// Package position is a simple 2D position library.
// Positions consist of a vector.Vector and a rotation.
package position

import (
	"math"

	"git.wtrh.nl/wouter/gopatterns/pkg/vector"
)

// Position contains a 2D vector and a rotation angle.
type Position struct {
	Vector   vector.Vector
	Rotation float64
}

// Add a position.
func (p Position) Add(q Position) Position {
	return Position{
		Vector:   p.Vector.Add(q.Vector.Rotate(p.Rotation)),
		Rotation: p.Rotation + q.Rotation,
	}
}

// Translate the position to a new reference frame.
func (p Position) Translate(q Position) Position {
	q.Vector = q.Vector.Span(q.Rotation)
	return p.Add(q)
}

// Distance returns the distance between two positions.
func (p Position) Distance(q Position) float64 {
	return p.Vector.Distance(q.Vector)
}

// Direction returns the angle to another position.
func (p Position) Direction(q Position) float64 {
	return math.Remainder(p.Vector.AngleBetween(q.Vector)-p.Rotation, 2*math.Pi)
}