// Copyright 2020 Arthur Sonzogni. All rights reserved.
// Use of this source code is governed by the MIT license that can be found in
// the LICENSE file.
#include <algorithm>  // for max
#include <cstddef>    // for size_t
#include <memory>  // for __shared_ptr_access, shared_ptr, make_shared, allocator_traits<>::value_type
#include <utility>  // for move
#include <vector>   // for vector, __alloc_traits<>::value_type

#include "ftxui/dom/box_helper.hpp"   // for Element, Compute
#include "ftxui/dom/elements.hpp"     // for Element, Elements, vbox
#include "ftxui/dom/node.hpp"         // for Node, Elements
#include "ftxui/dom/requirement.hpp"  // for Requirement
#include "ftxui/screen/box.hpp"       // for Box

namespace ftxui {

namespace {
class VBox : public Node {
 public:
  explicit VBox(Elements children) : Node(std::move(children)) {}

 private:
  void ComputeRequirement() override {
    requirement_ = Requirement{};

    for (auto& child : children_) {
      child->ComputeRequirement();

      // Propagate the focused requirement.
      if (requirement_.focused.Prefer(child->requirement().focused)) {
        requirement_.focused = child->requirement().focused;
        requirement_.focused.box.Shift(0, requirement_.min_y);
      }

      // Extend the min_x and min_y to contain all the children
      requirement_.min_y += child->requirement().min_y;
      requirement_.min_x =
          std::max(requirement_.min_x, child->requirement().min_x);
    }
  }

  void SetBox(Box box) override {
    Node::SetBox(box);

    std::vector<box_helper::Element> elements(children_.size());
    for (size_t i = 0; i < children_.size(); ++i) {
      auto& element = elements[i];
      const auto& requirement = children_[i]->requirement();
      element.min_size = requirement.min_y;
      element.flex_grow = requirement.flex_grow_y;
      element.flex_shrink = requirement.flex_shrink_y;
    }
    const int target_size = box.y_max - box.y_min + 1;
    box_helper::Compute(&elements, target_size);

    int y = box.y_min;
    for (size_t i = 0; i < children_.size(); ++i) {
      box.y_min = y;
      box.y_max = y + elements[i].size - 1;
      children_[i]->SetBox(box);
      y = box.y_max + 1;
    }
  }

  void Select(Selection& selection) override {
    // If this Node box_ doesn't intersect with the selection, then no
    // selection.
    if (Box::Intersection(selection.GetBox(), box_).IsEmpty()) {
      return;
    }

    Selection selection_saturated = selection.SaturateVertical(box_);

    for (auto& child : children_) {
      child->Select(selection_saturated);
    }
  }
};
}  // namespace

/// @brief A container displaying elements vertically one by one.
/// @param children The elements in the container
/// @return The container.
/// @ingroup dom
///
/// #### Example
///
/// ```cpp
/// vbox({
///   text("Up"),
///   text("Down"),
/// });
/// ```
Element vbox(Elements children) {
  return std::make_shared<VBox>(std::move(children));
}

}  // namespace ftxui