from datetime import timedelta

from django.utils import timezone

from communications.models import ChatUserSettings


def update_chat_notification_preferences(
    settings: ChatUserSettings,
    *,
    preferences: dict,
) -> ChatUserSettings:
    """Apply validated preferences while preserving the legacy empty toggle."""
    update_fields = set()
    if not preferences:
        settings.notification_mode = (
            ChatUserSettings.NotificationMode.MENTIONS
            if settings.effective_notification_mode()
            == ChatUserSettings.NotificationMode.ALL
            else ChatUserSettings.NotificationMode.ALL
        )
        settings.muted_until = None
        update_fields.update({"notification_mode", "muted_until"})
    else:
        mode = preferences.get("notification_mode")
        if mode is not None:
            settings.notification_mode = mode
            update_fields.add("notification_mode")
            if mode == ChatUserSettings.NotificationMode.MUTED:
                settings.muted_until = None
                update_fields.add("muted_until")

        if "mute_for_seconds" in preferences:
            seconds = preferences["mute_for_seconds"]
            settings.muted_until = (
                timezone.now() + timedelta(seconds=seconds) if seconds else None
            )
            update_fields.add("muted_until")

        if "muted_until" in preferences:
            settings.muted_until = preferences["muted_until"]
            update_fields.add("muted_until")

        for field in (
            "show_notification_preview",
            "notification_sound_enabled",
        ):
            if field in preferences:
                setattr(settings, field, preferences[field])
                update_fields.add(field)

    settings.notifications_enabled = (
        settings.notification_mode == ChatUserSettings.NotificationMode.ALL
        and not (settings.muted_until and settings.muted_until > timezone.now())
    )
    update_fields.add("notifications_enabled")
    settings.save(update_fields=sorted(update_fields))
    return settings