Make a squash

web/db.py

@@ -0,0 +1,58 @@
+import contextlib
+import json
+import pathlib
+import time
+
+import click
+import flask
+import flask.cli
+
+def lock(name):
+    lockfile = pathlib.Path(f'{name}.lock')
+    for i in range(5):
+        try:
+            lockfile.symlink_to('/dev/null')
+            return
+        except FileExistsError:
+            time.sleep(1)
+    raise TimeoutError(f'could not lock {name}')
+
+def unlock(name):
+    lockfile = pathlib.Path(f'{name}.lock')
+    lockfile.unlink(missing_ok=True)
+
+@contextlib.contextmanager
+def locked(name):
+    lock(name)
+    try:
+        yield name
+    finally:
+        unlock(name)
+
+def read(name):
+    with open(f'{name}.json', 'a+', encoding='utf-8') as f:
+        f.seek(0)
+        return json.loads(f.read() or '{}')
+
+def write(name, data):
+    with open(f'{name}.json', 'w', encoding='utf-8') as f:
+        json.dump(data, f, indent=2)
+        f.close()
+
+def load(name):
+    with locked(name):
+        return read(name)
+
+def save(name, data):
+    with locked(name):
+        write(name, data)
+
+def init_app(app):
+    #app.teardown_appcontext(close_db)
+    app.cli.add_command(init_db)
+
+@click.command('init-db')
+@flask.cli.with_appcontext
+def init_db():
+    """Clear the existing data and create new tables."""
+    pass # TODO, if needed