import 'package:super_paging/super_paging.dart';

class RickAndMortySource extends PagingSource<int, Character> {
  final RickAndMortyApi api;

  RickAndMortySource({required this.api});

  @override
  Future<LoadResult<int, Character>> load(PagingConfig<int> config, int key) async {
    try {
      final characters = await api.getCharacters(page: key);
      return LoadResult.page(nextKey: key + 1, items: characters);
    } catch (e) {
      return LoadResult.error(e);
    }
  }
}

final pager = Pager(
  initialKey: 1,
  config: const PagingConfig(pageSize: 20, initialLoadSize: 60),
  pagingSourceFactory: () => RickAndMortySource(api: RickAndMortyApi()),
);

PagingListView(
  pager: pager,
  itemBuilder: (BuildContext context, int index) {
    final item = pager.items.elementAt(index);
    return ListTile(
      title: Text(item.name),
      subtitle: Text(item.species),
      trailing: Text('# ${item.id}'),
      leading: CircleAvatar(backgroundImage: NetworkImage(item.image)),
    );
  },
  emptyBuilder: (BuildContext context) {
    return const Center(
      child: Text('No characters found'),
    );
  },
  errorBuilder: (BuildContext context, Object? error) {
    return Center(child: Text('$error'));
  },
  loadingBuilder: (BuildContext context) {
    return const Center(
      child: CircularProgressIndicator.adaptive(),
    );
  },
);

// Refresh the data
await pager.refresh();

// Retry failed loads
await pager.retry();

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

Pager(
  // Defines the initial key to use for the first load.
  //
  // By default, the initial key is null.
  initialKey: null,

  // Configuration for pagination behavior.
  config: PagingConfig(
    // Defines the number of items to load in a single page.
    pageSize: 20,
    
    // Defines the number of items to load in the first page.
    //
    // By default, the initial load size is 3 times the page size.
    initialLoadSize: 60,
    
    // Defines how far from the edge of loaded content an access
    // must be to trigger further loading.
    //
    // By default, the pager will start loading when the user scrolls
    // within 3 items of the end of the loaded content.
    //
    // If set to null, the pager will not start loading more content until
    // they are specifically requested by the user.
    prefetchIndex: 3,
    
    // @Experimental
    //
    // Defines the maximum number of items to keep in memory before
    // pages should be dropped.
    //
    // If set to null (Default), pages will never be dropped.
    maxSize: null,
  ),
  
  // Defines the initial state to use for the first load.
  //
  // By default, [PagingState.initial()] state is used.
  initialState: PagingState.initial(),

  // Defines the source from which to load the paginated data.
  pagingSourceFactory: () => MyPagingSource(),
);

PagingListView<int, String>(
  // Defines the pager to use for loading data.
  pager: myPager,

  // Defines the builder that is called to build items in the ListView.
  //
  // The builder is called once for each item in the list.
  itemBuilder: (context, index) {
    final item = myPager.valueList.elementAt(index);
    return ListTile(
      title: Text(item),
    );
  },

  // Defines the builder that is called to build the empty state of the list.
  emptyBuilder: (context) {
    return const Center(
      child: Text('No items found'),
    );
  },

  // Defines the builder that is called to build the error state of the list.
  //
  // [error] is the error that caused the state to be built.
  errorBuilder: (context, error) {
    return Center(child: Text('Error: $error'));
  },

  // Defines the builder that is called to build the loading state of the list.
  loadingBuilder: (context) {
    return const Center(
      child: CircularProgressIndicator.adaptive(),
    );
  },

  // Defines the builder that is called to build the prepend state of the list.
  //
  // [state] is the current state of the pager and [pager] is the pager instance.
  //
  // Optional. If not provided, the list will show the default prepend loading state.
  prependStateBuilder: (context, state, pager) {
    // Return a widget based on the state. For example, a button to load the previous page.
    // Use the [pager] instance to call [pager.load()] or [pager.retry] based on the state.
  },

  // Defines the builder that is called to build the append state of the list.
  //
  // [state] is the current state of the pager and [pager] is the pager instance.
  //
  // Optional. If not provided, the list will show the default append loading state.
  appendStateBuilder: (context, state, pager) {
    // Return a widget based on the state. For example, a button to load the next page.
    // Use the [pager] instance to call [pager.load()] or [pager.retry] based on the state.
  },
);