# -*- coding: utf-8 -*-
# _blobs.py
# Copyright (C) 2017 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Clientside BlobBackend Storage.
"""

from copy import copy
from urlparse import urljoin

import os.path
import uuid

from io import BytesIO
from functools import partial


from twisted.logger import Logger
from twisted.enterprise import adbapi
from twisted.internet import defer
from twisted.web.client import FileBodyProducer

import treq

from leap.soledad.client.sqlcipher import SQLCipherOptions
from leap.soledad.client import pragmas

from _crypto import DocInfo, BlobEncryptor, BlobDecryptor


logger = Logger()


class ConnectionPool(adbapi.ConnectionPool):

    def insertAndGetLastRowid(self, *args, **kwargs):
        """
        Execute an SQL query and return the last rowid.

        See: https://sqlite.org/c3ref/last_insert_rowid.html
        """
        return self.runInteraction(
            self._insertAndGetLastRowid, *args, **kwargs)

    def _insertAndGetLastRowid(self, trans, *args, **kw):
        trans.execute(*args, **kw)
        return trans.lastrowid

    def blob(self, table, column, irow, flags):
        """
        Open a BLOB for incremental I/O.

        Return a handle to the BLOB that would be selected by:

          SELECT column FROM table WHERE rowid = irow;

        See: https://sqlite.org/c3ref/blob_open.html

        :param table: The table in which to lookup the blob.
        :type table: str
        :param column: The column where the BLOB is located.
        :type column: str
        :param rowid: The rowid of the BLOB.
        :type rowid: int
        :param flags: If zero, BLOB is opened for read-only. If non-zero,
                      BLOB is opened for RW.
        :type flags: int

        :return: A BLOB handle.
        :rtype: pysqlcipher.dbapi.Blob
        """
        return self.runInteraction(self._blob, table, column, irow, flags)

    def _blob(self, trans, table, column, irow, flags):
        # TODO: should not use transaction private variable here
        handle = trans._connection.blob(table, column, irow, flags)
        return handle


class DecrypterBuffer(object):

    def __init__(self, doc_id, rev, secret):
        self.decrypter = None
        self.buffer = BytesIO()
        self.doc_info = DocInfo(doc_id, rev)
        self.secret = secret
        self.d = None

    def write(self, data):
        if not self.decrypter:
            self.buffer.write(data)
            self.decrypter = BlobDecryptor(
                self.doc_info, self.buffer,
                secret=self.secret,
                armor=True,
                start_stream=False)
            self.d = self.decrypter.decrypt()
        else:
            self.decrypter.write(data)

    def close(self):
        if self.d:
            self.d.addCallback(lambda result: (result, self.decrypter.size))
        return self.d


class BlobManager(object):
    """
    Ideally, the decrypting flow goes like this:

    - GET a blob from remote server.
    - Decrypt the preamble
    - Allocate a zeroblob in the sqlcipher sink
    - Mark the blob as unusable (ie, not verified)
    - Decrypt the payload incrementally, and write chunks to sqlcipher
      ** Is it possible to use a small buffer for the aes writer w/o
      ** allocating all the memory in openssl?
    - Finalize the AES decryption
    - If preamble + payload verifies correctly, mark the blob as usable

    """

    def __init__(self, local_path, remote, key, secret, user):
        self.local = SQLiteBlobBackend(local_path, key)
        self.remote = remote
        self.secret = secret
        self.user = user

    @defer.inlineCallbacks
    def put(self, doc):
        fd = doc.blob_fd
        # TODO this is a tee really, but ok... could do db and upload
        # concurrently. not sure if we'd gain something.
        yield self.local.put(doc.blob_id, fd)
        fd.seek(0)
        yield self._encrypt_and_upload(doc.blob_id, doc.doc_id, doc.rev, fd)

    @defer.inlineCallbacks
    def get(self, blob_id, doc_id, rev):
        local_blob = yield self.local.get(blob_id)
        if local_blob:
            logger.info("Found blob in local database: %s" % blob_id)
            defer.returnValue(local_blob)

        result = yield self._download_and_decrypt(blob_id, doc_id, rev)

        if not result:
            defer.returnValue(None)
        blob, size = result

        if blob:
            logger.info("Got decrypted blob of type: %s" % type(blob))
            blob.seek(0)
            yield self.local.put(blob_id, blob, size=size)
            blob.seek(0)
            defer.returnValue(blob)
        else:
            # XXX we shouldn't get here, but we will...
            # lots of ugly error handling possible:
            # 1. retry, might be network error
            # 2. try later, maybe didn't finished streaming
            # 3.. resignation, might be error while verifying
            logger.error('sorry, dunno what happened')

    @defer.inlineCallbacks
    def _encrypt_and_upload(self, blob_id, doc_id, rev, fd):
        # TODO ------------------------------------------
        # this is wrong, is doing 2 stages.
        # the crypto producer can be passed to
        # the uploader and react as data is written.
        # try to rewrite as a tube: pass the fd to aes and let aes writer
        # produce data to the treq request fd.
        # ------------------------------------------------
        logger.info("Staring upload of blob: %s" % blob_id)
        doc_info = DocInfo(doc_id, rev)
        uri = urljoin(self.remote, self.user + "/" + blob_id)
        crypter = BlobEncryptor(doc_info, fd, secret=self.secret,
                                armor=True)
        fd = yield crypter.encrypt()
        yield treq.put(uri, data=fd)
        logger.info("Finished upload: %s" % (blob_id,))

    @defer.inlineCallbacks
    def _download_and_decrypt(self, blob_id, doc_id, rev):
        logger.info("Staring download of blob: %s" % blob_id)
        # TODO this needs to be connected in a tube
        uri = self.remote + self.user + '/' + blob_id
        data = yield treq.get(uri)

        if data.code == 404:
            logger.warn("Blob not found in server: %s" % blob_id)
            defer.returnValue(None)
        elif not data.headers.hasHeader('Tag'):
            logger.error("Server didn't send a tag header for: %s" % blob_id)
            defer.returnValue(None)
        tag = data.headers.getRawHeaders('Tag')[0]
        tag = base64.urlsafe_b64decode(tag)
        buf = DecrypterBuffer(doc_id, rev, self.secret, tag)

        # incrementally collect the body of the response
        yield treq.collect(data, buf.write)
        fd, size = yield buf.close()
        logger.info("Finished download: (%s, %d)" % (blob_id, size))
        defer.returnValue((fd, size))


class SQLiteBlobBackend(object):

    def __init__(self, path, key=None):
        self.path = os.path.abspath(
            os.path.join(path, 'soledad_blob.db'))
        if not key:
            raise ValueError('key cannot be None')
        backend = 'pysqlcipher.dbapi2'
        opts = SQLCipherOptions('/tmp/ignored', key)
        pragmafun = partial(pragmas.set_init_pragmas, opts=opts)
        openfun = _sqlcipherInitFactory(pragmafun)

        self.dbpool = ConnectionPool(
            backend, self.path, check_same_thread=False, timeout=5,
            cp_openfun=openfun, cp_min=1, cp_max=2, cp_name='blob_pool')

    @defer.inlineCallbacks
    def put(self, blob_id, blob_fd, size=None):
        logger.info("Saving blob in local database...")
        insert = 'INSERT INTO blobs (blob_id, payload) VALUES (?, zeroblob(?))'
        irow = yield self.dbpool.insertAndGetLastRowid(insert, (blob_id, size))
        handle = yield self.dbpool.blob('blobs', 'payload', irow, 1)
        blob_fd.seek(0)
        # XXX I have to copy the buffer here so that I'm able to
        # return a non-closed file to the caller (blobmanager.get)
        # FIXME should remove this duplication!
        # have a look at how treq does cope with closing the handle
        # for uploading a file
        producer = FileBodyProducer(copy(blob_fd))
        done = yield producer.startProducing(handle)
        logger.info("Finished saving blob in local database.")
        defer.returnValue(done)

    @defer.inlineCallbacks
    def get(self, blob_id):
        # TODO we can also stream the blob value using sqlite
        # incremental interface for blobs - and just return the raw fd instead
        select = 'SELECT payload FROM blobs WHERE blob_id = ?'
        result = yield self.dbpool.runQuery(select, (blob_id,))
        if result:
            defer.returnValue(BytesIO(str(result[0][0])))


def _init_blob_table(conn):
    maybe_create = (
        "CREATE TABLE IF NOT EXISTS "
        "blobs ("
        "blob_id PRIMARY KEY, "
        "payload BLOB)")
    conn.execute(maybe_create)


def _sqlcipherInitFactory(fun):
    def _initialize(conn):
        fun(conn)
        _init_blob_table(conn)
    return _initialize


class BlobDoc(object):

    # TODO probably not needed, but convenient for testing for now.

    def __init__(self, doc_id, rev, content, blob_id=None):

        self.doc_id = doc_id
        self.rev = rev
        self.is_blob = True
        self.blob_fd = content
        if blob_id is None:
            blob_id = uuid.uuid4().get_hex()
        self.blob_id = blob_id


#
# testing facilities
#

@defer.inlineCallbacks
def testit(reactor):
    # configure logging to stdout
    from twisted.python import log
    import sys
    log.startLogging(sys.stdout)

    # parse command line arguments
    import argparse

    usage = "\n  mkdir /tmp/blobs/user && cd server/src/leap/soledad/server/" \
            " && python _blobs.py" \
            "\n  python _blobs.py upload /path/to/file blob_id" \
            "\n  python _blobs.py download blob_id"

    parser = argparse.ArgumentParser(usage=usage)
    subparsers = parser.add_subparsers(help='sub-command help', dest='action')

    # parse upload command
    parser_upload = subparsers.add_parser(
        'upload', help='upload blob and bypass local db')
    parser_upload.add_argument('payload')
    parser_upload.add_argument('blob_id')

    # parse download command
    parser_download = subparsers.add_parser(
        'download', help='download blob and bypass local db')
    parser_download.add_argument('blob_id')

    # parse put command
    parser_put = subparsers.add_parser(
        'put', help='put blob in local db and upload')
    parser_put.add_argument('payload')
    parser_put.add_argument('blob_id')

    # parse get command
    parser_get = subparsers.add_parser(
        'get', help='get blob from local db, get if needed')
    parser_get.add_argument('blob_id')

    # parse arguments
    args = parser.parse_args()

    # TODO convert these into proper unittests

    def _manager():
        manager = BlobManager(
            '/tmp/blobs', 'http://localhost:9000/',
            'A' * 32, 'secret', 'user')
        return manager

    @defer.inlineCallbacks
    def _upload(blob_id, payload):
        logger.info(":: Starting upload only: %s" % str((blob_id, payload)))
        manager = _manager()
        with open(payload, 'r') as fd:
            yield manager._encrypt_and_upload(blob_id, 'mydoc', '1', fd)
        logger.info(":: Finished upload only: %s" % str((blob_id, payload)))

    @defer.inlineCallbacks
    def _download(blob_id):
        logger.info(":: Starting download only: %s" % blob_id)
        manager = _manager()
        result = yield manager._download_and_decrypt(blob_id, 'mydoc', '1')
        logger.info(":: Result of download: %s" % str(result))
        if result:
            fd, _ = result
            logger.info(":: Content of blob %s: %s" % (blob_id, fd.getvalue()))
        logger.info(":: Finished download only: %s" % blob_id)

    @defer.inlineCallbacks
    def _put(blob_id, payload):
        logger.info(":: Starting full put: %s" % blob_id)
        manager = _manager()
        with open(payload) as fd:
            doc = BlobDoc('mydoc', '1', fd, blob_id=blob_id)
            result = yield manager.put(doc)
        logger.info(":: Result of put: %s" % str(result))
        logger.info(":: Finished full put: %s" % blob_id)

    @defer.inlineCallbacks
    def _get(blob_id):
        logger.info(":: Starting full get: %s" % blob_id)
        manager = _manager()
        fd = yield manager.get(blob_id, 'mydoc', '1')
        if fd:
            logger.info(":: Result of get: " + fd.getvalue())
        logger.info(":: Finished full get: %s" % blob_id)

    if args.action == 'upload':
        yield _upload(args.blob_id, args.payload)
    elif args.action == 'download':
        yield _download(args.blob_id)
    elif args.action == 'put':
        yield _put(args.blob_id, args.payload)
    elif args.action == 'get':
        yield _get(args.blob_id)


if __name__ == '__main__':
    from twisted.internet.task import react
    react(testit)