import os, sqlite3
from typing import List, Optional
from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
DB_PATH = os.getenv(“DB_PATH”, “/data/app.db”)
app = FastAPI(title=“Minimal Todo CRUD”, description=“Beginner-friendly, zero frontend.”)
class TodoIn(BaseModel):
title: str
completed: bool = False
class TodoUpdate(BaseModel):
title: Optional[str] = None
completed: Optional[bool] = None
class TodoOut(TodoIn):
id: int
def row_to_todo(row) -> TodoOut:
return TodoOut(id=row[“id”], title=row[“title”], completed=bool(row[“completed”]))
def get_conn():
conn = sqlite3.connect(DB_PATH)
conn.row_factory = sqlite3.Row
return conn
@app.on_event(“startup”)
def init_db():
os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)
conn = get_conn()
conn.execute(“””
CREATE TABLE IF NOT EXISTS todos(
id INTEGER PRIMARY KEY AUTOINCREMENT,
title TEXT NOT NULL,
completed INTEGER NOT NULL DEFAULT 0
)
“””)
conn.commit(); conn.close()
@app.post(“/todos”, response_model=TodoOut, status_code=201)
def create_todo(payload: TodoIn):
conn = get_conn()
cur = conn.execute(
“INSERT INTO todos(title, completed) VALUES(?, ?)”,
(payload.title, int(payload.completed))
)
conn.commit()
row = conn.execute(“SELECT * FROM todos WHERE id=?”, (cur.lastrowid,)).fetchone()
conn.close()
return row_to_todo(row)
@app.get(“/todos”, response_model=List[TodoOut])
def list_todos():
conn = get_conn()
rows = conn.execute(“SELECT * FROM todos ORDER BY id DESC”).fetchall()
conn.close()
return [row_to_todo(r) for r in rows]
@app.get(“/todos/{todo_id}”, response_model=TodoOut)
def get_todo(todo_id: int):
conn = get_conn()
row = conn.execute(“SELECT * FROM todos WHERE id=?”, (todo_id,)).fetchone()
conn.close()
if not row:
raise HTTPException(404, “Todo not found”)
return row_to_todo(row)
@app.patch(“/todos/{todo_id}”, response_model=TodoOut)
def update_todo(todo_id: int, payload: TodoUpdate):
data = payload.model_dump(exclude_unset=True)
if not data:
return get_todo(todo_id) # nothing to change
fields, values = [], []
if “title” in data:
fields.append(“title=?”); values.append(data[“title”])
if “completed” in data:
fields.append(“completed=?”); values.append(int(data[“completed”]))
if not fields:
return get_todo(todo_id)
conn = get_conn()
cur = conn.execute(f“UPDATE todos SET {‘, ‘.join(fields)} WHERE id=?”, (*values, todo_id))
if cur.rowcount == 0:
conn.close(); raise HTTPException(404, “Todo not found”)
conn.commit()
row = conn.execute(“SELECT * FROM todos WHERE id=?”, (todo_id,)).fetchone()
conn.close()
return row_to_todo(row)
@app.delete(“/todos/{todo_id}”, status_code=204)
def delete_todo(todo_id: int):
conn = get_conn()
cur = conn.execute(“DELETE FROM todos WHERE id=?”, (todo_id,))
conn.commit(); conn.close()
if cur.rowcount == 0:
raise HTTPException(404, “Todo not found”)
return # 204 No Content