try:
    import simplejson as json
except ImportError:
    import json  # noqa

from u1db import Document
from u1db.remote.http_target import HTTPSyncTarget
from u1db.remote.http_database import HTTPDatabase
import base64


class NoDefaultKey(Exception):
    pass


class LeapDocument(Document):
    """
    LEAP Documents are standard u1db documents with cabability of returning an
    encrypted version of the document json string as well as setting document
    content based on an encrypted version of json string.
    """

    def __init__(self, doc_id=None, rev=None, json='{}', has_conflicts=False,
                 encrypted_json=None, default_key=None, gpg_wrapper=None):
        super(LeapDocument, self).__init__(doc_id, rev, json, has_conflicts)
        if gpg_wrapper:
            self._gpg = gpg_wrapper
        else:
            self._gpg = GPGWrapper()
        if encrypted_json:
            self.set_encrypted_json(encrypted_json)
        self._default_key = default_key

    def get_encrypted_json(self):
        """
        Returns document's json serialization encrypted with user's public key.
        """
        if self._default_key is None:
            raise NoDefaultKey()
        cyphertext = self._gpg.encrypt(self.get_json(),
                                       self._default_key,
                                       always_trust = True)
                                       # TODO: always trust?
        return json.dumps({'cyphertext' : str(cyphertext)})

    def set_encrypted_json(self, encrypted_json):
        """
        Set document's content based on encrypted version of json string.
        """
        cyphertext = json.loads(encrypted_json)['cyphertext']
        plaintext = str(self._gpg.decrypt(cyphertext))
        return self.set_json(plaintext)


class LeapDatabase(HTTPDatabase):
    """Implement the HTTP remote database API to a Leap server."""

    @staticmethod
    def open_database(url, create):
        db = LeapDatabase(url)
        db.open(create)
        return db

    @staticmethod
    def delete_database(url):
        db = LeapDatabase(url)
        db._delete()
        db.close()

    def get_sync_target(self):
        st = LeapSyncTarget(self._url.geturl())
        st._creds = self._creds
        return st


class LeapSyncTarget(HTTPSyncTarget):

    def _parse_sync_stream(self, data, return_doc_cb, ensure_callback=None):
        """
        Does the same as parent's method but ensures incoming content will be
        decrypted.
        """
        parts = data.splitlines()  # one at a time
        if not parts or parts[0] != '[':
            raise BrokenSyncStream
        data = parts[1:-1]
        comma = False
        if data:
            line, comma = utils.check_and_strip_comma(data[0])
            res = json.loads(line)
            if ensure_callback and 'replica_uid' in res:
                ensure_callback(res['replica_uid'])
            for entry in data[1:]:
                if not comma:  # missing in between comma
                    raise BrokenSyncStream
                line, comma = utils.check_and_strip_comma(entry)
                entry = json.loads(line)
                doc = LeapDocument(entry['id'], entry['rev'],
                                   encrypted_json=entry['content'])
                return_doc_cb(doc, entry['gen'], entry['trans_id'])
        if parts[-1] != ']':
            try:
                partdic = json.loads(parts[-1])
            except ValueError:
                pass
            else:
                if isinstance(partdic, dict):
                    self._error(partdic)
            raise BrokenSyncStream
        if not data or comma:  # no entries or bad extra comma
            raise BrokenSyncStream
        return res

    def sync_exchange(self, docs_by_generations, source_replica_uid,
                      last_known_generation, last_known_trans_id,
                      return_doc_cb, ensure_callback=None):
        """
        Does the same as parent's method but encrypts content before syncing.
        """
        self._ensure_connection()
        if self._trace_hook:  # for tests
            self._trace_hook('sync_exchange')
        url = '%s/sync-from/%s' % (self._url.path, source_replica_uid)
        self._conn.putrequest('POST', url)
        self._conn.putheader('content-type', 'application/x-u1db-sync-stream')
        for header_name, header_value in self._sign_request('POST', url, {}):
            self._conn.putheader(header_name, header_value)
        entries = ['[']
        size = 1

        def prepare(**dic):
            entry = comma + '\r\n' + json.dumps(dic)
            entries.append(entry)
            return len(entry)

        comma = ''
        size += prepare(
            last_known_generation=last_known_generation,
            last_known_trans_id=last_known_trans_id,
            ensure=ensure_callback is not None)
        comma = ','
        for doc, gen, trans_id in docs_by_generations:
            size += prepare(id=doc.doc_id, rev=doc.rev,
                            content=doc.get_encrypted_json(),
                            gen=gen, trans_id=trans_id)
        entries.append('\r\n]')
        size += len(entries[-1])
        self._conn.putheader('content-length', str(size))
        self._conn.endheaders()
        for entry in entries:
            self._conn.send(entry)
        entries = None
        data, _ = self._response()
        res = self._parse_sync_stream(data, return_doc_cb, ensure_callback)
        data = None
        return res['new_generation'], res['new_transaction_id']