gopatterns/pkg/pattern/point/extend_point.go

package point

import (
	"git.wtrh.nl/patterns/gopatterns/pkg/position"
	"git.wtrh.nl/patterns/gopatterns/pkg/vector"
	"github.com/tdewolff/canvas"
	"math"
)

// ExtendPoint defines a point on the line between two other points.
type ExtendPoint struct {
	id     ID
	from   Point
	to     Point
	extend float64
	name   string
	draw   bool
	hide   bool
}

// NewExtendPoint returns a new ExtendPoint relative to two other points from and to.
// The given offset defines where the new point is.
// With offset = 0 the new point is a from, offset = 0.5 results in a point exactly in the middle.
func NewExtendPoint(from, to Point, extend float64, id ID) *ExtendPoint {
	return &ExtendPoint{
		id:     id,
		from:   from,
		to:     to,
		extend: extend,
		name:   string(id),
	}
}

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

func (b *ExtendPoint) extendedVector() vector.Vector {
	return b.to.Vector().Subtract(b.from.Vector()).Unit().Multiply(b.extend)
}

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

// Matrix calculates and returns the [canvas.Matrix] of a point.
func (b *ExtendPoint) Matrix() canvas.Matrix {
	return b.to.Matrix().Translate(b.extendedVector().Values()).
		Rotate((b.from.Vector().AngleBetween(b.to.Vector()) - math.Pi/2) * 180 / math.Pi)
}

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

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

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

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

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

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

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