/*************************************************************************/
/*  flow_container.cpp                                                   */
/*************************************************************************/
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/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
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#include "scene/gui/container.h"

#include "flow_container.h"

struct _LineData {
	int child_count = 0;
	int min_line_height = 0;
	int min_line_length = 0;
	int stretch_avail = 0;
	float stretch_ratio_total = 0;
};

void FlowContainer::_resort() {
	// Avoid resorting if invisible.
	if (!is_visible_in_tree()) {
		return;
	}

	int separation_horizontal = get_constant("hseparation");
	int separation_vertical = get_constant("vseparation");

	Map<Control *, Size2i> children_minsize_cache;

	Vector<_LineData> lines_data;

	Vector2i ofs;
	int line_height = 0;
	int line_length = 0;
	float line_stretch_ratio_total = 0;
	int current_container_size = vertical ? get_rect().size.y : get_rect().size.x;
	int children_in_current_line = 0;

	// First pass for line wrapping and minimum size calculation.
	for (int i = 0; i < get_child_count(); i++) {
		Control *child = Object::cast_to<Control>(get_child(i));
		if (!child || !child->is_visible()) {
			continue;
		}
		if (child->is_set_as_toplevel()) {
			continue;
		}

		Size2i child_msc = child->get_combined_minimum_size();

		if (vertical) { /* VERTICAL */
			if (children_in_current_line > 0) {
				ofs.y += separation_vertical;
			}
			if (ofs.y + child_msc.y > current_container_size) {
				line_length = ofs.y - separation_vertical;
				lines_data.push_back(_LineData{ children_in_current_line, line_height, line_length, current_container_size - line_length, line_stretch_ratio_total });

				// Move in new column (vertical line).
				ofs.x += line_height + separation_horizontal;
				ofs.y = 0;
				line_height = 0;
				line_stretch_ratio_total = 0;
				children_in_current_line = 0;
			}

			line_height = MAX(line_height, child_msc.x);
			if (child->get_v_size_flags() & SIZE_EXPAND) {
				line_stretch_ratio_total += child->get_stretch_ratio();
			}
			ofs.y += child_msc.y;

		} else { /* HORIZONTAL */
			if (children_in_current_line > 0) {
				ofs.x += separation_horizontal;
			}
			if (ofs.x + child_msc.x > current_container_size) {
				line_length = ofs.x - separation_horizontal;
				lines_data.push_back(_LineData{ children_in_current_line, line_height, line_length, current_container_size - line_length, line_stretch_ratio_total });

				// Move in new line.
				ofs.y += line_height + separation_vertical;
				ofs.x = 0;
				line_height = 0;
				line_stretch_ratio_total = 0;
				children_in_current_line = 0;
			}

			line_height = MAX(line_height, child_msc.y);
			if (child->get_h_size_flags() & SIZE_EXPAND) {
				line_stretch_ratio_total += child->get_stretch_ratio();
			}
			ofs.x += child_msc.x;
		}

		children_minsize_cache[child] = child_msc;
		children_in_current_line++;
	}
	line_length = vertical ? (ofs.y) : (ofs.x);
	lines_data.push_back(_LineData{ children_in_current_line, line_height, line_length, current_container_size - line_length, line_stretch_ratio_total });

	// Second pass for in-line expansion and alignment.

	int current_line_idx = 0;
	int child_idx_in_line = 0;

	ofs.x = 0;
	ofs.y = 0;

	for (int i = 0; i < get_child_count(); i++) {
		Control *child = Object::cast_to<Control>(get_child(i));
		if (!child || !child->is_visible()) {
			continue;
		}
		if (child->is_set_as_toplevel()) {
			continue;
		}
		Size2i child_size = children_minsize_cache[child];

		_LineData line_data = lines_data[current_line_idx];
		if (child_idx_in_line >= lines_data[current_line_idx].child_count) {
			current_line_idx++;
			child_idx_in_line = 0;
			if (vertical) {
				ofs.x += line_data.min_line_height + separation_horizontal;
				ofs.y = 0;
			} else {
				ofs.x = 0;
				ofs.y += line_data.min_line_height + separation_vertical;
			}
			line_data = lines_data[current_line_idx];
		}

		// The first child of each line adds the offset caused by the alignment,
		// but only if the line doesn't contain a child that expands.
		if (child_idx_in_line == 0 && Math::is_equal_approx(line_data.stretch_ratio_total, 0)) {
			int align_ofs = 0;
			switch (align) {
				case ALIGN_BEGIN:
					break;
				case ALIGN_CENTER:
					align_ofs = line_data.stretch_avail / 2;
					break;
				case ALIGN_END:
					align_ofs = line_data.stretch_avail;
					break;
			}

			if (vertical) { /* VERTICAL */
				ofs.y += align_ofs;
			} else { /* HORIZONTAL */
				ofs.x += align_ofs;
			}
		}

		if (vertical) { /* VERTICAL */
			if (child->get_h_size_flags() & (SIZE_FILL | SIZE_SHRINK_CENTER | SIZE_SHRINK_END)) {
				child_size.width = line_data.min_line_height;
			}

			if (child->get_v_size_flags() & SIZE_EXPAND) {
				int stretch = line_data.stretch_avail * child->get_stretch_ratio() / line_data.stretch_ratio_total;
				child_size.height += stretch;
			}

		} else { /* HORIZONTAL */
			if (child->get_v_size_flags() & (SIZE_FILL | SIZE_SHRINK_CENTER | SIZE_SHRINK_END)) {
				child_size.height = line_data.min_line_height;
			}

			if (child->get_h_size_flags() & SIZE_EXPAND) {
				int stretch = line_data.stretch_avail * child->get_stretch_ratio() / line_data.stretch_ratio_total;
				child_size.width += stretch;
			}
		}

		Rect2 child_rect = Rect2(ofs, child_size);
		fit_child_in_rect(child, child_rect);

		if (vertical) { /* VERTICAL */
			ofs.y += child_size.height + separation_vertical;
		} else { /* HORIZONTAL */
			ofs.x += child_size.width + separation_horizontal;
		}

		child_idx_in_line++;
	}
	cached_size = (vertical ? ofs.x : ofs.y) + line_height;
	cached_line_count = lines_data.size();
}

Size2 FlowContainer::get_minimum_size() const {
	Size2i minimum;

	for (int i = 0; i < get_child_count(); i++) {
		Control *c = Object::cast_to<Control>(get_child(i));
		if (!c) {
			continue;
		}
		if (c->is_set_as_toplevel()) {
			continue;
		}

		if (!c->is_visible()) {
			continue;
		}

		Size2i size = c->get_combined_minimum_size();

		if (vertical) { /* VERTICAL */
			minimum.height = MAX(minimum.height, size.height);
			minimum.width = cached_size;

		} else { /* HORIZONTAL */
			minimum.width = MAX(minimum.width, size.width);
			minimum.height = cached_size;
		}
	}

	return minimum;
}

void FlowContainer::_notification(int p_what) {
	switch (p_what) {
		case NOTIFICATION_SORT_CHILDREN: {
			_resort();
			minimum_size_changed();
		} break;
		case NOTIFICATION_THEME_CHANGED: {
			minimum_size_changed();
		} break;
		case NOTIFICATION_TRANSLATION_CHANGED: {
			queue_sort();
		} break;
	}
}

int FlowContainer::get_line_count() const {
	return cached_line_count;
}

void FlowContainer::set_alignment(AlignMode p_align) {
	if (align == p_align) {
		return;
	}
	align = p_align;
	_resort();
}

FlowContainer::AlignMode FlowContainer::get_alignment() const {
	return align;
}

FlowContainer::FlowContainer(bool p_vertical) {
	vertical = p_vertical;
	align = ALIGN_BEGIN;
	cached_size = 0;
	cached_line_count = 0;
}

void FlowContainer::_bind_methods() {
	ClassDB::bind_method(D_METHOD("get_line_count"), &FlowContainer::get_line_count);
	ClassDB::bind_method(D_METHOD("get_alignment"), &FlowContainer::get_alignment);
	ClassDB::bind_method(D_METHOD("set_alignment", "alignment"), &FlowContainer::set_alignment);

	BIND_ENUM_CONSTANT(ALIGN_BEGIN);
	BIND_ENUM_CONSTANT(ALIGN_CENTER);
	BIND_ENUM_CONSTANT(ALIGN_END);

	ADD_PROPERTY(PropertyInfo(Variant::INT, "alignment", PROPERTY_HINT_ENUM, "Begin,Center,End"), "set_alignment", "get_alignment");
}