# =============================================================================
# QWHPI — Quebec Weekly Housing Price Index
# Author  : Simon-Pierre Boucher
# Contact : contact@spboucher.ai
# File    : api/app/deps.py
# Purpose : Shared dependencies — series validation, ETag and CSV helpers.
# =============================================================================
"""Shared FastAPI dependencies and response helpers."""

from __future__ import annotations

import hashlib

import polars as pl
from fastapi import HTTPException, Request, Response

from app.services import data

VALID_TYPES = {"all", "unifamilial", "condo", "plex"}


def validate_series(geography: str, property_type: str) -> None:
    if property_type not in VALID_TYPES:
        raise HTTPException(422, f"property_type must be one of {sorted(VALID_TYPES)}")
    if geography not in data.geography_ids():
        raise HTTPException(404, f"unknown geography '{geography}' — see /v1/geographies")


def etag_for(request: Request, response: Response, *parts: str) -> bool:
    """Set the ETag; return True when the client's copy is fresh (304)."""
    raw = "|".join([data.data_vintage(), data.model_version(),
                    str(request.url), *parts])
    tag = '"' + hashlib.sha256(raw.encode()).hexdigest()[:32] + '"'
    response.headers["ETag"] = tag
    response.headers["Cache-Control"] = "public, max-age=300"
    return request.headers.get("if-none-match") == tag


def csv_response(df: pl.DataFrame) -> Response:
    return Response(
        content=df.write_csv(),
        media_type="text/csv",
        headers={"X-Author": "Simon-Pierre Boucher <contact@spboucher.ai>"},
    )