// Copyright (c) 2017 The vulkano developers
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or https://opensource.org/licenses/MIT>,
// at your option. All files in the project carrying such
// notice may not be copied, modified, or distributed except
// according to those terms.

use std::sync::Arc;

use crate::buffer::BufferAccess;
use crate::command_buffer::submit::SubmitAnyBuilder;
use crate::device::Device;
use crate::device::DeviceOwned;
use crate::device::Queue;
use crate::image::ImageAccess;
use crate::image::ImageLayout;
use crate::sync::AccessCheckError;
use crate::sync::AccessFlags;
use crate::sync::FlushError;
use crate::sync::GpuFuture;
use crate::sync::PipelineStages;

/// Builds a future that represents "now".
#[inline]
pub fn now(device: Arc<Device>) -> NowFuture {
    NowFuture { device: device }
}

/// A dummy future that represents "now".
pub struct NowFuture {
    device: Arc<Device>,
}

unsafe impl GpuFuture for NowFuture {
    #[inline]
    fn cleanup_finished(&mut self) {}

    #[inline]
    unsafe fn build_submission(&self) -> Result<SubmitAnyBuilder, FlushError> {
        Ok(SubmitAnyBuilder::Empty)
    }

    #[inline]
    fn flush(&self) -> Result<(), FlushError> {
        Ok(())
    }

    #[inline]
    unsafe fn signal_finished(&self) {}

    #[inline]
    fn queue_change_allowed(&self) -> bool {
        true
    }

    #[inline]
    fn queue(&self) -> Option<Arc<Queue>> {
        None
    }

    #[inline]
    fn check_buffer_access(
        &self,
        buffer: &dyn BufferAccess,
        _: bool,
        _: &Queue,
    ) -> Result<Option<(PipelineStages, AccessFlags)>, AccessCheckError> {
        Err(AccessCheckError::Unknown)
    }

    #[inline]
    fn check_image_access(
        &self,
        _: &dyn ImageAccess,
        _: ImageLayout,
        _: bool,
        _: &Queue,
    ) -> Result<Option<(PipelineStages, AccessFlags)>, AccessCheckError> {
        Err(AccessCheckError::Unknown)
    }
}

unsafe impl DeviceOwned for NowFuture {
    #[inline]
    fn device(&self) -> &Arc<Device> {
        &self.device
    }
}