[garak]

• Add mutable Position holding board, turn, kings, castling, epSquare, halfMoves, moveNumber.
• Chess holds a Position instead of seven loose properties. clear() uses Position::empty().
• Entry is now {move, before, previousHash, hash}. Undo restores the saved Position.
• $before shares the live board. Copying it per move would slow perft.
• Chess::$turn stays readable via __get.

Part 4 of #91

Summary by CodeRabbit

• New Features
  • Added a position object to represent the board and current game state.
  • History entries now include the pre-move position and optional hashes.
• Behavior Changes
  • The current turn remains readable but is now read-only; reading unsupported properties raises an error.
  • Undo restores the saved game state while keeping the board connected to the live game. Repetition checks use history hashes.
• Documentation
  • Updated history documentation to explain positions, snapshots, board sharing, and undo behavior.

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• src/Chess.php
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Walkthrough

Chess now stores game state in a Position object. History entries store the pre-move Position and optional hashes. Chess operations, undo, and draw checks use this state and history structure.

Changes: Position state and history

Layer / File(s)	Summary
Position and history contracts src/Position.php, src/Entry.php, src/Chess.php, tests/ConstructorTest.php, docs/history.md	Position holds the board and game-state fields. Entry stores a pre-move Position and optional hashes. Chess initializes a Position and provides read access to turn. Tests and history documentation use the updated structures.
Position-backed chess operations src/Chess.php, tests/ChessPublicator.php	FEN handling, move execution, move generation, king checks, and hash rebuilding now read or update game state through Position.
History restoration and draw checks src/Chess.php, tests/ConstructorTest.php, tests/MoveTest.php	Move history stores a pre-move Position and hashes. Undo restores the prior state and hash. Repetition counting uses entry hashes, and the 100-half-move check reads from Position. Tests check the saved state through Entry::before, verify board identity, and check that a retained entry’s state remains unchanged.

Priority: Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Refactor

Possibly related issues

• p-chess/chess issue 91: This PR adds mutable Position, moves game state out of Chess, and updates Entry as described by the issue.

Merge Risk: Moderate · up to 45a5b

Threefold-repetition results can be wrong in ordinary play. The issue remains open and should be fixed or explicitly accepted before merging.

Security architecture risk: Low · up to 45a5b

The change is contained within the chess library, and the inspected move and undo paths preserve state restoration. History entries intentionally retain access to the live mutable board, so they should not be treated as isolated snapshots. External consumer compatibility and trust assumptions remain unconfirmed.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — A consumer holding a generated history entry can now reach and mutate its originating game's live Board. The demonstrated scope is that in-memory game object; cross-tenant, service, or persistent-store exposure is not established.

Trust Boundaries and Controls

• observed — Direct Board mutation and mutable History access already existed before this PR. The new history-to-Board alias expands object reachability, but the inspected code does not establish that History recipients are less trusted than the game owner.

Resilience and Maintainability Implications

• inferred — Move and speculative-undo operations remain multi-step in-place transitions rather than atomic transactions. Normal restoration paths were inspected, but exception-safe recovery and concurrent sharing were not demonstrated. The base implementation used the same mutation-and-inverse-operation model, so this is not established as a PR-introduced regression.

Hardening Proposals

• proposed — If history is handed to a less-trusted consumer, use a detached read-only representation instead of exposing Entry objects containing the live Board. This is conditional hardening, not an observed boundary violation.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 19.35% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 31 functions across 6 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title identifies the main change, which is the introduction of the Position class and its integration into Chess. The emoji is unnecessary but does not make the title unclear.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 2

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Inline comments:
Review comments at @src/Chess.php:
- Line 353: In undoMove(), bind the restored Position’s board to the live
$this->board when restoring $old->before. Preserve the restored position state
while ensuring it and subsequent recordMove() snapshots remain attached to the
live board.
- Line 673: Update the repetition-counting logic around the
`$hash[$entry->hash]` check to count only occurrences matching
`$this->boardHash`, including the initial position represented by the first
entry’s `previousHash`; do not return true based on a different position that
occurred earlier.

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Actionable comments posted: 1

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Prompt to fix review comments

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Inline comments:
Review comments at @src/Chess.php:
- Line 353: Update the undo restoration in the visible undo flow to clone the
saved `$old->before` Position when assigning `$this->position`. Preserve the
existing board rebinding so the restored position remains connected to the
current board.

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Files selected for processing: 7

• docs/history.md
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• src/Entry.php
• src/Position.php
• tests/ChessPublicator.php
• tests/ConstructorTest.php
• tests/MoveTest.php

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