// SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use super::*;

/// Copy a block from a source to a destination using memcpy
pub fn copy_block<'a, Source, Destination>(
    sources: &'a Source,
    destinations: &'a mut Destination,
) -> Result<(), TransferError>
where
    Source: ReadableBlock,
    Destination: WritableBlock,
{
    let src_data = sources.block_data();
    let dst_data = destinations.block_data_mut();

    if src_data.is_fully_contiguous() && dst_data.is_fully_contiguous() {
        let src_view = src_data.block_view()?;
        let mut dst_view = dst_data.block_view_mut()?;
        debug_assert_eq!(src_view.size(), dst_view.size());
        unsafe {
            memcpy(src_view.as_ptr(), dst_view.as_mut_ptr(), src_view.size());
        }
    } else {
        assert_eq!(src_data.num_layers(), dst_data.num_layers());
        copy_layers(0..src_data.num_layers(), sources, destinations)?;
    }
    Ok(())
}

/// Copy a range of layers from a source to a destination using memcpy
pub fn copy_layers<'a, Source, Destination>(
    layer_range: Range<usize>,
    sources: &'a Source,
    destinations: &'a mut Destination,
) -> Result<(), TransferError>
where
    Source: ReadableBlock,
    // <Source as ReadableBlock>::StorageType: SystemAccessible + Local,
    Destination: WritableBlock,
    // <Destination as WritableBlock>::StorageType: SystemAccessible + Local,
{
    let src_data = sources.block_data();
    let dst_data = destinations.block_data_mut();

    for layer_idx in layer_range {
        for outer_idx in 0..src_data.num_outer_dims() {
            let src_view = src_data.layer_view(layer_idx, outer_idx)?;
            let mut dst_view = dst_data.layer_view_mut(layer_idx, outer_idx)?;

            debug_assert_eq!(src_view.size(), dst_view.size());
            unsafe {
                memcpy(src_view.as_ptr(), dst_view.as_mut_ptr(), src_view.size());
            }
        }
    }
    Ok(())
}

#[inline(always)]
unsafe fn memcpy(src_ptr: *const u8, dst_ptr: *mut u8, size: usize) {
    debug_assert!(
        (src_ptr as usize + size <= dst_ptr as usize)
            || (dst_ptr as usize + size <= src_ptr as usize),
        "Source and destination memory regions must not overlap for copy_nonoverlapping"
    );

    std::ptr::copy_nonoverlapping(src_ptr, dst_ptr, size);
}
