[WIP] Database models to cache the metadata and references

.gitignore

@@ -1,3 +1,4 @@
+app.db
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]

dapitains/app/database.py

@@ -0,0 +1,97 @@
+try:
+    from flask_sqlalchemy import SQLAlchemy
+    from sqlalchemy.ext.mutable import MutableDict
+    from sqlalchemy.types import TypeDecorator, TEXT
+    import click
+except ImportError:
+    print("This part of the package can only be imported with the web requirements.")
+    raise
+
+import dapitains.metadata.classes as abstracts
+import json
+
+db = SQLAlchemy()
+
+parent_child_association = db.Table('parent_child_association',
+    db.Column('parent_id', db.Integer, db.ForeignKey('collections.id'), primary_key=True),
+    db.Column('child_id', db.Integer, db.ForeignKey('collections.id'), primary_key=True)
+)
+
+
+class JSONEncodedDict(TypeDecorator):
+    """Enables JSON storage by encoding and decoding on the fly."""
+    impl = TEXT
+
+    def process_bind_param(self, value, dialect):
+        if value is None:
+            return ''
+        elif isinstance(value, dict):
+            return json.dumps(value)
+        return value
+
+    def process_result_value(self, value, dialect):
+        if value is None:
+            return '""'
+        return json.loads(value)
+
+class Collection(db.Model):
+    __tablename__ = 'collections'
+
+    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
+    identifier = db.Column(db.String, nullable=False, unique=True)
+    title = db.Column(db.String, nullable=False)
+    description = db.Column(db.String, nullable=True)
+    resource = db.Column(db.Boolean, default=False)
+    filepath = db.Column(db.String, nullable=True)
+    dublin_core = db.Column(MutableDict.as_mutable(JSONEncodedDict), nullable=True)
+    extensions = db.Column(MutableDict.as_mutable(JSONEncodedDict), nullable=True)
+
+    # One-to-one relationship with Navigation
+    navigation = db.relationship('Navigation', uselist=False, backref='collection', lazy='noload')
+
+
+    parents = db.relationship(
+        'Collection',
+        secondary=parent_child_association,
+        primaryjoin=id == parent_child_association.c.child_id,
+        secondaryjoin=id == parent_child_association.c.parent_id,
+        backref='children'
+    )
+
+    @classmethod
+    def from_class(cls, obj: abstracts.Collection) -> "Collection":
+        return cls(
+            identifier=obj.identifier,
+            title=obj.title,
+            description=obj.description,
+            resource=obj.resource,
+            filepath=obj.filepath,
+            # We are dumping because it's not read or accessible
+            dublin_core=json.dumps([dub.json() for dub in obj.dublin_core]),
+            extensions=json.dumps([ext.json() for ext in obj.extension])
+        )
+
+class Navigation(db.Model):
+    __tablename__ = 'navigations'
+
+    id = db.Column(db.Integer, primary_key=True)
+    collection_id = db.Column(db.Integer, db.ForeignKey('collections.id'), nullable=False, unique=True)
+    default_tree = db.Column(db.String, nullable=True)
+
+    # JSON fields stored as TEXT
+    paths = db.Column(MutableDict.as_mutable(JSONEncodedDict), nullable=False, default={})
+    references = db.Column(MutableDict.as_mutable(JSONEncodedDict), nullable=False, default={})
+
+if __name__ == "__main__":
+    import flask
+    import os
+    app = flask.Flask(__name__)
+
+    basedir = os.path.abspath(os.path.dirname(__file__))
+    db_path = os.path.join(basedir, 'app.db')
+    app.config['SQLALCHEMY_DATABASE_URI'] = f'sqlite:///{db_path}'
+    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
+
+    db.init_app(app)
+    with app.app_context():
+        db.create_all()