# Copyright (C) 2017  The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information

import smtplib
import psycopg2
from psycopg2.extras import RealDictCursor

from functools import wraps
from email.mime.text import MIMEText

from swh.model import hashutil
from swh.scheduler.backend import SchedulerBackend
from swh.scheduler.utils import create_oneshot_task_dict
from swh.vault.cache import VaultCache
from swh.vault.cookers import get_cooker
from swh.vault.cooking_tasks import SWHCookingTask  # noqa

cooking_task_name = 'swh.vault.cooking_tasks.SWHCookingTask'

NOTIF_EMAIL_FROM = ('"Software Heritage Vault" '
                    '<info@softwareheritage.org>')
NOTIF_EMAIL_SUBJECT_SUCCESS = ("Bundle ready: {obj_type} {short_id}")
NOTIF_EMAIL_SUBJECT_FAILURE = ("Bundle failed: {obj_type} {short_id}")

NOTIF_EMAIL_BODY_SUCCESS = """
You have requested the following bundle from the Software Heritage
Vault:

Object Type: {obj_type}
Object ID: {hex_id}

This bundle is now available for download at the following address:

{url}

Please keep in mind that this link might expire at some point, in which
case you will need to request the bundle again.

--\x20
The Software Heritage Developers
"""

NOTIF_EMAIL_BODY_FAILURE = """
You have requested the following bundle from the Software Heritage
Vault:

Object Type: {obj_type}
Object ID: {hex_id}

This bundle could not be cooked for the following reason:

{progress_msg}

We apologize for the inconvenience.

--\x20
The Software Heritage Developers
"""


class NotFoundExc(Exception):
    """Bundle was not found."""
    pass


def batch_to_bytes(batch):
    return [(obj_type, hashutil.hash_to_bytes(obj_id))
            for obj_type, obj_id in batch]


# TODO: Imported from swh.scheduler.backend. Factorization needed.
def autocommit(fn):
    @wraps(fn)
    def wrapped(self, *args, **kwargs):
        autocommit = False
        # TODO: I don't like using None, it's confusing for the user. how about
        # a NEW_CURSOR object()?
        if 'cursor' not in kwargs or not kwargs['cursor']:
            autocommit = True
            kwargs['cursor'] = self.cursor()

        try:
            ret = fn(self, *args, **kwargs)
        except BaseException:
            if autocommit:
                self.rollback()
            raise

        if autocommit:
            self.commit()

        return ret

    return wrapped


# TODO: This has to be factorized with other database base classes and helpers
# (swh.scheduler.backend.SchedulerBackend, swh.storage.db.BaseDb, ...)
# The three first methods are imported from swh.scheduler.backend.
class VaultBackend:
    """
    Backend for the Software Heritage vault.
    """
    def __init__(self, config):
        self.config = config
        self.cache = VaultCache(self.config['cache'])
        self.db = None
        self.reconnect()
        self.smtp_server = smtplib.SMTP()
        if self.config['scheduling_db'] is not None:
            self.scheduler = SchedulerBackend(
                scheduling_db=self.config['scheduling_db'])

    def reconnect(self):
        """Reconnect to the database."""
        if not self.db or self.db.closed:
            self.db = psycopg2.connect(
                dsn=self.config['db'],
                cursor_factory=RealDictCursor,
            )

    def close(self):
        """Close the underlying database connection."""
        self.db.close()

    def cursor(self):
        """Return a fresh cursor on the database, with auto-reconnection in
        case of failure"""
        cur = None

        # Get a fresh cursor and reconnect at most three times
        tries = 0
        while True:
            tries += 1
            try:
                cur = self.db.cursor()
                cur.execute('select 1')
                break
            except psycopg2.OperationalError:
                if tries < 3:
                    self.reconnect()
                else:
                    raise
        return cur

    def commit(self):
        """Commit a transaction"""
        self.db.commit()

    def rollback(self):
        """Rollback a transaction"""
        self.db.rollback()

    @autocommit
    def task_info(self, obj_type, obj_id, cursor=None):
        """Fetch information from a bundle"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        cursor.execute('''
            SELECT id, type, object_id, task_id, task_status, sticky,
                   ts_created, ts_done, ts_last_access, progress_msg
            FROM vault_bundle
            WHERE type = %s AND object_id = %s''', (obj_type, obj_id))
        res = cursor.fetchone()
        if res:
            res['object_id'] = bytes(res['object_id'])
        return res

    def _send_task(self, args):
        """Send a cooking task to the celery scheduler"""
        task = create_oneshot_task_dict('swh-vault-cooking', *args)
        added_tasks = self.scheduler.create_tasks([task])
        return added_tasks[0]['id']

    @autocommit
    def create_task(self, obj_type, obj_id, sticky=False, cursor=None):
        """Create and send a cooking task"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        hex_id = hashutil.hash_to_hex(obj_id)
        args = [obj_type, hex_id]

        backend_storage_config = {'storage': self.config['storage']}
        cooker_class = get_cooker(obj_type)
        cooker = cooker_class(*args, override_cfg=backend_storage_config)
        if not cooker.check_exists():
            raise NotFoundExc("Object {} was not found.".format(hex_id))

        cursor.execute('''
            INSERT INTO vault_bundle (type, object_id, sticky)
            VALUES (%s, %s, %s)''', (obj_type, obj_id, sticky))
        self.commit()

        task_id = self._send_task(args)

        cursor.execute('''
            UPDATE vault_bundle
            SET task_id = %s
            WHERE type = %s AND object_id = %s''', (task_id, obj_type, obj_id))

    @autocommit
    def add_notif_email(self, obj_type, obj_id, email, cursor=None):
        """Add an e-mail address to notify when a given bundle is ready"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        cursor.execute('''
            INSERT INTO vault_notif_email (email, bundle_id)
            VALUES (%s, (SELECT id FROM vault_bundle
                         WHERE type = %s AND object_id = %s))''',
                       (email, obj_type, obj_id))

    @autocommit
    def cook_request(self, obj_type, obj_id, *, sticky=False,
                     email=None, cursor=None):
        """Main entry point for cooking requests. This starts a cooking task if
            needed, and add the given e-mail to the notify list"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        info = self.task_info(obj_type, obj_id)

        # If there's a failed bundle entry, delete it first.
        if info is not None and info['task_status'] == 'failed':
            cursor.execute('''DELETE FROM vault_bundle
                              WHERE type = %s AND object_id = %s''',
                           (obj_type, obj_id))
            self.commit()
            info = None

        # If there's no bundle entry, create the task.
        if info is None:
            self.create_task(obj_type, obj_id, sticky)

        if email is not None:
            # If the task is already done, send the email directly
            if info is not None and info['task_status'] == 'done':
                self.send_notification(None, email, obj_type, obj_id,
                                       info['task_status'])
            # Else, add it to the notification queue
            else:
                self.add_notif_email(obj_type, obj_id, email)

        info = self.task_info(obj_type, obj_id)
        return info

    @autocommit
    def batch_cook(self, batch, cursor=None):
        """Cook a batch of bundles and returns the cooking id."""
        # Import execute_values at runtime only, because it requires
        # psycopg2 >= 2.7 (only available on postgresql servers)
        from psycopg2.extras import execute_values

        cursor.execute('''
            INSERT INTO vault_batch (id)
            VALUES (DEFAULT)
            RETURNING id''')
        batch_id = cursor.fetchone()['id']
        batch = batch_to_bytes(batch)

        # Delete all failed bundles from the batch
        cursor.execute('''
            DELETE FROM vault_bundle
            WHERE task_status = 'failed'
              AND (type, object_id) IN %s''', (tuple(batch),))

        # Insert all the bundles, return the new ones
        execute_values(cursor, '''
            INSERT INTO vault_bundle (type, object_id)
            VALUES %s ON CONFLICT DO NOTHING
            RETURNING type, object_id''', batch)
        batch_new = [(bundle['type'], bytes(bundle['object_id']))
                     for bundle in cursor.fetchall()]

        # Get the bundle ids
        cursor.execute('''
            SELECT id FROM vault_bundle
            WHERE (type, object_id) IN %s''', (tuple(batch),))
        bundle_ids = cursor.fetchall()

        # Insert the batch-bundle entries
        batch_id_bundle_ids = [(batch_id, row['id']) for row in bundle_ids]
        execute_values(cursor, '''
            INSERT INTO vault_batch_bundle (batch_id, bundle_id)
            VALUES %s ON CONFLICT DO NOTHING''',
                       batch_id_bundle_ids)
        self.commit()

        # Send the tasks
        args_batch = [(obj_type, hashutil.hash_to_hex(obj_id))
                      for obj_type, obj_id in batch_new]
        # TODO: change once the scheduler handles priority tasks
        tasks = [create_oneshot_task_dict('swh-vault-batch-cooking', *args)
                 for args in args_batch]

        added_tasks = self.scheduler.create_tasks(tasks)
        tasks_ids_bundle_ids = zip([task['id'] for task in added_tasks],
                                   batch_new)
        tasks_ids_bundle_ids = [(task_id, obj_type, obj_id)
                                for task_id, (obj_type, obj_id)
                                in tasks_ids_bundle_ids]

        # Update the task ids
        execute_values(cursor, '''
            UPDATE vault_bundle
            SET task_id = s_task_id
            FROM (VALUES %s) AS sub (s_task_id, s_type, s_object_id)
            WHERE type = s_type::cook_type AND object_id = s_object_id ''',
                       tasks_ids_bundle_ids)
        return batch_id

    @autocommit
    def batch_info(self, batch_id, cursor=None):
        """Fetch information from a batch of bundles"""
        cursor.execute('''
            SELECT vault_bundle.id as id,
                   type, object_id, task_id, task_status, sticky,
                   ts_created, ts_done, ts_last_access, progress_msg
            FROM vault_batch_bundle
            LEFT JOIN vault_bundle ON vault_bundle.id = bundle_id
            WHERE batch_id = %s''', (batch_id,))
        res = cursor.fetchall()
        if res:
            for d in res:
                d['object_id'] = bytes(d['object_id'])
        return res

    @autocommit
    def is_available(self, obj_type, obj_id, cursor=None):
        """Check whether a bundle is available for retrieval"""
        info = self.task_info(obj_type, obj_id, cursor=cursor)
        return (info is not None
                and info['task_status'] == 'done'
                and self.cache.is_cached(obj_type, obj_id))

    @autocommit
    def fetch(self, obj_type, obj_id, cursor=None):
        """Retrieve a bundle from the cache"""
        if not self.is_available(obj_type, obj_id, cursor=cursor):
            return None
        self.update_access_ts(obj_type, obj_id, cursor=cursor)
        return self.cache.get(obj_type, obj_id)

    @autocommit
    def update_access_ts(self, obj_type, obj_id, cursor=None):
        """Update the last access timestamp of a bundle"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        cursor.execute('''
            UPDATE vault_bundle
            SET ts_last_access = NOW()
            WHERE type = %s AND object_id = %s''',
                       (obj_type, obj_id))

    @autocommit
    def set_status(self, obj_type, obj_id, status, cursor=None):
        """Set the cooking status of a bundle"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        req = ('''
               UPDATE vault_bundle
               SET task_status = %s '''
               + (''', ts_done = NOW() ''' if status == 'done' else '')
               + '''WHERE type = %s AND object_id = %s''')
        cursor.execute(req, (status, obj_type, obj_id))

    @autocommit
    def set_progress(self, obj_type, obj_id, progress, cursor=None):
        """Set the cooking progress of a bundle"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        cursor.execute('''
            UPDATE vault_bundle
            SET progress_msg = %s
            WHERE type = %s AND object_id = %s''',
                       (progress, obj_type, obj_id))

    @autocommit
    def send_all_notifications(self, obj_type, obj_id, cursor=None):
        """Send all the e-mails in the notification list of a bundle"""
        obj_id = hashutil.hash_to_bytes(obj_id)
        cursor.execute('''
            SELECT vault_notif_email.id AS id, email, task_status, progress_msg
            FROM vault_notif_email
            INNER JOIN vault_bundle ON bundle_id = vault_bundle.id
            WHERE vault_bundle.type = %s AND vault_bundle.object_id = %s''',
                       (obj_type, obj_id))
        for d in cursor:
            self.send_notification(d['id'], d['email'], obj_type, obj_id,
                                   status=d['task_status'],
                                   progress_msg=d['progress_msg'])

    @autocommit
    def send_notification(self, n_id, email, obj_type, obj_id, status,
                          progress_msg=None, cursor=None):
        """Send the notification of a bundle to a specific e-mail"""
        hex_id = hashutil.hash_to_hex(obj_id)
        short_id = hex_id[:7]

        # TODO: instead of hardcoding this, we should probably:
        # * add a "fetch_url" field in the vault_notif_email table
        # * generate the url with flask.url_for() on the web-ui side
        # * send this url as part of the cook request and store it in
        #   the table
        # * use this url for the notification e-mail
        url = ('https://archive.softwareheritage.org/api/1/vault/{}/{}/'
               'raw'.format(obj_type, hex_id))

        if status == 'done':
            text = NOTIF_EMAIL_BODY_SUCCESS.strip()
            text = text.format(obj_type=obj_type, hex_id=hex_id, url=url)
            msg = MIMEText(text)
            msg['Subject'] = (NOTIF_EMAIL_SUBJECT_SUCCESS
                              .format(obj_type=obj_type, short_id=short_id))
        elif status == 'failed':
            text = NOTIF_EMAIL_BODY_FAILURE.strip()
            text = text.format(obj_type=obj_type, hex_id=hex_id,
                               progress_msg=progress_msg)
            msg = MIMEText(text)
            msg['Subject'] = (NOTIF_EMAIL_SUBJECT_FAILURE
                              .format(obj_type=obj_type, short_id=short_id))
        else:
            raise RuntimeError("send_notification called on a '{}' bundle"
                               .format(status))

        msg['From'] = NOTIF_EMAIL_FROM
        msg['To'] = email

        self._smtp_send(msg)

        if n_id is not None:
            cursor.execute('''
                DELETE FROM vault_notif_email
                WHERE id = %s''', (n_id,))

    def _smtp_send(self, msg):
        # Reconnect if needed
        try:
            status = self.smtp_server.noop()[0]
        except smtplib.SMTPException:
            status = -1
        if status != 250:
            self.smtp_server.connect('localhost', 25)

        # Send the message
        self.smtp_server.send_message(msg)

    @autocommit
    def _cache_expire(self, cond, *args, cursor=None):
        """Low-level expiration method, used by cache_expire_* methods"""
        # Embedded SELECT query to be able to use ORDER BY and LIMIT
        cursor.execute('''
            DELETE FROM vault_bundle
            WHERE ctid IN (
                SELECT ctid
                FROM vault_bundle
                WHERE sticky = false
                {}
            )
            RETURNING type, object_id
            '''.format(cond), args)

        for d in cursor:
            self.cache.delete(d['type'], bytes(d['object_id']))

    @autocommit
    def cache_expire_oldest(self, n=1, by='last_access', cursor=None):
        """Expire the `n` oldest bundles"""
        assert by in ('created', 'done', 'last_access')
        filter = '''ORDER BY ts_{} LIMIT {}'''.format(by, n)
        return self._cache_expire(filter)

    @autocommit
    def cache_expire_until(self, date, by='last_access', cursor=None):
        """Expire all the bundles until a certain date"""
        assert by in ('created', 'done', 'last_access')
        filter = '''AND ts_{} <= %s'''.format(by)
        return self._cache_expire(filter, date)