import "package:flutter/widgets.dart";

import "menu.dart";

const double _kContextMenuGap = 8.0;
const double _kContextMenuScreenPadding = 8.0;
const double _kContextMenuMinWidth = 192.0;

// shows a right-click style context menu at [globalPosition]. used to lean on
// shadcn's OverlayManager.showMenu; now its a plain flutter Overlay entry with
// a transparent tap-catcher to dismiss.
void showContextMenu({
  required BuildContext context,
  required Offset globalPosition,
  required List<MenuItem> items,
  required VoidCallback onDismissed,
}) {
  final overlay = Overlay.of(context, rootOverlay: true);
  final overlayBox = overlay.context.findRenderObject() as RenderBox?;
  final overlayPosition =
      overlayBox?.globalToLocal(globalPosition) ?? globalPosition;

  late OverlayEntry entry;
  var closed = false;
  void close() {
    if (closed) return;
    closed = true;
    entry.remove();
    onDismissed();
  }

  entry = OverlayEntry(
    builder: (ctx) {
      return Stack(
        children: [
          // tap anywhere outside to dismiss.
          Positioned.fill(
            child: GestureDetector(
              behavior: HitTestBehavior.opaque,
              excludeFromSemantics: true,
              onTap: close,
              child: const SizedBox.expand(),
            ),
          ),
          CustomSingleChildLayout(
            delegate: _ContextMenuLayoutDelegate(position: overlayPosition),
            child: MenuGroup(
              direction: Axis.vertical,
              subMenuOffset: const Offset(8, -4),
              onDismissed: close,
              builder: (ctx, children) => MenuPopup(children: children),
              children: items,
            ),
          ),
        ],
      );
    },
  );

  overlay.insert(entry);
}

class _ContextMenuLayoutDelegate extends SingleChildLayoutDelegate {
  const _ContextMenuLayoutDelegate({required this.position});

  final Offset position;

  @override
  BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
    final maxWidth = (constraints.maxWidth - _kContextMenuScreenPadding * 2)
        .clamp(0.0, double.infinity);
    final maxHeight = (constraints.maxHeight - _kContextMenuScreenPadding * 2)
        .clamp(0.0, double.infinity);
    return BoxConstraints(
      minWidth: _kContextMenuMinWidth.clamp(0.0, maxWidth),
      maxWidth: maxWidth,
      maxHeight: maxHeight,
    );
  }

  @override
  Offset getPositionForChild(Size size, Size childSize) {
    final minLeft = _kContextMenuScreenPadding;
    final minTop = _kContextMenuScreenPadding;
    final maxLeft = size.width - _kContextMenuScreenPadding - childSize.width;
    final maxTop = size.height - _kContextMenuScreenPadding - childSize.height;

    final preferredRight = position.dx + _kContextMenuGap;
    final preferredLeft = position.dx - _kContextMenuGap - childSize.width;
    final rightFits =
        preferredRight + childSize.width <=
        size.width - _kContextMenuScreenPadding;
    final leftFits = preferredLeft >= _kContextMenuScreenPadding;
    final opensRight = rightFits || !leftFits;
    final rawLeft = opensRight ? preferredRight : preferredLeft;

    final preferredBelow = position.dy;
    final preferredAbove = position.dy - childSize.height;
    final belowFits =
        preferredBelow + childSize.height <=
        size.height - _kContextMenuScreenPadding;
    final aboveFits = preferredAbove >= _kContextMenuScreenPadding;
    final opensBelow = belowFits || !aboveFits;
    final rawTop = opensBelow ? preferredBelow : preferredAbove;

    return Offset(
      rawLeft.clamp(minLeft, maxLeft.clamp(minLeft, double.infinity)),
      rawTop.clamp(minTop, maxTop.clamp(minTop, double.infinity)),
    );
  }

  @override
  bool shouldRelayout(_ContextMenuLayoutDelegate oldDelegate) {
    return position != oldDelegate.position;
  }
}