from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
from typing import List, Optional

app = FastAPI()

class Task(BaseModel):
    id: int
    title: str
    description: Optional[str] = None
    done: bool = False

tasks: List[Task] = []

@app.get("/")
def root():
    return {"message": "Willkommen bei der ToDo-API! Siehe /tasks"}

@app.get("/tasks", response_model=List[Task])
def get_tasks():
    return tasks

@app.post("/tasks", response_model=Task)
def create_task(task: Task):
    if any(t.id == task.id for t in tasks):
        raise HTTPException(status_code=400, detail="ID existiert bereits.")
    tasks.append(task)
    return task

@app.get("/tasks/{task_id}", response_model=Task)
def get_task(task_id: int):
    for task in tasks:
        if task.id == task_id:
            return task
    raise HTTPException(status_code=404, detail="Aufgabe nicht gefunden.")

@app.put("/tasks/{task_id}/done", response_model=Task)
def mark_task_done(task_id: int):
    for task in tasks:
        if task.id == task_id:
            task.done = True
            return task
    raise HTTPException(status_code=404, detail="Aufgabe nicht gefunden.")

@app.delete("/tasks/{task_id}")
def delete_task(task_id: int):
    for i, task in enumerate(tasks):
        if task.id == task_id:
            del tasks[i]
            return {"detail": "Aufgabe gelöscht."}
    raise HTTPException(status_code=404, detail="Aufgabe nicht gefunden.")