#pragma once

/* greebo: This file contains the templated class definition of the two-component vector
 *
 * BasicVector2: A vector with two components of type <Element>
 *
 * The BasicVector2 is equipped with the most important operators like *, *= and so on.
 *
 * Note: The most commonly used Vector2 is a BasicVector2<double>, this is also defined in this file
 *
 * Note: that the multiplication of a Vector2 with another one (Vector2*Vector2) does NOT
 * result in an inner product but in a component-wise scaling. Use the .dot() method to
 * execute an inner product of two vectors.
 */

#include "lrint.h"
#include <sstream>
#include <cmath>
#include <fmt/format.h>

template <typename Element>
class BasicVector2 {

	// This is where the components of the vector are stored.
	Element _v[2];

public:
	// Public typedef to read the type of our elements
	typedef Element ElementType;

	// Constructor with no arguments
  	BasicVector2() {
  		_v[0] = 0;
  		_v[1] = 0;
  	}

  	// Templated copy constructor
	template<typename OtherElement>
	BasicVector2(const BasicVector2<OtherElement>& other) {
		x() = static_cast<Element>(other.x());
		y() = static_cast<Element>(other.y());
	}

  	/** Construct a BasicVector2 with the 2 provided components.
     */
    BasicVector2(const Element& x_, const Element& y_) {
        _v[0] = x_;
        _v[1] = y_;
    }

	/** Construct a BasicVector2 from a 2-element array. The array must be
	 * valid as no bounds checking is done.
	 */
	BasicVector2(const Element* array) {
		for (int i = 0; i < 2; ++i)
			_v[i] = array[i];
	}

    /** Construct a BasicVector2 by parsing the supplied string. The string
     * must contain 2 numeric values separated by whitespace.
     *
     * @param str
     * The string from which component values are extracted.
     */

    BasicVector2(const std::string& str) {
    	// Initialise the vector with 0, in case the string parse fails
    	_v[0] = _v[1] = 0;
    	// Use a stringstream to parse the string
        std::stringstream strm(str);
        strm << std::skipws;
        strm >> x();
        strm >> y();
    }

    /** Construct a BasicVector2 out of 2 elements of type OtherType
     */
    template <typename OtherType>
  	BasicVector2(OtherType x, OtherType y) {
    	_v[0] = static_cast<Element>(x);
    	_v[1] = static_cast<Element>(y);
    }

    // Return NON-CONSTANT references to the vector components
    Element& x() {
    	return _v[0];
    }
    Element& y() {
    	return _v[1];
  	}

  	// Return CONSTANT references to the vector components
  	const Element& x() const {
    	return _v[0];
  	}
  	const Element& y() const {
    	return _v[1];
  	}

	/**
	 * Operator cast to Element*. Also provides operator[] due to the inbuilt
	 * operation on a pointer type.
	 */
	operator Element* () {
		return _v;
	}

	/**
	 * Operator cast to const Element*.
	 */
	operator const Element* () const {
		return _v;
	}

  	Element* data() {
    	return _v;
  	}
  	const Element* data() const {
    	return _v;
  	}

  	/** Compare this BasicVector2 against another for equality.
	 */
	bool operator== (const BasicVector2& other) const {
		return (other.x() == x() && other.y() == y());
	}

	/** Compare this BasicVector2 against another for inequality.
	 */
	bool operator!= (const BasicVector2& other) const {
		return !(*this == other);
	}

	/*	Define the negation operator -
	 *  All the vector's components are negated
	 */
	BasicVector2<Element> operator- () const {
		return BasicVector2<Element>(
			-_v[0],
			-_v[1]
		);
	}

	/*	Define the addition operators + and += with any other BasicVector2 of type OtherElement
	 *  The vectors are added to each other element-wise
	 */
	template<typename OtherElement>
	BasicVector2<Element> operator+ (const BasicVector2<OtherElement>& other) const {
		return BasicVector2<Element>(
			_v[0] + static_cast<Element>(other.x()),
			_v[1] + static_cast<Element>(other.y())
		);
	}

	template<typename OtherElement>
	BasicVector2<Element>& operator+= (const BasicVector2<OtherElement>& other) {
		_v[0] += static_cast<Element>(other.x());
		_v[1] += static_cast<Element>(other.y());
		return *this;
	}

	/*	Define the substraction operators - and -= with any other BasicVector2 of type OtherElement
	 *  The vectors are substracted from each other element-wise
	 */
	template<typename OtherElement>
	BasicVector2<Element> operator- (const BasicVector2<OtherElement>& other) const {
		return BasicVector2<Element>(
			_v[0] - static_cast<Element>(other.x()),
			_v[1] - static_cast<Element>(other.y())
		);
	}

	template<typename OtherElement>
	BasicVector2<Element>& operator-= (const BasicVector2<OtherElement>& other) {
		_v[0] -= static_cast<Element>(other.x());
		_v[1] -= static_cast<Element>(other.y());
		return *this;
	}

	/*	Define the multiplication operators * and *= with another Vector2 of type OtherElement
	 *
	 *  The vectors are multiplied element-wise
	 *
	 *  greebo: This is mathematically kind of senseless, as this is a mixture of
	 *  a dot product and scalar multiplication. It can be used to scale each
	 *  vector component by a different factor, so maybe this comes in handy.
	 */
	template<typename OtherElement>
	BasicVector2<Element> operator* (const BasicVector2<OtherElement>& other) const {
		return BasicVector2<Element>(
			_v[0] * static_cast<Element>(other.x()),
			_v[1] * static_cast<Element>(other.y())
		);
	}

	template<typename OtherElement>
	BasicVector2<Element>& operator*= (const BasicVector2<OtherElement>& other) {
		_v[0] *= static_cast<Element>(other.x());
		_v[1] *= static_cast<Element>(other.y());
		return *this;
	}


	/*	Define the multiplications * and *= with a scalar
	 */
	template<typename OtherElement>
	BasicVector2<Element> operator* (const OtherElement& other) const {
		Element factor = static_cast<Element>(other);
		return BasicVector2<Element>(
			_v[0] * factor,
			_v[1] * factor
		);
	}

	template<typename OtherElement>
	BasicVector2<Element>& operator*= (const OtherElement& other) {
		Element factor = static_cast<Element>(other);
		_v[0] *= factor;
		_v[1] *= factor;
		return *this;
	}

	/*	Define the division operators / and /= with another Vector2 of type OtherElement
	 *  The vectors are divided element-wise
	 */
	template<typename OtherElement>
	BasicVector2<Element> operator/ (const BasicVector2<OtherElement>& other) const {
		return BasicVector2<Element>(
			_v[0] / static_cast<Element>(other.x()),
			_v[1] / static_cast<Element>(other.y())
		);
	}

	template<typename OtherElement>
	BasicVector2<Element>& operator/= (const BasicVector2<OtherElement>& other) {
		_v[0] /= static_cast<Element>(other.x());
		_v[1] /= static_cast<Element>(other.y());
		return *this;
	}

	/*	Define the scalar divisions / and /=
	 */
	template<typename OtherElement>
	BasicVector2<Element> operator/ (const OtherElement& other) const {
		Element divisor = static_cast<Element>(other);
		return BasicVector2<Element>(
			_v[0] / divisor,
			_v[1] / divisor
		);
	}

	template<typename OtherElement>
	BasicVector2<Element>& operator/= (const OtherElement& other) {
		Element divisor = static_cast<Element>(other);
		_v[0] /= divisor;
		_v[1] /= divisor;
		return *this;
	}

	/** Cast to std::string
	 */
	operator std::string() const
	{
		return fmt::format("{0:f} {1:f}", _v[0], _v[1]);
	}

	/** Return the length of this vector.
     *
     * @returns
     * The Pythagorean length of this vector.
     */
	double getLength() const {
		double lenSquared = _v[0]*_v[0] +
							_v[1]*_v[1];
		return sqrt(lenSquared);
	}

	/** Return the squared length of this vector.
     */
	double getLengthSquared() const {
		double lenSquared = _v[0]*_v[0] +
							_v[1]*_v[1];
		return lenSquared;
	}

    /**
     * \brief Normalise this vector in-place by scaling by the inverse of its
     * size.

     * \return The length of the vector before normalisation.
     */
    double normalise()
    {
        auto length = getLength();

        _v[0] /= length;
        _v[1] /= length;

        return length;
    }

    /// Return the result of normalising this vector
    BasicVector2<Element> getNormalised() const
    {
        auto length = getLength();
        return { _v[0] / length, _v[1] / length };
    }

	/* Scalar product this vector with another Vector2,
	 * returning the projection of <self> onto <other>
	 *
	 * @param other
	 * The Vector2 to dot-product with this Vector2.
	 *
	 * @returns
	 * The inner product (a scalar): a[0]*b[0] + a[1]*b[1]
	 */
	template<typename OtherT>
	Element dot(const BasicVector2<OtherT>& other) const {
		return 	Element(_v[0] * other.x() +
						_v[1] * other.y());
	}

	/* Cross-product this vector with another Vector2, returning the scalar result
	 *
	 * @param other
	 * The Vector2 to cross-product with this Vector2.
	 *
	 * @returns
	 * The cross-product of the two vectors, a scalar: a[0]*b[1] - b[0]*a[1]
	 */
	template<typename OtherT>
	Element crossProduct(const BasicVector2<OtherT>& other) const {
		return Element(_v[0] * other.y() - _v[1] * other.x());
	}

	// Returns the mid-point of this vector and the other one
	BasicVector2<Element> mid(const BasicVector2<Element>& other) const
	{
		return (*this + other) * 0.5f;
	}
};

// ==========================================================================================

/// A 2-element vector stored in double-precision floating-point.
using Vector2 = BasicVector2<double>;

// A 2-element vector stored in single-precision floating point format
using Vector2f = BasicVector2<float>;

/// 2-element vector of signed integer
using Vector2i = BasicVector2<int>;

// Stream insertion operator for a BasicVector2
template<typename T>
std::ostream& operator<<(std::ostream& st, BasicVector2<T> vec) {
	st << "<" << vec.x() << ", " << vec.y() << ">";
	return st;
}

namespace math
{

template<typename T>
inline bool isNear(const BasicVector2<T>& v1, const BasicVector2<T>& v2, double epsilon)
{
    BasicVector2<T> diff = v1 - v2;
    return std::abs(diff.x()) < epsilon && std::abs(diff.y()) < epsilon;
}

}