use std::borrow::Cow;

use ash::vk;
use gpu_allocator::vulkan::AllocationScheme;

use crate::{
    Device,
    device::{Allocation, AllocationStrategy, DeviceObject, QueueFlags},
};

#[derive(Clone)]
pub struct BufferDesc {
    pub flags: vk::BufferCreateFlags,
    pub name: Option<Cow<'static, str>>,
    pub size: u64,
    pub usage: vk::BufferUsageFlags,
    pub queue_families: QueueFlags,

    pub mem_location: gpu_allocator::MemoryLocation,
    pub alloc_scheme: AllocationStrategy,
}

impl std::hash::Hash for BufferDesc {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.flags.hash(state);
        self.size.hash(state);
        self.usage.hash(state);
        self.queue_families.hash(state);
        self.mem_location.hash(state);
    }
}

impl std::fmt::Debug for BufferDesc {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("BufferDesc")
            .field("flags", &self.flags)
            .field("name", &self.name)
            .field("size", &self.size)
            .field("usage", &self.usage)
            .field("queue_families", &self.queue_families)
            .field("mem_location", &self.mem_location)
            .field("alloc_scheme", &self.alloc_scheme)
            .finish()
    }
}

impl Eq for BufferDesc {}
impl PartialEq for BufferDesc {
    fn eq(&self, other: &Self) -> bool {
        self.flags == other.flags
            // for hashmaps, `Eq` may be more strict than `Hash`
            && self.name == other.name
            && self.size == other.size
            && self.usage == other.usage
            && self.queue_families == other.queue_families
            && self.mem_location == other.mem_location
    }
}

impl Default for BufferDesc {
    fn default() -> Self {
        Self {
            flags: Default::default(),
            name: Default::default(),
            size: Default::default(),
            usage: Default::default(),
            queue_families: QueueFlags::empty(),
            mem_location: gpu_allocator::MemoryLocation::Unknown,
            alloc_scheme: AllocationStrategy::default(),
        }
    }
}

#[derive(Debug)]
pub struct Buffer {
    buffer: DeviceObject<vk::Buffer>,
    pub desc: BufferDesc,
    alloc: Allocation,
}

impl Eq for Buffer {}
impl PartialEq for Buffer {
    fn eq(&self, other: &Self) -> bool {
        *self.buffer == *other.buffer
    }
}

impl Buffer {
    pub fn new(device: Device, desc: BufferDesc) -> crate::Result<Self> {
        let (buffer, requirements) = Self::new_raw(device.clone(), &desc)?;

        let alloc =
            device
                .alloc2
                .lock()
                .allocate(&gpu_allocator::vulkan::AllocationCreateDesc {
                    name: desc.name.as_deref().unwrap_or_default(),
                    requirements,
                    location: desc.mem_location,
                    linear: true,
                    allocation_scheme: match desc.alloc_scheme {
                        AllocationStrategy::AllocatorManaged => {
                            AllocationScheme::GpuAllocatorManaged
                        }
                        AllocationStrategy::Dedicated => AllocationScheme::DedicatedBuffer(buffer),
                    },
                })?;

        unsafe {
            device
                .raw
                .bind_buffer_memory(buffer, alloc.memory(), alloc.offset())?;
        }

        Ok(Self {
            buffer: DeviceObject::new_debug_named(device.clone(), buffer, desc.name.clone()),
            desc,
            alloc: Allocation::Owned(DeviceObject::new(device, alloc)),
        })
    }

    fn new_raw(
        device: Device,
        desc: &BufferDesc,
    ) -> crate::Result<(vk::Buffer, vk::MemoryRequirements)> {
        let queue_families = device.queues.family_indices(desc.queue_families);

        let sharing_mode = if queue_families.len() > 1 {
            vk::SharingMode::CONCURRENT
        } else {
            vk::SharingMode::EXCLUSIVE
        };
        let create_info = vk::BufferCreateInfo::default()
            .size(desc.size)
            .usage(desc.usage)
            .queue_family_indices(&queue_families)
            .sharing_mode(sharing_mode);

        let buffer = unsafe { device.dev().create_buffer(&create_info, None)? };
        let mem_reqs = unsafe { device.dev().get_buffer_memory_requirements(buffer) };

        Ok((buffer, mem_reqs))
    }

    pub fn map(&mut self) -> Option<&[u8]> {
        if let Some(alloc) = self.alloc.allocation() {
            alloc
                .mapped_slice()
                .map(|slice| &slice[..self.desc.size as usize])
        } else {
            None
        }
    }

    pub fn map_mut(&mut self) -> Option<&mut [u8]> {
        if let Some(alloc) = self.alloc.allocation_mut() {
            alloc
                .mapped_slice_mut()
                .map(|slice| &mut slice[..self.desc.size as usize])
        } else {
            None
        }
    }

    pub fn raw(&self) -> vk::Buffer {
        *self.buffer
    }
    pub fn len(&self) -> u64 {
        self.desc.size
    }
}