From b03df823d727c71c827507b4dae6c5819f9eaea7 Mon Sep 17 00:00:00 2001
From: Ferdinand Thiessen <rpm@fthiessen.de>
Date: Sun, 19 Dec 2021 22:11:57 +0100
Subject: [PATCH] feat(db): Add database migration support, implements #19

Migrations allow us to keep track of database changes and upgrading databases if needed.
---
 flaschengeist/app.py      |  3 +-
 flaschengeist/database.py | 24 +++++++++++++
 migrations/alembic.ini    | 52 ++++++++++++++++++++++++++++
 migrations/env.py         | 73 +++++++++++++++++++++++++++++++++++++++
 migrations/script.py.mako | 25 ++++++++++++++
 setup.cfg                 | 11 +++---
 6 files changed, 182 insertions(+), 6 deletions(-)
 create mode 100644 migrations/alembic.ini
 create mode 100644 migrations/env.py
 create mode 100644 migrations/script.py.mako

diff --git a/flaschengeist/app.py b/flaschengeist/app.py
index 6cd99c5..0786745 100644
--- a/flaschengeist/app.py
+++ b/flaschengeist/app.py
@@ -101,10 +101,11 @@ def create_app(test_config=None, cli=False):
     CORS(app)
 
     with app.app_context():
-        from flaschengeist.database import db
+        from flaschengeist.database import db, migrate
 
         configure_app(app, test_config, cli)
         db.init_app(app)
+        migrate.init_app(app, db, compare_type=True)
         __load_plugins(app)
 
     @app.route("/", methods=["GET"])
diff --git a/flaschengeist/database.py b/flaschengeist/database.py
index ebda993..4da914a 100644
--- a/flaschengeist/database.py
+++ b/flaschengeist/database.py
@@ -1,3 +1,6 @@
+import os
+from flask import current_app
+from flask_migrate import Migrate
 from flask_sqlalchemy import SQLAlchemy
 from sqlalchemy import MetaData
 
@@ -14,6 +17,27 @@ metadata = MetaData(
 
 
 db = SQLAlchemy(metadata=metadata)
+migrate = Migrate()
+
+
+@migrate.configure
+def configure_alembic(config):
+    # Load migration paths from plugins
+    migrations = [str(p.migrations_path) for p in current_app.config["FG_PLUGINS"].values() if p and p.migrations_path]
+    if len(migrations) > 0:
+        # Get configured paths
+        paths = config.get_main_option("version_locations")
+        # Get configured path seperator
+        sep = config.get_main_option("version_path_separator", "os")
+        if paths:
+            # Insert configured paths at the front, before plugin migrations
+            migrations.insert(0, config.get_main_option("version_locations"))
+        sep = os.pathsep if sep == "os" else " " if sep == "space" else sep
+        # write back seperator (we changed it if neither seperator nor locations were specified)
+        config.set_main_option("version_path_separator", sep)
+        config.set_main_option("version_locations", sep.join(migrations))
+        print(config.get_main_option("version_locations"))
+    return config
 
 
 def case_sensitive(s):
diff --git a/migrations/alembic.ini b/migrations/alembic.ini
new file mode 100644
index 0000000..e1023e2
--- /dev/null
+++ b/migrations/alembic.ini
@@ -0,0 +1,52 @@
+# A generic, single database configuration.
+
+[alembic]
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+version_path_separator = os
+version_locations = %(here)s/versions
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic,flask_migrate
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[logger_flask_migrate]
+level = INFO
+handlers =
+qualname = flask_migrate
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S
diff --git a/migrations/env.py b/migrations/env.py
new file mode 100644
index 0000000..fd8edac
--- /dev/null
+++ b/migrations/env.py
@@ -0,0 +1,73 @@
+import logging
+from logging.config import fileConfig
+from flask import current_app
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+logger = logging.getLogger("alembic.env")
+
+config.set_main_option("sqlalchemy.url", str(current_app.extensions["migrate"].db.get_engine().url).replace("%", "%%"))
+target_metadata = current_app.extensions["migrate"].db.metadata
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(url=url, target_metadata=target_metadata, literal_binds=True)
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    # this callback is used to prevent an auto-migration from being generated
+    # when there are no changes to the schema
+    # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
+    def process_revision_directives(context, revision, directives):
+        if getattr(config.cmd_opts, "autogenerate", False):
+            script = directives[0]
+            if script.upgrade_ops.is_empty():
+                directives[:] = []
+                logger.info("No changes in schema detected.")
+
+    connectable = current_app.extensions["migrate"].db.get_engine()
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            process_revision_directives=process_revision_directives,
+            **current_app.extensions["migrate"].configure_args
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
diff --git a/migrations/script.py.mako b/migrations/script.py.mako
new file mode 100644
index 0000000..a6f4fdf
--- /dev/null
+++ b/migrations/script.py.mako
@@ -0,0 +1,25 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+import flaschengeist
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}
diff --git a/setup.cfg b/setup.cfg
index b5347c8..d28bc94 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -23,12 +23,13 @@ python_requires = >=3.7
 packages = find:
 install_requires =
     Flask >= 2.0
-    Pillow>=8.4.0
-    flask_cors
-    flask_sqlalchemy>=2.5
-    sqlalchemy>=1.4.26
+    Flask-Cors >= 3.0
+    Flask-Migrate >= 3.1.0 
+    Flask-SQLAlchemy >= 2.5
+    Pillow >= 8.4.0
+    SQLAlchemy >= 1.4.28
     toml
-    werkzeug
+    werkzeug >= 2.0
     PyMySQL;platform_system=='Windows'
     mysqlclient;platform_system!='Windows'