"""The boundary between an HTTP form and a validated payload (ARCH-005).

Every POST in this application arrives as a `werkzeug.MultiDict` of strings.
Turning that into typed, checked values was done inline, differently, in each
route: `int(x) if x else None` here, `datetime.strptime` inside a bare `try`
there, and in several places not at all. The failures that produced were not
loud ones — a bad time silently became `None` and the page said the match had
been updated.

Two functions here, one schema module next to them (`app.validators`):

    payload = form_payload(list_fields=('player_ids',))
    try:
        data = MatchSchema().load(payload)
    except ValidationError as err:
        flash_validation_errors(err)
        return _rerender()

Both were originally inside `app/routes/users/_shared.py`, which is where
they were first needed. They are re-exported from there so that nothing had
to be renamed when the match and tryout routes started using them too.
"""

from flask import flash, request
from flask_babel import gettext as _


def flash_validation_errors(err):
    """Surface marshmallow errors, one flash per problem.

    The uniform reporting half of ARCH-005: before this, a bad date flashed
    'Invalid date format.' from one route, redirected from another, and was
    silently dropped by a third.
    """
    for field, messages in err.messages.items():
        for msg in messages:
            flash(_('%(field)s: %(msg)s', field=field, msg=msg), 'danger')


def form_payload(*, checkboxes=(), list_fields=('games',), optional_blank=('password',)):
    """Turn the multi-valued request form into a plain dict for marshmallow.

    request.form.to_dict() keeps only the first value of a repeated key, so
    list fields have to be re-read with getlist(). Unchecked HTML checkboxes
    are simply absent from the submission, which is not the same as a schema
    default, so they are injected explicitly. Blank optional fields are
    dropped rather than sent as '' — an empty password means "leave the
    current one alone", not "set the password to the empty string".

    Args:
        checkboxes: Names to report as True/False on presence.
        list_fields: Names to read with getlist(), always producing a list.
        optional_blank: Names to drop entirely when submitted empty.
    """
    payload = request.form.to_dict()
    for name in list_fields:
        payload[name] = request.form.getlist(name)
    for name in checkboxes:
        payload[name] = name in request.form
    for name in optional_blank:
        if not payload.get(name):
            payload.pop(name, None)
    return payload