add serialization, custom field types

src/grung/db.py

@@ -21,18 +21,25 @@ class RecordTable(table.Table):
         super().__init__(db.storage, name, **kwargs)
 
     def insert(self, document):
-        self._satisfy_constraints(document)
+        doc = document.serialize(self._db)
-        if document.doc_id:
+        self._check_constraints(doc)
-            last_insert_id = super().upsert(document)[0]
+
+        if doc.doc_id:
+            last_insert_id = super().upsert(doc)[0]
         else:
-            last_insert_id = super().insert(dict(document))
+            last_insert_id = super().insert(dict(doc))
         return self.get(doc_id=last_insert_id)
 
+    def get(self, doc_id: int):
+        document = super().get(doc_id=doc_id)
+        if document:
+            return document.deserialize(self._db)
+
     def remove(self, document):
         if document.doc_id:
             super().remove(doc_ids=[document.doc_id])
 
-    def _satisfy_constraints(self, document) -> bool:
+    def _check_constraints(self, document) -> bool:
         self._check_unique(document)
 
     def _check_unique(self, document) -> bool:

src/grung/examples.py

@@ -1,11 +1,9 @@
-from typing import List
+from grung.types import Collection, Field, Integer, Record
-
-from grung.types import Field, Record
 
 
 class User(Record):
-    _fields = [Field("name"), Field("email", unique=True)]
+    _fields = [Field("name"), Integer("number", default=0), Field("email", unique=True)]
 
 
 class Group(Record):
-    _fields = [Field("name", unique=True), Field("users", List[User])]
+    _fields = [Field("name", unique=True), Collection("users", User)]

src/grung/exceptions.py

@@ -10,3 +10,17 @@ class UniqueConstraintError(Exception):
             f"  * Error:   Unique constraint failure\n"
             "   * The record matches the following existing records:\n\n" + "\n".join(str(c) for c in collisions)
         )
+
+
+class PointerReferenceError(Exception):
+    """
+    Thrown when a document field containing a document could not be resolve to an existing record in the database.
+    """
+
+    def __init__(self, reference):
+        super().__init__(
+            "\n"
+            f"  * Reference: {reference}\n"
+            f"  * Error:     Invalid Pointer\n"
+            "   * This collection member does not refer an existing record. Do you need to save it first?"
+        )

src/grung/types.py

@@ -1,7 +1,13 @@
+from __future__ import annotations
+
 from collections import namedtuple
 from dataclasses import dataclass
+from typing import Dict, List
 
 import nanoid
+from tinydb import where
+
+from grung.exceptions import PointerReferenceError
 
 Metadata = namedtuple("Metadata", ["table", "fields"])
 
@@ -12,13 +18,29 @@ class Field:
     Represents a single field in a Record.
     """
 
+    value_type = str
+
     name: str
-    value_type: type = str
     default: value_type | None = None
     unique: bool = False
 
+    def serialize(self, rec: value_type, db: TinyDB) -> str:
+        return str(rec)
 
-class Record(dict):
+    def deserialize(self, rec: str, db: TinyDB) -> value_type:
+        return rec
+
+
+class Integer(Field):
+    value_type = int
+
+    default: value_type = 0
+
+    def deserialize(self, rec: str, db: TinyDB) -> value_type:
+        return int(rec)
+
+
+class Record(Dict[(str, Field)]):
     """
     Base type for a single database record.
     """
@@ -33,6 +55,24 @@ class Record(dict):
         self.doc_id = doc_id
         super().__init__(dict({field.name: field.default for field in self._fields}, **raw_doc, **params))
 
+    def serialize(self, db):
+        """
+        Serialie every field on the record
+        """
+        rec = {}
+        for name, field in self._metadata.fields.items():
+            rec[name] = field.serialize(self[name], db)
+        return self.__class__(rec, doc_id=self.doc_id)
+
+    def deserialize(self, db):
+        """
+        Deserialize every field on the record
+        """
+        rec = {}
+        for name, field in self._metadata.fields.items():
+            rec[name] = field.deserialize(self[name], db)
+        return self.__class__(rec, doc_id=self.doc_id)
+
     def __setattr__(self, key, value):
         if key in self:
             self[key] = value
@@ -45,3 +85,29 @@ class Record(dict):
 
     def __repr__(self):
         return f"{self.__class__.__name__}[{self.doc_id}]: {self.items()}"
+
+
+class Collection(Field):
+    """
+    A collection of fields that store pointers instead of dicts.
+    """
+
+    value_type = List[Record]
+
+    def serialize(self, recs: value_type, db: TinyDB) -> List[str]:
+        vals = []
+        for rec in recs:
+            if not rec.doc_id:
+                raise PointerReferenceError(rec)
+            vals.append(f"{rec._metadata.table}::{rec.uid}")
+        return vals
+
+    def deserialize(self, rec: List[str], db: TinyDB) -> Collection.value_type:
+        """
+        Recursively deserialize the objects in this collection
+        """
+        vals = []
+        for member in rec:
+            pt, puid = member.split("::")
+            vals.append(db.table(pt).search(where("uid") == puid)[0].deserialize(db))
+        return vals

test/test_db.py

@@ -3,7 +3,7 @@ from tinydb.storages import MemoryStorage
 
 from grung import examples
 from grung.db import GrungDB
-from grung.exceptions import UniqueConstraintError
+from grung.exceptions import PointerReferenceError, UniqueConstraintError
 
 
 @pytest.fixture
@@ -14,7 +14,7 @@ def db():
 
 
 def test_crud(db):
-    user = examples.User(name="john", email="john@foo")
+    user = examples.User(name="john", number=23, email="john@foo")
     assert user.uid
     assert user._metadata.fields["uid"].unique
 
@@ -25,6 +25,7 @@ def test_crud(db):
     # read back
     assert db.User.get(doc_id=last_insert_id) == john_something
     assert john_something.name == user.name
+    assert john_something.number == 23
     assert john_something.email == user.email
     assert john_something.uid == user.uid
 
@@ -35,21 +36,23 @@ def test_crud(db):
     assert after_update == john_something
     assert before_update != after_update
 
-    # pointers
-    players = examples.Group(name="players", users=[john_something])
-    players = db.save(players)
-    players.users[0]["name"] = "fnord"
-    db.save(players)
-
-    # modify records
-    players.users = []
-    db.save(players)
-    after_update = db.Group.get(doc_id=players.doc_id)
-    assert after_update.users == []
-
     # delete
-    db.delete(players)
+    db.delete(john_something)
-    assert len(db.Group) == 0
+    assert len(db.User) == 0
+
+
+def test_pointers(db):
+    user = examples.User(name="john", email="john@foo")
+    players = examples.Group(name="players", users=[user])
+
+    with pytest.raises(PointerReferenceError):
+        players = db.save(players)
+
+    user = db.save(user)
+
+    players.users[0] = user
+    players = db.save(players)
+    assert players.users[0] == user
 
 
 def test_unique(db):