import 'dart:math' as math;
import 'package:flutter/widgets.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/gestures.dart' show DragStartBehavior;
import 'button_bar.dart';
import 'card.dart';
import 'constants.dart';
import 'data_table.dart';
import 'data_table_source.dart';
import 'debug.dart';
import 'dropdown.dart';
import 'icon_button.dart';
import 'icons.dart';
import 'ink_decoration.dart';
import 'material_localizations.dart';
import 'progress_indicator.dart';
import 'theme.dart';


class PaginatedDataTable extends StatefulWidget {

  PaginatedDataTable({
    Key key,
    this.header,
    this.actions,
    @required this.columns,
    this.sortColumnIndex,
    this.sortAscending = true,
    this.onSelectAll,
    this.dataRowHeight = kMinInteractiveDimension,
    this.headingRowHeight = 56.0,
    this.horizontalMargin = 24.0,
    this.columnSpacing = 56.0,
    this.initialFirstRowIndex = 0,
    this.onPageChanged,
    this.rowsPerPage = defaultRowsPerPage,
    this.availableRowsPerPage = const <int>[defaultRowsPerPage, defaultRowsPerPage * 2, defaultRowsPerPage * 5, defaultRowsPerPage * 10],
    this.onRowsPerPageChanged,
    this.dragStartBehavior = DragStartBehavior.start,
    @required this.source,
  }) : assert(header == null),
       assert(columns != null),
       assert(dragStartBehavior != null),
       assert(columns.isNotEmpty),
       assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length)),
       assert(sortAscending != null),
       assert(dataRowHeight != null),
       assert(headingRowHeight != null),
       assert(horizontalMargin != null),
       assert(columnSpacing != null),
       assert(rowsPerPage != null),
       assert(rowsPerPage > 0),
       assert(() {
         if (onRowsPerPageChanged != null)
           assert(availableRowsPerPage != null && availableRowsPerPage.contains(rowsPerPage));
         return true;
       }()),
       assert(source != null),
       super(key: key);


  final Widget header; 
  final List<Widget> actions;
  final List<DataColumn> columns;
  final int sortColumnIndex;
  final bool sortAscending;
  final ValueSetter<bool> onSelectAll;
  final double dataRowHeight;
  final double headingRowHeight;
  final double horizontalMargin;
  final double columnSpacing;
  final int initialFirstRowIndex;
  final ValueChanged<int> onPageChanged;
  final int rowsPerPage;

  static const int defaultRowsPerPage = 10;
  final List<int> availableRowsPerPage;
  final ValueChanged<int> onRowsPerPageChanged;
  final DataTableSource source;
  final DragStartBehavior dragStartBehavior;
  @override
  PaginatedDataTableState createState() => PaginatedDataTableState();
}

class PaginatedDataTableState extends State<PaginatedDataTable> {
  int _firstRowIndex;
  int _rowCount;
  bool _rowCountApproximate;
  int _selectedRowCount;
  final Map<int, DataRow> _rows = <int, DataRow>{};

  @override
  void initState() {
    super.initState();
    _firstRowIndex = PageStorage.of(context)?.readState(context) ?? widget.initialFirstRowIndex ?? 0;
    widget.source.addListener(_handleDataSourceChanged);
    _handleDataSourceChanged();
  }

  @override
  void didUpdateWidget(PaginatedDataTable oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.source != widget.source) {
      oldWidget.source.removeListener(_handleDataSourceChanged);
      widget.source.addListener(_handleDataSourceChanged);
      _handleDataSourceChanged();
    }
  }

  @override
  void dispose() {
    widget.source.removeListener(_handleDataSourceChanged);
    super.dispose();
  }

  void _handleDataSourceChanged() {
    setState(() {
      _rowCount = widget.source.rowCount;
      _rowCountApproximate = widget.source.isRowCountApproximate;
      _selectedRowCount = widget.source.selectedRowCount;
      _rows.clear();
    });
  }

  /// Ensures that the given row is visible.
  void pageTo(int rowIndex) {
    final int oldFirstRowIndex = _firstRowIndex;
    setState(() {
      final int rowsPerPage = widget.rowsPerPage;
      _firstRowIndex = (rowIndex ~/ rowsPerPage) * rowsPerPage;
    });
    if ((widget.onPageChanged != null) &&
        (oldFirstRowIndex != _firstRowIndex))
      widget.onPageChanged(_firstRowIndex);
  }

  DataRow _getBlankRowFor(int index) {
    return DataRow.byIndex(
      index: index,
      cells: widget.columns.map<DataCell>((DataColumn column) => DataCell.empty).toList(),
    );
  }

  DataRow _getProgressIndicatorRowFor(int index) {
    bool haveProgressIndicator = false;
    final List<DataCell> cells = widget.columns.map<DataCell>((DataColumn column) {
      if (!column.numeric) {
        haveProgressIndicator = true;
        return const DataCell(CircularProgressIndicator());
      }
      return DataCell.empty;
    }).toList();
    if (!haveProgressIndicator) {
      haveProgressIndicator = true;
      cells[0] = const DataCell(CircularProgressIndicator());
    }
    return DataRow.byIndex(
      index: index,
      cells: cells,
    );
  }

  List<DataRow> _getRows(int firstRowIndex, int rowsPerPage) {
    final List<DataRow> result = <DataRow>[];
    final int nextPageFirstRowIndex = firstRowIndex + rowsPerPage;
    bool haveProgressIndicator = false;
    for (int index = firstRowIndex; index < nextPageFirstRowIndex; index += 1) {
      DataRow row;
      if (index < _rowCount || _rowCountApproximate) {
        row = _rows.putIfAbsent(index, () => widget.source.getRow(index));
        if (row == null && !haveProgressIndicator) {
          row ??= _getProgressIndicatorRowFor(index);
          haveProgressIndicator = true;
        }
      }
      row ??= _getBlankRowFor(index);
      result.add(row);
    }
    return result;
  }

  void _handlePrevious() {
    pageTo(math.max(_firstRowIndex - widget.rowsPerPage, 0));
  }

  void _handleNext() {
    pageTo(_firstRowIndex + widget.rowsPerPage);
  }

  final GlobalKey _tableKey = GlobalKey();

  @override
  Widget build(BuildContext context) {
  
    assert(debugCheckHasMaterialLocalizations(context));
    final ThemeData themeData = Theme.of(context);
    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
    // HEADER
    final List<Widget> headerWidgets = <Widget>[];
    double startPadding = 24.0;
    if (_selectedRowCount == 0) {
      // headerWidgets.add(Expanded(child: widget.header));
      if (widget.header is ButtonBar) {
    
        startPadding = 12.0;
      }
    } else {
      headerWidgets.add(Expanded(
        child: Text(localizations.selectedRowCountTitle(_selectedRowCount)),
      ));
    }
    if (widget.actions != null) {
      headerWidgets.addAll(
        widget.actions.map<Widget>((Widget action) {
          return Padding(
            // 8.0 is the default padding of an icon button
            padding: const EdgeInsetsDirectional.only(start: 24.0 - 8.0 * 2.0),
            child: action,
          );
        }).toList()
      );
    }

    // FOOTER
    final TextStyle footerTextStyle = themeData.textTheme.caption;
    final List<Widget> footerWidgets = <Widget>[];
    if (widget.onRowsPerPageChanged != null) {
      final List<Widget> availableRowsPerPage = widget.availableRowsPerPage
        .where((int value) => value <= _rowCount || value == widget.rowsPerPage)
        .map<DropdownMenuItem<int>>((int value) {
          return DropdownMenuItem<int>(
            value: value,
            child: Text('$value'),
          );
        })
        .toList();
      footerWidgets.addAll(<Widget>[
        Container(width: 14.0), // to match trailing padding in case we overflow and end up scrolling
        Text(localizations.rowsPerPageTitle),
        ConstrainedBox(
          constraints: const BoxConstraints(minWidth: 64.0), // 40.0 for the text, 24.0 for the icon
          child: Align(
            alignment: AlignmentDirectional.centerEnd,
            child: DropdownButtonHideUnderline(
              child: DropdownButton<int>(
                items: availableRowsPerPage,
                value: widget.rowsPerPage,
                onChanged: widget.onRowsPerPageChanged,
                style: footerTextStyle,
                iconSize: 24.0,
              ),
            ),
          ),
        ),
      ]);
    }
    footerWidgets.addAll(<Widget>[
      Container(width: 32.0),
      Text(
        localizations.pageRowsInfoTitle(
          _firstRowIndex + 1,
          _firstRowIndex + widget.rowsPerPage,
          _rowCount,
          _rowCountApproximate,
        ),
      ),
      Container(width: 32.0),
      IconButton(
        icon: const Icon(Icons.chevron_left),
        padding: EdgeInsets.zero,
        tooltip: localizations.previousPageTooltip,
        onPressed: _firstRowIndex <= 0 ? null : _handlePrevious,
      ),
      Container(width: 24.0),
      IconButton(
        icon: const Icon(Icons.chevron_right),
        padding: EdgeInsets.zero,
        tooltip: localizations.nextPageTooltip,
        onPressed: (!_rowCountApproximate && (_firstRowIndex + widget.rowsPerPage >= _rowCount)) ? null : _handleNext,
      ),
      Container(width: 14.0),
    ]);

    // CARD
    return Card(
      semanticContainer: false,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          Semantics(
            container: true,
            child: DefaultTextStyle(
            
              style: _selectedRowCount > 0 ? themeData.textTheme.subhead.copyWith(color: themeData.accentColor)
                                           : themeData.textTheme.title.copyWith(fontWeight: FontWeight.w400),
              child: IconTheme.merge(
                data: const IconThemeData(
                  opacity: 0.54
                ),
                child: Ink(
                  height: 0.0,
                  color: _selectedRowCount > 0 ? themeData.secondaryHeaderColor : null,
                  child: Padding(
                    padding: EdgeInsetsDirectional.only(start: startPadding, end: 0.0),
                    child: Row(
                      mainAxisAlignment: MainAxisAlignment.end,
                      children: headerWidgets,
                    ),
                  ),
                ),
              ),
            ),
          ),
          SingleChildScrollView(
            scrollDirection: Axis.horizontal,
            dragStartBehavior: widget.dragStartBehavior,
            child: DataTable(
              key: _tableKey,
              columns: widget.columns,
              sortColumnIndex: widget.sortColumnIndex,
              sortAscending: widget.sortAscending,
              onSelectAll: widget.onSelectAll,
              dataRowHeight: widget.dataRowHeight,
              headingRowHeight: widget.headingRowHeight,
              horizontalMargin: widget.horizontalMargin,
              columnSpacing: widget.columnSpacing,
              rows: _getRows(_firstRowIndex, widget.rowsPerPage),
            ),
          ),
          DefaultTextStyle(
            style: footerTextStyle,
            child: IconTheme.merge(
              data: const IconThemeData(
                opacity: 0.54
              ),
              child: Container(
                height: 56.0,
                child: SingleChildScrollView(
                  dragStartBehavior: widget.dragStartBehavior,
                  scrollDirection: Axis.horizontal,
                  reverse: true,
                  child: Row(
                    children: footerWidgets,
                  ),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}