// 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,
        }
    }
}