selectDialog.dart

import 'dart:async';

import 'package:flutter/material.dart';

import '../dropdown_search.dart';

class SelectDialog<T> extends StatefulWidget {
  final T selectedValue;
  final List<T> items;
  final bool showSearchBox;
  final bool isFilteredOnline;
  final ValueChanged<T> onChanged;
  final DropdownSearchOnFind<T> onFind;
  final DropdownSearchPopupItemBuilder<T> itemBuilder;
  final InputDecoration searchBoxDecoration;
  final DropdownSearchItemAsString<T> itemAsString;
  final DropdownSearchFilterFn<T> filterFn;
  final String hintText;
  final double maxHeight;
  final double dialogMaxWidth;
  final Widget popupTitle;
  final bool showSelectedItem;
  final DropdownSearchCompareFn<T> compareFn;
  final DropdownSearchPopupItemEnabled<T> itemDisabled;

  ///custom layout for empty results
  final EmptyBuilder emptyBuilder;

  ///custom layout for loading items
  final LoadingBuilder loadingBuilder;

  ///custom layout for error
  final ErrorBuilder errorBuilder;

  ///the search box will be focused if true
  final bool autoFocusSearchBox;

  ///text controller to set default search word for example
  final TextEditingController searchBoxController;

  ///delay before searching
  final Duration searchDelay;

  const SelectDialog({
    Key key,
    this.popupTitle,
    this.items,
    this.maxHeight,
    this.showSearchBox = false,
    this.isFilteredOnline = false,
    this.onChanged,
    this.selectedValue,
    this.onFind,
    this.itemBuilder,
    this.searchBoxDecoration,
    this.hintText,
    this.itemAsString,
    this.filterFn,
    this.showSelectedItem = false,
    this.compareFn,
    this.emptyBuilder,
    this.loadingBuilder,
    this.errorBuilder,
    this.autoFocusSearchBox = false,
    this.dialogMaxWidth,
    this.itemDisabled,
    this.searchBoxController,
    this.searchDelay,
  }) : super(key: key);

  @override
  _SelectDialogState<T> createState() => _SelectDialogState<T>();
}

class _SelectDialogState<T> extends State<SelectDialog<T>> {
  final FocusNode focusNode = new FocusNode();
  final StreamController<List<T>> _itemsStream = StreamController();
  final ValueNotifier<bool> _loadingNotifier = ValueNotifier(false);
  final List<T> _items = List<T>();
  Debouncer _debouncer;

  @override
  void initState() {
    super.initState();
    _debouncer = Debouncer(delay: widget.searchDelay);

    Future.delayed(
      Duration.zero,
      () => manageItemsByFilter(widget.searchBoxController?.text ?? '',
          isFistLoad: true),
    );
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (widget.autoFocusSearchBox)
      FocusScope.of(context).requestFocus(focusNode);
  }

  @override
  void dispose() {
    _itemsStream.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    Size deviceSize = MediaQuery.of(context).size;
    bool isTablet = deviceSize.width > deviceSize.height;
    double maxHeight = deviceSize.height * (isTablet ? .8 : .6);
    double maxWidth = deviceSize.width * (isTablet ? .7 : .9);

    return Container(
      width: widget.dialogMaxWidth ?? maxWidth,
      constraints: BoxConstraints(maxHeight: widget.maxHeight ?? maxHeight),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          _searchField(),
          Expanded(
            child: Stack(
              children: <Widget>[
                StreamBuilder<List<T>>(
                  stream: _itemsStream.stream,
                  builder: (context, snapshot) {
                    if (snapshot.hasError) {
                      return _errorWidget(snapshot?.error);
                    } else if (!snapshot.hasData) {
                      return _loadingWidget();
                    } else if (snapshot.data.isEmpty) {
                      if (widget.emptyBuilder != null)
                        return widget.emptyBuilder(
                            context, widget.searchBoxController?.text);
                      else
                        return const Center(
                          child: const Text("No data found"),
                        );
                    }
                    return ListView.builder(
                      shrinkWrap: true,
                      padding: EdgeInsets.symmetric(vertical: 0),
                      itemCount: snapshot.data.length,
                      itemBuilder: (context, index) {
                        var item = snapshot.data[index];
                        return _itemWidget(item);
                      },
                    );
                  },
                ),
                _loadingWidget()
              ],
            ),
          ),
        ],
      ),
    );
  }

  void _showErrorDialog(dynamic error) {
    showDialog(
      context: context,
      barrierDismissible: false,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text("Error while getting online items"),
          content: _errorWidget(error),
          actions: <Widget>[
            FlatButton(
              child: new Text("OK"),
              onPressed: () {
                Navigator.of(context).pop(false);
              },
            )
          ],
        );
      },
    );
  }

  Widget _errorWidget(dynamic error) {
    if (widget.errorBuilder != null)
      return widget.errorBuilder(
          context, widget.searchBoxController?.text, error);
    else
      return Padding(
        padding: EdgeInsets.all(8),
        child: Text(
          error?.toString() ?? 'Error',
        ),
      );
  }

  Widget _loadingWidget() {
    return ValueListenableBuilder(
        valueListenable: _loadingNotifier,
        builder: (context, bool isLoading, wid) {
          if (isLoading) {
            if (widget.loadingBuilder != null)
              return widget.loadingBuilder(
                  context, widget.searchBoxController?.text);
            else
              return Padding(
                padding: const EdgeInsets.all(24.0),
                child: const Center(
                  child: const CircularProgressIndicator(),
                ),
              );
          }
          return Container();
        });
  }

  void _onTextChanged(String filter) async {
    manageItemsByFilter(filter);
  }

  ///Function that filter item (online and offline) base on user filter
  ///[filter] is the filter keyword
  ///[isFirstLoad] true if it's the first time we load data from online, false other wises
  void manageItemsByFilter(String filter, {bool isFistLoad = false}) async {
    _loadingNotifier.value = true;

    List<T> applyFilter(String filter) {
      return _items.where((i) {
        if (widget.filterFn != null)
          return (widget.filterFn(i, filter));
        else if (i.toString().toLowerCase().contains(filter.toLowerCase()))
          return true;
        else if (widget.itemAsString != null) {
          return (widget.itemAsString(i))
                  ?.toLowerCase()
                  ?.contains(filter.toLowerCase()) ??
              false;
        }
        return false;
      }).toList();
    }

    //load offline data for the first time
    if (isFistLoad && widget.items != null) _items.addAll(widget.items);

    //manage offline items
    if (widget.onFind != null && (widget.isFilteredOnline || isFistLoad)) {
      try {
        final List<T> onlineItems = List();
        onlineItems.addAll(await widget.onFind(filter) ?? List());

        //Remove all old data
        _items.clear();
        //add offline items
        if (widget.items != null) _items.addAll(widget.items);
        //add new online items to list
        _items.addAll(onlineItems);

        _addDataToStream(applyFilter(filter));
      } catch (e) {
        _addErrorToStream(e);
        //if offline items count > 0 , the error will be not visible for the user
        //As solution we show it in dialog
        if (widget.items != null && widget.items.isNotEmpty) {
          _showErrorDialog(e);
          _addDataToStream(applyFilter(filter));
        }
      }
    } else {
      _addDataToStream(applyFilter(filter));
    }

    _loadingNotifier.value = false;
  }

  void _addDataToStream(List<T> data) {
    if (_itemsStream.isClosed) return;
    _itemsStream.add(data);
  }

  void _addErrorToStream(Object error, [StackTrace stackTrace]) {
    if (_itemsStream.isClosed) return;
    _itemsStream.addError(error, stackTrace);
  }

  Widget _itemWidget(T item) {
    if (widget.itemBuilder != null)
      return InkWell(
        child: widget.itemBuilder(
          context,
          item,
          _manageSelectedItemVisibility(item),
        ),
        onTap: widget.itemDisabled != null &&
                (widget.itemDisabled(item) ?? false) == true
            ? null
            : () {
                Navigator.pop(context, item);
                if (widget.onChanged != null) widget.onChanged(item);
              },
      );
    else
      return ListTile(
        title: Text(
          widget.itemAsString != null
              ? (widget.itemAsString(item) ?? "")
              : item.toString(),
        ),
        selected: _manageSelectedItemVisibility(item),
        onTap: widget.itemDisabled != null &&
                (widget.itemDisabled(item) ?? false) == true
            ? null
            : () {
                Navigator.pop(context, item);
                if (widget.onChanged != null) widget.onChanged(item);
              },
      );
  }

  /// selected item will be highlighted only when [widget.showSelectedItem] is true,
  /// if our object is String [widget.compareFn] is not required , other wises it's required
  bool _manageSelectedItemVisibility(T item) {
    if (!widget.showSelectedItem) return false;

    if (T == String) {
      return item == widget.selectedValue;
    } else {
      return widget.compareFn(item, widget.selectedValue);
    }
  }

  Widget _searchField() {
    return Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          widget.popupTitle ?? const SizedBox.shrink(),
          if (widget.showSearchBox)
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: TextField(
                controller: widget.searchBoxController,
                focusNode: focusNode,
                onChanged: (f) => _debouncer(() {
                  _onTextChanged(f);
                }),
                decoration: widget.searchBoxDecoration ??
                    InputDecoration(
                      hintText: widget.hintText,
                      border: const OutlineInputBorder(),
                      contentPadding:
                          const EdgeInsets.symmetric(horizontal: 16),
                    ),
              ),
            )
        ]);
  }
}

class Debouncer {
  final Duration delay;
  Timer _timer;

  Debouncer({this.delay});

  call(Function action) {
    _timer?.cancel();
    _timer = Timer(delay ?? const Duration(milliseconds: 500), action);
  }
}