dos-vga-arena-shooter-game/spawn.c

#include <math.h>
#include <stdio.h>

#include "game.h"
#include "movement.h"
#include "const.h"
#include "spawn.h"

struct SpawnPointRange spawnPointRanges[4] = {
   // top
   { .left = TILE_SIZE * 4, .width = TILE_SIZE * 2, .top = TILE_SIZE - 8, .height = TILE_SIZE },
   // right
   { .left = (ARENA_WIDTH_TILES - 1) * TILE_SIZE - 8, .width = TILE_SIZE, .top = TILE_SIZE * 4, .height = TILE_SIZE * 2 },
   // bottom
   { .left = TILE_SIZE * 4, .width = TILE_SIZE * 2, .top = (ARENA_HEIGHT_TILES - 1) * TILE_SIZE - 8, .height = TILE_SIZE },
   // left
   { .left = TILE_SIZE - 8, .width = TILE_SIZE, .top = TILE_SIZE * 4, .height = TILE_SIZE * 2 },
};

int determineEnemyHitPointCalculation(int difficulty, int roll) {
  return hitPointRanges[difficulty][roll];
}

void selectEnemySpawnLocation(
  struct EnemySpawningDetails *spawnDetails,
  struct RabbitPosition *rabbitPosition
) {
  int spawnTry, gate, i;
  int gatePlayerIsFacing = rabbitPosition->mouseAngle / 90;

  // determine which gate the player is at and reduce the likelihood of
  // spawning from that gate
  // * 8 chances to spawn [0, 1] for each gate
  // * if the gate the player is looking at gets [0], reroll
  // * try three times max to limit cost of calculating
  for (spawnTry = 0; spawnTry < 3; ++spawnTry) {
    i = rand() % 12;
    gate = i / 3;

    if (gatePlayerIsFacing == gate && i % 3 != 0) continue;
  }

  spawnDetails->gate = gate;
  spawnDetails->spawnX = spawnPointRanges[gate].left + rand() % spawnPointRanges[gate].width;
  spawnDetails->spawnY = spawnPointRanges[gate].top + rand() % spawnPointRanges[gate].height;
}

void spawnEnemy(
  struct EnemySpawningDetails *spawnDetails,
  struct GlobalGameState *globalGameState
) {
  spawnDetails->enemyPosition->isActive = 1;
  spawnDetails->enemyPosition->willBeInactive = 0;
  spawnDetails->enemyPosition->wasKilled = 0;
  spawnDetails->enemyPosition->hitPoints = determineEnemyHitPointCalculation(
    globalGameState->difficulty,
    rand() % 4
  );
  spawnDetails->enemyPosition->hasLeftGate = 0;
  spawnDetails->enemyPosition->gateExitedFrom = spawnDetails->gate;
  spawnDetails->enemyPosition->enemyMoveDelayStep = 0;
  spawnDetails->enemyPosition->enemyFireDelayStep = ENEMY_FIRE_MIN_DELAY + rand() % ENEMY_FIRE_VARIABLE_DELAY;
  spawnDetails->enemyPosition->enemyPosition[0] = spawnDetails->spawnX;
  spawnDetails->enemyPosition->enemyPosition[1] = spawnDetails->spawnY;
  spawnDetails->enemyPosition->oldEnemyPosition[0] = spawnDetails->spawnX;
  spawnDetails->enemyPosition->oldEnemyPosition[1] = spawnDetails->spawnY;
}

void maybeSpawnEnemy(
  struct GlobalGameState *globalGameState,
  struct EnemyPosition enemyPosition[],
  struct RabbitPosition *rabbitPosition
) {
  char canSpawn;
  int i, availableEnemy;

  struct EnemySpawningDetails spawnDetails;

  if (globalGameState->spawnCooldown-- > 0) return;

  for (i = 0; i < ENEMY_MAX_COUNT; ++i) {
    if (!enemyPosition[i].isActive) {
      availableEnemy = i;
      canSpawn = 1;
      break;
    }
  }

  if (!canSpawn) return;

  spawnDetails.enemyPosition = &enemyPosition[availableEnemy];
  spawnDetails.difficulty = globalGameState->difficulty;
  selectEnemySpawnLocation(
    &spawnDetails,
    rabbitPosition
  );
  spawnEnemy(
    &spawnDetails,
    globalGameState
  );

  globalGameState->spawnCooldown = (
    BASE_ENEMY_SPAWN_COOLDOWN - (globalGameState->difficulty * DIFFICULTY_SPAWN_COOLDOWN_REDUCTION)) +
    MINIMUM_ENEMY_SPAWN_COOLDOWN + rand() % VARIABLE_ENEMY_SPAWN_COOLDOWN;
}