feat(backend): file deletion flow (#16)

* feat(backend): file deletion flow

* ci: set change-check flags when no changes detected

* feat(backend): refactor settings to be a singleton object

* refactor(backend): cleaning delete flow cruft

* test(backend): add coverage for deletion + adapt coverage to only rely on endpoints

* docs: type responses for deletions

.github/workflows/ci.yml

@@ -41,10 +41,14 @@ jobs:
           if [ -n "$(git diff --name-only origin/main origin/${GITHUB_HEAD_REF} -- ./frontend)" ]
           then
             echo "fe_changed=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "fe_changed=false" >> "$GITHUB_OUTPUT"
           fi
           if [ -n "$(git diff --name-only origin/main origin/${GITHUB_HEAD_REF} -- ./backend)" ]
           then
             echo "be_changed=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "be_changed=false" >> "$GITHUB_OUTPUT"
           fi
   backend:
     uses: ./.github/workflows/backend-pipeline.yml

Taskfile.backend.yml

@@ -47,6 +47,8 @@ tasks:
   migrate:
     desc: "Applies migrations. Usage: be:migrate -- <up|down>"
     deps: [bootstrap]
+    env:
+      PYTHONPATH: '..'
     dotenv:
       - "{{ .DOTENV }}"
     cmd: "{{ .VENV_BIN }}/python migrate.py {{ .CLI_ARGS }}"

backend/requirements.in

@@ -2,3 +2,4 @@ fastapi~=0.101
 uvicorn[standard]
 python-multipart
 psycopg2
+typing_extensions

backend/requirements.txt

@@ -34,6 +34,7 @@ starlette==0.27.0
     # via fastapi
 typing-extensions==4.7.1
     # via
+    #   -r requirements.in
     #   fastapi
     #   pydantic
     #   pydantic-core

backend/rotini/api/files.py

@@ -5,9 +5,12 @@ This API allows users to create and query for existing data about
 files that live in the system.
 """
 
+import pathlib
+
 from fastapi import APIRouter, HTTPException, UploadFile
 
 import use_cases.files as files_use_cases
+from settings import settings
 
 router = APIRouter(prefix="/files")
 
@@ -23,11 +26,12 @@ async def upload_file(file: UploadFile):
     size = len(content)
     await file.seek(0)
 
-    with open(file.filename, "wb") as f:
+    dest_path = pathlib.Path(settings.STORAGE_ROOT, file.filename)
+    with open(dest_path, "wb") as f:
         content = await file.read()
         f.write(content)
 
-    created_record = files_use_cases.create_file_record(file.filename, size)
+    created_record = files_use_cases.create_file_record(str(dest_path), size)
 
     return created_record
 
@@ -40,3 +44,31 @@ def get_file_details(file_id: str):
         raise HTTPException(status_code=404)
 
     return file
+
+
+@router.delete("/{file_id}/")
+def delete_file(file_id: str) -> files_use_cases.FileRecord:
+    """
+    Deletes a file given its ID.
+
+    This will delete the file in the database records as well
+    as on disk. The operation is not reversible.
+
+    DELETE /files/{file_id}/
+
+    200 { <FileRecord> }
+
+        The file exists and has been deleted from storage and
+        from the database.
+
+    404 {}
+
+        The file ID did not map to anything.
+
+    """
+    try:
+        file = files_use_cases.delete_file_record_by_id(file_id)
+    except files_use_cases.DoesNotExist as exc:
+        raise HTTPException(status_code=404) from exc
+
+    return file

backend/rotini/db.py

@@ -1,6 +1,6 @@
 import psycopg2
 
-import settings
+from settings import settings
 
 
 def get_connection():

backend/rotini/envs/test.py

@@ -1,5 +1,9 @@
+import os
+
 DATABASE_USERNAME = "postgres"
 DATABASE_PASSWORD = "test"
 DATABASE_HOST = "localhost"
 DATABASE_PORT = 5431
 DATABASE_NAME = "postgres"
+
+STORAGE_ROOT = os.getenv("ROTINI_STORAGE_ROOT")

backend/rotini/migrations/migrate.py

@@ -27,7 +27,6 @@ Not including a migration name executes everything from the last executed
 migration.
 """
 
-import os
 import collections
 import pathlib
 import datetime
@@ -38,7 +37,7 @@ import sys
 
 import psycopg2
 
-import settings
+from settings import settings
 
 VALID_COMMANDS = ["up", "down", "new"]
 

backend/rotini/settings.py

@@ -1,12 +1,50 @@
-# pylint: disable=unused-import, wildcard-import, unused-wildcard-import
+# pylint: disable=unused-import, wildcard-import, unused-wildcard-import, too-few-public-methods
 import os
+import typing
 
 IS_CI = os.getenv("ROTINI_CI")
 IS_TEST = os.getenv("ROTINI_TEST")
 
+
+class Settings:
+    """
+    Representation of the configuration settings available to the
+    application.
+    """
+
+    ENV: str
+    DATABASE_USERNAME: str
+    DATABASE_PASSWORD: str
+    DATABASE_HOST: str
+    DATABASE_PORT: int
+    DATABASE_NAME: str
+    STORAGE_ROOT: typing.Optional[str] = "."
+
+    def __init__(self, *_, **kwargs):
+        for key, value in kwargs.items():
+            setattr(self, key, value)
+
+
+def extract_settings(env: str, imported_module) -> Settings:
+    """
+    Extracts all the exposed values from the given module and
+    creates a corresponding Settings object.
+    """
+    imported_values = {
+        k: v for k, v in imported_module.__dict__.items() if not k.startswith("__")
+    }
+    return Settings(ENV=env, **imported_values)
+
+
 if IS_CI is not None:
-    from envs.ci import *
+    import envs.ci as ci_config
+
+    settings = extract_settings("ci", ci_config)
 elif IS_TEST is not None:
-    from envs.test import *
+    import envs.test as test_config
+
+    settings = extract_settings("ci", test_config)
 else:
-    from envs.local import *
+    import envs.local as local_config
+
+    settings = extract_settings("ci", local_config)

backend/rotini/use_cases/files.py

@@ -5,10 +5,18 @@ Use cases and data structures defined in this file
 manipulate file records in the database or represent them
 after they have been read.
 """
-import typing
 import pathlib
 
+import typing_extensions as typing
+
 from db import get_connection
+from settings import settings
+
+
+class DoesNotExist(Exception):
+    """
+    General purpose exception signalling a failure to find a database record.
+    """
 
 
 class FileRecord(typing.TypedDict):
@@ -84,3 +92,25 @@ def get_file_record_by_id(file_id: str) -> typing.Optional[FileRecord]:
     return FileRecord(
         id=row[0], path=row[1], size=row[2], filename=pathlib.Path(row[1]).name
     )
+
+
+def delete_file_record_by_id(file_id: str) -> typing.Union[typing.NoReturn, FileRecord]:
+    """
+    Deletes a single file by ID, including its presence in storage.
+
+    If the ID doesn't correspond to a record, DoesNotExist is raised.
+    """
+
+    row = None
+    with get_connection() as connection, connection.cursor() as cursor:
+        cursor.execute("DELETE FROM files WHERE id=%s RETURNING *;", (file_id,))
+        row = cursor.fetchone()
+
+    if row is None:
+        raise DoesNotExist()
+
+    pathlib.Path(pathlib.Path(settings.STORAGE_ROOT, row[1])).unlink()
+
+    return FileRecord(
+        id=row[0], path=row[1], size=row[2], filename=pathlib.Path(row[1]).name
+    )

backend/tests/conftest.py

@@ -1,9 +1,12 @@
 from fastapi.testclient import TestClient
 import pytest
+import unittest.mock
 
 from rotini.main import app
 from rotini.db import get_connection
 
+from settings import settings
+
 
 @pytest.fixture(name="client")
 def fixture_client():
@@ -12,5 +15,21 @@ def fixture_client():
 
 @pytest.fixture(autouse=True)
 def reset_database():
+    """
+    Empties all user tables between tests.
+    """
     with get_connection() as conn, conn.cursor() as cursor:
         cursor.execute("DELETE FROM files;")
+
+
+@pytest.fixture(autouse=True)
+def set_storage_path(tmp_path, monkeypatch):
+    """
+    Ensures that files stored by tests are stored
+    in temporary directories.
+    """
+
+    files_dir = tmp_path / "files"
+    files_dir.mkdir()
+
+    monkeypatch.setattr(settings, "STORAGE_ROOT", str(files_dir))

backend/tests/test_api_files.py

@@ -1,23 +1,43 @@
-from rotini.use_cases import files as files_use_cases
+import pathlib
 
 
-def test_list_files_returns_registered_files_and_200(client):
+def test_list_files_returns_registered_files_and_200(client, tmp_path):
-    file_1 = files_use_cases.create_file_record("/test1.txt", 123)
+    mock_file_1 = tmp_path / "test1.txt"
-    file_2 = files_use_cases.create_file_record("/test2.txt", 456)
+    mock_file_1.write_text("testtest")
+
+    with open(str(mock_file_1), "rb") as mock_file_stream:
+        response = client.post("/files/", files={"file": mock_file_stream})
+
+    mock_file_1_data = response.json()
+
+    mock_file_2 = tmp_path / "test2.txt"
+    mock_file_2.write_text("testtest")
+
+    with open(str(mock_file_2), "rb") as mock_file_stream:
+        response = client.post("/files/", files={"file": mock_file_stream})
+
+    mock_file_2_data = response.json()
 
     response = client.get("/files/")
 
     assert response.status_code == 200
-    assert response.json() == [file_1, file_2]
+    assert response.json() == [mock_file_1_data, mock_file_2_data]
 
 
-def test_file_details_returns_specified_file_and_200(client):
+def test_file_details_returns_specified_file_and_200(client, tmp_path):
-    file = files_use_cases.create_file_record("/test1.txt", 123)
+    mock_file = tmp_path / "test.txt"
+    mock_file.write_text("testtest")
 
-    response = client.get(f"/files/{file['id']}/")
+    with open(str(mock_file), "rb") as mock_file_stream:
+        response = client.post("/files/", files={"file": mock_file_stream})
+
+    response_data = response.json()
+    created_file_id = response_data["id"]
+
+    response = client.get(f"/files/{created_file_id}/")
 
     assert response.status_code == 200
-    assert response.json() == file
+    assert response.json() == response_data
 
 
 def test_file_details_returns_404_if_does_not_exist(client):
@@ -25,3 +45,50 @@ def test_file_details_returns_404_if_does_not_exist(client):
     response = client.get(f"/files/{non_existent_id}/")
 
     assert response.status_code == 404
+
+
+def test_file_deletion_returns_404_if_does_not_exist(client):
+    non_existent_id = "06f02980-864d-4832-a894-2e9d2543a79a"
+    response = client.delete(f"/files/{non_existent_id}/")
+
+    assert response.status_code == 404
+
+
+def test_file_deletion_deletes_record_and_file(client, tmp_path):
+    mock_file = tmp_path / "test.txt"
+    mock_file.write_text("testtest")
+
+    with open(str(mock_file), "rb") as mock_file_stream:
+        response = client.post("/files/", files={"file": mock_file_stream})
+
+    response_data = response.json()
+    file_id = response_data["id"]
+    file_path = response_data["path"]
+
+    assert pathlib.Path(file_path).exists()
+    response = client.get(f"/files/{file_id}/")
+
+    assert response.status_code == 200
+
+    client.delete(f"/files/{file_id}/")
+    assert not pathlib.Path(file_path).exists()
+
+    response = client.get(f"/files/{file_id}/")
+
+    assert response.status_code == 404
+
+
+def test_file_deletion_200_and_return_deleted_resource(client, tmp_path):
+    mock_file = tmp_path / "test.txt"
+    mock_file.write_text("testtest")
+
+    with open(str(mock_file), "rb") as mock_file_stream:
+        response = client.post("/files/", files={"file": mock_file_stream})
+
+    response_data = response.json()
+    file_id = response_data["id"]
+
+    response = client.delete(f"/files/{file_id}/")
+
+    assert response.status_code == 200
+    assert response.json() == response_data