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

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

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

#include "system/mouse_io.h"
#include "system/pc_stuff.h"
#include "system/vga.h"

#define SIGN(x) ((x > 0) - (x < 0))

void captureAndLimitMousePosition(
  struct RabbitPosition *pos,
  struct MouseStatus *mouseStatus
) {
  pos->oldMouseDotPosition[0] = pos->mouseDotPosition[0];
  pos->oldMouseDotPosition[1] = pos->mouseDotPosition[1];

  pos->mouseDotPosition[0] = mouseStatus->xPosition;
  pos->mouseDotPosition[1] = mouseStatus->yPosition;

  if (pos->mouseDotPosition[0] < MOUSE_LIMIT_LEFT) pos->mouseDotPosition[0] = MOUSE_LIMIT_LEFT;
  if (pos->mouseDotPosition[0] >= MOUSE_LIMIT_RIGHT) pos->mouseDotPosition[0] = MOUSE_LIMIT_RIGHT;
  if (pos->mouseDotPosition[1] < MOUSE_LIMIT_TOP) pos->mouseDotPosition[1] = MOUSE_LIMIT_TOP;
  if (pos->mouseDotPosition[1] >= MOUSE_LIMIT_BOTTOM) pos->mouseDotPosition[1] = MOUSE_LIMIT_BOTTOM;
}

// now this is ray casting
struct TargetMousePosition {
  int x, y;
};

void constrainMousePosition(
  struct RabbitPosition *pos,
  struct TargetMousePosition *target
) {
  int i, didChange, which;
  int currentX, currentY;

  float xCrossover, yCrossover;
  float maxDeltaX, maxDeltaY, fixHypotenuse, fixDistance;
  float currentDeltaX, currentDeltaY;
  float adjustedDeltaX, adjustedDeltaY;
  int considerX, considerY;

  maxDeltaX = sin(pos->mouseAngle * DEG2RAD) * MOUSE_DISTANCE;
  maxDeltaY = -cos(pos->mouseAngle * DEG2RAD) * MOUSE_DISTANCE;

  currentX = target->x + maxDeltaX;
  currentY = target->y + maxDeltaY;

  if (maxDeltaX > 0) {
    currentDeltaX = ARENA_RIGHT_EDGE - target->x;
  } else {
    currentDeltaX = target->x - ARENA_LEFT_EDGE;
  }

  if (maxDeltaY > 0) {
    currentDeltaY = ARENA_BOTTOM_EDGE - target->y;
  } else {
    currentDeltaY = target->y - ARENA_TOP_EDGE;
  }

  which = -1;

  considerY = currentY > ARENA_BOTTOM_EDGE || currentY < ARENA_TOP_EDGE;
  considerX = currentX > ARENA_RIGHT_EDGE || currentX < ARENA_LEFT_EDGE;

  if (considerX || considerY) {
    if (considerX && considerY) {
      which = currentDeltaY < currentDeltaX;
    } else {
      which = considerY;
    }
  }

  switch (which) {
    case 0: // x
      if (maxDeltaX > 0) {
        adjustedDeltaX = ARENA_RIGHT_EDGE - target->x;
      } else {
        adjustedDeltaX = -(target->x - ARENA_LEFT_EDGE);
      }

      adjustedDeltaY = (adjustedDeltaX / sin(pos->mouseAngle * DEG2RAD)) * -cos(pos->mouseAngle * DEG2RAD);
      if (fabs(adjustedDeltaY) > currentDeltaY) {
        adjustedDeltaY = SIGN(adjustedDeltaY) * currentDeltaY;
      }

      break;
    case 1: // y
      if (maxDeltaY > 0) {
        adjustedDeltaY = ARENA_BOTTOM_EDGE - target->y;
      } else {
        adjustedDeltaY = -(target->y - ARENA_TOP_EDGE);
      }

      adjustedDeltaX = (adjustedDeltaY / -cos(pos->mouseAngle * DEG2RAD)) * sin(pos->mouseAngle * DEG2RAD);
      if (fabs(adjustedDeltaX) > currentDeltaX) {
        adjustedDeltaX = SIGN(adjustedDeltaX) * currentDeltaX;
      }

      break;
  }

  if (which != -1) {
    currentX = target->x + adjustedDeltaX;
    currentY = target->y + adjustedDeltaY;
  }

  target->x = currentX;
  target->y = currentY;
}

void calculateTargetAngle(
  struct RabbitPosition *pos
) {
  float distanceX, distanceY;
  float angle, fixHypotenuse, fixDistance;
  struct TargetMousePosition targetMousePosition;

  // Position the cursor
  distanceX = pos->mouseDotPosition[0] - pos->rabbitPosition[0];
  distanceY = pos->mouseDotPosition[1] - pos->rabbitPosition[1];

  // edge case -- top left corner
  if (
    pos->rabbitPosition[0] == ARENA_LEFT_EDGE &&
    pos->rabbitPosition[1] == ARENA_TOP_EDGE &&
    distanceX == 0 &&
    distanceY == 0
  ) {
    angle = 315;
  } else {
    angle = atan2(distanceY, distanceX) * RAD2DEG + 90;
    if (angle < 0) angle += 360;
  }

  pos->mouseAngle = angle;

  pos->oldMousePosition[0] = pos->mousePosition[0];
  pos->oldMousePosition[1] = pos->mousePosition[1];

  targetMousePosition.x = pos->rabbitPosition[0];
  targetMousePosition.y = pos->rabbitPosition[1];

  constrainMousePosition(pos, &targetMousePosition);

  pos->mousePosition[0] = targetMousePosition.x;
  pos->mousePosition[1] = targetMousePosition.y;
}


void handleEnemyMovement(
  struct EnemyPosition enemyPosition[],
  struct RabbitPosition *pos
) {
  char hasExitedGate;
  int i, xDistance, yDistance;

  for (i = 0; i < ENEMY_MAX_COUNT; ++i) {
    if (!enemyPosition[i].isActive) continue;

    enemyPosition[i].enemyMoveDelayStep += 1;
    if (enemyPosition[i].enemyMoveDelayStep < ENEMY_MOVE_DELAY) continue;
    enemyPosition[i].enemyMoveDelayStep = 0;

    enemyPosition[i].oldEnemyPosition[0] = enemyPosition[i].enemyPosition[0];
    enemyPosition[i].oldEnemyPosition[1] = enemyPosition[i].enemyPosition[1];

    if (enemyPosition[i].hasLeftGate) {
      // which straight directon is the player closest to
      xDistance = pos->rabbitPosition[0] - enemyPosition[i].enemyPosition[0];
      yDistance = pos->rabbitPosition[1] - enemyPosition[i].enemyPosition[1];

      if (abs(xDistance) > abs(yDistance)) {
        enemyPosition[i].enemyPosition[0] += SIGN(xDistance) * ENEMY_MOVE_SPEED;
      } else {
        enemyPosition[i].enemyPosition[1] += SIGN(yDistance) * ENEMY_MOVE_SPEED;
      }
    } else {
      switch (enemyPosition[i].gateExitedFrom) {
        // top
        case 0:
          xDistance = 0;
          yDistance = ENEMY_MOVE_SPEED;
          break;
        // right
        case 1:
          xDistance = -ENEMY_MOVE_SPEED;
          yDistance = 0;
          break;
        // bottom
        case 2:
          xDistance = 0;
          yDistance = -ENEMY_MOVE_SPEED;
          break;
        // left
        case 3:
          xDistance = ENEMY_MOVE_SPEED;
          yDistance = 0;
          break;
      }

      enemyPosition[i].enemyPosition[0] += xDistance;
      enemyPosition[i].enemyPosition[1] += yDistance;

      switch (enemyPosition[i].gateExitedFrom) {
        case 0:
          hasExitedGate = (
            enemyPosition[i].enemyPosition[1] > spawnPointRanges[0].top + spawnPointRanges[0].height
          );
          break;
        case 1:
          hasExitedGate = (
            enemyPosition[i].enemyPosition[0] < spawnPointRanges[1].left
          );
          break;
        case 2:
          hasExitedGate = (
            enemyPosition[i].enemyPosition[1] < spawnPointRanges[2].top
          );
          break;
        case 3:
          hasExitedGate = (
            enemyPosition[i].enemyPosition[0] > spawnPointRanges[3].left + spawnPointRanges[3].width
          );
          break;
      }

      enemyPosition[i].hasLeftGate = hasExitedGate;
    }
  }
}

void handleRabbitMovement(
  struct RabbitPosition *pos,
  struct KeyboardKeydownState *keyboardKeydownState
) {
  int i;

  if (keyboardKeydownState->KEY_W) {
    pos->rabbitVelocity[1] -= RABBIT_MOTION_ACCELERATION;
    if (pos->rabbitVelocity[1] < -RABBIT_MOTION_MAX_SPEED) {
      pos->rabbitVelocity[1] = -RABBIT_MOTION_MAX_SPEED;
    }
  }
  if (keyboardKeydownState->KEY_S) {
    pos->rabbitVelocity[1] += RABBIT_MOTION_ACCELERATION;
    if (pos->rabbitVelocity[1] > RABBIT_MOTION_MAX_SPEED) {
      pos->rabbitVelocity[1] = RABBIT_MOTION_MAX_SPEED;
    }
  }
  if (keyboardKeydownState->KEY_A) {
    pos->rabbitVelocity[0] -= RABBIT_MOTION_ACCELERATION;
    if (pos->rabbitVelocity[0] < -RABBIT_MOTION_MAX_SPEED) {
      pos->rabbitVelocity[0] = -RABBIT_MOTION_MAX_SPEED;
    }
  }
  if (keyboardKeydownState->KEY_D) {
    pos->rabbitVelocity[0] += RABBIT_MOTION_ACCELERATION;
    if (pos->rabbitVelocity[0] > RABBIT_MOTION_MAX_SPEED) {
      pos->rabbitVelocity[0] = RABBIT_MOTION_MAX_SPEED;
    }
  }

  for (i = 0; i < 2; ++i) {
    pos->oldRabbitPosition[i] = pos->rabbitPosition[i];
    pos->rabbitPosition[i] += (pos->rabbitVelocity[i] / RABBIT_MOTION_VELOCITY_DECAY);

    if (pos->rabbitPosition[i] < pos->rabbitLimits[0][i]) {
      pos->rabbitPosition[i] = pos->rabbitLimits[0][i];
    }
    if (pos->rabbitPosition[i] >= pos->rabbitLimits[1][i]) {
      pos->rabbitPosition[i] = pos->rabbitLimits[1][i];
    }

    if (pos->rabbitVelocity[i] < 0) {
      pos->rabbitVelocity[i] += RABBIT_MOTION_DRAG;
      if (pos->rabbitVelocity[i] > 0) pos->rabbitVelocity[i] = 0;
    }
    if (pos->rabbitVelocity[i] > 0) {
      pos->rabbitVelocity[i] -= RABBIT_MOTION_DRAG;
      if (pos->rabbitVelocity[i] < 0) pos->rabbitVelocity[i] = 0;
    }
  }
}