import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:paperless_api/paperless_api.dart';
import 'package:paperless_mobile/core/extensions/flutter_extensions.dart';
import 'package:paperless_mobile/generated/l10n/app_localizations.dart';

class FullscreenLabelForm<T extends Label> extends StatefulWidget {
  /// If null, this will resolve to [UnsetIdQueryParameter].
  final IdQueryParameter initialValue;

  final Map<int, T> options;
  final Future<T?> Function(String? initialName)? onCreateNewLabel;
  final bool showNotAssignedOption;
  final bool showAnyAssignedOption;
  final void Function({IdQueryParameter returnValue}) onSubmit;
  final Widget leadingIcon;
  final String? addNewLabelText;
  final bool autofocus;
  final bool allowSelectUnassigned;
  final bool canCreateNewLabel;

  FullscreenLabelForm({
    super.key,
    this.initialValue = const UnsetIdQueryParameter(),
    required this.options,
    required this.onCreateNewLabel,
    this.showNotAssignedOption = true,
    this.showAnyAssignedOption = true,
    required this.onSubmit,
    required this.leadingIcon,
    this.addNewLabelText,
    this.autofocus = true,
    this.allowSelectUnassigned = true,
    required this.canCreateNewLabel,
  })  : assert(!(initialValue.isOnlyAssigned) || showAnyAssignedOption),
        assert(!(initialValue.isOnlyNotAssigned) || showNotAssignedOption),
        assert((addNewLabelText != null) == (onCreateNewLabel != null));

  @override
  State<FullscreenLabelForm> createState() => _FullscreenLabelFormState();
}

class _FullscreenLabelFormState<T extends Label>
    extends State<FullscreenLabelForm<T>> {
  bool _showClearIcon = false;
  final _textEditingController = TextEditingController();
  final _focusNode = FocusNode();

  @override
  void initState() {
    super.initState();
    _textEditingController.addListener(() {
      setState(() => _showClearIcon = _textEditingController.text.isNotEmpty);
    });
    if (widget.autofocus) {
      WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
        //Delay keyboard popup to ensure open animation is finished before.
        Future.delayed(
          const Duration(milliseconds: 200),
          () => _focusNode.requestFocus(),
        );
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    final showFab = MediaQuery.viewInsetsOf(context).bottom == 0;
    final theme = Theme.of(context);
    final options = _filterOptionsByQuery(_textEditingController.text);
    return Scaffold(
      appBar: AppBar(
        backgroundColor: theme.colorScheme.surface,
        toolbarHeight: 72,
        leading: BackButton(
          color: theme.colorScheme.onSurface,
        ),
        title: TextFormField(
          focusNode: _focusNode,
          controller: _textEditingController,
          onFieldSubmitted: (value) {
            FocusScope.of(context).unfocus();
            final index = AutocompleteHighlightedOption.of(context);
            final value = index.isNegative ? null : options.elementAt(index);
            widget.onSubmit(
              returnValue: switch (value) {
                SetIdQueryParameter query => query,
                _ => const UnsetIdQueryParameter(),
              },
            );
          },
          autofocus: true,
          style: theme.textTheme.bodyLarge?.apply(
            color: theme.colorScheme.onSurface,
          ),
          decoration: InputDecoration(
            contentPadding: EdgeInsets.zero,
            hintStyle: theme.textTheme.bodyLarge?.apply(
              color: theme.colorScheme.onSurfaceVariant,
            ),
            icon: widget.leadingIcon,
            hintText: _buildHintText(),
            border: InputBorder.none,
          ),
          textInputAction: TextInputAction.done,
        ),
        actions: [
          if (_showClearIcon)
            IconButton(
              icon: const Icon(Icons.clear),
              onPressed: () {
                _textEditingController.clear();
              },
            ),
        ],
        bottom: PreferredSize(
          preferredSize: const Size.fromHeight(1),
          child: Divider(
            color: theme.colorScheme.outline,
          ),
        ),
      ),
      floatingActionButton: showFab && widget.onCreateNewLabel != null
          ? FloatingActionButton(
              heroTag: "fab_label_form",
              onPressed: _onCreateNewLabel,
              child: const Icon(Icons.add),
            )
          : null,
      body: Builder(builder: (context) {
        return Column(
          children: [
            Expanded(
              child: ListView.builder(
                padding: EdgeInsets.zero,
                shrinkWrap: true,
                itemCount: options.length,
                itemBuilder: (BuildContext context, int index) {
                  final option = options.elementAt(index);
                  final shouldHighlight = switch (option) {
                    NotAssignedIdQueryParameter() => true,
                    AnyAssignedIdQueryParameter() => true,
                    SetIdQueryParameter(id: var id) =>
                      (widget.options[id]?.documentCount ?? 0) > 0,
                    _ => false,
                  };
                  final highlight =
                      AutocompleteHighlightedOption.of(context) == index;
                  if (highlight && shouldHighlight) {
                    SchedulerBinding.instance
                        .addPostFrameCallback((Duration timeStamp) {
                      Scrollable.ensureVisible(
                        context,
                        alignment: 0,
                      );
                    });
                  }
                  return _buildOptionWidget(
                      option, highlight && shouldHighlight);
                },
              ),
            ),
          ],
        );
      }),
    );
  }

  void _onCreateNewLabel() async {
    final label = await widget.onCreateNewLabel!(_textEditingController.text);
    if (label?.id != null) {
      widget.onSubmit(
        returnValue: SetIdQueryParameter(id: label!.id!),
      );
    }
  }

  ///
  /// Filters the options passed to this widget by the current [query] and
  /// adds not-/any assigned options
  ///
  Iterable<IdQueryParameter> _filterOptionsByQuery(String query) sync* {
    final normalizedQuery = query.trim().toLowerCase();
    if (normalizedQuery.isEmpty) {
      if ((widget.initialValue.isUnset)) {
        if (widget.options.isEmpty) {
          yield const UnsetIdQueryParameter();
          return;
        }
        // If nothing is selected yet (==> UnsetIdQueryParameter), show all options first.
        for (final option in widget.options.values) {
          yield SetIdQueryParameter(id: option.id!);
        }
        if (widget.showNotAssignedOption) {
          yield const NotAssignedIdQueryParameter();
        }
        if (widget.showAnyAssignedOption) {
          yield const AnyAssignedIdQueryParameter();
        }
      } else {
        // If an initial value is given, show not assigned first, which will be selected by default when pressing "done" on keyboard.
        if (widget.showNotAssignedOption) {
          yield const NotAssignedIdQueryParameter();
        }
        if (widget.showAnyAssignedOption) {
          yield const AnyAssignedIdQueryParameter();
        }
        for (final option in widget.options.values) {
          // Don't include the initial value in the selection
          final initialValue = widget.initialValue;
          if (initialValue is SetIdQueryParameter &&
              option.id == initialValue.id) {
            continue;
          }
          yield SetIdQueryParameter(id: option.id!);
        }
      }
    } else {
      // Show filtered options, if no matching option is found, always show not assigned and any assigned (if enabled) and proceed.
      final matches = widget.options.values
          .where((e) => e.name.trim().toLowerCase().contains(normalizedQuery));
      if (matches.isNotEmpty) {
        for (final match in matches) {
          yield SetIdQueryParameter(id: match.id!);
        }
        if (widget.showNotAssignedOption) {
          yield const NotAssignedIdQueryParameter();
        }
        if (widget.showAnyAssignedOption) {
          yield const AnyAssignedIdQueryParameter();
        }
      } else {
        if (widget.showNotAssignedOption) {
          yield const NotAssignedIdQueryParameter();
        }
        if (widget.showAnyAssignedOption) {
          yield const AnyAssignedIdQueryParameter();
        }
        if (!(widget.showAnyAssignedOption || widget.showNotAssignedOption)) {
          yield const UnsetIdQueryParameter();
        }
      }
    }
  }

  String? _buildHintText() {
    return switch (widget.initialValue) {
      UnsetIdQueryParameter() => S.of(context)!.startTyping,
      NotAssignedIdQueryParameter() => S.of(context)!.notAssigned,
      AnyAssignedIdQueryParameter() => S.of(context)!.anyAssigned,
      SetIdQueryParameter(id: var id) =>
        widget.options[id]?.name ?? S.of(context)!.startTyping,
    };
  }

  Widget _buildOptionWidget(IdQueryParameter option, bool highlight) {
    void onTap() => widget.onSubmit(returnValue: option);
    final hasNoAssignedDocumentsTextStyle = Theme.of(context)
        .textTheme
        .labelMedium
        ?.apply(color: Theme.of(context).disabledColor);
    final hasAssignedDocumentsTextStyle =
        Theme.of(context).textTheme.labelMedium;

    return switch (option) {
      NotAssignedIdQueryParameter() => ListTile(
          selected: highlight,
          selectedTileColor: Theme.of(context).focusColor,
          title: Text(S.of(context)!.notAssigned),
          onTap: onTap,
        ),
      AnyAssignedIdQueryParameter() => ListTile(
          selected: highlight,
          selectedTileColor: Theme.of(context).focusColor,
          title: Text(S.of(context)!.anyAssigned),
          onTap: onTap,
        ),
      SetIdQueryParameter(id: var id) => ListTile(
          selected: highlight,
          selectedTileColor: Theme.of(context).focusColor,
          title: Text(
            widget.options[id]!.name,
            maxLines: 2,
            overflow: TextOverflow.ellipsis,
          ),
          onTap: onTap,
          trailing: Text(
            S
                .of(context)!
                .documentsAssigned(widget.options[id]!.documentCount ?? 0),
            style: (widget.options[id]!.documentCount ?? 0) > 0
                ? hasAssignedDocumentsTextStyle
                : hasNoAssignedDocumentsTextStyle,
          ),
        ),
      UnsetIdQueryParameter() => Center(
          child: Column(
            children: [
              Text(S.of(context)!.noItemsFound).padded(),
              if (widget.onCreateNewLabel != null)
                TextButton(
                  child: Text(widget.addNewLabelText!),
                  onPressed: _onCreateNewLabel,
                ),
            ],
          ),
        ),
    };
  }
}