package viz

import (
	"bspviz/internal/bsp"
	"bytes"
	"fmt"
	"os"
)

func EmitDOT(root *bsp.Node, path string) error {
	var buf bytes.Buffer
	buf.WriteString("digraph BSP {\n")
	buf.WriteString("  node [fontname=\"Helvetica\"];\n")

	id := 0
	var walk func(*bsp.Node) int
	walk = func(n *bsp.Node) int {
		my := id
		id++
		if n.Leaf != nil {
			fmt.Fprintf(&buf, "  n%d [label=\"Leaf\\nSegs=%d\", shape=ellipse, style=filled, fillcolor=lightgray];\n",
				my, len(n.Leaf.Segs))
			return my
		}
		fmt.Fprintf(&buf, "  n%d [label=\"Split\\nO=(%.0f,%.0f) D=(%.0f,%.0f)\"];\n",
			my, n.O.X, n.O.Y, n.D.X, n.D.Y)
		l := walk(n.Left)
		r := walk(n.Right)
		fmt.Fprintf(&buf, "  n%d -> n%d [label=\"L\"];\n", my, l)
		fmt.Fprintf(&buf, "  n%d -> n%d [label=\"R\"];\n", my, r)
		return my
	}
	walk(root)

	buf.WriteString("}\n")
	return os.WriteFile(path, buf.Bytes(), 0644)
}