/*
This Source Code Form is subject to the
terms of the Mozilla Public License, v.
2.0. If a copy of the MPL was not
distributed with this file, You can
obtain one at
http://mozilla.org/MPL/2.0/.
*/

#include "stdafx.h"
#include "application/editormode.h"
#include "application/editoruilayer.h"
#include "application/editorprojection.h"
#include "application/editormodeshared.h"
#include "editor/editorFormat.hpp"
#include "editor/editorAlignmentStore.hpp"
#include "editor/editorSwitchStore.hpp"
#include "editor/editorGeometry.hpp"

#include "world/Track.h"
#include "utilities/translation.h"

#include "imgui/imgui.h"
#include <algorithm>
#include <array>
#include <optional>
#include <tuple>

namespace
{

using geometry::bezier;
using geometry::has_controls;
using geometry::cross;
using geometry::grade_of;
using geometry::plan_distance;
using geometry::plan_of;

struct switch_end_move
{
	glm::dvec3 from{0.0};
	glm::dvec3 to{0.0};
	double shift{0.0};
};

std::optional<std::vector<switch_end_move>> switch_end_moves(TTrack const &Track, segment_data const &Main, bool const Online, std::pair<double, double> const &Room, double const Offset, std::string &Status)
{
	auto const axis{editor_track::main_axis(Track)};
	std::vector<switch_end_move> ends;
	for (auto const index : {segment_data::point::start, segment_data::point::end})
	{
		auto const from{Track.m_paths.front().points[index]};
		auto const to{Main.points[index]};
		if (false == Online || glm::distance(from, to) < 0.005 || axis->lateral(to) > Offset)
			continue;
		auto const target{axis->along(to)};
		if (target < Room.first - 0.01 || target > Room.second + 0.01)
		{
			Status = STR_C("The switch would run into another switch or past the end of the straight");
			return std::nullopt;
		}
		ends.push_back({from, to, index == segment_data::point::start ? axis->along(from) - target : target - axis->along(from)});
	}
	std::stable_sort(ends.begin(), ends.end(), [](switch_end_move const &A, switch_end_move const &B) { return A.shift > B.shift; });
	return ends;
}

std::string switch_rejoin(TTrack &Track, std::vector<editor_track::joint> const &Joints, std::vector<bool> const &Handled, editor_track::edit &Edit)
{
	std::vector<editor_track::joint> following;
	std::string loose;
	for (std::size_t i = 0; i < Joints.size(); ++i)
	{
		auto const &joint{Joints[i]};
		if (Handled[i] || joint.other->m_editorremoved)
			continue;
		auto const &theirs{joint.other->m_paths[joint.theirs.path]};
		auto const shift{glm::distance(editor_track::point_position(Track, joint.own), editor_track::point_position(*joint.other, joint.theirs))};
		if (shift > 0.3 * bezier{theirs}.plan_length())
		{
			loose += (loose.empty() ? "" : ", ") + name_of(*joint.other);
			continue;
		}
		following.push_back(joint);
		Edit.capture(*joint.other);
	}
	editor_track::follow(Track, following);
	return loose;
}

double constexpr kBranchStraight{500.0}; // how far the straight past the curve next to a switch is followed

// direction out of the path at the end
glm::dvec3 end_outward(segment_data const &Path, bool const Atend)
{
	bezier const curve{Path};
	auto direction{Atend ? curve.first(1.0) : -curve.first(0.0)};
	if (glm::length(plan_of(direction)) < 1e-9)
		direction = Atend ? curve.p3 - curve.p0 : curve.p0 - curve.p3;
	return direction;
}

// straight from the start of the line to its first curve
double opening(alignment::result const &Result)
{
	return Result.elements.empty() || Result.elements.front().kind != alignment::element_kind::straight ? 0.0 : Result.elements.front().length;
}

// straight from the last curve of the line to its end
double closing(alignment::result const &Result)
{
	return Result.elements.empty() || Result.elements.back().kind != alignment::element_kind::straight ? 0.0 : Result.elements.back().length;
}

alignment::vertex scaled(alignment::vertex Vertex, double const Factor)
{
	Vertex.radius *= Factor;
	Vertex.transition_in *= Factor;
	Vertex.transition_out *= Factor;
	for (auto &arc : Vertex.arcs)
	{
		arc.radius *= Factor;
		arc.transition *= Factor;
	}
	return Vertex;
}

// where the path of the index leaves the chain
glm::dvec3 exit_of(editor_track::chain const &Chain, std::size_t const Index)
{
	auto const &path{Chain.tracks[Index]->m_paths.front()};
	return path.points[Chain.forward[Index] ? segment_data::point::end : segment_data::point::start];
}

// raises the pieces by Rise at their start, less and less up to nothing at their end
void lift(std::vector<segment_data> &Pieces, double const Rise)
{
	std::vector<double> lengths;
	double total{0.0};
	for (auto const &piece : Pieces)
	{
		lengths.push_back(bezier{piece}.plan_length());
		total += lengths.back();
	}
	if (total <= 1e-6 || std::abs(Rise) <= 1e-6)
		return;
	auto const slope{Rise / total};
	double along{0.0};
	for (std::size_t i = 0; i < Pieces.size(); ++i)
	{
		auto &points{Pieces[i].points};
		auto const controls{has_controls(Pieces[i])};
		points[segment_data::point::start].y += Rise - slope * along;
		points[segment_data::point::end].y += Rise - slope * (along + lengths[i]);
		// the controls are kept from their ends
		if (controls)
		{
			points[segment_data::point::control1].y -= slope * glm::length(plan_of(points[segment_data::point::control1]));
			points[segment_data::point::control2].y += slope * glm::length(plan_of(points[segment_data::point::control2]));
		}
		along += lengths[i];
	}
}

} // namespace

bool editor_mode::switch_room(TTrack &Track, double &Low, double &High, std::string &Reason)
{
	Low = 0.0;
	High = 0.0;
	if (Track.eType != tt_Switch || Track.m_paths.size() < 2 || has_controls(Track.m_paths.front()))
		return false;
	auto const axis{editor_track::main_axis(Track)};
	if (false == axis.has_value())
		return false;
	auto const line{editor_track::find_straight(Track, m_straights.tolerance)};
	if (false == tracks_editable(line.tracks, Reason))
		return false;
	std::vector<std::tuple<double, double, bool>> spans;
	for (std::size_t i = 0; i < line.tracks.size(); ++i)
	{
		if (line.tracks[i] == &Track)
			continue;
		auto const &path{line.tracks[i]->m_paths[line.paths[i]]};
		auto const a{axis->along(path.points[segment_data::point::start])};
		auto const b{axis->along(path.points[segment_data::point::end])};
		spans.emplace_back(std::min(a, b), std::max(a, b), line.tracks[i]->eType == tt_Normal);
	}
	std::sort(spans.begin(), spans.end());
	double low{0.0};
	double high{axis->length};
	for (auto const &[from, to, plain] : spans)
		if (from > axis->length - 0.01)
		{
			if (false == plain || from > high + 0.01)
				break;
			high = std::max(high, to);
		}
	for (auto span{spans.rbegin()}; span != spans.rend(); ++span)
	{
		auto const &[from, to, plain] = *span;
		if (to < 0.01)
		{
			if (false == plain || to < low - 0.01)
				break;
			low = std::min(low, from);
		}
	}
	Low = low;
	High = high;
	return true;
}

bool editor_mode::switch_vacate(TTrack &Track, glm::dvec3 const &From, glm::dvec3 const &To, double const Shift, editor_track::straight const &Line, editor_track::edit &Edit, std::string &Status)
{
	if (Shift > 0.0)
	{
		auto const a{Line.along(From)};
		auto const b{Line.along(To)};
		if (cut_straight(Line, std::min(a, b), std::max(a, b), Edit.states, Edit.created, Edit.removed, nullptr))
			return true;
		Status = STR_C("The switch would overlap another switch, move it onto plain track");
		return false;
	}
	TTrack const *style{nullptr};
	bool filler{false};
	for (auto const &[other, point] : editor_track::connected_points(Track, From))
	{
		if (other->m_editorremoved)
			continue;
		if (other->eType == tt_Normal && std::find(Line.tracks.begin(), Line.tracks.end(), other) != Line.tracks.end())
		{
			Edit.capture(*other);
			editor_track::move_point(*other, point, To);
			continue;
		}
		filler = true;
		if (style == nullptr && other->eType == tt_Normal)
			style = other;
	}
	if (filler)
	{
		segment_data path;
		path.points[segment_data::point::start] = To;
		path.points[segment_data::point::end] = From;
		auto *piece{editor_track::create_path(style != nullptr ? *style : Track, path)};
		Edit.created.push_back(piece);
		Edit.changed.push_back(piece);
	}
	return true;
}

std::optional<editor_mode::switch_branch> editor_mode::take_switch_branch(TTrack const &Track, editor_track::joint const &Joint, std::size_t const Index) const
{
	auto *first{Joint.other};
	if (first == nullptr || first->eType != tt_Normal || first->m_paths.empty())
		return std::nullopt;
	auto const category{first->iCategoryFlag & 15};
	auto const regular = [&](TTrack const *Other) { return Other != nullptr && Other->eType == tt_Normal && false == Other->m_editorremoved && editor_track::is_supported(*Other) && (Other->iCategoryFlag & 15) == category; };
	// from the switch on: a straight up to the curve maybe, the curve, the straight past it
	std::vector<TTrack *> run;
	auto *current{first};
	auto atstart{Joint.theirs.kind == editor_track::point_kind::start};
	int phase{0};
	std::size_t straight{0};
	double past{0.0};
	while (regular(current) && std::find(run.begin(), run.end(), current) == run.end() && past < kBranchStraight)
	{
		auto const plain{editor_track::is_straight(*current, m_straights.tolerance)};
		if (false == plain && phase == 2)
			break;
		if (false == plain)
			phase = 1;
		else if (phase == 1)
		{
			phase = 2;
			straight = run.size();
		}
		if (phase == 2)
			past += current->Length();
		run.push_back(current);
		auto *next{atstart ? current->trNext : current->trPrev};
		if (next == nullptr || (next->trPrev != current && next->trNext != current))
			break;
		atstart = next->trPrev == current;
		current = next;
	}
	if (phase != 2)
		return std::nullopt;
	switch_branch branch;
	branch.joint = Index;
	branch.straight = straight;
	std::string error;
	auto &chain{branch.chain};
	if (false == editor_track::find_chain(run.front(), run.back(), chain, error) || chain.tracks != run || plan_distance(chain.start, editor_track::point_position(Track, Joint.own)) > geometry::same_point)
		return std::nullopt;
	auto &design{branch.design};
	design.norms = m_route.design.norms;
	design.shape = m_route.design.shape;
	design.transition_pieces = m_route.design.transition_pieces;
	design.speed = chain.velocity > 0.0 ? chain.velocity : 100.0;
	if (auto const hit{alignment_store::on_track(*run[straight - 1])})
	{
		auto const &stored{alignment_store::records()[hit->record].design};
		design.norms = stored.norms;
		design.shape = stored.shape;
		design.transition_pieces = stored.transition_pieces;
		design.arc_piece_angle = stored.arc_piece_angle;
		design.speed = stored.speed;
	}
	design.norms.checked = false;
	auto const found{editor_track::recognize_line(chain, m_straights.tolerance, design.norms.gauge, design.shape)};
	if (found.size() != 1 || found.front().kink)
		return std::nullopt;
	design.start = chain.start;
	design.end = chain.end;
	design.start_direction = glm::normalize(plan_of(chain.start_direction));
	design.end_direction = glm::normalize(plan_of(chain.end_direction));
	design.start_grade = grade_of(chain.start_direction);
	design.end_grade = grade_of(chain.end_direction);
	auto vertex{route_vertex_of(found.front().shape)};
	vertex.position = found.front().position;
	design.vertices = {vertex};
	branch.result = alignment::compute(design);
	if (false == branch.result.valid)
		return std::nullopt;
	return branch;
}

bool editor_mode::plan_switch_branch(segment_data const &Path, editor_track::joint const &Joint, switch_branch &Branch) const
{
	auto const atend{Joint.own.kind == editor_track::point_kind::end};
	auto const start{Path.points[atend ? segment_data::point::end : segment_data::point::start]};
	auto const outward{end_outward(Path, atend)};
	auto laid{Branch.design};
	laid.start = start;
	laid.start_direction = glm::normalize(plan_of(outward));
	laid.start_grade = grade_of(outward);
	auto const original{Branch.design.vertices.front()};
	auto const make = [&](double const Factor) {
		laid.vertices = {scaled(original, Factor)};
		return alignment::compute(laid);
	};
	// compute() makes the curve tighter when it doesn't fit between the ends
	auto const fits = [&](alignment::result const &Result) { return Result.valid && false == Result.curves.empty() && Result.curves.front().radius >= laid.vertices.front().radius * (1.0 - 1e-6); };
	double factor{1.0};
	auto result{make(factor)};
	if (false == result.valid || result.curves.empty())
		return false;
	if (false == fits(result))
	{
		// the design keeps the curve the way it was made to fit
		auto &vertex{laid.vertices.front()};
		auto const &report{result.curves.front()};
		auto const reduced{report.radius / vertex.radius};
		if (vertex.compound)
			vertex = scaled(vertex, reduced);
		else
		{
			vertex.radius = report.radius;
			vertex.transition_in = report.transition_in;
			vertex.transition_out = report.transition_out;
		}
		factor = reduced;
		result = alignment::compute(laid);
		if (false == result.valid)
			return false;
	}
	else if (opening(Branch.result) < 0.1 && opening(result) >= 0.1)
	{
		// the curve which adjoined the switch keeps to it: the largest one which fits
		double low{1.0};
		double high{1.5};
		while (fits(make(high)) && high < 5.0)
			high *= 1.5;
		if (fits(make(high)))
			return false;
		for (int i = 0; i < 40; ++i)
		{
			auto const middle{0.5 * (low + high)};
			(fits(make(middle)) ? low : high) = middle;
		}
		factor = low;
		result = make(factor);
		if (false == result.valid)
			return false;
	}
	// the paths are laid up to the first joint on the straight past the old and the new curve
	auto const &chain{Branch.chain};
	auto const end{plan_of(chain.end)};
	auto const behind = [&](glm::dvec3 const &Point) { return glm::dot(end - plan_of(Point), laid.end_direction); };
	auto const curveend{closing(result)};
	auto last{chain.tracks.size()};
	for (auto k{Branch.straight - 1}; k < chain.tracks.size(); ++k)
		if (behind(exit_of(chain, k)) <= curveend - 0.5)
		{
			last = k;
			break;
		}
	if (last == chain.tracks.size())
		return false;
	auto part{laid};
	auto const joint{exit_of(chain, last)};
	part.end = joint;
	part.end_grade = grade_of(end_outward(chain.tracks[last]->m_paths.front(), chain.forward[last]));
	auto const partresult{alignment::compute(part)};
	if (false == partresult.valid)
		return false;
	Branch.part = {};
	Branch.part.tracks.assign(chain.tracks.begin(), chain.tracks.begin() + last + 1);
	Branch.part.forward.assign(chain.forward.begin(), chain.forward.begin() + last + 1);
	Branch.part.start = chain.start;
	Branch.part.end = joint;
	Branch.pieces = alignment::pieces(partresult, part, last + 1);
	if (Branch.pieces.size() < last + 1)
		return false;
	editor_track::keep_heights(Branch.part, Branch.pieces);
	lift(Branch.pieces, start.y - chain.start.y);
	Branch.pieces.front().points[segment_data::point::start] = start;
	Branch.pieces.back().points[segment_data::point::end] = joint;
	Branch.laid = laid;
	Branch.factor = factor;
	return true;
}

void editor_mode::lay_switch_branch(switch_branch const &Branch, editor_track::edit &Edit)
{
	for (auto *track : Branch.part.tracks)
		Edit.capture(*track);
	auto const created{editor_track::relay(Branch.part, Branch.pieces)};
	Edit.created.insert(Edit.created.end(), created.begin(), created.end());
	// the design kept for the line starting or ending at the switch follows it
	auto const &records{alignment_store::records()};
	auto const from{Branch.chain.start};
	auto const joint{Branch.part.end};
	for (std::size_t i = 0; i < records.size(); ++i)
	{
		auto const &record{records[i]};
		if (false == record.whole())
			continue;
		auto const atstart{plan_distance(record.design.start, from) < geometry::same_point};
		if (false == atstart && plan_distance(record.design.end, from) >= geometry::same_point)
			continue;
		auto design{record.design};
		auto &vertices{design.vertices};
		if (vertices.empty())
			return;
		auto const outward{Branch.laid.start_direction};
		auto const k{atstart ? std::size_t{0} : vertices.size() - 1};
		if (atstart)
		{
			design.start = Branch.laid.start;
			design.start_direction = outward;
			design.start_grade = Branch.laid.start_grade;
		}
		else
		{
			design.end = Branch.laid.start;
			design.end_direction = -outward;
			design.end_grade = -Branch.laid.start_grade;
		}
		auto const &corners{record.result.vertices};
		if (vertices.size() >= 2 && corners.size() == vertices.size())
		{
			// the corner moves along its other leg to the line from the switch
			auto const corner{corners[k]};
			auto const leg{corners[atstart ? 1 : k - 1] - corner};
			auto const determinant{cross(outward, leg)};
			if (std::abs(determinant) < 1e-9)
				return;
			auto const offset{cross(corner - plan_of(Branch.laid.start), leg) / determinant};
			if (offset <= 0.0)
				return;
			vertices[k].offset = offset;
		}
		// the curve next to the switch takes the shape it was laid with
		auto const &shape{Branch.laid.vertices.front()};
		if (shape.compound || vertices[k].compound)
			vertices[k] = scaled(vertices[k], Branch.factor);
		else
		{
			vertices[k].radius = shape.radius;
			vertices[k].transition_in = atstart ? shape.transition_in : shape.transition_out;
			vertices[k].transition_out = atstart ? shape.transition_out : shape.transition_in;
		}
		auto const result{alignment::compute(design)};
		if (false == result.valid || false == alignment_store::follows(result, Branch.part.tracks))
			return;
		// the km of the joint the paths are laid up to stays as it was
		auto origin{record.origin};
		if (atstart)
		{
			auto const before{alignment_store::chainage_on(record.result, joint)};
			auto const after{alignment_store::chainage_on(result, joint)};
			if (before.has_value() && after.has_value())
				origin += *before - *after;
		}
		auto const layer{record.layer};
		auto const source{record.source};
		auto const fit{record.fit};
		alignment_store::forget(static_cast<int>(i));
		alignment_store::store(design, result, origin, layer, source, fit);
		return;
	}
}

bool editor_mode::move_switch_paths(TTrack &Track, std::vector<segment_data> const &Paths, std::string &Status)
{
	if (Paths.size() < 2 || Track.m_paths.size() < 2 || false == editor_track::main_axis(Track).has_value())
		return false;
	double low{0.0};
	double high{0.0};
	std::string reason;
	bool const online{switch_room(Track, low, high, reason)};
	if (false == online && false == reason.empty())
	{
		Status = reason;
		return false;
	}
	auto const ends{switch_end_moves(Track, Paths.front(), online, {low, high}, m_straights.tolerance.offset, Status)};
	if (false == ends.has_value())
		return false;
	auto const joints{editor_track::joints(Track)};
	std::vector<glm::dvec3> positions;
	for (auto const &joint : joints)
		positions.push_back(editor_track::point_position(Track, joint.own));
	std::vector<bool> handled(joints.size(), false);
	auto branches{switch_branches(Track, joints)};
	editor_track::edit edit;
	edit.capture(Track);
	auto const line{online ? editor_track::find_straight(Track, m_straights.tolerance) : editor_track::straight{}};
	for (auto const &end : *ends)
	{
		for (std::size_t i = 0; i < joints.size(); ++i)
			if (glm::distance(positions[i], end.from) < geometry::same_point)
				handled[i] = true;
		if (false == switch_vacate(Track, end.from, end.to, end.shift, line, edit, Status))
			return false;
	}
	Track.m_paths.assign(Paths.begin(), Paths.begin() + 2);
	auto const notes{plan_switch_branches(Track, joints, branches, handled)};
	auto const loose{switch_rejoin(Track, joints, handled, edit)};
	editor_track::commit(edit.changed);
	for (auto const &branch : branches)
		lay_switch_branch(branch, edit);
	push_track_snapshot(std::move(edit.states), std::move(edit.created), std::move(edit.removed));
	if (false == loose.empty())
		Status = STR_C("Too far from the new ends of the switch, left unjoined: ") + loose;
	if (false == notes.empty())
		Status += (Status.empty() ? "" : "\n") + notes;
	return true;
}

std::vector<editor_mode::switch_branch> editor_mode::switch_branches(TTrack const &Track, std::vector<editor_track::joint> const &Joints, std::vector<TTrack const *> const &Skip) const
{
	std::vector<switch_branch> branches;
	auto const axis{editor_track::main_axis(Track)};
	if (false == axis.has_value())
		return branches;
	for (std::size_t i = 0; i < Joints.size(); ++i)
	{
		if (std::find(Skip.begin(), Skip.end(), Joints[i].other) != Skip.end() || axis->lateral(editor_track::point_position(Track, Joints[i].own)) <= m_straights.tolerance.offset)
			continue;
		if (auto branch{take_switch_branch(Track, Joints[i], i)})
			branches.push_back(std::move(*branch));
	}
	return branches;
}

std::string editor_mode::plan_switch_branches(TTrack const &Track, std::vector<editor_track::joint> const &Joints, std::vector<switch_branch> &Branches, std::vector<bool> &Handled) const
{
	std::string notes;
	for (auto branch{Branches.begin()}; branch != Branches.end();)
	{
		auto const &joint{Joints[branch->joint]};
		std::string reason;
		if (false == plan_switch_branch(Track.m_paths[joint.own.path], joint, *branch) || false == tracks_editable(branch->part.tracks, reason))
		{
			notes += (notes.empty() ? "" : "\n") + format(STR_C("The curve past the end of the switch can't keep to it, %s follows the switch on its own"), name_of(*joint.other).c_str());
			branch = Branches.erase(branch);
			continue;
		}
		Handled[branch->joint] = true;
		if (std::abs(branch->factor - 1.0) > 1e-4)
			notes += (notes.empty() ? "" : "\n") + format(STR_C("The curve past the end of the switch keeps to it with the radius of %.1f m instead of %.1f m"), branch->laid.vertices.front().radius, branch->design.vertices.front().radius);
		++branch;
	}
	return notes;
}

bool editor_mode::double_room(double_switch const &Set, double &Low, double &High, double &Length, std::string &Reason)
{
	double low{0.0};
	double high{0.0};
	double low2{0.0};
	double high2{0.0};
	auto const axis{editor_track::main_axis(*Set.first)};
	if (false == axis.has_value() || false == switch_room(*Set.first, low, high, Reason) || false == switch_room(*Set.second, low2, high2, Reason))
		return false;
	auto const &main{Set.second->m_paths.front()};
	Low = low;
	High = axis->along(main.points[segment_data::point::start]) + high2;
	Length = axis->along(main.points[segment_data::point::end]);
	return true;
}

bool editor_mode::move_double_paths(double_switch const &Set, std::vector<segment_data> const &Paths, std::string &Status)
{
	auto const axis{editor_track::main_axis(*Set.first)};
	if (Paths.size() < 5 || false == axis.has_value())
		return false;
	double low{0.0};
	double high{0.0};
	double length{0.0};
	std::string reason;
	bool const online{double_room(Set, low, high, length, reason)};
	if (false == online && false == reason.empty())
	{
		Status = reason;
		return false;
	}
	struct outer_end
	{
		TTrack *track{nullptr};
		switch_end_move move;
	};
	std::vector<outer_end> ends;
	auto const outer = [&](TTrack &Track, glm::dvec3 const &From, glm::dvec3 const &To, bool const Atstart) {
		if (false == online || glm::distance(From, To) < 0.005 || axis->lateral(To) > m_straights.tolerance.offset)
			return true;
		auto const target{axis->along(To)};
		if (target < low - 0.01 || target > high + 0.01)
		{
			Status = STR_C("The switch would run into another switch or past the end of the straight");
			return false;
		}
		ends.push_back({&Track, {From, To, Atstart ? axis->along(From) - target : target - axis->along(From)}});
		return true;
	};
	if (false == outer(*Set.first, Set.first->m_paths.front().points[segment_data::point::start], Paths[0].points[segment_data::point::start], true) ||
	    false == outer(*Set.second, Set.second->m_paths.front().points[segment_data::point::end], Paths[2].points[segment_data::point::end], false))
		return false;
	std::stable_sort(ends.begin(), ends.end(), [](outer_end const &A, outer_end const &B) { return A.move.shift > B.move.shift; });
	std::array<TTrack *, 2> const switches{Set.first, Set.second};
	std::array<std::vector<editor_track::joint>, 2> joints;
	std::array<std::vector<glm::dvec3>, 2> positions;
	std::array<std::vector<bool>, 2> handled;
	for (std::size_t k = 0; k < 2; ++k)
	{
		joints[k] = editor_track::joints(*switches[k]);
		for (auto const &joint : joints[k])
		{
			positions[k].push_back(editor_track::point_position(*switches[k], joint.own));
			handled[k].push_back(joint.other == Set.link || joint.other == Set.first || joint.other == Set.second);
		}
	}
	auto const joint{Set.first->m_paths.front().points[segment_data::point::end]};
	auto const &link{Set.link->m_paths.front()};
	bool const reversed{glm::distance(link.points[segment_data::point::start], joint) > glm::distance(link.points[segment_data::point::end], joint)};
	std::array<std::vector<switch_branch>, 2> branches;
	for (std::size_t k = 0; k < 2; ++k)
		branches[k] = switch_branches(*switches[k], joints[k], {Set.first, Set.link, Set.second});
	editor_track::edit edit;
	for (auto *track : {Set.first, Set.link, Set.second})
		edit.capture(*track);
	for (auto const &end : ends)
	{
		for (std::size_t k = 0; k < 2; ++k)
			for (std::size_t i = 0; i < joints[k].size(); ++i)
				if (glm::distance(positions[k][i], end.move.from) < geometry::same_point)
					handled[k][i] = true;
		auto const line{editor_track::find_straight(*end.track, m_straights.tolerance)};
		if (false == switch_vacate(*end.track, end.move.from, end.move.to, end.move.shift, line, edit, Status))
			return false;
	}
	Set.first->m_paths.assign(Paths.begin(), Paths.begin() + 2);
	Set.second->m_paths.assign(Paths.begin() + 2, Paths.begin() + 4);
	Set.link->m_paths = {reversed ? geometry::reversed(Paths[4]) : Paths[4]};
	std::string notes;
	for (std::size_t k = 0; k < 2; ++k)
	{
		auto const note{plan_switch_branches(*switches[k], joints[k], branches[k], handled[k])};
		if (false == note.empty())
			notes += (notes.empty() ? "" : "\n") + note;
	}
	std::string loose;
	for (std::size_t k = 0; k < 2; ++k)
	{
		auto const left{switch_rejoin(*switches[k], joints[k], handled[k], edit)};
		if (false == left.empty())
			loose += (loose.empty() ? "" : ", ") + left;
	}
	editor_track::commit(edit.changed);
	for (auto const &set : branches)
		for (auto const &branch : set)
			lay_switch_branch(branch, edit);
	push_track_snapshot(std::move(edit.states), std::move(edit.created), std::move(edit.removed));
	if (false == loose.empty())
		Status = STR_C("Too far from the new ends of the switch, left unjoined: ") + loose;
	if (false == notes.empty())
		Status += (Status.empty() ? "" : "\n") + notes;
	return true;
}

bool editor_mode::slip_room(slip_set const &Slip, slip_slide &Slide, std::string &Reason) const
{
	Slide = slip_slide{};
	Reason.clear();
	// one laid out of straights only, along its first one
	for (auto const *part : Slip.switches)
		if (has_controls(part->m_paths.front()))
		{
			Reason = STR_C("A slip bent into a curve isn't slid along it: delete it and lay it again");
			return false;
		}
	if (false == tracks_editable(Slip.parts, Reason))
		return false;
	auto const chord{Slip.ends[1] - Slip.ends[0]};
	auto const run{glm::length(plan_of(chord))};
	if (run < 1e-6)
		return false;
	Slide.shift = chord / run;
	Slide.movers = Slip.parts;
	auto const outside = [&](TTrack const *Track) { return std::find(Slip.parts.begin(), Slip.parts.end(), Track) == Slip.parts.end(); };
	// its crossing track goes along where it goes on into tracks ending free, as when it was laid on one straight
	for (std::size_t end = 2; end < 4; ++end)
	{
		for (auto const *part : Slip.parts)
			for (auto const &[other, point] : editor_track::connected_points(*part, Slip.ends[end]))
			{
				if (false == outside(other) || std::find(Slide.movers.begin(), Slide.movers.end(), other) != Slide.movers.end())
					continue;
				auto const free{other->eType == tt_Normal && other->m_paths.size() == 1 &&
				                editor_track::connected_points(*other, editor_track::point_position(*other, {point.path, point.kind == editor_track::point_kind::start ? editor_track::point_kind::end : editor_track::point_kind::start})).empty()};
				if (false == free)
				{
					Reason = STR_C("The crossing track of the slip is joined on beyond it: the slip stays where the two tracks cross");
					return false;
				}
				Slide.movers.push_back(other);
			}
	}
	// the straights of its first track out to the joints of its template, as long as the ones of its crossing track going along, go
	// along too, the joints with them
	auto const extension{Slide.movers.size() > Slip.parts.size() ? geometry::chord_length(Slide.movers.back()->m_paths.front()) : 0.0};
	auto const straight_along = [&](TTrack const &Track) {
		return Track.eType == tt_Normal && Track.m_paths.size() == 1 && false == has_controls(Track.m_paths.front()) &&
		       std::abs(geometry::cross(glm::normalize(plan_of(Track.m_paths.front().points[segment_data::point::end] - Track.m_paths.front().points[segment_data::point::start])), plan_of(Slide.shift))) < 1e-3;
	};
	std::array<glm::dvec3, 2> joints{Slip.ends[0], Slip.ends[1]};
	for (std::size_t end = 0; end < 2 && extension > 0.0; ++end)
		for (auto const *part : Slip.parts)
			for (auto const &[other, point] : editor_track::connected_points(*part, Slip.ends[end]))
				if (outside(other) && straight_along(*other) && std::abs(geometry::chord_length(other->m_paths.front()) - extension) < 0.01 &&
				    std::find(Slide.movers.begin(), Slide.movers.end(), other) == Slide.movers.end())
				{
					Slide.movers.push_back(other);
					joints[end] = editor_track::point_position(*other, {point.path, point.kind == editor_track::point_kind::start ? editor_track::point_kind::end : editor_track::point_kind::start});
				}
	Slide.joints = joints;
	// the straights of its first track before it and past it give and take the length, a metre of them kept at least
	double room[2]{1e4, 1e4};
	bool straight[2]{true, true};
	for (std::size_t end = 0; end < 2; ++end)
		for (auto *track : Slide.movers)
			for (auto const &[other, point] : editor_track::connected_points(*track, joints[end]))
			{
				if (std::find(Slide.movers.begin(), Slide.movers.end(), other) != Slide.movers.end() || Slide.ends[end].first != nullptr)
					continue;
				Slide.ends[end] = {other, point};
				straight[end] = straight_along(*other);
				room[end] = straight[end] ? geometry::chord_length(other->m_paths.front()) - 1.0 : 0.0;
			}
	// back, it shortens the track before it and lengthens the one past it; on, the other way
	Slide.low = straight[1] ? -std::max(0.0, room[0]) : 0.0;
	Slide.high = straight[0] ? std::max(0.0, room[1]) : 0.0;
	return true;
}

bool editor_mode::slide_slip(slip_set const &Slip, double const Distance)
{
	slip_slide slide;
	std::string reason;
	if (false == slip_room(Slip, slide, reason))
	{
		m_switch.status = refused(reason);
		ui()->set_status(m_switch.status, true);
		return false;
	}
	auto const distance{std::clamp(Distance, slide.low, slide.high)};
	if (std::abs(distance) < 0.005)
		return false;
	auto const shift{slide.shift * distance};
	std::vector<std::pair<TTrack *, editor_track::state>> states;
	std::vector<TTrack *> changed;
	for (auto *mover : slide.movers)
	{
		states.emplace_back(mover, editor_track::capture(*mover));
		for (auto &path : mover->m_paths)
			path.translate(shift);
		changed.push_back(mover);
	}
	for (std::size_t end = 0; end < 2; ++end)
		if (auto const &[other, point]{slide.ends[end]}; other != nullptr)
		{
			states.emplace_back(other, editor_track::capture(*other));
			editor_track::move_point(*other, point, slide.joints[end] + shift);
			changed.push_back(other);
		}
	editor_track::commit(changed);
	push_track_snapshot(std::move(states), {}, {});
	switch_store::follow();
	records_to_history();
	straight_refresh();
	m_switch.status = format(STR_C("Slip %s moved %.2f m along its track, its crossing track with it"), Slip.record.name.c_str(), distance);
	ui()->set_status(m_switch.status, false);
	return true;
}

bool editor_mode::bent_switch_frame(TTrack const &Track, std::vector<curve_sample> &Frame, std::array<TTrack *, 2> &Sides, double &Station) const
{
	Frame.clear();
	Sides = {nullptr, nullptr};
	if (Track.eType != tt_Switch || Track.m_paths.size() != 2 || Track.m_editorremoved || false == has_controls(Track.m_paths.front()) || slip_of(Track).has_value() || double_of(Track).has_value() ||
	    crossover_of(Track).has_value())
		return false;
	// the plain tracks the main track goes on into, each run towards the end of the switch it joins: the one before into its start, the
	// one past it out of its end
	std::array<bool, 2> forward{true, true};
	for (auto const &joint : editor_track::joints(Track))
	{
		if (joint.own.path != 0 || joint.other == nullptr || joint.other->eType != tt_Normal || joint.other->m_editorremoved || joint.other->m_paths.size() != 1)
			continue;
		auto const past{joint.own.kind == editor_track::point_kind::end ? 1 : 0};
		Sides[past] = joint.other;
		forward[past] = (joint.theirs.kind == editor_track::point_kind::end) == (past == 0);
	}
	if (Sides[0] == nullptr || Sides[1] == nullptr || Sides[0] == Sides[1])
		return false;
	editor_track::chain chain;
	chain.tracks = {Sides[0], const_cast<TTrack *>(&Track), Sides[1]};
	chain.forward = {forward[0], true, forward[1]};
	Frame = sample_chain(chain);
	Station = nearest_station(Frame, Track.m_paths.front().points[segment_data::point::start]);
	return Frame.size() >= 2;
}

std::vector<segment_data> editor_mode::bent_switch_paths(TTrack const &Track, std::vector<curve_sample> const &Frame, double const Station, double const Distance) const
{
	// a path as seen from the curve where the switch starts: across it, over it, along it, as frame_path takes a path of a template
	auto const local_end = [&](glm::dvec3 const &World, glm::dvec3 const &Control, glm::dvec3 &Point, glm::dvec3 &Localcontrol) {
		auto const at{nearest_station(Frame, World)};
		auto const sample{sample_at(Frame, at)};
		glm::dvec2 const across{-sample.tangent.y, sample.tangent.x};
		auto const lateral{glm::dot(plan_of(World) - plan_of(sample.position), across)};
		Point = {lateral, World.y - sample.position.y + lateral * std::tan(glm::radians(static_cast<double>(sample.roll))), at - Station};
		auto const planar{plan_of(Control)};
		Localcontrol = glm::length(planar) > 1e-9 ? glm::dvec3{glm::dot(planar, across), Control.y, glm::dot(planar, sample.tangent)} : glm::dvec3{0.0};
	};
	auto const localized = [&](segment_data const &Path) {
		auto local{Path};
		local.pieces.clear();
		local_end(Path.points[segment_data::point::start], Path.points[segment_data::point::control1], local.points[segment_data::point::start], local.points[segment_data::point::control1]);
		local_end(Path.points[segment_data::point::end], Path.points[segment_data::point::control2], local.points[segment_data::point::end], local.points[segment_data::point::control2]);
		return local;
	};
	std::vector<segment_data> result;
	for (std::size_t i = 0; i < Track.m_paths.size(); ++i)
	{
		auto const &own{Track.m_paths[i]};
		auto path{frame_path(localized(own), Frame, Station + Distance, 1, 1)};
		for (auto const &piece : own.pieces)
			path.pieces.push_back(frame_path(localized(piece), Frame, Station + Distance, 1, 1));
		// the main track follows the curve it lies in
		if (i == 0)
			path.radius = own.radius;
		result.push_back(path);
	}
	return result;
}

bool editor_mode::slide_bent_switch(TTrack &Track, double const Distance)
{
	std::vector<curve_sample> frame;
	std::array<TTrack *, 2> sides;
	double station;
	if (false == bent_switch_frame(Track, frame, sides, station))
		return false;
	auto const &main{Track.m_paths.front()};
	auto const length{nearest_station(frame, main.points[segment_data::point::end]) - station};
	// as far as the far end of a track next to it, which goes then, the switch joining what it joined there: P4 of another switch, say
	auto const back{station};
	auto const ahead{frame.back().station - station - length};
	if (Distance < -back - 1e-3 || Distance > ahead + 1e-3)
	{
		m_switch.status = format(STR_C("The switch goes %.2f m back and %.2f m on along the curve at most"), std::max(0.0, back), std::max(0.0, ahead));
		ui()->set_status(m_switch.status, true);
		return false;
	}
	// a track shorter than this left beside it goes too
	constexpr double kRemnant{0.5};
	auto distance{std::clamp(Distance, -back, ahead)};
	if (back + distance < kRemnant)
		distance = -back;
	else if (ahead - distance < kRemnant)
		distance = ahead;
	auto const paths{bent_switch_paths(Track, frame, station, distance)};
	auto const joints{editor_track::joints(Track)};
	std::vector<bool> handled(joints.size(), false);
	// the line leaving the end of the diverging track: the curve past it laid again up to the straight beyond it
	std::vector<switch_branch> branches;
	for (std::size_t i = 0; i < joints.size(); ++i)
		if (joints[i].own.path == 1)
			if (auto branch{take_switch_branch(Track, joints[i], i)})
				branches.push_back(std::move(*branch));
	editor_track::edit edit;
	edit.capture(Track);
	// the tracks of the curve on both sides laid along it up to the new ends of the switch
	std::vector<std::string> gone;
	for (int k = 0; k < 2; ++k)
	{
		auto &side{*sides[k]};
		for (std::size_t i = 0; i < joints.size(); ++i)
			if (joints[i].own.path == 0 && joints[i].other == &side)
				handled[i] = true;
		// taken up whole: the switch takes its place up to its far end
		if ((k == 0 ? back + distance : ahead - distance) < 1e-3)
		{
			gone.push_back(side.name());
			editor_track::retire(side);
			edit.removed.push_back(&side);
			continue;
		}
		auto const joint{main.points[k == 0 ? segment_data::point::start : segment_data::point::end]};
		auto const &path{side.m_paths.front()};
		auto const atend{glm::distance(path.points[segment_data::point::end], joint) < glm::distance(path.points[segment_data::point::start], joint)};
		auto from{nearest_station(frame, path.points[segment_data::point::start])};
		auto to{nearest_station(frame, path.points[segment_data::point::end])};
		(atend ? to : from) = station + distance + (k == 0 ? 0.0 : length);
		auto const a{sample_at(frame, from)};
		auto const b{sample_at(frame, to)};
		auto const way{to >= from ? 1.0 : -1.0};
		auto const span{std::abs(to - from)};
		auto const turn{std::abs(geometry::signed_angle(a.tangent, b.tangent))};
		auto const handle{turn > 1e-6 ? 4.0 / 3.0 * std::tan(turn / 4.0) * span / turn : span / 3.0};
		segment_data laid{path};
		laid.pieces.clear();
		laid.points[segment_data::point::start] = a.position;
		laid.points[segment_data::point::end] = b.position;
		// right at the new end of the switch
		laid.points[atend ? segment_data::point::end : segment_data::point::start] = paths.front().points[k == 0 ? segment_data::point::start : segment_data::point::end];
		auto const rise{laid.points[segment_data::point::end].y - laid.points[segment_data::point::start].y};
		laid.points[segment_data::point::control1] = {a.tangent.x * way * handle, rise / 3.0, a.tangent.y * way * handle};
		laid.points[segment_data::point::control2] = {-b.tangent.x * way * handle, -rise / 3.0, -b.tangent.y * way * handle};
		laid.rolls = {static_cast<float>(a.roll * way), static_cast<float>(b.roll * way)};
		edit.capture(side);
		side.m_paths.front() = laid;
	}
	Track.m_paths.assign(paths.begin(), paths.begin() + 2);
	auto const notes{plan_switch_branches(Track, joints, branches, handled)};
	auto const loose{switch_rejoin(Track, joints, handled, edit)};
	editor_track::commit(edit.changed);
	for (auto const &branch : branches)
		lay_switch_branch(branch, edit);
	push_track_snapshot(std::move(edit.states), std::move(edit.created), std::move(edit.removed));
	switch_store::follow();
	records_to_history();
	straight_refresh();
	m_switch.status = format(STR_C("Switch %s moved %.2f m along the curve"), Track.name().c_str(), distance);
	for (auto const &name : gone)
		m_switch.status += "\n" + format(STR_C("%s taken up whole, the switch joins what it joined"), name.c_str());
	if (false == loose.empty())
		m_switch.status += "\n" + std::string{STR_C("Too far from the new ends of the switch, left unjoined: ")} + loose;
	if (false == notes.empty())
		m_switch.status += "\n" + notes;
	ui()->set_status(m_switch.status, false == loose.empty());
	return true;
}

bool editor_mode::slide_switch(TTrack &Track, double const Distance)
{
	if (std::abs(Distance) < 0.005)
		return false;
	// a slip slides whole
	if (auto const slip{slip_of(Track)})
		return slide_slip(*slip, Distance);
	// a switch of a crossover along a curve takes the crossover with it
	if (crossover_of(Track).has_value())
		return slide_curved_connection(Track, Distance);
	// one bent into a curve slides along the curve
	if (Track.m_paths.size() == 2 && has_controls(Track.m_paths.front()))
		return slide_bent_switch(Track, Distance);
	auto const set{double_of(Track)};
	auto &first{set.has_value() ? *set->first : Track};
	if (first.m_paths.size() < 2)
		return false;
	auto paths{editor_track::slid(first, Distance)};
	if (paths.empty())
		return false;
	std::string status;
	bool moved{false};
	if (set.has_value())
	{
		auto const shift{paths.front().points[segment_data::point::start] - first.m_paths.front().points[segment_data::point::start]};
		paths = double_paths(*set);
		for (auto &path : paths)
			path.translate(shift);
		moved = move_double_paths(*set, paths, status);
	}
	else
		moved = move_switch_paths(Track, paths, status);
	if (false == moved)
	{
		m_switch.status = status;
		ui()->set_status(status, true);
		return false;
	}
	switch_store::follow();
	records_to_history();
	straight_refresh();
	m_switch.status = status.empty() ? format(STR_C("Switch %s moved %.2f m along the straight"), first.name().c_str(), Distance) : status;
	ui()->set_status(m_switch.status, false == status.empty());
	return true;
}

bool editor_mode::switch_slides(TTrack const &Track) const
{
	if (auto const slip{slip_of(Track)})
	{
		slip_slide room;
		std::string reason;
		return slip_room(*slip, room, reason);
	}
	if (Track.eType == tt_Normal)
	{
		auto const set{double_of(Track)};
		return set.has_value() && switch_slides(*set->first) && switch_slides(*set->second);
	}
	if (Track.eType != tt_Switch || Track.m_paths.size() != 2 || Track.m_editorremoved)
		return false;
	if (false == has_controls(Track.m_paths.front()))
		return true;
	// bent into a curve: along the curve, where it goes on into plain tracks on both sides
	std::vector<curve_sample> frame;
	std::array<TTrack *, 2> sides;
	double station;
	return bent_switch_frame(Track, frame, sides, station);
}

void editor_mode::switch_slide_start(TTrack &Track)
{
	auto &slide{m_switch.slide};
	slide = {};
	std::string reason;
	// a slip along its first track, from its first switch
	if (auto const slip{slip_of(Track)})
	{
		slip_slide room;
		auto const axis{editor_track::main_axis(*slip->switches.front())};
		if (false == slip_room(*slip, room, reason) || false == axis.has_value())
		{
			if (false == reason.empty())
				ui()->set_status(reason, true);
			return;
		}
		auto const &mouse{ImGui::GetIO().MousePos};
		slide.active = true;
		slide.track = slip->switches.front();
		slide.pressed = {mouse.x, mouse.y};
		slide.grip = axis->along(cursor_level(axis->origin.y));
		slide.length = 0.0;
		slide.low = room.low;
		slide.high = room.high;
		return;
	}
	// bent into a curve: along it, the tracks next to it keeping a metre, the curve past its diverging track drawn as it'll be laid
	if (std::array<TTrack *, 2> sides; bent_switch_frame(Track, slide.frame, sides, slide.station))
	{
		auto const &main{Track.m_paths.front()};
		auto const &mouse{ImGui::GetIO().MousePos};
		slide.active = true;
		slide.track = &Track;
		slide.pressed = {mouse.x, mouse.y};
		slide.grip = nearest_station(slide.frame, cursor_level(main.points[segment_data::point::start].y));
		slide.length = nearest_station(slide.frame, main.points[segment_data::point::end]) - slide.station;
		slide.low = -slide.station;
		slide.high = std::max(0.0, slide.frame.back().station - slide.station - slide.length);
		auto const joints{editor_track::joints(Track)};
		for (std::size_t i = 0; i < joints.size(); ++i)
			if (joints[i].own.path == 1)
				if (auto branch{take_switch_branch(Track, joints[i], i)})
					slide.branches.push_back({joints[i], 1, std::move(*branch)});
		return;
	}
	auto const set{double_of(Track)};
	auto &first{set.has_value() ? *set->first : Track};
	auto const axis{editor_track::main_axis(first)};
	if (false == axis.has_value())
		return;
	slide.length = axis->length;
	if (false == (set.has_value() ? double_room(*set, slide.low, slide.high, slide.length, reason) : switch_room(first, slide.low, slide.high, reason)))
	{
		if (false == reason.empty())
			ui()->set_status(reason, true);
		return;
	}
	auto const &mouse{ImGui::GetIO().MousePos};
	slide.active = true;
	slide.track = &first;
	slide.pressed = {mouse.x, mouse.y};
	slide.grip = axis->along(cursor_level(axis->origin.y));
	std::vector<TTrack *> members{&first};
	if (set.has_value())
		members = {set->first, set->link, set->second};
	for (auto *member : members)
	{
		if (member->eType != tt_Switch)
			continue;
		auto const line{editor_track::find_straight(*member, m_straights.tolerance)};
		for (std::size_t i = 0; i < line.tracks.size(); ++i)
		{
			if (std::find(members.begin(), members.end(), line.tracks[i]) != members.end())
				continue;
			auto const &path{line.tracks[i]->m_paths[line.paths[i]]};
			for (auto const index : {segment_data::point::start, segment_data::point::end})
				slide.joints.push_back(axis->along(path.points[index]));
		}
	}
	std::vector<TTrack const *> const skip(members.begin(), members.end());
	for (auto *member : members)
	{
		if (member->eType != tt_Switch)
			continue;
		std::size_t const offset{set.has_value() && member == set->second ? 2u : 0u};
		auto const joints{editor_track::joints(*member)};
		for (auto &branch : switch_branches(*member, joints, skip))
		{
			auto const &joint{joints[branch.joint]};
			slide.branches.push_back({joint, offset + static_cast<std::size_t>(joint.own.path), std::move(branch)});
		}
	}
}

void editor_mode::switch_slide_update()
{
	auto &slide{m_switch.slide};
	if (false == slide.active)
		return;
	// along the curve it's bent into
	if (false == slide.frame.empty())
	{
		if (slide.track == nullptr || slide.track->m_editorremoved)
		{
			slide = {};
			return;
		}
		auto const height{sample_at(slide.frame, slide.station).position.y};
		auto distance{std::clamp(nearest_station(slide.frame, cursor_level(height)) - slide.grip, slide.low, slide.high)};
		// drawn to the far ends of the tracks next to it, where it takes one up whole and joins what it joined
		for (auto const end : {slide.low, slide.high})
			if (std::abs(distance - end) < 1.0)
				distance = end;
		slide.distance = distance;
		return;
	}
	auto const axis{slide.track != nullptr && false == slide.track->m_editorremoved && slide.track->m_paths.size() >= 2 ? editor_track::main_axis(*slide.track) : std::nullopt};
	if (false == axis.has_value())
	{
		slide = {};
		return;
	}
	auto const length{slide.length};
	auto const distance{std::clamp(axis->along(cursor_level(axis->origin.y)) - slide.grip, slide.low, slide.high - length)};
	double best{1.0};
	double snapped{distance};
	for (auto const joint : slide.joints)
		for (auto const end : {0.0, length})
			if (auto const gap{std::abs(joint - (end + distance))}; gap < best && std::abs(joint - end) > 0.01)
			{
				best = gap;
				snapped = joint - end;
			}
	slide.distance = std::clamp(snapped, slide.low, slide.high - length);
}

void editor_mode::switch_slide_finish()
{
	auto &slide{m_switch.slide};
	if (false == slide.active)
		return;
	auto *track{slide.track};
	auto const distance{slide.distance};
	auto const &mouse{ImGui::GetIO().MousePos};
	auto const dragged{glm::length(glm::vec2{mouse.x, mouse.y} - slide.pressed) > kDragPixels};
	slide = {};
	if (track != nullptr && false == track->m_editorremoved && dragged)
		slide_switch(*track, distance);
}

void editor_mode::draw_switch_slide() const
{
	auto const &slide{m_switch.slide};
	if (false == slide.active || slide.track == nullptr || slide.track->m_paths.size() < 2)
		return;
	auto const &mouse{ImGui::GetIO().MousePos};
	if (glm::length(glm::vec2{mouse.x, mouse.y} - slide.pressed) <= kDragPixels)
		return;
	auto paths{slide.frame.empty() ? editor_track::slid(*slide.track, slide.distance) : bent_switch_paths(*slide.track, slide.frame, slide.station, slide.distance)};
	if (paths.empty())
		return;
	// a slip with all it takes along
	if (auto const slip{slip_of(*slide.track)})
	{
		slip_slide room;
		std::string reason;
		slip_room(*slip, room, reason);
		paths.clear();
		for (auto const *mover : room.movers)
			for (auto path : mover->m_paths)
			{
				path.translate(room.shift * slide.distance);
				paths.push_back(path);
			}
	}
	else if (auto const set{double_of(*slide.track)})
	{
		auto const shift{paths.front().points[segment_data::point::start] - slide.track->m_paths.front().points[segment_data::point::start]};
		paths = double_paths(*set);
		for (auto &path : paths)
			path.translate(shift);
	}
	screen_projection const projection;
	auto *drawlist{ImGui::GetBackgroundDrawList(ImGui::GetMainViewport())};
	auto const draw = [&](segment_data const &Path, ImU32 const Color, float const Width) {
		bezier const curve{Path};
		auto previous{curve.point(0.0)};
		for (int i = 1; i <= 24; ++i)
		{
			auto const next{curve.point(i / 24.0)};
			projection.line(drawlist, previous, next, Color, Width);
			previous = next;
		}
	};
	for (auto const &path : paths)
		draw(path, overlay_color::marked, 3.0f);
	// the curves past the switch, laid again up to the straight beyond them
	for (auto const &line : slide.branches)
	{
		if (line.path >= paths.size())
			continue;
		auto branch{line.branch};
		if (plan_switch_branch(paths[line.path], line.joint, branch))
			for (auto const &piece : branch.pieces)
				draw(piece, overlay_color::grip, 2.0f);
	}
	ImVec2 at;
	auto const start{paths.front().points[segment_data::point::start]};
	if (false == projection.project(start, at))
		return;
	auto const km{alignment_store::chainage_at(start)};
	auto const label{km.has_value() ? format("%+.2f m  km %.3f", slide.distance, *km / 1000.0) : format("%+.2f m", slide.distance)};
	auto const size{ImGui::CalcTextSize(label.c_str())};
	drawlist->AddRectFilled(ImVec2(at.x + 10.0f, at.y - 8.0f), ImVec2(at.x + 18.0f + size.x, at.y + 8.0f), IM_COL32(0, 0, 0, 180), 3.0f);
	drawlist->AddText(ImVec2(at.x + 14.0f, at.y - 8.0f), overlay_color::highlight, label.c_str());
}