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    // Copyright (c) 2016 The vulkano developers
    // Licensed under the Apache License, Version 2.0
    // <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT
    // license <LICENSE-MIT or http://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::error;
    use std::fmt;
    use std::sync::Arc;

    use OomError;
    use buffer::BufferAccess;
    use command_buffer::CommandBuffer;
    use command_buffer::CommandBufferExecError;
    use command_buffer::CommandBufferExecFuture;
    use command_buffer::submit::SubmitAnyBuilder;
    use command_buffer::submit::SubmitBindSparseError;
    use command_buffer::submit::SubmitCommandBufferError;
    use command_buffer::submit::SubmitPresentError;
    use device::DeviceOwned;
    use device::Queue;
    use image::ImageAccess;
    use image::ImageLayout;
    use swapchain;
    use swapchain::PresentFuture;
    use swapchain::PresentRegion;
    use swapchain::Swapchain;
    use sync::AccessFlagBits;
    use sync::FenceWaitError;
    use sync::PipelineStages;

    pub use self::fence_signal::{FenceSignalFuture, FenceSignalFutureBehavior};
    pub use self::join::JoinFuture;
    pub use self::now::{NowFuture, now};
    pub use self::semaphore_signal::SemaphoreSignalFuture;

    mod now;
    mod fence_signal;
    mod join;
    mod semaphore_signal;

    /// Represents an event that will happen on the GPU in the future.
    ///
    /// See the documentation of the `sync` module for explanations about futures.
    // TODO: consider switching all methods to take `&mut self` for optimization purposes
    pub unsafe trait GpuFuture: DeviceOwned {
        /// If possible, checks whether the submission has finished. If so, gives up ownership of the
        /// resources used by these submissions.
        ///
        /// It is highly recommended to call `cleanup_finished` from time to time. Doing so will
        /// prevent memory usage from increasing over time, and will also destroy the locks on
        /// resources used by the GPU.
        fn cleanup_finished(&mut self);

        /// Builds a submission that, if submitted, makes sure that the event represented by this
        /// `GpuFuture` will happen, and possibly contains extra elements (eg. a semaphore wait or an
        /// event wait) that makes the dependency with subsequent operations work.
        ///
        /// It is the responsibility of the caller to ensure that the submission is going to be
        /// submitted only once. However keep in mind that this function can perfectly be called
        /// multiple times (as long as the returned object is only submitted once).
        /// Also note that calling `flush()` on the future  may change the value returned by
        /// `build_submission()`.
        ///
        /// It is however the responsibility of the implementation to not return the same submission
        /// from multiple different future objects. For example if you implement `GpuFuture` on
        /// `Arc<Foo>` then `build_submission()` must always return `SubmitAnyBuilder::Empty`,
        /// otherwise it would be possible for the user to clone the `Arc` and make the same
        /// submission be submitted multiple times.
        ///
        /// It is also the responsibility of the implementation to ensure that it works if you call
        /// `build_submission()` and submits the returned value without calling `flush()` first. In
        /// other words, `build_submission()` should perform an implicit flush if necessary.
        ///
        /// Once the caller has submitted the submission and has determined that the GPU has finished
        /// executing it, it should call `signal_finished`. Failure to do so will incur a large runtime
        /// overhead, as the future will have to block to make sure that it is finished.
        unsafe fn build_submission(&self) -> Result<SubmitAnyBuilder, FlushError>;

        /// Flushes the future and submits to the GPU the actions that will permit this future to
        /// occur.
        ///
        /// The implementation must remember that it was flushed. If the function is called multiple
        /// times, only the first time must result in a flush.
        fn flush(&self) -> Result<(), FlushError>;

        /// Sets the future to its "complete" state, meaning that it can safely be destroyed.
        ///
        /// This must only be done if you called `build_submission()`, submitted the returned
        /// submission, and determined that it was finished.
        ///
        /// The implementation must be aware that this function can be called multiple times on the
        /// same future.
        unsafe fn signal_finished(&self);

        /// Returns the queue that triggers the event. Returns `None` if unknown or irrelevant.
        ///
        /// If this function returns `None` and `queue_change_allowed` returns `false`, then a panic
        /// is likely to occur if you use this future. This is only a problem if you implement
        /// the `GpuFuture` trait yourself for a type outside of vulkano.
        fn queue(&self) -> Option<Arc<Queue>>;

        /// Returns `true` if elements submitted after this future can be submitted to a different
        /// queue than the other returned by `queue()`.
        fn queue_change_allowed(&self) -> bool;

        /// Checks whether submitting something after this future grants access (exclusive or shared,
        /// depending on the parameter) to the given buffer on the given queue.
        ///
        /// If the access is granted, returns the pipeline stage and access flags of the latest usage
        /// of this resource, or `None` if irrelevant.
        ///
        /// > **Note**: Returning `Ok` means "access granted", while returning `Err` means
        /// > "don't know". Therefore returning `Err` is never unsafe.
        fn check_buffer_access(&self, buffer: &dyn BufferAccess, exclusive: bool, queue: &Queue)
                               -> Result<Option<(PipelineStages, AccessFlagBits)>, AccessCheckError>;

        /// Checks whether submitting something after this future grants access (exclusive or shared,
        /// depending on the parameter) to the given image on the given queue.
        ///
        /// If the access is granted, returns the pipeline stage and access flags of the latest usage
        /// of this resource, or `None` if irrelevant.
        ///
        /// Implementations must ensure that the image is in the given layout. However if the `layout`
        /// is `Undefined` then the implementation should accept any actual layout.
        ///
        /// > **Note**: Returning `Ok` means "access granted", while returning `Err` means
        /// > "don't know". Therefore returning `Err` is never unsafe.
        ///
        /// > **Note**: Keep in mind that changing the layout of an image also requires exclusive
        /// > access.
        fn check_image_access(&self, image: &dyn ImageAccess, layout: ImageLayout, exclusive: bool,
                              queue: &Queue)
                              -> Result<Option<(PipelineStages, AccessFlagBits)>, AccessCheckError>;

        /// Joins this future with another one, representing the moment when both events have happened.
        // TODO: handle errors
        fn join<F>(self, other: F) -> JoinFuture<Self, F>
            where Self: Sized,
                  F: GpuFuture
        {
            join::join(self, other)
        }

        /// Executes a command buffer after this future.
        ///
        /// > **Note**: This is just a shortcut function. The actual implementation is in the
        /// > `CommandBuffer` trait.
        #[inline]
        fn then_execute<Cb>(self, queue: Arc<Queue>, command_buffer: Cb)
                            -> Result<CommandBufferExecFuture<Self, Cb>, CommandBufferExecError>
            where Self: Sized,
                  Cb: CommandBuffer + 'static
        {
            command_buffer.execute_after(self, queue)
        }

        /// Executes a command buffer after this future, on the same queue as the future.
        ///
        /// > **Note**: This is just a shortcut function. The actual implementation is in the
        /// > `CommandBuffer` trait.
        #[inline]
        fn then_execute_same_queue<Cb>(
            self, command_buffer: Cb)
            -> Result<CommandBufferExecFuture<Self, Cb>, CommandBufferExecError>
            where Self: Sized,
                  Cb: CommandBuffer + 'static
        {
            let queue = self.queue().unwrap().clone();
            command_buffer.execute_after(self, queue)
        }

        /// Signals a semaphore after this future. Returns another future that represents the signal.
        ///
        /// Call this function when you want to execute some operations on a queue and want to see the
        /// result on another queue.
        #[inline]
        fn then_signal_semaphore(self) -> SemaphoreSignalFuture<Self>
            where Self: Sized
        {
            semaphore_signal::then_signal_semaphore(self)
        }

        /// Signals a semaphore after this future and flushes it. Returns another future that
        /// represents the moment when the semaphore is signalled.
        ///
        /// This is a just a shortcut for `then_signal_semaphore()` followed with `flush()`.
        ///
        /// When you want to execute some operations A on a queue and some operations B on another
        /// queue that need to see the results of A, it can be a good idea to submit A as soon as
        /// possible while you're preparing B.
        ///
        /// If you ran A and B on the same queue, you would have to decide between submitting A then
        /// B, or A and B simultaneously. Both approaches have their trade-offs. But if A and B are
        /// on two different queues, then you would need two submits anyway and it is always
        /// advantageous to submit A as soon as possible.
        #[inline]
        fn then_signal_semaphore_and_flush(self) -> Result<SemaphoreSignalFuture<Self>, FlushError>
            where Self: Sized
        {
            let f = self.then_signal_semaphore();
            f.flush()?;
            Ok(f)
        }

        /// Signals a fence after this future. Returns another future that represents the signal.
        ///
        /// > **Note**: More often than not you want to immediately flush the future after calling this
        /// > function. If so, consider using `then_signal_fence_and_flush`.
        #[inline]
        fn then_signal_fence(self) -> FenceSignalFuture<Self>
            where Self: Sized
        {
            fence_signal::then_signal_fence(self, FenceSignalFutureBehavior::Continue)
        }

        /// Signals a fence after this future. Returns another future that represents the signal.
        ///
        /// This is a just a shortcut for `then_signal_fence()` followed with `flush()`.
        #[inline]
        fn then_signal_fence_and_flush(self) -> Result<FenceSignalFuture<Self>, FlushError>
            where Self: Sized
        {
            let f = self.then_signal_fence();
            f.flush()?;
            Ok(f)
        }

        /// Presents a swapchain image after this future.
        ///
        /// You should only ever do this indirectly after a `SwapchainAcquireFuture` of the same image,
        /// otherwise an error will occur when flushing.
        ///
        /// > **Note**: This is just a shortcut for the `Swapchain::present()` function.
        #[inline]
        fn then_swapchain_present<W>(self, queue: Arc<Queue>, swapchain: Arc<Swapchain<W>>,
                                  image_index: usize)
                                  -> PresentFuture<Self,W>
            where Self: Sized
        {
            swapchain::present(swapchain, self, queue, image_index)
        }

        /// Same as `then_swapchain_present`, except it allows specifying a present region.
        ///
        /// > **Note**: This is just a shortcut for the `Swapchain::present_incremental()` function.
        #[inline]
        fn then_swapchain_present_incremental<W>(self, queue: Arc<Queue>, swapchain: Arc<Swapchain<W>>,
                                              image_index: usize, present_region: PresentRegion)
                                              -> PresentFuture<Self,W>
            where Self: Sized
        {
            swapchain::present_incremental(swapchain, self, queue, image_index, present_region)
        }
    }

    unsafe impl<F: ?Sized> GpuFuture for Box<F>
        where F: GpuFuture
    {
        #[inline]
        fn cleanup_finished(&mut self) {
            (**self).cleanup_finished()
        }

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

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

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

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

        #[inline]
        fn queue(&self) -> Option<Arc<Queue>> {
            (**self).queue()
        }

        #[inline]
        fn check_buffer_access(
            &self, buffer: &dyn BufferAccess, exclusive: bool, queue: &Queue)
            -> Result<Option<(PipelineStages, AccessFlagBits)>, AccessCheckError> {
            (**self).check_buffer_access(buffer, exclusive, queue)
        }

        #[inline]
        fn check_image_access(&self, image: &dyn ImageAccess, layout: ImageLayout, exclusive: bool,
                              queue: &Queue)
                              -> Result<Option<(PipelineStages, AccessFlagBits)>, AccessCheckError> {
            (**self).check_image_access(image, layout, exclusive, queue)
        }
    }

    /// Access to a resource was denied.
    #[derive(Clone, Debug, PartialEq, Eq)]
    pub enum AccessError {
        /// Exclusive access is denied.
        ExclusiveDenied,

        /// The resource is already in use, and there is no tracking of concurrent usages.
        AlreadyInUse,

        UnexpectedImageLayout {
            allowed: ImageLayout,
            requested: ImageLayout,
        },

        /// Trying to use an image without transitioning it from the "undefined" or "preinitialized"
        /// layouts first.
        ImageNotInitialized {
            /// The layout that was requested for the image.
            requested: ImageLayout,
        },

        /// Trying to use a buffer that still contains garbage data.
        BufferNotInitialized,

        /// Trying to use a swapchain image without depending on a corresponding acquire image future.
        SwapchainImageAcquireOnly,
    }

    impl error::Error for AccessError {
        #[inline]
        fn description(&self) -> &str {
            match *self {
                AccessError::ExclusiveDenied => {
                    "only shared access is allowed for this resource"
                },
                AccessError::AlreadyInUse => {
                    "the resource is already in use, and there is no tracking of concurrent usages"
                },
                AccessError::UnexpectedImageLayout { .. } => {
                    unimplemented!() // TODO: find a description
                },
                AccessError::ImageNotInitialized { .. } => {
                    "trying to use an image without transitioning it from the undefined or \
                     preinitialized layouts first"
                },
                AccessError::BufferNotInitialized => {
                    "trying to use a buffer that still contains garbage data"
                },
                AccessError::SwapchainImageAcquireOnly => {
                    "trying to use a swapchain image without depending on a corresponding acquire \
                     image future"
                },
            }
        }
    }

    impl fmt::Display for AccessError {
        #[inline]
        fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
            write!(fmt, "{}", error::Error::description(self))
        }
    }

    /// Error that can happen when checking whether we have access to a resource.
    #[derive(Clone, Debug, PartialEq, Eq)]
    pub enum AccessCheckError {
        /// Access to the resource has been denied.
        Denied(AccessError),
        /// The resource is unknown, therefore we cannot possibly answer whether we have access or not.
        Unknown,
    }

    impl error::Error for AccessCheckError {
        #[inline]
        fn description(&self) -> &str {
            match *self {
                AccessCheckError::Denied(_) => {
                    "access to the resource has been denied"
                },
                AccessCheckError::Unknown => {
                    "the resource is unknown"
                },
            }
        }
    }

    impl fmt::Display for AccessCheckError {
        #[inline]
        fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
            write!(fmt, "{}", error::Error::description(self))
        }
    }

    impl From<AccessError> for AccessCheckError {
        #[inline]
        fn from(err: AccessError) -> AccessCheckError {
            AccessCheckError::Denied(err)
        }
    }

    /// Error that can happen when creating a graphics pipeline.
    #[derive(Clone, Debug, PartialEq, Eq)]
    pub enum FlushError {
        /// Access to a resource has been denied.
        AccessError(AccessError),

        /// Not enough memory.
        OomError(OomError),

        /// The connection to the device has been lost.
        DeviceLost,

        /// The surface is no longer accessible and must be recreated.
        SurfaceLost,

        /// The surface has changed in a way that makes the swapchain unusable. You must query the
        /// surface's new properties and recreate a new swapchain if you want to continue drawing.
        OutOfDate,

        /// The flush operation needed to block, but the timeout has elapsed.
        Timeout,
    }

    impl error::Error for FlushError {
        #[inline]
        fn description(&self) -> &str {
            match *self {
                FlushError::AccessError(_) => "access to a resource has been denied",
                FlushError::OomError(_) => "not enough memory",
                FlushError::DeviceLost => "the connection to the device has been lost",
                FlushError::SurfaceLost => "the surface of this swapchain is no longer valid",
                FlushError::OutOfDate => "the swapchain needs to be recreated",
                FlushError::Timeout => "the flush operation needed to block, but the timeout has \
                                        elapsed",
            }
        }

        #[inline]
        fn cause(&self) -> Option<&dyn error::Error> {
            match *self {
                FlushError::AccessError(ref err) => Some(err),
                FlushError::OomError(ref err) => Some(err),
                _ => None,
            }
        }
    }

    impl fmt::Display for FlushError {
        #[inline]
        fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
            write!(fmt, "{}", error::Error::description(self))
        }
    }

    impl From<AccessError> for FlushError {
        #[inline]
        fn from(err: AccessError) -> FlushError {
            FlushError::AccessError(err)
        }
    }

    impl From<SubmitPresentError> for FlushError {
        #[inline]
        fn from(err: SubmitPresentError) -> FlushError {
            match err {
                SubmitPresentError::OomError(err) => FlushError::OomError(err),
                SubmitPresentError::DeviceLost => FlushError::DeviceLost,
                SubmitPresentError::SurfaceLost => FlushError::SurfaceLost,
                SubmitPresentError::OutOfDate => FlushError::OutOfDate,
            }
        }
    }

    impl From<SubmitCommandBufferError> for FlushError {
        #[inline]
        fn from(err: SubmitCommandBufferError) -> FlushError {
            match err {
                SubmitCommandBufferError::OomError(err) => FlushError::OomError(err),
                SubmitCommandBufferError::DeviceLost => FlushError::DeviceLost,
            }
        }
    }

    impl From<SubmitBindSparseError> for FlushError {
        #[inline]
        fn from(err: SubmitBindSparseError) -> FlushError {
            match err {
                SubmitBindSparseError::OomError(err) => FlushError::OomError(err),
                SubmitBindSparseError::DeviceLost => FlushError::DeviceLost,
            }
        }
    }

    impl From<FenceWaitError> for FlushError {
        #[inline]
        fn from(err: FenceWaitError) -> FlushError {
            match err {
                FenceWaitError::OomError(err) => FlushError::OomError(err),
                FenceWaitError::Timeout => FlushError::Timeout,
                FenceWaitError::DeviceLostError => FlushError::DeviceLost,
            }
        }
    }

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