feat: implement and exhaustively test the game domain core

include/game_engine.h

@@ -1,6 +1,27 @@
 #pragma once
 
+#include <stdbool.h>
+
+#include "app_interfaces.h"
+#include "fleet_generator.h"
 #include "game_types.h"
 
-/* Rule implementation begins in Milestone 007. */
 typedef struct { game_state_t state; } game_engine_t;
+
+typedef uint8_t game_result_t;
+enum {
+  GAME_RESULT_OK,
+  GAME_RESULT_INVALID_COORDINATE,
+  GAME_RESULT_WRONG_PHASE,
+  GAME_RESULT_NOT_YOUR_TURN,
+  GAME_RESULT_CELL_ALREADY_SHOT,
+  GAME_RESULT_GENERATION_FAILED,
+};
+
+typedef struct { bool hit; bool sunk; bool finished; } shot_result_t;
+
+void game_engine_init(game_engine_t *engine);
+game_result_t game_engine_start(game_engine_t *engine, uint32_t game_id, game_mode_t mode,
+                                const fleet_generator_t *generator);
+game_result_t game_engine_shot(game_engine_t *engine, uint8_t player, coordinate_t coordinate,
+                               shot_result_t *result);