#! /usr/bin/env python3

# A database storing dictionaries, keyed on a timestamp.

# key = 8 octets timestamp | 1 octet version
#       struct.pack('!dB', time.time(), 0)

# value = A dict which will be stored as a JSON object encoded in
# UTF-8. Note that dict keys of type integer or float will become
# strings while values will keep their type.

# Note that there's a (slim) chance that you'd stomp on the previous
# value if you're too quick with generating the timestamps, ie
# invoking time.time() several times quickly enough.

from store import KVStore
import json
from pathlib import PurePath
import time
import struct
import os

class DictDB(KVStore):
    VERSION = 0

    # TODO: implement indexes
    # TODO: implement search(dict key) for indexed fields

    def __init__(self, name, basedir='.'):
        super().__init__(name, basedir)
        self._ts = time.time()
        self._index = {}

    def unique_key(self):
        ts = time.time()
        while ts == self._ts:
            ts = time.time()
        self._ts = ts
        return struct.pack('!dB', ts, DictDB.VERSION)

    def index_add(self, path):
        name = PurePath(path).name
        self._index[name] = DBIndex(path)

    def add(self, data, batch_write=False):
        if type(data) is list:
            ret = []
            if batch_write:     # Supposedly makes the update atomic.
                batch = self.batch()
            for e in data:
                ret += [self.add(e)]
            if batch_write:
                self.write(batch)
            return ret
        else:
            key = self.unique_key()
            json_data = json.dumps(data).encode('UTF-8')
            self.put(key, json_data)
            return key

    def get(self, key):
        enc = super().get(key)  # name collision, specify super class
        ret = json.loads(enc.decode('UTF-8'))
        return ret

    def slice(self, key_from=None, key_to=None):
        ret = []
        for key_raw, val_raw in list(self.range_iter(key_from=key_from, key_to=key_to)):
            (key, ver) = struct.unpack('!dB', key_raw)
            if ver == DictDB.VERSION:
                val = json.loads(val_raw.decode('UTF-8'))
                ret.append((key, val))
        return ret

    # Search top level dict for objects with a name matching DICT_NAME
    # and optionally value DICT_VAL.
    def search(self, dict_name, dict_val=None):
        res = []
        for key, obj in self.slice():
            if dict_name in obj:
                if dict_val is None:
                    res.append((key, obj))
                elif dict_val == obj[dict_name]:
                    res.append((key, obj))
        return res

    def timestamp_from_key(key):
        ts, _ = struct.unpack('!dB', key)
        return ts

class DBIndex(KVStore):
    def __init__(self, name, basedir='.'):
        super().__init__(name, basedir)

#     def update_or_create(self, key, val):
#         curval = []
#         try:
#             curval = self._db.Get(key)
#         except KeyError:
#             self._db.Put(key, [val])
#             return

#         if curval is list:
#             self._db.Put(key, curval + [val])
#         else:
#             self._db.Put(key, json.dumps([curval, val]))

    # def index_full(self, name):
    #     kv = self._index[name])
    #     for key, val in self.range_iter():
    #         valdict = json.loads(val)
    #         field = valdict.get(name)
    #         if field:
    #             ix = kv.get(key)
    #             if ix:
    #                 kv.put(ix + [key])
    #             else:
    #                 kv.put([key])

if __name__ == '__main__':
    DBDIR = 'test_db.db'
    # TODO: rm -r DBDIR
    db = DictDB('db', basedir = DBDIR)
    #ix = DBIndex('foo', basedir = DBDIR)

    key = db.add({'foo': 'Bar'})
    assert(db.get(key) == {'foo': 'Bar'})

    key = db.add({0: 'Foo'})    # NOTE: int keys become strings
    assert(db.get(key) == {'0': 'Foo'})

    d = {'4711': 'Large number', '7': 'Small number', '0': 'Bar'}
    key = db.add(d)
    res = db.get(key)
    assert(dict_eq(d, res))

    key = db.add({'an int': 0})
    assert(db.get(key) == {'an int': 0})

    key = db.add({'a float': 1.1})
    assert(db.get(key) == {'a float': 1.1})

    # TODO: verify slice() too
    for key, val in db.slice():
        print(key, val)

    res = db.search('an int')
    assert(dict_eq(res[0][1], {'an int': 0}))

    res = db.search('0')
    assert(dict_eq(res[0][1], {'0': 'Foo'}))
    assert(dict_eq(res[1][1], d))

    res = db.search('7', dict_val = 'Small number') # FIXME: verify better -- do we hit only '7' here, f.ex.?
    assert('7' in res[0][1])

    res = db.search('7', dict_val = 'not matching')
    assert(not res)

    N = 10 * 1000               # 10k takes ~0.2s.
    data = [{str(x): x} for x in range(N)]
    keys = db.add(data, batch_write = False)
    assert(len(keys) == N)
    for k in range(len(keys)):
        assert(db.get(keys[k]) == data[k])


from operator import itemgetter
def dict_eq(a, b):
    sort_on_key = lambda d: sorted(d.items(), key=itemgetter(0))
    return sort_on_key(a) == sort_on_key(b)