cards: the castle rules engine

domains/games/libs/cards/README.md

@@ -9,6 +9,7 @@ This module provides a set of classes and utilities for building card games.
 
 - Top level module contains core components for building card games.
 - [golf](./golf) is a mostly complete implementation of the game Golf.
+- [castle](./castle) is the rules engine for Castle (Palace).
 
 ## Building
 

domains/games/libs/cards/castle/BUILD.bazel

@@ -0,0 +1,53 @@
+load("@rules_cc//cc:defs.bzl", "cc_library", "cc_test")
+
+# The castle rules engine: immutable GameState/Player value types for
+# the games hub.
+
+cc_library(
+    name = "player",
+    srcs = ["player.cc"],
+    hdrs = ["player.h"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//domains/games/libs/cards",
+        "@com_google_absl//absl/status",
+        "@com_google_absl//absl/status:statusor",
+    ],
+)
+
+cc_library(
+    name = "game_state",
+    srcs = ["game_state.cc"],
+    hdrs = ["game_state.h"],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":player",
+        "//domains/games/libs/cards",
+        "@com_google_absl//absl/status",
+        "@com_google_absl//absl/status:statusor",
+    ],
+)
+
+cc_test(
+    name = "player_test",
+    size = "small",
+    srcs = ["player_test.cc"],
+    deps = [
+        ":player",
+        "//domains/games/libs/cards",
+        "@googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "game_state_test",
+    size = "small",
+    srcs = ["game_state_test.cc"],
+    deps = [
+        ":game_state",
+        ":player",
+        "//domains/games/libs/cards",
+        "//domains/games/libs/cards:dealer",
+        "@googletest//:gtest_main",
+    ],
+)

domains/games/libs/cards/castle/README.md

@@ -0,0 +1,17 @@
+# castle
+
+The rules engine for Castle (the shedding game also played as Palace):
+immutable `Player` and `GameState` value types in the style of
+[`../golf`](../golf), for the games hub.
+
+The rules the engine plays are the contract, stated on `GameState` in
+`game_state.h` and pinned one by one in `game_state_test.cc`: three
+face-down, three face-up, three in hand; a setup phase of hand/face-up
+swaps; lowest ordinary card opens; equal-or-higher plays, twos reset,
+tens and four of a kind burn; must play if able, otherwise pick up the
+pile; face-up then face-down rows once the hand is gone; first out wins,
+last holder loses.
+
+```bash
+bazel test //domains/games/libs/cards/castle/...
+```