From 63584ccba6c12cebe806212e7e2a5032697d6c5c Mon Sep 17 00:00:00 2001
From: Mark Hobson <mark.hobson@activetravelengland.gov.uk>
Date: Fri, 20 Oct 2023 11:51:00 +0100
Subject: [PATCH] GH-4: Introduce Alembic for database migrations

---
 alembic.ini                                   |  2 ++
 pyproject.toml                                |  1 +
 schemes/__init__.py                           | 17 +++++++----
 schemes/migrations/env.py                     |  7 +++++
 schemes/migrations/script.py.mako             | 24 ++++++++++++++++
 .../bfc3cbc1bb13_create_users_table.py        | 28 +++++++++++++++++++
 6 files changed, 73 insertions(+), 6 deletions(-)
 create mode 100644 alembic.ini
 create mode 100644 schemes/migrations/env.py
 create mode 100644 schemes/migrations/script.py.mako
 create mode 100644 schemes/migrations/versions/bfc3cbc1bb13_create_users_table.py

diff --git a/alembic.ini b/alembic.ini
new file mode 100644
index 00000000..d58f776a
--- /dev/null
+++ b/alembic.ini
@@ -0,0 +1,2 @@
+[alembic]
+script_location = schemes:migrations
diff --git a/pyproject.toml b/pyproject.toml
index f5a3ce8a..746bf1f6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,6 +4,7 @@ version = "1.0.0"
 description = "ATE Schemes App."
 requires-python = ">=3.11"
 dependencies = [
+    "alembic~=1.12.0",
     "authlib~=1.2.0",
     "flask~=2.3.0",
     "govuk-frontend-jinja~=2.7.0",
diff --git a/schemes/__init__.py b/schemes/__init__.py
index e30660ba..c21bacec 100644
--- a/schemes/__init__.py
+++ b/schemes/__init__.py
@@ -1,17 +1,19 @@
 import os
 from typing import Any, Mapping
 
+import alembic.config
 import inject
+from alembic import command
 from authlib.integrations.flask_client import OAuth
 from authlib.oauth2.rfc7523 import PrivateKeyJWT
 from flask import Config, Flask, Response, render_template, request, url_for
 from inject import Binder
 from jinja2 import ChoiceLoader, FileSystemLoader, PackageLoader, PrefixLoader
-from sqlalchemy import Engine, MetaData, create_engine
+from sqlalchemy import Engine, create_engine
 
 from schemes import api, auth, home, start
 from schemes.config import DevConfig
-from schemes.users import DatabaseUserRepository, User, UserRepository, add_tables
+from schemes.users import DatabaseUserRepository, User, UserRepository
 
 
 def create_app(test_config: Mapping[str, Any] | None = None) -> Flask:
@@ -107,11 +109,14 @@ def _configure_oidc(app: Flask) -> None:
 
 
 def _create_database() -> None:
-    metadata = MetaData()
-    add_tables(metadata)
-
     engine = inject.instance(Engine)
-    metadata.create_all(engine)
+
+    alembic_config = alembic.config.Config()
+    alembic_config.set_main_option("script_location", "schemes:migrations")
+
+    with engine.connect() as connection:
+        alembic_config.attributes["connection"] = connection
+        command.upgrade(alembic_config, "head")
 
 
 def _configure_users() -> None:
diff --git a/schemes/migrations/env.py b/schemes/migrations/env.py
new file mode 100644
index 00000000..171a8e82
--- /dev/null
+++ b/schemes/migrations/env.py
@@ -0,0 +1,7 @@
+from alembic import context
+
+connection = context.config.attributes["connection"]
+context.configure(connection=connection, target_metadata=None)
+
+with context.begin_transaction():
+    context.run_migrations()
diff --git a/schemes/migrations/script.py.mako b/schemes/migrations/script.py.mako
new file mode 100644
index 00000000..765291af
--- /dev/null
+++ b/schemes/migrations/script.py.mako
@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = ${repr(up_revision).replace("'", '"')}
+down_revision: Union[str, None] = ${repr(down_revision).replace("'", '"')}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels).replace("'", '"')}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on).replace("'", '"')}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}
diff --git a/schemes/migrations/versions/bfc3cbc1bb13_create_users_table.py b/schemes/migrations/versions/bfc3cbc1bb13_create_users_table.py
new file mode 100644
index 00000000..496148e5
--- /dev/null
+++ b/schemes/migrations/versions/bfc3cbc1bb13_create_users_table.py
@@ -0,0 +1,28 @@
+"""Create users table
+
+Revision ID: bfc3cbc1bb13
+Revises: 
+Create Date: 2023-10-20 10:15:51.912421
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "bfc3cbc1bb13"
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "users",
+        sa.Column("id", sa.Integer, primary_key=True),
+        sa.Column("email", sa.String(256), nullable=False, unique=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("users")