"""Backups API routes.

Admin-only surface over the site's backup sets. The heavy lifting (mysqldump,
restic snapshot of the instance tree, retention prune, integrity check) runs in
the one-shot backup container defined in docker-compose.backup.yml; this
blueprint is the read-mostly control plane the UI talks to.

Two recovery products stay firewalled, per the design notes:
  - code rollback lives in git (tags/releases), NOT here
  - data restore lives here, gated on schema compatibility via each set's manifest

Every backup set carries a manifest.json stamped with the core + plugin Alembic
revisions and the running image tag at capture time. A restore is a CHECKED
operation: current code must be at least the set's schema revision, so we never
load rows that reference a column the live schema has not applied yet.
"""

import json
import os
import subprocess
from datetime import datetime, timezone

from flask import Blueprint, current_app, request

from shopdb.core.models import AuditLog
from shopdb.core.models.setting import Setting
from shopdb.utils.responses import success_response, error_response, ErrorCodes
from shopdb.utils.authz import require_role

shopdbbackups_bp = Blueprint('shopdbbackups', __name__)

# Supported backup destination kinds. 'local' needs no credentials; 'smb' and
# 'aws' are ground-wired here so operators can configure them now, but their
# client libraries are held back until the security review clears them, so the
# runner treats a non-local destination as configured-but-not-yet-armed.
DESTINATION_KINDS = ('local', 'smb', 'aws')

# The setting keys that make up each destination's config, grouped by kind so
# the GET can surface only the relevant fields and the PUT can validate what it
# is allowed to write. Secret keys (password/secret/token in the name) are
# masked by the shared settings serializer, same convention as SMTP/SAML.
DESTINATION_FIELDS = {
    'local': [],
    'smb': [
        'backup_smb_host',
        'backup_smb_share',
        'backup_smb_path',
        'backup_smb_username',
        'backup_smb_password',
    ],
    'aws': [
        'backup_aws_region',
        'backup_aws_bucket',
        'backup_aws_prefix',
        'backup_aws_accesskeyid',
        'backup_aws_secretaccesskey',
    ],
}

# Keys whose value must never leave the API in the clear. Mirrors the shared
# settings convention (_is_secret) so the two surfaces agree on what is secret.
_SECRET_TOKENS = ('password', 'secret', 'token')
SECRET_MASK = '********'


def _is_secret_key(key):
    return any(token in key for token in _SECRET_TOKENS)

# Where the backup container drops each set and its manifest. Mounted read-only
# for the api container so the UI can enumerate sets without being able to
# mutate them; writes happen only from the backup one-shot.
BACKUPS_ROOT_ENV = 'SHOPDB_BACKUPS_ROOT'
DEFAULT_BACKUPS_ROOT = '/backups'

# Retention the backup container enforces; surfaced read-only so the UI can show
# "day 1 of 5 retained" without re-deriving the policy.
RETENTION = {
    'keepdaily': 5,
    'keepweekly': 4,
    'keepmonthly': 6,
}


def _backups_root():
    return os.environ.get(BACKUPS_ROOT_ENV, DEFAULT_BACKUPS_ROOT)


def _backups_configured():
    """Whether this deployment has a backup store behind the feature.

    The overlay is a compose profile: a third container writes the sets onto a
    shared volume, and the api container only ever reads them and drops a
    sentinel. A Windows/IIS install has no such container, and the default root
    resolves there to a drive-letter path nothing creates - so every button
    either 500s on PermissionError or reports 'queued' for a run that will
    never happen. Answer the caller honestly instead.
    """
    return os.path.isdir(_backups_root())


def _unavailable_response():
    # 404 + NOT_FOUND is the established shape for "this feature is not
    # enabled here" (the configuration-policy routes answer the same way), and
    # the UI already tells a 404 apart from a real failure.
    return error_response(
        ErrorCodes.NOT_FOUND,
        'Site Backups is not configured on this deployment. It needs the '
        'backup overlay and a readable backups root (%s).' % BACKUPS_ROOT_ENV,
        http_code=404)


def _read_json(path):
    """Load a JSON file, or None when it is absent or unreadable."""
    try:
        with open(path, 'r', encoding='utf-8') as handle:
            return json.load(handle)
    except (OSError, ValueError):
        return None


def _read_status(kind):
    """Return the live status dict for a run kind, or None when idle."""
    root = _backups_root()
    return _read_json(os.path.join(root, '.' + kind + '-status.json'))


def _read_history(kind):
    """Return the recorded run history for a kind, newest first."""
    root = _backups_root()
    entries = _read_json(os.path.join(root, 'history', kind + 's.json'))
    if not isinstance(entries, list):
        return []
    return list(reversed(entries))


def _write_status(kind, phase, setname, message):
    """Seed a live status file so the UI shows movement the instant a run is
    queued, before the watcher has picked up the sentinel."""
    root = _backups_root()
    stamp = datetime.now(timezone.utc).replace(tzinfo=None).isoformat() + 'Z'
    payload = {
        'kind': kind,
        'phase': phase,
        'setname': setname,
        'message': message,
        'updatedat': stamp,
    }
    try:
        path = os.path.join(root, '.' + kind + '-status.json')
        with open(path, 'w', encoding='utf-8') as handle:
            json.dump(payload, handle)
    except OSError:
        pass


def _append_history(kind, outcome, setname, message):
    """Append one run record to the shared history the UI reads, newest last.

    Mirrors status.sh's history_append so a finalize that completes in the api
    (not the sidecar) still lands in the same history file the restore page
    shows. Best-effort: history is a convenience log, never a gate.
    """
    root = _backups_root()
    stamp = datetime.now(timezone.utc).replace(tzinfo=None).isoformat() + 'Z'
    entry = {
        'kind': kind,
        'outcome': outcome,
        'setname': setname,
        'message': message,
        'at': stamp,
    }
    path = os.path.join(root, 'history', kind + 's.json')
    try:
        os.makedirs(os.path.dirname(path), exist_ok=True)
        entries = _read_json(path)
        if not isinstance(entries, list):
            entries = []
        entries.append(entry)
        with open(path, 'w', encoding='utf-8') as handle:
            json.dump(entries, handle)
    except OSError:
        pass


def _run_schema_upgrade():
    """Bring the just-restored database up to the running code, in-process.

    Runs the same two idempotent steps every deploy runs: the core Alembic
    upgrade to head, then each plugin chain via the plugin manager. Both are
    no-ops when the data already matches the code head, so this is safe to call
    even when the restored dump was already current. Uses the live app context
    and its configured engine, so no subprocess or extra Flask CLI is needed.
    """
    from flask_migrate import upgrade as alembic_upgrade

    alembic_upgrade()

    manager = current_app.extensions.get('plugin_manager')
    if manager is None:
        raise RuntimeError('Plugin manager not initialized; cannot upgrade plugins')
    results = manager.upgrade_all_plugins()
    failed = {name: status for name, status in (results or {}).items()
              if status not in ('ok', 'no-migrations')}
    if failed:
        raise RuntimeError('Plugin upgrade failed: ' + json.dumps(failed))



def _read_manifest(setdir):
    """Load a set's manifest.json, or None when absent/unreadable.

    A set without a readable manifest is not restorable (we cannot check its
    schema), so callers treat None as "unverified" rather than trusting it.
    """
    path = os.path.join(setdir, 'manifest.json')
    try:
        with open(path, 'r', encoding='utf-8') as handle:
            return json.load(handle)
    except (OSError, ValueError):
        return None


def _current_schema_revisions():
    """Return the live Alembic head revisions (core + plugins) for this build.

    Compared against a set's stamped revisions to decide restore compatibility.
    Imported lazily so a missing alembic at request time degrades to an empty
    map (everything reads as "unknown") instead of 500ing the list endpoint.
    """
    try:
        from alembic.config import Config
        from alembic.script import ScriptDirectory
    except ImportError:
        return {}

    root = current_app.root_path
    migrations = os.path.join(os.path.dirname(root), 'migrations')
    ini = os.path.join(migrations, 'alembic.ini')
    if not os.path.isfile(ini):
        return {}
    try:
        config = Config(ini)
        # This is a Flask-Migrate project: alembic.ini carries no
        # script_location (it is set at runtime), so ScriptDirectory.from_config
        # would raise and leave every set reading as incompatible. Point it at
        # the migrations directory - the same versions tree manifest.py scans.
        config.set_main_option('script_location', migrations)
        script = ScriptDirectory.from_config(config)
        return {'core': list(script.get_heads())}
    except Exception:
        return {}


def _known_core_revisions():
    """Return every core Alembic revision this build knows, heads and ancestors.

    Restore compatibility is now data-driven: a set restores when the running
    code KNOWS the dump's data revision (so `flask db upgrade` can roll it
    forward to head). Heads alone cannot answer that - a dump stamped at an
    older-but-valid revision is perfectly restorable - so we walk the whole
    script history. Lazy import + broad except keeps a missing/broken alembic
    from 500ing the list endpoint (returns empty = everything reads unknown).
    """
    try:
        from alembic.config import Config
        from alembic.script import ScriptDirectory
    except ImportError:
        return set()

    root = current_app.root_path
    migrations = os.path.join(os.path.dirname(root), 'migrations')
    ini = os.path.join(migrations, 'alembic.ini')
    if not os.path.isfile(ini):
        return set()
    try:
        config = Config(ini)
        config.set_main_option('script_location', migrations)
        script = ScriptDirectory.from_config(config)
        return {rev.revision for rev in script.walk_revisions()}
    except Exception:
        return set()


def _is_compatible(manifest, current):
    """Decide whether a set restores onto THIS build.

    Data-driven gate (the fix for the FBJXBDB4 outage): the authoritative
    signal is the set's `datarev` - the actual `alembic_version` of the dumped
    DATABASE, not the code head that captured it. A restore is safe when the
    running code KNOWS that revision (it is somewhere in this build's migration
    history), because then the post-restore finalize can run `flask db upgrade`
    to roll the loaded data forward to head. If the code does not know the
    revision, the dump is from a NEWER schema than this build and would 500 on
    restored rows, so we block until the code is upgraded.

    Legacy sets predate `datarev`; fall back to the old head-subset check on
    `schemarev` so they stay listable and restorable as before.
    """
    if not manifest:
        return False
    datarev = manifest.get('datarev')
    if datarev:
        known = _known_core_revisions()
        if not known:
            return False
        return datarev in known
    setrevs = set(manifest.get('schemarev', {}).get('core', []))
    currevs = set(current.get('core', []))
    if not setrevs or not currevs:
        return False
    # Compatible when the current heads cover every head the set was taken at.
    return setrevs.issubset(currevs)


# Reserved entries under the backups root that are not backup sets: the run
# history store and any dotfile sentinels/status files the watcher drops.
_NON_SET_ENTRIES = ('history',)


def _list_sets():
    """Enumerate backup sets newest-first, each summarized for the list view."""
    root = _backups_root()
    if not os.path.isdir(root):
        return []
    current = _current_schema_revisions()
    sets = []
    for name in sorted(os.listdir(root), reverse=True):
        if name in _NON_SET_ENTRIES or name.startswith('.'):
            continue
        setdir = os.path.join(root, name)
        if not os.path.isdir(setdir):
            continue
        manifest = _read_manifest(setdir)
        dbdump = os.path.join(setdir, 'db.sql.gz')
        sizebytes = 0
        for base, _dirs, files in os.walk(setdir):
            for filename in files:
                try:
                    sizebytes += os.path.getsize(os.path.join(base, filename))
                except OSError:
                    pass
        sets.append({
            'snapshotid': name,
            'takenat': (manifest or {}).get('takenat'),
            'sizebytes': sizebytes,
            'schemarev': (manifest or {}).get('schemarev', {}),
            'imagetag': (manifest or {}).get('imagetag'),
            'ischeckpassed': bool((manifest or {}).get('ischeckpassed')),
            'hasmanifest': manifest is not None,
            'hasdbdump': os.path.isfile(dbdump),
            'iscompatible': _is_compatible(manifest, current),
        })
    return sets


@shopdbbackups_bp.route('', methods=['GET'])
@require_role('admin')
def list_backups():
    """List every retained backup set, newest first, with a compatibility flag."""
    sets = _list_sets()
    laststgood = next((s for s in sets if s['ischeckpassed']), None)
    meta = {
        'retention': RETENTION,
        'lastgoodat': (laststgood or {}).get('takenat'),
        'count': len(sets),
        'configured': _backups_configured(),
    }
    return success_response(data=sets, meta=meta)


@shopdbbackups_bp.route('/<snapshotid>', methods=['GET'])
@require_role('admin')
def get_backup(snapshotid):
    """Return one set's full manifest plus a resolved compatibility verdict."""
    root = _backups_root()
    setdir = os.path.join(root, os.path.basename(snapshotid))
    if not os.path.isdir(setdir):
        return error_response(ErrorCodes.NOT_FOUND, 'Backup set not found',
                              http_code=404)
    manifest = _read_manifest(setdir)
    current = _current_schema_revisions()
    return success_response(data={
        'snapshotid': os.path.basename(snapshotid),
        'manifest': manifest,
        'currentschemarev': current,
        'iscompatible': _is_compatible(manifest, current),
        'hasmanifest': manifest is not None,
    })


@shopdbbackups_bp.route('', methods=['POST'])
@require_role('admin')
def trigger_backup():
    """Kick off an on-demand backup run.

    The api container cannot run docker; it writes a sentinel the host-side
    scheduler (or an operator running `docker compose run --rm backup`) picks
    up. Returning isrunning=false with a clear message keeps the UI honest
    rather than pretending the run started inside this process.
    """
    if not _backups_configured():
        return _unavailable_response()

    root = _backups_root()
    try:
        os.makedirs(root, exist_ok=True)
        sentinel = os.path.join(root, '.backup-requested')
        stamp = datetime.now(timezone.utc).replace(tzinfo=None).isoformat() + 'Z'
        with open(sentinel, 'w', encoding='utf-8') as handle:
            handle.write(stamp)
    except OSError as error:
        return error_response(ErrorCodes.INTERNAL_ERROR,
                              'Could not queue a backup: ' + str(error),
                              http_code=500)
    _write_status('backup', 'queued', '', 'Backup queued')
    AuditLog.log('requested', 'Backup', entityname=stamp)
    return success_response(
        data={'isrunning': False, 'isqueued': True, 'requestedat': stamp},
        message='Backup queued. The backup service runs it on its next pass.')


@shopdbbackups_bp.route('/<snapshotid>/restore', methods=['POST'])
@require_role('admin')
def restore_backup(snapshotid):
    """Queue a restore of a set, gated on schema compatibility.

    We refuse outright when the set is incompatible (current code older than the
    set's schema) so an operator cannot foot-gun a schema mismatch from the UI.
    The actual restore is performed by scripts/backup/restore.sh in the backup
    container; here we validate and record intent.
    """
    if not _backups_configured():
        return _unavailable_response()

    root = _backups_root()
    setdir = os.path.join(root, os.path.basename(snapshotid))
    if not os.path.isdir(setdir):
        return error_response(ErrorCodes.NOT_FOUND, 'Backup set not found',
                              http_code=404)
    manifest = _read_manifest(setdir)
    current = _current_schema_revisions()
    if not _is_compatible(manifest, current):
        return error_response(
            ErrorCodes.CONFLICT,
            'This backup was taken on a newer schema than the running code. '
            'Upgrade the code to at least the set\'s revision, run '
            '`flask db upgrade` and `flask plugin upgrade-all`, then retry.',
            details={'currentschemarev': current,
                     'setschemarev': (manifest or {}).get('schemarev', {})},
            http_code=409)
    try:
        sentinel = os.path.join(root, '.restore-requested')
        stamp = datetime.now(timezone.utc).replace(tzinfo=None).isoformat() + 'Z'
        with open(sentinel, 'w', encoding='utf-8') as handle:
            handle.write(os.path.basename(snapshotid))
    except OSError as error:
        return error_response(ErrorCodes.INTERNAL_ERROR,
                              'Could not queue the restore: ' + str(error),
                              http_code=500)
    _write_status('restore', 'queued', os.path.basename(snapshotid),
                  'Restore queued')
    AuditLog.log('restore-requested', 'Backup',
                 entityname=os.path.basename(snapshotid))
    return success_response(
        data={'isqueued': True, 'snapshotid': os.path.basename(snapshotid)},
        message='Restore queued and validated against the live schema.')


@shopdbbackups_bp.route('/finalize-restore', methods=['POST'])
@require_role('admin')
def finalize_restore():
    """Run the post-restore schema upgrade in the app context.

    The restore itself runs in the Flask-less backup sidecar, which loads the
    dump and then drops an .upgrade-requested sentinel because it cannot run
    'flask db upgrade' itself. This endpoint is the api-side half: it brings the
    just-restored DATA up to the running CODE with the exact idempotent commands
    the deploy path uses, then stamps the final 'done'. Without it a restored
    dump that sits at an older revision leaves every newer-migration table
    throwing 1054 Unknown column.

    Idempotent and safe to call when nothing is pending: if there is no
    .upgrade-requested sentinel it reports there was nothing to finalize.
    """
    if not _backups_configured():
        return _unavailable_response()

    root = _backups_root()
    sentinel = os.path.join(root, '.upgrade-requested')
    try:
        with open(sentinel, 'r', encoding='utf-8') as handle:
            setname = handle.read().strip()
    except OSError:
        return success_response(
            data={'finalized': False},
            message='No restore is awaiting schema upgrade.')

    _write_status('restore', 'upgrading', setname,
                  'Upgrading restored schema to code')
    try:
        _run_schema_upgrade()
    except Exception as error:  # noqa: BLE001 - report any upgrade failure
        _write_status('restore', 'failed', setname,
                      'Schema upgrade failed: ' + str(error))
        _append_history('restore', 'failed', setname,
                        'Schema upgrade failed: ' + str(error))
        return error_response(ErrorCodes.INTERNAL_ERROR,
                              'Post-restore schema upgrade failed: ' + str(error),
                              http_code=500)

    try:
        os.remove(sentinel)
    except OSError:
        pass
    _write_status('restore', 'done', setname, 'Restore complete')
    _append_history('restore', 'success', setname, 'Restore complete')
    AuditLog.log('restore-finalized', 'Backup', entityname=setname)
    return success_response(
        data={'finalized': True, 'snapshotid': setname},
        message='Restore finalized: schema upgraded to the running code.')


@shopdbbackups_bp.route('/status', methods=['GET'])
@require_role('admin')
def get_status():
    """Return the live status of the most recent backup and restore runs.

    The watcher writes these files as it moves through each phase; the UI polls
    this endpoint to drive the restore progress spinner and phase label. Either
    value is None when that kind of run has never been requested.
    """
    return success_response(data={
        'configured': _backups_configured(),
        'backup': _read_status('backup'),
        'restore': _read_status('restore'),
    })


@shopdbbackups_bp.route('/history', methods=['GET'])
@require_role('admin')
def get_history():
    """Return the recorded history of backup and restore runs, newest first.

    These are operational run logs written by the backup container onto the
    shared volume, not the audit trail (AuditLog records the requested intent).
    """
    return success_response(data={
        'backups': _read_history('backup'),
        'restores': _read_history('restore'),
    })


@shopdbbackups_bp.route('/settings', methods=['GET'])
@require_role('admin')
def get_backup_settings():
    """Return destination + retention config for the settings pane.

    The destination kind and its (non-secret) fields come from the settings
    store so an operator can configure where backups ship without editing env
    or redeploying. Secret fields (SMB password, AWS secret key) are never
    returned in the clear: we send a mask when a value is set and an empty
    string when it is not, matching the shared settings API convention.

    'smb' and 'aws' are configurable now but their client libraries are held
    back pending the security review, so we flag those destinations as armed:
    false to tell the UI the config is stored but not yet acting.
    """
    kind = Setting.get('backup_destination_kind', 'local')
    if kind not in DESTINATION_KINDS:
        kind = 'local'

    fields = {}
    for key in DESTINATION_FIELDS.get(kind, []):
        raw = Setting.get(key, '')
        if _is_secret_key(key):
            fields[key] = SECRET_MASK if raw else ''
        else:
            fields[key] = raw or ''

    return success_response(data={
        'destinationkind': kind,
        'destinationkinds': list(DESTINATION_KINDS),
        'fields': fields,
        'isarmed': kind == 'local',
        'retention': RETENTION,
        'backupsroot': _backups_root(),
    })


@shopdbbackups_bp.route('/settings', methods=['PUT'])
@require_role('admin')
def update_backup_settings():
    """Persist the backup destination kind and its credential/config fields.

    Only keys that belong to the chosen destination are accepted, so a stray
    payload cannot write arbitrary settings rows through this surface. A secret
    field submitted as the mask placeholder means "leave unchanged" - the
    client only ever received the mask, so we never overwrite a real secret
    with it.
    """
    data = request.get_json(silent=True) or {}
    kind = data.get('destinationkind', Setting.get('backup_destination_kind', 'local'))
    if kind not in DESTINATION_KINDS:
        return error_response(
            ErrorCodes.VALIDATION_ERROR,
            'destinationkind must be one of: ' + ', '.join(DESTINATION_KINDS))

    Setting.set('backup_destination_kind', kind, valuetype='string',
                category='backup')

    incoming = data.get('fields', {}) or {}
    allowed = set(DESTINATION_FIELDS.get(kind, []))
    for key, value in incoming.items():
        if key not in allowed:
            continue
        if _is_secret_key(key) and value == SECRET_MASK:
            continue
        Setting.set(key, value if value is not None else '',
                    valuetype='string', category='backup')

    AuditLog.log('updated', 'BackupSettings', entityname=kind, changes={
        'destinationkind': kind,
    })

    return get_backup_settings()