add skeleton sqlalchemy models

field_types.py

+import enum
+
+class FieldType(enum.Enum):
+    STRING = 'string'
+    FLOAT = 'float'
+    INTEGER = 'integer'
+    BOOLEAN = 'boolean'
+    ENUM = 'enum'

sa.py

+import sqlalchemy
+from sqlalchemy.schema import Column
+from sqlalchemy import String, DateTime, Numeric, ARRAY, Table, ForeignKey, Enum, Integer
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import relationship, validates
+from sqlalchemy.orm.session import Session as BaseSession
+
+from .field_types import FieldType
+
+
+# TODO declarative_base
+class Base(object):
+    id = Column(UUID, primary_key=True, default=lambda: str(uuid.uuid4()))
+
+class Session(SessionManager):
+    engine = sqlalchemy.create_engine(config['sqlalchemy.url'])
+
+
+
+# This table maintains the field <-> ObjectType links.
+type_links = Table('type_links', Base.metadata,
+        Column('type_id', UUID, ForeignKey('objecttype.id')),
+        Column('field_id' UUID, ForeignKey('field.id')))
+
+
+
+class MapObject(Base):
+    __tablename__ = 'mapobject' #TODO fix for py3/new sa
+    name = Column(String, nullable=False)
+    type_id = Column(UUID, ForeignKey('objecttype.id')) # TODO fix foreignkeyconstraint
+    type = relationship('ObjectType')
+    lat = Column(Numeric(precision=10, scale=15, asdecimal=False), nullable=False)#TODO this doesn't work
+    lon = Column(Numeric(precision=10, scale=15, asdecimal=False), nullable=False) 
+    data = Column(JSONB)
+
+    @validates('data')
+    def validate_data(self, _, data):
+        if data is None:
+            return
+        fields = type.fields
+        for key in data:
+            for field in fields:
+                if field.name == key:
+                    break
+            else:
+                raise ValueError('extra data must be a registered field')
+            field.validate_data(data[key])
+        return data
+
+class ObjectType(Base):
+    """
+    Represent a schema
+    """
+    __tablename__ = 'objecttype' #TODO py3
+
+    name = Column(String, nullable=False, unique=True)
+    fields = relationship('Field', secondary=type_links, backref='types')
+
+
+class Field(Base):
+    """
+    Represent a field that can be on an ObjectType schema
+    """
+    __tablename__ = 'field' # TODO this don't work in py3?
+
+    name = Column(String, nullable=False, unique=True)
+    type = Column(Enum(FieldType), nullable=False)
+    unit = Column(String)
+    values = Column(ARRAY(String)) # enum values - TODO change to comma-separated list if sqlite don't support?
+    # types: List[ObjectType]
+
+    def validate_data(self, data):
+        """
+        Verify that data is the correct type for this Field.
+        """
+        if self.type is FieldType.BOOLEAN and isinstance(data, bool):
+            return
+        if self.type is FieldType.FLOAT and isinstance(data, float) or isinstance(data, int):
+            return
+        if self.type is FieldType.INTEGER and isinstance(data, int):
+            return
+        if self.type is FieldType.STRING and isinstance(data, str):
+            return
+        if self.type is FieldType.ENUM and isinstance(data, str):
+            if data in self.values:
+                return
+        print(type(data))
+        print(self.type)
+        raise ValueError('Invalid input "{}" for field {}'.format(data, self.name))