"""A Task logger that presents our DB interface,
but exists entirely in memory and implemented with dicts.

Authors:

* Min RK


TaskRecords are dicts of the form:
{
    'msg_id' : str(uuid),
    'client_uuid' : str(uuid),
    'engine_uuid' : str(uuid) or None,
    'header' : dict(header),
    'content': dict(content),
    'buffers': list(buffers),
    'submitted': datetime,
    'started': datetime or None,
    'completed': datetime or None,
    'resubmitted': datetime or None,
    'result_header' : dict(header) or None,
    'result_content' : dict(content) or None,
    'result_buffers' : list(buffers) or None,
}
With this info, many of the special categories of tasks can be defined by query:

pending:  completed is None
client's outstanding: client_uuid = uuid && completed is None
MIA: arrived is None (and completed is None)
etc.

EngineRecords are dicts of the form:
{
    'eid' : int(id),
    'uuid': str(uuid)
}
This may be extended, but is currently.

We support a subset of mongodb operators:
    $lt,$gt,$lte,$gte,$ne,$in,$nin,$all,$mod,$exists
"""
#-----------------------------------------------------------------------------
#  Copyright (C) 2010-2011  The IPython Development Team
#
#  Distributed under the terms of the BSD License.  The full license is in
#  the file COPYING, distributed as part of this software.
#-----------------------------------------------------------------------------

from copy import deepcopy as copy
from datetime import datetime

from IPython.config.configurable import LoggingConfigurable

from IPython.utils.traitlets import Dict, Unicode, Instance

filters = {
 '$lt' : lambda a,b: a < b,
 '$gt' : lambda a,b: b > a,
 '$eq' : lambda a,b: a == b,
 '$ne' : lambda a,b: a != b,
 '$lte': lambda a,b: a <= b,
 '$gte': lambda a,b: a >= b,
 '$in' : lambda a,b: a in b,
 '$nin': lambda a,b: a not in b,
 '$all': lambda a,b: all([ a in bb for bb in b ]),
 '$mod': lambda a,b: a%b[0] == b[1],
 '$exists' : lambda a,b: (b and a is not None) or (a is None and not b)
}


class CompositeFilter(object):
    """Composite filter for matching multiple properties."""

    def __init__(self, dikt):
        self.tests = []
        self.values = []
        for key, value in dikt.items():
            self.tests.append(filters[key])
            self.values.append(value)

    def __call__(self, value):
        for test,check in zip(self.tests, self.values):
            if not test(value, check):
                return False
        return True

class BaseDB(LoggingConfigurable):
    """Empty Parent class so traitlets work on DB."""
    # base configurable traits:
    session = Unicode("")

class DictDB(BaseDB):
    """Basic in-memory dict-based object for saving Task Records.

    This is the first object to present the DB interface
    for logging tasks out of memory.

    The interface is based on MongoDB, so adding a MongoDB
    backend should be straightforward.
    """

    _records = Dict()

    def _match_one(self, rec, tests):
        """Check if a specific record matches tests."""
        for key,test in tests.items():
            if not test(rec.get(key, None)):
                return False
        return True

    def _match(self, check):
        """Find all the matches for a check dict."""
        matches = []
        tests = {}
        for k,v in check.items():
            if isinstance(v, dict):
                tests[k] = CompositeFilter(v)
            else:
                tests[k] = lambda o: o==v

        for rec in self._records.values():
            if self._match_one(rec, tests):
                matches.append(copy(rec))
        return matches

    def _extract_subdict(self, rec, keys):
        """extract subdict of keys"""
        d = {}
        d['msg_id'] = rec['msg_id']
        for key in keys:
            d[key] = rec[key]
        return copy(d)

    def add_record(self, msg_id, rec):
        """Add a new Task Record, by msg_id."""
        if msg_id in self._records:
            raise KeyError("Already have msg_id %r"%(msg_id))
        self._records[msg_id] = rec

    def get_record(self, msg_id):
        """Get a specific Task Record, by msg_id."""
        if not msg_id in self._records:
            raise KeyError("No such msg_id %r"%(msg_id))
        return copy(self._records[msg_id])

    def update_record(self, msg_id, rec):
        """Update the data in an existing record."""
        self._records[msg_id].update(rec)

    def drop_matching_records(self, check):
        """Remove a record from the DB."""
        matches = self._match(check)
        for m in matches:
            del self._records[m['msg_id']]

    def drop_record(self, msg_id):
        """Remove a record from the DB."""
        del self._records[msg_id]


    def find_records(self, check, keys=None):
        """Find records matching a query dict, optionally extracting subset of keys.

        Returns dict keyed by msg_id of matching records.

        Parameters
        ----------

        check: dict
            mongodb-style query argument
        keys: list of strs [optional]
            if specified, the subset of keys to extract.  msg_id will *always* be
            included.
        """
        matches = self._match(check)
        if keys:
            return [ self._extract_subdict(rec, keys) for rec in matches ]
        else:
            return matches


    def get_history(self):
        """get all msg_ids, ordered by time submitted."""
        msg_ids = list(self._records.keys())
        return sorted(msg_ids, key=lambda m: self._records[m]['submitted'])

NODATA = KeyError("NoDB backend doesn't store any data. "
"Start the Controller with a DB backend to enable resubmission / result persistence."
)

class NoDB(DictDB):
    """A blackhole db backend that actually stores no information.
    
    Provides the full DB interface, but raises KeyErrors on any
    method that tries to access the records.  This can be used to
    minimize the memory footprint of the Hub when its record-keeping
    functionality is not required.
    """
    
    def add_record(self, msg_id, record):
        pass
    
    def get_record(self, msg_id):
        raise NODATA
    
    def update_record(self, msg_id, record):
        pass
    
    def drop_matching_records(self, check):
        pass
    
    def drop_record(self, msg_id):
        pass
    
    def find_records(self, check, keys=None):
        raise NODATA
    
    def get_history(self):
        raise NODATA

