Add debug line for spline drawing

cmd/gopatterns/gopatterns.go

@@ -40,6 +40,10 @@ gopatterns [-templates <template-dir>] [-out <output-dir>] input-file
 `)
 	}
 
+	if debug {
+		slog.SetLogLoggerLevel(slog.LevelDebug)
+	}
+
 	args := flag.Args()
 	if len(args) == 0 {
 		slog.Error("at least one pattern is required")

pkg/pattern/path/splines.go

@@ -5,6 +5,7 @@ import (
 	"git.wtrh.nl/patterns/gopatterns/pkg/pattern/point"
 	"github.com/tdewolff/canvas"
 	splines "gitlab.com/Achilleshiel/gosplines"
+	"log/slog"
 )
 
 const resolution = 40
@@ -44,8 +45,41 @@ func NewSpline(opts SplineOpts) Spline {
 
 // Draw the spline to the provided [canvas.Canvas].
 func (s Spline) Draw(c *canvas.Canvas) error {
+	points, err := s.build()
+	if err != nil {
+		return fmt.Errorf("generating spline: %w", err)
+	}
+
+	path := NewPath(points, s.style)
+
+	if err = path.Draw(c); err != nil {
+		return fmt.Errorf("draw spline points to canvas: %w", err)
+	}
+
+	length, _ := s.Length()
+	slog.Debug("Draw spline", "length", length, "from", points[0].Name(), "to", points[len(points)-1].Name())
+
+	return nil
+}
+
+func (s Spline) Length() (float64, error) {
+	points, err := s.build()
+	if err != nil {
+		return 0.0, fmt.Errorf("generating spline: %w", err)
+	}
+
+	length := 0.0
+
+	for i := range points[1:] {
+		length += points[i].Position().Distance(points[i+1].Position())
+	}
+
+	return length, nil
+}
+
+func (s Spline) build() (points []point.Point, err error) {
 	if len(s.points) < 2 {
-		return nil
+		return s.points, nil
 	}
 
 	x := make([]float64, len(s.points))
@@ -60,15 +94,15 @@ func (s Spline) Draw(c *canvas.Canvas) error {
 
 	xCoefficient, err := splines.SolveSplineWithConstraint(x, diffStart.X, diffEnd.X)
 	if err != nil {
-		return fmt.Errorf("unable to calculate coefficients for x: %w", err)
+		return nil, fmt.Errorf("unable to calculate coefficients for x: %w", err)
 	}
 
 	yCoefficient, err := splines.SolveSplineWithConstraint(y, diffStart.Y, diffEnd.Y)
 	if err != nil {
-		return fmt.Errorf("unable to calculate coefficients for y: %w", err)
+		return nil, fmt.Errorf("unable to calculate coefficients for y: %w", err)
 	}
 
-	points := make([]point.Point, 0, len(x)*resolution)
+	points = make([]point.Point, 0, len(x)*resolution)
 	stepSize := 1.0 / float64(resolution-1)
 
 	for i := range len(s.points) - 1 {
@@ -83,11 +117,5 @@ func (s Spline) Draw(c *canvas.Canvas) error {
 
 	points = append(points, s.points[len(s.points)-1])
 
-	path := NewPath(points, s.style)
-
-	if err = path.Draw(c); err != nil {
-		return fmt.Errorf("draw spline points to canvas: %w", err)
-	}
-
-	return nil
+	return points, nil
 }