feat: serpentine map layout function

2026-06-11 23:12:29 +09:00
parent ee364cc2e2
commit 96304cc8a7
2 changed files with 61 additions and 0 deletions
@@ -0,0 +1,29 @@
+import 'dart:math' as math;
+import 'dart:ui';
+
+/// Deterministic serpentine layout for the journey map. Stage 0 is at the
+/// bottom; the path snakes upward. Works for any stage count.
+class MapLayout {
+  const MapLayout({
+    required this.width,
+    this.nodeSpacing = 108,
+    this.topPadding = 140,
+    this.bottomPadding = 150,
+  });
+
+  final double width;
+  final double nodeSpacing;
+  final double topPadding;
+  final double bottomPadding;
+
+  double get amplitude => width * 0.26;
+
+  double heightFor(int count) =>
+      topPadding + bottomPadding + (count - 1) * nodeSpacing;
+
+  Offset nodeCenter(int index, int count) {
+    final y = heightFor(count) - bottomPadding - index * nodeSpacing;
+    final x = width / 2 + amplitude * math.sin(index * 1.05);
+    return Offset(x, y);
+  }
+}