pathed_stack.dart

import 'package:flutter/material.dart';
import 'package:path_to_regexp/path_to_regexp.dart';

class PathStackEntry {
  PathStackEntry({required this.path, required this.builder, this.maintainState = true, this.aliases});
  final String path;
  // This wants the query string values
  final WidgetBuilder builder;
  final List<String>? aliases;
  final bool maintainState;
  // Paths ending with a / are assumed to allow prefixes on the end
  bool get allowSuffix => path.endsWith("/");
}

class PathStack extends StatefulWidget {
  static const kDefaultDuration = Duration(milliseconds: 250);

  final String path;
  final String parentPath;
  final List<PathStackEntry> entries;
  final bool caseSensitive;
  final Widget Function(BuildContext context, Widget child)? childBuilder;
  final Widget Function(BuildContext context)? unknownPathBuilder;
  final Widget Function(BuildContext context, Widget child, AnimationController animation)? transitionBuilder;
  final Duration transitionDuration;

  const PathStack({
    Key? key,
    required this.path,
    required this.entries,
    this.parentPath = "",
    this.caseSensitive = false,
    this.childBuilder,
    this.transitionBuilder,
    this.transitionDuration = kDefaultDuration,
    this.unknownPathBuilder,
  }) : super(key: key);

  @override
  PathStackState createState() => PathStackState();
}

class PathStackState extends State<PathStack> with SingleTickerProviderStateMixin {
  Map<String, Widget> _knownRoutes = {};
  String? _previousPath;
  late AnimationController transitionInAnim = AnimationController(vsync: this, duration: widget.transitionDuration)
    ..forward();

  @override
  Widget build(BuildContext context) {
    // Try and find a known route for the current path
    PathStackEntry? matchingRoute =
        List<PathStackEntry?>.from(widget.entries).firstWhere(checkEntryMatchesPath, orElse: () => null);
    // Fall back to first page in the route stack, TODO: Add a emptyRouteBuilder?
    if (matchingRoute == null) {
      print("WARNING: Unable to find a route for ${widget.path}");
      matchingRoute = PathStackEntry(
          path: "404",
          builder: (c) {
            return widget.unknownPathBuilder?.call(c) ?? Center(child: Text("Page Not Found"));
          });
    }
    // Use a UniqueKey if maintainState=false
    Key pageKey = matchingRoute.maintainState ? ValueKey(matchingRoute.path) : UniqueKey();
    // Add the new route to our list of known routes
    _knownRoutes[matchingRoute.path] = _KeyedWidget(key: pageKey, child: matchingRoute.builder.call(context));
    // Get all known children which we'll pass to the indexedStack
    List<Widget> children = _knownRoutes.values.toList();
    // Finds the index of the matching route, which we'll also pass to indexedStack
    int index = _knownRoutes.keys.toList().indexWhere((r) => r == matchingRoute!.path);
    // Remove non-persistent pages from the stack so they are not retained on next build
    if (matchingRoute.maintainState == false) {
      _knownRoutes.remove(matchingRoute.path);
    }
    Widget content = IndexedStack(index: index, children: children);
    if (_previousPath != matchingRoute.path) {
      transitionInAnim.forward(from: 0);
    }
    _previousPath = matchingRoute.path;
    content = widget.transitionBuilder?.call(context, content, transitionInAnim) ?? content;
    content = widget.childBuilder?.call(context, content) ?? content;
    return content;
  }

  void clearState() => _knownRoutes.clear();

  @override
  void dispose() {
    clearState();
    super.dispose();
  }

  bool checkEntryMatchesPath(PathStackEntry? entry) {
    List<String> allPaths = List.from([entry!.path, ...(entry.aliases ?? [])]);
    for (var i = 0; i < allPaths.length; i++) {
      final regExp = pathToRegExp('${widget.parentPath}${allPaths[i]}', prefix: entry.allowSuffix);
      if (regExp.hasMatch("${widget.path}")) return true;
    }
    return false;
  }
}

class _KeyedWidget extends StatelessWidget {
  const _KeyedWidget({Key? key, required this.child}) : super(key: key);
  final Widget child;
  @override
  Widget build(BuildContext context) => child;
}