anyway/frontend/lib/modules/current_trip_loading_indicator.dart

import 'package:anyway/constants.dart';
import 'package:flutter/material.dart';
import 'package:auto_size_text/auto_size_text.dart';

import 'package:anyway/structs/trip.dart';
import 'package:anyway/pages/current_trip.dart';


final List<String> statusTexts = [
  'Parsing your preferences...',
  'Finding the best places...',
  'Crunching the numbers...',
  'Calculating the best route...',
  'Making sure you have a great time...',
];


class CurrentTripLoadingIndicator extends StatefulWidget {
  final Trip trip;
  const CurrentTripLoadingIndicator({
    super.key,
    required this.trip,
  });

  @override
  State<CurrentTripLoadingIndicator> createState() => _CurrentTripLoadingIndicatorState();
}


class _CurrentTripLoadingIndicatorState extends State<CurrentTripLoadingIndicator> {
  @override
  Widget build(BuildContext context) => Stack(
    fit: StackFit.expand,
    children: [
      // In the very center of the panel, show the greeter which tells the user that the trip is being generated
      Center(child: loadingText(widget.trip)),
      // As a gimmick, and a way to show that the app is still working, show a few loading dots
      Align(
        alignment: Alignment.bottomCenter,
        child: statusText(),
      )
    ],
  );
}

// automatically cycle through the greeter texts
class statusText extends StatefulWidget {
  const statusText({Key? key}) : super(key: key);

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

class _statusTextState extends State<statusText> {
  int statusIndex = 0;

  @override
  void initState() {
    super.initState();
    Future.delayed(Duration(seconds: 5), () {
      setState(() {
        statusIndex = (statusIndex + 1) % statusTexts.length;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return AutoSizeText(
      statusTexts[statusIndex],
      style: Theme.of(context).textTheme.labelSmall,
    );
  }
}



Widget loadingText(Trip trip) => FutureBuilder(
  future: trip.cityName,
  builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
    Widget greeter;

    if (snapshot.hasData) {
      greeter = AnimatedGradientText(
        text: 'Creating your trip to ${snapshot.data}...',
        style: greeterStyle,
      );
    } else if (snapshot.hasError) {
      // the exact error is shown in the central part of the trip overview. No need to show it here
      greeter = AnimatedGradientText(
        text: 'Error while loading trip.',
        style: greeterStyle,
      );
    } else {
      greeter = AnimatedGradientText(
        text: 'Creating your trip...',
        style: greeterStyle,
      );
    }
    return greeter;
  }
);

class AnimatedGradientText extends StatefulWidget {
  final String text;
  final TextStyle style;

  const AnimatedGradientText({
    Key? key,
    required this.text,
    required this.style,
  }) : super(key: key);

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

class _AnimatedGradientTextState extends State<AnimatedGradientText> with SingleTickerProviderStateMixin {
  late AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 1),
      vsync: this,
    )..repeat();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: _controller,
      builder: (context, child) {
        return ShaderMask(
          shaderCallback: (bounds) {
            return LinearGradient(
              colors: [GRADIENT_START, GRADIENT_END, GRADIENT_START],
              stops: [
                _controller.value - 1.0,
                _controller.value,
                _controller.value + 1.0,
              ],
              tileMode: TileMode.mirror,
            ).createShader(bounds);
          },
          child: Text(
            widget.text,
            style: widget.style,
          ),
        );
      },
    );
  }
}