:00")
    try:
        parsed = datetime.fromisoformat(text)
    except ValueError:
        return None
    if parsed.tzinfo is None:
        parsed = parsed.replace(tzinfo=timezone.utc)
    return parsed <= now


# ── durable issue locks (filesystem) ─────────────────────────────────────────


def _load_locks_section(*, lock_dir: str | None = None) -> InventorySection:
    started = time.perf_counter()
    try:
        paths = issue_lock_store.iter_lock_files(lock_dir)
    except OSError as exc:
        return InventorySection(
            name="locks",
            authority=AUTHORITY_FILESYSTEM,
            status=STATUS_UNAVAILABLE,
            reason=f"issue lock directory could not be listed: {exc}",
        )

    items: list[dict[str, Any]] = []
    unreadable = 0
    for path in paths:
        try:
            record = issue_lock_store.read_lock_file(path)
        except (OSError, ValueError):
            unreadable += 1
            continue
        if not record:
            unreadable += 1
            continue
        try:
            freshness = issue_lock_store.assess_lock_freshness(record)
        except Exception:  # noqa: BLE001 — a read-only view never raises
            freshness = {"status": "unknown", "live": False, "stale": False}
        claimant = record.get("claimant") or (
            (record.get("work_lease") or {}).get("claimant") or {}
        )
        items.append(
            scrub(
                {
                    "issue_number": record.get("issue_number"),
                    "branch_name": record.get("branch_name"),
                    "remote": record.get("remote"),
                    "org": record.get("org"),
                    "repo": record.get("repo"),
                    "worktree_path": record.get("worktree_path"),
                    "pid": record.get("session_pid") or record.get("pid"),
                    "pid_alive": issue_lock_store.is_process_alive(
                        record.get("session_pid") or record.get("pid")
                    ),
                    "claimant_username": (claimant or {}).get("username"),
                    "claimant_profile": (claimant or {}).get("profile"),
                    "lock_generation": record.get("lock_generation"),
                    "freshness_status": freshness.get("status"),
                    "live": bool(freshness.get("live")),
                    "stale": bool(freshness.get("stale")),
                    "freshness_reason": freshness.get("reason"),
                    "lock_path": record.get("lock_file_path") or path,
                }
            )
        )

    elapsed = (time.perf_counter() - started) * 1000.0
    reason = (
        f"{unreadable} lock file(s) were unreadable and are not represented"
        if unreadable
        else None
    )
    return InventorySection(
        name="locks",
        authority=AUTHORITY_FILESYSTEM,
        status=STATUS_DEGRADED if unreadable else STATUS_OK,
        items=tuple(items),
        reason=reason,
        scan_ms=round(elapsed, 3),
    )


# ── worktrees (filesystem, via the #432 scanner) ─────────────────────────────


def _load_worktrees_section(
    *, load_hygiene: Callable[[], Any] | None = None
) -> InventorySection:
    started = time.perf_counter()
    try:
        loader = load_hygiene
        if loader is None:
            from webui.worktree_scanner import load_hygiene_snapshot

            loader = load_hygiene_snapshot
        snapshot = loader()
    except Exception as exc:  # noqa: BLE001 — fail soft, never fail the request
        return InventorySection(
            name="worktrees",
            authority=AUTHORITY_FILESYSTEM,
            status=STATUS_UNAVAILABLE,
            reason=f"worktree scan failed: {exc}",
        )

    items = tuple(
        scrub(
            {
                "rel_path": entry.rel_path,
                "folder_name": entry.folder_name,
                "classification": entry.classification,
                "branch": entry.branch,
                "head_sha": entry.head_sha,
                "dirty_tracked": entry.dirty_tracked,
                "dirty_untracked": entry.dirty_untracked,
                "detached": entry.detached,
                "registered_worktree": entry.registered_worktree,
                "notes": entry.notes,
            }
        )
        for entry in snapshot.entries
    )
    scan_error = getattr(snapshot, "scan_error", None)
    elapsed = (time.perf_counter() - started) * 1000.0
    return InventorySection(
        name="worktrees",
        authority=AUTHORITY_FILESYSTEM,
        status=STATUS_DEGRADED if scan_error else STATUS_OK,
        items=items,
        reason=scan_error,
        scan_ms=round(elapsed, 3),
    )


# ── namespaces / capability summary ──────────────────────────────────────────


def _load_namespaces_section() -> InventorySection:
    started = time.perf_counter()
    try:
        from gitea_auth import get_profile

        profile = get_profile() or {}
    except Exception as exc:  # noqa: BLE001
        return InventorySection(
            name="namespaces",
            authority=AUTHORITY_FILESYSTEM,
            status=STATUS_UNAVAILABLE,
            reason=f"active profile could not be resolved: {exc}",
        )

    allowed = list(profile.get("allowed_operations") or [])
    forbidden = list(profile.get("forbidden_operations") or [])
    profile_name = str(profile.get("profile_name") or "")

    namespace = None
    try:
        import role_namespace_gate

        namespace = role_namespace_gate.infer_mcp_namespace(profile_name)
    except Exception:  # noqa: BLE001 — namespace inference is advisory
        namespace = None

    item = scrub(
        {
            "profile_name": profile_name,
            "role": profile.get("role"),
            "mcp_namespace": namespace,
            "allowed_operations": sorted(allowed),
            "forbidden_operations": sorted(forbidden),
            "capability_summary": {
                "can_author": "gitea.pr.create" in allowed,
                "can_review": "gitea.pr.approve" in allowed,
                "can_merge": "gitea.pr.merge" in allowed,
                "can_close_pr": "gitea.pr.close" in allowed,
            },
            "active": True,
        }
    )
    elapsed = (time.perf_counter() - started) * 1000.0
    return InventorySection(
        name="namespaces",
        authority=AUTHORITY_FILESYSTEM,
        status=STATUS_OK,
        items=(item,),
        reason=(
            "only the profile serving this web process is observable; other "
            "namespaces are not enumerable from here"
        ),
        scan_ms=round(elapsed, 3),
    )


# ── correlation and collision detection ──────────────────────────────────────


def _issue_from_branch(branch: str | None) -> int | None:
    match = re.search(r"issue-(\d+)", str(branch or ""), re.IGNORECASE)
    return int(match.group(1)) if match else None


def correlate(
    *,
    leases: InventorySection,
    locks: InventorySection,
    worktrees: InventorySection,
    sessions: InventorySection,
) -> tuple[tuple[dict[str, Any], ...], tuple[CollisionSignal, ...]]:
    """Join lease owner ↔ lock ↔ worktree ↔ namespace where evidence allows.

    Correlation rows are emitted from whatever sections did load. Collision
    signals are only emitted from sections that are ``ok``: a conflict inferred
    from a partially-read source would be a false accusation.
    """
    correlations: list[dict[str, Any]] = []
    collisions: list[CollisionSignal] = []

    worktree_by_branch: dict[str, dict[str, Any]] = {}
    for entry in worktrees.items:
        branch = (entry.get("branch") or "").strip()
        if branch:
            worktree_by_branch.setdefault(branch, entry)

    session_by_id = {
        str(s.get("session_id")): s for s in sessions.items if s.get("session_id")
    }

    # Lock-centred rows: a durable lock names an issue, a branch, and a worktree.
    for lock in locks.items:
        branch = (lock.get("branch_name") or "").strip()
        worktree = worktree_by_branch.get(branch)
        matching_leases = [
            lease
            for lease in leases.items
            if lease.get("work_kind") == "issue"
            and lease.get("work_number") == lock.get("issue_number")
        ]
        correlations.append(
            {
                "issue_number": lock.get("issue_number"),
                "branch": branch or None,
                "lock_live": bool(lock.get("live")),
                "lock_claimant": lock.get("claimant_profile"),
                "lock_pid": lock.get("pid"),
                "lock_pid_alive": lock.get("pid_alive"),
                "worktree_rel_path": (worktree or {}).get("rel_path"),
                "worktree_classification": (worktree or {}).get("classification"),
                "worktree_registered": (worktree or {}).get("registered_worktree"),
                "lease_ids": [
                    lease.get("lease_id")
                    for lease in matching_leases
                    if lease.get("lease_id")
                ],
                "lease_sessions": [
                    lease.get("session_id")
                    for lease in matching_leases
                    if lease.get("session_id")
                ],
            }
        )

        if locks.ok and worktrees.ok:
            # A claim whose lease window is still open but has no registered
            # worktree is an anomaly regardless of whether its pid is alive; a
            # fully time-expired lease is on its way out and is not flagged.
            if (
                lock.get("freshness_status") != "expired"
                and branch
                and worktree is None
            ):
                collisions.append(
                    CollisionSignal(
                        kind="lock-without-worktree",
                        severity="warning",
                        issue_number=lock.get("issue_number"),
                        branch=branch,
                        worktree_path=lock.get("worktree_path"),
                        message=(
                            f"Live lock on issue #{lock.get('issue_number')} names "
                            f"branch {branch!r} but no registered worktree carries "
                            "that branch (#404)"
                        ),
                    )
                )

        if locks.ok:
            # A lock whose recorded pid is gone is held by nobody: a clean #753
            # dead-session recovery candidate. Subclassify by the lease window,
            # because the two cases need different operator urgency. When the
            # window is still open the lock would read as live to a naive
            # timestamp check even though the owner is dead — the more dangerous
            # case — so it is flagged distinctly from a fully time-expired lease.
            if lock.get("pid_alive") is False and lock.get("stale"):
                if lock.get("freshness_status") == "expired":
                    collisions.append(
                        CollisionSignal(
                            kind="stale-lock-dead-owner",
                            severity="warning",
                            issue_number=lock.get("issue_number"),
                            branch=branch or None,
                            message=(
                                f"Lock on issue #{lock.get('issue_number')} is stale "
                                f"and its recorded pid {lock.get('pid')} is not running "
                                "(#753 dead-session recovery candidate)"
                            ),
                        )
                    )
                else:
                    collisions.append(
                        CollisionSignal(
                            kind="live-lock-dead-owner",
                            severity="warning",
                            issue_number=lock.get("issue_number"),
                            branch=branch or None,
                            message=(
                                f"Lock on issue #{lock.get('issue_number')} has an "
                                "unexpired lease but its recorded pid "
                                f"{lock.get('pid')} is not running; it would read as "
                                "live to a timestamp check (#753 dead-session recovery "
                                "candidate)"
                            ),
                        )
                    )
            # The #635 trap: the lease has expired but the recorded pid is a
            # still-running daemon, so neither dead-pid reclaim nor exact-owner
            # renewal applies. This is the collision an operator must see.
            elif (
                lock.get("freshness_status") == "expired"
                and lock.get("pid_alive") is True
            ):
                collisions.append(
                    CollisionSignal(
                        kind="expired-lock-live-owner",
                        severity="error",
                        issue_number=lock.get("issue_number"),
                        branch=branch or None,
                        message=(
                            f"Lock on issue #{lock.get('issue_number')} has an expired "
                            f"lease but its recorded pid {lock.get('pid')} is still "
                            "running (daemon-pid deadlock; needs an operator decision, "
                            "#635/#760)"
                        ),
                    )
                )

    # Two live locks on one branch, or two active leases on one work item.
    if locks.ok:
        by_branch: dict[str, list[dict[str, Any]]] = {}
        for lock in locks.items:
            if not lock.get("live"):
                continue
            branch = (lock.get("branch_name") or "").strip()
            if branch:
                by_branch.setdefault(branch, []).append(lock)
        for branch, entries in sorted(by_branch.items()):
            if len(entries) > 1:
                collisions.append(
                    CollisionSignal(
                        kind="duplicate-live-lock",
                        severity="error",
                        branch=branch,
                        message=(
                            f"{len(entries)} live locks name branch {branch!r}: "
                            "issues "
                            + ", ".join(
                                f"#{e.get('issue_number')}" for e in entries
                            )
                        ),
                    )
                )

    if leases.ok:
        by_work: dict[tuple[str, int], list[dict[str, Any]]] = {}
        for lease in leases.items:
            if str(lease.get("status") or "").lower() != "active":
                continue
            kind = str(lease.get("work_kind") or "").strip().lower()
            number = lease.get("work_number")
            if not kind or number is None:
                continue
            by_work.setdefault((kind, int(number)), []).append(lease)
        for (kind, number), entries in sorted(by_work.items()):
            sessions_held = {
                str(e.get("session_id")) for e in entries if e.get("session_id")
            }
            if len(sessions_held) > 1:
                collisions.append(
                    CollisionSignal(
                        kind="concurrent-active-lease",
                        severity="error",
                        issue_number=number if kind == "issue" else None,
                        session_ids=tuple(sorted(sessions_held)),
                        message=(
                            f"{len(sessions_held)} sessions hold an active lease on "
                            f"{kind} #{number}"
                        ),
                    )
                )
            for entry in entries:
                if entry.get("expired") is True:
                    collisions.append(
                        CollisionSignal(
                            kind="active-lease-past-expiry",
                            severity="warning",
                            issue_number=number if kind == "issue" else None,
                            session_ids=(
                                (str(entry.get("session_id")),)
                                if entry.get("session_id")
                                else ()
                            ),
                            message=(
                                f"Lease {entry.get('lease_id')} on {kind} #{number} "
                                "is still marked active past its expiry"
                            ),
                        )
                    )

    # A lease whose owning session is gone is an orphan, not free work.
    if leases.ok and sessions.ok:
        for lease in leases.items:
            if str(lease.get("status") or "").lower() != "active":
                continue
            session_id = str(lease.get("session_id") or "")
            if session_id and session_id not in session_by_id:
                collisions.append(
                    CollisionSignal(
                        kind="orphan-lease",
                        severity="error",
                        session_ids=(session_id,),
                        message=(
                            f"Active lease {lease.get('lease_id')} names session "
                            f"{session_id}, which has no session record"
                        ),
                    )
                )

    return tuple(correlations), tuple(collisions)


# ── snapshot assembly ────────────────────────────────────────────────────────


def load_inventory_snapshot(
    *,
    db_path: str | None = None,
    lock_dir: str | None = None,
    load_hygiene: Callable[[], Any] | None = None,
    include: tuple[str, ...] | None = None,
) -> InventorySnapshot:
    """Build the unified inventory snapshot.

    Every section is loaded independently and fails soft. *include* restricts
    the sections that are scanned; omitted sections are simply absent rather
    than reported as empty, so a resource-split request cannot be mistaken for
    a whole-inventory answer.
    """
    started = time.perf_counter()
    wanted = tuple(include) if include else SECTION_NAMES

    sections: list[InventorySection] = []
    sessions_section: InventorySection | None = None
    leases_section: InventorySection | None = None

    if "sessions" in wanted or "leases" in wanted:
        sessions_section, leases_section = _load_cp_db_sections(db_path=db_path)
        if "sessions" in wanted:
            sections.append(sessions_section)
        if "leases" in wanted:
            sections.append(leases_section)

    locks_section = (
        _load_locks_section(lock_dir=lock_dir)
        if "locks" in wanted
        else _empty_section("locks", AUTHORITY_FILESYSTEM)
    )
    if "locks" in wanted:
        sections.append(locks_section)

    worktrees_section = (
        _load_worktrees_section(load_hygiene=load_hygiene)
        if "worktrees" in wanted
        else _empty_section("worktrees", AUTHORITY_FILESYSTEM)
    )
    if "worktrees" in wanted:
        sections.append(worktrees_section)

    if "namespaces" in wanted:
        sections.append(_load_namespaces_section())

    correlations, collisions = correlate(
        leases=leases_section or _empty_section("leases", AUTHORITY_CONTROL_PLANE_DB),
        locks=locks_section,
        worktrees=worktrees_section,
        sessions=sessions_section
        or _empty_section("sessions", AUTHORITY_CONTROL_PLANE_DB),
    )

    elapsed = (time.perf_counter() - started) * 1000.0
    index = {section.name: section for section in sections}
    return InventorySnapshot(
        generated_at=datetime.now(timezone.utc).isoformat(),
        sections=tuple(sections),
        collisions=collisions,
        correlations=correlations,
        scan_ms=round(elapsed, 3),
        _section_index=index,
    )


def _empty_section(name: str, authority: str) -> InventorySection:
    """A section that was not requested — never a claim that it is empty."""
    return InventorySection(
        name=name,
        authority=authority,
        status=STATUS_UNAVAILABLE,
        reason="section not requested in this scan",
    )


def snapshot_to_dict(snapshot: InventorySnapshot) -> dict[str, Any]:
    """Serialize the snapshot for the versioned API."""
    return {
        "api_version": snapshot.api_version,
        "schema_version": snapshot.schema_version,
        "generated_at": snapshot.generated_at,
        "status": snapshot.status,
        "scan_ms": snapshot.scan_ms,
        "ownership_authority_complete": snapshot.ownership_authority_complete,
        "ownership_note": (
            "Every ownership source read cleanly; an item absent from leases "
            "and locks is genuinely unclaimed."
            if snapshot.ownership_authority_complete
            else "One or more ownership sources are degraded; nothing in this "
            "snapshot may be treated as unowned. Collisions are reported only "
            "from sections that read cleanly."
        ),
        "degraded_sections": list(snapshot.degraded_sections),
        "field_authority": {
            "sessions": AUTHORITY_CONTROL_PLANE_DB,
            "leases": AUTHORITY_CONTROL_PLANE_DB,
            "locks": AUTHORITY_FILESYSTEM,
            "worktrees": AUTHORITY_FILESYSTEM,
            "namespaces": AUTHORITY_FILESYSTEM,
        },
        "sections": {section.name: section.to_dict() for section in snapshot.sections},
        "correlations": [dict(row) for row in snapshot.correlations],
        "collisions": [signal.to_dict() for signal in snapshot.collisions],
    }