kaltaquise-gamification/kidney_lab/js/conveyor.js

/**
 * conveyor.js
 * Left conveyor belts (3×, goods travel → right).
 * Right conveyor belt (1×, medication travels ← left).
 * Pure logic — no rendering, no DOM.
 */

/* ────────────────────────────── Good ──────────────────────────── */

const GoodState = Object.freeze({
  SLIDING:   'sliding',    // moving along belt
  READY:     'ready',      // at belt's right end, waiting for pickup
  COLLECTED: 'collected',  // grabbed by player
  DROPPED:   'dropped',    // fell — penalty already applied
});

class Good {
  constructor(beltRow, isSpecial) {
    this.id        = Good._nextId++;
    this.beltRow   = beltRow;
    this.isSpecial = isSpecial;
    this.x         = SETTINGS.LEFT_ZONE_START + SETTINGS.GOOD_SIZE / 2;
    this.y         = SETTINGS.BELT_ROWS[beltRow];
    this.state     = GoodState.SLIDING;
    this.waitTimer = 0;
  }
}
Good._nextId = 0;

/* ────────────────────────── LeftConveyorSystem ─────────────────── */

class LeftConveyorSystem {
  constructor() {
    // Belt strip animation offset (px, wraps at 40)
    this.animOffset = 0;

    // Per-belt state: goods array + countdown to next spawn
    this.belts = SETTINGS.BELT_INIT_OFFSETS.map(offset => ({
      goods:      [],
      spawnTimer: offset,
    }));
  }

  _randomSpawnTime() {
    return SETTINGS.BELT_MIN_SPAWN
      + Math.random() * (SETTINGS.BELT_MAX_SPAWN - SETTINGS.BELT_MIN_SPAWN);
  }

  /**
   * Update all belts.
   * @param {number}   dt      – delta time in ms
   * @param {function} onDrop  – called with (good) when a good drops off
   */
  update(dt, onDrop) {
    this.animOffset = (this.animOffset + SETTINGS.LEFT_BELT_SPEED * dt / 1000) % 40;

    this.belts.forEach((belt, row) => {
      // ── Spawn ──
      belt.spawnTimer -= dt;
      if (belt.spawnTimer <= 0) {
        belt.spawnTimer = this._randomSpawnTime();
        const isSpecial = Math.random() < SETTINGS.SPECIAL_GOOD_CHANCE;
        belt.goods.push(new Good(row, isSpecial));
      }

      // ── Move & age goods ──
      belt.goods.forEach(good => {
        if (good.state === GoodState.SLIDING) {
          good.x += SETTINGS.LEFT_BELT_SPEED * dt / 1000;
          const pickupX = SETTINGS.LEFT_ZONE_END - SETTINGS.GOOD_SIZE * 0.5;
          if (good.x >= pickupX) {
            good.x = pickupX;
            good.state     = GoodState.READY;
            good.waitTimer = SETTINGS.GOOD_WAIT_TIME;
          }
        } else if (good.state === GoodState.READY) {
          good.waitTimer -= dt;
          if (good.waitTimer <= 0) {
            good.state = GoodState.DROPPED;
            onDrop(good);
          }
        }
      });

      // ── Prune finished goods ──
      belt.goods = belt.goods.filter(
        g => g.state === GoodState.SLIDING || g.state === GoodState.READY
      );
    });
  }

  /**
   * Try to collect the READY good on the given row.
   * Returns the Good object on success, null otherwise.
   */
  tryCollect(row) {
    const belt = this.belts[row];
    const good = belt.goods.find(g => g.state === GoodState.READY);
    if (!good) return null;
    good.state = GoodState.COLLECTED;
    return good;
  }

  /** True if belt[row] has a READY good waiting at the pickup point. */
  hasReadyGood(row) {
    return this.belts[row].goods.some(g => g.state === GoodState.READY);
  }

  /** All goods in SLIDING or READY state across all belts (for rendering). */
  allGoods() {
    return this.belts.flatMap(b => b.goods);
  }
}

/* ─────────────────────── Medication (right belt) ──────────────── */

const MedState = Object.freeze({
  ON_BELT:  'on_belt',  // sliding left
  READY:    'ready',    // at left end, waiting for player
  PICKED:   'picked',   // player has it
  EXPIRED:  'expired',  // timed out while waiting
});

class Medication {
  constructor() {
    this.id        = Medication._nextId++;
    // Start at right edge of right zone
    this.x         = SETTINGS.RIGHT_ZONE_END - SETTINGS.GOOD_SIZE;
    this.y         = SETTINGS.BELT_ROWS[1];   // always middle row
    this.state     = MedState.ON_BELT;
    this.waitTimer = 0;
  }
}
Medication._nextId = 0;

/* ────────────────────────── RightConveyorSystem ────────────────── */

class RightConveyorSystem {
  constructor() {
    this.animOffset  = 0;
    this.medications = [];
  }

  addMedication() {
    this.medications.push(new Medication());
  }

  /**
   * Update right belt medications.
   * @param {number} dt – delta time ms
   */
  update(dt) {
    this.animOffset = (this.animOffset + SETTINGS.RIGHT_BELT_SPEED * dt / 1000) % 40;

    this.medications.forEach(med => {
      if (med.state === MedState.ON_BELT) {
        med.x -= SETTINGS.RIGHT_BELT_SPEED * dt / 1000;
        const pickupX = SETTINGS.RIGHT_ZONE_START + SETTINGS.GOOD_SIZE * 0.5;
        if (med.x <= pickupX) {
          med.x         = pickupX;
          med.state     = MedState.READY;
          med.waitTimer = SETTINGS.MED_WAIT_TIME;
        }
      } else if (med.state === MedState.READY) {
        med.waitTimer -= dt;
        if (med.waitTimer <= 0) {
          med.state = MedState.EXPIRED;
        }
      }
    });

    // Prune expired / picked medications
    this.medications = this.medications.filter(
      m => m.state === MedState.ON_BELT || m.state === MedState.READY
    );
  }

  /** True if there is a READY medication at the pickup point (row 1 left end). */
  hasReadyMedication() {
    return this.medications.some(m => m.state === MedState.READY);
  }

  /**
   * Try to pick up the READY medication.
   * Returns true on success.
   */
  tryPickup() {
    const med = this.medications.find(m => m.state === MedState.READY);
    if (!med) return false;
    med.state = MedState.PICKED;
    return true;
  }

  /** Visible medications for rendering (ON_BELT and READY). */
  visibleMedications() {
    return this.medications.filter(
      m => m.state === MedState.ON_BELT || m.state === MedState.READY
    );
  }
}