import 'dart:convert';
import 'dart:io';
import 'dart:math';

import 'package:dio/dio.dart' as dio_lib;

var dio = dio_lib.Dio();

// Load mastodon instance url from env
final instanceUrl = Platform.environment['INSTANCE_URL'];
// Load mastodon auth token from env
final authToken = Platform.environment['MASTODON_TOKEN'];

Future<void> _postOnMastodon(postText) async {
  await dio.post('$instanceUrl/api/v1/statuses',
        data: {'status': postText},
        options:
            dio_lib.Options(headers: {'Authorization': 'Bearer $authToken'}));
}

/// Reads a file [fileUri] and adds posts to posts.json
/// 
/// If [fileUri] does not exist, do nothing.
/// [fileUri] is a plain text file where the posts are separated by empty lines.
/// posts.json is an array of posts
Future<void> _importPosts(fileUri) async {
  if (!File(fileUri).existsSync()) {
    return;
  }

  final file = File(fileUri);
  final lines = await file.readAsLines();

  final List<String> posts = [];
  String post = '';

  for (final line in lines) {
    if (line.isEmpty && post != '') {
      posts.add(post);
      print('Added post: $post');
      post = '';
    } else {
      post += '$line\n';
    }
  }

  if (post != '') {
    posts.add(post);
    print('Added post: $post');
  }

  // Read posts.json and add posts to it
  final postsJson = json.decode(await File('/data/posts.json').readAsString());
  postsJson.addAll(posts);

  // Write posts.json
  await File('/data/posts.json').writeAsString(json.encode(postsJson));

  // Delete file
  await file.delete();

  return;

}

/// Posts a random string from posts.json to mastodon
/// 
/// If posts.json does not exist, do nothing.
/// posts.json is an array of posts
/// If an array is empty, do nothing.
/// Delete posted post from posts.json
Future<void> _postRandomPost() async {
  if (!File('/data/posts.json').existsSync()) {
    return;
  }

  final postsJson = json.decode(await File('/data/posts.json').readAsString());

  if (postsJson.isEmpty) {
    return;
  }

  final post = postsJson.removeAt(Random().nextInt(postsJson.length));

  await File('/data/posts.json').writeAsString(json.encode(postsJson));

  await _postOnMastodon(post);

  return;
}

void main(List<String> args) async {
  // If posts.json does not exist, create it and write an empty array
  if (!File('/data/posts.json').existsSync()) {
    await File('/data/posts.json').writeAsString(json.encode([]));
  }

  // Import posts from files
  await _importPosts('/data/posts.txt');

  // Post a random post
  await _postRandomPost();

  // Post a random post at random time
  // Random time is between 1 and 8 hours
  // Random time is choosen after every post
  while (true) {
    await Future.delayed(Duration(hours: Random().nextInt(8) + 1));
    await _importPosts('/data/posts.txt');
    await _postRandomPost();
  }
  
}