// 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 device::DeviceOwned;
use instance::MemoryType;
use memory::DedicatedAlloc;
use memory::DeviceMemory;
use memory::DeviceMemoryAllocError;
use memory::MappedDeviceMemory;
use memory::MemoryRequirements;

pub use self::host_visible::StdHostVisibleMemoryTypePool;
pub use self::host_visible::StdHostVisibleMemoryTypePoolAlloc;
pub use self::non_host_visible::StdNonHostVisibleMemoryTypePool;
pub use self::non_host_visible::StdNonHostVisibleMemoryTypePoolAlloc;
pub use self::pool::StdMemoryPool;
pub use self::pool::StdMemoryPoolAlloc;

mod host_visible;
mod non_host_visible;
mod pool;

/// Pool of GPU-visible memory that can be allocated from.
pub unsafe trait MemoryPool: DeviceOwned {
    /// Object that represents a single allocation. Its destructor should free the chunk.
    type Alloc: MemoryPoolAlloc;

    /// Allocates memory from the pool.
    ///
    /// # Safety
    ///
    /// Implementation safety:
    ///
    /// - The returned object must match the requirements.
    /// - When a linear object is allocated next to an optimal object, it is mandatory that
    ///   the boundary is aligned to the value of the `buffer_image_granularity` limit.
    ///
    /// Note that it is not unsafe to *call* this function, but it is unsafe to bind the memory
    /// returned by this function to a resource.
    ///
    /// # Panic
    ///
    /// - Panics if `memory_type` doesn't belong to the same physical device as the device which
    ///   was used to create this pool.
    /// - Panics if the memory type is not host-visible and `map` is `MappingRequirement::Map`.
    /// - Panics if `size` is 0.
    /// - Panics if `alignment` is 0.
    ///
    fn alloc_generic(&self, ty: MemoryType, size: usize, alignment: usize, layout: AllocLayout,
                     map: MappingRequirement)
                     -> Result<Self::Alloc, DeviceMemoryAllocError>;

    /// Chooses a memory type and allocates memory from it.
    ///
    /// Contrary to `alloc_generic`, this function may allocate a whole new block of memory
    /// dedicated to a resource based on `requirements.prefer_dedicated`.
    ///
    /// `filter` can be used to restrict the memory types and to indicate which are preferred.
    /// If `map` is `MappingRequirement::Map`, then non-host-visible memory types will
    /// automatically be filtered out.
    ///
    /// # Safety
    ///
    /// Implementation safety:
    ///
    /// - The returned object must match the requirements.
    /// - When a linear object is allocated next to an optimal object, it is mandatory that
    ///   the boundary is aligned to the value of the `buffer_image_granularity` limit.
    /// - If `dedicated` is not `None`, the returned memory must either not be dedicated or be
    ///   dedicated to the resource that was passed.
    ///
    /// Note that it is not unsafe to *call* this function, but it is unsafe to bind the memory
    /// returned by this function to a resource.
    ///
    /// # Panic
    ///
    /// - Panics if no memory type could be found, which can happen if `filter` is too restrictive.
    // TODO: ^ is this a good idea?
    /// - Panics if `size` is 0.
    /// - Panics if `alignment` is 0.
    ///
    fn alloc_from_requirements<F>(
        &self, requirements: &MemoryRequirements, layout: AllocLayout, map: MappingRequirement,
        dedicated: DedicatedAlloc, mut filter: F)
        -> Result<PotentialDedicatedAllocation<Self::Alloc>, DeviceMemoryAllocError>
        where F: FnMut(MemoryType) -> AllocFromRequirementsFilter
    {
        // Choose a suitable memory type.
        let mem_ty = {
            let mut filter = |ty: MemoryType| {
                if map == MappingRequirement::Map && !ty.is_host_visible() {
                    return AllocFromRequirementsFilter::Forbidden;
                }
                filter(ty)
            };
            let first_loop = self.device()
                .physical_device()
                .memory_types()
                .map(|t| (t, AllocFromRequirementsFilter::Preferred));
            let second_loop = self.device()
                .physical_device()
                .memory_types()
                .map(|t| (t, AllocFromRequirementsFilter::Allowed));
            first_loop
                .chain(second_loop)
                .filter(|&(t, _)| (requirements.memory_type_bits & (1 << t.id())) != 0)
                .filter(|&(t, rq)| filter(t) == rq)
                .next()
                .expect("Couldn't find a memory type to allocate from")
                .0
        };

        // Redirect to `self.alloc_generic` if we don't perform a dedicated allocation.
        if !requirements.prefer_dedicated ||
            !self.device().loaded_extensions().khr_dedicated_allocation
        {
            let alloc = self.alloc_generic(mem_ty,
                                           requirements.size,
                                           requirements.alignment,
                                           layout,
                                           map)?;
            return Ok(alloc.into());
        }
        if let DedicatedAlloc::None = dedicated {
            let alloc = self.alloc_generic(mem_ty,
                                           requirements.size,
                                           requirements.alignment,
                                           layout,
                                           map)?;
            return Ok(alloc.into());
        }

        // If we reach here, then we perform a dedicated alloc.
        match map {
            MappingRequirement::Map => {
                let mem = DeviceMemory::dedicated_alloc_and_map(self.device().clone(),
                                                                mem_ty,
                                                                requirements.size,
                                                                dedicated)?;
                Ok(PotentialDedicatedAllocation::DedicatedMapped(mem))
            },
            MappingRequirement::DoNotMap => {
                let mem = DeviceMemory::dedicated_alloc(self.device().clone(),
                                                        mem_ty,
                                                        requirements.size,
                                                        dedicated)?;
                Ok(PotentialDedicatedAllocation::Dedicated(mem))
            },
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum AllocFromRequirementsFilter {
    Preferred,
    Allowed,
    Forbidden,
}

/// Object that represents a single allocation. Its destructor should free the chunk.
pub unsafe trait MemoryPoolAlloc {
    /// Returns the memory object from which this is allocated. Returns `None` if the memory is
    /// not mapped.
    fn mapped_memory(&self) -> Option<&MappedDeviceMemory>;

    /// Returns the memory object from which this is allocated.
    fn memory(&self) -> &DeviceMemory;

    /// Returns the offset at the start of the memory where the first byte of this allocation
    /// resides.
    fn offset(&self) -> usize;
}

/// Whether an allocation should map the memory or not.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum MappingRequirement {
    /// Should map.
    Map,
    /// Shouldn't map.
    DoNotMap,
}

/// Layout of the object being allocated.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum AllocLayout {
    /// The object has a linear layout.
    Linear,
    /// The object has an optimal layout.
    Optimal,
}

/// Enumeration that can contain either a generic allocation coming from a pool, or a dedicated
/// allocation for one specific resource.
#[derive(Debug)]
pub enum PotentialDedicatedAllocation<A> {
    Generic(A),
    Dedicated(DeviceMemory),
    DedicatedMapped(MappedDeviceMemory),
}

unsafe impl<A> MemoryPoolAlloc for PotentialDedicatedAllocation<A>
    where A: MemoryPoolAlloc
{
    #[inline]
    fn mapped_memory(&self) -> Option<&MappedDeviceMemory> {
        match *self {
            PotentialDedicatedAllocation::Generic(ref alloc) => alloc.mapped_memory(),
            PotentialDedicatedAllocation::Dedicated(_) => None,
            PotentialDedicatedAllocation::DedicatedMapped(ref mem) => Some(mem),
        }
    }

    #[inline]
    fn memory(&self) -> &DeviceMemory {
        match *self {
            PotentialDedicatedAllocation::Generic(ref alloc) => alloc.memory(),
            PotentialDedicatedAllocation::Dedicated(ref mem) => mem,
            PotentialDedicatedAllocation::DedicatedMapped(ref mem) => mem.as_ref(),
        }
    }

    #[inline]
    fn offset(&self) -> usize {
        match *self {
            PotentialDedicatedAllocation::Generic(ref alloc) => alloc.offset(),
            PotentialDedicatedAllocation::Dedicated(_) => 0,
            PotentialDedicatedAllocation::DedicatedMapped(_) => 0,
        }
    }
}

impl<A> From<A> for PotentialDedicatedAllocation<A> {
    #[inline]
    fn from(alloc: A) -> PotentialDedicatedAllocation<A> {
        PotentialDedicatedAllocation::Generic(alloc)
    }
}
