"""Backups plugin main class.

Per-asset configuration backups with revision history, pluggable by kind
(services/registry.py). Accepts collector input over HTTPS per ADR-006 and
renders one asset panel per kind via the ADR-010 hook.

Dedup is the load-bearing behaviour: GE-Enforce runs the collector every cycle
across the fleet, so apply_collector_payload inserts a revision only when the
content hash differs from that asset's latest for that kind. Without it a
readable history would be buried under millions of identical rows.
"""

import base64
import json
import logging
from datetime import datetime, timezone
from pathlib import Path
from typing import Dict, List, Optional, Type

from flask import Flask, Blueprint

from shopdb.plugins.base import BasePlugin, PluginMeta

from .api import backups_bp
from .models import BackupRevision
from .services.registry import (REGISTRY, getkind, canonicalhash,
                               DEFAULTSHAREROOT)
from .services.retention import prune

logger = logging.getLogger(__name__)


class BackupsPlugin(BasePlugin):
    """Configuration backup + revision history plugin."""

    def __init__(self):
        self._manifest = self._load_manifest()

    def _load_manifest(self) -> Dict:
        manifest_path = Path(__file__).parent / 'manifest.json'
        if manifest_path.exists():
            with open(manifest_path, 'r') as f:
                return json.load(f)
        return {}

    @property
    def meta(self) -> PluginMeta:
        return PluginMeta(
            name=self._manifest.get('name', 'backups'),
            version=self._manifest.get('version', '1.0.0'),
            description=self._manifest.get('description', 'Configuration backups'),
            author=self._manifest.get('author', 'ShopDB Team'),
            dependencies=self._manifest.get('dependencies', []),
            core_version=self._manifest.get('core_version', '>=0.2.0,<1.0.0'),
            api_prefix=self._manifest.get('api_prefix', '/api/backups'),
        )

    def get_blueprint(self) -> Optional[Blueprint]:
        return backups_bp

    def get_models(self) -> List[Type]:
        return [BackupRevision]

    def get_permissions(self) -> List:
        """RBAC for the human-facing routes.

        Deliberately split: download is separate from view because a .reg is a
        restorable artifact, so a read-only auditor should be able to see that a
        machine's config changed without being able to pull a file that
        reconfigures it.

        No delete permission. Revisions are removed only by the retention
        policy; a hand-delete route would let someone quietly drop the evidence
        of a config change, and there is no operational need for it. Collector
        INGEST is not covered here at all - that path authorizes on a
        collector.ingest-scoped service token, not a user JWT.
        """
        return [
            ('backups.view', 'View configuration backups', 'backups'),
            ('backups.download', 'Download configuration backups', 'backups'),
        ]

    def get_asset_panels(self) -> List[Dict]:
        """One panel per kind, plus the DNC Info card.

        DNC Info sits ABOVE the history panels (lower position) because it
        answers the question a tech actually arrives with - what is this
        machine's controller talking to - while the history panels are for the
        rarer restore case.
        """
        panels = [kind.infopanel() for kind in REGISTRY.values()
                  if kind.infopanel()]
        for position, kind in enumerate(REGISTRY.values()):
            panel = {
                'id': 'backups-{}'.format(kind.key),
                'title': kind.displayname,
                'assettypes': list(kind.assettypes),
                'endpoint': '/api/backups/asset/{assetid}?kind=' + kind.key,
                'render': 'list',
                'map': {
                    'title': 'label',
                    'meta': [
                        {'key': 'collectedat', 'label': 'Captured', 'format': 'date'},
                        {'key': 'sourcehostname', 'label': 'From'},
                        {'key': 'shorthash', 'label': 'Hash', 'mono': True},
                    ],
                },
                # The generic renderer has no per-item actions, and downloading
                # a .reg needs a per-revision control plus a dialect choice, so
                # the panel links to the plugin's own history view instead.
                'manage': {
                    'to': '/backups/asset/{assetid}',
                    'label': 'History / download',
                    'emptylabel': 'View history',
                },
                'position': 40 + position,
            }
            # OMIT 'empty' entirely unless the kind sets it. The list renderer
            # shows a panel when it has rows OR declares empty text, so a
            # present-but-null 'empty' would still render the panel on every
            # asset of the type. Most machines are not part markers and never
            # will be, so that panel must disappear rather than announce it has
            # nothing.
            if kind.emptytext:
                panel['empty'] = kind.emptytext
            panels.append(panel)
        return panels

    def get_settings_defaults(self) -> List[Dict]:
        """Schedule + retention, read by the collector and the prune job.

        The interval lives here rather than in the manifest entry because
        GE-Enforce fires every cycle (several times a day on a shift change).
        The collector reads backups_intervalhours and no-ops when its marker
        file is younger than that, so the cadence is changed centrally in
        ShopDB instead of by editing a script on the share.
        """
        return [
            {
                'key': 'backups_intervalhours',
                'value': '24',
                'valuetype': 'integer',
                'category': 'backups',
                'description': 'Minimum hours between collection attempts on a '
                               'PC. GE-Enforce runs every cycle; the collector '
                               'skips until this much time has passed.',
            },
            {
                'key': 'backups_shareroot',
                'value': DEFAULTSHAREROOT,
                'valuetype': 'string',
                'category': 'backups',
                'description': 'UNC root that opaque (non-JSON) backups are '
                               'written under by the collecting PC. Site-specific.',
            },
            {
                'key': 'backups_retentioncount',
                'value': '50',
                'valuetype': 'integer',
                'category': 'backups',
                'description': 'Distinct revisions kept per asset per kind. '
                               '0 keeps everything. The newest and the oldest '
                               'are never pruned.',
            },
            {
                'key': 'backups_retentiondays',
                'value': '0',
                'valuetype': 'integer',
                'category': 'backups',
                'description': 'Also prune revisions older than this many days. '
                               '0 disables age-based pruning.',
            },
        ]

    # ---- ADR-006 collector contract -------------------------------------

    def get_collector_schema(self) -> Optional[dict]:
        return {
            'identityfield': 'machinenumber',
            'fields': {
                'type': 'object',
                'required': ['machinenumber', 'backupkind'],
                'properties': {
                    'machinenumber': {
                        'type': 'string',
                        'description': 'Machine number the config belongs to. '
                                       'Resolved against assets.assetnumber.',
                    },
                    'backupkind': {
                        'type': 'string',
                        'enum': sorted(REGISTRY.keys()),
                    },
                    'contentbase64': {
                        'type': 'string',
                        'description': "Raw backup file, base64. Required for "
                                       "'shopdb' kinds (parsed server-side).",
                    },
                    'contenthash': {
                        'type': 'string',
                        'description': "sha256 of the file. Required for 'share' "
                                       "kinds, whose bytes stay on the SFLD share.",
                    },
                    'sharepath': {
                        'type': 'string',
                        'description': "Full UNC path. Required for 'share' kinds.",
                    },
                    'sourcefilename': {'type': 'string'},
                    'sourcehostname': {
                        'type': 'string',
                        'description': 'PC the backup was read from. For NTLARS '
                                       'this is the controlling PC, not the machine.',
                    },
                    'collectedat': {'type': 'string', 'format': 'date-time'},
                    'bytesize': {'type': 'integer'},
                },
            },
        }

    def apply_collector_payload(self, payload: dict) -> dict:
        from shopdb.api import db

        warnings = []
        kindkey = (payload.get('backupkind') or '').strip().lower()
        kind = getkind(kindkey)
        if kind is None:
            raise ValueError('unknown backupkind: {!r}'.format(kindkey))

        assetid, err = kind.resolveassetid(payload)
        if assetid is None:
            # Unresolvable is reported, never silently dropped - an unmatched
            # machine number means a real gap between the fleet and ShopDB.
            raise ValueError('could not resolve asset: {}'.format(err))

        projection = None
        sharepath = None
        sourcefilename = payload.get('sourcefilename')
        bytesize = payload.get('bytesize')

        if kind.storagebackend == 'shopdb':
            encoded = payload.get('contentbase64')
            if not encoded:
                raise ValueError(
                    "contentbase64 is required for kind '{}'".format(kindkey))
            raw = base64.b64decode(encoded)
            bytesize = bytesize or len(raw)
            projection = kind.parse(raw)
            contenthash = canonicalhash(projection)

            # The fleet's machine number (pc-config.txt) is authoritative for
            # WHICH asset this belongs to, but NTLARS carries its own MachineNo.
            # A disagreement means the PC is running another machine's config -
            # worth surfacing rather than quietly filing under the reported one.
            embedded = getattr(kind, 'embeddedmachineno', None)
            if embedded is not None:
                embeddedno = embedded(projection)
                reported = (payload.get('machinenumber') or '').strip()
                if embeddedno and reported and embeddedno != reported:
                    warnings.append(
                        'reported machine number {!r} but NTLARS is configured '
                        'for {!r}'.format(reported, embeddedno))
        else:
            contenthash = (payload.get('contenthash') or '').strip().lower()
            sharepath = (payload.get('sharepath') or '').strip()
            if not contenthash or not sharepath:
                raise ValueError(
                    "contenthash and sharepath are required for kind '{}'".format(
                        kindkey))

        # with_for_update serializes concurrent posts for the same asset+kind.
        # The whole fleet collects on the same GE-Enforce cycle, so a retry or
        # two PCs claiming one machine number can otherwise both pass the hash
        # check and insert duplicate identical revisions. No unique constraint
        # can cover this: dedup is against the LATEST row only, because a config
        # reverting to an earlier state is a legitimate new revision.
        latest = (db.session.query(BackupRevision)
                  .filter(BackupRevision.assetid == assetid,
                          BackupRevision.backupkind == kindkey)
                  .order_by(BackupRevision.backuprevisionid.desc())
                  .with_for_update()
                  .first())

        if latest is not None and latest.contenthash == contenthash:
            return {
                'action': 'noop',
                'assetid': assetid,
                'backuprevisionid': latest.backuprevisionid,
                'warnings': warnings,
            }

        collectedat = None
        rawcollected = payload.get('collectedat')
        if rawcollected:
            try:
                collectedat = datetime.fromisoformat(rawcollected.replace('Z', '+00:00'))
                if collectedat.tzinfo is not None:
                    # Convert, don't just drop the offset: createdat is utcnow(),
                    # so keeping local wall time would skew a -04:00 bay by 4h
                    # against its own history.
                    collectedat = collectedat.astimezone(timezone.utc).replace(
                        tzinfo=None)
            except ValueError:
                warnings.append('unparseable collectedat: {!r}'.format(rawcollected))

        revision = BackupRevision(
            assetid=assetid,
            backupkind=kindkey,
            storagebackend=kind.storagebackend,
            contenthash=contenthash,
            sharepath=sharepath,
            sourcefilename=sourcefilename,
            bytesize=bytesize,
            sourcehostname=payload.get('sourcehostname'),
            collectedat=collectedat or datetime.utcnow(),
        )
        revision.payload = projection
        db.session.add(revision)
        # flush, not commit: the collector dispatcher owns the transaction and
        # commits after writing its AuditLog row. Committing here would leave an
        # unaudited revision behind if that write then failed.
        db.session.flush()

        pruned = prune(
            assetid, kindkey,
            retentioncount=self.get_setting('backups_retentioncount', 0),
            retentiondays=self.get_setting('backups_retentiondays', 0),
        )
        if pruned:
            warnings.append('pruned {} old revision(s) per retention policy'
                            .format(pruned))

        return {
            'action': 'created',
            'assetid': assetid,
            'backuprevisionid': revision.backuprevisionid,
            'warnings': warnings,
        }

    def init_app(self, app: Flask, db_instance) -> None:
        logger.info('Backups plugin initialized (v%s, kinds: %s)',
                    self.meta.version, ', '.join(sorted(REGISTRY)))