"""Feature blueprints registered by app.py (one module per page group).

    views.dell_updates   - Updates > Dell drivers and BIOS
    views.ipxe           - Updates > iPXE Secure Boot files
    views.blancco_update - Updates > Blancco Drive Eraser releases

Shared here: the download speed cap form handler. The cap is one setting
(services/updates_common.py settings.json) used by every download; each
Updates page with downloads shows the same form and posts it to its own
route, which calls save_speed_cap() and redirects back to that page.
"""

import math

from flask import flash, request

from services import updates_common
from services.audit import audit


def save_speed_cap():
    """Validate and save the shared speed cap from the posted form, audit and
    flash the result. Returns the saved settings, or None when refused."""
    try:
        value = float(request.form.get("max_mbps", ""))
        if not math.isfinite(value):  # float() accepts "nan"
            raise ValueError("not a number")
        data = updates_common.save_settings(value)
    except ValueError as ex:
        msg = str(ex) if "between" in str(ex) else "enter a number of MB/s (0 = no cap)"
        flash(f"Speed cap not saved: {msg}", "danger")
        return None
    audit("UPDATES_SPEED_CAP", f"{data['max_mbps']} MB/s")
    cap = data["max_mbps"]
    flash(f"Download speed cap set to {cap:g} MB/s (shared by Dell and iPXE downloads)."
          if cap else "Download speed cap removed (shared by Dell and iPXE downloads).", "success")
    return data