/*
 * Copyright (c) 2017-2019 ARM Limited.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#pragma once

#include <cmath>
#include <list>
#include <ostream>
#include <sstream>
#include <limits>
#include <string>

namespace vkb
{
/** Generic measurement that stores values as either double or long long int. */
struct Measurement
{
	/** Measurement value */
	struct Value
	{
		/** Constructor
         *
         * @param[in] is_floating Will the value stored be floating point ?
         */
		Value(bool is_floating) :
		    v{0},
		    is_floating_point(is_floating)
		{
		}

		/** Add the value stored to the stream as a string
         */
		friend std::ostream &operator<<(std::ostream &os, const Value &value)
		{
			std::stringstream ss;
			ss << std::fixed;

			if (value.is_floating_point)
			{
				ss.precision(4);
				ss << value.v.floating_point;
			}
			else
			{
				ss.precision(std::numeric_limits<long long>::digits10 + 1);
				ss << value.v.integer;
			}

			return os << ss.str();
		}
		/** Convert the value stored to string
         */
		std::string to_string() const
		{
			std::stringstream ss;
			ss << *this;
			return ss.str();
		}
		/** Add with another value and return the sum
         *
         * @param[in] b Other value
         *
         * @return Sum of the stored value + b
         */
		Value operator+(Value b) const
		{
			if (is_floating_point)
			{
				b.v.floating_point += v.floating_point;
			}
			else
			{
				b.v.integer += v.integer;
			}
			return b;
		}

		/** Subtract with another value and return the result
         *
         * @param[in] b Other value
         *
         * @return Result of the stored value - b
         */
		Value operator-(Value b) const
		{
			if (is_floating_point)
			{
				b.v.floating_point -= v.floating_point;
			}
			else
			{
				b.v.integer -= v.integer;
			}
			return b;
		}

		/** Multiple with another value and return the result
         *
         * @param[in] b Other value
         *
         * @return Result of the stored value * b
         */
		Value operator*(Value b) const
		{
			if (is_floating_point)
			{
				b.v.floating_point *= v.floating_point;
			}
			else
			{
				b.v.integer *= v.integer;
			}
			return b;
		}

		/** Return the stored value divided by an integer.
         *
         * @param[in] b Integer to divide the value by.
         *
         * @return Stored value / b
         */
		Value operator/(int b) const
		{
			Value res(is_floating_point);
			if (is_floating_point)
			{
				res.v.floating_point = v.floating_point / b;
			}
			else
			{
				res.v.integer = v.integer / b;
			}
			return res;
		}

		/** Subtract another value and return the updated stored value.
         *
         * @param[in] b Other value
         *
         * @return The updated stored value
         */
		Value &operator-=(const Value &b)
		{
			if (is_floating_point)
			{
				v.floating_point -= b.v.floating_point;
			}
			else
			{
				v.integer -= b.v.integer;
			}
			return *this;
		}

		/** Compare the stored value with another value
         *
         * @param[in] b Value to compare against
         *
         * @return The result of stored value < b
         */
		bool operator<(const Value &b) const
		{
			if (is_floating_point)
			{
				return v.floating_point < b.v.floating_point;
			}
			else
			{
				return v.integer < b.v.integer;
			}
		}

		/** Get the relative standard deviation to a given distribution as a percentage.
         *
         * @param[in] variance The variance of the distribution.
         * @param[in] mean     The mean of the distribution.
         *
         * @return the relative standard deviation.
         */
		static double relative_standard_deviation(const Value &variance, const Value &mean)
		{
			if (variance.is_floating_point)
			{
				return 100.0 * std::sqrt(variance.v.floating_point) / mean.v.floating_point;
			}
			else
			{
				return 100.0 * std::sqrt(static_cast<double>(variance.v.integer)) / mean.v.integer;
			}
		}

		/** Stored value */
		union
		{
			double        floating_point;
			long long int integer;
		} v;
		bool is_floating_point; /**< Is the stored value floating point or integer ? */
	};

	/** Compare the stored value with another value
     *
     * @param[in] b Value to compare against
     *
     * @return The result of stored value < b
     */
	bool operator<(const Measurement &b) const
	{
		return _value < b.value();
	}

	/** Stream output operator to print the measurement.
     *
     * Prints value and unit.
     *
     * @param[out] os          Output stream.
     * @param[in]  measurement Measurement.
     *
     * @return the modified output stream.
     */
	friend inline std::ostream &operator<<(std::ostream &os, const Measurement &measurement)
	{
		os << measurement._value << " " << measurement._unit;
		return os;
	}

	/** Constructor to store a floating point value
     *
     * @param[in] v    Value to store
     * @param[in] unit Unit of @p v
     * @param[in] raw  (Optional) The raw value(s) @p was generated from.
     */
	template <typename Floating, typename std::enable_if<!std::is_integral<Floating>::value, int>::type = 0>
	Measurement(Floating v, std::string unit, std::list<std::string> raw = {}) :
	    _unit(unit),
	    _raw_data(std::move(raw)),
	    _value(true)
	{
		_value.v.floating_point = static_cast<double>(v);
		if (_raw_data.empty())
		{
			_raw_data = {_value.to_string()};
		}
	}

	/** Constructor to store an integer value
     *
     * @param[in] v    Value to store
     * @param[in] unit Unit of @p v
     * @param[in] raw  (Optional) The raw value(s) @p was generated from.
     */
	template <typename Integer, typename std::enable_if<std::is_integral<Integer>::value, int>::type = 0>
	Measurement(Integer v, std::string unit, std::list<std::string> raw = {}) :
	    _unit(unit),
	    _raw_data(std::move(raw)),
	    _value(false)
	{
		_value.v.integer = static_cast<long long int>(v);
		if (_raw_data.empty())
		{
			_raw_data = {_value.to_string()};
		}
	}

	/** Accessor for the unit of the measurement
     *
     * @return Unit of the measurement
     */
	const std::string &unit() const
	{
		return _unit;
	}

	/** Accessor for the raw data
     *
     * @return The raw data
     */
	const std::list<std::string> &raw_data() const
	{
		return _raw_data;
	}

	/** Accessor for the stored value
     *
     * @return The stored value
     */
	const Value &value() const
	{
		return _value;
	}

  private:
	std::string            _unit;
	std::list<std::string> _raw_data;
	Value                  _value;
};

}        // namespace vkb