AGENTS.md

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+This is a Flutter project.
+
+The structure is as follows:
+
+* `abc/` directory contains usual Flutter application
+* `util/` directory contains scripts to run the application
+* `src/` directory contains source code files that are symlinked into `abc/lib/` directory so that Flutter builder can find them
+
+
+All new source code files should go into `src/` directory and be symlinked to `abc/lib/`.

abc/lib/game.dart

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+../../src/game.dart

abc/lib/main.dart

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-import 'package:flutter/material.dart';
-
-void main() {
-  runApp(const MainApp());
-}
-
-class MainApp extends StatelessWidget {
-  const MainApp({super.key});
-
-  @override
-  Widget build(BuildContext context) {
-    return const MaterialApp(
-      home: Scaffold(
-        body: Center(
-          child: Text('Wow, nice, Hello World!'),
-        ),
-      ),
-    );
-  }
-}

abc/lib/main.dart

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+../../src/main.dart

abc/lib/tutFun.dart

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+../../src/tutFun.dart

src/game.dart

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+/// Game logic and supporting types for Birdle,
+/// a five-letter word-guessing game similar to Wordle.
+///
+/// Defines the [Game] state machine and the
+/// [Word], [Letter], and [HitType] data model used to
+/// represent guesses and their evaluation against a hidden word.
+library;
+
+import 'dart:collection';
+import 'dart:math';
+
+/// The result of evaluating a [Letter] of a guess against the hidden word.
+enum HitType {
+  /// The letter hasn't yet been evaluated.
+  none,
+
+  /// The letter matches the hidden word's letter at the same position.
+  hit,
+
+  /// The letter is in the hidden word, but at a different position.
+  partial,
+
+  /// The letter doesn't appear in the hidden word.
+  miss,
+}
+
+/// A single character paired with its [HitType] against the hidden word.
+typedef Letter = ({String char, HitType type});
+
+/// Every word that can be legally entered as a guess.
+const List<String> allLegalGuesses = [...legalWords, ...legalGuesses];
+
+/// Words that can be chosen as the hidden word.
+const List<String> legalWords = ['aback', 'abase', 'abate', 'abbey', 'abbot'];
+
+/// Additional words accepted as guesses beyond those in [legalWords].
+const List<String> legalGuesses = [
+  'aback',
+  'abase',
+  'abate',
+  'abbey',
+  'abbot',
+  'abhor',
+  'abide',
+  'abled',
+  'abode',
+  'abort',
+];
+
+/// Game state of a single round of Birdle,
+/// a five-letter word-guessing game similar to Wordle.
+///
+/// Exposes the state and methods a UI needs to
+/// evaluate guesses and track progress,
+/// but doesn't advance play on its own.
+///
+/// Clients drive each round by calling [guess] to submit an attempt and
+/// [resetGame] to start over.
+class Game {
+  /// The default maximum number of guesses allowed in a [Game].
+  static const int defaultMaxGuesses = 5;
+
+  /// Creates a new game with [maxGuesses] guesses allowed.
+  ///
+  /// If [seed] is provided, the hidden word is
+  /// chosen deterministically from [legalWords],
+  /// otherwise it is selected at random.
+  Game({this.maxGuesses = defaultMaxGuesses, this.seed})
+    : _wordToGuess = _generateInitialWord(seed),
+      _guesses = List<Word>.filled(maxGuesses, Word.empty());
+
+  /// The maximum number of guesses allowed in this game.
+  final int maxGuesses;
+
+  /// The seed used to choose the hidden word,
+  /// or `null` if it was selected at random.
+  final int? seed;
+
+  /// The current hidden word, exposed publicly through [hiddenWord].
+  Word _wordToGuess;
+
+  /// Backing storage for [guesses].
+  ///
+  /// Holds every guess slot in order,
+  /// with unfilled slots represented by empty [Word]s.
+  List<Word> _guesses;
+
+  /// The word the player is trying to guess.
+  Word get hiddenWord => _wordToGuess;
+
+  /// An unmodifiable view of every guess slot, including those still empty.
+  UnmodifiableListView<Word> get guesses => UnmodifiableListView(_guesses);
+
+  /// The most recently submitted guess,
+  /// or an empty [Word] if no guesses have been made.
+  Word get previousGuess {
+    final index = _guesses.lastIndexWhere((word) => word.isNotEmpty);
+    return index == -1 ? Word.empty() : _guesses[index];
+  }
+
+  /// The index of the next empty guess slot, or `-1` if every slot is full.
+  int get activeIndex => _guesses.indexWhere((word) => word.isEmpty);
+
+  /// The number of guesses still available to the player.
+  int get guessesRemaining {
+    if (activeIndex == -1) return 0;
+    return maxGuesses - activeIndex;
+  }
+
+  /// Whether the most recent guess matches the hidden word.
+  bool get didWin {
+    if (_guesses.first.isEmpty) return false;
+
+    for (final letter in previousGuess) {
+      if (letter.type != HitType.hit) return false;
+    }
+
+    return true;
+  }
+
+  /// Whether all allowed guesses have been used without winning.
+  bool get didLose => guessesRemaining == 0 && !didWin;
+
+  /// Picks a new hidden word and clears every submitted guess.
+  void resetGame() {
+    _wordToGuess = _generateInitialWord(seed);
+    _guesses = List<Word>.filled(maxGuesses, Word.empty());
+  }
+
+  /// Evaluates [guess] against the hidden word,
+  /// records the result in [guesses], and returns it.
+  ///
+  /// For finer control, use [isLegalGuess] to validate input or
+  /// [matchGuessOnly] to evaluate without recording the result.
+  Word guess(String guess) {
+    final result = matchGuessOnly(guess);
+    addGuessToList(result);
+    return result;
+  }
+
+  /// Whether [guess] is a legal word to guess.
+  ///
+  /// UIs can call this method before [guess] to
+  /// show players a message when they enter an invalid word.
+  bool isLegalGuess(String guess) => Word.fromString(guess).isLegalGuess;
+
+  /// Evaluates [guess] against the hidden word without advancing the game.
+  Word matchGuessOnly(String guess) =>
+      Word.fromString(guess).evaluateGuess(_wordToGuess);
+
+  /// Stores [guess] in the next empty slot of [guesses].
+  void addGuessToList(Word guess) {
+    final guessIndex = activeIndex;
+    if (guessIndex == -1) {
+      throw StateError('No guesses remaining.');
+    }
+
+    _guesses[guessIndex] = guess;
+  }
+
+  /// Returns the starting hidden word for a new round.
+  ///
+  /// Picks a deterministic word from [legalWords] when [seed] is provided,
+  /// or one at random otherwise.
+  static Word _generateInitialWord(int? seed) =>
+      seed == null ? Word.random() : Word.fromSeed(seed);
+}
+
+/// A five-letter word made up of [Letter]s, each tracking its [HitType].
+class Word with IterableMixin<Letter> {
+  /// Creates a word backed by the specified list of [Letter]s.
+  Word(this._letters);
+
+  /// Creates a word with five blank letters of [HitType.none].
+  factory Word.empty() =>
+      Word(List<Letter>.filled(5, (char: '', type: HitType.none)));
+
+  /// Creates a [Word] from [guess].
+  ///
+  /// Each character is lowercased,
+  /// every [Letter] starts as [HitType.none].
+  factory Word.fromString(String guess) {
+    if (guess.length != 5) {
+      throw ArgumentError.value(
+        guess,
+        'guess',
+        'Must be exactly 5 characters long.',
+      );
+    }
+
+    final letters = guess
+        .toLowerCase()
+        .split('')
+        .map((char) => (char: char, type: HitType.none))
+        .toList();
+    return Word(letters);
+  }
+
+  /// Creates a word chosen at random from [legalWords].
+  factory Word.random() {
+    final random = Random();
+    final nextWord = legalWords[random.nextInt(legalWords.length)];
+    return Word.fromString(nextWord);
+  }
+
+  /// Creates a word chosen from [legalWords] using [seed] as an index.
+  factory Word.fromSeed(int seed) =>
+      Word.fromString(legalWords[seed % legalWords.length]);
+
+  /// An unmodifiable list of [Letter]s that make up this word.
+  final List<Letter> _letters;
+
+  @override
+  Iterator<Letter> get iterator => _letters.iterator;
+
+  /// Whether every [Letter] in this word has no character.
+  @override
+  bool get isEmpty => every((letter) => letter.char.isEmpty);
+
+  @override
+  int get length => _letters.length;
+
+  /// The [Letter] at index [i] in word.
+  Letter operator [](int i) => _letters[i];
+
+  @override
+  String toString() => _letters.map((letter) => letter.char).join().trim();
+
+  /// Returns a multi-line string showing each [Letter] alongside its [HitType].
+  ///
+  /// Used to play the game from the command line.
+  String toStringVerbose() => _letters
+      .map((letter) => '${letter.char} - ${letter.type.name}')
+      .join('\n');
+}
+
+/// Validation and guess-evaluation logic on [Word].
+extension WordUtils on Word {
+  /// Whether this word appears in [allLegalGuesses].
+  bool get isLegalGuess => allLegalGuesses.contains(toString());
+
+  /// Compares this [Word] against the specified [hiddenWord]
+  /// and returns a new [Word] with the same letters,
+  /// but where each [Letter] has new a [HitType] of
+  /// [HitType.hit], [HitType.partial], or [HitType.miss].
+  Word evaluateGuess(Word hiddenWord) {
+    //assert(isLegalGuess);
+
+    final result = List<Letter>.filled(length, (char: '', type: HitType.none));
+    // Counts hidden-word letters that can still be claimed as partial matches.
+    final unmatchedHiddenLetterCounts = <String, int>{};
+
+    // Reserve exact matches before scoring partial matches.
+    for (var i = 0; i < length; i++) {
+      final guessChar = this[i].char;
+      final hiddenChar = hiddenWord[i].char;
+
+      if (guessChar == hiddenChar) {
+        result[i] = (char: guessChar, type: HitType.hit);
+      } else {
+        // Track non-hit hidden letters for the partial-match pass.
+        final unmatchedCount = unmatchedHiddenLetterCounts[hiddenChar] ?? 0;
+        unmatchedHiddenLetterCounts[hiddenChar] = unmatchedCount + 1;
+      }
+    }
+
+    // Spend each remaining hidden letter only once for partial matches.
+    for (var i = 0; i < length; i++) {
+      if (result[i].type == HitType.hit) continue;
+
+      final guessChar = this[i].char;
+      final unmatchedCount = unmatchedHiddenLetterCounts[guessChar] ?? 0;
+      final isPartial = unmatchedCount > 0;
+      if (isPartial) {
+        // Use one available hidden letter for this partial match.
+        unmatchedHiddenLetterCounts[guessChar] = unmatchedCount - 1;
+      }
+
+      result[i] = (
+        char: guessChar,
+        type: isPartial ? HitType.partial : HitType.miss,
+      );
+    }
+
+    return Word(result);
+  }
+}

src/main.dart

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+import 'package:flutter/material.dart';
+import 'game.dart';
+import 'tutFun.dart';
+
+void main() {
+    runApp(const MainApp());
+}
+
+class GamePage extends StatefulWidget {
+    GamePage({super.key});
+
+    @override State<GamePage> createState() => GamePageState();
+}
+    
+class GamePageState extends State<GamePage> {
+    final Game _game = Game();
+
+    @override
+    Widget build(BuildContext context) {
+        return Padding(
+            padding: const EdgeInsets.all(8.0),
+            child: Column(
+                spacing: 5.0,
+                children: [
+                    for (final guess in _game.guesses)
+                        Row(
+                            spacing: 5.0,
+                            children: [
+                                for (final letter in guess)
+                                    Tile(letter.char, letter.type)
+                            ],
+                        ),
+                    GuessInput(
+                        onSubmitGuess: (guess) {
+                            /**/print(guess);
+                            setState(() {
+                                _game.guess(guess);
+                            });
+                        }
+                    ),
+                ],
+            ),
+        );
+    }
+}
+
+class GuessInput extends StatelessWidget {
+    GuessInput({super.key, required this.onSubmitGuess});
+
+    final FocusNode _focusNode = FocusNode();
+    final void Function(String) onSubmitGuess;
+    final TextEditingController _textEditingController = TextEditingController();
+
+    @override
+    Widget build(BuildContext context) {
+        return Row(
+            children: [
+                Expanded(
+                    child: Padding(
+                        child: TextField(
+                            autofocus: true,
+                            controller: _textEditingController,
+                            decoration: InputDecoration(
+                                border: OutlineInputBorder(
+                                    borderRadius: BorderRadius.all(Radius.circular(35)),
+                                ),
+                            ),
+                            focusNode: _focusNode,
+                            maxLength: 5,
+                            onSubmitted: (_) {
+                                processSubmit();
+                            },
+                        ),
+                        padding: const EdgeInsets.all(8.0),
+                    ),
+                ),
+                IconButton(
+                    icon: const Icon(Icons.arrow_circle_up),
+                    onPressed: () {
+                        processSubmit();
+                    },
+                    padding: EdgeInsets.zero,
+                ),
+            ]
+        );
+    }
+
+    void processSubmit() {
+        onSubmitGuess(_textEditingController.text.trim());
+        _textEditingController.clear();
+        _focusNode.requestFocus();
+    }
+}
+
+class MainApp extends StatelessWidget {
+    const MainApp({super.key});
+
+    @override
+    Widget build(BuildContext context) {
+        return MaterialApp(
+            home: Scaffold(
+                appBar: AppBar(
+                    title: Align(
+                        alignment: Alignment.centerLeft,
+                        child: Text("Birdle"),
+                    ),
+                ),
+                body: Center(child: GamePage()),
+            ),
+        );
+    }
+}
+
+class Tile extends StatelessWidget {
+    const Tile(this.letter, this.hitType, {super.key});
+
+    final String letter;
+    final HitType hitType;
+
+    @override
+    Widget build(BuildContext context) {
+        return AnimatedContainer(
+            child: Center(
+                child: Text(
+                    letter.toUpperCase(),
+                    style: Theme.of(context).textTheme.titleLarge,
+                ),
+            ),
+            decoration: BoxDecoration(
+                border: Border.all(color: Colors.grey.shade300),
+                color: tutTileColor(hitType),
+            ),
+            duration: Duration(milliseconds: 300),
+            height: 60,
+            width: 60,
+        );
+    }
+}

src/tutFun.dart

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+library;
+
+import 'package:flutter/material.dart';
+import 'game.dart';
+
+Color tutTileColor(HitType t) {
+    if (t == HitType.hit) {
+        return Colors.green;
+    }
+    if (t == HitType.partial) {
+        return Colors.yellow;
+    }
+    if (t == HitType.miss) {
+        return Colors.grey;
+    }
+    return Colors.white;
+}

util/run-macos

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+#!/bin/bash
+SDIR=$(cd "$(dirname "$0")" ; pwd -P)
+
+cd $SDIR/../abc
+flutter run --enable-experiment=dot-shorthands -d macos