/*
    This file is part of Magnum.

    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
                2020, 2021 Vladimír Vondruš <mosra@centrum.cz>

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/

#include "Interleave.h"

#include <Corrade/Containers/Optional.h>
#include <Corrade/Utility/Algorithms.h>

#include "Magnum/Math/Functions.h"
#include "Magnum/MeshTools/Reference.h"
#include "Magnum/Trade/MeshData.h"

namespace Magnum { namespace MeshTools {

namespace {

inline std::size_t attributeSize(const Trade::MeshData& data, UnsignedInt i) {
    return vertexFormatSize(data.attributeFormat(i))*Math::max(data.attributeArraySize(i), UnsignedShort{1});
}

inline std::size_t attributeSize(const Trade::MeshAttributeData& data) {
    return vertexFormatSize(data.format())*Math::max(data.arraySize(), UnsignedShort{1});
}
Containers::Optional<Containers::StridedArrayView2D<const char>> interleavedDataInternal(const Trade::MeshData& data) {
    /* There is no attributes, return a zero-sized view to indicate a success */
    if(!data.attributeCount())
        return Containers::StridedArrayView2D<const char>{data.vertexData(), {data.vertexCount(), 0}};

    /* Technically zero and negative strides *may* also be categorized as
       interleaved if they are all the same, but it causes way too many
       problems especially when used within interleavedLayout() etc. May
       tackle properly later. */
    const Int stride = data.attributeStride(0);
    if(stride <= 0) return Containers::NullOpt;

    std::size_t minOffset = ~std::size_t{};
    std::size_t maxOffset = 0;
    bool hasImplementationSpecificVertexFormat = false;
    for(UnsignedInt i = 0; i != data.attributeCount(); ++i) {
        if(data.attributeStride(i) != stride) return Containers::NullOpt;

        const std::size_t offset = data.attributeOffset(i);
        minOffset = Math::min(minOffset, offset);

        /* If the attribute has implementation-specific format, remember that
           for later and optimistically use size of 1 byte for calculations */
        std::size_t size;
        if(isVertexFormatImplementationSpecific(data.attributeFormat(i))) {
            hasImplementationSpecificVertexFormat = true;
            size = 1;
        } else size = attributeSize(data, i);

        maxOffset = Math::max(maxOffset, offset + size);
    }

    /* If there's an attribute with implementation-specific format,
       conservatively use the whole stride for it. This should work for
       majority of cases except when the stride has a padding at the end and
       the padding isn't included in the vertexData array for the last vertex,
       but that'd probably blow up in many other cases (and drivers) as well. */
    if(hasImplementationSpecificVertexFormat)
        maxOffset = Math::max(maxOffset, minOffset + stride);

    /* The offsets can't fit into the stride, report failure */
    if(maxOffset - minOffset > UnsignedInt(stride)) return Containers::NullOpt;

    return Containers::StridedArrayView2D<const char>{
        data.vertexData(), data.vertexData().data() + minOffset,
        {data.vertexCount(), maxOffset - minOffset},
        {std::ptrdiff_t(stride), 1}};
}

}

bool isInterleaved(const Trade::MeshData& data) {
    return !!interleavedDataInternal(data);
}

Containers::StridedArrayView2D<const char> interleavedData(const Trade::MeshData& data) {
    auto out = interleavedDataInternal(data);
    CORRADE_ASSERT(out, "MeshTools::interleavedData(): the mesh is not interleaved", {});
    return *out;
}

Containers::StridedArrayView2D<char> interleavedMutableData(Trade::MeshData& data) {
    Containers::StridedArrayView2D<const char> out = interleavedData(data);
    CORRADE_ASSERT(data.vertexDataFlags() & Trade::DataFlag::Mutable,
        "MeshTools::interleavedMutableData(): vertex data is not mutable", {});
    return Containers::StridedArrayView2D<char>{
        {nullptr, ~std::size_t{}}, /* to sidestep the range assertions */
        const_cast<char*>(reinterpret_cast<const char*>(out.data())),
        out.size(), out.stride()};
}

namespace Implementation {

Containers::Array<Trade::MeshAttributeData> interleavedLayout(Trade::MeshData&& data, const Containers::ArrayView<const Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    /* Nothing to do here, bye! */
    if(!data.attributeCount() && extra.empty()) return {};

    /* If we're not told to preserve the layout, treat the mesh as
       noninterleaved always, forcing a repack. Otherwise check if it's already
       interleaved. */
    const bool interleaved = flags >= InterleaveFlag::PreserveInterleavedAttributes && isInterleaved(data);

    /* If the mesh is already interleaved, use the original stride to
       preserve all padding, but remove the initial offset. Otherwise calculate
       a tightly-packed stride. */
    std::size_t stride;
    std::size_t minOffset;
    if(interleaved && data.attributeCount()) {
        stride = data.attributeStride(0);
        minOffset = ~std::size_t{};
        for(UnsignedInt i = 0, max = data.attributeCount(); i != max; ++i)
            minOffset = Math::min(minOffset, data.attributeOffset(i));
    } else {
        stride = 0;
        minOffset = 0;
        for(UnsignedInt i = 0, max = data.attributeCount(); i != max; ++i) {
            const VertexFormat format = data.attributeFormat(i);
            CORRADE_ASSERT(!isVertexFormatImplementationSpecific(format),
                "MeshTools::interleavedLayout(): attribute" << i << "has an implementation-specific format" << reinterpret_cast<void*>(vertexFormatUnwrap(format)), {});
            stride += attributeSize(data, i);
        }
    }

    /* Add the extra attributes and explicit padding */
    std::size_t extraAttributeCount = 0;
    for(std::size_t i = 0; i != extra.size(); ++i) {
        if(extra[i].format() == VertexFormat{}) {
            CORRADE_ASSERT(extra[i].stride() > 0 || stride >= std::size_t(-extra[i].stride()),
                "MeshTools::interleavedLayout(): negative padding" << extra[i].stride() << "in extra attribute" << i << "too large for stride" << stride, {});
            stride += extra[i].stride();
        } else {
            const VertexFormat format = extra[i].format();
            CORRADE_ASSERT(!isVertexFormatImplementationSpecific(format),
                "MeshTools::interleavedLayout(): extra attribute" << i << "has an implementation-specific format" << reinterpret_cast<void*>(vertexFormatUnwrap(format)), {});
            stride += attributeSize(extra[i]);
            ++extraAttributeCount;
        }
    }

    /* Transfer the attribute data array. If there are no extra attributes and
       the attribute data array is owned (the array has a default deleter), we
       can take over the ownership and avoid an allocation. Otherwise we
       allocate a new array and copy the prefix over so we can just patch the
       data array later. */
    const UnsignedInt originalAttributeCount = data.attributeCount();
    const UnsignedInt originalAttributeStride = originalAttributeCount ?
        data.attributeStride(0) : 0;
    Containers::Array<Trade::MeshAttributeData> originalAttributeData =
        data.releaseAttributeData();
    Containers::Array<Trade::MeshAttributeData> attributeData;
    if(!extraAttributeCount && !originalAttributeData.deleter())
        attributeData = std::move(originalAttributeData);
    else {
        attributeData = Containers::Array<Trade::MeshAttributeData>{originalAttributeCount + extraAttributeCount};
        Utility::copy(originalAttributeData, attributeData.prefix(originalAttributeCount));
    }

    /* Copy existing attribute layout. If the original is already interleaved,
       preserve relative attribute offsets, otherwise pack tightly. */
    std::size_t offset = 0;
    for(UnsignedInt i = 0; i != originalAttributeCount; ++i) {
        if(interleaved) offset = attributeData[i].offset(data.vertexData()) - minOffset;

        attributeData[i] = Trade::MeshAttributeData{
            attributeData[i].name(), attributeData[i].format(),
            offset, 0, std::ptrdiff_t(stride), attributeData[i].arraySize()};

        if(!interleaved) offset += attributeSize(attributeData[i]);
    }

    /* In case the original is already interleaved, set the offset for extra
       attribs to the original stride to preserve also potential padding at the
       end. */
    if(interleaved && originalAttributeCount)
        offset = originalAttributeStride;

    /* Mix in the extra attributes */
    UnsignedInt attributeIndex = originalAttributeCount;
    for(UnsignedInt i = 0; i != extra.size(); ++i) {
        /* Padding, only adjust the offset for next attribute */
        if(extra[i].format() == VertexFormat{}) {
            offset += extra[i].stride();
            continue;
        }

        attributeData[attributeIndex++] = Trade::MeshAttributeData{
            extra[i].name(), extra[i].format(),
            offset, 0, std::ptrdiff_t(stride), extra[i].arraySize()};

        offset += attributeSize(extra[i]);
    }

    return attributeData;
}

}

Trade::MeshData interleavedLayout(Trade::MeshData&& data, const UnsignedInt vertexCount, const Containers::ArrayView<const Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    Containers::Array<Trade::MeshAttributeData> attributeData = Implementation::interleavedLayout(std::move(data), extra, flags);

    /* If there are no attributes, bail -- return an empty mesh with desired
       vertex count but nothing else */
    if(!attributeData)
        return Trade::MeshData{data.primitive(), vertexCount};

    /* Allocate new data array */
    Containers::Array<char> vertexData{NoInit, attributeData[0].stride()*vertexCount};

    /* Convert the attributes from offset-only and zero vertex count to
       absolute, referencing the above-allocated data array */
    for(Trade::MeshAttributeData& attribute: attributeData) {
        attribute = Trade::MeshAttributeData{
            attribute.name(), attribute.format(),
            Containers::StridedArrayView1D<void>{vertexData,
                vertexData + attribute.offset(vertexData),
                vertexCount, attribute.stride()},
            attribute.arraySize()};
    }

    return Trade::MeshData{data.primitive(), std::move(vertexData), std::move(attributeData)};
}

Trade::MeshData interleavedLayout(Trade::MeshData&& data, const UnsignedInt vertexCount, const std::initializer_list<Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    return interleavedLayout(std::move(data), vertexCount, Containers::arrayView(extra), flags);
}

Trade::MeshData interleavedLayout(const Trade::MeshData& data, const UnsignedInt vertexCount, const Containers::ArrayView<const Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    /* Pass through to the && overload, which then decides whether to reuse
       anything based on the DataFlags */
    return interleavedLayout(reference(data), vertexCount, extra, flags);
}

Trade::MeshData interleavedLayout(const Trade::MeshData& data, const UnsignedInt vertexCount, const std::initializer_list<Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    return interleavedLayout(data, vertexCount, Containers::arrayView(extra), flags);
}

Trade::MeshData interleave(Trade::MeshData&& data, const Containers::ArrayView<const Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    /* Transfer the indices unchanged, in case the mesh is indexed */
    Containers::Array<char> indexData;
    Trade::MeshIndexData indices;
    if(data.isIndexed()) {
        const MeshIndexType indexType = data.indexType();

        /* If we can steal the data and we're allowed to preserve a strided
           layout or it's tightly packed, do the steal */
        if((data.indexDataFlags() & Trade::DataFlag::Owned) && ((flags & InterleaveFlag::PreserveStridedIndices) || (!isMeshIndexTypeImplementationSpecific(indexType) && data.indexStride() == Int(meshIndexTypeSize(indexType))))) {
            indices = Trade::MeshIndexData{indexType,
                Containers::StridedArrayView1D<const void>{
                    data.indexData(),
                    data.indexData().data() + data.indexOffset(),
                    data.indexCount(),
                    data.indexStride()}};
            indexData = data.releaseIndexData();

        /* Otherwise, if we can't steal the data but we're told to preserve
           strided indices, make a full copy including any extra offsets and
           paddings */
        } else if(flags & InterleaveFlag::PreserveStridedIndices) {
            indexData = Containers::Array<char>{NoInit, data.indexData().size()};
            indices = Trade::MeshIndexData{indexType,
                Containers::StridedArrayView1D<const void>{
                    indexData,
                    indexData.data() + data.indexOffset(),
                    data.indexCount(),
                    data.indexStride()}};
            Utility::copy(data.indexData(), indexData);

        /* Otherwise, make a tightly packed copy, in which case we can't have
           an implementation-specific index type */
        } else {
            CORRADE_ASSERT(!isMeshIndexTypeImplementationSpecific(indexType),
                "MeshTools::interleave(): mesh has an implementation-specific index type" << reinterpret_cast<void*>(meshIndexTypeUnwrap(indexType)) << Debug::nospace << ", enable MeshTools::InterleaveFlag::PreserveStridedIndices to pass the array through unchanged",
                (Trade::MeshData{MeshPrimitive{}, 0}));

            const std::size_t indexTypeSize = meshIndexTypeSize(indexType);
            indexData = Containers::Array<char>{NoInit, data.indexCount()*indexTypeSize};
            Containers::StridedArrayView2D<char> out{indexData,
                {data.indexCount(), indexTypeSize},
                {std::ptrdiff_t(indexTypeSize), 1}};
            indices = Trade::MeshIndexData{out};
            Utility::copy(data.indices(), out);
        }
    }

    /* If we're not told to preserve the layout, treat the mesh as
       noninterleaved always, forcing a repack. Otherwise check if it's already
       interleaved. */
    const bool interleaved = flags >= InterleaveFlag::PreserveInterleavedAttributes && isInterleaved(data);
    const UnsignedInt vertexCount = data.vertexCount();

    /* If the mesh is already interleaved and we don't have anything extra,
       steal that data as well */
    Containers::Array<char> vertexData;
    Containers::Array<Trade::MeshAttributeData> attributeData;
    if(interleaved && extra.empty() && (data.vertexDataFlags() & Trade::DataFlag::Owned)) {
        attributeData = data.releaseAttributeData();
        vertexData = data.releaseVertexData();

    /* Otherwise do it the hard way */
    } else {
        /* Calculate the layout. Can't std::move() the data in to avoid copying
           the attribute array as we need the original attributes below. */
        Trade::MeshData layout = interleavedLayout(data, vertexCount, extra, flags);
        #ifdef CORRADE_GRACEFUL_ASSERT
        /* If interleavedLayout() gracefully asserted and returned no
           attributes (but the original had some), exit right away to not blow
           up on something else later. Sorry, yes, this is shitty. */
        if(!layout.attributeCount() && (data.attributeCount() || extra.size()))
            return Trade::MeshData{MeshPrimitive::Points, 0};
        #endif

        /* Copy existing attributes to new locations */
        for(UnsignedInt i = 0; i != data.attributeCount(); ++i)
            Utility::copy(data.attribute(i), layout.mutableAttribute(i));

        /* Mix in the extra attributes */
        UnsignedInt attributeIndex = data.attributeCount();
        for(UnsignedInt i = 0; i != extra.size(); ++i) {
            /* Padding, ignore */
            if(extra[i].format() == VertexFormat{}) continue;

            /* Asserting here even though data() has another assert since that
               one would be too confusing in this context */
            CORRADE_ASSERT(!extra[i].isOffsetOnly(),
                "MeshTools::interleave(): extra attribute" << i << "is offset-only, which is not supported",
                (Trade::MeshData{MeshPrimitive::Triangles, 0}));

            /* Copy the attribute in, if it is non-empty, otherwise keep the
               memory uninitialized */
            if(extra[i].data()) {
                CORRADE_ASSERT(extra[i].data().size() == vertexCount,
                    "MeshTools::interleave(): extra attribute" << i << "expected to have" << vertexCount << "items but got" << extra[i].data().size(),
                    (Trade::MeshData{MeshPrimitive::Triangles, 0}));
                const Containers::StridedArrayView2D<const char> attribute =
                    Containers::arrayCast<2, const char>(extra[i].data(), vertexFormatSize(extra[i].format()));
                Utility::copy(attribute, layout.mutableAttribute(attributeIndex));
            }

            ++attributeIndex;
        }

        /* Release the data from the layout to pack them into the output */
        vertexData = layout.releaseVertexData();
        attributeData = layout.releaseAttributeData();
    }

    return Trade::MeshData{data.primitive(), std::move(indexData), indices,
        std::move(vertexData), std::move(attributeData), vertexCount};
}

Trade::MeshData interleave(Trade::MeshData&& data, const std::initializer_list<Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    return interleave(std::move(data), Containers::arrayView(extra), flags);
}

Trade::MeshData interleave(const Trade::MeshData& data, const Containers::ArrayView<const Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    /* Pass through to the && overload, which then decides whether to reuse
       anything based on the DataFlags */
    return interleave(reference(data), extra, flags);
}

Trade::MeshData interleave(const Trade::MeshData& data, const std::initializer_list<Trade::MeshAttributeData> extra, const InterleaveFlags flags) {
    return interleave(std::move(data), Containers::arrayView(extra), flags);
}

}}