use std::{num::NonZeroU32, ops::Range};

#[cfg(feature = "trace")]
use crate::device::trace::Command as TraceCommand;
use crate::{
    align_to,
    command::CommandBuffer,
    get_lowest_common_denom,
    hub::{Global, GlobalIdentityHandlerFactory, HalApi, Token},
    id::{BufferId, CommandEncoderId, DeviceId, TextureId},
    init_tracker::MemoryInitKind,
    track::TextureSelector,
};

use hal::CommandEncoder as _;
use thiserror::Error;
use wgt::{
    BufferAddress, BufferSize, BufferUsages, ImageSubresourceRange, TextureAspect, TextureUsages,
};

/// Error encountered while attempting a clear.
#[derive(Clone, Debug, Error)]
pub enum ClearError {
    #[error("to use clear_buffer/texture the CLEAR_COMMANDS feature needs to be enabled")]
    MissingClearCommandsFeature,
    #[error("command encoder {0:?} is invalid")]
    InvalidCommandEncoder(CommandEncoderId),
    #[error("device {0:?} is invalid")]
    InvalidDevice(DeviceId),
    #[error("buffer {0:?} is invalid or destroyed")]
    InvalidBuffer(BufferId),
    #[error("texture {0:?} is invalid or destroyed")]
    InvalidTexture(TextureId),
    #[error("buffer clear size {0:?} is not a multiple of `COPY_BUFFER_ALIGNMENT`")]
    UnalignedFillSize(BufferSize),
    #[error("buffer offset {0:?} is not a multiple of `COPY_BUFFER_ALIGNMENT`")]
    UnalignedBufferOffset(BufferAddress),
    #[error("clear of {start_offset}..{end_offset} would end up overrunning the bounds of the buffer of size {buffer_size}")]
    BufferOverrun {
        start_offset: BufferAddress,
        end_offset: BufferAddress,
        buffer_size: BufferAddress,
    },
    #[error("destination buffer/texture is missing the `COPY_DST` usage flag")]
    MissingCopyDstUsageFlag(Option<BufferId>, Option<TextureId>),
    #[error("texture lacks the aspects that were specified in the image subresource range. Texture with format {texture_format:?}, specified was {subresource_range_aspects:?}")]
    MissingTextureAspect {
        texture_format: wgt::TextureFormat,
        subresource_range_aspects: TextureAspect,
    },
    #[error("Depth/Stencil formats are not supported for clearing")]
    DepthStencilFormatNotSupported,
    #[error("Multisampled textures are not supported for clearing")]
    MultisampledTextureUnsupported,
    #[error("image subresource level range is outside of the texture's level range. texture range is {texture_level_range:?},  \
whereas subesource range specified start {subresource_base_mip_level} and count {subresource_mip_level_count:?}")]
    InvalidTextureLevelRange {
        texture_level_range: Range<u32>,
        subresource_base_mip_level: u32,
        subresource_mip_level_count: Option<NonZeroU32>,
    },
    #[error("image subresource layer range is outside of the texture's layer range. texture range is {texture_layer_range:?},  \
whereas subesource range specified start {subresource_base_array_layer} and count {subresource_array_layer_count:?}")]
    InvalidTextureLayerRange {
        texture_layer_range: Range<u32>,
        subresource_base_array_layer: u32,
        subresource_array_layer_count: Option<NonZeroU32>,
    },
}

impl<G: GlobalIdentityHandlerFactory> Global<G> {
    pub fn command_encoder_clear_buffer<A: HalApi>(
        &self,
        command_encoder_id: CommandEncoderId,
        dst: BufferId,
        offset: BufferAddress,
        size: Option<BufferSize>,
    ) -> Result<(), ClearError> {
        profiling::scope!("CommandEncoder::fill_buffer");

        let hub = A::hub(self);
        let mut token = Token::root();
        let (mut cmd_buf_guard, mut token) = hub.command_buffers.write(&mut token);
        let cmd_buf = CommandBuffer::get_encoder_mut(&mut *cmd_buf_guard, command_encoder_id)
            .map_err(|_| ClearError::InvalidCommandEncoder(command_encoder_id))?;
        let (buffer_guard, _) = hub.buffers.read(&mut token);

        #[cfg(feature = "trace")]
        if let Some(ref mut list) = cmd_buf.commands {
            list.push(TraceCommand::ClearBuffer { dst, offset, size });
        }

        let (dst_buffer, dst_pending) = cmd_buf
            .trackers
            .buffers
            .use_replace(&*buffer_guard, dst, (), hal::BufferUses::COPY_DST)
            .map_err(ClearError::InvalidBuffer)?;
        let dst_raw = dst_buffer
            .raw
            .as_ref()
            .ok_or(ClearError::InvalidBuffer(dst))?;
        if !dst_buffer.usage.contains(BufferUsages::COPY_DST) {
            return Err(ClearError::MissingCopyDstUsageFlag(Some(dst), None));
        }

        // Check if offset & size are valid.
        if offset % wgt::COPY_BUFFER_ALIGNMENT != 0 {
            return Err(ClearError::UnalignedBufferOffset(offset));
        }
        if let Some(size) = size {
            if size.get() % wgt::COPY_BUFFER_ALIGNMENT != 0 {
                return Err(ClearError::UnalignedFillSize(size));
            }
            let destination_end_offset = offset + size.get();
            if destination_end_offset > dst_buffer.size {
                return Err(ClearError::BufferOverrun {
                    start_offset: offset,
                    end_offset: destination_end_offset,
                    buffer_size: dst_buffer.size,
                });
            }
        }

        let end = match size {
            Some(size) => offset + size.get(),
            None => dst_buffer.size,
        };
        if offset == end {
            log::trace!("Ignoring fill_buffer of size 0");
            return Ok(());
        }

        // Mark dest as initialized.
        cmd_buf
            .buffer_memory_init_actions
            .extend(dst_buffer.initialization_status.create_action(
                dst,
                offset..end,
                MemoryInitKind::ImplicitlyInitialized,
            ));
        // actual hal barrier & operation
        let dst_barrier = dst_pending.map(|pending| pending.into_hal(dst_buffer));
        let cmd_buf_raw = cmd_buf.encoder.open();
        unsafe {
            cmd_buf_raw.transition_buffers(dst_barrier);
            cmd_buf_raw.clear_buffer(dst_raw, offset..end);
        }
        Ok(())
    }

    pub fn command_encoder_clear_texture<A: HalApi>(
        &self,
        command_encoder_id: CommandEncoderId,
        dst: TextureId,
        subresource_range: &ImageSubresourceRange,
    ) -> Result<(), ClearError> {
        profiling::scope!("CommandEncoder::clear_texture");

        let hub = A::hub(self);
        let mut token = Token::root();
        let (device_guard, mut token) = hub.devices.write(&mut token);
        let (mut cmd_buf_guard, mut token) = hub.command_buffers.write(&mut token);
        let cmd_buf = CommandBuffer::get_encoder_mut(&mut *cmd_buf_guard, command_encoder_id)
            .map_err(|_| ClearError::InvalidCommandEncoder(command_encoder_id))?;
        let (_, mut token) = hub.buffers.read(&mut token); // skip token
        let (texture_guard, _) = hub.textures.read(&mut token);

        #[cfg(feature = "trace")]
        if let Some(ref mut list) = cmd_buf.commands {
            list.push(TraceCommand::ClearTexture {
                dst,
                subresource_range: subresource_range.clone(),
            });
        }

        if !cmd_buf.support_clear_buffer_texture {
            return Err(ClearError::MissingClearCommandsFeature);
        }

        let dst_texture = texture_guard
            .get(dst)
            .map_err(|_| ClearError::InvalidTexture(dst))?;

        // Check if subresource aspects are valid.
        let requested_aspects = hal::FormatAspects::from(subresource_range.aspect);
        let clear_aspects = hal::FormatAspects::from(dst_texture.desc.format) & requested_aspects;
        if clear_aspects.is_empty() {
            return Err(ClearError::MissingTextureAspect {
                texture_format: dst_texture.desc.format,
                subresource_range_aspects: subresource_range.aspect,
            });
        };

        // Check if texture is supported for clearing
        if dst_texture.desc.format.describe().sample_type == wgt::TextureSampleType::Depth {
            return Err(ClearError::DepthStencilFormatNotSupported);
        }
        if dst_texture.desc.sample_count > 1 {
            return Err(ClearError::MultisampledTextureUnsupported);
        }

        // Check if subresource level range is valid
        let subresource_level_end = match subresource_range.mip_level_count {
            Some(count) => subresource_range.base_mip_level + count.get(),
            None => dst_texture.full_range.levels.end,
        };
        if dst_texture.full_range.levels.start > subresource_range.base_mip_level
            || dst_texture.full_range.levels.end < subresource_level_end
        {
            return Err(ClearError::InvalidTextureLevelRange {
                texture_level_range: dst_texture.full_range.levels.clone(),
                subresource_base_mip_level: subresource_range.base_mip_level,
                subresource_mip_level_count: subresource_range.mip_level_count,
            });
        }
        // Check if subresource layer range is valid
        let subresource_layer_end = match subresource_range.array_layer_count {
            Some(count) => subresource_range.base_array_layer + count.get(),
            None => dst_texture.full_range.layers.end,
        };
        if dst_texture.full_range.layers.start > subresource_range.base_array_layer
            || dst_texture.full_range.layers.end < subresource_layer_end
        {
            return Err(ClearError::InvalidTextureLayerRange {
                texture_layer_range: dst_texture.full_range.layers.clone(),
                subresource_base_array_layer: subresource_range.base_array_layer,
                subresource_array_layer_count: subresource_range.array_layer_count,
            });
        }

        // query from tracker with usage (and check usage)
        let (dst_texture, dst_pending) = cmd_buf
            .trackers
            .textures
            .use_replace(
                &*texture_guard,
                dst,
                TextureSelector {
                    levels: subresource_range.base_mip_level..subresource_level_end,
                    layers: subresource_range.base_array_layer..subresource_layer_end,
                },
                hal::TextureUses::COPY_DST,
            )
            .map_err(ClearError::InvalidTexture)?;
        let dst_raw = dst_texture
            .inner
            .as_raw()
            .ok_or(ClearError::InvalidTexture(dst))?;
        if !dst_texture.desc.usage.contains(TextureUsages::COPY_DST) {
            return Err(ClearError::MissingCopyDstUsageFlag(None, Some(dst)));
        }

        // actual hal barrier & operation
        let dst_barrier = dst_pending.map(|pending| pending.into_hal(dst_texture));
        let encoder = cmd_buf.encoder.open();
        let device = &device_guard[cmd_buf.device_id.value];

        let mut zero_buffer_copy_regions = Vec::new();
        collect_zero_buffer_copies_for_clear_texture(
            &dst_texture.desc,
            device.alignments.buffer_copy_pitch.get() as u32,
            subresource_range.base_mip_level..subresource_level_end,
            subresource_range.base_array_layer..subresource_layer_end,
            &mut zero_buffer_copy_regions,
        );
        unsafe {
            encoder.transition_textures(dst_barrier);
            if !zero_buffer_copy_regions.is_empty() {
                encoder.copy_buffer_to_texture(
                    &device.zero_buffer,
                    dst_raw,
                    zero_buffer_copy_regions.into_iter(),
                );
            }
        }
        Ok(())
    }
}

pub(crate) fn collect_zero_buffer_copies_for_clear_texture(
    texture_desc: &wgt::TextureDescriptor<()>,
    buffer_copy_pitch: u32,
    mip_range: Range<u32>,
    layer_range: Range<u32>,
    out_copy_regions: &mut Vec<hal::BufferTextureCopy>, // TODO: Something better than Vec
) {
    let format_desc = texture_desc.format.describe();

    let bytes_per_row_alignment =
        get_lowest_common_denom(buffer_copy_pitch, format_desc.block_size as u32);

    for mip_level in mip_range {
        let mut mip_size = texture_desc.mip_level_size(mip_level).unwrap();
        // Round to multiple of block size
        mip_size.width = align_to(mip_size.width, format_desc.block_dimensions.0 as u32);
        mip_size.height = align_to(mip_size.height, format_desc.block_dimensions.1 as u32);

        let bytes_per_row = align_to(
            mip_size.width / format_desc.block_dimensions.0 as u32 * format_desc.block_size as u32,
            bytes_per_row_alignment,
        );

        let max_rows_per_copy = crate::device::ZERO_BUFFER_SIZE as u32 / bytes_per_row;
        // round down to a multiple of rows needed by the texture format
        let max_rows_per_copy = max_rows_per_copy / format_desc.block_dimensions.1 as u32
            * format_desc.block_dimensions.1 as u32;
        assert!(max_rows_per_copy > 0, "Zero buffer size is too small to fill a single row of a texture with format {:?} and desc {:?}",
                        texture_desc.format, texture_desc.size);

        let z_range = 0..(if texture_desc.dimension == wgt::TextureDimension::D3 {
            mip_size.depth_or_array_layers
        } else {
            1
        });

        for array_layer in layer_range.clone() {
            // TODO: Only doing one layer at a time for volume textures right now.
            for z in z_range.clone() {
                // May need multiple copies for each subresource! However, we assume that we never need to split a row.
                let mut num_rows_left = mip_size.height;
                while num_rows_left > 0 {
                    let num_rows = num_rows_left.min(max_rows_per_copy);

                    out_copy_regions.push(hal::BufferTextureCopy {
                        buffer_layout: wgt::ImageDataLayout {
                            offset: 0,
                            bytes_per_row: NonZeroU32::new(bytes_per_row),
                            rows_per_image: None,
                        },
                        texture_base: hal::TextureCopyBase {
                            mip_level,
                            array_layer,
                            origin: wgt::Origin3d {
                                x: 0, // Always full rows
                                y: mip_size.height - num_rows_left,
                                z,
                            },
                            aspect: hal::FormatAspects::all(),
                        },
                        size: hal::CopyExtent {
                            width: mip_size.width, // full row
                            height: num_rows,
                            depth: 1, // Only single slice of volume texture at a time right now
                        },
                    });

                    num_rows_left -= num_rows;
                }
            }
        }
    }
}