app/routes/explain.py

import os
from fastapi import APIRouter, Header, HTTPException
from pydantic import BaseModel
from typing import Optional
from pipeline.explainer import FallacyExplainer

FH_TOKEN = os.environ["FH_TOKEN"]

router = APIRouter()
_explainer = None


def get_explainer():
    global _explainer
    if _explainer is None:
        _explainer = FallacyExplainer()
    return _explainer


class ExplainRequest(BaseModel):
    text: str
    label: str


class ExplainResponse(BaseModel):
    explanation: Optional[str] = None
    highlighted_phrase: Optional[str] = None


@router.post("/explain", response_model=ExplainResponse)
def explain_fallacy(req: ExplainRequest, x_fh_token: str = Header(None)):
    if x_fh_token != FH_TOKEN:
        raise HTTPException(status_code=403, detail="Forbidden")

    explainer = get_explainer()
    definition = explainer.fallacy_definitions.get(req.label.lower(), "")
    result = explainer.explain(req.text, req.label, {"explanation": definition})
    return ExplainResponse(
        explanation=result["explanation"],
        highlighted_phrase=result["highlighted_phrase"],
    )