providers: add process management

lib/config/dependencies.dart

@@ -1,6 +1,7 @@
 import 'package:get_it/get_it.dart';
 import 'package:sidesail/config/sidechains.dart';
 import 'package:sidesail/providers/balance_provider.dart';
+import 'package:sidesail/providers/proc_provider.dart';
 import 'package:sidesail/providers/transactions_provider.dart';
 import 'package:sidesail/routing/router.dart';
 import 'package:sidesail/rpc/rpc_ethereum.dart';
@@ -34,6 +35,9 @@ Future<void> initGetitDependencies(Sidechain initialChain) async {
     // we start polling for balance updates
     () => BalanceProvider(),
   );
+
+  GetIt.I.registerLazySingleton(() => ProcessProvider());
+
   GetIt.I.registerLazySingleton<TransactionsProvider>(
     () => TransactionsProvider(),
   );

lib/providers/proc_provider.dart

@@ -0,0 +1,94 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:logger/logger.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:sidesail/logger.dart';
+
+class ProcessProvider extends ChangeNotifier {
+  ProcessProvider();
+
+  // List of currently running processes.
+  List<int> pids = [];
+
+  final Map<int, int> _exitCodes = {};
+  final List<int> _runningProcesses = [];
+
+  final Map<int, Stream<String>> _stdoutStreams = {};
+  final Map<int, Stream<String>> _stderrStreams = {};
+
+  Stream<String> stdout(int pid) => _stdoutStreams[pid] ?? const Stream.empty();
+  Stream<String> stderr(int pid) => _stderrStreams[pid] ?? const Stream.empty();
+  bool running(int pid) => _runningProcesses.contains(pid);
+
+  // Starts a binary located in the asset bundle included with the app.
+  Future<int> start(BuildContext context, String binary, List<String> args) async {
+    // TODO: lookup based on arch + platform
+    final binResource = await DefaultAssetBundle.of(context).load('assets/bin/$binary');
+
+    final temp = await getTemporaryDirectory();
+
+    final file = File('${temp.path}/$binary');
+
+    // Have to convert the ByteData -> List<int>. Side note: why tf does writeAsBytes
+    // operate on a list of numbers? Jesus
+    // https://stackoverflow.com/a/50121777
+    final buffer = binResource.buffer;
+    await file.writeAsBytes(
+      buffer.asUint8List(binResource.offsetInBytes, binResource.lengthInBytes),
+    );
+
+    // Must be executable before we can start.
+    // TODO: what to do on Windows here
+    await Process.run('chmod', ['+x', file.path]);
+
+    final process = await Process.start(
+      file.path,
+      args,
+      mode: ProcessStartMode.normal, // when the flutter app quits, this process quit
+    );
+    log.d('started "$binary" with pid ${process.pid}');
+    _runningProcesses.add(process.pid);
+
+    // Let output streaming chug in the background
+
+    // Proper logs are written here
+    _stdoutStreams[process.pid] = process.stdout.transform(utf8.decoder);
+
+    // Error messages while starting up are written here
+    _stderrStreams[process.pid] = process.stderr.transform(utf8.decoder);
+
+    // Register a handler for when the process stops.
+    unawaited(
+      process.exitCode.then((code) async {
+        var level = Level.error;
+        // Node software exited with a success code. Someone called
+        // `drivechain-cli stop`?
+        if (code == 0) {
+          level = Level.info;
+        }
+
+        final errLogs = await (_stderrStreams[process.pid] ?? const Stream.empty()).toList();
+        log.log(level, '"$binary" exited with code $code: $errLogs');
+
+        // Forward to listeners that the process finished.
+        _exitCodes[process.pid] = code;
+        _runningProcesses.remove(process.pid);
+        notifyListeners();
+      }),
+    );
+
+    notifyListeners();
+    return process.pid;
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+
+    log.d('dispose process provider: killing processes $_runningProcesses');
+    _runningProcesses.forEach(Process.killPid);
+  }
+}

pubspec.lock

@@ -586,7 +586,7 @@ packages:
     source: hosted
     version: "1.0.1"
   path_provider:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: path_provider
       sha256: a1aa8aaa2542a6bc57e381f132af822420216c80d4781f7aa085ca3229208aaa

pubspec.yaml

@@ -51,15 +51,15 @@ dependencies:
   collection: ^1.17.2
   stacked: ^3.4.1+1
   intl: ^0.18.0
-  web3dart: 
+  web3dart:
     git:
       url: https://github.com/xclud/web3dart.git
       ref: main
   http: ^1.1.0
-    
+  path_provider: ^2.1.1
 
 # Needed for silencing complaints from adding the web3dart lib
-dependency_overrides: 
+dependency_overrides:
   stream_channel: 2.1.2
 
 dev_dependencies:
@@ -85,6 +85,9 @@ flutter:
   # the material Icons class.
   uses-material-design: true
 
+  assets:
+    - assets/bin/
+
   fonts:
     - family: SourceCodePro
       fonts: