import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:intl/intl.dart';

/// A [FormField] that contains a [DateField].
///
/// This is a convenience widget that wraps a [DateField] widget in a
/// [FormField].
///
/// A [Form] ancestor is not required. The [Form] simply makes it easier to
/// save, reset, or validate multiple fields at once. To use without a [Form],
/// pass a [GlobalKey] to the constructor and use [GlobalKey.currentState] to
/// save or reset the form field.
class DateFormField extends FormField<DateTime> {
  DateFormField(
      {Key key,
      FormFieldSetter<DateTime> onSaved,
      FormFieldValidator<DateTime> validator,
      DateTime initialValue,
      bool autovalidate = false,
      bool enabled = true,
      this.onDateSelected,
      this.firstDate,
      this.lastDate,
      this.label = 'Select date',
      this.dateFormat,
      this.decoration,
      this.initialDatePickerMode = DatePickerMode.day})
      : super(
          key: key,
          initialValue: initialValue,
          onSaved: onSaved,
          validator: validator,
          autovalidate: autovalidate,
          enabled: enabled,
          builder: (FormFieldState<DateTime> field) {
            final _DateFormFieldState state = field;

            void onChangedHandler(DateTime value) {
              if (onDateSelected != null) {
                onDateSelected(value);
              }
              field.didChange(value);
            }

            return DateField(
              label: label,
              firstDate: firstDate,
              lastDate: lastDate,
              decoration: decoration,
              initialDatePickerMode: initialDatePickerMode,
              dateFormat: dateFormat,
              errorText: state.errorText,
              onDateSelected: onChangedHandler,
              selectedDate: state.value,
              enabled: enabled,
            );
          },
        );

  /// (optional) A callback that will be triggered whenever a new
  /// DateTime is selected
  final ValueChanged<DateTime> onDateSelected;

  /// (optional) The first date that the user can select (default is 1900)
  final DateTime firstDate;

  /// (optional) The last date that the user can select (default is 2100)
  final DateTime lastDate;

  /// (optional) The label to display for the field (default is 'Select date')
  final String label;

  /// (optional) Custom [InputDecoration] for the [InputDecorator] widget
  final InputDecoration decoration;

  /// (optional) How to display the [DateTime] for the user (default is [DateFormat.yMMMD])
  final DateFormat dateFormat;

  /// (optional) Let you choose the [DatePickerMode] for the date picker! (default is [DatePickerMode.day]
  final DatePickerMode initialDatePickerMode;

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

class _DateFormFieldState extends FormFieldState<DateTime> {}

/// [DateField]
///
/// Shows an [_InputDropdown] that'll trigger [DateField._selectDate] whenever the user
/// clicks on it ! The date picker is **platform responsive** (ios date picker style for ios, ...)
class DateField extends StatelessWidget {
  /// Default constructor
  const DateField({
    @required this.onDateSelected,
    @required this.selectedDate,
    this.firstDate,
    this.lastDate,
    this.initialDatePickerMode = DatePickerMode.day,
    this.decoration,
    this.errorText,
    this.dateFormat,
    this.label = 'Select date',
    this.enabled = true,
  });

  /// Callback for whenever the user selects a [DateTime]
  final ValueChanged<DateTime> onDateSelected;

  /// The current selected date to display inside the field
  final DateTime selectedDate;

  /// (optional) The first date that the user can select (default is 1900)
  final DateTime firstDate;

  /// (optional) The last date that the user can select (default is 2100)
  final DateTime lastDate;

  /// Let you choose the [DatePickerMode] for the date picker! (default is [DatePickerMode.day]
  final DatePickerMode initialDatePickerMode;

  /// The label to display for the field (default is 'Select date')
  final String label;

  /// (optional) The error text that should be displayed under the field
  final String errorText;

  /// (optional) Custom [InputDecoration] for the [InputDecorator] widget
  final InputDecoration decoration;

  /// (optional) How to display the [DateTime] for the user (default is [DateFormat.yMMMD])
  final DateFormat dateFormat;

  /// (optional) Whether the field is usable. If false the user won't be able to select any date
  final bool enabled;

  /// Shows a dialog asking the user to pick a date !
  Future<void> _selectDate(BuildContext context) async {
    if (Theme.of(context).platform == TargetPlatform.iOS) {
      showModalBottomSheet<void>(
        context: context,
        builder: (BuildContext builder) {
          return Container(
            height: MediaQuery.of(context).size.height / 4,
            child: CupertinoDatePicker(
              mode: CupertinoDatePickerMode.date,
              onDateTimeChanged: onDateSelected,
              initialDateTime: selectedDate ?? lastDate ?? DateTime.now(),
              minimumDate: firstDate,
              maximumDate: lastDate,
            ),
          );
        },
      );
    } else {
      final DateTime _selectedDate = await showDatePicker(
          context: context,
          initialDatePickerMode: initialDatePickerMode,
          initialDate: selectedDate ?? lastDate ?? DateTime.now(),
          firstDate: firstDate ?? DateTime(1900),
          lastDate: lastDate ?? DateTime(2100));

      if (_selectedDate != null) {
        onDateSelected(_selectedDate);
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    String text;

    if (selectedDate != null)
      text = (dateFormat ?? DateFormat.yMMMd()).format(selectedDate);

    return _InputDropdown(
      text: text ?? label,
      label: text == null ? null : label,
      errorText: errorText,
      decoration: decoration,
      onPressed: enabled
          ? () {
              _selectDate(context);
            }
          : null,
    );
  }
}

///
/// [_InputDropdown]
///
/// Shows a field with a dropdown arrow !
/// It does not show any popup menu, it'll just trigger onPressed whenever the
/// user does click on it !
class _InputDropdown extends StatelessWidget {
  const _InputDropdown({
    Key key,
    @required this.text,
    this.label,
    this.decoration,
    this.textStyle,
    this.onPressed,
    this.errorText,
  })  : assert(text != null),
        super(key: key);

  /// The label to display for the field (default is 'Select date')
  final String label;

  /// The text that should be displayed inside the field
  final String text;

  /// (optional) The error text that should be displayed under the field
  final String errorText;

  /// (optional) Custom [InputDecoration] for the [InputDecorator] widget
  final InputDecoration decoration;

  /// TextStyle for the field
  final TextStyle textStyle;

  /// Callbacks triggered whenever the user presses on the field!
  final VoidCallback onPressed;

  @override
  Widget build(BuildContext context) {
    BorderRadius inkwellBorderRadius;

    if (decoration?.border?.runtimeType == OutlineInputBorder) {
      inkwellBorderRadius = BorderRadius.circular(8);
    }

    final InputDecoration effectiveDecoration =
        decoration?.copyWith(errorText: errorText) ??
            InputDecoration(
              labelText: label,
              errorText: errorText,
              suffixIcon: Icon(Icons.arrow_drop_down),
            ).applyDefaults(Theme.of(context).inputDecorationTheme);

    return Material(
      color: Colors.transparent,
      child: InkWell(
        borderRadius: inkwellBorderRadius,
        onTap: onPressed,
        child: InputDecorator(
          decoration: effectiveDecoration,
          baseStyle: textStyle,
          child: Text(text, style: textStyle),
        ),
      ),
    );
  }
}