#include "Arduino.h"

// ============================================================================
// STUDENT CONFIGURATION
// ============================================================================
#define STUDENT_NUMBER 2248578

// ============================================================================
// SYSTEM PARAMETERS - AUTO-GENERATED FROM STUDENT_NUMBER
// DO NOT MODIFY MANUALLY - Computed by generateParameters()
// ============================================================================
struct SystemParams {
  float v1, v2, v3;                  // Conveyor speeds (cm/s)
  float d0, d1, d2, d3, d4;          // Conv1 distances from obstruction sensor (cm)
  float d5, d6;                      // Conv2/Conv3 total lengths (cm)
  float L_min, L_max, L_threshold;   // Length criteria (cm)
  float W_min, W_max, W_threshold;   // Weight criteria (g)
  float T_gate;                      // Gate mechanical response time (ms)
  int C1, C2, C3;                    // Area capacities (products)
  int productInterval;               // Product loading interval (ms)
};

SystemParams sp;

#define DIST_LEAD   10.0f   // Fixed: entry point to obstruction sensor (cm)
#define DEBUG_PIN   12

// ============================================================================
// TYPE DEFINITIONS
// ============================================================================
enum class ProductEventType {
  OBSTRUCTION_SENSOR_RISE,
  OBSTRUCTION_SENSOR_FALL,
  G2_CHECK,                       // Size gate check
  WEIGHT_SENSOR_ENTER_WINDOW,
  WEIGHT_SENSOR_EXIT_WINDOW,
  G3_CHECK,                       // Weight gate check
  BARCODE_SENSOR_ENTER_WINDOW,
  BARCODE_SENSOR_EXIT_WINDOW,
  G4_CHECK,                       // Routing gate check
  ARRIVE_DESTINATION,             // Product reaches final area
  FINISH
};

struct Product {
  float length;       // Product length (cm)
  float weight;       // Product weight (g)
  int   barcodeID;    // Barcode tracking number
};

struct ProductEvent {
  uint64_t         triggerTimeMicros;
  ProductEventType eventType;
  int              gateExpected;       // For gate checks: expected gate state (0 or 1)
  int              destArea;           // For ARRIVE: destination area (0=A1, 1=A2, 2=A3)
};

struct ProductScheduler {
  Product product;
  ProductEvent events[16];
  int totalEvents;
  int currentEventIndex;
  int debugPin;
  hw_timer_t* timerHandle;
};

// Gate error counters: [0]=G2, [1]=G3, [2]=G4
// Check these to verify your gate control is correct (should all be 0)
volatile int errorGateCNT[3] = {0};

// Ground truth area counts (maintained by simulator)
volatile int simAreaCount[3] = {0, 0, 0};  // Area1, Area2, Area3

extern void startSimulator(void);

// ============================================================================
// PARAMETER GENERATION (deterministic from student number)
// ============================================================================
static uint32_t paramHash(uint32_t seed, uint32_t idx) {
  uint32_t v = seed * 2654435761u + idx * 2246822519u;
  v ^= v >> 16;
  v *= 0x45d9f3bu;
  v ^= v >> 16;
  return v;
}

static float paramRangeF(uint32_t seed, uint32_t idx, float lo, float hi) {
  return lo + (float)(paramHash(seed, idx) % 10001u) / 10000.0f * (hi - lo);
}

static int paramRangeI(uint32_t seed, uint32_t idx, int lo, int hi) {
  return lo + (int)(paramHash(seed, idx) % (uint32_t)(hi - lo + 1));
}

void generateParameters(uint32_t sn) {
  if (sn == 0) {
    // Default parameters (no student number set)
    sp.v1 = 100.0f;  sp.v2 = 120.0f;  sp.v3 = 80.0f;
    sp.d0 = 15.0f;   sp.d1 = 25.0f;   sp.d2 = 35.0f;
    sp.d3 = 45.0f;   sp.d4 = 55.0f;
    sp.d5 = 40.0f;   sp.d6 = 40.0f;
    sp.L_min = 4.5f;  sp.L_max = 5.5f;  sp.L_threshold = 5.0f;
    sp.W_min = 90.0f;  sp.W_max = 110.0f;  sp.W_threshold = 100.0f;
    sp.T_gate = 3.0f;
    sp.C1 = 5;  sp.C2 = 10;  sp.C3 = 10;
    sp.productInterval = 500;
    return;
  }

  sp.v1 = paramRangeF(sn, 1, 80.0f, 120.0f);
  sp.v2 = paramRangeF(sn, 2, 100.0f, 150.0f);
  sp.v3 = paramRangeF(sn, 3, 60.0f, 100.0f);

  sp.d0 = paramRangeF(sn, 4, 12.0f, 20.0f);
  sp.d1 = sp.d0 + paramRangeF(sn, 5, 8.0f, 15.0f);
  sp.d2 = sp.d1 + paramRangeF(sn, 6, 8.0f, 15.0f);
  sp.d3 = sp.d2 + paramRangeF(sn, 7, 8.0f, 15.0f);
  sp.d4 = sp.d3 + paramRangeF(sn, 8, 8.0f, 15.0f);
  sp.d5 = paramRangeF(sn, 9, 30.0f, 50.0f);
  sp.d6 = paramRangeF(sn, 10, 30.0f, 50.0f);

  sp.L_min = paramRangeF(sn, 11, 4.0f, 5.0f);
  sp.L_max = sp.L_min + paramRangeF(sn, 12, 0.8f, 1.5f);
  sp.L_threshold = (sp.L_min + sp.L_max) / 2.0f;

  sp.W_min = paramRangeF(sn, 13, 80.0f, 100.0f);
  sp.W_max = sp.W_min + paramRangeF(sn, 14, 15.0f, 30.0f);
  sp.W_threshold = (sp.W_min + sp.W_max) / 2.0f;

  sp.T_gate = paramRangeF(sn, 15, 2.0f, 5.0f);

  sp.C1 = paramRangeI(sn, 16, 3, 8);
  sp.C2 = paramRangeI(sn, 17, 8, 15);
  sp.C3 = paramRangeI(sn, 18, 8, 15);

  sp.productInterval = paramRangeI(sn, 19, 400, 600);
}

void printParameters() {
  Serial.println("========== SmartSort System Parameters ==========");
  Serial.printf("Student Number: %u\n", (unsigned)STUDENT_NUMBER);
  Serial.println("----- Conveyor Speeds -----");
  Serial.printf("  v1 (Conv1): %.1f cm/s\n", sp.v1);
  Serial.printf("  v2 (Conv2): %.1f cm/s\n", sp.v2);
  Serial.printf("  v3 (Conv3): %.1f cm/s\n", sp.v3);
  Serial.println("----- Distances (from obstruction sensor, cm) -----");
  Serial.printf("  d0 (to G2):      %.1f\n", sp.d0);
  Serial.printf("  d1 (to Weight):  %.1f\n", sp.d1);
  Serial.printf("  d2 (to G3):      %.1f\n", sp.d2);
  Serial.printf("  d3 (to Barcode): %.1f\n", sp.d3);
  Serial.printf("  d4 (to G4):      %.1f\n", sp.d4);
  Serial.printf("  d5 (Conv2 len):  %.1f\n", sp.d5);
  Serial.printf("  d6 (Conv3 len):  %.1f\n", sp.d6);
  Serial.println("----- Length Criteria (cm) -----");
  Serial.printf("  L_min=%.2f  L_max=%.2f  L_threshold=%.2f\n", sp.L_min, sp.L_max, sp.L_threshold);
  Serial.println("----- Weight Criteria (g) -----");
  Serial.printf("  W_min=%.2f  W_max=%.2f  W_threshold=%.2f\n", sp.W_min, sp.W_max, sp.W_threshold);
  Serial.println("----- Timing & Capacity -----");
  Serial.printf("  T_gate=%.1f ms  Interval=%d ms\n", sp.T_gate, sp.productInterval);
  Serial.printf("  C1=%d  C2=%d  C3=%d\n", sp.C1, sp.C2, sp.C3);
  Serial.println("=================================================");
}

// ============================================================================
// PRODUCT ARRAY - Generated based on parameters to cover all sorting paths
// Students may modify this array for additional testing
// ============================================================================
#define MAX_TEST_PRODUCTS 20
Product productArray[MAX_TEST_PRODUCTS];
int numProducts = 0;

void generateProductArray() {
  int idx = 0;
  float Lmid = (sp.L_min + sp.L_max) / 2.0f;
  float Wmid = (sp.W_min + sp.W_max) / 2.0f;

  // Category 1: Size abnormal (too short) -> Area 1 via G2
  productArray[idx++] = {sp.L_min - 0.5f, Wmid, 1001};
  productArray[idx++] = {sp.L_min - 1.0f, Wmid + 3.0f, 1002};

  // Category 2: Size abnormal (too long) -> Area 1 via G2
  productArray[idx++] = {sp.L_max + 0.5f, Wmid, 1003};
  productArray[idx++] = {sp.L_max + 0.8f, Wmid - 2.0f, 1004};

  // Category 3: Normal size, weight too light -> Area 1 via G3
  productArray[idx++] = {Lmid, sp.W_min - 5.0f, 1005};
  productArray[idx++] = {sp.L_min + 0.1f, sp.W_min - 3.0f, 1006};

  // Category 4: Normal size, weight too heavy -> Area 1 via G3
  productArray[idx++] = {Lmid, sp.W_max + 5.0f, 1007};
  productArray[idx++] = {sp.L_max - 0.1f, sp.W_max + 3.0f, 1008};

  // Category 5: Normal, small & light -> Area 2 (L<=Lthresh AND W<=Wthresh)
  productArray[idx++] = {sp.L_min + 0.1f, sp.W_min + 1.0f, 1009};
  productArray[idx++] = {sp.L_threshold, sp.W_threshold, 1010};       // Edge case: exactly at threshold
  productArray[idx++] = {sp.L_threshold - 0.1f, sp.W_threshold - 1.0f, 1011};

  // Category 6: Normal, large or heavy -> Area 3
  productArray[idx++] = {sp.L_threshold + 0.1f, sp.W_threshold - 1.0f, 1012};
  productArray[idx++] = {sp.L_min + 0.2f, sp.W_threshold + 1.0f, 1013};
  productArray[idx++] = {sp.L_max - 0.1f, sp.W_max - 1.0f, 1014};
  productArray[idx++] = {sp.L_threshold + 0.2f, sp.W_threshold + 2.0f, 1015};

  // Edge cases
  productArray[idx++] = {sp.L_min, sp.W_min, 1016};    // Exactly at min boundaries -> Area 2
  productArray[idx++] = {sp.L_max, sp.W_max, 1017};    // Exactly at max -> Area 3
  productArray[idx++] = {Lmid, Wmid, 1018};             // Center values -> Area 2

  numProducts = idx;
}

/*!!!!!!!!!!!!!!!!!!ANY CODE ABOVE THIS LINE SHOULD NOT BE MODIFIED BY STUDENTS!!!!!!!!!!!!!!!!!!!*/
/*=========================== INTERFACE BETWEEN SIMULATOR AND STUDENT CODE ============================*/

/*
   g_obstructionSensorPin outputs the physical signal of the obstruction sensor (for oscilloscope).
*/
#define g_obstructionSensorPin    32

/*
   Debug output pins for gate signals (for oscilloscope verification).
   The simulator does NOT read these - they are for your debugging only.
*/
#define gate2DebugPin             33
#define gate3DebugPin             27
#define gate4DebugPin             14

/*
   SHARED VARIABLES - DO NOT RENAME
   The simulator uses these to provide sensor data and check your gate controls.
*/
// ========== Simulator writes, students read ==========
volatile bool   g_obstructionSensor = false;  // Obstruction sensor state
volatile int    g_barcodeReader     = 0;       // Barcode reading (0=invalid/not in window)
volatile float  g_weightSensor      = 0.0f;    // Weight reading (0=invalid/not in window)

// ========== Students write, simulator reads ==========
// G1 (Intake): true=allow products in, false=block entry
volatile bool   g_gate1Ctrl = true;
// G2 (Size divert): false=let pass, true=activate pusher (divert to Area 1)
volatile bool   g_gate2Ctrl = false;
// G3 (Weight divert): false=let pass, true=activate pusher (divert to Area 1)
volatile bool   g_gate3Ctrl = false;
// G4 (Routing): false=route to Conv2/Area2, true=route to Conv3/Area3
volatile bool   g_gate4Ctrl = false;

/*================================= IMPLEMENT YOUR RTOS CODE BELOW ===================================*/


// ============================================================================
// CONSTANTS
// ============================================================================

#define LEN_EPS_CM             0.005f
#define WGT_EPS_G              0.005f

#define STATUS_HISTORY_SIZE    6
#define GATE_QUEUE_SIZE        32
#define ARRIVAL_QUEUE_SIZE     24


// ============================================================================
// ENUMS
// ============================================================================

typedef enum {
  STATE_NEW_PRODUCT = 0,
  STATE_LENGTH_READY,
  STATE_WAIT_WEIGHT,
  STATE_WEIGHT_READY,
  STATE_WAIT_BARCODE,
  STATE_BARCODE_READY,
  STATE_FINISHED,
  STATE_ABORTED
} ParcelState;

typedef enum {
  DEST_NONE = 0,
  DEST_A1   = 1,
  DEST_A2   = 2,
  DEST_A3   = 3
} Destination;

typedef enum {
  GATE_G2 = 2,
  GATE_G3 = 3,
  GATE_G4 = 4
} GateId;


// ============================================================================
// STRUCTURES
// ============================================================================

typedef struct {
  int64_t riseUs;
  int64_t fallUs;
} BeamEdges;

typedef struct {
  uint32_t sequenceId;
  uint32_t epoch;

  BeamEdges beam;

  ParcelState state;
  Destination destination;

  float lengthCm;
  float weightG;
  int barcode;

  int64_t g2CheckUs;
  int64_t g3CheckUs;
  int64_t g4CheckUs;
} ParcelContext;

typedef struct {
  uint32_t sequenceId;
  int barcode;
  float lengthCm;
  float weightG;
  Destination destination;
} RecentParcel;

typedef struct {
  int occupied[3];        // A1, A2, A3
  int travelling[3];      // A1, A2, A3

  float sumLengthAll;
  float sumWeightAll;
  int countAll;

  float sumLengthA2;
  float sumWeightA2;
  int countA2;

  float sumLengthA3;
  float sumWeightA3;
  int countA3;
} SortState;

typedef struct {
  GateId gate;
  bool stateRequired;
  int64_t onTimeUs;
  int64_t gateArrivalUs;
  int64_t offTimeUs;
  uint32_t epoch;
} GateJob;

typedef struct {
  GateId gate;
  QueueHandle_t queue;
} GateTaskParam;

typedef struct {
  uint32_t sequenceId;
  int barcode;
  float lengthCm;
  float weightG;
  Destination destination;
  int64_t arrivalTimeUs;
  uint32_t epoch;
} ArrivalJob;


// ============================================================================
// GLOBAL VARIABLES
// ============================================================================

static QueueHandle_t beamQueue = NULL;

static QueueHandle_t gateQueueG2 = NULL;
static QueueHandle_t gateQueueG3 = NULL;
static QueueHandle_t gateQueueG4 = NULL;

static QueueHandle_t arrivalQueue = NULL;
static SemaphoreHandle_t stateMutex = NULL;

static volatile BeamEdges activeBeam = {0, 0};

static SortState sortState = {0};

static RecentParcel recentList[STATUS_HISTORY_SIZE];
static int recentWriteIndex = 0;
static int recentCount = 0;

static volatile uint32_t nextSequenceId = 1;
static volatile uint32_t currentEpoch = 1;

static volatile bool emergencyStop = false;
static volatile bool intakeClosedByCapacity = false;
static volatile bool capacityMessagePrinted = false;
static volatile int capacityBlockedArea = 0;

static volatile int64_t g2LastAppliedArrivalUs = 0;
static volatile int64_t g3LastAppliedArrivalUs = 0;
static volatile int64_t g4LastAppliedArrivalUs = 0;

static volatile int64_t g2LastReleaseUs = 0;
static volatile int64_t g3LastReleaseUs = 0;
static volatile int64_t g4LastReleaseUs = 0;

static GateTaskParam gateParamG2;
static GateTaskParam gateParamG3;
static GateTaskParam gateParamG4;


// ============================================================================
// FORWARD DECLARATIONS
// ============================================================================

static int64_t travelUs(float distanceCm, float speedCmPerSec);
static bool epochValid(uint32_t epoch);
static void waitUntilUs(int64_t targetUs, uint32_t epoch);

static bool lengthOk(float lengthCm);
static bool weightOk(float weightG);
static bool qualifiesArea2(float lengthCm, float weightG);

static void updateG1CapacityControl();
static void reserveDestination(Destination dest);
static void completeDestinationArrival(const ArrivalJob *job);
static void addRecentRecord(const ArrivalJob *job);

static float readWeightTimed(int64_t centreUs, float lengthCm, uint32_t epoch);
static int readBarcodeTimed(int64_t centreUs, float lengthCm, uint32_t epoch);

static volatile bool* gateOutputPointer(GateId gate);
static volatile int64_t* gateLastAppliedPointer(GateId gate);
static volatile int64_t* gateLastReleasePointer(GateId gate);
static QueueHandle_t gateQueueFromId(GateId gate);

static void submitGateJob(GateId gate,
                          bool requiredState,
                          int64_t gateCheckUs,
                          float lengthCm,
                          uint32_t epoch);

static void submitArrivalJob(const ParcelContext *parcel, int64_t arrivalUs);

static void resetController();
static void clearDestinationAreas();

void parcelStateMachineTask(void *pvParameters);
void gateControlTask(void *pvParameters);
void arrivalManagerTask(void *pvParameters);
void productProcessingTask(void *pvParameters);
void backgroundTask(void *pvParameters);


// ============================================================================
// TIME HELPERS
// ============================================================================

static int64_t travelUs(float distanceCm, float speedCmPerSec) {
  if (speedCmPerSec <= 0.0f) {
    return 0;
  }

  return (int64_t)((distanceCm / speedCmPerSec) * 1000000.0f);
}

static bool epochValid(uint32_t epoch) {
  return epoch == currentEpoch;
}

static void waitUntilUs(int64_t targetUs, uint32_t epoch) {
  while (!emergencyStop && epochValid(epoch)) {
    int64_t nowUs = esp_timer_get_time();
    int64_t remainingUs = targetUs - nowUs;

    if (remainingUs <= 0) {
      return;
    }

    if (remainingUs > 4000) {
      int delayMs = (int)((remainingUs - 2000) / 1000);

      if (delayMs < 1) {
        delayMs = 1;
      }

      vTaskDelay(pdMS_TO_TICKS(delayMs));
    }
    else {
      delayMicroseconds((uint32_t)remainingUs);
      return;
    }
  }
}


// ============================================================================
// CLASSIFICATION HELPERS
// ============================================================================

static bool lengthOk(float lengthCm) {
  return (lengthCm >= (sp.L_min - LEN_EPS_CM) &&
          lengthCm <= (sp.L_max + LEN_EPS_CM));
}

static bool weightOk(float weightG) {
  return (weightG >= (sp.W_min - WGT_EPS_G) &&
          weightG <= (sp.W_max + WGT_EPS_G));
}

static bool qualifiesArea2(float lengthCm, float weightG) {
  return (lengthCm <= sp.L_threshold &&
          weightG <= sp.W_threshold);
}


// ============================================================================
// CAPACITY AND STATISTICS
// ============================================================================

static void updateG1CapacityControl() {
  if (stateMutex == NULL) {
    return;
  }

  if (sp.C1 <= 0 || sp.C2 <= 0 || sp.C3 <= 0) {
    g_gate1Ctrl = true;
    intakeClosedByCapacity = false;
    capacityMessagePrinted = false;
    capacityBlockedArea = 0;
    return;
  }

  xSemaphoreTake(stateMutex, portMAX_DELAY);

  int blockedArea = 0;

  if ((sortState.occupied[0] + sortState.travelling[0]) >= sp.C1) {
    blockedArea = 1;
  }
  else if ((sortState.occupied[1] + sortState.travelling[1]) >= sp.C2) {
    blockedArea = 2;
  }
  else if ((sortState.occupied[2] + sortState.travelling[2]) >= sp.C3) {
    blockedArea = 3;
  }

  if (emergencyStop) {
    g_gate1Ctrl = false;
  }
  else if (blockedArea != 0) {
    g_gate1Ctrl = false;
    intakeClosedByCapacity = true;
    capacityBlockedArea = blockedArea;
  }
  else {
    g_gate1Ctrl = true;
    intakeClosedByCapacity = false;
    capacityMessagePrinted = false;
    capacityBlockedArea = 0;
  }

  xSemaphoreGive(stateMutex);
}

static void reserveDestination(Destination dest) {
  int index = ((int)dest) - 1;

  if (index < 0 || index > 2 || stateMutex == NULL) {
    return;
  }

  xSemaphoreTake(stateMutex, portMAX_DELAY);
  sortState.travelling[index]++;
  xSemaphoreGive(stateMutex);

  updateG1CapacityControl();
}

static void addRecentRecord(const ArrivalJob *job) {
  if (job == NULL || stateMutex == NULL) {
    return;
  }

  xSemaphoreTake(stateMutex, portMAX_DELAY);

  recentList[recentWriteIndex].sequenceId = job->sequenceId;
  recentList[recentWriteIndex].barcode = job->barcode;
  recentList[recentWriteIndex].lengthCm = job->lengthCm;
  recentList[recentWriteIndex].weightG = job->weightG;
  recentList[recentWriteIndex].destination = job->destination;

  recentWriteIndex = (recentWriteIndex + 1) % STATUS_HISTORY_SIZE;

  if (recentCount < STATUS_HISTORY_SIZE) {
    recentCount++;
  }

  xSemaphoreGive(stateMutex);
}

static void completeDestinationArrival(const ArrivalJob *job) {
  if (job == NULL || stateMutex == NULL) {
    return;
  }

  int index = ((int)job->destination) - 1;

  if (index < 0 || index > 2) {
    return;
  }

  xSemaphoreTake(stateMutex, portMAX_DELAY);

  if (sortState.travelling[index] > 0) {
    sortState.travelling[index]--;
  }

  sortState.occupied[index]++;

  sortState.sumLengthAll += job->lengthCm;
  sortState.sumWeightAll += job->weightG;
  sortState.countAll++;

  if (job->destination == DEST_A2) {
    sortState.sumLengthA2 += job->lengthCm;
    sortState.sumWeightA2 += job->weightG;
    sortState.countA2++;
  }
  else if (job->destination == DEST_A3) {
    sortState.sumLengthA3 += job->lengthCm;
    sortState.sumWeightA3 += job->weightG;
    sortState.countA3++;
  }

  xSemaphoreGive(stateMutex);

  addRecentRecord(job);
  updateG1CapacityControl();
}


// ============================================================================
// SENSOR TIMING
// ============================================================================

static float readWeightTimed(int64_t centreUs, float lengthCm, uint32_t epoch) {
  float weight = 0.0f;

  int64_t halfWindowUs = travelUs(lengthCm * 0.10f, sp.v1);
  int64_t startUs = centreUs - halfWindowUs + 300;
  int64_t endUs   = centreUs + halfWindowUs - 300;

  waitUntilUs(startUs, epoch);

  while (!emergencyStop && epochValid(epoch) && esp_timer_get_time() <= endUs) {
    if (g_weightSensor > 0.0f) {
      weight = g_weightSensor;
      break;
    }

    delayMicroseconds(300);
  }

  return weight;
}

static int readBarcodeTimed(int64_t centreUs, float lengthCm, uint32_t epoch) {
  int code = 0;

  int64_t halfWindowUs = travelUs(lengthCm * 0.10f, sp.v1);
  int64_t startUs = centreUs - halfWindowUs + 300;
  int64_t endUs   = centreUs + halfWindowUs - 300;

  waitUntilUs(startUs, epoch);

  while (!emergencyStop && epochValid(epoch) && esp_timer_get_time() <= endUs) {
    if (g_barcodeReader != 0) {
      code = g_barcodeReader;
      break;
    }

    delayMicroseconds(300);
  }

  return code;
}


// ============================================================================
// SERIALIZED PER-GATE CONTROL
// ============================================================================

static volatile bool* gateOutputPointer(GateId gate) {
  switch (gate) {
    case GATE_G2:
      return &g_gate2Ctrl;

    case GATE_G3:
      return &g_gate3Ctrl;

    case GATE_G4:
      return &g_gate4Ctrl;

    default:
      return NULL;
  }
}

static volatile int64_t* gateLastAppliedPointer(GateId gate) {
  switch (gate) {
    case GATE_G2:
      return &g2LastAppliedArrivalUs;

    case GATE_G3:
      return &g3LastAppliedArrivalUs;

    case GATE_G4:
      return &g4LastAppliedArrivalUs;

    default:
      return NULL;
  }
}

static volatile int64_t* gateLastReleasePointer(GateId gate) {
  switch (gate) {
    case GATE_G2:
      return &g2LastReleaseUs;

    case GATE_G3:
      return &g3LastReleaseUs;

    case GATE_G4:
      return &g4LastReleaseUs;

    default:
      return NULL;
  }
}

static QueueHandle_t gateQueueFromId(GateId gate) {
  switch (gate) {
    case GATE_G2:
      return gateQueueG2;

    case GATE_G3:
      return gateQueueG3;

    case GATE_G4:
      return gateQueueG4;

    default:
      return NULL;
  }
}

static void submitGateJob(GateId gate,
                          bool requiredState,
                          int64_t gateCheckUs,
                          float lengthCm,
                          uint32_t epoch) {
  if (!epochValid(epoch)) {
    return;
  }

  QueueHandle_t q = gateQueueFromId(gate);

  if (q == NULL) {
    return;
  }

  GateJob job;

  int64_t leadUs = (int64_t)(sp.T_gate * 1000.0f);

  job.gate = gate;
  job.stateRequired = requiredState;

  // Product front edge reaches the gate at gateCheckUs.
  job.gateArrivalUs = gateCheckUs;

  // Gate must start moving before the product reaches the gate.
  job.onTimeUs = gateCheckUs - leadUs;

  // Product clears the gate after its own length has travelled past the gate.
  job.offTimeUs = gateCheckUs + travelUs(lengthCm, sp.v1);

  job.epoch = epoch;

  int64_t nowUs = esp_timer_get_time();

  if (job.onTimeUs < nowUs) {
    job.onTimeUs = nowUs;
  }

  xQueueSend(q, &job, pdMS_TO_TICKS(10));
}

void gateControlTask(void *pvParameters) {
  GateTaskParam *param = (GateTaskParam *)pvParameters;

  if (param == NULL || param->queue == NULL) {
    vTaskDelete(NULL);
    return;
  }

  GateJob job;

  while (true) {
    if (xQueueReceive(param->queue, &job, portMAX_DELAY) != pdTRUE) {
      continue;
    }

    if (emergencyStop || !epochValid(job.epoch)) {
      continue;
    }

    volatile bool *gateSignal = gateOutputPointer(job.gate);
    volatile int64_t *lastAppliedArrival = gateLastAppliedPointer(job.gate);
    volatile int64_t *lastRelease = gateLastReleasePointer(job.gate);

    if (gateSignal == NULL ||
        lastAppliedArrival == NULL ||
        lastRelease == NULL) {
      continue;
    }

    int64_t activationTimeUs = job.onTimeUs;

    if (activationTimeUs < *lastRelease) {
      activationTimeUs = *lastRelease;
    }

    waitUntilUs(activationTimeUs, job.epoch);

    if (emergencyStop || !epochValid(job.epoch)) {
      continue;
    }

    if (job.gateArrivalUs >= *lastAppliedArrival) {
      *lastAppliedArrival = job.gateArrivalUs;
      *gateSignal = job.stateRequired;
    }

    int64_t releaseTimeUs = job.offTimeUs;

    if (releaseTimeUs < activationTimeUs) {
      releaseTimeUs = activationTimeUs;
    }

    waitUntilUs(releaseTimeUs, job.epoch);

    if (emergencyStop || !epochValid(job.epoch)) {
      continue;
    }

    if (job.gateArrivalUs == *lastAppliedArrival) {
      *lastRelease = releaseTimeUs;
    }
  }
}


// ============================================================================
// ARRIVAL TRACKING ON CORE 1
// ============================================================================

static void submitArrivalJob(const ParcelContext *parcel, int64_t arrivalUs) {
  if (parcel == NULL || arrivalQueue == NULL || !epochValid(parcel->epoch)) {
    return;
  }

  ArrivalJob job;

  job.sequenceId = parcel->sequenceId;
  job.barcode = parcel->barcode;
  job.lengthCm = parcel->lengthCm;
  job.weightG = parcel->weightG;
  job.destination = parcel->destination;
  job.arrivalTimeUs = arrivalUs;
  job.epoch = parcel->epoch;

  xQueueSend(arrivalQueue, &job, pdMS_TO_TICKS(10));
}

void arrivalManagerTask(void *pvParameters) {
  ArrivalJob job;

  while (true) {
    if (xQueueReceive(arrivalQueue, &job, portMAX_DELAY) == pdTRUE) {
      if (!epochValid(job.epoch) || emergencyStop) {
        continue;
      }

      waitUntilUs(job.arrivalTimeUs, job.epoch);

      if (epochValid(job.epoch) && !emergencyStop) {
        completeDestinationArrival(&job);
      }
    }
  }
}


// ============================================================================
// RESET AND CLEAR
// ============================================================================

static void resetController() {
  currentEpoch++;

  if (currentEpoch == 0) {
    currentEpoch = 1;
  }

  if (stateMutex != NULL) {
    xSemaphoreTake(stateMutex, portMAX_DELAY);

    memset(&sortState, 0, sizeof(sortState));
    memset(recentList, 0, sizeof(recentList));

    recentWriteIndex = 0;
    recentCount = 0;
    nextSequenceId = 1;

    xSemaphoreGive(stateMutex);
  }

  if (beamQueue != NULL) {
    xQueueReset(beamQueue);
  }

  if (gateQueueG2 != NULL) {
    xQueueReset(gateQueueG2);
  }

  if (gateQueueG3 != NULL) {
    xQueueReset(gateQueueG3);
  }

  if (gateQueueG4 != NULL) {
    xQueueReset(gateQueueG4);
  }

  if (arrivalQueue != NULL) {
    xQueueReset(arrivalQueue);
  }

  g2LastAppliedArrivalUs = 0;
  g3LastAppliedArrivalUs = 0;
  g4LastAppliedArrivalUs = 0;

  g2LastReleaseUs = 0;
  g3LastReleaseUs = 0;
  g4LastReleaseUs = 0;

  emergencyStop = false;
  intakeClosedByCapacity = false;
  capacityMessagePrinted = false;
  capacityBlockedArea = 0;

  g_gate1Ctrl = true;
  g_gate2Ctrl = false;
  g_gate3Ctrl = false;
  g_gate4Ctrl = false;
}

static void clearDestinationAreas() {
  if (stateMutex != NULL) {
    xSemaphoreTake(stateMutex, portMAX_DELAY);

    sortState.occupied[0] = 0;
    sortState.occupied[1] = 0;
    sortState.occupied[2] = 0;

    xSemaphoreGive(stateMutex);
  }

  intakeClosedByCapacity = false;
  capacityMessagePrinted = false;
  capacityBlockedArea = 0;

  updateG1CapacityControl();
}


// ============================================================================
// OBSTRUCTION SENSOR ISR
// ============================================================================

void IRAM_ATTR obstructionSensorInterrupt() {
  BaseType_t shouldYield = pdFALSE;

  if (g_obstructionSensor == true) {
    activeBeam.riseUs = esp_timer_get_time();
  }
  else {
    activeBeam.fallUs = esp_timer_get_time();

    if (beamQueue != NULL) {
      BeamEdges beamCopy;

      beamCopy.riseUs = activeBeam.riseUs;
      beamCopy.fallUs = activeBeam.fallUs;

      xQueueSendFromISR(beamQueue, &beamCopy, &shouldYield);
    }

    if (shouldYield) {
      portYIELD_FROM_ISR();
    }
  }
}


// ============================================================================
// PRODUCT DISPATCH TASK - CORE 0
// ============================================================================

void productProcessingTask(void *pvParameters) {
  BeamEdges beam;

  while (true) {
    if (xQueueReceive(beamQueue, &beam, portMAX_DELAY) == pdTRUE) {
      if (emergencyStop) {
        continue;
      }

      ParcelContext *parcel =
        (ParcelContext *)pvPortMalloc(sizeof(ParcelContext));

      if (parcel == NULL) {
        continue;
      }

      memset(parcel, 0, sizeof(ParcelContext));

      parcel->sequenceId = nextSequenceId++;
      parcel->epoch = currentEpoch;
      parcel->beam = beam;
      parcel->state = STATE_NEW_PRODUCT;
      parcel->destination = DEST_NONE;
      parcel->barcode = 0;
      parcel->weightG = 0.0f;

      BaseType_t created = xTaskCreatePinnedToCore(
                             parcelStateMachineTask,
                             "ParcelFSM",
                             4096,
                             parcel,
                             8,
                             NULL,
                             0
                           );

      if (created != pdPASS) {
        vPortFree(parcel);
      }
    }
  }
}


// ============================================================================
// PARCEL STATE MACHINE TASK - CORE 0
// ============================================================================

void parcelStateMachineTask(void *pvParameters) {
  ParcelContext *parcel = (ParcelContext *)pvParameters;

  if (parcel == NULL) {
    vTaskDelete(NULL);
    return;
  }

  while (!emergencyStop && epochValid(parcel->epoch)) {
    switch (parcel->state) {

      case STATE_NEW_PRODUCT: {
          int64_t blockedUs = parcel->beam.fallUs - parcel->beam.riseUs;

          if (blockedUs <= 0) {
            parcel->state = STATE_ABORTED;
            break;
          }

          parcel->lengthCm = (float)blockedUs * sp.v1 / 1000000.0f;

          parcel->g2CheckUs = parcel->beam.riseUs + travelUs(sp.d0, sp.v1);
          parcel->g3CheckUs = parcel->beam.riseUs + travelUs(sp.d2, sp.v1);
          parcel->g4CheckUs = parcel->beam.riseUs + travelUs(sp.d4, sp.v1);

          parcel->state = STATE_LENGTH_READY;
          break;
        }

      case STATE_LENGTH_READY: {
          if (!lengthOk(parcel->lengthCm)) {
            parcel->destination = DEST_A1;
            parcel->weightG = 0.0f;
            parcel->barcode = 0;

            reserveDestination(DEST_A1);

            submitGateJob(GATE_G2,
                          true,
                          parcel->g2CheckUs,
                          parcel->lengthCm,
                          parcel->epoch);

            submitArrivalJob(parcel,
                             parcel->g2CheckUs + travelUs(parcel->lengthCm, sp.v1));

            parcel->state = STATE_FINISHED;
          }
          else {
            submitGateJob(GATE_G2,
                          false,
                          parcel->g2CheckUs,
                          parcel->lengthCm,
                          parcel->epoch);

            parcel->state = STATE_WAIT_WEIGHT;
          }

          break;
        }

      case STATE_WAIT_WEIGHT: {
          float centreDistance = sp.d1 - (parcel->lengthCm / 2.0f);

          if (centreDistance < 0.0f) {
            centreDistance = 0.0f;
          }

          int64_t centreUs =
            parcel->beam.fallUs + travelUs(centreDistance, sp.v1);

          parcel->weightG =
            readWeightTimed(centreUs, parcel->lengthCm, parcel->epoch);

          parcel->state = STATE_WEIGHT_READY;
          break;
        }

      case STATE_WEIGHT_READY: {
          if (!weightOk(parcel->weightG)) {
            parcel->destination = DEST_A1;
            parcel->barcode = 0;

            reserveDestination(DEST_A1);

            submitGateJob(GATE_G3,
                          true,
                          parcel->g3CheckUs,
                          parcel->lengthCm,
                          parcel->epoch);

            submitArrivalJob(parcel,
                             parcel->g3CheckUs + travelUs(parcel->lengthCm, sp.v1));

            parcel->state = STATE_FINISHED;
          }
          else {
            submitGateJob(GATE_G3,
                          false,
                          parcel->g3CheckUs,
                          parcel->lengthCm,
                          parcel->epoch);

            parcel->state = STATE_WAIT_BARCODE;
          }

          break;
        }

      case STATE_WAIT_BARCODE: {
          float centreDistance = sp.d3 - (parcel->lengthCm / 2.0f);

          if (centreDistance < 0.0f) {
            centreDistance = 0.0f;
          }

          int64_t centreUs =
            parcel->beam.fallUs + travelUs(centreDistance, sp.v1);

          parcel->barcode =
            readBarcodeTimed(centreUs, parcel->lengthCm, parcel->epoch);

          parcel->state = STATE_BARCODE_READY;
          break;
        }

      case STATE_BARCODE_READY: {
          if (qualifiesArea2(parcel->lengthCm, parcel->weightG)) {
            parcel->destination = DEST_A2;

            reserveDestination(DEST_A2);

            submitGateJob(GATE_G4,
                          false,
                          parcel->g4CheckUs,
                          parcel->lengthCm,
                          parcel->epoch);

            int64_t arrivalUs =
              parcel->g4CheckUs + travelUs(sp.d5, sp.v2);

            submitArrivalJob(parcel, arrivalUs);
          }
          else {
            parcel->destination = DEST_A3;

            reserveDestination(DEST_A3);

            submitGateJob(GATE_G4,
                          true,
                          parcel->g4CheckUs,
                          parcel->lengthCm,
                          parcel->epoch);

            int64_t arrivalUs =
              parcel->g4CheckUs + travelUs(sp.d6, sp.v3);

            submitArrivalJob(parcel, arrivalUs);
          }

          parcel->state = STATE_FINISHED;
          break;
        }

      case STATE_FINISHED:
      case STATE_ABORTED:
      default:
        vPortFree(parcel);
        vTaskDelete(NULL);
        return;
    }
  }

  vPortFree(parcel);
  vTaskDelete(NULL);
}


// ============================================================================
// BACKGROUND TASK - CORE 1
// ============================================================================

void backgroundTask(void *pvParameters) {
  TickType_t lastWake = xTaskGetTickCount();

  while (true) {
    while (Serial.available() > 0) {
      String cmd = Serial.readStringUntil('\n');
      cmd.trim();

      if (cmd == "reset") {
        resetController();
      }
      else if (cmd == "clear") {
        clearDestinationAreas();
      }
      else if (cmd == "emergency") {
        emergencyStop = true;

        g_gate1Ctrl = false;
        g_gate2Ctrl = false;
        g_gate3Ctrl = false;
        g_gate4Ctrl = false;

        Serial.println("EMERGENCY: System halted");
      }
      else if (cmd == "stat") {
        float Lavg = 0.0f;
        float Wavg = 0.0f;
        float L2avg = 0.0f;
        float W2avg = 0.0f;
        float L3avg = 0.0f;
        float W3avg = 0.0f;

        if (stateMutex != NULL) {
          xSemaphoreTake(stateMutex, portMAX_DELAY);

          if (sortState.countAll > 0) {
            Lavg = sortState.sumLengthAll / sortState.countAll;
            Wavg = sortState.sumWeightAll / sortState.countAll;
          }

          if (sortState.countA2 > 0) {
            L2avg = sortState.sumLengthA2 / sortState.countA2;
            W2avg = sortState.sumWeightA2 / sortState.countA2;
          }

          if (sortState.countA3 > 0) {
            L3avg = sortState.sumLengthA3 / sortState.countA3;
            W3avg = sortState.sumWeightA3 / sortState.countA3;
          }

          xSemaphoreGive(stateMutex);
        }

        Serial.printf("sortSTAT: %.2f,%.2f,%.2f,%.2f,%.2f,%.2f\n",
                      Lavg, L2avg, L3avg, Wavg, W2avg, W3avg);
      }
    }

    updateG1CapacityControl();

    if (intakeClosedByCapacity && !capacityMessagePrinted) {
      Serial.printf("Area %d Capacity is full. Please clear the area, then type clear to continue.\n",
                    capacityBlockedArea);

      capacityMessagePrinted = true;
    }

    if (stateMutex != NULL) {
      xSemaphoreTake(stateMutex, portMAX_DELAY);
      if (emergencyStop || intakeClosedByCapacity) {}
      else {
        Serial.printf("sortRT: %03d,%03d,%03d",
                      sortState.occupied[0],
                      sortState.occupied[1],
                      sortState.occupied[2]);

        for (int i = 0; i < recentCount; i++) {
          int idx =
            (recentWriteIndex - recentCount + i + STATUS_HISTORY_SIZE)
            % STATUS_HISTORY_SIZE;

          RecentParcel p = recentList[idx];

          Serial.printf(",%d,%.1f,%.1f,A%d",
                        p.barcode,
                        p.lengthCm,
                        p.weightG,
                        (int)p.destination);
        }

        Serial.println();
      }

      xSemaphoreGive(stateMutex);
    }

    vTaskDelayUntil(&lastWake, pdMS_TO_TICKS(1000));
  }
}


// ============================================================================
// SETUP
// ============================================================================

void setup() {
  Serial.begin(115200);

  beamQueue = xQueueCreate(10, sizeof(BeamEdges));

  if (beamQueue == NULL) {
    Serial.println("ERROR: beamQueue creation failed");
  }

  gateQueueG2 = xQueueCreate(GATE_QUEUE_SIZE, sizeof(GateJob));

  if (gateQueueG2 == NULL) {
    Serial.println("ERROR: gateQueueG2 creation failed");
  }

  gateQueueG3 = xQueueCreate(GATE_QUEUE_SIZE, sizeof(GateJob));

  if (gateQueueG3 == NULL) {
    Serial.println("ERROR: gateQueueG3 creation failed");
  }

  gateQueueG4 = xQueueCreate(GATE_QUEUE_SIZE, sizeof(GateJob));

  if (gateQueueG4 == NULL) {
    Serial.println("ERROR: gateQueueG4 creation failed");
  }

  arrivalQueue = xQueueCreate(ARRIVAL_QUEUE_SIZE, sizeof(ArrivalJob));

  if (arrivalQueue == NULL) {
    Serial.println("ERROR: arrivalQueue creation failed");
  }

  stateMutex = xSemaphoreCreateMutex();

  if (stateMutex == NULL) {
    Serial.println("ERROR: stateMutex creation failed");
  }

  g_gate1Ctrl = true;
  g_gate2Ctrl = false;
  g_gate3Ctrl = false;
  g_gate4Ctrl = false;

  gateParamG2.gate = GATE_G2;
  gateParamG2.queue = gateQueueG2;

  gateParamG3.gate = GATE_G3;
  gateParamG3.queue = gateQueueG3;

  gateParamG4.gate = GATE_G4;
  gateParamG4.queue = gateQueueG4;

  xTaskCreatePinnedToCore(
    gateControlTask,
    "GateG2",
    4096,
    &gateParamG2,
    11,
    NULL,
    0
  );

  xTaskCreatePinnedToCore(
    gateControlTask,
    "GateG3",
    4096,
    &gateParamG3,
    11,
    NULL,
    0
  );

  xTaskCreatePinnedToCore(
    gateControlTask,
    "GateG4",
    4096,
    &gateParamG4,
    11,
    NULL,
    0
  );

  xTaskCreatePinnedToCore(
    productProcessingTask,
    "BeamDispatcher",
    4096,
    NULL,
    10,
    NULL,
    0
  );

  xTaskCreatePinnedToCore(
    arrivalManagerTask,
    "ArrivalManager",
    4096,
    NULL,
    4,
    NULL,
    1
  );

  xTaskCreatePinnedToCore(
    backgroundTask,
    "StatusTask",
    4096,
    NULL,
    2,
    NULL,
    1
  );

  startSimulator();
}


// ============================================================================
// LOOP
// ============================================================================

void loop() {
  vTaskDelay(portMAX_DELAY);
}

/******************************************** END OF STUDENT CODE *****************************************/
/*!!!!!!!!!!!!!!!!!!!!!!!!!!! ANY CODE BELOW THIS LINE SHOULD NOT BE MODIFIED !!!!!!!!!!!!!!!!!!!!!!!!!!!*/
/*================================ START OF SIMULATOR ENGINE ============================================*/

volatile int currentProductIndex = 0;
const int MAX_SCHEDULERS = 4;
ProductScheduler g_schedulers[MAX_SCHEDULERS];

static inline uint64_t distanceToMicros(float distance_cm, float speed_cm_s) {
  double tSec = (double)distance_cm / (double)speed_cm_s;
  return (uint64_t)(tSec * 1e6);
}

void fillProductEvents(ProductScheduler &sch) {
  const Product &p = sch.product;
  sch.totalEvents = 0;
  sch.currentEventIndex = 0;

  auto &events = sch.events;
  int idx = 0;

  uint64_t leadTime = distanceToMicros(DIST_LEAD, sp.v1);

  // Determine product's ground-truth path
  bool sizeOk   = (p.length >= sp.L_min && p.length <= sp.L_max);
  bool weightOk = (p.weight >= sp.W_min && p.weight <= sp.W_max);
  bool isSmallLight = sizeOk && weightOk &&
                      (p.length <= sp.L_threshold) && (p.weight <= sp.W_threshold);

  // Pre-compute destination area index (0=A1, 1=A2, 2=A3)
  int destArea;
  if (!sizeOk) destArea = 0;
  else if (!weightOk) destArea = 0;
  else if (isSmallLight) destArea = 1;
  else destArea = 2;

  // 1. Obstruction sensor: front edge arrives
  events[idx].triggerTimeMicros = leadTime;
  events[idx].eventType = ProductEventType::OBSTRUCTION_SENSOR_RISE;
  events[idx].gateExpected = 0;
  events[idx].destArea = 0;
  idx++;

  // 2. Obstruction sensor: back edge leaves
  uint64_t fallTime = distanceToMicros(p.length, sp.v1);
  events[idx].triggerTimeMicros = leadTime + fallTime;
  events[idx].eventType = ProductEventType::OBSTRUCTION_SENSOR_FALL;
  events[idx].gateExpected = 0;
  events[idx].destArea = 0;
  idx++;

  // 3. G2 check (size gate) - front edge at d0
  // G2: true=divert (size abnormal), expected true if !sizeOk
  uint64_t g2Time = distanceToMicros(sp.d0, sp.v1) + leadTime;
  events[idx].triggerTimeMicros = g2Time;
  events[idx].eventType = ProductEventType::G2_CHECK;
  events[idx].gateExpected = sizeOk ? 0 : 1;
  events[idx].destArea = 0;
  idx++;

  if (!sizeOk) {
    // Product diverted at G2 -> Area 1
    events[idx].triggerTimeMicros = g2Time + 5000;
    events[idx].eventType = ProductEventType::ARRIVE_DESTINATION;
    events[idx].gateExpected = 0;
    events[idx].destArea = 0;
    idx++;

    events[idx].triggerTimeMicros = g2Time + 10000;
    events[idx].eventType = ProductEventType::FINISH;
    events[idx].gateExpected = 0;
    events[idx].destArea = 0;
    idx++;
  } else {
    // 4. Weight sensor window
    uint64_t centerAtWeight = distanceToMicros(sp.d1 + p.length / 2.0f, sp.v1) + leadTime;
    uint64_t halfWindowW = distanceToMicros(p.length * 0.1f, sp.v1);
    events[idx].triggerTimeMicros = centerAtWeight - halfWindowW;
    events[idx].eventType = ProductEventType::WEIGHT_SENSOR_ENTER_WINDOW;
    events[idx].gateExpected = 0;
    events[idx].destArea = 0;
    idx++;

    events[idx].triggerTimeMicros = centerAtWeight + halfWindowW;
    events[idx].eventType = ProductEventType::WEIGHT_SENSOR_EXIT_WINDOW;
    events[idx].gateExpected = 0;
    events[idx].destArea = 0;
    idx++;

    // 5. G3 check (weight gate) - front edge at d2
    // G3: true=divert (weight abnormal), expected true if !weightOk
    uint64_t g3Time = distanceToMicros(sp.d2, sp.v1) + leadTime;
    events[idx].triggerTimeMicros = g3Time;
    events[idx].eventType = ProductEventType::G3_CHECK;
    events[idx].gateExpected = weightOk ? 0 : 1;
    events[idx].destArea = 0;
    idx++;

    if (!weightOk) {
      // Product diverted at G3 -> Area 1
      events[idx].triggerTimeMicros = g3Time + 5000;
      events[idx].eventType = ProductEventType::ARRIVE_DESTINATION;
      events[idx].gateExpected = 0;
      events[idx].destArea = 0;
      idx++;

      events[idx].triggerTimeMicros = g3Time + 10000;
      events[idx].eventType = ProductEventType::FINISH;
      events[idx].gateExpected = 0;
      events[idx].destArea = 0;
      idx++;
    } else {
      // 6. Barcode sensor window
      uint64_t centerAtBarcode = distanceToMicros(sp.d3 + p.length / 2.0f, sp.v1) + leadTime;
      uint64_t halfWindowB = distanceToMicros(p.length * 0.1f, sp.v1);
      events[idx].triggerTimeMicros = centerAtBarcode - halfWindowB;
      events[idx].eventType = ProductEventType::BARCODE_SENSOR_ENTER_WINDOW;
      events[idx].gateExpected = 0;
      events[idx].destArea = 0;
      idx++;

      events[idx].triggerTimeMicros = centerAtBarcode + halfWindowB;
      events[idx].eventType = ProductEventType::BARCODE_SENSOR_EXIT_WINDOW;
      events[idx].gateExpected = 0;
      events[idx].destArea = 0;
      idx++;

      // 7. G4 check (routing gate) - front edge at d4
      // G4: false=Conv2/Area2, true=Conv3/Area3
      uint64_t g4Time = distanceToMicros(sp.d4, sp.v1) + leadTime;
      events[idx].triggerTimeMicros = g4Time;
      events[idx].eventType = ProductEventType::G4_CHECK;
      events[idx].gateExpected = isSmallLight ? 0 : 1;
      events[idx].destArea = 0;
      idx++;

      // 8. Arrive at destination area
      uint64_t arriveTime;
      if (isSmallLight) {
        arriveTime = g4Time + distanceToMicros(sp.d5, sp.v2);
      } else {
        arriveTime = g4Time + distanceToMicros(sp.d6, sp.v3);
      }
      events[idx].triggerTimeMicros = arriveTime;
      events[idx].eventType = ProductEventType::ARRIVE_DESTINATION;
      events[idx].gateExpected = 0;
      events[idx].destArea = destArea;
      idx++;

      events[idx].triggerTimeMicros = arriveTime + 5000;
      events[idx].eventType = ProductEventType::FINISH;
      events[idx].gateExpected = 0;
      events[idx].destArea = 0;
      idx++;
    }
  }

  sch.totalEvents = idx;

  // Sort events by time
  for (int i = 0; i < sch.totalEvents - 1; i++) {
    for (int j = i + 1; j < sch.totalEvents; j++) {
      if (events[i].triggerTimeMicros > events[j].triggerTimeMicros) {
        ProductEvent tmp = events[i];
        events[i] = events[j];
        events[j] = tmp;
      }
    }
  }
}

void printProductEvents(const ProductScheduler &sch) {
  Serial.println("===== Product Event Timeline =====");
  Serial.printf("Length: %.2f cm  Weight: %.2f g  Barcode: %d\n",
                sch.product.length, sch.product.weight, sch.product.barcodeID);

  bool sizeOk = (sch.product.length >= sp.L_min && sch.product.length <= sp.L_max);
  bool weightOk = (sch.product.weight >= sp.W_min && sch.product.weight <= sp.W_max);
  const char* dest = "???";
  if (!sizeOk) dest = "Area1(size)";
  else if (!weightOk) dest = "Area1(weight)";
  else if (sch.product.length <= sp.L_threshold && sch.product.weight <= sp.W_threshold) dest = "Area2";
  else dest = "Area3";
  Serial.printf("Expected destination: %s\n", dest);

  for (int i = 0; i < sch.totalEvents; i++) {
    const ProductEvent &evt = sch.events[i];
    float timeMs = evt.triggerTimeMicros / 1000.0f;
    Serial.printf("  %d: %.3f ms - ", i, timeMs);
    switch (evt.eventType) {
      case ProductEventType::OBSTRUCTION_SENSOR_RISE:   Serial.println("OBSTRUCTION_RISE"); break;
      case ProductEventType::OBSTRUCTION_SENSOR_FALL:   Serial.println("OBSTRUCTION_FALL"); break;
      case ProductEventType::G2_CHECK:                  Serial.println("G2_CHECK (size)"); break;
      case ProductEventType::WEIGHT_SENSOR_ENTER_WINDOW: Serial.println("WEIGHT_ENTER"); break;
      case ProductEventType::WEIGHT_SENSOR_EXIT_WINDOW: Serial.println("WEIGHT_EXIT"); break;
      case ProductEventType::G3_CHECK:                  Serial.println("G3_CHECK (weight)"); break;
      case ProductEventType::BARCODE_SENSOR_ENTER_WINDOW: Serial.println("BARCODE_ENTER"); break;
      case ProductEventType::BARCODE_SENSOR_EXIT_WINDOW: Serial.println("BARCODE_EXIT"); break;
      case ProductEventType::G4_CHECK:                  Serial.println("G4_CHECK (route)"); break;
      case ProductEventType::ARRIVE_DESTINATION:        Serial.println("ARRIVE_DESTINATION"); break;
      case ProductEventType::FINISH:                    Serial.println("FINISH"); break;
      default: Serial.println("UNKNOWN"); break;
    }
  }
  Serial.println("==================================");
}

// Hardware timer ISR - executes product events
void ARDUINO_ISR_ATTR onTimerInterrupt(void* arg) {
  ProductScheduler* sch = (ProductScheduler*)arg;
  hw_timer_t* timer = sch->timerHandle;

  if (!timer) return;

  if (sch->currentEventIndex >= sch->totalEvents) {
    timerEnd(timer);
    sch->timerHandle = nullptr;
    return;
  }

  // Get current event
  ProductEvent evt = sch->events[sch->currentEventIndex];
  sch->currentEventIndex++;

  // Execute event logic (no floating-point comparisons - all pre-computed)
  int evtType = (int)evt.eventType;

  if (evtType == (int)ProductEventType::OBSTRUCTION_SENSOR_RISE) {
    g_obstructionSensor = true;
    digitalWrite(g_obstructionSensorPin, HIGH);
    obstructionSensorInterrupt();
  }
  else if (evtType == (int)ProductEventType::OBSTRUCTION_SENSOR_FALL) {
    g_obstructionSensor = false;
    digitalWrite(g_obstructionSensorPin, LOW);
    obstructionSensorInterrupt();
  }
  else if (evtType == (int)ProductEventType::WEIGHT_SENSOR_ENTER_WINDOW) {
    g_weightSensor = sch->product.weight;
  }
  else if (evtType == (int)ProductEventType::WEIGHT_SENSOR_EXIT_WINDOW) {
    g_weightSensor = 0.0f;
  }
  else if (evtType == (int)ProductEventType::BARCODE_SENSOR_ENTER_WINDOW) {
    g_barcodeReader = sch->product.barcodeID;
  }
  else if (evtType == (int)ProductEventType::BARCODE_SENSOR_EXIT_WINDOW) {
    g_barcodeReader = 0;
  }
  else if (evtType == (int)ProductEventType::G2_CHECK) {
    // G2: true=divert. Pre-computed expected value in gateExpected
    if ((int)g_gate2Ctrl != evt.gateExpected) {
      errorGateCNT[0]++;
    }
  }
  else if (evtType == (int)ProductEventType::G3_CHECK) {
    // G3: true=divert. Pre-computed expected value in gateExpected
    if ((int)g_gate3Ctrl != evt.gateExpected) {
      errorGateCNT[1]++;
    }
  }
  else if (evtType == (int)ProductEventType::G4_CHECK) {
    // G4: false=Conv2, true=Conv3. Pre-computed expected value
    if ((int)g_gate4Ctrl != evt.gateExpected) {
      errorGateCNT[2]++;
    }
  }
  else if (evtType == (int)ProductEventType::ARRIVE_DESTINATION) {
    simAreaCount[evt.destArea]++;
  }
  else if (evtType == (int)ProductEventType::FINISH) {
    digitalWrite(sch->debugPin, LOW);
  }

  // Set up next event or end timer
  if (sch->currentEventIndex < sch->totalEvents) {
    timerAlarm(timer, sch->events[sch->currentEventIndex].triggerTimeMicros, false, 0);
  } else {
    timerEnd(timer);
    sch->timerHandle = nullptr;
  }
}

hw_timer_t* allocateTimerForProduct(ProductScheduler &sch) {
  digitalWrite(sch.debugPin, HIGH);
  fillProductEvents(sch);

  hw_timer_t* timer = timerBegin(1000000);  // 1MHz = 1us resolution
  if (!timer) return nullptr;

  sch.timerHandle = timer;
  timerAttachInterruptArg(timer, &onTimerInterrupt, (void*)&sch);

  if (sch.totalEvents > 0) {
    digitalWrite(sch.debugPin, LOW);
    timerWrite(timer, 0);
    timerAlarm(timer, sch.events[0].triggerTimeMicros, false, 0);
  }
  return timer;
}

// Status reporting task - prints simulator state periodically
void statusReportTask(void *pvParameters) {
  vTaskDelay(2000 / portTICK_PERIOD_MS);  // Initial delay
  while (true) {
    Serial.printf("[SIM] Products loaded: %d/%d | Area counts: A1=%d A2=%d A3=%d | Gate errors: G2=%d G3=%d G4=%d\n",
                  currentProductIndex, numProducts,
                  simAreaCount[0], simAreaCount[1], simAreaCount[2],
                  errorGateCNT[0], errorGateCNT[1], errorGateCNT[2]);

    // Check if all products finished
    if (currentProductIndex >= numProducts) {
      bool allDone = true;
      for (int i = 0; i < MAX_SCHEDULERS; i++) {
        if (g_schedulers[i].timerHandle != nullptr) {
          allDone = false;
          break;
        }
      }
      if (allDone) {
        int totalArrived = simAreaCount[0] + simAreaCount[1] + simAreaCount[2];
        Serial.println("\n=== SIMULATION COMPLETE ===");
        Serial.printf("Total products processed: %d/%d\n", totalArrived, numProducts);
        Serial.printf("Area 1: %d  Area 2: %d  Area 3: %d\n",
                      simAreaCount[0], simAreaCount[1], simAreaCount[2]);
        Serial.printf("Gate errors: G2=%d  G3=%d  G4=%d\n",
                      errorGateCNT[0], errorGateCNT[1], errorGateCNT[2]);
        if (errorGateCNT[0] == 0 && errorGateCNT[1] == 0 && errorGateCNT[2] == 0) {
          Serial.println("Result: ALL GATES CORRECT!");
        } else {
          Serial.println("Result: GATE ERRORS DETECTED - check your control logic");
        }
        Serial.println("===========================\n");
        vTaskDelete(NULL);
        return;
      }
    }
    vTaskDelay(2000 / portTICK_PERIOD_MS);
  }
}

// Product loading task - loads products at fixed intervals, checks G1 gate
void productLoadingTask(void *pvParameters) {
  TickType_t xLastWakeTime = xTaskGetTickCount();

  while (true) {
    if (currentProductIndex < numProducts) {
      // Check G1 intake gate
      if (g_gate1Ctrl) {
        bool schedulerFound = false;
        for (int i = 0; i < MAX_SCHEDULERS; i++) {
          if (g_schedulers[i].timerHandle == nullptr) {
            g_schedulers[i].product = productArray[currentProductIndex];
            g_schedulers[i].debugPin = DEBUG_PIN + currentProductIndex % 3;

            hw_timer_t* t = allocateTimerForProduct(g_schedulers[i]);
            if (!t) {
              Serial.println("ERROR: No hardware timer available!");
            } else {
              currentProductIndex++;
              schedulerFound = true;
            }
            break;
          }
        }
        if (!schedulerFound) {
          // No scheduler available this cycle, will retry next interval
        }
      } else {
        // G1 is closed - product blocked at intake
        // The product remains in the queue, will be loaded when G1 opens
      }
    }
    vTaskDelayUntil(&xLastWakeTime, sp.productInterval / portTICK_PERIOD_MS);
  }
}

void startSimulator(void) {
  // Generate parameters from student number
  generateParameters(STUDENT_NUMBER);
  printParameters();

  // Generate test product array
  generateProductArray();

  Serial.printf("\nGenerated %d test products:\n", numProducts);
  for (int i = 0; i < numProducts; i++) {
    bool sizeOk = (productArray[i].length >= sp.L_min && productArray[i].length <= sp.L_max);
    bool weightOk = (productArray[i].weight >= sp.W_min && productArray[i].weight <= sp.W_max);
    const char* dest;
    if (!sizeOk) dest = "A1(size)";
    else if (!weightOk) dest = "A1(weight)";
    else if (productArray[i].length <= sp.L_threshold && productArray[i].weight <= sp.W_threshold) dest = "A2";
    else dest = "A3";
    Serial.printf("  [%d] L=%.2f W=%.2f BC=%d -> %s\n",
                  i, productArray[i].length, productArray[i].weight, productArray[i].barcodeID, dest);
  }
  Serial.println();

  // Setup GPIO pins
  pinMode(g_obstructionSensorPin, OUTPUT);
  pinMode(DEBUG_PIN, OUTPUT);
  pinMode(DEBUG_PIN + 1, OUTPUT);
  pinMode(DEBUG_PIN + 2, OUTPUT);
  digitalWrite(DEBUG_PIN, LOW);
  digitalWrite(DEBUG_PIN + 1, LOW);
  digitalWrite(DEBUG_PIN + 2, LOW);

  // Initialize sensor outputs
  g_obstructionSensor = false;
  g_barcodeReader = 0;
  g_weightSensor = 0.0f;

  // Initialize gate controls to default
  g_gate1Ctrl = true;
  g_gate2Ctrl = false;
  g_gate3Ctrl = false;
  g_gate4Ctrl = false;

  // Reset counters
  currentProductIndex = 0;
  for (int i = 0; i < MAX_SCHEDULERS; i++) {
    g_schedulers[i].timerHandle = nullptr;
  }
  for (int i = 0; i < 3; i++) {
    errorGateCNT[i] = 0;
    simAreaCount[i] = 0;
  }

  // Create product loading task (highest priority)
  xTaskCreate(
    productLoadingTask,
    "ProductLoader",
    2048,
    NULL,
    configMAX_PRIORITIES - 1,
    NULL
  );

  // Create status reporting task
  xTaskCreate(
    statusReportTask,
    "StatusReport",
    2048,
    NULL,
    1,
    NULL
  );

  Serial.println("=== SmartSort Simulator Started ===\n");
}