gopatterns/pkg/pattern/point/between_point.go

package point

import (
	"math"

	"git.wtrh.nl/wouter/gopatterns/pkg/position"
	"git.wtrh.nl/wouter/gopatterns/pkg/vector"
	"github.com/tdewolff/canvas"
)

// BetweenPoint defines a point on the line between two other points.
type BetweenPoint struct {
	id     ID
	p      Point
	q      Point
	offset float64
	name   string
	draw   bool
	hide   bool
}

// NewBetweenPoint returns a new BetweenPoint relative to two other points p and q.
// The given offset defines where the new point is.
// With offset = 0 the new point is a p, offset = 0.5 results in a point exactly in the middle.
// Offset can be <0 (extending from p side) or >1 (extending from the q side).
func NewBetweenPoint(p, q Point, offset float64, id ID) *BetweenPoint {
	return &BetweenPoint{
		id:     id,
		p:      p,
		q:      q,
		offset: offset,
		name:   string(id),
	}
}

// Position calculates and returns the absolute [position.Position].
func (b *BetweenPoint) Position() position.Position {
	return position.Position{
		Vector:   b.p.Vector().Add(b.inBetween()),
		Rotation: b.p.Vector().AngleBetween(b.q.Vector()) - math.Pi/2,
	}
}

func (b *BetweenPoint) inBetween() vector.Vector {
	return b.q.Vector().Subtract(b.p.Vector()).Multiply(b.offset)
}

// Vector calculates and returns the absolute [vector.Vector].
func (b *BetweenPoint) Vector() vector.Vector {
	return b.Position().Vector
}

// Matrix calculates and returns the [canvas.Matrix] of a point.
func (b *BetweenPoint) Matrix() canvas.Matrix {
	return b.p.Matrix().Translate(b.inBetween().Values()).
		Rotate((b.p.Vector().AngleBetween(b.q.Vector()) - math.Pi/2) * 180 / math.Pi)
}

// ID returns the point ID.
func (b *BetweenPoint) ID() ID {
	return b.id
}

// Name returns the name of a point.
func (b *BetweenPoint) Name() string {
	return b.name
}

// Draw returns if the point should be drawn.
func (b *BetweenPoint) Draw() bool {
	return b.draw
}

// SetDraw indicates that the point should be drawn.
func (b *BetweenPoint) SetDraw() {
	b.draw = true
}

// UnsetDraw indicates that the point should not be drawn.
func (b *BetweenPoint) UnsetDraw() {
	b.draw = true
}

// Hide returns if the point must remain hidden.
func (b *BetweenPoint) Hide() bool {
	return b.hide
}

// SetHide indicates that the must be hidden.
func (b *BetweenPoint) SetHide() {
	b.hide = true
}