/*
Crafter®.Graphics
Copyright (C) 2026 Catcrafts®
catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 3.0 as published by the Free Software Foundation;

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

module;

#ifndef CRAFTER_GRAPHICS_WINDOW_DOM
#include "vulkan/vulkan.h"

#endif // !CRAFTER_GRAPHICS_WINDOW_DOM
export module Crafter.Graphics:VulkanBuffer;
#ifndef CRAFTER_GRAPHICS_WINDOW_DOM
import std;
import :Device;

namespace Crafter {
    // Round a host-write flush range outward to nonCoherentAtomSize boundaries —
    // the alignment vkFlushMappedMemoryRanges demands for a sub-buffer range
    // (whole-buffer VK_WHOLE_SIZE calls sidestep it). `atom` is
    // VkPhysicalDeviceLimits::nonCoherentAtomSize (a power of two ≥ 1) and
    // `mappingSize` is the byte size the memory was mapped with (the allocation
    // size). The start rounds down and the end rounds up to atom multiples; the
    // end is then clamped to `mappingSize`. Clamping is what keeps the range
    // valid even when `mappingSize` itself is not atom-aligned: the spec permits
    // a non-atom-multiple size only when offset+size equals the mapping size, and
    // the clamp lands exactly on that exception. Pure math, so it is unit-tested
    // without a device.
    export struct MappedFlushRange { VkDeviceSize offset; VkDeviceSize size; };
    export constexpr MappedFlushRange AlignMappedFlushRange(
            VkDeviceSize offset, VkDeviceSize bytes,
            VkDeviceSize atom, VkDeviceSize mappingSize) {
        VkDeviceSize begin = (offset / atom) * atom;
        VkDeviceSize end   = ((offset + bytes + atom - 1) / atom) * atom;
        if (end > mappingSize) end = mappingSize;
        return { begin, end - begin };
    }

    export class VulkanBufferBase {
        public:
        VkDeviceAddress address;
        std::uint32_t size;
        // Byte size the memory was mapped with — equal to the allocation's
        // VkMemoryRequirements::size, which is ≥ `size` and what ranged flushes
        // clamp their upper bound to. Only meaningful for mapped buffers.
        VkDeviceSize mappedSize = 0;
        VkBuffer buffer = VK_NULL_HANDLE;
        VkDeviceMemory memory;
        // Property flags of the memory type actually chosen by GetMemoryType —
        // not the requested flags. GetMemoryType may land a request without the
        // COHERENT bit on a coherent type (and vice versa), so the flush/
        // invalidate paths gate on this recorded value, never on the request.
        VkMemoryPropertyFlags memoryPropertyFlagsChosen = 0;
        // Byte capacity the buffer was created with, and the usage flags it was
        // created with. Resize reuses the allocation in place when a new
        // request still fits within `capacity` and these immutable-at-create
        // properties match, avoiding a destroy+reallocate.
        std::uint32_t capacity = 0;
        VkBufferUsageFlags2 usageFlagsCreated = 0;
    };

    export template<typename T>
    class VulkanBufferMapped {
        public:
        T* value;
    };
    export class VulkanBufferMappedEmpty {};
    template<typename T, bool Mapped>
    using VulkanBufferMappedConditional =
        std::conditional_t<
            Mapped,
            VulkanBufferMapped<T>,
            VulkanBufferMappedEmpty
        >;

    export template <typename T, bool Mapped> 
    class VulkanBuffer : public VulkanBufferBase, public VulkanBufferMappedConditional<T, Mapped> {
    public:
        VulkanBuffer() = default;
        // `preferredPropertyFlags` are best-effort: the allocation prefers a
        // memory type satisfying them on top of `memoryPropertyFlags`, but
        // falls back to the required flags alone rather than failing. Use it
        // for perf hints (e.g. DEVICE_LOCAL on a mapped buffer) that aren't
        // available on every device — see Device::GetMemoryType.
        void Create(VkBufferUsageFlags2 usageFlags, VkMemoryPropertyFlags memoryPropertyFlags, std::uint32_t count, VkMemoryPropertyFlags preferredPropertyFlags = 0) {
            size = count * sizeof(T);
            capacity = size;
            usageFlagsCreated = usageFlags;

            // Carry usage in the maintenance5 flags2 chain so 64-bit bits
            // (e.g. VK_BUFFER_USAGE_2_MEMORY_DECOMPRESSION_BIT_EXT, bit 35)
            // are not truncated.
            VkBufferUsageFlags2CreateInfo usageFlags2 {
                .sType = VK_STRUCTURE_TYPE_BUFFER_USAGE_FLAGS_2_CREATE_INFO,
                .usage = usageFlags,
            };
            VkBufferCreateInfo bufferCreateInfo {};
			bufferCreateInfo.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;
            bufferCreateInfo.pNext = &usageFlags2;
            bufferCreateInfo.usage = 0;
			bufferCreateInfo.size = sizeof(T)*count;
            Device::CheckVkResult(vkCreateBuffer(Device::device, &bufferCreateInfo, nullptr, &buffer));
        
            VkMemoryRequirements memReqs;
            vkGetBufferMemoryRequirements(Device::device, buffer, &memReqs);
            std::uint32_t memoryTypeIndex = Device::GetMemoryType(memReqs.memoryTypeBits, memoryPropertyFlags, preferredPropertyFlags);
            memoryPropertyFlagsChosen = Device::memoryProperties.memoryTypes[memoryTypeIndex].propertyFlags;
            VkMemoryAllocateInfo memAlloc {
                .sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO,
                .allocationSize = memReqs.size,
                .memoryTypeIndex = memoryTypeIndex
            };

            VkMemoryAllocateFlagsInfoKHR allocFlagsInfo {
                .sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_FLAGS_INFO_KHR,
                .flags = VK_MEMORY_ALLOCATE_DEVICE_ADDRESS_BIT_KHR,
            };
            memAlloc.pNext = &allocFlagsInfo;
            Device::CheckVkResult(vkAllocateMemory(Device::device, &memAlloc, nullptr, &memory));
        
            Device::CheckVkResult(vkBindBufferMemory(Device::device, buffer, memory, 0));

            VkBufferDeviceAddressInfo addressInfo = {
                .sType = VK_STRUCTURE_TYPE_BUFFER_DEVICE_ADDRESS_INFO,
                .buffer = buffer
            };
            address = vkGetBufferDeviceAddress(Device::device, &addressInfo);

            if constexpr(Mapped) {
                mappedSize = memReqs.size;
                Device::CheckVkResult(vkMapMemory(Device::device, memory, 0, memReqs.size, 0, reinterpret_cast<void**>(&(VulkanBufferMappedConditional<T, true>::value))));
            }
        }

        void Clear() {
            if constexpr(Mapped) {
                vkUnmapMemory(Device::device, memory);
            }
            vkDestroyBuffer(Device::device, buffer, nullptr);
            vkFreeMemory(Device::device, memory, nullptr);
            buffer = VK_NULL_HANDLE;
        }

        // Like Clear(), but hands the destroy+free to Device's fence-keyed
        // deletion queue instead of doing it immediately. Use when the buffer
        // may still be read by an in-flight frame's GPU work — destroying it
        // now would be a use-after-free, since frames are pipelined up to
        // framesInFlight deep (issue #101). The handle is nulled immediately so
        // this VulkanBuffer no longer owns it; vkFreeMemory (deferred) implicitly
        // unmaps mapped memory, so no explicit vkUnmapMemory is needed here.
        void DeferredClear() {
            Device::EnqueueDeletion(buffer, memory);
            buffer = VK_NULL_HANDLE;
        }

        void Resize(VkBufferUsageFlags2 usageFlags, VkMemoryPropertyFlags memoryPropertyFlags, std::uint32_t count, VkMemoryPropertyFlags preferredPropertyFlags = 0) {
            // Reuse the existing allocation in place when the request still fits
            // and the fixed-at-create properties match: usage flags are
            // immutable after creation, and the memory type already chosen must
            // still satisfy the required property flags. preferredPropertyFlags
            // is a best-effort perf hint and does not affect correctness, so it
            // is intentionally not part of the guard. The buffer handle (and its
            // device address / mapped pointer) is preserved, only `size` shrinks
            // to the new logical extent.
            std::uint32_t requestedSize = count * sizeof(T);
            if(buffer != VK_NULL_HANDLE
                && requestedSize <= capacity
                && usageFlags == usageFlagsCreated
                && (memoryPropertyFlagsChosen & memoryPropertyFlags) == memoryPropertyFlags) {
                size = requestedSize;
                return;
            }
            // Defer the old allocation's destruction: an in-flight frame may
            // still reference it (the #63 hazard, no longer masked by a
            // per-frame wait-idle since #40). DeferredClear nulls the handle,
            // so the Create below starts from a clean slate.
            if(buffer != VK_NULL_HANDLE) {
               DeferredClear();
            }
            Create(usageFlags, memoryPropertyFlags, count, preferredPropertyFlags);
        }

        void Copy(VkCommandBuffer cmd, VulkanBuffer& dst) {
            VkBufferCopy copyRegion = {
                .srcOffset = 0,
                .dstOffset = 0,
                .size = size
            };

            vkCmdCopyBuffer(
                cmd,
                buffer,
                dst.buffer,
                1,
                &copyRegion
            );
        }

        void Copy(VkCommandBuffer cmd, VulkanBuffer& dst, VkAccessFlags srcAccessMask, VkAccessFlags dstAccessMask, VkPipelineStageFlags srcStageMask, VkPipelineStageFlags dstStageMask) {
            Copy(cmd, dst);

            VkBufferMemoryBarrier barrier = {
                .sType = VK_STRUCTURE_TYPE_BUFFER_MEMORY_BARRIER,
                .srcAccessMask = srcAccessMask,
                .dstAccessMask = dstAccessMask,
                .srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED,
                .dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED,
                .buffer = buffer,
                .offset = 0,
                .size = VK_WHOLE_SIZE
            };

            vkCmdPipelineBarrier(
                cmd,
                srcStageMask,
                dstStageMask,
                0,
                0, NULL,
                1, &barrier,
                0, NULL
            );
        }

        void FlushDevice() requires(Mapped) {
            // Coherent memory needs no explicit flush — host writes are
            // automatically visible to the device.
            if (memoryPropertyFlagsChosen & VK_MEMORY_PROPERTY_HOST_COHERENT_BIT) {
                return;
            }
            VkMappedMemoryRange range = {
                .sType  = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE,
                .memory = memory,
                .offset = 0,
                .size   = VK_WHOLE_SIZE
            };
            vkFlushMappedMemoryRanges(Device::device, 1, &range);
        }

        // Flush only the host writes in [offset, offset+bytes) to the device,
        // instead of the whole buffer. Use after touching a small sub-range
        // (e.g. one descriptor in a multi-KB descriptor heap) so cache
        // maintenance scales with the bytes actually written. The range is
        // rounded outward to nonCoherentAtomSize as the Vulkan spec requires.
        // No-op on coherent memory, same gate as the whole-buffer FlushDevice().
        void FlushDevice(VkDeviceSize offset, VkDeviceSize bytes) requires(Mapped) {
            if (memoryPropertyFlagsChosen & VK_MEMORY_PROPERTY_HOST_COHERENT_BIT) {
                return;
            }
            MappedFlushRange r = AlignMappedFlushRange(
                offset, bytes, Device::nonCoherentAtomSize, mappedSize);
            VkMappedMemoryRange range = {
                .sType  = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE,
                .memory = memory,
                .offset = r.offset,
                .size   = r.size
            };
            vkFlushMappedMemoryRanges(Device::device, 1, &range);
        }

        void FlushDevice(VkCommandBuffer cmd, VkAccessFlags dstAccessMask, VkPipelineStageFlags dstStageMask) requires(Mapped) {
            FlushDevice();
            VkBufferMemoryBarrier barrier = {
                .sType = VK_STRUCTURE_TYPE_BUFFER_MEMORY_BARRIER,
                .srcAccessMask = VK_ACCESS_HOST_WRITE_BIT,
                .dstAccessMask = dstAccessMask,
                .srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED,
                .dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED,
                .buffer = buffer,
                .offset = 0,
                .size = VK_WHOLE_SIZE
            };

            vkCmdPipelineBarrier(
                cmd,
                VK_PIPELINE_STAGE_HOST_BIT,
                dstStageMask,
                0,
                0, NULL,
                1, &barrier,
                0, NULL
            );
        }

        void FlushHost() requires(Mapped) {
            // Coherent memory needs no explicit invalidate — device writes are
            // automatically visible to the host.
            if (memoryPropertyFlagsChosen & VK_MEMORY_PROPERTY_HOST_COHERENT_BIT) {
                return;
            }
            VkMappedMemoryRange range = {
                .sType  = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE,
                .memory = memory,
                .offset = 0,
                .size   = VK_WHOLE_SIZE
            };
            vkInvalidateMappedMemoryRanges(Device::device, 1, &range);
        }
    
        VulkanBuffer(VulkanBuffer&& other) {
            buffer = other.buffer;
            memory = other.memory;
            size = other.size;
            mappedSize = other.mappedSize;
            capacity = other.capacity;
            usageFlagsCreated = other.usageFlagsCreated;
            memoryPropertyFlagsChosen = other.memoryPropertyFlagsChosen;
            other.buffer = VK_NULL_HANDLE;
            address = other.address;
            if constexpr(Mapped) {
                VulkanBufferMappedConditional<T, true>::value = other.VulkanBufferMappedConditional<T, true>::value;
            }
        };

        ~VulkanBuffer() {
            if(buffer != VK_NULL_HANDLE) {
               Clear();
            }
        }

        VulkanBuffer(VulkanBuffer&) = delete;
        VulkanBuffer& operator=(const VulkanBuffer&) = delete;
    };
}
#endif // !CRAFTER_GRAPHICS_WINDOW_DOM