1 files changed, 171 insertions, 0 deletions
diff --git a/src/db.py b/src/db.py
new file mode 100755
index 0000000..4702def
--- /dev/null
+++ b/src/db.py
@@ -0,0 +1,171 @@
+#! /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)