/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated January 1, 2020. Replaces all prior versions.
 *
 * Copyright (c) 2013-2020, Esoteric Software LLC
 *
 * Integration of the Spine Runtimes into software or otherwise creating
 * derivative works of the Spine Runtimes is permitted under the terms and
 * conditions of Section 2 of the Spine Editor License Agreement:
 * http://esotericsoftware.com/spine-editor-license
 *
 * Otherwise, it is permitted to integrate the Spine Runtimes into software
 * or otherwise create derivative works of the Spine Runtimes (collectively,
 * "Products"), provided that each user of the Products must obtain their own
 * Spine Editor license and redistribution of the Products in any form must
 * include this license and copyright notice.
 *
 * THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL ESOTERIC SOFTWARE LLC BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES,
 * BUSINESS INTERRUPTION, OR LOSS OF USE, DATA, OR PROFITS) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THE SPINE RUNTIMES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

#ifdef SPINE_UE4
    #include "SpinePluginPrivatePCH.h"
#endif

#include <spine/SkeletonClipping.h>

#include <spine/ClippingAttachment.h>
#include <spine/Slot.h>

using namespace spine;

SkeletonClipping::SkeletonClipping() : _clipAttachment(NULL) {
    _clipOutput.ensureCapacity(128);
    _clippedVertices.ensureCapacity(128);
    _clippedTriangles.ensureCapacity(128);
    _clippedUVs.ensureCapacity(128);
}

size_t SkeletonClipping::clipStart(Slot &slot, ClippingAttachment *clip) {
    if (_clipAttachment != NULL) {
        return 0;
    }

    _clipAttachment = clip;

    int n = clip->getWorldVerticesLength();
    _clippingPolygon.setSize(n, 0);
    clip->computeWorldVertices(slot, 0, n, _clippingPolygon, 0, 2);
    makeClockwise(_clippingPolygon);
    _clippingPolygons = &_triangulator.decompose(_clippingPolygon, _triangulator.triangulate(_clippingPolygon));

    for (size_t i = 0; i < _clippingPolygons->size(); ++i) {
        Vector<float> *polygonP = (*_clippingPolygons)[i];
        Vector<float> &polygon = *polygonP;
        makeClockwise(polygon);
        polygon.add(polygon[0]);
        polygon.add(polygon[1]);
    }

    return (*_clippingPolygons).size();
}

void SkeletonClipping::clipEnd(Slot &slot) {
    if (_clipAttachment != NULL && _clipAttachment->_endSlot == &slot._data) {
        clipEnd();
    }
}

void SkeletonClipping::clipEnd() {
    if (_clipAttachment == NULL) return;

    _clipAttachment = NULL;
    _clippingPolygons = NULL;
    _clippedVertices.clear();
    _clippedUVs.clear();
    _clippedTriangles.clear();
    _clippingPolygon.clear();
}

void SkeletonClipping::clipTriangles(Vector<float> &vertices, Vector<unsigned short> &triangles, Vector<float> &uvs, size_t stride) {
    clipTriangles(vertices.buffer(), triangles.buffer(), triangles.size(), uvs.buffer(), stride);
}

void SkeletonClipping::clipTriangles(float *vertices, unsigned short *triangles,
                                     size_t trianglesLength, float *uvs, size_t stride) {
    Vector<float> &clipOutput = _clipOutput;
    Vector<float> &clippedVertices = _clippedVertices;
    Vector<unsigned short> &clippedTriangles = _clippedTriangles;
    Vector<Vector<float> *> &polygons = *_clippingPolygons;
    size_t polygonsCount = (*_clippingPolygons).size();

    size_t index = 0;
    clippedVertices.clear();
    _clippedUVs.clear();
    clippedTriangles.clear();

    size_t i = 0;
continue_outer:
    for (; i < trianglesLength; i += 3) {
        int vertexOffset = triangles[i] * stride;
        float x1 = vertices[vertexOffset], y1 = vertices[vertexOffset + 1];
        float u1 = uvs[vertexOffset], v1 = uvs[vertexOffset + 1];

        vertexOffset = triangles[i + 1] * stride;
        float x2 = vertices[vertexOffset], y2 = vertices[vertexOffset + 1];
        float u2 = uvs[vertexOffset], v2 = uvs[vertexOffset + 1];

        vertexOffset = triangles[i + 2] * stride;
        float x3 = vertices[vertexOffset], y3 = vertices[vertexOffset + 1];
        float u3 = uvs[vertexOffset], v3 = uvs[vertexOffset + 1];

        for (size_t p = 0; p < polygonsCount; p++) {
            size_t s = clippedVertices.size();
            if (clip(x1, y1, x2, y2, x3, y3, &(*polygons[p]), &clipOutput)) {
                size_t clipOutputLength = clipOutput.size();
                if (clipOutputLength == 0) continue;
                float d0 = y2 - y3, d1 = x3 - x2, d2 = x1 - x3, d4 = y3 - y1;
                float d = 1 / (d0 * d2 + d1 * (y1 - y3));

                size_t clipOutputCount = clipOutputLength >> 1;
                clippedVertices.setSize(s + clipOutputCount * 2, 0);
                _clippedUVs.setSize(s + clipOutputCount * 2, 0);
                for (size_t ii = 0; ii < clipOutputLength; ii += 2) {
                    float x = clipOutput[ii], y = clipOutput[ii + 1];
                    clippedVertices[s] = x;
                    clippedVertices[s + 1] = y;
                    float c0 = x - x3, c1 = y - y3;
                    float a = (d0 * c0 + d1 * c1) * d;
                    float b = (d4 * c0 + d2 * c1) * d;
                    float c = 1 - a - b;
                    _clippedUVs[s] = u1 * a + u2 * b + u3 * c;
                    _clippedUVs[s + 1] = v1 * a + v2 * b + v3 * c;
                    s += 2;
                }

                s = clippedTriangles.size();
                clippedTriangles.setSize(s + 3 * (clipOutputCount - 2), 0);
                clipOutputCount--;
                for (size_t ii = 1; ii < clipOutputCount; ii++) {
                    clippedTriangles[s] = (unsigned short)(index);
                    clippedTriangles[s + 1] = (unsigned short)(index + ii);
                    clippedTriangles[s + 2] = (unsigned short)(index + ii + 1);
                    s += 3;
                }
                index += clipOutputCount + 1;
            } else {
                clippedVertices.setSize(s + 3 * 2, 0);
                _clippedUVs.setSize(s + 3 * 2, 0);
                clippedVertices[s] = x1;
                clippedVertices[s + 1] = y1;
                clippedVertices[s + 2] = x2;
                clippedVertices[s + 3] = y2;
                clippedVertices[s + 4] = x3;
                clippedVertices[s + 5] = y3;

                _clippedUVs[s] = u1;
                _clippedUVs[s + 1] = v1;
                _clippedUVs[s + 2] = u2;
                _clippedUVs[s + 3] = v2;
                _clippedUVs[s + 4] = u3;
                _clippedUVs[s + 5] = v3;

                s = clippedTriangles.size();
                clippedTriangles.setSize(s + 3, 0);
                clippedTriangles[s] = (unsigned short)index;
                clippedTriangles[s + 1] = (unsigned short)(index + 1);
                clippedTriangles[s + 2] = (unsigned short)(index + 2);
                index += 3;
                i += 3;
                goto continue_outer;
            }
        }
    }
}

bool SkeletonClipping::isClipping() {
    return _clipAttachment != NULL;
}

Vector<float> &SkeletonClipping::getClippedVertices() {
    return _clippedVertices;
}

Vector<unsigned short> &SkeletonClipping::getClippedTriangles() {
    return _clippedTriangles;
}

Vector<float> &SkeletonClipping::getClippedUVs() {
    return _clippedUVs;
}

bool SkeletonClipping::clip(float x1, float y1, float x2, float y2, float x3, float y3, Vector<float> *clippingArea,
                            Vector<float> *output) {
    Vector<float> *originalOutput = output;
    bool clipped = false;

    // Avoid copy at the end.
    Vector<float> *input;
    if (clippingArea->size() % 4 >= 2) {
        input = output;
        output = &_scratch;
    } else
        input = &_scratch;

    input->clear();
    input->add(x1);
    input->add(y1);
    input->add(x2);
    input->add(y2);
    input->add(x3);
    input->add(y3);
    input->add(x1);
    input->add(y1);
    output->clear();

    Vector<float> &clippingVertices = *clippingArea;
    size_t clippingVerticesLast = clippingArea->size() - 4;
    for (size_t i = 0;; i += 2) {
        float edgeX = clippingVertices[i], edgeY = clippingVertices[i + 1];
        float edgeX2 = clippingVertices[i + 2], edgeY2 = clippingVertices[i + 3];
        float deltaX = edgeX - edgeX2, deltaY = edgeY - edgeY2;

        Vector<float> &inputVertices = *input;
        size_t inputVerticesLength = input->size() - 2, outputStart = output->size();
        for (size_t ii = 0; ii < inputVerticesLength; ii += 2) {
            float inputX = inputVertices[ii], inputY = inputVertices[ii + 1];
            float inputX2 = inputVertices[ii + 2], inputY2 = inputVertices[ii + 3];
            bool side2 = deltaX * (inputY2 - edgeY2) - deltaY * (inputX2 - edgeX2) > 0;
            if (deltaX * (inputY - edgeY2) - deltaY * (inputX - edgeX2) > 0) {
                if (side2) {
                    // v1 inside, v2 inside
                    output->add(inputX2);
                    output->add(inputY2);
                    continue;
                }
                // v1 inside, v2 outside
                float c0 = inputY2 - inputY, c2 = inputX2 - inputX;
                float s = c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY);
                if (MathUtil::abs(s) > 0.000001f) {
                    float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / s;
                    output->add(edgeX + (edgeX2 - edgeX) * ua);
                    output->add(edgeY + (edgeY2 - edgeY) * ua);
                } else {
                    output->add(edgeX);
                    output->add(edgeY);
                }
            } else if (side2) {
                // v1 outside, v2 inside
                float c0 = inputY2 - inputY, c2 = inputX2 - inputX;
                float s = c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY);
                if (MathUtil::abs(s) > 0.000001f) {
                    float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / s;
                    output->add(edgeX + (edgeX2 - edgeX) * ua);
                    output->add(edgeY + (edgeY2 - edgeY) * ua);
                } else {
                    output->add(edgeX);
                    output->add(edgeY);
                }
                output->add(inputX2);
                output->add(inputY2);
            }
            clipped = true;
        }

        if (outputStart == output->size()) {
            // All edges outside.
            originalOutput->clear();
            return true;
        }

        output->add((*output)[0]);
        output->add((*output)[1]);

        if (i == clippingVerticesLast) {
            break;
        }
        Vector<float> *temp = output;
        output = input;
        output->clear();
        input = temp;
    }

    if (originalOutput != output) {
        originalOutput->clear();
        for (size_t i = 0, n = output->size() - 2; i < n; ++i)
            originalOutput->add((*output)[i]);
    } else
        originalOutput->setSize(originalOutput->size() - 2, 0);

    return clipped;
}

void SkeletonClipping::makeClockwise(Vector<float> &polygon) {
    size_t verticeslength = polygon.size();

    float area = polygon[verticeslength - 2] * polygon[1] - polygon[0] * polygon[verticeslength - 1];
    float p1x, p1y, p2x, p2y;

    for (size_t i = 0, n = verticeslength - 3; i < n; i += 2) {
        p1x = polygon[i];
        p1y = polygon[i + 1];
        p2x = polygon[i + 2];
        p2y = polygon[i + 3];
        area += p1x * p2y - p2x * p1y;
    }

    if (area < 0) return;

    for (size_t i = 0, lastX = verticeslength - 2, n = verticeslength >> 1; i < n; i += 2) {
        float x = polygon[i], y = polygon[i + 1];
        int other = lastX - i;
        polygon[i] = polygon[other];
        polygon[i + 1] = polygon[other + 1];
        polygon[other] = x;
        polygon[other + 1] = y;
    }
}
