Refactoring of backend: implementing a layered architecture

Author: diofeher

README.md

@@ -6,7 +6,7 @@ General:
 Backend:
 - FastAPI as the Webserver
 - PostgresQL + sqlalchemy on the Backend
-- Alembi for Database migrations
+
 - Containerization with Docker and Uvicorn for serving
 - Ruff for style checks
 - Github Actions as CI/CD for automatic code checking, using Ruff and ESLint
@@ -17,6 +17,11 @@ Frontend:
 - Usage of ESLint for linting
 - Containerization with Docker and Docker compose
 
+TODO:
+- Alembi for Database migrations
+- mypy for static type checking 
+
+
 # Installation
 
 First, we will need to install the dependencies and pre-commit hooks.

backend/app/app.py

@@ -1,7 +1,8 @@
+from .tasks.routers import router as task_router
+from .users.routers import router as user_router
 from fastapi import FastAPI
 from contextlib import asynccontextmanager
 
-from .routers import task, user
 from .db import create_db_and_tables
 
 from fastapi.middleware.cors import CORSMiddleware
@@ -15,8 +16,8 @@ async def lifespan(app: FastAPI):
 
 
 app = FastAPI(lifespan=lifespan)
-app.include_router(task.router)
-app.include_router(user.router)
+app.include_router(task_router)
+app.include_router(user_router)
 
 origins = [
     "*",

backend/app/auth.py

@@ -6,10 +6,11 @@
 
 from fastapi import Depends, HTTPException, status
 from fastapi.security import OAuth2PasswordBearer
-from sqlmodel import Session, select
+from sqlalchemy.orm import Session
+from sqlalchemy import select
 
 from app.db import get_session
-from app.models.user import User, TokenData
+from app.users.models import User, TokenData
 
 # TODO: Pass as configuration, hardcoded for now
 SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
@@ -54,7 +55,7 @@ async def get_current_user(
         raise credentials_exception
 
     stmt = select(User).where(User.username == token_data.username)
-    db_user = session.exec(stmt).first()
+    db_user = session.exec(stmt).first()[0]
     if not db_user:
         raise credentials_exception
     return db_user

backend/app/models/__init__.py

@@ -4,7 +4,8 @@
 class Settings(BaseSettings):
     # TODO: Remove this hardcoded default from here
     database_url: str = (
-        "postgresql+psycopg2://myuser:mypassword@db:5432/mydatabase"
+        # "postgresql+psycopg2://myuser:mypassword@db:5432/mydatabase"
+        "postgresql+psycopg2://myuser:mypassword@localhost:5432/mydatabase"
     )
 
 

backend/app/routers/__init__.py

@@ -25,15 +25,3 @@ class Task(TaskBase, table=True):
     model_config = ConfigDict(validate_assignment=True)
 
     id: int | None = Field(default=None, primary_key=True, index=True)
-
-
-class TaskCreate(TaskBase):
-    pass
-
-
-class TaskUpdate(TaskBase):
-    title: str | None = None
-    description: str | None = None
-    status: TaskStatus | None = Field(
-        sa_column=Column(Enum(TaskStatus)), default=TaskStatus.created
-    )

backend/app/routers/task.py

@@ -0,0 +1,43 @@
+from typing import List, Optional
+from sqlalchemy.orm import Session
+from sqlalchemy import select, update
+from dataclasses import dataclass
+from .models import Task, TaskStatus
+from .schema import TaskInput, TaskOutput
+
+
+@dataclass
+class TaskRepository:
+    session: Session
+    current_user_id: int
+
+    def create(self, data: TaskInput) -> TaskOutput:
+        task = Task(**data.model_dump(exclude_none=True))
+        self.session.add(task)
+        self.session.commit()
+        self.session.refresh(task)
+        return TaskOutput(**dict(task))
+
+    def list(self, offset: int, limit: int) -> List[Optional[TaskOutput]]:
+        stmt = (
+            select(Task)
+            .where(
+                Task.status != TaskStatus.deleted,
+                Task.user_id == self.current_user_id,
+            )
+            .offset(offset)
+            .limit(limit)
+        )
+        tasks = self.session.execute(stmt).all()
+        return [TaskOutput(**dict(task[0])) for task in tasks]
+
+    def get_by_id(self, id: int) -> Task:
+        return self.session.get(Task, id)
+
+    def update(self, task: Task) -> TaskOutput:
+        self.session.execute(
+            update(Task).where(Task.id == task.id).values(**dict(task))
+        )
+        self.session.commit()
+        self.session.refresh(task)
+        return TaskOutput(**dict(task))

backend/app/settings.py

@@ -0,0 +1,63 @@
+from typing import Annotated
+from fastapi import Depends, Query, APIRouter
+from sqlalchemy.orm import Session
+from app.users.models import User
+from app.auth import get_current_active_user
+from app.db import get_session
+from .schema import TaskInput, TaskOutput
+from .service import TaskService
+
+
+router = APIRouter(prefix="/tasks")
+
+
+@router.get("/")
+def read_tasks(
+    *,
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    session: Session = Depends(get_session),
+    offset: int = 0,
+    limit: int = Query(default=100, le=100),
+):
+    return TaskService(session, current_user.id).list(offset, limit)
+
+
+@router.post("/", response_model=TaskOutput)
+def create_task(
+    *,
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    session: Session = Depends(get_session),
+    data: TaskInput,
+):
+    return TaskService(session, current_user.id).create(data)
+
+
+@router.get("/{task_id}")
+def read_task(
+    *,
+    session: Session = Depends(get_session),
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    task_id: int,
+):
+    return TaskService(session, current_user.id).read(task_id)
+
+
+@router.patch("/{task_id}")
+def update_task(
+    *,
+    session: Session = Depends(get_session),
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    task_id: int,
+    task: TaskInput,
+):
+    return TaskService(session, current_user.id).update(task_id, task)
+
+
+@router.delete("/{task_id}")
+def delete_task(
+    *,
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    session: Session = Depends(get_session),
+    task_id: int,
+):
+    return TaskService(session, current_user.id).delete(task_id)

backend/app/models/task.py backend/app/tasks/models.py

@@ -0,0 +1,21 @@
+import datetime
+from typing import Optional
+from pydantic import BaseModel, Field
+from .models import TaskStatus
+
+
+class TaskInput(BaseModel):
+    title: str = Field(min_length=1, max_length=50)
+    description: str | None = None
+    user_id: int | None = None
+    due_date: datetime.datetime | None = None
+    status: TaskStatus = TaskStatus.created
+
+
+class TaskOutput(BaseModel):
+    id: int
+    title: str
+    description: Optional[str] = ""
+    user_id: int
+    due_date: datetime.datetime | None = None
+    status: TaskStatus

backend/app/tasks/repository.py

@@ -0,0 +1,52 @@
+from typing import List
+from sqlalchemy.orm import Session
+from dataclasses import dataclass
+from fastapi import HTTPException
+from .repository import TaskRepository
+from .models import TaskStatus, Task
+from .schema import TaskInput, TaskOutput
+
+
+@dataclass
+class TaskService:
+    session: Session
+    current_user_id: int
+
+    def __post_init__(self):
+        self.repository: TaskRepository = TaskRepository(
+            self.session, self.current_user_id
+        )
+
+    def get_or_not_found(self, task_id: int) -> Task:
+        task = self.repository.get_by_id(task_id)
+        if (not task) or (task.user_id != self.current_user_id):
+            raise HTTPException(status_code=404, detail="Task not found")
+        return task
+
+    def list(self, offset: int, limit: int) -> List[TaskOutput]:
+        return self.repository.list(offset, limit)
+
+    def create(self, data: TaskInput) -> TaskOutput:
+        data.user_id = self.current_user_id
+        return self.repository.create(data)
+
+    def read(self, task_id: int) -> TaskOutput:
+        task = self.get_or_not_found(task_id)
+        return TaskOutput(**dict(task))
+
+    def update(self, task_id: int, data: TaskInput) -> TaskOutput:
+        task = self.get_or_not_found(task_id)
+        task.title = data.title
+        task.description = data.description
+        task.due_date = data.due_date
+
+        task.user_id = self.current_user_id
+        self.repository.update(task)
+        return TaskOutput(**dict(task))
+
+    def delete(self, task_id: int) -> TaskOutput:
+        task = self.get_or_not_found(task_id)
+
+        task.status = TaskStatus.deleted
+        self.repository.update(task)
+        return task

backend/app/tasks/routers.py

@@ -0,0 +1,7 @@
+from dataclasses import dataclass
+from sqlalchemy.orm import Session
+
+
+@dataclass
+class UserRepository:
+    session: Session

backend/app/tasks/schema.py

@@ -7,7 +7,7 @@
 from fastapi.security import OAuth2PasswordRequestForm
 from passlib.hash import pbkdf2_sha256
 
-from app.models.user import User, UserCreate
+from app.users.models import User, UserCreate
 from app.db import get_session
 from app.auth import (
     create_access_token,