// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "impeller/entity/geometry/fill_path_geometry.h"
#include "impeller/core/formats.h"

namespace impeller {

FillPathGeometry::FillPathGeometry(Path path, std::optional<Rect> inner_rect)
    : path_(std::move(path)), inner_rect_(inner_rect) {}

GeometryResult FillPathGeometry::GetPositionBuffer(
    const ContentContext& renderer,
    const Entity& entity,
    RenderPass& pass) const {
  auto& host_buffer = renderer.GetTransientsBuffer();
  VertexBuffer vertex_buffer;

  if (path_.GetFillType() == FillType::kNonZero &&  //
      path_.IsConvex()) {
    auto points = renderer.GetTessellator()->TessellateConvex(
        path_, entity.GetTransform().GetMaxBasisLength());

    vertex_buffer.vertex_buffer = host_buffer.Emplace(
        points.data(), points.size() * sizeof(Point), alignof(Point));
    vertex_buffer.index_buffer = {}, vertex_buffer.vertex_count = points.size();
    vertex_buffer.index_type = IndexType::kNone;

    return GeometryResult{
        .type = PrimitiveType::kTriangleStrip,
        .vertex_buffer = vertex_buffer,
        .transform = pass.GetOrthographicTransform() * entity.GetTransform(),
        .prevent_overdraw = false,
    };
  }

  auto tesselation_result = renderer.GetTessellator()->Tessellate(
      path_, entity.GetTransform().GetMaxBasisLength(),
      [&vertex_buffer, &host_buffer](
          const float* vertices, size_t vertices_count, const uint16_t* indices,
          size_t indices_count) {
        vertex_buffer.vertex_buffer = host_buffer.Emplace(
            vertices, vertices_count * sizeof(float) * 2, alignof(float));
        if (indices != nullptr) {
          vertex_buffer.index_buffer = host_buffer.Emplace(
              indices, indices_count * sizeof(uint16_t), alignof(uint16_t));
          vertex_buffer.vertex_count = indices_count;
          vertex_buffer.index_type = IndexType::k16bit;
        } else {
          vertex_buffer.index_buffer = {};
          vertex_buffer.vertex_count = vertices_count;
          vertex_buffer.index_type = IndexType::kNone;
        }
        return true;
      });
  if (tesselation_result != Tessellator::Result::kSuccess) {
    return {};
  }
  return GeometryResult{
      .type = PrimitiveType::kTriangle,
      .vertex_buffer = vertex_buffer,
      .transform = pass.GetOrthographicTransform() * entity.GetTransform(),
      .prevent_overdraw = false,
  };
}

// |Geometry|
GeometryResult FillPathGeometry::GetPositionUVBuffer(
    Rect texture_coverage,
    Matrix effect_transform,
    const ContentContext& renderer,
    const Entity& entity,
    RenderPass& pass) const {
  using VS = TextureFillVertexShader;

  auto uv_transform =
      texture_coverage.GetNormalizingTransform() * effect_transform;

  if (path_.GetFillType() == FillType::kNonZero &&  //
      path_.IsConvex()) {
    auto points = renderer.GetTessellator()->TessellateConvex(
        path_, entity.GetTransform().GetMaxBasisLength());

    VertexBufferBuilder<VS::PerVertexData> vertex_builder;
    vertex_builder.Reserve(points.size());
    for (auto i = 0u; i < points.size(); i++) {
      VS::PerVertexData data;
      data.position = points[i];
      data.texture_coords = uv_transform * points[i];
      vertex_builder.AppendVertex(data);
    }

    return GeometryResult{
        .type = PrimitiveType::kTriangleStrip,
        .vertex_buffer =
            vertex_builder.CreateVertexBuffer(renderer.GetTransientsBuffer()),
        .transform = pass.GetOrthographicTransform() * entity.GetTransform(),
        .prevent_overdraw = false,
    };
  }

  VertexBufferBuilder<VS::PerVertexData> vertex_builder;
  auto tesselation_result = renderer.GetTessellator()->Tessellate(
      path_, entity.GetTransform().GetMaxBasisLength(),
      [&vertex_builder, &uv_transform](
          const float* vertices, size_t vertices_count, const uint16_t* indices,
          size_t indices_count) {
        for (auto i = 0u; i < vertices_count * 2; i += 2) {
          VS::PerVertexData data;
          Point vtx = {vertices[i], vertices[i + 1]};
          data.position = vtx;
          data.texture_coords = uv_transform * vtx;
          vertex_builder.AppendVertex(data);
        }
        FML_DCHECK(vertex_builder.GetVertexCount() == vertices_count);
        if (indices != nullptr) {
          for (auto i = 0u; i < indices_count; i++) {
            vertex_builder.AppendIndex(indices[i]);
          }
        }
        return true;
      });
  if (tesselation_result != Tessellator::Result::kSuccess) {
    return {};
  }
  return GeometryResult{
      .type = PrimitiveType::kTriangle,
      .vertex_buffer =
          vertex_builder.CreateVertexBuffer(renderer.GetTransientsBuffer()),
      .transform = pass.GetOrthographicTransform() * entity.GetTransform(),
      .prevent_overdraw = false,
  };
}

GeometryVertexType FillPathGeometry::GetVertexType() const {
  return GeometryVertexType::kPosition;
}

std::optional<Rect> FillPathGeometry::GetCoverage(
    const Matrix& transform) const {
  return path_.GetTransformedBoundingBox(transform);
}

bool FillPathGeometry::CoversArea(const Matrix& transform,
                                  const Rect& rect) const {
  if (!inner_rect_.has_value()) {
    return false;
  }
  if (!transform.IsTranslationScaleOnly()) {
    return false;
  }
  Rect coverage = inner_rect_->TransformBounds(transform);
  return coverage.Contains(rect);
}

}  // namespace impeller