from __future__ import annotations

import urllib.parse

from fastapi import HTTPException, Request

from ..settings import DdnsSettings

MAX_FORM_FIELDS = 100


def parse_form(body: bytes) -> dict[str, list[str]]:
    try:
        decoded = body.decode("utf-8")
    except UnicodeDecodeError as exc:
        raise HTTPException(status_code=400, detail="form body must be valid UTF-8") from exc
    try:
        return urllib.parse.parse_qs(decoded, keep_blank_values=True, max_num_fields=MAX_FORM_FIELDS)
    except ValueError as exc:
        raise HTTPException(
            status_code=400, detail=f"form must not contain more than {MAX_FORM_FIELDS} fields"
        ) from exc


async def request_form(request: Request, settings: DdnsSettings) -> dict[str, list[str]]:
    body = await request.body()
    if len(body) > settings.max_request_body_bytes:
        raise HTTPException(status_code=413, detail="request body too large")
    return parse_form(body)


def first_form_value(form: dict[str, list[str]], key: str) -> str:
    return form.get(key, [""])[0].strip()