feat: implement safe state presentation and bounded serialization

test/host/Makefile

@@ -1,7 +1,7 @@
 CC ?= cc
 CFLAGS ?= -std=c11 -Wall -Wextra -Werror -I../../include
 
-all: test_command_queue test_game_domain test_bot_player test_game_lifecycle
+all: test_command_queue test_game_domain test_bot_player test_game_lifecycle test_state_presenter
 
 test_command_queue: test_command_queue.c ../../src/command_queue.c ../../src/application.c
 	$(CC) $(CFLAGS) $^ -o $@
@@ -11,6 +11,7 @@ run: all
 	./test_game_domain
 	./test_bot_player
 	./test_game_lifecycle
+	./test_state_presenter
 
 test_game_domain: test_game_domain.c ../../src/fleet_generator.c ../../src/game_engine.c
 	$(CC) $(CFLAGS) $^ -o $@
@@ -21,5 +22,8 @@ test_bot_player: test_bot_player.c ../../src/bot_player.c ../../src/fleet_genera
 test_game_lifecycle: test_game_lifecycle.c ../../src/session_manager.c ../../src/game_lifecycle.c ../../src/fleet_generator.c ../../src/game_engine.c
 	$(CC) $(CFLAGS) $^ -o $@
 
+test_state_presenter: test_state_presenter.c ../../src/state_presenter.c
+	$(CC) $(CFLAGS) $^ -o $@
+
 clean:
-	rm -f test_command_queue test_game_domain test_bot_player test_game_lifecycle
+	rm -f test_command_queue test_game_domain test_bot_player test_game_lifecycle test_state_presenter

test/host/test_state_presenter.c

@@ -0,0 +1,92 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "state_presenter.h"
+
+static void set_board(board_t *board) {
+  memset(board, 0, sizeof(*board));
+  board->cells[0] = CELL_SHIP;
+  board->cells[1] = CELL_MISS;
+  board->cells[2] = CELL_HIT;
+  board->cells[99] = CELL_SHIP;
+}
+
+static const char *board_start(const char *json, uint8_t board) {
+  const char *first = strstr(json, "\"boards\":[\"");
+  assert(first != NULL);
+  first += strlen("\"boards\":[\"");
+  return board == 0U ? first : first + kBoardCellCount + 3U;
+}
+
+static void assert_hidden(const char *json, uint8_t board) {
+  const char *cells = board_start(json, board);
+  for (uint8_t index = 0; index < kBoardCellCount; ++index) assert(cells[index] != '1');
+}
+
+static void test_role_views_and_golden_schema(void) {
+  game_state_t state = {0};
+  state.game_id = 42U;
+  state.version = 9U;
+  state.phase = PHASE_IN_PROGRESS;
+  state.mode = MODE_HUMAN;
+  state.current_player = 1U;
+  set_board(&state.boards[0]);
+  set_board(&state.boards[1]);
+  char output[kStateMessageCapacity] = {0};
+  size_t written = 0;
+
+  assert(state_presenter_write(&state, ROLE_PLAYER_1, output, sizeof(output), &written));
+  assert(written == strlen(output));
+  assert(strstr(output, "{\"type\":\"state\",\"version\":9,\"gameId\":42,\"phase\":\"in_progress\",\"mode\":\"human\",\"viewer\":\"player1\",\"turn\":\"player2\",\"boards\":[\"") == output);
+  assert(board_start(output, 0)[0] == '1' && board_start(output, 0)[1] == '2' && board_start(output, 0)[2] == '3');
+  assert_hidden(output, 1);
+
+  assert(state_presenter_write(&state, ROLE_PLAYER_2, output, sizeof(output), &written));
+  assert_hidden(output, 0);
+  assert(board_start(output, 1)[0] == '1');
+
+  assert(state_presenter_write(&state, ROLE_SPECTATOR, output, sizeof(output), &written));
+  assert_hidden(output, 0);
+  assert_hidden(output, 1);
+  assert(board_start(output, 0)[1] == '2' && board_start(output, 1)[2] == '3');
+}
+
+static void test_finished_and_failure_are_safe(void) {
+  game_state_t state = {0};
+  state.game_id = UINT32_MAX;
+  state.version = UINT32_MAX;
+  state.phase = PHASE_FINISHED;
+  state.mode = MODE_BOT;
+  state.current_player = 0U;
+  set_board(&state.boards[0]);
+  set_board(&state.boards[1]);
+  char output[kStateMessageCapacity] = {0};
+  size_t written = 0;
+  assert(state_presenter_write(&state, ROLE_SPECTATOR, output, sizeof(output), &written));
+  assert(written < sizeof(output));
+  assert(board_start(output, 0)[0] == '1' && board_start(output, 1)[99] == '1');
+
+  game_lifecycle_t lifecycle = {0};
+  lifecycle.game.state = state;
+  lifecycle.game.state.phase = PHASE_REMATCH_WAIT;
+  lifecycle.game.state.mode = MODE_HUMAN;
+  lifecycle.cumulative[0].wins = UINT16_MAX;
+  lifecycle.cumulative[1].wins = UINT16_MAX;
+  assert(state_presenter_write_lifecycle(&lifecycle, ROLE_SPECTATOR, output, sizeof(output), &written));
+  assert(written == 371U);
+
+  char unchanged[16];
+  memset(unchanged, 'X', sizeof(unchanged));
+  size_t failure_written = 99U;
+  assert(!state_presenter_write(&state, ROLE_PLAYER_1, unchanged, sizeof(unchanged), &failure_written));
+  assert(failure_written == 0U);
+  for (size_t index = 0; index < sizeof(unchanged); ++index) assert(unchanged[index] == 'X');
+}
+
+int main(void) {
+  test_role_views_and_golden_schema();
+  test_finished_and_failure_are_safe();
+  puts("state presenter tests passed");
+  return 0;
+}