Refactor PyClient module

client.py

@@ -21,8 +21,9 @@
 from __future__ import annotations
 
 import json
+import pyclient
 
-from pyclient import PyClient
+from pyclient import Agent, PyClient
 from pyclient.games.tic_tac_toe import TicTacToe
 from typing import Any
 
@@ -33,23 +34,28 @@ def main() -> int:
         :return: Exit code
         :rtype: int
     """
-    c = PyClient([
+    c = PyClient(debug=False)
-        "https://bmt001.noordstar.me",
-        "https://bmt001.noordstar.me",
-    ], debug=False)
 
-    out = c.play_game("tic-tac-toe", TicTacToe)
+    players : list[Agent] = [
+        Agent.from_url(url="https://bmt001.noordstar.me/"),
+        Agent.from_url(url="https://bmt001.noordstar.me/"),
+    ]
+
+    out = c.play_game(
+        players=players,
+        start=TicTacToe.empty(),
+    )
 
     inspect_game(out)
 
     return 0
 
-def inspect_game(game : list[tuple[int, dict[str, Any], Any]]) -> None:
+def inspect_game(game : pyclient.GameReplay) -> None:
     """
         Print a diagnostic of a played game to the terminal.
 
         :param game: The results of a played game.
-        :type game: list[typle[int, dict[str, Any], Any]]
+        :type game: pyclient.GameReplay
     """
     max_width = 40
     hbar = max_width * '%'
@@ -69,19 +75,19 @@ def inspect_game(game : list[tuple[int, dict[str, Any], Any]]) -> None:
 
     # Show all moves made throughout the game
     title("Turns taken")
-    for player, action, _ in game:
+    for turn in game.turns:
-        print(f"Player {player} : " + json.dumps(action)[:max_width-12])
+        print(f"Player {turn.player} : " + json.dumps(turn.action)[:max_width-12])
 
     # Show all remaining variables in the finishing state of the game
     title("Final state")
-    final_state = game[-1][2]
+    final_state = game.turns[-1].state
     for k, v in final_state.to_dict().items():
         print(f"{k} => {json.dumps(v)}")
     
     # Some final (usually the most relevant) statistics
     title("Result")
-    print(f"Total turns taken: {len(game)}")
+    print(f"Total turns taken: {len(game.turns)}")
-    print("Winner: " + ("0 (tie)" if final_state.winner() == 0 else f"player {final_state.winner()}"))
+    print(f"Result: {final_state.winner()}")
 
 if __name__ == "__main__":
     raise SystemExit(main())

pyclient/__init__.py

@@ -1,111 +1,16 @@
-"""Public client entry points."""
-
-from typing import Any, Generator, List, Optional
-
-import requests
-
-from .poll import ServerAgent
-
-
-class PyClient:
-    """Host games between discovered server agents."""
-
-    def __init__(self, hosts: List[str], debug : bool = False) -> None:
 """
-        Create a PyClient.
+    Entry points for developers who wish to use the PyClient module.
-
-        :param hosts: URLs of servers that can participate.
-        :type hosts: List[str]
-        :raises ValueError: If no reachable servers are provided.
 """
-        self.agents: List[ServerAgent] = []
-        self.debug = debug
-        self.hosts: List[str] = []
 
-        for host in hosts:
+from .agent import Agent, ServerAgent
-            agent = self.__discover_host(host)
+from .client import PyClient
-            if agent is not None:
+from .replay import GameReplay
-                self.agents.append(agent)
+from .transition import Transition
-                self.hosts.append(agent.url)
 
-        if len(self.hosts) <= 0:
+__all__ = [
-            raise ValueError(
+    "Agent",
-                "No valid hosts found! Check your internet connection or verify the URLs are correct."
+    "GameReplay",
-            )
+    "PyClient",
-
+    "ServerAgent",
-    def __discover_host(self, url: str) -> Optional[ServerAgent]:
+    "Transition",
-        try:
-            return ServerAgent.from_url(url, debug=self.debug)
-        except (requests.exceptions.RequestException, ValueError):
-            return None
-    
-    def gen_game(self, name : str, game : Any, urls : list[str], timeout : float = 1.0, move_default_if_nonexistent : bool = False) -> Generator[tuple[int, dict[str, Any], Any], None, None]:
-        """
-            Play game. Return the results as they've been calculated.
-
-            :param name: Unique identifier string name for the game
-            :type name: str
-            :param game: Game to be played
-            :type game: Any
-            :param urls: List of URLs where players are located
-            :type urls: list[str]
-            :param timeout: Maximum time in seconds to wait for a player to respond
-            :type timeout: float
-            :param move_default_if_nonexistent: If a required player doesn't exist, raise an error. When this is set to true, however, the program will instead assume a player that always takes the default option.
-            :type move_default_if_nonexistent: bool
-            :return: Generator of each turn consisting of a player, what action it took and what that resulted in.
-            :rtype: Generator[tuple[int, dict[str, Any], Any], None, None]
-            :raises KeyError: The number of URLs provided is too low, the game requires more players.
-        """
-        agents = [
-            ServerAgent(url=url, name="", games={}, debug=self.debug)
-            for url in urls
 ]
-
-        current_state = game.empty()
-
-        while current_state.winner() is None:
-            player : int = current_state.player_to_move()
-
-            if len(agents) < player:
-                if not move_default_if_nonexistent:
-                    raise KeyError(
-                        f"Game requires at least {player} players to exist, found only {len(agents)}"
-                    )
-                
-                current_state = current_state.move_default()
-
-                yield player, {}, current_state
-            
-            else:
-                agent = agents[player-1]
-                payload = agent.poll(
-                    game=(name + "/" + current_state.action_name()).strip("/"),
-                    payload=current_state.as_seen_by(player),
-                    timeout=timeout,
-                )
-
-                # Calculate move
-                current_state = current_state.move(payload)
-
-                yield player, payload or {}, current_state
-
-    def play_game(self, name : str, game, timeout : float = 1.0) -> list[tuple[int, dict[str, Any], Any]]:
-        """
-            Play a given game. Ask the registered agents to participate.
-        """
-        urls = [ agent.url for agent in self.agents if name in agent.games ]
-        
-        return list(self.gen_game(
-            name=name, game=game, urls=urls, timeout=timeout,
-            move_default_if_nonexistent=False,
-        ))
-
-    def verify_host(self, url: str) -> bool:
-        """
-        Verify whether the URL seems to contain a link to a playable server.
-        """
-        return self.__discover_host(url) is not None
-
-
-__all__ = ["PyClient", "ServerAgent"]

pyclient/agent.py

@@ -0,0 +1,156 @@
+"""
+    This module hosts various agents that can participate in games.
+
+    Examples of possible agents could be:
+
+    - An online server
+    - A locally running neural network
+    - A hacker who participates from the terminal
+    - A user interface that allows users to play against their own creations
+"""
+
+from dataclasses import dataclass
+from typing import Any, Dict, Optional, Tuple, Union
+
+import requests
+import time
+
+@dataclass(frozen=True)
+class Agent:
+    """
+        Base class of a game participant. Mostly used to inherit from.
+    """
+
+    debug : bool
+    games : dict[str, dict[str, Any]]
+    profile : dict[str, Any]
+
+    @classmethod
+    def from_url(cls, url : str, **kwargs) -> "ServerAgent":
+        """
+            Create an agent based on a URL.
+
+            :param url: The URL where the agent can be accessed.
+            :type url: str            
+            :return: An agent that contacts a server when polled.
+            :rtype: ServerAgent
+        """
+        return ServerAgent.from_server_url(url=url, **kwargs)
+
+    @property
+    def name(self) -> str:
+        """
+            The name by which the agent calls itself.
+        """
+        return str(self.profile.get("name", "Nameless agent"))
+
+    def poll(
+        self,
+        game : str,
+        payload : dict[str, Any],
+        **kwargs
+    ) -> Optional[dict[str, Any]]:
+        """
+            Ask the agent to make a move.
+
+            :param game: The game the ServerAgent is asked to play.
+            :type game: str
+            :param payload: The JSON payload that represents the game's state.
+            :type payload: dict[str, Any]
+            :return: The agent's response, or None if the agent doesn't respond.
+            :rtype: Optional[dict[str, Any]]
+        """
+        print(f"WARNING: The `poll` method is not defined on the {self.__class__.__name__} class")
+        return None
+
+@dataclass(frozen=True)
+class ServerAgent(Agent):
+    """
+        Agent that reaches out to the internet to poll for moves.
+    """
+
+    url : str
+
+    @classmethod
+    def from_server_url(
+        cls,
+        url: str,
+        timeout: float | tuple[float, float] | None = 10.0,
+        debug : bool = False
+    ) -> "ServerAgent":
+        """
+        Create a server agent by polling its discovery endpoint.
+
+        :param url: The URL that the server can be reached at.
+        :type url: str
+        :param timeout: Request timeout.
+        :type timeout: float | tuple[float, float] | None
+        :param debug: Enables debug mode
+        :type debug: bool
+        :return: The server's representation as an agent.
+        :rtype: ServerAgent
+        :raises requests.exceptions.HTTPError: If the server returns a
+            non-success HTTP status code.
+        :raises requests.exceptions.RequestException: If the request fails
+            before a response is received.
+        :raises ValueError: If the response body is not a JSON object or if the
+            payload contains malformed discovery fields.
+        """
+        response = requests.get(url.rstrip("/") + "/", timeout=timeout)
+        response.raise_for_status()
+        content = response.json()
+
+        if not isinstance(content, dict):
+            raise ValueError("Server discovery responses must be JSON objects.")
+
+        raw_name = content.get("name", "")
+        name = "" if raw_name is None else str(raw_name)
+
+        games: dict[str, dict[str, Any]] = {}
+        raw_games = content.get("games", {})
+        if raw_games is not None:
+            if not isinstance(raw_games, dict):
+                raise ValueError("The 'games' field must be a JSON object when provided.")
+
+            for game_name, profile in raw_games.items():
+                if isinstance(profile, dict):
+                    games[str(game_name)] = profile
+
+        return cls(
+            debug=debug,
+            games=games,
+            profile=content,
+            url=url,
+        )
+    
+    def poll(
+        self,
+        game : str,
+        payload : dict[str, Any],
+        **kwargs
+    ) -> Optional[dict[str, Any]]:
+        """
+            Inquire a game to make a move.
+
+            :param game: The game the ServerAgent is asked to play.
+            :type game: str
+            :param payload: The JSON payload that represents the game's state.
+            :type payload: dict[str, Any]
+            :return: The server's response, or None if the server did not respond.
+            :rtype: Optional[dict[str, Any]]
+        """
+        url = f"{self.url.rstrip('/')}/{game.lstrip('/')}"
+        timeout = float(kwargs.get("timeout", 1.0))
+
+        try:
+            response = requests.get(url, json=payload, timeout=timeout)
+            response.raise_for_status()
+            content = response.json()
+        except (requests.exceptions.RequestException, ValueError):
+            return None
+
+        if self.debug:
+            print(f"[DBG] Agent `{self.name}` returned:")
+            print(content)
+
+        return content if isinstance(content, dict) else None

pyclient/client.py

@@ -0,0 +1,71 @@
+"""
+    This module hosts the PyClient class. You can use this class to simulate
+    games among mulltiple agents.
+"""
+
+from __future__ import annotations
+
+from .agent import Agent
+from .games import Game
+from .replay import GameReplay, Turn
+from dataclasses import dataclass
+from typing import Any, Generator
+
+@dataclass(frozen=True)
+class PyClient:
+    """
+        Host games among multiple agents.
+    """
+
+    debug : bool
+
+    def gen_game(self, players : list[Agent], start : Game) -> Generator[Turn, None, None]:
+        """
+            Generate a game by polling the players.
+
+            :param players: All players that wish to participate.
+            :type players: list[Agent]
+            :param start: The start state of the game.
+            :type start: Game
+            :return: A generator that yields turns.
+            :rtype: Generator[Turn, None, None]
+        """
+        current_state = start
+
+        while current_state.winner() is None:
+            player = current_state.player_to_move()
+
+            if len(players) < player:
+                # Player not found! Make a default move.
+                current_state = current_state.move_default()
+            
+                yield Turn(action={}, player=player, state=current_state)
+            
+            else:
+                agent = players[player - 1]
+                payload = agent.poll(
+                    game=current_state.game_name(),
+                    payload=current_state.as_seen_by(player=player),
+                )
+
+                # Calculate move
+                current_state = current_state.move(payload=payload)
+
+                yield Turn(action=payload, player=player, state=current_state)
+
+    def play_game(self, players : list[Agent], start : Game) -> GameReplay:
+        """
+            Generate a game by polling the players. Collect all moves in a
+            summary.
+
+            :param players: All players that wish to participate.
+            :type players: list[Agent]
+            :param start: The start state of the game.
+            :type start: Game
+            :return: Summary describing how the game went.
+            :rtype: GameReplay
+        """
+        return GameReplay(
+            start=start,
+            turns=list(self.gen_game(players=players, start=start)),
+        )

pyclient/games/__init__.py

@@ -0,0 +1,12 @@
+"""
+    Entry point for collecting all known games
+"""
+
+from .game import FinishState, Game
+from .tic_tac_toe import TicTacToe
+
+__all__ = [
+    "FinishState",
+    "Game",
+    "TicTacToe",
+]

pyclient/games/game.py

@@ -0,0 +1,138 @@
+"""
+    This module contains the base class for any game.
+
+    If you'd like to create a new game, please copy this module and fill in
+    all the necessary methods in order to have a functioning game.
+"""
+
+from __future__ import annotations
+
+from enum import Enum, auto
+from typing import Any
+
+class FinishState(Enum):
+    draw = auto()
+    loss = auto()
+    win = auto()
+
+class Game:
+    """
+        Base class for all games.
+
+        A game is always a snapshot of a game that is paused because it waits
+        for a user to make a move.
+    """
+
+    def action_name(self) -> str:
+        """
+            Return the type of action to take. Please only use alphanumeric
+            characters.
+
+            This helps the player understand what they are supposed to do.
+            For example, in Risk, you can use this to explain whether they are
+            expected to "recruit" or "attack" or "move" with their troops.
+
+            If all moves require the same action (such as with tic-tac-toe),
+            you can leave this to return an empty string.
+        """
+        return ""
+    
+    def as_seen_by(self, player : int) -> dict[str, Any]:
+        """
+            From the perspective of a given player, return the game's state.
+
+            Note that it is very common in games for players to not have ALL
+            the details available. For example, in card games, you are
+            generally unable to see the cards in your opponents' hands.
+
+            The game's state is formatted in a way that makes it easy to
+            convert it to JSON or a tensor.
+
+            :param player: Player. Counting starts from one.
+            :type player: int
+            :return: The game's state from the perspective of the player.
+            :rtype: dict[str, Any]
+        """
+        return {}
+
+    @classmethod
+    def empty(cls) -> "Game":
+        """
+            Create a new game.
+
+            Use this method to shuffle the cards, to arrange pieces on the
+            board, and set up the state in a way where the first player can
+            start to make its move.
+
+            :return: A game that's ready to start.
+            :rtype: Game
+        """
+        return cls()
+    
+    def game_name(self) -> str:
+        """
+            Return a non-empty string that uniquely identifies the game.
+            When creating a new unspecified game, please respect the Java
+            package naming convention.
+        """
+        return "default-game"
+    
+    def move_default(self) -> "Game":
+        """
+            Fallback move option for when a user isn't available or cannot
+            decide. Program this move to be predictable, and resemble an
+            attempted skip as much as possible. For example:"
+
+            - In Go, place a tile in an empty space near the top-left corner
+            - In Monopoly, choose not to buy anything
+            - In poker, check. (Or fold after a raise.)
+            - In a maze, choose the left-most path
+        """
+        # NOTE: Games are meant to be immutable values!
+        # As such, you should always consider creating a deep copy of oneself,
+        # do not simply return self if it might update.
+        return self
+    
+    def move(self, payload : dict[str, Any] | None = None) -> "Game":
+        """
+            Make a move on behalf of whose turn it is.
+
+            :param payload: Dictionary containing the player's response.
+            :type payload: dict[str, Any] | None
+            :return: A new instance of the game where a new action is required.
+            :rtype: Game
+        """
+        if not isinstance(payload, dict):
+            return self.move_default()
+    
+        # NOTE: Games are meant to be immutable values!
+        # As such, you should always consider creating a deep copy of oneself,
+        # do not simply return self if it might update.
+        return self
+    
+    def player_to_move(self) -> int:
+        """
+            Return which player is currently meant to move.
+
+            :return: Which player to move. Counting starts from one.
+            :rtype: int
+        """
+        return 1
+    
+    def to_dict(self) -> dict[str, Any]:
+        """
+            Return a dictionary containing the full game state.
+
+            :return: The current game's state.
+            :rtype: dict[str, Any]
+        """
+        return {}
+    
+    def winner(self) -> dict[int, FinishState] | None:
+        """
+            Determine whether the game has ended.
+
+            :return: A list detailing which players have won, lost or drawn - or None if the game hasn't finished.
+            :rtype: dict[int, FinishState] | None
+        """
+        return {}

pyclient/games/tic_tac_toe.py

@@ -1,6 +1,14 @@
+"""
+    This module hosts the game of tic-tac-toe, the traditional game where
+    you're trying to place 3 items in a row in a 3x3-grid.
+"""
+
+from __future__ import annotations
+
+from .game import FinishState, Game
 from dataclasses import dataclass
 from enum import Enum, auto
-from typing import Any, Dict, List, Optional
+from typing import Any, Optional
 
 class Field(Enum):
     X = auto()
@@ -20,7 +28,7 @@ class Field(Enum):
                 return ""
 
 @dataclass(frozen=True)
-class TicTacToe:
+class TicTacToe(Game):
     field_1 : Field
     field_2 : Field
     field_3 : Field
@@ -172,7 +180,7 @@ class TicTacToe:
     def action_name(self) -> str:
         return ""
     
-    def as_seen_by(self, player : int) -> Dict[str, Any]:
+    def as_seen_by(self, player : int) -> dict[str, Any]:
         """
             Return the view of the game from the perspective of a given player.
 
@@ -203,6 +211,9 @@ class TicTacToe:
             field_7=Field.empty, field_8=Field.empty, field_9=Field.empty,
         )
 
+    def game_name(self) -> str:
+        return "tic-tac-toe"
+    
     def move_default(self) -> "TicTacToe":
         """
             Have a player take a "default" move. They'll take this move
@@ -229,7 +240,7 @@ class TicTacToe:
                 "No legal moves exist anymore on this tic-tac-toe board."
             )
 
-    def move(self, payload : Optional[Dict[str, Any]] = None) -> "TicTacToe":
+    def move(self, payload : Optional[dict[str, Any]] = None) -> "TicTacToe":
         """
             Have a player make a move. Based on this information, update the
             game.
@@ -271,7 +282,7 @@ class TicTacToe:
         """
         return 1 if self.count_x() <= self.count_o() else 2
     
-    def to_dict(self) -> Dict[str, Any]:
+    def to_dict(self) -> dict[str, Any]:
         return {
             "1": str(self.field_1),
             "2": str(self.field_2),
@@ -284,12 +295,12 @@ class TicTacToe:
             "9": str(self.field_9),
         }
     
-    def winner(self) -> int | None:
+    def winner(self) -> dict[int, FinishState] | None:
         """
             Returns whether the board indicates that there's a winner.
 
             :return: The winning player, zero in case of a tie, or None if there's no winner yet.
-            :rtype: int | None
+            :rtype: dict[int, FinishState] | None
         """
         win_lines = [
             [ 1, 2, 3, ],
@@ -303,15 +314,17 @@ class TicTacToe:
         ]
 
         d = self.to_dict()
+        out = { 1 : FinishState.loss, 2 : FinishState.loss, }
 
         for player, symbol in [ ( 1, str(Field.X) ), ( 2, str(Field.O) ) ]:
             for win_line in win_lines:
                 if all(d[str(w)] == symbol for w in win_line):
-                    return player
+                    out[player] = FinishState.win
+                    return out
         else:
             # Check for draw
             if all(item != "" for item in d.values()):
-                return 0
+                return { 1 : FinishState.draw, 2 : FinishState.draw, }
             
             return None
 

pyclient/poll.py

@@ -1,102 +0,0 @@
-"""Discovery and polling helpers for Bot-Man-Toe servers."""
-
-from typing import Any, Dict, Optional, Tuple, Union
-
-import requests
-import time
-
-class ServerAgent:
-    """Representation of a server that can host one or more games."""
-
-    def __init__(self, url: str, name: str, games: Dict[str, Dict[str, Any]], debug : bool = False) -> None:
-        """
-        Create a server representation.
-
-        :param url: The URL used to discover the server.
-        :type url: str
-        :param name: Name of the server's player.
-        :type name: str
-        :param games: Games the server is willing to play.
-        :type games: Dict[str, Dict[str, Any]]
-        """
-        self.debug = debug
-        self.games = games
-        self.name = name
-        self.url = url.strip("/")
-
-    @classmethod
-    def from_url(
-        cls,
-        url: str,
-        timeout: Optional[Union[float, Tuple[float, float]]] = 10.0,
-        debug : bool = False
-    ) -> "ServerAgent":
-        """
-        Create a server agent by polling its discovery endpoint.
-
-        The root endpoint is expected to return a JSON object with an optional
-        ``name`` field and an optional ``games`` mapping.
-
-        :param url: The URL that the server can be reached at.
-        :type url: str
-        :param timeout: Request timeout passed to ``requests.get``.
-        :type timeout: Optional[Union[float, Tuple[float, float]]]
-        :return: The server's representation.
-        :rtype: ServerAgent
-        :raises requests.exceptions.HTTPError: If the server returns a
-            non-success HTTP status code.
-        :raises requests.exceptions.RequestException: If the request fails
-            before a response is received.
-        :raises ValueError: If the response body is not a JSON object or if the
-            payload contains malformed discovery fields.
-        """
-        response = requests.get(url.rstrip("/") + "/", timeout=timeout)
-        response.raise_for_status()
-        content = response.json()
-
-        if not isinstance(content, dict):
-            raise ValueError("Server discovery responses must be JSON objects.")
-
-        raw_name = content.get("name", "")
-        name = "" if raw_name is None else str(raw_name)
-
-        games: Dict[str, Dict[str, Any]] = {}
-        raw_games = content.get("games", {})
-        if raw_games is not None:
-            if not isinstance(raw_games, dict):
-                raise ValueError("The 'games' field must be a JSON object when provided.")
-
-            for game_name, profile in raw_games.items():
-                if isinstance(profile, dict):
-                    games[str(game_name)] = profile
-
-        return cls(url=url, name=name, games=games, debug=debug)
-    
-    def poll(self, game: str, payload: Dict[str, Any], timeout: float = 1.0) -> Optional[Dict[str, Any]]:
-        """
-            Inquire a game to make a move.
-
-            :param game: The game the ServerAgent is asked to play.
-            :type game: str
-            :param payload: The JSON payload that represents the game's state.
-            :type payload: Dict[str, Any]
-            :param timeout: Maximum number of seconds to wait for a move.
-            :type timeout: float
-            :return: The server's response, or None if the server did not respond
-                in time or returned an invalid response.
-            :rtype: Optional[Dict[str, Any]]
-        """
-        url = f"{self.url.rstrip('/')}/{game.lstrip('/')}"
-
-        try:
-            response = requests.get(url, json=payload, timeout=timeout)
-            response.raise_for_status()
-            content = response.json()
-        except (requests.exceptions.RequestException, ValueError):
-            return None
-
-        if self.debug:
-            print(f"[DBG] Agent `{self.name}` returned:")
-            print(content)
-
-        return content if isinstance(content, dict) else None

pyclient/replay.py

@@ -0,0 +1,92 @@
+"""
+    This module helps describe & evaluate previously played games.
+"""
+
+from __future__ import annotations
+
+from .games import Game
+from .transition import Transition
+from dataclasses import dataclass
+from typing import Any, Generator
+
+@dataclass(frozen=True)
+class GameReplay:
+    """
+        Game replay detailing the events of what happened in a previously
+        played game.
+    """
+
+    start : Game
+    turns : list[Turn]
+
+    def gen_transitions(self) -> Generator[Transition, None, None]:
+        """
+            Generate transitions from the game's summary.
+
+            :return: Transitions that describe consequences throughout the game.
+            :rtype: Generator[Transition, None, None]
+        """
+        prev_state : Game = self.start
+        seen_participants : dict[int, tuple[Game, dict[str, Any]]] = {}
+
+        for turn in self.turns:
+            # If a player has made a move before, show the current state as
+            # the result of their previous turn's action.
+            state, action = seen_participants.get(turn.player, ( None, {} ))
+            if state is not None:
+                yield Transition(
+                    full_state_after=prev_state,
+                    full_state_before=state,
+                    move=action,
+                    player=turn.player,
+                )
+            
+            # Save the player's current action for the future.
+            # We'll see how this action worked out!
+            seen_participants[turn.player] = ( prev_state, turn.action )
+            prev_state = turn.state
+        
+        else:
+            # Record to all players that the game has finished.
+            for player, ( state, action ) in seen_participants.items():
+                yield Transition(
+                    full_state_after=prev_state,
+                    full_state_before=state,
+                    move=action,
+                    player=player,
+                )
+    
+    def to_transitions(self, player : int | None = None) -> list[Transition]:
+        """
+            Convert the GameSummary into a list of transitions that can be
+            fed to a system that can reflect on past moves.
+
+            :param player: Filter to only show transitions of a given player.
+            :type player: int | None
+            :return: A list of transitions extracted from a game.
+            :rtype: list[Transition]
+        """
+        if player is None:
+            return list(self.gen_transitions())
+        else:
+            return [ t for t in self.gen_transitions() if t.player == player ]
+
+@dataclass(frozen=True)
+class Turn:
+    """
+        A turn is a snapshot of a moment where a user was prompted to take an
+        action. A turn consists of three values:
+
+        1. The player (number) that was prompted for an action
+        2. The action that that player has decided to take
+        3. The game's state after the action was prompted and before the next
+            prompted move.
+
+        Note that turns might not correlate with in-game turns. A user might
+        take multiple actions in a Risk game (recruit, attack, move) and each
+        action is registered as an independent move.
+    """
+
+    player : int
+    action : dict[str, Any]
+    state : Game

pyclient/transition.py

@@ -0,0 +1,110 @@
+"""
+    The transition module allows agents to reflect on the choices they
+    (and others) have made during recent games.
+
+    Agents are generally intended to be stateless, so this allows them to
+    later understand how well certain moves turned out.
+"""
+
+from __future__ import annotations
+
+from .games import FinishState, Game
+from dataclasses import dataclass
+from typing import Any, Generator
+
+@dataclass(frozen=True)
+class Transition:
+    """
+        A transition is a simplified view on a user's single move.
+
+        The transition contains the game state, the move they made,
+        and what the game ended up looking like the next time they were
+        prompted for a move. If the game ends, the `state_after` field contains
+        the final state.
+    """
+
+    full_state_after : Game
+    full_state_before : Game
+    move : dict[str, Any]
+    player : int
+
+    @property
+    def end_result(self) -> FinishState | None:
+        """
+            Return the result of this move if it caused the game to end,
+            or None if the game still continues after this.
+
+            :return: The player's result in the game with this move.
+            :rtype: FinishState | None
+        """
+        w = self.full_state_after.winner()
+
+        if w is None:
+            return None
+        
+        return w[self.player]
+
+    @property
+    def game_has_ended(self) -> bool:
+        """
+            Shorthand property for whether this was the player's last move.
+
+            Tip: Use the methods `move_caused_draw`, `move_caused_loss` and
+            `move_caused_win` to determine the outcome.
+        """
+        return self.full_state_after.winner() is not None
+
+    @property
+    def move_caused_draw(self) -> bool:
+        """
+            Shorthand property for whether this move caused the player to draw.
+
+            :rtype: bool
+        """
+        return self.end_result == FinishState.draw
+    
+    @property
+    def move_caused_loss(self) -> bool:
+        """
+            Shorthand property for whether this move caused the player to lose.
+
+            :rtype: bool
+        """
+        return self.end_result == FinishState.loss
+    
+    @property
+    def move_caused_win(self) -> bool:
+        """
+            Shorthand property for whether this move caused the player to win.
+
+            :rtype: bool
+        """
+        return self.end_result == FinishState.win
+    
+    @property
+    def state_after(self) -> dict[str, Any]:
+        """
+            The initial state that the agent was shown after they were asked for
+            a move. 
+            
+            Keep in mind that this state does not necessarily contain
+            ALL information, as players are often partially kept in the dark
+            about a game's state.
+
+            :rtype: dict[str, Any]
+        """
+        return self.full_state_after.as_seen_by(self.player)
+    
+    @property
+    def state_before(self) -> dict[str, Any]:
+        """
+            The initial state that the agent was shown when they were asked for
+            a move. 
+            
+            Keep in mind that this state does not necessarily contain
+            ALL information, as players are often partially kept in the dark
+            about a game's state.
+
+            :rtype: dict[str, Any]
+        """
+        return self.full_state_before.as_seen_by(self.player)