//! Convolution operations using Metal Performance Shaders

use metal::foreign_types::ForeignType;
use metal::NSUInteger;
use metal::{CommandBuffer, Device};
use objc2::msg_send;
use objc2::runtime::AnyObject;

use crate::metal::{
    buffer::MetalBuffer,
    error::{MetalError, Result},
    mps::{create_conv_descriptor, create_image_descriptor, MPSDataType},
};

/// 2D Convolution using MPS
#[allow(dead_code)]
pub struct MPSConv2d {
    /// MPS CNN convolution object
    conv: *mut AnyObject,
    /// Output buffer  
    output: MetalBuffer,
    /// Convolution parameters
    params: Conv2dParams,
    /// Device reference
    device: Device,
}

/// Convolution parameters
#[derive(Debug, Clone)]
pub struct Conv2dParams {
    pub batch_size: usize,
    pub in_channels: usize,
    pub out_channels: usize,
    pub height: usize,
    pub width: usize,
    pub kernel_height: usize,
    pub kernel_width: usize,
    pub stride_height: usize,
    pub stride_width: usize,
    pub padding_height: usize,
    pub padding_width: usize,
    pub dilation_height: usize,
    pub dilation_width: usize,
    pub groups: usize,
}

impl MPSConv2d {
    /// Create a new MPS 2D convolution operation
    pub fn new(
        device: &Device,
        params: Conv2dParams,
        weights: &MetalBuffer,
        bias: Option<&MetalBuffer>,
    ) -> Result<Self> {
        unsafe {
            // Validate parameters
            if params.in_channels % params.groups != 0 || params.out_channels % params.groups != 0 {
                return Err(MetalError::BackendError(
                    "Invalid group convolution parameters".to_string(),
                ));
            }

            // Calculate output dimensions
            let out_height = (params.height + 2 * params.padding_height - params.kernel_height)
                / params.stride_height
                + 1;
            let out_width = (params.width + 2 * params.padding_width - params.kernel_width)
                / params.stride_width
                + 1;

            // Create output buffer
            let output_shape = vec![
                params.batch_size,
                params.out_channels,
                out_height,
                out_width,
            ];
            let output = MetalBuffer::zeros(
                &torsh_core::Shape::from(output_shape),
                &torsh_core::DType::F32,
                &crate::metal::device::MetalDevice::new()?,
            )?;

            // Create convolution descriptor
            let desc = create_conv_descriptor(
                params.kernel_height,
                params.kernel_width,
                params.in_channels / params.groups,
                params.out_channels,
            );

            // Set stride
            let _: () = msg_send![desc, setStrideInPixelsX: params.stride_width as NSUInteger];
            let _: () = msg_send![desc, setStrideInPixelsY: params.stride_height as NSUInteger];

            // Set groups
            let _: () = msg_send![desc, setGroups: params.groups as NSUInteger];

            // Create CNN convolution
            let class = objc2::class!(MPSCNNConvolution);
            let conv: *mut AnyObject = msg_send![class, alloc];

            // Initialize with weights
            let weights_ptr = weights.buffer().contents() as *const f32;
            let bias_ptr = if let Some(b) = bias {
                b.buffer().contents() as *const f32
            } else {
                std::ptr::null()
            };

            let conv: *mut AnyObject = msg_send![conv,
                initWithDevice: device.as_ptr() as *mut AnyObject,
                convolutionDescriptor: desc,
                kernelWeights: weights_ptr,
                biasTerms: bias_ptr,
                flags: 0 as NSUInteger // MPSCNNConvolutionFlagsNone
            ];

            // Set padding
            let _: () = msg_send![conv, setPaddingLeft: params.padding_width as NSUInteger];
            let _: () = msg_send![conv, setPaddingRight: params.padding_width as NSUInteger];
            let _: () = msg_send![conv, setPaddingTop: params.padding_height as NSUInteger];
            let _: () = msg_send![conv, setPaddingBottom: params.padding_height as NSUInteger];

            Ok(Self {
                conv,
                output,
                params: params.clone(),
                device: device.clone(),
            })
        }
    }

    /// Encode the convolution operation
    pub fn encode_conv(&self, command_buffer: &CommandBuffer, _input: &MetalBuffer) -> Result<()> {
        unsafe {
            // Create MPS images
            let class = objc2::class!(MPSImage);

            // Input image
            let in_desc = create_image_descriptor(
                self.params.width,
                self.params.height,
                self.params.in_channels,
                MPSDataType::Float32,
            );

            let input_image: *mut AnyObject = msg_send![class, alloc];
            let input_image: *mut AnyObject = msg_send![input_image,
                initWithDevice: self.device.as_ptr() as *mut AnyObject,
                imageDescriptor: in_desc
            ];

            // Copy data to image (this is simplified - real implementation would handle layout)
            // In practice, you'd use MPSImageBatch for batch processing

            // Output image
            let out_desc = create_image_descriptor(
                (self.params.width + 2 * self.params.padding_width - self.params.kernel_width)
                    / self.params.stride_width
                    + 1,
                (self.params.height + 2 * self.params.padding_height - self.params.kernel_height)
                    / self.params.stride_height
                    + 1,
                self.params.out_channels,
                MPSDataType::Float32,
            );

            let output_image: *mut AnyObject = msg_send![class, alloc];
            let output_image: *mut AnyObject = msg_send![output_image,
                initWithDevice: self.device.as_ptr() as *mut AnyObject,
                imageDescriptor: out_desc
            ];

            // Encode the convolution
            let _: () = msg_send![self.conv,
                encodeToCommandBuffer: command_buffer.as_ptr() as *mut AnyObject,
                sourceImage: input_image,
                destinationImage: output_image
            ];

            Ok(())
        }
    }

    /// Get the output buffer
    pub fn output(&self) -> &MetalBuffer {
        &self.output
    }
}

impl Drop for MPSConv2d {
    fn drop(&mut self) {
        unsafe {
            let _: () = msg_send![self.conv, release];
        }
    }
}
