#include "geoData.h"
#include "collections.h"
#include "geometricPlane.h"
#include <fstream>
#include <glm/gtx/intersect.hpp>
#include <maths.h>
#include <ranges>
#include <set>

GeoData::GeoData()
{
	add_property(surface);
}

GeoData
GeoData::loadFromAsciiGrid(const std::filesystem::path & input)
{
	size_t ncols = 0, nrows = 0, xllcorner = 0, yllcorner = 0, cellsize = 0;
	std::map<std::string_view, size_t *> properties {
			{"ncols", &ncols},
			{"nrows", &nrows},
			{"xllcorner", &xllcorner},
			{"yllcorner", &yllcorner},
			{"cellsize", &cellsize},
	};
	std::ifstream f {input};
	while (!properties.empty()) {
		std::string property;
		f >> property;
		f >> *properties.at(property);
		properties.erase(property);
	}
	xllcorner *= 1000;
	yllcorner *= 1000;
	cellsize *= 1000;
	std::vector<VertexHandle> vertices;
	vertices.reserve(ncols * nrows);
	GeoData mesh;
	mesh.lowerExtent = {xllcorner, yllcorner, std::numeric_limits<GlobalDistance>::max()};
	mesh.upperExtent = {xllcorner + (cellsize * (ncols - 1)), yllcorner + (cellsize * (nrows - 1)),
			std::numeric_limits<GlobalDistance>::min()};
	for (size_t row = 0; row < nrows; ++row) {
		for (size_t col = 0; col < ncols; ++col) {
			float heightf = 0;
			f >> heightf;
			const auto height = static_cast<GlobalDistance>(std::round(heightf * 1000.F));
			mesh.upperExtent.z = std::max(mesh.upperExtent.z, height);
			mesh.lowerExtent.z = std::min(mesh.lowerExtent.z, height);
			vertices.push_back(mesh.add_vertex({xllcorner + (col * cellsize), yllcorner + (row * cellsize), height}));
		}
	}
	if (!f.good()) {
		throw std::runtime_error("Couldn't read terrain file");
	}
	for (size_t row = 1; row < nrows; ++row) {
		for (size_t col = 1; col < ncols; ++col) {
			mesh.add_face({
					vertices[ncols * (row - 1) + (col - 1)],
					vertices[ncols * (row - 0) + (col - 0)],
					vertices[ncols * (row - 0) + (col - 1)],
			});
			mesh.add_face({
					vertices[ncols * (row - 1) + (col - 1)],
					vertices[ncols * (row - 1) + (col - 0)],
					vertices[ncols * (row - 0) + (col - 0)],
			});
		}
	}
	mesh.update_vertex_normals_only();

	return mesh;
};

constexpr static GlobalDistance GRID_SIZE = 10'000;

GeoData
GeoData::createFlat(GlobalPosition2D lower, GlobalPosition2D upper, GlobalDistance h)
{
	assert((upper - lower) % GRID_SIZE == GlobalPosition2D {});
	GeoData mesh;

	mesh.lowerExtent = {lower, h};
	mesh.upperExtent = {upper, h};

	std::vector<VertexHandle> vertices;
	for (GlobalDistance row = lower.x; row <= upper.x; row += GRID_SIZE) {
		for (GlobalDistance col = lower.y; col <= upper.y; col += GRID_SIZE) {
			vertices.push_back(mesh.add_vertex({col, row, h}));
		}
	}

	const auto n = glm::vec<2, size_t> {((upper - lower) / GRID_SIZE) + 1};
	for (auto row = 1U; row < n.x; ++row) {
		for (auto col = 1U; col < n.y; ++col) {
			mesh.add_face({
					vertices[n.y * (row - 1) + (col - 1)],
					vertices[n.y * (row - 0) + (col - 0)],
					vertices[n.y * (row - 0) + (col - 1)],
			});
			mesh.add_face({
					vertices[n.y * (row - 1) + (col - 1)],
					vertices[n.y * (row - 1) + (col - 0)],
					vertices[n.y * (row - 0) + (col - 0)],
			});
		}
	}

	mesh.update_vertex_normals_only();

	return mesh;
}

OpenMesh::FaceHandle
GeoData::findPoint(GlobalPosition2D p) const
{
	return findPoint(p, *faces_sbegin());
}

GeoData::PointFace::PointFace(const GlobalPosition2D p, const GeoData * mesh) :
	PointFace {p, mesh, *mesh->faces_sbegin()}
{
}

GeoData::PointFace::PointFace(const GlobalPosition2D p, const GeoData * mesh, FaceHandle start) :
	PointFace {p, mesh->findPoint(p, start)}
{
}

GeoData::FaceHandle
GeoData::PointFace::face(const GeoData * mesh, FaceHandle start) const
{
	if (_face.is_valid()) {
		assert(mesh->triangleContainsPoint(point, _face));
		return _face;
	}
	else {
		return (_face = mesh->findPoint(point, start));
	}
}

GeoData::FaceHandle
GeoData::PointFace::face(const GeoData * mesh) const
{
	return face(mesh, *mesh->faces_sbegin());
}

namespace {
	template<template<typename> typename Op>
	[[nodiscard]] constexpr inline auto
	pointLineOp(const GlobalPosition2D p, const GlobalPosition2D e1, const GlobalPosition2D e2)
	{
		return Op {}(CalcDistance(e2.x - e1.x) * CalcDistance(p.y - e1.y),
				CalcDistance(e2.y - e1.y) * CalcDistance(p.x - e1.x));
	}

	constexpr auto pointLeftOfLine = pointLineOp<std::greater>;
	constexpr auto pointLeftOfOrOnLine = pointLineOp<std::greater_equal>;

	static_assert(pointLeftOfLine({1, 2}, {1, 1}, {2, 2}));
	static_assert(pointLeftOfLine({2, 1}, {2, 2}, {1, 1}));
	static_assert(pointLeftOfLine({2, 2}, {1, 2}, {2, 1}));
	static_assert(pointLeftOfLine({1, 1}, {2, 1}, {1, 2}));
	static_assert(pointLeftOfOrOnLine({310000000, 490000000}, {310000000, 490000000}, {310050000, 490050000}));
	static_assert(pointLeftOfOrOnLine({310000000, 490000000}, {310050000, 490050000}, {310000000, 490050000}));
	static_assert(pointLeftOfOrOnLine({310000000, 490000000}, {310000000, 490050000}, {310000000, 490000000}));

	[[nodiscard]] constexpr inline bool
	linesCross(
			const GlobalPosition2D a1, const GlobalPosition2D a2, const GlobalPosition2D b1, const GlobalPosition2D b2)
	{
		return (pointLeftOfLine(a2, b1, b2) == pointLeftOfLine(a1, b2, b1))
				&& (pointLeftOfLine(b1, a1, a2) == pointLeftOfLine(b2, a2, a1));
	}

	static_assert(linesCross({1, 1}, {2, 2}, {1, 2}, {2, 1}));
	static_assert(linesCross({2, 2}, {1, 1}, {1, 2}, {2, 1}));

	[[nodiscard]] constexpr inline bool
	linesCrossLtR(
			const GlobalPosition2D a1, const GlobalPosition2D a2, const GlobalPosition2D b1, const GlobalPosition2D b2)
	{
		return pointLeftOfLine(a2, b1, b2) && pointLeftOfLine(a1, b2, b1) && pointLeftOfLine(b1, a1, a2)
				&& pointLeftOfLine(b2, a2, a1);
	}

	static_assert(linesCrossLtR({1, 1}, {2, 2}, {1, 2}, {2, 1}));
	static_assert(!linesCrossLtR({2, 2}, {1, 1}, {1, 2}, {2, 1}));

	constexpr GlobalPosition3D
	positionOnTriangle(const GlobalPosition2D point, const GeoData::Triangle<3> & t)
	{
		const CalcPosition3D a = t[1] - t[0], b = t[2] - t[0];
		const auto n = crossProduct(a, b);
		return {point, ((n.x * t[0].x) + (n.y * t[0].y) + (n.z * t[0].z) - (n.x * point.x) - (n.y * point.y)) / n.z};
	}

	static_assert(positionOnTriangle({7, -2}, {{1, 2, 3}, {1, 0, 1}, {-2, 1, 0}}) == GlobalPosition3D {7, -2, 3});
}

OpenMesh::FaceHandle
GeoData::findPoint(GlobalPosition2D p, OpenMesh::FaceHandle f) const
{
	while (f.is_valid() && !triangleContainsPoint(p, triangle<2>(f))) {
		for (auto next = cfh_iter(f); next.is_valid(); ++next) {
			f = opposite_face_handle(*next);
			if (f.is_valid()) {
				const auto e1 = point(to_vertex_handle(*next));
				const auto e2 = point(to_vertex_handle(opposite_halfedge_handle(*next)));
				if (pointLeftOfLine(p, e1, e2)) {
					break;
				}
			}
			f.reset();
		}
	}
	return f;
}

GlobalPosition3D
GeoData::positionAt(const PointFace & p) const
{
	return positionOnTriangle(p.point, triangle<3>(p.face(this)));
}

[[nodiscard]] GeoData::IntersectionResult
GeoData::intersectRay(const Ray<GlobalPosition3D> & ray) const
{
	return intersectRay(ray, findPoint(ray.start));
}

[[nodiscard]] GeoData::IntersectionResult
GeoData::intersectRay(const Ray<GlobalPosition3D> & ray, FaceHandle face) const
{
	GeoData::IntersectionResult out;
	walkUntil(PointFace {ray.start, face},
			ray.start.xy() + (ray.direction.xy() * RelativePosition2D(upperExtent.xy() - lowerExtent.xy())),
			[&out, &ray, this](FaceHandle face) {
				BaryPosition bari {};
				RelativeDistance dist {};
				const auto t = triangle<3>(face);
				if (ray.intersectTriangle(t.x, t.y, t.z, bari, dist)) {
					out.emplace(t * bari, face);
					return true;
				}
				return false;
			});
	return out;
}

void
GeoData::walk(const PointFace & from, const GlobalPosition2D to, const std::function<void(FaceHandle)> & op) const
{
	walkUntil(from, to, [&op](const auto & fh) {
		op(fh);
		return false;
	});
}

void
GeoData::walkUntil(const PointFace & from, const GlobalPosition2D to, const std::function<bool(FaceHandle)> & op) const
{
	auto f = from.face(this);
	if (!f.is_valid()) {
		const auto entryEdge = findEntry(from.point, to);
		if (!entryEdge.is_valid()) {
			return;
		}
		f = opposite_face_handle(entryEdge);
	}
	FaceHandle previousFace;
	while (f.is_valid() && !op(f)) {
		for (auto next = cfh_iter(f); next.is_valid(); ++next) {
			f = opposite_face_handle(*next);
			if (f.is_valid() && f != previousFace) {
				const auto e1 = point(to_vertex_handle(*next));
				const auto e2 = point(to_vertex_handle(opposite_halfedge_handle(*next)));
				if (linesCrossLtR(from.point, to, e1, e2)) {
					previousFace = f;
					break;
				}
			}
			f.reset();
		}
	}
}

void
GeoData::boundaryWalk(const std::function<void(HalfedgeHandle)> & op) const
{
	boundaryWalk(op, findBoundaryStart());
}

void
GeoData::boundaryWalk(const std::function<void(HalfedgeHandle)> & op, HalfedgeHandle start) const
{
	assert(is_boundary(start));
	boundaryWalkUntil(
			[&op](auto heh) {
				op(heh);
				return false;
			},
			start);
}

void
GeoData::boundaryWalkUntil(const std::function<bool(HalfedgeHandle)> & op) const
{
	boundaryWalkUntil(op, findBoundaryStart());
}

void
GeoData::boundaryWalkUntil(const std::function<bool(HalfedgeHandle)> & op, HalfedgeHandle start) const
{
	assert(is_boundary(start));
	if (!op(start)) {
		for (auto heh = next_halfedge_handle(start); heh != start; heh = next_halfedge_handle(heh)) {
			if (op(heh)) {
				break;
			}
		}
	}
}

GeoData::HalfedgeHandle
GeoData::findEntry(const GlobalPosition2D from, const GlobalPosition2D to) const
{
	HalfedgeHandle entry;
	boundaryWalkUntil([this, from, to, &entry](auto he) {
		const auto e1 = point(to_vertex_handle(he));
		const auto e2 = point(to_vertex_handle(opposite_halfedge_handle(he)));
		if (linesCrossLtR(from, to, e1, e2)) {
			entry = he;
			return true;
		}
		return false;
	});
	return entry;
}

bool
GeoData::triangleContainsPoint(const GlobalPosition2D p, const Triangle<2> & t)
{
	return pointLeftOfOrOnLine(p, t[0], t[1]) && pointLeftOfOrOnLine(p, t[1], t[2])
			&& pointLeftOfOrOnLine(p, t[2], t[0]);
}

bool
GeoData::triangleContainsPoint(const GlobalPosition2D p, FaceHandle face) const
{
	return triangleContainsPoint(p, triangle<2>(face));
}

GeoData::HalfedgeHandle
GeoData::findBoundaryStart() const
{
	return *std::find_if(halfedges_sbegin(), halfedges_end(), [this](const auto heh) {
		return is_boundary(heh);
	});
}

[[nodiscard]] RelativePosition3D
GeoData::difference(const HalfedgeHandle heh) const
{
	return point(to_vertex_handle(heh)) - point(from_vertex_handle(heh));
}

[[nodiscard]] RelativeDistance
GeoData::length(const HalfedgeHandle heh) const
{
	return glm::length(difference(heh));
}

[[nodiscard]] GlobalPosition3D
GeoData::centre(const HalfedgeHandle heh) const
{
	return point(from_vertex_handle(heh)) + (difference(heh) / 2.F);
}

void
GeoData::update_vertex_normals_only()
{
	update_vertex_normals_only(vertices_sbegin());
}

void
GeoData::update_vertex_normals_only(VertexIter start)
{
	std::for_each(start, vertices_end(), [this](const auto vh) {
		if (normal(vh) == Normal3D {}) {
			Normal3D n;
			calc_vertex_normal_correct(vh, n);
			this->set_normal(vh, glm::normalize(n));
		}
	});
}

bool
GeoData::triangleOverlapsTriangle(const Triangle<2> & a, const Triangle<2> & b)
{
	return triangleContainsPoint(a.x, b) || triangleContainsPoint(a.y, b) || triangleContainsPoint(a.z, b)
			|| triangleContainsPoint(b.x, a) || triangleContainsPoint(b.y, a) || triangleContainsPoint(b.z, a)
			|| linesCross(a.x, a.y, b.x, b.y) || linesCross(a.x, a.y, b.y, b.z) || linesCross(a.x, a.y, b.z, b.x)
			|| linesCross(a.y, a.z, b.x, b.y) || linesCross(a.y, a.z, b.y, b.z) || linesCross(a.y, a.z, b.z, b.x)
			|| linesCross(a.z, a.x, b.x, b.y) || linesCross(a.z, a.x, b.y, b.z) || linesCross(a.z, a.x, b.z, b.x);
}

bool
GeoData::triangleContainsTriangle(const Triangle<2> & a, const Triangle<2> & b)
{
	return triangleContainsPoint(a.x, b) && triangleContainsPoint(a.y, b) && triangleContainsPoint(a.z, b);
}

void
GeoData::split(FaceHandle _fh)
{
	// Collect halfedges of face
	const HalfedgeHandle he0 = halfedge_handle(_fh);
	const HalfedgeHandle he1 = next_halfedge_handle(he0);
	const HalfedgeHandle he2 = next_halfedge_handle(he1);

	const EdgeHandle eh0 = edge_handle(he0);
	const EdgeHandle eh1 = edge_handle(he1);
	const EdgeHandle eh2 = edge_handle(he2);

	// Collect points of face
	const VertexHandle p0 = to_vertex_handle(he0);
	const VertexHandle p1 = to_vertex_handle(he1);
	const VertexHandle p2 = to_vertex_handle(he2);

	// Calculate midpoint coordinates
	const Point new0 = centre(he0);
	const Point new1 = centre(he1);
	const Point new2 = centre(he2);

	// Add vertices at midpoint coordinates
	const VertexHandle v0 = add_vertex(new0);
	const VertexHandle v1 = add_vertex(new1);
	const VertexHandle v2 = add_vertex(new2);

	const bool split0 = !is_boundary(eh0);
	const bool split1 = !is_boundary(eh1);
	const bool split2 = !is_boundary(eh2);

	// delete original face
	delete_face(_fh, false);

	// split boundary edges of deleted face ( if not boundary )
	if (split0) {
		split(eh0, v0);
	}

	if (split1) {
		split(eh1, v1);
	}

	if (split2) {
		split(eh2, v2);
	}

	// Retriangulate
	add_face(v0, p0, v1);
	add_face(p2, v0, v2);
	add_face(v2, v1, p1);
	add_face(v2, v0, v1);
}

static constexpr RelativeDistance MAX_SLOPE = .5F;

void
GeoData::setHeights(const std::span<const GlobalPosition3D> triangleStrip, const Surface &)
{
	if (triangleStrip.size() < 3) {
		return;
	}
	const auto stripMinMax = std::ranges::minmax(triangleStrip, {}, &GlobalPosition3D::z);
	lowerExtent.z = std::min(upperExtent.z, stripMinMax.min.z);
	upperExtent.z = std::max(upperExtent.z, stripMinMax.max.z);

	const auto initialVertexCount = static_cast<unsigned int>(n_vertices());

	// New vertices for each vertex in triangleStrip
	std::vector<VertexHandle> newVerts;
	newVerts.reserve(newVerts.size());
	std::transform(
			triangleStrip.begin(), triangleStrip.end(), std::back_inserter(newVerts), [this](const auto tsPoint) {
				return split(findPoint(tsPoint), tsPoint);
			});

	// Create temporary triangles from triangleStrip
	std::vector<Triangle<3>> strip;
	std::transform(
			strip_begin(triangleStrip), strip_end(triangleStrip), std::back_inserter(strip), [](const auto & newVert) {
				const auto [a, b, c] = newVert;
				return Triangle<3> {a, b, c};
			});
	auto getTriangle = [&strip](const auto point) -> const Triangle<3> * {
		if (const auto t = std::ranges::find_if(strip,
					[point](const auto & triangle) {
						return triangleContainsPoint(point, triangle);
					});
				t != strip.end()) {
			return &*t;
		}
		return nullptr;
	};

	// Cut along each edge of triangleStrip AB, AC, BC, BD, CD, CE etc
	std::map<VertexHandle, const Triangle<3> *> boundaryTriangles;
	auto doBoundaryPart
			= [this, &boundaryTriangles](VertexHandle start, VertexHandle end, const Triangle<3> & triangle) {
				  boundaryTriangles.emplace(start, &triangle);
				  const auto endPoint = point(end);
				  while (std::any_of(voh_begin(start), voh_end(start), [&](const auto & outHalf) {
					  const auto next = next_halfedge_handle(outHalf);
					  if (next == end) {
						  return false;
					  }
					  const auto startPoint = point(start);
					  const auto nextStartPoint = point(from_vertex_handle(next));
					  const auto nextEndPoint = point(to_vertex_handle(next));
					  if (linesCross(startPoint, endPoint, nextStartPoint, nextEndPoint)) {
						  if (const auto intersection = linesIntersectAt(
									  startPoint.xy(), endPoint.xy(), nextStartPoint.xy(), nextEndPoint.xy())) {
							  start = split(edge_handle(next), positionOnTriangle(*intersection, triangle));
							  boundaryTriangles.emplace(start, &triangle);
							  return true;
						  }
					  }
					  return false;
				  })) { }
			  };
	auto doBoundary = [&doBoundaryPart, triangle = strip.begin()](const auto & verts) mutable {
		const auto & [a, b, c] = verts;
		doBoundaryPart(a, b, *triangle);
		doBoundaryPart(a, c, *triangle);
		triangle++;
	};
	std::ranges::for_each(newVerts | std::views::adjacent<3>, doBoundary);
	doBoundaryPart(newVerts.back(), *++newVerts.rbegin(), *strip.rbegin());

	std::set<HalfedgeHandle> done;
	std::set<HalfedgeHandle> todo;
	auto todoOutHalfEdges = [&todo, &done, this](const VertexHandle v) {
		std::copy_if(voh_begin(v), voh_end(v), std::inserter(todo, todo.end()), [&done](const auto & h) {
			return !done.contains(h);
		});
	};
	std::ranges::for_each(newVerts, todoOutHalfEdges);
	while (!todo.empty()) {
		const auto heh = todo.extract(todo.begin()).value();
		const auto fromVertex = from_vertex_handle(heh);
		const auto toVertex = to_vertex_handle(heh);
		const auto & fromPoint = point(fromVertex);
		auto & toPoint = point(toVertex);
		auto toTriangle = getTriangle(toPoint);
		if (!toTriangle) {
			if (const auto boundaryVertex = boundaryTriangles.find(toVertex);
					boundaryVertex != boundaryTriangles.end()) {
				toTriangle = boundaryVertex->second;
			}
		}
		if (toTriangle) { // point within the new strip, adjust vertically by triangle
			toPoint.z = positionOnTriangle(toPoint, *toTriangle).z;
			todoOutHalfEdges(toVertex);
		}
		else if (!toTriangle) { // point without the new strip, adjust vertically by limit
			const auto maxOffset = static_cast<GlobalDistance>(MAX_SLOPE * glm::length(difference(heh).xy()));
			const auto newHeight = std::clamp(toPoint.z, fromPoint.z - maxOffset, fromPoint.z + maxOffset);
			if (newHeight != toPoint.z) {
				toPoint.z = newHeight;
				std::copy_if(voh_begin(toVertex), voh_end(toVertex), std::inserter(todo, todo.end()),
						[this, &boundaryTriangles](const auto & heh) {
							return !boundaryTriangles.contains(to_vertex_handle(heh));
						});
			}
		}
		done.insert(heh);
	}
	update_vertex_normals_only(VertexIter {*this, vertex_handle(initialVertexCount), true});
}