Board state string

There are now seven possible board states for a given coordinate: - no stone; - no stone, black’s territory; - no stone, white’s territory; - black stone; - black stone, white’s territory (dead black stone); - white stone; - white stone, black’s territory (dead white stone).

The GameBoard class in go.js needs to track this stuff. I plan to add an owner field that’s parallel to board, storing black, white, or none for each position. This implies another two states: - black stone, black’s territory; - white stone, white’s territory.

I’m not sure whether these two states should be used in someway, or just be considered invalid. I’m leaning towards invalid.

The state_string representing the board state needs to deal with the new states. These make sense to me:

.	no stone
B	no stone, black’s territory
W	no stone, white’s territory
b	black stone
c	black stone (dead)
w	white stone
x	white stone (dead)

c and x were chosen just because they follow b and c in the alphabet.

Scoring algorithms

Algorithm for counting territory, given: - komi, - the number of black stones captured during the game, - the number of white stones captured during the game, - the coordinates of live black stones, - the coordinates of live white stones, - the number of dead black stones on the board, and - the number of dead white stones on the board.

1. Mark live black stones with b, live white stones with w, and all other coordinates with ?.

2. For each coordinate ?:

   • Search in all directions, stopping at any b or w.

   • If both b and w coordinates are found, then mark all ? with ..

   • If only b coordinates are found, then mark all ? with B.

   • If only w coordinates are found, then mark all ? with W.

3. Black’s territory is the sum of:

   • the number of coordinates marked B,

   • the number of white stones captured during the game, and

   • the number of dead white stones on the board.

4. White’s territory is the sum of:

   • komi,

   • the number of coordinates marked W,

   • the number of black stones captured during the game, and

   • the number of dead black stones on the board.

Algorithm for finding other dead stones, given: - the coordinate of the new dead stone, - the coordinates of all stones of the same colour, and - the coordinates of the live stones of the other colour.

1. Mark the stones of the same colour with ?, the live stones of the other colour with a (for alive), and all other coordinates with ..

2. From the new dead stone, search in all directions, stopping at any a. Mark all ? encountered as d (for dead).

Planned flow for marking dead stones

1. After two consecutive passes, the playing board is used for scoring.

   • The player that passed first gets an email announcement.

   • Both players are able to mark dead stones.

   • The link done appears, and is enabled.

   • Next to the done link, there is some opponent_done text; perhaps, (opponent has clicked done). This text is initially hidden.

2. Clicking done sends the board state to the server.

   • A confirmation dialog is required. This helps with any race conditions: if an update has just been received from the opponent, this player will have a chance to notice.

   • The opponent gets an email.

   • The server stores the final board state for that user.

   • If the opponent has already clicked done and the final board states match, then the game is over.

   • If the opponent has already clicked done and the final board states do not match, then there has been a race condition (as should be evident after reading further)…​ hopefully, this situation is avoidable.

   • If the opponent has not already clicked done, then their opponent_done text is shown on their next update.

   • The done link is disabled.

3. Clicking a stone on the board (either dead or alive) will send that stone to the server.

   • Send the coordinates of the stone that was clicked, as well as the supposed new owner.

   • The server saves the state of the stone, and sends back the new board state.

   • This is completed without link confirmation, since it can be undone…​ no need for the stupid-proof API used when playing the game.

   • If the opponent had previously clicked done, then the opponent’s final board state is cleared, the opponent receives an email, and this player’s opponent_done text is hidden again.

4. Periodically, the UI polls the server for updates.

Details of client-side state transitions during scoring

There are lots of client-side bugs in the UI, so I’m going to get more specific. - has_opponent_moved request succeeds - you_have_passed → scoring - Occurs when opponent clicks pass after you. - Hide the links about passing, etc., and show the done link. - Show initial territory calculations. - other possibilites not relevant. - you click pass - has_opponent_passed → scoring - Occurs when you click pass after opponent. - Hide the links about passing, etc., and show the done link. - Show initial territory calculations. - other possibilites not relevant. - you mark_stone - scoring → scoring - Occurs when you mark a group of stones. - May incorporate changes from opponent as well. - Update territory calculations. - opponent_is_done → scoring - Occurs when you mark a group of stones. - Update the territory calculations. - you click done - scoring → scoring - Occurs when you click done, but the server has a scoring_number higher than the one sent in. - Update the territory calculations. - Update scoring_number. - scoring → you_are_done - Occurs when you click done, and the server has the same scoring_number. - Disable the done link. - opponent_is_done → game_finished - Occurs when you click done. - Hide the done link. - Display game over text. - has_opponent_scored request succeeds - scoring → scoring - Occurs when opponent mark_stone. - Update territory calculations. - Update scoring_number. - scoring → opponent_is_done - Occurs when opponent clicks done. - Update territory calculations, since opponent may have used mark_stone. - Update scoring_number. - you_are_done → scoring - Occurs when opponent mark_stone. - Enable the done link. - Update the territory calculations. - Update scoring_number. - you_are_done → opponent_is_done - Occurs when opponent mark_stone and then clicks done. - Enable the done link. - Update territory calculations. - Update scoring_number. - you_are_done → game_finished - Occurs when opponent clicks done. - Hide the done link. - Display game over text.