feat: handle completion request (#17)

lib/cli_completion.dart

@@ -4,3 +4,5 @@ library cli_completion;
 
 export 'src/command_runner/commands/commands.dart';
 export 'src/command_runner/completion_command_runner.dart';
+export 'src/handling/completion_result.dart';
+export 'src/handling/completion_state.dart';

lib/src/command_runner/commands/handle_completion_command.dart

@@ -2,7 +2,8 @@ import 'dart:async';
 
 import 'package:args/command_runner.dart';
 import 'package:cli_completion/src/command_runner/completion_command_runner.dart';
-
+import 'package:cli_completion/src/handling/completion_state.dart';
+import 'package:cli_completion/src/handling/parser.dart';
 import 'package:mason_logger/mason_logger.dart';
 
 /// {@template handle_completion_request_command}
@@ -34,12 +35,27 @@ class HandleCompletionRequestCommand<T> extends Command<T> {
   final Logger logger;
 
   @override
-  FutureOr<T>? run() {
-    logger
-      ..info('USA')
-      ..info('Brazil')
-      ..info('Netherlands');
+  CompletionCommandRunner<T> get runner {
+    return super.runner! as CompletionCommandRunner<T>;
+  }
 
+  @override
+  FutureOr<T>? run() {
+    try {
+      final completionState = CompletionState.fromEnvironment(
+        runner.environmentOverride,
+      );
+      if (completionState == null) {
+        return null;
+      }
+
+      final result = CompletionParser(completionState).parse();
+
+      runner.renderCompletionResult(result);
+    } on Exception {
+      // Do not output any Exception here, since even error messages are
+      // interpreted as completion suggestions
+    }
     return null;
   }
 }

lib/src/command_runner/completion_command_runner.dart

@@ -2,7 +2,7 @@ import 'dart:async';
 
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
-import 'package:cli_completion/src/command_runner/commands/commands.dart';
+import 'package:cli_completion/cli_completion.dart';
 import 'package:cli_completion/src/exceptions.dart';
 import 'package:cli_completion/src/install/completion_installation.dart';
 import 'package:cli_completion/src/system_shell.dart';
@@ -35,10 +35,11 @@ abstract class CompletionCommandRunner<T> extends CommandRunner<T> {
   final Logger completionInstallationLogger = Logger();
 
   /// Environment map which can be overridden for testing purposes.
-  @visibleForTesting
+  @internal
   Map<String, String>? environmentOverride;
 
-  SystemShell? get _systemShell =>
+  /// The [SystemShell] used to determine the current shell.
+  SystemShell? get systemShell =>
       SystemShell.current(environmentOverride: environmentOverride);
 
   CompletionInstallation? _completionInstallation;
@@ -48,7 +49,7 @@ abstract class CompletionCommandRunner<T> extends CommandRunner<T> {
     var completionInstallation = _completionInstallation;
 
     completionInstallation ??= CompletionInstallation.fromSystemShell(
-      systemShell: _systemShell,
+      systemShell: systemShell,
       logger: completionInstallationLogger,
     );
 
@@ -81,4 +82,19 @@ abstract class CompletionCommandRunner<T> extends CommandRunner<T> {
       completionInstallationLogger.err(e.toString());
     }
   }
+
+  /// Renders a [CompletionResult] into the current system shell.
+  ///
+  /// This is called after a completion request (sent by a shell function) is
+  /// parsed and the output is ready to be displayed.
+  ///
+  /// Override this to intercept and customize the general
+  /// output of the completions.
+  void renderCompletionResult(CompletionResult completionResult) {
+    final systemShell = this.systemShell;
+    if (systemShell == null) {
+      return;
+    }
+    completionResult.render(completionLogger, systemShell);
+  }
 }

lib/src/handling/completion_result.dart

@@ -0,0 +1,85 @@
+import 'package:cli_completion/src/system_shell.dart';
+import 'package:mason_logger/mason_logger.dart';
+import 'package:meta/meta.dart';
+
+/// {@template completion_result}
+/// Describes the result of a completion handling process.
+/// {@endtemplate}
+///
+/// Generated after parsing a completion request from the shell, it is
+/// responsible to contain the information to be sent back to the shell
+/// (via stdout) including suggestions and its metadata (description).
+///
+/// See also:
+/// - [ValueCompletionResult]
+/// - [EmptyCompletionResult]
+@immutable
+abstract class CompletionResult {
+  /// Creates a [CompletionResult] that contains predefined suggestions.
+  const factory CompletionResult.fromMap(Map<String, String?> completions) =
+      ValueCompletionResult._fromMap;
+
+  const CompletionResult._();
+
+  /// Render the completion suggestions on the [shell].
+  void render(Logger logger, SystemShell shell);
+}
+
+/// {@template value_completion_result}
+/// A [CompletionResult] that contains completion suggestions.
+/// {@endtemplate}
+class ValueCompletionResult extends CompletionResult {
+  /// {@macro value_completion_result}
+  ValueCompletionResult()
+      : _completions = <String, String?>{},
+        super._();
+
+  /// Create a [ValueCompletionResult] with predefined completion suggestions
+  ///
+  /// Since this can be const, calling "addSuggestion" on instances created
+  /// with this constructor may result in runtime exceptions.
+  /// Use [CompletionResult.fromMap] instead.
+  const ValueCompletionResult._fromMap(this._completions) : super._();
+
+  /// A map of completion suggestions to their descriptions.
+  final Map<String, String?> _completions;
+
+  /// Adds an entry to the current pool of suggestions. Overrides any previous
+  /// entry with the same [completion].
+  void addSuggestion(String completion, [String? description]) {
+    _completions[completion] = description;
+  }
+
+  @override
+  void render(Logger logger, SystemShell shell) {
+    for (final entry in _completions.entries) {
+      switch (shell) {
+        case SystemShell.zsh:
+          // On zsh, colon acts as delimitation between a suggestion and its
+          // description. Any literal colon should be escaped.
+          final suggestion = entry.key.replaceAll(':', r'\:');
+          final description = entry.value?.replaceAll(':', r'\:');
+
+          logger.info(
+            '$suggestion${description != null ? ':$description' : ''}',
+          );
+          break;
+        case SystemShell.bash:
+          logger.info(entry.key);
+          break;
+      }
+    }
+  }
+}
+
+/// {@template no_completion_result}
+/// A [CompletionResult] that indicates that no completion suggestions should be
+/// displayed.
+/// {@endtemplate}
+class EmptyCompletionResult extends CompletionResult {
+  /// {@macro no_completion_result}
+  const EmptyCompletionResult() : super._();
+
+  @override
+  void render(Logger logger, SystemShell shell) {}
+}

lib/src/handling/completion_state.dart

@@ -0,0 +1,69 @@
+import 'dart:io';
+
+import 'package:equatable/equatable.dart';
+
+import 'package:meta/meta.dart';
+
+/// {@template completion_state}
+/// A description of the state of a user input when requesting completion.
+/// {@endtemplate}
+@immutable
+class CompletionState extends Equatable {
+  /// {@macro completion_state}
+  @visibleForTesting
+  const CompletionState({
+    required this.cword,
+    required this.cpoint,
+    required this.cline,
+    required this.args,
+  });
+
+  /// The index of the word being completed
+  final int cword;
+
+  /// The position of the cursor upon completion request
+  final int cpoint;
+
+  /// The user prompt that is being completed
+  final String cline;
+
+  /// The arguments that were passed by the user so far
+  final Iterable<String> args;
+
+  @override
+  bool? get stringify => true;
+
+  /// Creates a [CompletionState] from the environment variables set by the
+  /// shell script.
+  static CompletionState? fromEnvironment([
+    Map<String, String>? environmentOverride,
+  ]) {
+    final environment = environmentOverride ?? Platform.environment;
+    final cword = environment['COMP_CWORD'];
+    final cpoint = environment['COMP_POINT'];
+    final compLine = environment['COMP_LINE'];
+
+    if (cword == null || cpoint == null || compLine == null) {
+      return null;
+    }
+
+    final cwordInt = int.tryParse(cword);
+    final cpointInt = int.tryParse(cpoint);
+
+    if (cwordInt == null || cpointInt == null) {
+      return null;
+    }
+
+    final args = compLine.trimLeft().split(' ').skip(1);
+
+    return CompletionState(
+      cword: cwordInt,
+      cpoint: cpointInt,
+      cline: compLine,
+      args: args,
+    );
+  }
+
+  @override
+  List<Object?> get props => [cword, cpoint, cline, args];
+}

lib/src/handling/parser.dart

@@ -0,0 +1,38 @@
+import 'package:args/args.dart';
+import 'package:cli_completion/cli_completion.dart';
+
+/// {@template completion_parser}
+/// The workhorse of the completion system.
+///
+/// It is responsible for discovering the possible completions given a
+/// [CompletionState].
+/// {@endtemplate}
+class CompletionParser {
+  /// {@macro completion_parser}
+  CompletionParser(this._state);
+
+  final CompletionState _state;
+
+  /// Do not complete if there is an argument terminator in the middle of
+  /// the sentence
+  bool _containsArgumentTerminator() {
+    final args = _state.args;
+    return args.isNotEmpty && args.take(args.length - 1).contains('--');
+  }
+
+  /// Parse the given [CompletionState] into a [CompletionResult] given the
+  /// structure of commands and options declared by the CLIs [ArgParser].
+  CompletionResult parse() {
+    if (_containsArgumentTerminator()) {
+      return const EmptyCompletionResult();
+    }
+
+    // todo(renancaraujo): actually suggest useful things
+    return const CompletionResult.fromMap({
+      'Brazil': 'A country',
+      'USA': 'Another country',
+      'Netherlands': 'Guess what: a country',
+      'Portugal': 'Yep, a country'
+    });
+  }
+}

lib/src/system_shell.dart

@@ -11,6 +11,8 @@ enum SystemShell {
   bash;
 
   /// Identifies the current shell.
+  ///
+  /// Based on https://stackoverflow.com/a/3327022
   static SystemShell? current({
     Map<String, String>? environmentOverride,
   }) {

pubspec.yaml

@@ -8,6 +8,7 @@ environment:
 
 dependencies:
   args: ^2.3.1
+  equatable: ^2.0.5
   mason_logger: ^0.2.2
   meta: ^1.8.0
   path: ^1.8.2

test/src/command_runner/commands/handle_completion_command_test.dart

@@ -36,19 +36,46 @@ void main() {
       );
     });
 
-    group('when run', () {
-      test('with no args', () async {
+    group('run', () {
+      test('should display completion', () async {
+        final output = StringBuffer();
+        when(() {
+          commandRunner.completionLogger.info(any());
+        }).thenAnswer((invocation) {
+          output.writeln(invocation.positionalArguments.first);
+        });
+
+        commandRunner.environmentOverride = {
+          'SHELL': '/foo/bar/zsh',
+          'COMP_LINE': 'example_cli some_command --discrete foo',
+          'COMP_POINT': '12',
+          'COMP_CWORD': '2'
+        };
+        await commandRunner.run(['completion']);
+
+        expect(output.toString(), r'''
+Brazil:A country
+USA:Another country
+Netherlands:Guess what\: a country
+Portugal:Yep, a country
+''');
+      });
+
+      test('should supress error messages', () async {
+        final output = StringBuffer();
+        when(() {
+          commandRunner.completionLogger.info(any());
+        }).thenThrow(Exception('oh no'));
+
+        commandRunner.environmentOverride = {
+          'SHELL': '/foo/bar/zsh',
+          'COMP_LINE': 'example_cli some_command --discrete foo',
+          'COMP_POINT': '12',
+          'COMP_CWORD': '2'
+        };
         await commandRunner.run(['completion']);
 
-        verify(() {
-          commandRunner.completionLogger.info('USA');
-        }).called(1);
-        verify(() {
-          commandRunner.completionLogger.info('Brazil');
-        }).called(1);
-        verify(() {
-          commandRunner.completionLogger.info('Netherlands');
-        }).called(1);
+        expect(output.toString(), '');
       });
     });
   });