#pragma once

#include <DB/DataTypes/DataTypesNumberFixed.h>
#include <DB/Functions/IFunction.h>
#include <ext/range.hpp>
#include <math.h>
#include <array>

#define DEGREES_IN_RADIANS (M_PI / 180.0)

namespace DB
{

namespace ErrorCodes
{
	extern const int ARGUMENT_OUT_OF_BOUND;
}

const Float64 EARTH_RADIUS_IN_METERS = 6372797.560856;

static inline Float64 degToRad(Float64 angle) { return angle * DEGREES_IN_RADIANS; }
static inline Float64 radToDeg(Float64 angle) { return angle / DEGREES_IN_RADIANS; }

/**
 *  The function calculates distance in meters between two points on Earth specified by longitude and latitude in degrees.
 *  The function uses great circle distance formula https://en.wikipedia.org/wiki/Great-circle_distance.
 *  Throws exception when one or several input values are not within reasonable bounds.
 *  Latitude must be in [-90, 90], longitude must be [-180, 180]
 *
 */
class FunctionGreatCircleDistance : public IFunction
{
public:

	static constexpr auto name = "greatCircleDistance";
	static FunctionPtr create(const Context &) { return std::make_shared<FunctionGreatCircleDistance>(); }

private:

	enum class instr_type : uint8_t
	{
		get_float_64,
		get_const_float_64
	};

	using instr_t = std::pair<instr_type, const IColumn *>;
	using instrs_t = std::array<instr_t, 4>;

	String getName() const override { return name; }

	size_t getNumberOfArguments() const override { return 4; }

	DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
	{
		for (const auto arg_idx : ext::range(0, arguments.size()))
		{
			const auto arg = arguments[arg_idx].get();
			if (!typeid_cast<const DataTypeFloat64 *>(arg))
				throw Exception(
					"Illegal type " + arg->getName() + " of argument " + std::to_string(arg_idx + 1) + " of function " + getName() + ". Must be Float64",
					ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
		}

		return std::make_shared<DataTypeFloat64>();
	}

	instrs_t getInstructions(const Block & block, const ColumnNumbers & arguments, bool & out_const)
	{
		instrs_t result;
		out_const = true;

		for (const auto arg_idx : ext::range(0, arguments.size()))
		{
			const auto column = block.safeGetByPosition(arguments[arg_idx]).column.get();

			if (const auto col = typeid_cast<const ColumnVector<Float64> *>(column))
			{
				out_const = false;
				result[arg_idx] = instr_t{instr_type::get_float_64, col};
			}
			else if (const auto col = typeid_cast<const ColumnConst<Float64> *>(column))
			{
				result[arg_idx] = instr_t{instr_type::get_const_float_64, col};
			}
			else
				throw Exception("Illegal column " + column->getName() + " of argument of function " + getName(),
					ErrorCodes::ILLEGAL_COLUMN);
		}

		return result;
	}

	/// https://en.wikipedia.org/wiki/Great-circle_distance
	Float64 greatCircleDistance(Float64 lon1Deg, Float64 lat1Deg, Float64 lon2Deg, Float64 lat2Deg)
	{
		if (lon1Deg < -180 || lon1Deg > 180 ||
			lon2Deg < -180 || lon2Deg > 180 ||
			lat1Deg < -90 || lat1Deg > 90 ||
			lat2Deg < -90 || lat2Deg > 90)
		{
			throw Exception("Arguments values out of bounds for function " + getName(), ErrorCodes::ARGUMENT_OUT_OF_BOUND);
		}

		Float64 lon1Rad = degToRad(lon1Deg);
		Float64 lat1Rad = degToRad(lat1Deg);
		Float64 lon2Rad = degToRad(lon2Deg);
		Float64 lat2Rad = degToRad(lat2Deg);
		Float64 u = sin((lat2Rad - lat1Rad) / 2);
		Float64 v = sin((lon2Rad - lon1Rad) / 2);
		return 2.0 * EARTH_RADIUS_IN_METERS * asin(sqrt(u * u + cos(lat1Rad) * cos(lat2Rad) * v * v));
	}


	void executeImpl(Block & block, const ColumnNumbers & arguments, const size_t result) override
	{
		const auto size = block.rows();

		bool result_is_const{};
		auto instrs = getInstructions(block, arguments, result_is_const);

		if (result_is_const)
		{
			const auto & colLon1 = static_cast<const ColumnConst<Float64> *>(block.safeGetByPosition(arguments[0]).column.get())->getData();
			const auto & colLat1 = static_cast<const ColumnConst<Float64> *>(block.safeGetByPosition(arguments[1]).column.get())->getData();
			const auto & colLon2 = static_cast<const ColumnConst<Float64> *>(block.safeGetByPosition(arguments[2]).column.get())->getData();
			const auto & colLat2 = static_cast<const ColumnConst<Float64> *>(block.safeGetByPosition(arguments[3]).column.get())->getData();

			Float64 res = greatCircleDistance(colLon1, colLat1, colLon2, colLat2);
			block.safeGetByPosition(result).column = std::make_shared<ColumnConst<Float64>>(size, res);
		}
		else
		{
			const auto dst = std::make_shared<ColumnVector<Float64>>();
			block.safeGetByPosition(result).column = dst;
			auto & dst_data = dst->getData();
			dst_data.resize(size);
			Float64 vals[instrs.size()];
			for (const auto row : ext::range(0, size))
			{
				for (const auto idx : ext::range(0, instrs.size()))
				{
					if (instr_type::get_float_64 == instrs[idx].first)
						vals[idx] = static_cast<const ColumnVector<Float64> *>(instrs[idx].second)->getData()[row];
					else if (instr_type::get_const_float_64 == instrs[idx].first)
						vals[idx] = static_cast<const ColumnConst<Float64> *>(instrs[idx].second)->getData();
					else
						throw std::logic_error{"unknown instr_type"};
				}
				dst_data[row] = greatCircleDistance(vals[0], vals[1], vals[2], vals[3]);
			}
		}
	}
};


/**
 * The function checks if a point is in one of ellipses in set.
 * The number of arguments must be 2 + 4*N where N is the number of ellipses.
 * The arguments must be arranged as follows: (x, y, x_0, y_0, a_0, b_0, ..., x_i, y_i, a_i, b_i)
 * All ellipses parameters must be const values;
 *
 * The function first checks bounding box condition.
 * If a point is inside an ellipse's bounding box, the quadratic condition is evaluated.
 *
 * Here we assume that points in one block are close and are likely to fit in one ellipse,
 * so the last success ellipse index is remembered to check this ellipse first for next point.
 *
 */
class FunctionPointInEllipses : public IFunction
{
public:

	static constexpr auto name = "pointInEllipses";
	static FunctionPtr create(const Context &) { return std::make_shared<FunctionPointInEllipses>(); }

private:

	struct Ellipse {
		Float64 x;
		Float64 y;
		Float64 a;
		Float64 b;
	};

	String getName() const override { return name; }

	bool isVariadic() const override { return true; }

	size_t getNumberOfArguments() const override { return 0; }

	DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
	{
		if (arguments.size() < 6 || arguments.size() % 4 != 2)
		{
			throw Exception(
				"Incorrect number of arguments of function " + getName() + ". Must be 2 for your point plus 4 * N for ellipses (x_i, y_i, a_i, b_i).");
		}

		/// For array on stack, see below.
		if (arguments.size() > 10000)
		{
			throw Exception(
				"Number of arguments of function " + getName() + " is too large.");
		}

		for (const auto arg_idx : ext::range(0, arguments.size()))
		{
			const auto arg = arguments[arg_idx].get();
			if (!typeid_cast<const DataTypeFloat64 *>(arg))
			{
				throw Exception(
					"Illegal type " + arg->getName() + " of argument " + std::to_string(arg_idx + 1) + " of function " + getName() + ". Must be Float64",
					ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
			}
		}

		return std::make_shared<DataTypeUInt8>();
	}

	void executeImpl(Block & block, const ColumnNumbers & arguments, const size_t result) override
	{
		const auto size = block.rows();

		/// Prepare array of ellipses.
		size_t ellipses_count = (arguments.size() - 2) / 4;
		Ellipse ellipses[ellipses_count];

		for (const auto ellipse_idx : ext::range(0, ellipses_count))
		{
			Float64 ellipse_data[4];
			for (const auto idx : ext::range(0, 4))
			{
				int arg_idx = 2 + 4 * ellipse_idx + idx;
				const auto column = block.safeGetByPosition(arguments[arg_idx]).column.get();
				if (const auto col = typeid_cast<const ColumnConst<Float64> *>(column))
				{
					ellipse_data[idx] = col->getData();
				}
				else
				{
					throw Exception(
						"Illegal type " + column->getName() + " of argument " + std::to_string(arg_idx + 1) + " of function " + getName() + ". Must be const Float64",
						ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
				}
			}
			ellipses[ellipse_idx] = Ellipse{ellipse_data[0], ellipse_data[1], ellipse_data[2], ellipse_data[3]};
		}

		int const_cnt = 0;
		for (const auto idx : ext::range(0, 2))
		{
			const auto column = block.safeGetByPosition(arguments[idx]).column.get();
			if (typeid_cast<const ColumnConst<Float64> *> (column))
			{
				++const_cnt;
			}
			else if (!typeid_cast<const ColumnVector<Float64> *> (column))
			{
				throw Exception("Illegal column " + column->getName() + " of argument of function " + getName(),
					ErrorCodes::ILLEGAL_COLUMN);
			}
		}

		const auto col_x = block.safeGetByPosition(arguments[0]).column.get();
		const auto col_y = block.safeGetByPosition(arguments[1]).column.get();
		if (const_cnt == 0)
		{
				const auto col_vec_x = static_cast<const ColumnVector<Float64> *> (col_x);
				const auto col_vec_y = static_cast<const ColumnVector<Float64> *> (col_y);

				const auto dst = std::make_shared<ColumnVector<UInt8>>();
				block.safeGetByPosition(result).column = dst;
				auto & dst_data = dst->getData();
				dst_data.resize(size);

				size_t start_index = 0;
				for (const auto row : ext::range(0, size))
				{
					dst_data[row] = isPointInEllipses(col_vec_x->getData()[row], col_vec_y->getData()[row], ellipses, ellipses_count, start_index);
				}
			}
			else if (const_cnt == 2)
			{
				const auto col_const_x = static_cast<const ColumnConst<Float64> *> (col_x);
				const auto col_const_y = static_cast<const ColumnConst<Float64> *> (col_y);
				size_t start_index = 0;
				UInt8 res = isPointInEllipses(col_const_x->getData(), col_const_y->getData(), ellipses, ellipses_count, start_index);
				block.safeGetByPosition(result).column = std::make_shared<ColumnConst<UInt8>>(size, res);
			}
			else
			{
				throw Exception(
					"Illegal types " + col_x->getName() + ", " + col_y->getName() + " of arguments 1, 2 of function " + getName() + ". Both must be either const or vector",
					ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
			}
	}

	static bool isPointInEllipses(Float64 x, Float64 y, const Ellipse * ellipses, size_t ellipses_count, size_t & start_index)
	{
		size_t index = 0 + start_index;
		for (size_t i = 0; i < ellipses_count; ++i)
		{
			Ellipse el = ellipses[index];
			double p1 = ((x - el.x) / el.a);
			double p2 = ((y - el.y) / el.b);
			if (x <= el.x + el.a && x >= el.x - el.a && y <= el.y + el.b && y >= el.y - el.b /// Bounding box check
				&& p1 * p1 + p2 * p2 <= 1.0)	/// Precise check
			{
				start_index = index;
				return true;
			}
			++index;
			if (index == ellipses_count)
			{
				index = 0;
			}
		}
		return false;
	}
};

}

#undef DEGREES_IN_RADIANS