feat(render): add JSON output format for tower layout

- Add JSON tags to Layout and Block structs
- Add RenderJSON sink alongside RenderSVG
- Add --format flag to render command (svg default, json)

Author: matzehuels

internal/cli/render.go

@@ -41,6 +41,7 @@ type renderOpts struct {
 	nebraska     bool
 	popups       bool
 	topDown      bool
+	format       string
 }
 
 func newRenderCmd() *cobra.Command {
@@ -83,6 +84,7 @@ func newRenderCmd() *cobra.Command {
 	cmd.Flags().BoolVar(&opts.nebraska, "nebraska", false, "show Nebraska guy maintainer ranking")
 	cmd.Flags().BoolVar(&opts.popups, "popups", opts.popups, "show hover popups with metadata")
 	cmd.Flags().BoolVar(&opts.topDown, "top-down", false, "use top-down width flow (roots get equal width)")
+	cmd.Flags().StringVar(&opts.format, "format", "svg", "output format: svg (default), json")
 
 	return cmd
 }
@@ -228,8 +230,16 @@ func renderTower(ctx context.Context, g *dag.DAG, opts *renderOpts) ([]byte, err
 		layout = layouttransform.Randomize(layout, g, defaultSeed, nil)
 	}
 
-	logger.Infof("Rendering tower SVG (%s style)", opts.style)
-	return tower.RenderSVG(layout, buildRenderOpts(g, opts)...), nil
+	switch opts.format {
+	case "json":
+		logger.Info("Rendering tower layout as JSON")
+		return tower.RenderJSON(layout)
+	case "svg", "":
+		logger.Infof("Rendering tower SVG (%s style)", opts.style)
+		return tower.RenderSVG(layout, buildRenderOpts(g, opts)...), nil
+	default:
+		return nil, fmt.Errorf("unknown format: %s (must be 'svg' or 'json')", opts.format)
+	}
 }
 
 func buildLayoutOpts(ctx context.Context, opts *renderOpts) ([]tower.Option, error) {

pkg/render/tower/block.go

@@ -1,13 +1,32 @@
 package tower
 
 type Block struct {
-	NodeID      string
-	Left, Right float64
-	Bottom, Top float64
+	NodeID string  `json:"id"`
+	Left   float64 `json:"x"`
+	Right  float64 `json:"-"`
+	Bottom float64 `json:"y"`
+	Top    float64 `json:"-"`
 }
 
-func (b Block) Width() float64  { return b.Right - b.Left }
-func (b Block) Height() float64 { return b.Top - b.Bottom }
-
+func (b Block) Width() float64   { return b.Right - b.Left }
+func (b Block) Height() float64  { return b.Top - b.Bottom }
 func (b Block) CenterX() float64 { return (b.Left + b.Right) / 2 }
 func (b Block) CenterY() float64 { return (b.Bottom + b.Top) / 2 }
+
+type jsonBlock struct {
+	ID     string  `json:"id"`
+	X      float64 `json:"x"`
+	Y      float64 `json:"y"`
+	Width  float64 `json:"width"`
+	Height float64 `json:"height"`
+}
+
+func (b Block) MarshalJSON() ([]byte, error) {
+	return jsonMarshal(jsonBlock{
+		ID:     b.NodeID,
+		X:      b.Left,
+		Y:      b.Bottom,
+		Width:  b.Width(),
+		Height: b.Height(),
+	})
+}

pkg/render/tower/json.go

@@ -0,0 +1,11 @@
+package tower
+
+import "encoding/json"
+
+func RenderJSON(layout Layout) ([]byte, error) {
+	return json.MarshalIndent(layout, "", "  ")
+}
+
+func jsonMarshal(v any) ([]byte, error) {
+	return json.Marshal(v)
+}

pkg/render/tower/layout.go

@@ -13,10 +13,12 @@ const (
 )
 
 type Layout struct {
-	FrameWidth, FrameHeight float64
-	Blocks                  map[string]Block
-	RowOrders               map[int][]string
-	MarginX, MarginY        float64
+	FrameWidth  float64          `json:"width"`
+	FrameHeight float64          `json:"height"`
+	Blocks      map[string]Block `json:"blocks"`
+	RowOrders   map[int][]string `json:"rows,omitempty"`
+	MarginX     float64          `json:"margin_x"`
+	MarginY     float64          `json:"margin_y"`
 }
 
 type Option func(*config)