"""Per-PC endpoint credentials: enrollment, administration and fleet migration.

Agent-facing:
  POST /enroll                     issue a credential or record a pending request
  POST /collect                    the generic collector ingest, under this prefix

Admin (endpoints.fleet to read, admin role to change):
  GET  /enrollment                 credential state per computer + requests
  POST /enrollment/requests/<id>/approve | reject
  POST /enrollment/assets/<assetid>/revoke          body {"blockreenroll", "reason"}
  POST /enrollment/assets/<assetid>/allow-reenroll  lift a re-enrollment block
  PUT  /enrollment/settings
  GET  /enrollment/migration       readiness of every computer for agent 1.20
  POST /enrollment/migration/wave  push the agent upgrade to a batch of PCs

Dashboard (endpoints.fleet):
  GET  /dashboard/enrollmentpending  one row while enroll requests await an admin
  GET  /dashboard/reenrollblocked    PCs blocked from re-enrolling over 7 days

A PC moves onto its own credential by running an agent that enrolls. The
migration surface computes, per computer, whether the existing agent upgrade
can be pushed to it, and pushes it in waves through the same enqueue path the
single-asset agentupgrade route uses.
"""

import hmac
import re
from collections import Counter
from datetime import datetime, timedelta, timezone

from flask import current_app, request
from flask_jwt_extended import current_user

from shopdb.api import (
    db, Asset, AuditLog, Script, Setting, error_response, success_response,
    ErrorCodes, require_permission, require_role, collector_authorized,
    collector_ingest, client_ip, get_pagination_params,
)

from ..commands import (
    ACTIVE_LOCK_FOR, ALLOWED_ACTIONS_FOR, agent_meets_minimum,
    minimum_agent_version_for, parse_agent_version,
)
from ..models import (
    EndpointCommand, EndpointCredential, EndpointEnrollRequest,
    EndpointMigrationWave, EndpointState,
)
from . import agentauth
from .ratelimit import ratelimited, rate_limit_response
from .routes import endpoints_bp

# First agent that enrolls itself.
CREDENTIAL_AGENT_VERSION = '1.20.0'

CODE_ENROLL_NONCE_MISMATCH = 'ENROLL_NONCE_MISMATCH'
CODE_ENROLL_PENDING_FULL = 'ENROLL_PENDING_FULL'

# Fixed-window per-IP limiter on /enroll, which takes no auth by design and
# writes a row for every new (hostname, serialnumber) pair it has not seen.
# Sized for a whole shop floor behind one address, not for one PC: an agent
# waiting for approval re-asks about once a minute, so 300 in 60 seconds covers
# roughly 300 machines sharing a NAT address, or a re-enrollment wave across a
# smaller room, while still turning a scripted loop into a 429 within seconds.
# Same shape and cache as the bootstrap and login limiters (see .ratelimit).
ENROLL_RATELIMIT_MAX = 300
ENROLL_RATELIMIT_WINDOW_SECONDS = 60

# Ceiling on rows in the pending queue. The rate limit bounds how FAST an
# unauthenticated caller can write; this bounds how MANY rows exist at all, so a
# slow drip from many addresses cannot grow the table without limit or bury the
# genuine requests an admin has to find in the approval queue.
#
# The cap refuses only a request for a hostname and serial we have never seen.
# An existing row - pending, approved, rejected - still updates and still hands
# out an approved credential, so a real fleet at the cap keeps enrolling while
# an admin drains the queue, and the refusal cannot lock anybody out of a PC
# that is already in the workflow.
PENDING_CAP_SETTING = 'plugin.endpoints.maxpendingenrollments'
DEFAULT_PENDING_CAP = 500

_NONCE_PATTERN = re.compile(r'^[A-Za-z0-9_-]{32,128}$')

REASON_UNKNOWN_HOSTNAME = 'unknown hostname'
REASON_DUPLICATE_HOSTNAME = 'duplicate hostname'
REASON_NO_SERIAL = 'no serial on record'
REASON_SERIAL_MISMATCH = 'serial mismatch'
REASON_ALREADY_ENROLLED = 'already enrolled'
REASON_AWAITING_APPROVAL = 'awaiting approval'
REASON_NONCE_CHANGED = 'nonce changed'
REASON_REJECTED = 'rejected'
REASON_REENROLL_BLOCKED = 'reenroll blocked'

# What an approval did to the computer's hostname. Reported back so the UI can
# say so, and so an admin can tell a rename from a no-op.
HOSTNAME_UNCHANGED = 'unchanged'
HOSTNAME_SET = 'set'
HOSTNAME_OVERWRITTEN = 'overwritten'
HOSTNAME_MESSAGES = {
    HOSTNAME_UNCHANGED: 'Enroll request approved',
    HOSTNAME_SET: 'Enroll request approved; the hostname is now recorded on '
                  'that computer',
    HOSTNAME_OVERWRITTEN: 'Enroll request approved; that computer was renamed '
                          'to the hostname the PC reports',
}

MIGRATION_STATES = ('enrolled', 'pending', 'upgrading', 'ready', 'blocked',
                    'notreporting')
ENROLLMENT_STATES = ('enrolled', 'notenrolled', 'pending', 'revoked')

BLOCKER_OFFLINE = 'offline'
BLOCKER_NO_SERIAL = 'no serial on record'
BLOCKER_DUPLICATE_HOSTNAME = 'duplicate hostname'
BLOCKER_LOCKED = 'commands locked'
BLOCKER_NO_PACKAGE = 'no agent package in store'
BLOCKER_TOO_OLD = 'agent too old for remote upgrade'
BLOCKER_POLICY = 'run_script not permitted by policy'
BLOCKER_AWAITING_ENROLLMENT = 'awaiting enrollment'
BLOCKER_REENROLL_BLOCKED = 'reenroll blocked'
BLOCKER_CERT_UNTRUSTED = 'server certificate not trusted by this PC'

# How agents up to 1.19 word a download refused over the server certificate.
# Only a PC's own recorded failure shows it; the server cannot read a trust store.
_TLS_TRUST_FAILURES = (
    'ssl connection could not be established',
    'untrustedroot',
    'remotecertificatechainerrors',
    'the remote certificate is invalid',
    'could not establish trust relationship',
)

_OFFLINE_AFTER = timedelta(hours=24)
_WAVE_MAXIMUM = 100
_RECENT_REQUESTS = 50
_BLOCKED_ATTENTION_AFTER = timedelta(days=7)

# Per-PC credential state as the fleet list and PC detail show it. First match
# wins, in this order.
CREDENTIAL_ENROLLED = 'enrolled'
CREDENTIAL_REENROLL_BLOCKED = 'reenrollblocked'
CREDENTIAL_PENDING = 'pending'
CREDENTIAL_NOT_REPORTING = 'notreporting'
CREDENTIAL_SHARED_KEY = 'sharedkey'
CREDENTIAL_STATES = (CREDENTIAL_ENROLLED, CREDENTIAL_REENROLL_BLOCKED,
                     CREDENTIAL_PENDING, CREDENTIAL_NOT_REPORTING,
                     CREDENTIAL_SHARED_KEY)
CREDENTIAL_STATE_LABELS = {
    CREDENTIAL_ENROLLED: 'Enrolled',
    CREDENTIAL_REENROLL_BLOCKED: 'Re-enroll blocked',
    CREDENTIAL_PENDING: 'Pending',
    CREDENTIAL_NOT_REPORTING: 'Not reporting',
    CREDENTIAL_SHARED_KEY: 'Shared key (not enrolled)',
}


def _naive_utcnow():
    return datetime.now(timezone.utc).replace(tzinfo=None)


def _utciso(value):
    return value.isoformat() + 'Z' if value else None


def _username():
    return getattr(current_user, 'username', None)


def _computer_model():
    from plugins.computers.models import Computer
    return Computer


# ---------------------------------------------------------------------------
# Agent-facing
# ---------------------------------------------------------------------------

@endpoints_bp.route('/collect', methods=['POST'])
def agent_collect():
    """Agent telemetry ingest. Same handler as POST /api/collector/endpoints."""
    return collector_ingest('endpoints')


def _pending(row, reason, matchedassetid=None):
    row.status = EndpointEnrollRequest.STATUS_PENDING
    row.reason = reason
    row.matchedassetid = matchedassetid
    db.session.commit()
    return success_response(
        {'status': 'pending', 'requestid': row.requestid, 'reason': reason},
        http_code=202)


def issue_credential(assetid, enrolledvia):
    """Issue (or re-issue after revoke) the credential for one asset.

    Returns the secret. Only its hash is stored. Caller commits.
    """
    secret = agentauth.generate_credential()
    row = EndpointCredential.query.filter_by(assetid=assetid).first()
    if row is None:
        row = EndpointCredential(assetid=assetid)
        db.session.add(row)
    row.credentialhash = agentauth.hash_credential(secret)
    row.credentialprefix = secret[:agentauth.DISPLAY_PREFIX_LENGTH]
    row.enrolledvia = enrolledvia
    row.issuedat = _naive_utcnow()
    row.lastusedat = None
    row.revokedat = None
    row.revokedby = None
    return secret, row


def _issue(row, assetid, enrolledvia):
    secret, credential = issue_credential(assetid, enrolledvia)
    row.status = EndpointEnrollRequest.STATUS_ISSUED
    row.matchedassetid = assetid
    row.reason = None
    AuditLog.log('created', 'EndpointCredential', entityid=assetid,
                 entityname=row.hostname,
                 details='endpoint credential {} issued ({}), request {}'.format(
                     credential.credentialprefix, enrolledvia, row.requestid))
    db.session.commit()
    return success_response(
        {'status': 'enrolled', 'credential': secret, 'assetid': assetid},
        message='Endpoint enrolled', http_code=201)


def _text_field(payload, name, maximum, required):
    value = payload.get(name)
    if value is None:
        value = ''
    if not isinstance(value, str):
        return None, f'{name} must be a string'
    value = value.strip()
    if required and not value:
        return None, f'{name} is required'
    if len(value) > maximum:
        return None, f'{name} must be at most {maximum} characters'
    return value, None


def pending_cap():
    """How many pending enroll requests this site will hold. 0 = no cap."""
    try:
        value = int(Setting.get(PENDING_CAP_SETTING,
                                default=DEFAULT_PENDING_CAP))
    except (TypeError, ValueError):
        return DEFAULT_PENDING_CAP
    return max(value, 0)


def _pending_queue_is_full():
    """True when a NEW enroll request would push the queue past its cap.

    Counted, not paged: the answer is a single number and the route only asks
    on first contact for a hostname and serial, not on the repeat asks that
    make up almost all the traffic.
    """
    cap = pending_cap()
    if not cap:
        return False
    pending = (EndpointEnrollRequest.query
               .filter(EndpointEnrollRequest.status
                       == EndpointEnrollRequest.STATUS_PENDING)
               .count())
    return pending >= cap


def _pending_queue_full_response(hostname, serialnumber):
    """Refuse a new row, say so plainly in the log and leave an audit trail."""
    cap = pending_cap()
    current_app.logger.warning(
        'endpoint enroll refused from %s: pending queue is at its cap of %d '
        '(hostname %s, serial %s). Approve or reject requests in Settings > '
        'Endpoints > Enrollment, or raise %s.',
        client_ip(request), cap, hostname, serialnumber, PENDING_CAP_SETTING)
    AuditLog.log(
        'updated', 'EndpointEnrollRequest', entityname=hostname,
        details='enroll refused from {0}: pending queue at cap {1} '
                '(hostname {2}, serial {3})'.format(
                    client_ip(request), cap, hostname, serialnumber))
    db.session.commit()
    return error_response(
        CODE_ENROLL_PENDING_FULL,
        'This site is not accepting new enrollment requests right now. '
        'An administrator has to clear the pending queue.',
        http_code=503)


@endpoints_bp.route('/enroll', methods=['POST'])
def enroll_endpoint():
    """A PC asks for its own credential.

    Takes no auth. A PC installed without the shared key must still reach an
    admin, so a missing or invalid key never refuses the call: it records or
    updates the pending request for this hostname and serial. The shared key
    only decides auto-enroll: a valid key, while plugin.endpoints.sharedkeyallowed
    and plugin.endpoints.autoenroll are on, may issue on a clean match. Without
    one, only a credential an admin already approved for this exact hostname,
    serial and nonce is handed out.

    Unauthenticated and row-writing, so it carries both bounds an open door
    needs: a per-IP fixed-window rate limit on how fast, and a settings-backed
    cap on how many pending rows can exist. Neither touches a PC already in the
    workflow - the cap refuses only a hostname and serial never seen before.
    """
    if ratelimited('endpointenrollratelimit', 'ENDPOINTS_ENROLL_RATELIMIT',
                   ENROLL_RATELIMIT_MAX, ENROLL_RATELIMIT_WINDOW_SECONDS):
        return rate_limit_response(
            'Too many enrollment requests. Try again later.')

    sharedkeyauthenticated = False
    presented = bool(request.headers.get('X-API-Key')
                     or request.headers.get('Authorization'))
    if presented and agentauth.shared_key_allowed():
        if collector_authorized('endpoints') is None:
            sharedkeyauthenticated = True
        else:
            current_app.logger.warning(
                'endpoint enroll from %s presented an invalid API key; '
                'treated as unauthenticated', client_ip(request))

    payload = request.get_json(silent=True)
    if not isinstance(payload, dict):
        return error_response(ErrorCodes.VALIDATION_ERROR, 'No data provided')

    hostname, problem = _text_field(payload, 'hostname', 255, True)
    if problem is None:
        serialnumber, problem = _text_field(payload, 'serialnumber', 128, True)
    if problem is None:
        deviceid, problem = _text_field(payload, 'deviceid', 64, False)
    if problem is None:
        agentversion, problem = _text_field(payload, 'agentversion', 32, False)
    if problem is None:
        nonce = payload.get('enrollnonce')
        if not isinstance(nonce, str) or not _NONCE_PATTERN.match(nonce):
            problem = 'enrollnonce must be 32-128 characters of A-Z a-z 0-9 _ -'
    if problem is not None:
        return error_response(ErrorCodes.VALIDATION_ERROR, problem)

    now = _naive_utcnow()
    sourceip = client_ip(request)

    row = (EndpointEnrollRequest.query
           .filter(db.func.lower(EndpointEnrollRequest.hostname) == hostname.lower(),
                   db.func.lower(EndpointEnrollRequest.serialnumber)
                   == serialnumber.lower())
           .order_by(EndpointEnrollRequest.requestid.desc())
           .first())

    if row is None:
        # First contact for this hostname and serial. This is the only branch
        # that grows the table, so it is the only one the cap guards.
        if _pending_queue_is_full():
            return _pending_queue_full_response(hostname, serialnumber)
        row = EndpointEnrollRequest(
            hostname=hostname, serialnumber=serialnumber, enrollnonce=nonce,
            status=EndpointEnrollRequest.STATUS_PENDING, requestedat=now)
        db.session.add(row)
    else:
        samenonce = hmac.compare_digest(row.enrollnonce, nonce)
        if row.status == EndpointEnrollRequest.STATUS_APPROVED:
            row.lastseenat = now
            row.sourceip = sourceip
            if not samenonce:
                db.session.commit()
                return error_response(
                    CODE_ENROLL_NONCE_MISMATCH,
                    'This enrollment was approved for a different agent '
                    'installation', http_code=403)
            if agentauth.active_credential_for(row.matchedassetid) is not None:
                return _pending(row, REASON_ALREADY_ENROLLED, row.matchedassetid)
            if agentauth.reenroll_blocked(row.matchedassetid):
                return _pending(row, REASON_REENROLL_BLOCKED, row.matchedassetid)
            if row.matchedassetid is None or db.session.get(Asset, row.matchedassetid) is None:
                return _pending(row, REASON_UNKNOWN_HOSTNAME)
            return _issue(row, row.matchedassetid,
                          EndpointCredential.ENROLLED_APPROVED)
        if row.status == EndpointEnrollRequest.STATUS_PENDING and not samenonce:
            # First nonce wins; a second installation needs an admin.
            row.lastseenat = now
            row.sourceip = sourceip
            return _pending(row, REASON_NONCE_CHANGED, row.matchedassetid)
        if row.status == EndpointEnrollRequest.STATUS_REJECTED and samenonce:
            row.lastseenat = now
            row.sourceip = sourceip
            db.session.commit()
            return success_response(
                {'status': 'pending', 'requestid': row.requestid,
                 'reason': REASON_REJECTED}, http_code=202)
        if row.status != EndpointEnrollRequest.STATUS_PENDING:
            # Issued earlier (credential since revoked) or rejected for another
            # installation: a new enrollment cycle bound to this nonce.
            row.enrollnonce = nonce
            row.requestedat = now
            row.decidedat = None
            row.decidedby = None

    row.lastseenat = now
    row.sourceip = sourceip
    if deviceid:
        row.deviceid = deviceid
    if agentversion:
        row.agentversion = agentversion
    db.session.flush()

    Computer = _computer_model()
    matches = (Computer.query
               .filter(db.func.lower(Computer.hostname) == hostname.lower())
               .all())
    if not matches:
        return _pending(row, REASON_UNKNOWN_HOSTNAME)
    if len(matches) > 1:
        return _pending(row, REASON_DUPLICATE_HOSTNAME)

    assetid = matches[0].assetid
    asset = db.session.get(Asset, assetid)
    recorded = ((asset.serialnumber if asset is not None else None) or '').strip()
    if not recorded:
        return _pending(row, REASON_NO_SERIAL, assetid)
    if recorded.lower() != serialnumber.lower():
        return _pending(row, REASON_SERIAL_MISMATCH, assetid)
    if agentauth.active_credential_for(assetid) is not None:
        return _pending(row, REASON_ALREADY_ENROLLED, assetid)
    if agentauth.reenroll_blocked(assetid):
        return _pending(row, REASON_REENROLL_BLOCKED, assetid)
    if sharedkeyauthenticated and agentauth.auto_enroll_enabled():
        return _issue(row, assetid, EndpointCredential.ENROLLED_AUTO)
    return _pending(row, REASON_AWAITING_APPROVAL, assetid)


# ---------------------------------------------------------------------------
# Admin: credentials and requests
# ---------------------------------------------------------------------------

def _computers():
    """(assetid, hostname, serialnumber) for every active computer."""
    Computer = _computer_model()
    return (db.session.query(Computer.assetid, Computer.hostname,
                             Asset.serialnumber)
            .join(Asset, Asset.assetid == Computer.assetid)
            .filter(Asset.isactive.is_(True))
            .order_by(db.func.lower(Computer.hostname))
            .all())


def _pending_requests():
    return (EndpointEnrollRequest.query
            .filter_by(status=EndpointEnrollRequest.STATUS_PENDING)
            .all())


def _pending_index(requests):
    assetids = {r.matchedassetid for r in requests if r.matchedassetid}
    hostnames = {(r.hostname or '').lower() for r in requests}
    return assetids, hostnames


def _is_pending(assetid, hostname, index):
    assetids, hostnames = index
    return assetid in assetids or (hostname or '').lower() in hostnames


def _awaiting_admin_filter():
    """Pending requests an admin can act on.

    A PC blocked from re-enrolling keeps asking on purpose; those rows are
    expected, not work.
    """
    return db.and_(
        EndpointEnrollRequest.status == EndpointEnrollRequest.STATUS_PENDING,
        db.or_(EndpointEnrollRequest.reason.is_(None),
               EndpointEnrollRequest.reason != REASON_REENROLL_BLOCKED))


def credential_state_expression(assetid, hostname, lastreportedat):
    """SQL CASE giving CREDENTIAL_STATES for a row, evaluated in the query.

    Correlated EXISTS on endpointcredentials and endpointenrollrequests, so a
    paged list filters and labels in one statement instead of per row.
    """
    active = (db.select(EndpointCredential.credentialid)
              .where(EndpointCredential.assetid == assetid,
                     EndpointCredential.revokedat.is_(None))
              .exists())
    blocked = (db.select(EndpointCredential.credentialid)
               .where(EndpointCredential.assetid == assetid,
                      EndpointCredential.reenrollblocked.is_(True))
               .exists())
    pending = (db.select(EndpointEnrollRequest.requestid)
               .where(EndpointEnrollRequest.status
                      == EndpointEnrollRequest.STATUS_PENDING,
                      db.or_(EndpointEnrollRequest.matchedassetid == assetid,
                             db.func.lower(EndpointEnrollRequest.hostname)
                             == db.func.lower(hostname)))
               .exists())
    return db.case(
        (active, CREDENTIAL_ENROLLED),
        (blocked, CREDENTIAL_REENROLL_BLOCKED),
        (pending, CREDENTIAL_PENDING),
        (lastreportedat.is_(None), CREDENTIAL_NOT_REPORTING),
        else_=CREDENTIAL_SHARED_KEY,
    )


def credential_detail(assetid, hostname, lastreportedat, detailed):
    """Credential state of one PC, same rules as credential_state_expression.

    detailed False withholds the prefix, timestamps, enrollment path and block
    reason, leaving the state alone.
    """
    credential = EndpointCredential.query.filter_by(assetid=assetid).first()
    if credential is not None and credential.revokedat is None:
        state = CREDENTIAL_ENROLLED
    elif credential is not None and credential.reenrollblocked:
        state = CREDENTIAL_REENROLL_BLOCKED
    elif (EndpointEnrollRequest.query
          .filter(EndpointEnrollRequest.status
                  == EndpointEnrollRequest.STATUS_PENDING,
                  db.or_(EndpointEnrollRequest.matchedassetid == assetid,
                         db.func.lower(EndpointEnrollRequest.hostname)
                         == (hostname or '').lower()))
          .first()) is not None:
        state = CREDENTIAL_PENDING
    elif lastreportedat is None:
        state = CREDENTIAL_NOT_REPORTING
    else:
        state = CREDENTIAL_SHARED_KEY

    detail = {
        'state': state,
        'statelabel': CREDENTIAL_STATE_LABELS[state],
        'credentialprefix': None,
        'issuedat': None,
        'lastusedat': None,
        'revokedat': None,
        'enrolledvia': None,
        'reenrollblocked': bool(credential is not None
                                and credential.reenrollblocked),
        'reenrollblockedreason': None,
    }
    if detailed and credential is not None:
        detail.update({
            'credentialprefix': credential.credentialprefix,
            'issuedat': _utciso(credential.issuedat),
            'lastusedat': _utciso(credential.lastusedat),
            'revokedat': _utciso(credential.revokedat),
            'enrolledvia': credential.enrolledvia,
            'reenrollblockedreason': (credential.reenrollblockedreason
                                      if credential.reenrollblocked else None),
        })
    return detail


def _search_filter(rows, search, *keys):
    if not search:
        return rows
    needle = search.lower()
    return [row for row in rows
            if any(needle in str(row.get(key) or '').lower() for key in keys)]


def _page(rows):
    page, perpage = get_pagination_params()
    total = len(rows)
    start = (page - 1) * perpage
    totalpages = (total + perpage - 1) // perpage if perpage else 0
    return rows[start:start + perpage], {
        'page': page, 'perpage': perpage, 'total': total,
        'totalpages': totalpages, 'hasnext': page < totalpages,
        'hasprev': page > 1,
    }


def _settings_payload():
    return {'sharedkeyallowed': agentauth.shared_key_allowed(),
            'autoenroll': agentauth.auto_enroll_enabled(),
            'maxpendingenrollments': pending_cap()}


@endpoints_bp.route('/enrollment', methods=['GET'])
@require_permission('endpoints.fleet')
def get_enrollment():
    """Credential state of every computer, plus pending and recent requests."""
    credentials = {c.assetid: c for c in EndpointCredential.query.all()}
    pending = _pending_requests()
    index = _pending_index(pending)

    rows = []
    for assetid, hostname, serialnumber in _computers():
        credential = credentials.get(assetid)
        blocked = bool(credential is not None and credential.reenrollblocked)
        if credential is not None and credential.revokedat is None:
            state = 'enrolled'
        elif blocked:
            # Its agent keeps asking; those requests are expected, not pending work.
            state = 'revoked'
        elif _is_pending(assetid, hostname, index):
            state = 'pending'
        elif credential is not None:
            state = 'revoked'
        else:
            state = 'notenrolled'
        rows.append({
            'assetid': assetid,
            'hostname': hostname,
            'serialnumber': serialnumber,
            'state': state,
            'credentialprefix': credential.credentialprefix if credential else None,
            'issuedat': _utciso(credential.issuedat) if credential else None,
            'lastusedat': _utciso(credential.lastusedat) if credential else None,
            'enrolledvia': credential.enrolledvia if credential else None,
            'reenrollblocked': blocked,
            'reenrollblockedreason': (credential.reenrollblockedreason
                                      if blocked else None),
        })

    # Computer counts by state, except pending: that is every pending request,
    # including those naming no known computer, so it matches the request list.
    counts = Counter(row['state'] for row in rows)
    summary = {
        'enrolled': counts['enrolled'],
        'notenrolled': counts['notenrolled'] + counts['revoked'],
        'pendingcomputers': counts['pending'],
        'pending': len(pending),
    }

    state = (request.args.get('state') or '').strip().lower()
    if state:
        if state not in ENROLLMENT_STATES:
            return error_response(ErrorCodes.VALIDATION_ERROR,
                                  f'Unknown state filter: {state!r}')
        rows = [row for row in rows if row['state'] == state]
    rows = _search_filter(rows, (request.args.get('search') or '').strip(),
                          'hostname', 'serialnumber')
    pagerows, pagination = _page(rows)

    recent = (EndpointEnrollRequest.query
              .filter(EndpointEnrollRequest.status
                      != EndpointEnrollRequest.STATUS_PENDING)
              .order_by(EndpointEnrollRequest.lastseenat.desc())
              .limit(_RECENT_REQUESTS)
              .all())
    requests_payload = [
        r.to_dict()
        for r in sorted(pending, key=lambda r: r.lastseenat or r.requestedat,
                        reverse=True) + recent
    ]

    return success_response({
        'settings': _settings_payload(),
        'counts': summary,
        'computers': pagerows,
        'requests': requests_payload,
    }, meta={'pagination': pagination})


@endpoints_bp.route('/enrollment/requests/<int:requestid>/approve',
                    methods=['POST'])
@require_role('admin')
def approve_enroll_request(requestid):
    """Bind a pending request to the asset the admin picked.

    The computer record also has to CARRY the request's hostname, or the PC
    403s on every call after it collects its credential: bind_hostname resolves
    the hostname the agent sends to an asset and compares it with the
    credential's asset, and a computer with no hostname resolves to nothing.
    The pending reason for a one-off PC is by definition `unknown hostname`, so
    this is the normal case, not the exception.

    Body: {"assetid": 123, "sethostname": false}. A computer with no hostname
    is stamped with the request's. A computer carrying a DIFFERENT hostname is
    refused with 409 naming both, until the caller repeats the approval with
    "sethostname": true. Either change is audited, and the response says which
    of unchanged / set / overwritten happened.
    """
    row = db.session.get(EndpointEnrollRequest, requestid)
    if row is None:
        return error_response(ErrorCodes.NOT_FOUND,
                              f'No enroll request {requestid}', http_code=404)
    if row.status == EndpointEnrollRequest.STATUS_ISSUED:
        return error_response(ErrorCodes.CONFLICT,
                              'A credential was already issued for this request',
                              http_code=409)

    payload = request.get_json(silent=True) or {}
    assetid = payload.get('assetid')
    if isinstance(assetid, bool) or not isinstance(assetid, int):
        return error_response(ErrorCodes.VALIDATION_ERROR,
                              'assetid must be an integer')
    sethostname = payload.get('sethostname', False)
    if not isinstance(sethostname, bool):
        return error_response(ErrorCodes.VALIDATION_ERROR,
                              'sethostname must be true or false')
    Computer = _computer_model()
    computer = Computer.query.filter_by(assetid=assetid).first()
    if computer is None:
        return error_response(ErrorCodes.VALIDATION_ERROR,
                              f'Asset {assetid} is not a computer')
    if agentauth.active_credential_for(assetid) is not None:
        return error_response(ErrorCodes.CONFLICT,
                              'That computer is already enrolled; revoke its '
                              'credential first', http_code=409)
    if agentauth.reenroll_blocked(assetid):
        return error_response(ErrorCodes.CONFLICT,
                              'That computer is blocked from enrolling again; '
                              'allow re-enrollment first', http_code=409)

    requesthostname = (row.hostname or '').strip()
    currenthostname = (computer.hostname or '').strip()
    hostnameresult = HOSTNAME_UNCHANGED
    if requesthostname and not currenthostname:
        hostnameresult = HOSTNAME_SET
    elif requesthostname and currenthostname.lower() != requesthostname.lower():
        if not sethostname:
            return error_response(
                ErrorCodes.CONFLICT,
                'That computer is recorded as {0}, but the request comes from '
                '{1}. Approving as it stands leaves the PC unable to '
                'authenticate. Approve again with "sethostname": true to '
                'rename the computer to {1}.'.format(currenthostname,
                                                     requesthostname),
                details={'hostnameconflict': True,
                         'computerhostname': currenthostname,
                         'requesthostname': requesthostname},
                http_code=409)
        hostnameresult = HOSTNAME_OVERWRITTEN

    if hostnameresult != HOSTNAME_UNCHANGED:
        computer.hostname = requesthostname
        AuditLog.log('updated', 'Computer', entityid=computer.computerid,
                     entityname=requesthostname,
                     changes={'hostname': {'old': currenthostname or None,
                                           'new': requesthostname}},
                     details='hostname {0} from enroll request {1}'.format(
                         hostnameresult, row.requestid))

    row.status = EndpointEnrollRequest.STATUS_APPROVED
    row.matchedassetid = assetid
    row.reason = None
    row.decidedat = _naive_utcnow()
    row.decidedby = _username()
    AuditLog.log('updated', 'EndpointEnrollRequest', entityid=row.requestid,
                 entityname=row.hostname,
                 details='enroll request approved for asset {0}, hostname {1}'
                         .format(assetid, hostnameresult))
    db.session.commit()
    approved = row.to_dict()
    approved['hostnameresult'] = hostnameresult
    return success_response(approved, message=HOSTNAME_MESSAGES[hostnameresult])


@endpoints_bp.route('/enrollment/requests/<int:requestid>/reject',
                    methods=['POST'])
@require_role('admin')
def reject_enroll_request(requestid):
    row = db.session.get(EndpointEnrollRequest, requestid)
    if row is None:
        return error_response(ErrorCodes.NOT_FOUND,
                              f'No enroll request {requestid}', http_code=404)
    if row.status == EndpointEnrollRequest.STATUS_ISSUED:
        return error_response(ErrorCodes.CONFLICT,
                              'A credential was already issued for this request; '
                              'revoke the credential instead', http_code=409)
    row.status = EndpointEnrollRequest.STATUS_REJECTED
    row.decidedat = _naive_utcnow()
    row.decidedby = _username()
    AuditLog.log('updated', 'EndpointEnrollRequest', entityid=row.requestid,
                 entityname=row.hostname, details='enroll request rejected')
    db.session.commit()
    return success_response(row.to_dict(), message='Enroll request rejected')


@endpoints_bp.route('/enrollment/assets/<int:assetid>/revoke', methods=['POST'])
@require_role('admin')
def revoke_endpoint_credential(assetid):
    """Un-enroll a PC. Its agent gets CREDENTIAL_INVALID and enrolls again.

    Body (optional) {"blockreenroll": true, "reason": "rollback"} also keeps the
    PC from enrolling again until POST .../allow-reenroll. That is the step
    before rolling a PC back to an agent that only knows the shared key: without
    it the current agent re-enrolls within seconds and the older agent is then
    refused. A PC whose credential is already revoked can still be blocked.
    """
    payload = request.get_json(silent=True) or {}
    if not isinstance(payload, dict):
        return error_response(ErrorCodes.VALIDATION_ERROR,
                              'Body must be a JSON object')
    blockreenroll = payload.get('blockreenroll', False)
    if not isinstance(blockreenroll, bool):
        return error_response(ErrorCodes.VALIDATION_ERROR,
                              'blockreenroll must be true or false')
    reason = None
    if blockreenroll:
        reason, problem = _text_field(payload, 'reason', 64, False)
        if problem is not None:
            return error_response(ErrorCodes.VALIDATION_ERROR, problem)
        reason = reason or None

    credential = agentauth.active_credential_for(assetid)
    if credential is None and blockreenroll:
        credential = EndpointCredential.query.filter_by(assetid=assetid).first()
    if credential is None:
        return error_response(ErrorCodes.NOT_FOUND,
                              'This computer has no active credential',
                              http_code=404)

    wasactive = credential.revokedat is None
    if wasactive:
        credential.revokedat = _naive_utcnow()
        credential.revokedby = _username()
    details = []
    if wasactive:
        details.append('endpoint credential {} revoked'.format(
            credential.credentialprefix))
    if blockreenroll:
        credential.reenrollblocked = True
        credential.reenrollblockedreason = reason
        details.append('re-enrollment blocked ({})'.format(reason or 'no reason'))
    AuditLog.log('deleted' if wasactive else 'updated', 'EndpointCredential',
                 entityid=assetid, entityname=credential.credentialprefix,
                 details='; '.join(details))
    db.session.commit()
    return success_response(credential.to_dict(),
                            message='Endpoint credential revoked')


@endpoints_bp.route('/enrollment/assets/<int:assetid>/allow-reenroll',
                    methods=['POST'])
@require_role('admin')
def allow_endpoint_reenroll(assetid):
    """Lift a re-enrollment block. The PC enrolls on its next attempt."""
    credential = EndpointCredential.query.filter_by(assetid=assetid).first()
    if credential is None:
        return error_response(ErrorCodes.NOT_FOUND,
                              'This computer has no credential record',
                              http_code=404)
    if not credential.reenrollblocked:
        return success_response(credential.to_dict(),
                                message='Re-enrollment was not blocked')
    previous = credential.reenrollblockedreason
    credential.reenrollblocked = False
    credential.reenrollblockedreason = None
    AuditLog.log('updated', 'EndpointCredential', entityid=assetid,
                 entityname=credential.credentialprefix,
                 changes={'reenrollblocked': {'old': True, 'new': False}},
                 details='re-enrollment allowed again (was blocked: {})'.format(
                     previous or 'no reason'))
    db.session.commit()
    return success_response(credential.to_dict(),
                            message='Re-enrollment allowed')


@endpoints_bp.route('/enrollment/settings', methods=['PUT'])
@require_role('admin')
def update_enrollment_settings():
    from shopdb.api import Setting

    payload = request.get_json(silent=True) or {}
    changes = {}
    for key, settingkey in (('sharedkeyallowed', agentauth.SHARED_KEY_SETTING),
                            ('autoenroll', agentauth.AUTO_ENROLL_SETTING)):
        if key not in payload:
            continue
        if not isinstance(payload[key], bool):
            return error_response(ErrorCodes.VALIDATION_ERROR,
                                  f'{key} must be true or false')
        changes[key] = (settingkey, payload[key], 'boolean')

    if 'maxpendingenrollments' in payload:
        value = payload['maxpendingenrollments']
        if isinstance(value, bool) or not isinstance(value, int) or value < 0:
            return error_response(
                ErrorCodes.VALIDATION_ERROR,
                'maxpendingenrollments must be 0 or a positive whole number')
        changes['maxpendingenrollments'] = (PENDING_CAP_SETTING, value,
                                            'integer')

    if not changes:
        return error_response(
            ErrorCodes.VALIDATION_ERROR,
            'Send sharedkeyallowed, autoenroll and/or maxpendingenrollments')

    before = _settings_payload()
    for key, (settingkey, value, valuetype) in changes.items():
        Setting.set(settingkey, value, valuetype=valuetype,
                    category='plugin.endpoints')
    after = _settings_payload()
    AuditLog.log('updated', 'Setting', entityname='endpoint enrollment',
                 changes={key: {'old': before[key], 'new': after[key]}
                          for key in changes},
                 details='endpoint enrollment settings changed')
    db.session.commit()
    return success_response(after, message='Enrollment settings saved')


# ---------------------------------------------------------------------------
# Migration of PCs already in the fleet
# ---------------------------------------------------------------------------

def _version_below(reported, target):
    parsed = parse_agent_version(reported)
    wanted = parse_agent_version(target)
    if parsed is None or wanted is None:
        return True
    width = max(len(parsed), len(wanted))
    return (tuple(parsed) + (0,) * (width - len(parsed))
            < tuple(wanted) + (0,) * (width - len(wanted)))


def _upgrade_scriptid():
    from .agentupgradescript import UPGRADE_SCRIPT_NAME

    script = Script.query.filter_by(scriptname=UPGRADE_SCRIPT_NAME).first()
    return script.scriptid if script is not None else None


def _store_has_package():
    from . import agentstore

    current = agentstore.current_version('agent')
    if current is None:
        return agentstore.current_path('agent') is not None
    return not _version_below(current, CREDENTIAL_AGENT_VERSION)


def _latest_commands(assetids, target=None):
    """The newest run_script command per asset (optionally for one target)."""
    if not assetids:
        return {}
    newest = (db.session.query(db.func.max(EndpointCommand.endpointcommandid))
              .filter(EndpointCommand.assetid.in_(assetids),
                      EndpointCommand.action == 'run_script'))
    if target is not None:
        newest = newest.filter(EndpointCommand.target == target)
    newest = newest.group_by(EndpointCommand.assetid)
    return {command.assetid: command for command in EndpointCommand.query
            .filter(EndpointCommand.endpointcommandid.in_(newest)).all()}


def _is_tls_trust_failure(command):
    if command is None or command.status != EndpointCommand.STATUS_FAILED:
        return False
    text = '{} {}'.format(command.resultmessage or '',
                          command.resultjson or '').lower()
    return any(marker in text for marker in _TLS_TRUST_FAILURES)


def is_trust_retryable(blockers):
    """True when nothing blocks the PC but, at most, the certificate trust failure.

    The server only learns about trust from the PC's last failed download, so
    that blocker cannot clear by itself. An admin who fixed trust may queue the
    PC by id; a wave picking the next ready PCs never does.
    """
    return all(blocker == BLOCKER_CERT_UNTRUSTED for blocker in blockers)


def compute_readiness(assetids=None):
    """Migration state for every active computer (or just assetids).

    Returns a list of dicts ordered by hostname: assetid, hostname,
    agentversion, lastreportedat, state, blockers.
    """
    computers = _computers()
    hostnamecounts = Counter((hostname or '').lower()
                             for _assetid, hostname, _serial in computers)
    if assetids is not None:
        wanted = set(assetids)
        computers = [row for row in computers if row[0] in wanted]
    if not computers:
        return []

    ids = [row[0] for row in computers]
    credentialrows = EndpointCredential.query.filter(
        EndpointCredential.assetid.in_(ids)).all()
    active = {c.assetid for c in credentialrows if c.revokedat is None}
    reenrollblocked = {c.assetid for c in credentialrows
                       if c.reenrollblocked and c.revokedat is not None}
    index = _pending_index(_pending_requests())
    states = {s.assetid: s for s in
              EndpointState.query.filter(EndpointState.assetid.in_(ids)).all()}

    scriptid = _upgrade_scriptid()
    upgrading = set()
    if scriptid is not None:
        upgrading = {row[0] for row in db.session.query(EndpointCommand.assetid)
                     .filter(EndpointCommand.assetid.in_(ids),
                             EndpointCommand.action == 'run_script',
                             EndpointCommand.target == f'script:{scriptid}',
                             EndpointCommand.status.in_(
                                 (EndpointCommand.STATUS_PENDING,
                                  EndpointCommand.STATUS_RUNNING)))}

    lastscripts = _latest_commands(ids)

    haspackage = _store_has_package()
    minimum = minimum_agent_version_for('run_script')
    offlinecutoff = _naive_utcnow() - _OFFLINE_AFTER

    result = []
    for assetid, hostname, serialnumber in computers:
        state = states.get(assetid)
        agentversion = state.agentversion if state is not None else None
        lastreportedat = state.lastreportedat if state is not None else None
        blockers = []
        if assetid in active:
            status = 'enrolled'
        elif assetid in reenrollblocked:
            status = 'blocked'
            blockers.append(BLOCKER_REENROLL_BLOCKED)
        elif _is_pending(assetid, hostname, index):
            status = 'pending'
        elif assetid in upgrading:
            status = 'upgrading'
        elif state is None:
            status = 'notreporting'
        else:
            if lastreportedat is None or lastreportedat < offlinecutoff:
                blockers.append(BLOCKER_OFFLINE)
            if not (serialnumber or '').strip():
                blockers.append(BLOCKER_NO_SERIAL)
            if hostnamecounts[(hostname or '').lower()] > 1:
                blockers.append(BLOCKER_DUPLICATE_HOSTNAME)
            if ACTIVE_LOCK_FOR(assetid) is not None:
                blockers.append(BLOCKER_LOCKED)
            if not haspackage:
                blockers.append(BLOCKER_NO_PACKAGE)
            if minimum and not agent_meets_minimum(agentversion, minimum):
                blockers.append(BLOCKER_TOO_OLD)
            if _is_tls_trust_failure(lastscripts.get(assetid)):
                blockers.append(BLOCKER_CERT_UNTRUSTED)
            if not _version_below(agentversion, CREDENTIAL_AGENT_VERSION):
                blockers.append(BLOCKER_AWAITING_ENROLLMENT)
            if (is_trust_retryable(blockers)
                    and 'run_script' not in ALLOWED_ACTIONS_FOR(assetid=assetid)):
                blockers.append(BLOCKER_POLICY)
            status = 'blocked' if blockers else 'ready'
        result.append({
            'assetid': assetid,
            'hostname': hostname,
            'agentversion': agentversion,
            'lastreportedat': _utciso(lastreportedat),
            'state': status,
            'blockers': blockers,
        })
    return result


def _wave_progress(wave, scriptid):
    """Live progress of one wave.

    failed counts a member only while it is still stuck: its newest agent
    upgrade (from any wave or a single push) failed or expired, it is not
    enrolled, and it does not report an agent at or above the credential
    version. A PC a later wave upgraded stops counting here.
    """
    members = wave.assetidlist
    enrolled = set()
    failed = set()
    queued = set()
    if members:
        enrolled = {c.assetid for c in EndpointCredential.query.filter(
            EndpointCredential.assetid.in_(members),
            EndpointCredential.revokedat.is_(None)).all()}
        if scriptid is not None:
            target = f'script:{scriptid}'
            queued = {row[0] for row in db.session.query(EndpointCommand.assetid)
                      .filter(EndpointCommand.assetid.in_(members),
                              EndpointCommand.action == 'run_script',
                              EndpointCommand.target == target,
                              EndpointCommand.createdat >= wave.createdat)
                      .distinct()}
            versions = dict(db.session.query(EndpointState.assetid,
                                             EndpointState.agentversion)
                            .filter(EndpointState.assetid.in_(members)).all())
            failed = {assetid for assetid, command
                      in _latest_commands(members, target).items()
                      if assetid not in enrolled
                      and command.status in (EndpointCommand.STATUS_FAILED,
                                             EndpointCommand.STATUS_EXPIRED)
                      and _version_below(versions.get(assetid),
                                         CREDENTIAL_AGENT_VERSION)}
    return {
        'waveid': wave.waveid,
        'createdat': _utciso(wave.createdat),
        'createdby': wave.createdby,
        'size': len(members),
        'queued': len(queued),
        'enrolled': len(enrolled),
        'failed': len(failed),
        'done': len(enrolled) + len(failed) >= len(members),
    }


@endpoints_bp.route('/enrollment/migration', methods=['GET'])
@require_permission('endpoints.fleet')
def get_enrollment_migration():
    """Per-computer readiness to move onto per-PC credentials, plus waves."""
    rows = compute_readiness()
    counts = Counter(row['state'] for row in rows)

    state = (request.args.get('state') or '').strip().lower()
    if state:
        if state not in MIGRATION_STATES:
            return error_response(ErrorCodes.VALIDATION_ERROR,
                                  f'Unknown state filter: {state!r}')
        rows = [row for row in rows if row['state'] == state]
    rows = _search_filter(rows, (request.args.get('search') or '').strip(),
                          'hostname', 'agentversion')
    pagerows, pagination = _page(rows)

    scriptid = _upgrade_scriptid()
    waves = (EndpointMigrationWave.query
             .order_by(EndpointMigrationWave.createdat.desc())
             .limit(_RECENT_REQUESTS)
             .all())

    return success_response({
        'target': CREDENTIAL_AGENT_VERSION,
        'counts': {name: counts[name] for name in MIGRATION_STATES},
        'computers': pagerows,
        'waves': [_wave_progress(wave, scriptid) for wave in waves],
    }, meta={'pagination': pagination})


def _response_message(response):
    try:
        body = response.get_json() or {}
    except Exception:  # noqa: BLE001 - reason text only
        return 'enqueue refused'
    error = ((body.get('data') or {}).get('error') or {})
    return error.get('message') or body.get('message') or 'enqueue refused'


@endpoints_bp.route('/enrollment/migration/wave', methods=['POST'])
@require_role('admin')
def create_migration_wave():
    """Push the agent upgrade to a batch of READY PCs.

    Body {"assetids": [...]} or {"next": n}. Readiness is re-checked per PC; the
    agent is packaged once for the whole wave, then each PC is queued through
    the same path as POST /<asset>/agentupgrade. An explicit id whose only
    blocker is the certificate trust failure is queued too and listed in
    retried: the admin is saying trust was fixed.
    """
    from .routes import prepare_agent_upgrade, queue_prepared_agent_upgrade

    payload = request.get_json(silent=True) or {}
    requested = payload.get('assetids')
    nextcount = payload.get('next')

    if requested is not None:
        if (not isinstance(requested, list) or not requested
                or not all(isinstance(v, int) and not isinstance(v, bool)
                           for v in requested)):
            return error_response(ErrorCodes.VALIDATION_ERROR,
                                  'assetids must be a non-empty list of integers')
        if len(requested) > _WAVE_MAXIMUM:
            return error_response(ErrorCodes.VALIDATION_ERROR,
                                  f'A wave holds at most {_WAVE_MAXIMUM} PCs')
        candidates = list(dict.fromkeys(requested))
    elif nextcount is not None:
        if (isinstance(nextcount, bool) or not isinstance(nextcount, int)
                or nextcount < 1 or nextcount > _WAVE_MAXIMUM):
            return error_response(ErrorCodes.VALIDATION_ERROR,
                                  f'next must be an integer from 1 to {_WAVE_MAXIMUM}')
        candidates = [row['assetid'] for row in compute_readiness()
                      if row['state'] == 'ready'][:nextcount]
    else:
        return error_response(ErrorCodes.VALIDATION_ERROR,
                              'Send assetids or next')

    readiness = {row['assetid']: row for row in compute_readiness(candidates)}
    skipped = []
    ready = []
    retrying = set()
    for assetid in candidates:
        row = readiness.get(assetid)
        if row is None:
            skipped.append({'assetid': assetid, 'reason': 'not a computer'})
        elif (requested is not None and row['state'] == 'blocked'
              and row['blockers'] and is_trust_retryable(row['blockers'])):
            retrying.add(assetid)
            ready.append(assetid)
        elif row['state'] != 'ready':
            reason = ', '.join(row['blockers']) if row['blockers'] else row['state']
            skipped.append({'assetid': assetid, 'reason': reason})
        else:
            ready.append(assetid)

    queued = []
    waveid = None
    if ready:
        startedat = _naive_utcnow().replace(microsecond=0)
        registration, seeded, error = prepare_agent_upgrade()
        if error is not None:
            return error
        for assetid in ready:
            response = queue_prepared_agent_upgrade(assetid, registration,
                                                    seeded, {})
            if getattr(response, 'status_code', None) == 201:
                queued.append(assetid)
            else:
                db.session.rollback()
                skipped.append({'assetid': assetid,
                                'reason': _response_message(response)})

        if queued:
            wave = EndpointMigrationWave(
                createdat=startedat, createdby=_username(),
                assetids=','.join(str(v) for v in queued))
            db.session.add(wave)
            db.session.flush()
            waveid = wave.waveid
            AuditLog.log('created', 'EndpointMigrationWave', entityid=waveid,
                         entityname='agent {}'.format(registration['agentversion']),
                         details='migration wave queued agent upgrade for {} PC(s): {}'
                                 .format(len(queued), wave.assetids))
            db.session.commit()

    retried = [assetid for assetid in queued if assetid in retrying]
    return success_response(
        {'waveid': waveid, 'queued': queued, 'skipped': skipped,
         'retried': retried},
        message='{} PC(s) queued'.format(len(queued)),
        http_code=201 if queued else 200)


# ---------------------------------------------------------------------------
# Dashboard
# ---------------------------------------------------------------------------

@endpoints_bp.route('/dashboard/enrollmentpending', methods=['GET'])
@require_permission('endpoints.fleet')
def dashboard_enrollment_pending():
    """One queue row while enroll requests wait for an admin, else nothing.

    A count rather than a row per PC: the decision is made on the Enrollment
    page, where the asset picker is, so the dashboard only has to say go there.
    """
    count = (db.session.query(db.func.count(EndpointEnrollRequest.requestid))
             .filter(_awaiting_admin_filter())
             .scalar()) or 0
    if not count:
        return success_response([])
    return success_response([{
        'summary': '{} PC{} waiting for enrollment approval'.format(
            count, '' if count == 1 else 's'),
        'pendingcount': count,
    }])


@endpoints_bp.route('/dashboard/reenrollblocked', methods=['GET'])
@require_permission('endpoints.fleet')
def dashboard_reenroll_blocked():
    """PCs kept from re-enrolling for more than 7 days.

    A block is the first step of a rollback and is meant to be lifted again.
    There is no separate block timestamp: revokedat is when the credential
    stopped working, which is when the rollback started.
    """
    Computer = _computer_model()
    cutoff = _naive_utcnow() - _BLOCKED_ATTENTION_AFTER
    now = _naive_utcnow()
    rows = (db.session.query(EndpointCredential, Computer.computerid,
                             Computer.hostname)
            .join(Computer, Computer.assetid == EndpointCredential.assetid)
            .join(Asset, Asset.assetid == EndpointCredential.assetid)
            .filter(Asset.isactive.is_(True),
                    EndpointCredential.reenrollblocked.is_(True),
                    EndpointCredential.revokedat.isnot(None),
                    EndpointCredential.revokedat < cutoff)
            .order_by(EndpointCredential.revokedat.asc())
            .limit(50)
            .all())
    return success_response([{
        'computerid': computerid,
        'assetid': credential.assetid,
        'hostname': hostname,
        'blockeddays': (now - credential.revokedat).days,
        'reason': credential.reenrollblockedreason,
    } for credential, computerid, hostname in rows])