battleship/test/host/test_bot_player.c

#include <assert.h>
#include <stdio.h>

#include "bot_player.h"
#include "fleet_generator.h"
#include "game_engine.h"

typedef struct { uint32_t value; } test_random_t;
typedef struct { uint32_t delay_ms; uint8_t calls; bool accepted; } test_scheduler_t;

static uint32_t next_random(void *context) {
  test_random_t *random = context;
  random->value = random->value * 1664525U + 1013904223U;
  return random->value;
}

static bool schedule_after(void *context, uint32_t delay_ms) {
  test_scheduler_t *scheduler = context;
  scheduler->delay_ms = delay_ms;
  ++scheduler->calls;
  return scheduler->accepted;
}

static bot_player_t new_bot(test_random_t *random, test_scheduler_t *scheduler) {
  bot_player_t bot;
  bot_player_init(&bot, (random_source_t){.next_u32 = next_random, .context = random},
                  (scheduler_t){.schedule_after_ms = schedule_after, .context = scheduler});
  return bot;
}

static void record(bot_player_t *bot, uint8_t x, uint8_t y, bool hit, bool sunk) {
  const bot_shot_result_t result = {.hit = hit, .sunk = sunk};
  bot_player_record_result(bot, (coordinate_t){x, y}, &result);
}

static bool is_adjacent(coordinate_t source, coordinate_t candidate) {
  const int16_t dx = (int16_t)source.x - candidate.x;
  const int16_t dy = (int16_t)source.y - candidate.y;
  return (dx == 0 && (dy == 1 || dy == -1)) || (dy == 0 && (dx == 1 || dx == -1));
}

static void test_targeting_and_cleanup(void) {
  test_random_t random = {.value = 3};
  test_scheduler_t scheduler = {.accepted = true};
  bot_player_t bot = new_bot(&random, &scheduler);
  coordinate_t next = {0};

  record(&bot, 0, 0, true, false);
  assert(bot_player_next_shot(&bot, &next));
  assert(is_adjacent((coordinate_t){0, 0}, next));

  bot_player_init(&bot, (random_source_t){.next_u32 = next_random, .context = &random},
                  (scheduler_t){.schedule_after_ms = schedule_after, .context = &scheduler});
  record(&bot, 4, 4, true, false);
  record(&bot, 5, 4, true, false);
  record(&bot, 6, 4, false, false);
  assert(bot_player_next_shot(&bot, &next));
  assert(next.x == 3U && next.y == 4U);

  bot_player_init(&bot, (random_source_t){.next_u32 = next_random, .context = &random},
                  (scheduler_t){.schedule_after_ms = schedule_after, .context = &scheduler});
  record(&bot, 0, 0, true, true);
  assert(bot.knowledge[0] == BOT_CELL_BLOCKED);
  assert(bot.knowledge[1] == BOT_CELL_BLOCKED);
  assert(bot.knowledge[kBoardWidth] == BOT_CELL_BLOCKED);
  assert(bot_player_next_shot(&bot, &next));
  assert(next.x > 1U || next.y > 1U);
}

static void test_nonblocking_schedule_and_cancel(void) {
  test_random_t random = {.value = 9};
  test_scheduler_t scheduler = {.accepted = true};
  bot_player_t bot = new_bot(&random, &scheduler);
  assert(bot_player_schedule_turn(&bot));
  assert(bot.turn_pending && scheduler.calls == 1U);
  assert(scheduler.delay_ms >= 500U && scheduler.delay_ms <= 900U);
  assert(!bot_player_schedule_turn(&bot));
  bot_player_cancel_turn(&bot);
  assert(!bot.turn_pending);
  scheduler.accepted = false;
  assert(!bot_player_schedule_turn(&bot));
  assert(!bot.turn_pending);
}

static void test_final_bot_shot_uses_only_result(void) {
  test_random_t random = {.value = 17};
  test_scheduler_t scheduler = {.accepted = true};
  bot_player_t bot = new_bot(&random, &scheduler);
  for (uint8_t index = 1; index < kBoardCellCount; ++index) bot.knowledge[index] = BOT_CELL_BLOCKED;
  game_engine_t engine;
  game_engine_init(&engine);
  engine.state.phase = PHASE_IN_PROGRESS;
  engine.state.current_player = 1U;
  engine.state.boards[0].ships_alive = 1U;
  engine.state.boards[0].ships[0] = (ship_t){.x = 0, .y = 0, .length = 1, .horizontal = true};
  engine.state.boards[0].cells[0] = CELL_SHIP;

  coordinate_t target = {0, 0};
  shot_result_t result = {0};
  assert(bot_player_next_shot(&bot, &target));
  /* The strategy sees this result, never engine.state.boards[0]. */
  assert(game_engine_shot(&engine, 1U, target, &result) == GAME_RESULT_OK);
  bot_player_record_result(&bot, target, &(bot_shot_result_t){.hit = result.hit, .sunk = result.sunk});
  assert(result.hit && result.sunk && result.finished);
  assert(engine.state.phase == PHASE_FINISHED && engine.state.winner == 1U);
}

static fleet_generator_t generator_for(test_random_t *random) {
  return (fleet_generator_t){.random = {.next_u32 = next_random, .context = random}};
}

static coordinate_t first_available_target(const board_t *board) {
  for (uint8_t index = 0; index < kBoardCellCount; ++index) {
    if (board->cells[index] == CELL_WATER || board->cells[index] == CELL_SHIP) {
      return (coordinate_t){(uint8_t)(index % kBoardWidth), (uint8_t)(index / kBoardWidth)};
    }
  }
  assert(false);
  return (coordinate_t){0, 0};
}

static void test_ten_thousand_games_without_hidden_board_access(void) {
  for (uint32_t seed = 0; seed < 10000U; ++seed) {
    test_random_t random = {.value = seed + 1000U};
    test_scheduler_t scheduler = {.accepted = true};
    const fleet_generator_t generator = generator_for(&random);
    game_engine_t engine;
    game_engine_init(&engine);
    assert(game_engine_start(&engine, seed + 1U, MODE_BOT, &generator) == GAME_RESULT_OK);
    bot_player_t bot = new_bot(&random, &scheduler);
    bool bot_shot[kBoardCellCount] = {0};
    for (uint16_t step = 0; step < 200U && engine.state.phase == PHASE_IN_PROGRESS; ++step) {
      const uint8_t player = engine.state.current_player;
      coordinate_t coordinate;
      shot_result_t result = {0};
      if (player == 1U) {
        assert(bot_player_next_shot(&bot, &coordinate));
        const uint8_t index = (uint8_t)(coordinate.y * kBoardWidth + coordinate.x);
        assert(!bot_shot[index]);
        bot_shot[index] = true;
        assert(game_engine_shot(&engine, player, coordinate, &result) == GAME_RESULT_OK);
        bot_player_record_result(&bot, coordinate, &(bot_shot_result_t){.hit = result.hit, .sunk = result.sunk});
      } else {
        coordinate = first_available_target(&engine.state.boards[1]);
        assert(game_engine_shot(&engine, player, coordinate, &result) == GAME_RESULT_OK);
      }
    }
    assert(engine.state.phase == PHASE_FINISHED);
    assert(engine.state.winner < kPlayerCapacity);
  }
}

int main(void) {
  test_targeting_and_cleanup();
  test_nonblocking_schedule_and_cancel();
  test_final_bot_shot_uses_only_result();
  test_ten_thousand_games_without_hidden_board_access();
  puts("bot player tests passed");
  return 0;
}