// SPDX-FileCopyrightText: 2022 Iconica
//
// SPDX-License-Identifier: BSD-3-Clause

import 'dart:collection';
import 'package:flutter/material.dart';
import 'package:flutter_registration/flutter_registration.dart';

class AuthScreen extends StatefulWidget {
  const AuthScreen({
    required this.title,
    required this.steps,
    required this.submitBtnTitle,
    required this.nextBtnTitle,
    required this.previousBtnTitle,
    required this.onFinish,
    this.customAppBar,
    this.nextButtonBuilder,
    this.previousButtonBuilder,
    super.key,
  }) : assert(steps.length > 0, 'At least one step is required');

  final String title;
  final Function({
    required HashMap<String, String> values,
    required VoidCallback onError,
  }) onFinish;
  final List<AuthStep> steps;
  final String submitBtnTitle;
  final String nextBtnTitle;
  final String previousBtnTitle;
  final AppBar? customAppBar;
  final Widget Function(VoidCallback onPressed, String label)?
      nextButtonBuilder;
  final Widget Function(VoidCallback onPressed, String label)?
      previousButtonBuilder;

  @override
  State<AuthScreen> createState() => _AuthScreenState();
}

class _AuthScreenState extends State<AuthScreen> {
  final _formKey = GlobalKey<FormState>();
  final _pageController = PageController();
  final _animationDuration = const Duration(milliseconds: 300);
  final _animationCurve = Curves.ease;

  AppBar get _appBar =>
      widget.customAppBar ??
      AppBar(
        title: Text(widget.title),
      );

  void onPrevious() {
    _pageController.previousPage(
      duration: _animationDuration,
      curve: _animationCurve,
    );
  }

  void onNext(AuthStep step) {
    if (!_formKey.currentState!.validate()) {
      return;
    }

    _formKey.currentState!.save();

    FocusScope.of(context).unfocus();

    if (widget.steps.last == step) {
      var values = HashMap<String, String>();

      for (var step in widget.steps) {
        for (var field in step.fields) {
          values[field.name] =
              (field as AuthTextField).textController.value.text;
        }
      }

      widget.onFinish(
        values: values,
        onError: () => _pageController.animateToPage(
          0,
          duration: _animationDuration,
          curve: _animationCurve,
        ),
      );

      return;
    } else {
      _pageController.nextPage(
        duration: _animationDuration,
        curve: _animationCurve,
      );
    }
  }

  @override
  Widget build(BuildContext context) => Scaffold(
        backgroundColor: Theme.of(context).colorScheme.background,
        appBar: _appBar,
        body: Form(
          key: _formKey,
          child: PageView(
            physics: const NeverScrollableScrollPhysics(),
            controller: _pageController,
            children: <Widget>[
              for (AuthStep step in widget.steps)
                Column(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    Flexible(
                      child: Center(
                        child: ListView(
                          physics: const ClampingScrollPhysics(),
                          shrinkWrap: true,
                          padding: const EdgeInsets.symmetric(
                            vertical: 8.0,
                            horizontal: 30.0,
                          ),
                          children: [
                            for (AuthField field in step.fields)
                              Align(
                                child: Column(
                                  crossAxisAlignment: CrossAxisAlignment.start,
                                  children: [
                                    if (field.title != null) ...[
                                      field.title!,
                                    ],
                                    field.build(),
                                  ],
                                ),
                              )
                          ],
                        ),
                      ),
                    ),
                    Padding(
                      padding: const EdgeInsets.only(
                        top: 15.0,
                        bottom: 30.0,
                        left: 30.0,
                        right: 30.0,
                      ),
                      child: Row(
                        mainAxisAlignment: widget.steps.first != step
                            ? MainAxisAlignment.spaceBetween
                            : MainAxisAlignment.end,
                        children: [
                          if (widget.steps.first != step)
                            widget.previousButtonBuilder?.call(
                                  onPrevious,
                                  widget.previousBtnTitle,
                                ) ??
                                ElevatedButton(
                                  onPressed: onPrevious,
                                  child: Row(
                                    children: [
                                      const Icon(
                                        Icons.arrow_back,
                                        size: 18,
                                      ),
                                      Padding(
                                        padding:
                                            const EdgeInsets.only(left: 4.0),
                                        child: Text(widget.previousBtnTitle),
                                      ),
                                    ],
                                  ),
                                ),
                          widget.nextButtonBuilder?.call(
                                () => onNext(step),
                                widget.steps.last == step
                                    ? widget.submitBtnTitle
                                    : widget.nextBtnTitle,
                              ) ??
                              ElevatedButton(
                                onPressed: () {
                                  onNext(step);
                                },
                                child: Row(
                                  children: [
                                    Text(
                                      widget.steps.last == step
                                          ? widget.submitBtnTitle
                                          : widget.nextBtnTitle,
                                    ),
                                    const Padding(
                                      padding: EdgeInsets.only(left: 4.0),
                                      child: Icon(
                                        Icons.arrow_forward,
                                        size: 18,
                                      ),
                                    ),
                                  ],
                                ),
                              ),
                        ],
                      ),
                    )
                  ],
                ),
            ],
          ),
        ),
      );
}