"""Utility Functions for Handlers."""

import re
from typing import Any

from flask import request
from marshmallow import Schema
from marshmallow.exceptions import ValidationError
from werkzeug.exceptions import BadRequest, UnsupportedMediaType

from vectororder.constants import search
from vectororder.exceptions import RequestError


def parse_request_json(
    schema: type[Schema],
    partial: bool = False,
    request_data: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Parse and optionally validate request JSON.

    Args:
        schema (type): Marshmallow schema to validate request.
        partial (bool): Partial validation flag.
        request_data (dict): Request data.

    Returns:
        dict: Validated request.

    Raises:
        RequestError: Request JSON is not an object (but a list, for example).
        ValidationError: Request data did not pass the schema validation.
    """
    if not request_data:
        try:
            request_data = request.get_json()
        except (UnsupportedMediaType, BadRequest) as exc:
            raise RequestError("Invalid JSON") from exc

    # Verify request data is wrapped in dict (Marshmallow doesn't catch this).
    if not isinstance(request_data, dict):
        raise RequestError("Request envelope must be an object.")

    if not schema:
        return request_data

    return schema().load(request_data, partial=partial)


def get_order_by(order_by_string: str) -> list[str]:
    """Parse and validate request 'order by' parameter.

    Args:
        order_by_string (str): A comma-delimited string of fields optionally
            prefixed by '-' to indicate a descending order.

    Returns:
        list: A list of fields to order by.

    Raises:
        ValidationError: An exception is raised on invalid input string.
    """
    if not order_by_string:
        return []

    order_by = [field.strip() for field in order_by_string.split(",")]
    order_by_re = re.compile(search.ORDER_BY_RE, re.IGNORECASE)
    for order_by_field in order_by:
        if not order_by_re.fullmatch(order_by_field):
            raise ValidationError(
                "Bad value '{}' in 'order by' field.".format(order_by_field)
            )
    return order_by