#include "Arduino.h"

#define STUDENT_NUMBER 2246306

// ============================================================================
// 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 LENGTH_TOL_CM      0.02f
#define WEIGHT_TOL_G       0.02f
#define SORTRT_HISTORY_LEN 6


// ============================================================================
// DATA TYPES
// ============================================================================

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


typedef struct {
    float lengthCm;
    float weightG;
    int trackingNumber;
    int destination;       // 1=A1, 2=A2, 3=A3
} tracked_product_t;


typedef struct {
    sensor_edges_t edges;
} product_task_context_t;


typedef struct {
    int trackingNumber;
    float lengthCm;
    float weightG;
    int destination;
} completed_product_t;


typedef struct {
    int arrived[3];
    int travelling[3];

    float sumLengthAll;
    float sumWeightAll;
    int countAll;

    float sumLengthA2;
    float sumWeightA2;
    int countA2;

    float sumLengthA3;
    float sumWeightA3;
    int countA3;
} controller_stats_t;


// Gate command context.
// Each gate command is a timed event.
typedef struct {
    volatile bool *gateSignal;

    volatile uint32_t *activeCommandId;
    volatile int64_t  *lastAppliedSetTimeUs;

    uint32_t commandId;

    bool requiredState;

    int64_t setTimeUs;
    int64_t clearTimeUs;
} gate_command_context_t;


// ============================================================================
// GLOBAL STATE
// ============================================================================

static QueueHandle_t edgeQueue = NULL;
static SemaphoreHandle_t stateMutex = NULL;

static volatile sensor_edges_t currentEdges = {0, 0};

static controller_stats_t ctrlStats = {0};

static completed_product_t recentProducts[SORTRT_HISTORY_LEN];
static int recentWritePos = 0;
static int recentCount = 0;

static volatile bool emergencyActive = false;


// ============================================================================
// GATE SCHEDULER STATE
// ============================================================================

// Used to generate unique command IDs.
static volatile uint32_t nextGateCommandId = 0;

// Current active command for each gate.
static volatile uint32_t g2ActiveCommandId = 0;
static volatile uint32_t g3ActiveCommandId = 0;
static volatile uint32_t g4ActiveCommandId = 0;

// Last applied set-time for each gate.
// Prevents an older delayed command from overwriting a newer applied command.
static volatile int64_t g2LastAppliedSetTimeUs = 0;
static volatile int64_t g3LastAppliedSetTimeUs = 0;
static volatile int64_t g4LastAppliedSetTimeUs = 0;

// Critical section for gate scheduler state.
static portMUX_TYPE gateSchedulerMux = portMUX_INITIALIZER_UNLOCKED;


// ============================================================================
// FUNCTION DECLARATIONS
// ============================================================================

static int64_t travelTimeUs(float distanceCm, float speedCmPerSec);
static void waitUntilTimeUs(int64_t targetUs);

static bool lengthIsValid(float lengthCm);
static bool weightIsValid(float weightG);
static bool productIsArea2(float lengthCm, float weightG);

static void refreshIntakeGate();
static void reserveAreaSlot(int area);
static void recordRecentProduct(int trackingNumber, float lengthCm, float weightG, int area);
static void markProductArrived(int area, float lengthCm, float weightG, int trackingNumber);

static float sampleWeightSensor(int64_t centreTimeUs, float productLengthCm);
static int sampleBarcodeSensor(int64_t centreTimeUs, float productLengthCm);

static void scheduleGateCommand(volatile bool *gateSignal,
                                volatile uint32_t *activeCommandId,
                                volatile int64_t *lastAppliedSetTimeUs,
                                bool requiredState,
                                int64_t frontEdgeAtGateUs,
                                float productLengthCm);

void gateCommandTask(void *pvParameters);

static void resetControllerOnly();

void handleOneProductTask(void *pvParameters);


// ============================================================================
// TIMING HELPERS
// ============================================================================

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

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


static void waitUntilTimeUs(int64_t targetUs) {
    while (!emergencyActive) {
        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 lengthIsValid(float lengthCm) {
    return (lengthCm >= (sp.L_min - LENGTH_TOL_CM) &&
            lengthCm <= (sp.L_max + LENGTH_TOL_CM));
}


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


static bool productIsArea2(float lengthCm, float weightG) {
    return (lengthCm <= (sp.L_threshold + LENGTH_TOL_CM) &&
            weightG <= (sp.W_threshold + WEIGHT_TOL_G));
}


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

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

    xSemaphoreTake(stateMutex, portMAX_DELAY);

    bool a1Blocked = (ctrlStats.arrived[0] + ctrlStats.travelling[0]) >= sp.C1;
    bool a2Blocked = (ctrlStats.arrived[1] + ctrlStats.travelling[1]) >= sp.C2;
    bool a3Blocked = (ctrlStats.arrived[2] + ctrlStats.travelling[2]) >= sp.C3;

    if (emergencyActive || a1Blocked || a2Blocked || a3Blocked) {
        g_gate1Ctrl = false;
    }
    else {
        g_gate1Ctrl = true;
    }

    xSemaphoreGive(stateMutex);
}


static void reserveAreaSlot(int area) {
    int idx = area - 1;

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

    xSemaphoreTake(stateMutex, portMAX_DELAY);
    ctrlStats.travelling[idx]++;
    xSemaphoreGive(stateMutex);

    refreshIntakeGate();
}


static void recordRecentProduct(int trackingNumber, float lengthCm, float weightG, int area) {
    if (stateMutex == NULL) {
        return;
    }

    xSemaphoreTake(stateMutex, portMAX_DELAY);

    recentProducts[recentWritePos].trackingNumber = trackingNumber;
    recentProducts[recentWritePos].lengthCm = lengthCm;
    recentProducts[recentWritePos].weightG = weightG;
    recentProducts[recentWritePos].destination = area;

    recentWritePos = (recentWritePos + 1) % SORTRT_HISTORY_LEN;

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

    xSemaphoreGive(stateMutex);
}


static void markProductArrived(int area, float lengthCm, float weightG, int trackingNumber) {
    int idx = area - 1;

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

    xSemaphoreTake(stateMutex, portMAX_DELAY);

    if (ctrlStats.travelling[idx] > 0) {
        ctrlStats.travelling[idx]--;
    }

    ctrlStats.arrived[idx]++;

    ctrlStats.sumLengthAll += lengthCm;
    ctrlStats.sumWeightAll += weightG;
    ctrlStats.countAll++;

    if (area == 2) {
        ctrlStats.sumLengthA2 += lengthCm;
        ctrlStats.sumWeightA2 += weightG;
        ctrlStats.countA2++;
    }
    else if (area == 3) {
        ctrlStats.sumLengthA3 += lengthCm;
        ctrlStats.sumWeightA3 += weightG;
        ctrlStats.countA3++;
    }

    xSemaphoreGive(stateMutex);

    recordRecentProduct(trackingNumber, lengthCm, weightG, area);

    refreshIntakeGate();
}


// ============================================================================
// SENSOR SAMPLING HELPERS
// ============================================================================

static float sampleWeightSensor(int64_t centreTimeUs, float productLengthCm) {
    float result = 0.0f;

    int64_t halfWindowUs = travelTimeUs(productLengthCm * 0.10f, sp.v1);

    int64_t windowStartUs = centreTimeUs - halfWindowUs + 300;
    int64_t windowEndUs   = centreTimeUs + halfWindowUs - 300;

    waitUntilTimeUs(windowStartUs);

    while (!emergencyActive && esp_timer_get_time() <= windowEndUs) {
        if (g_weightSensor > 0.0f) {
            result = g_weightSensor;
            break;
        }

        delayMicroseconds(300);
    }

    return result;
}


static int sampleBarcodeSensor(int64_t centreTimeUs, float productLengthCm) {
    int result = 0;

    int64_t halfWindowUs = travelTimeUs(productLengthCm * 0.10f, sp.v1);

    int64_t windowStartUs = centreTimeUs - halfWindowUs + 300;
    int64_t windowEndUs   = centreTimeUs + halfWindowUs - 300;

    waitUntilTimeUs(windowStartUs);

    while (!emergencyActive && esp_timer_get_time() <= windowEndUs) {
        if (g_barcodeReader != 0) {
            result = g_barcodeReader;
            break;
        }

        delayMicroseconds(300);
    }

    return result;
}


// ============================================================================
// GATE TIMING SCHEDULER
// ============================================================================
//
// This is the key fix.
//
// Each gate command is scheduled as its own timed event.
// The gate is set just before the product reaches the gate.
// Older products are prevented from clearing or overwriting a newer command.
//

static void scheduleGateCommand(volatile bool *gateSignal,
                                volatile uint32_t *activeCommandId,
                                volatile int64_t *lastAppliedSetTimeUs,
                                bool requiredState,
                                int64_t frontEdgeAtGateUs,
                                float productLengthCm) {
    if (gateSignal == NULL || activeCommandId == NULL || lastAppliedSetTimeUs == NULL) {
        return;
    }

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

    int64_t setTimeUs = frontEdgeAtGateUs - gateLeadUs;

    int64_t clearTimeUs =
        frontEdgeAtGateUs + travelTimeUs(productLengthCm, sp.v1) + 2000;

    gate_command_context_t *ctx =
        (gate_command_context_t *)pvPortMalloc(sizeof(gate_command_context_t));

    if (ctx == NULL) {
        return;
    }

    uint32_t commandId;

    portENTER_CRITICAL(&gateSchedulerMux);
    nextGateCommandId++;
    commandId = nextGateCommandId;
    portEXIT_CRITICAL(&gateSchedulerMux);

    ctx->gateSignal = gateSignal;
    ctx->activeCommandId = activeCommandId;
    ctx->lastAppliedSetTimeUs = lastAppliedSetTimeUs;
    ctx->commandId = commandId;
    ctx->requiredState = requiredState;
    ctx->setTimeUs = setTimeUs;
    ctx->clearTimeUs = clearTimeUs;

    xTaskCreatePinnedToCore(
        gateCommandTask,
        "GateCmd",
        2048,
        ctx,
        9,
        NULL,
        0
    );
}


void gateCommandTask(void *pvParameters) {
    gate_command_context_t *ctx = (gate_command_context_t *)pvParameters;

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

    waitUntilTimeUs(ctx->setTimeUs);

    if (!emergencyActive) {
        bool shouldApply = false;

        portENTER_CRITICAL(&gateSchedulerMux);

        // Apply only if this command is not older than the last command
        // already applied to this gate.
        if (ctx->setTimeUs >= *(ctx->lastAppliedSetTimeUs)) {
            *(ctx->lastAppliedSetTimeUs) = ctx->setTimeUs;
            *(ctx->activeCommandId) = ctx->commandId;
            shouldApply = true;
        }

        portEXIT_CRITICAL(&gateSchedulerMux);

        if (shouldApply) {
            *(ctx->gateSignal) = ctx->requiredState;
        }
    }

    waitUntilTimeUs(ctx->clearTimeUs);

    if (!emergencyActive) {
        bool shouldClear = false;

        portENTER_CRITICAL(&gateSchedulerMux);

        // Only the command currently active for this gate may clear it.
        // This prevents an older product from resetting the gate after
        // a newer product has already set its own decision.
        if (*(ctx->activeCommandId) == ctx->commandId) {
            shouldClear = true;
            *(ctx->activeCommandId) = 0;
        }

        portEXIT_CRITICAL(&gateSchedulerMux);

        if (shouldClear) {
            *(ctx->gateSignal) = false;
        }
    }

    vPortFree(ctx);
    vTaskDelete(NULL);
}


// ============================================================================
// RESET HELPER
// ============================================================================

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

        memset(&ctrlStats, 0, sizeof(ctrlStats));
        memset(recentProducts, 0, sizeof(recentProducts));

        recentWritePos = 0;
        recentCount = 0;

        xSemaphoreGive(stateMutex);
    }

    emergencyActive = false;

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

    portENTER_CRITICAL(&gateSchedulerMux);

    nextGateCommandId = 0;

    g2ActiveCommandId = 0;
    g3ActiveCommandId = 0;
    g4ActiveCommandId = 0;

    g2LastAppliedSetTimeUs = 0;
    g3LastAppliedSetTimeUs = 0;
    g4LastAppliedSetTimeUs = 0;

    portEXIT_CRITICAL(&gateSchedulerMux);

    refreshIntakeGate();
}


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

void IRAM_ATTR obstructionSensorInterrupt() {
    BaseType_t shouldYield = pdFALSE;

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

        if (edgeQueue != NULL) {
            xQueueSendFromISR(edgeQueue, (void*)&currentEdges, &shouldYield);
        }

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


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

void productProcessingTask(void *pvParameters) {
    sensor_edges_t edges;

    while (true) {
        if (xQueueReceive(edgeQueue, &edges, portMAX_DELAY) == pdTRUE) {
            if (emergencyActive) {
                continue;
            }

            product_task_context_t *ctx =
                (product_task_context_t *)pvPortMalloc(sizeof(product_task_context_t));

            if (ctx == NULL) {
                continue;
            }

            ctx->edges = edges;

            xTaskCreatePinnedToCore(
                handleOneProductTask,
                "ProductControl",
                4096,
                ctx,
                8,
                NULL,
                0
            );
        }
    }
}


// ============================================================================
// SINGLE PRODUCT CONTROL TASK - CORE 0
// ============================================================================

void handleOneProductTask(void *pvParameters) {
    product_task_context_t *ctx = (product_task_context_t *)pvParameters;

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

    sensor_edges_t edges = ctx->edges;
    vPortFree(ctx);

    if (emergencyActive) {
        vTaskDelete(NULL);
        return;
    }

    tracked_product_t item;
    item.lengthCm = 0.0f;
    item.weightG = 0.0f;
    item.trackingNumber = 0;
    item.destination = 0;

    // ------------------------------------------------------------
    // Length calculation
    // ------------------------------------------------------------
    int64_t blockedUs = edges.fallUs - edges.riseUs;
    item.lengthCm = (float)blockedUs * sp.v1 / 1000000.0f;

    int64_t g2TimeUs = edges.riseUs + travelTimeUs(sp.d0, sp.v1);
    int64_t g3TimeUs = edges.riseUs + travelTimeUs(sp.d2, sp.v1);
    int64_t g4TimeUs = edges.riseUs + travelTimeUs(sp.d4, sp.v1);

    // ------------------------------------------------------------
    // G2 size decision
    // ------------------------------------------------------------
    if (!lengthIsValid(item.lengthCm)) {
        item.destination = 1;
        item.weightG = 0.0f;
        item.trackingNumber = 0;

        reserveAreaSlot(1);

        scheduleGateCommand(&g_gate2Ctrl,
                            &g2ActiveCommandId,
                            &g2LastAppliedSetTimeUs,
                            true,
                            g2TimeUs,
                            item.lengthCm);

        waitUntilTimeUs(g2TimeUs + 5000);

        if (!emergencyActive) {
            markProductArrived(item.destination,
                               item.lengthCm,
                               item.weightG,
                               item.trackingNumber);
        }

        vTaskDelete(NULL);
        return;
    }

    scheduleGateCommand(&g_gate2Ctrl,
                        &g2ActiveCommandId,
                        &g2LastAppliedSetTimeUs,
                        false,
                        g2TimeUs,
                        item.lengthCm);

    if (emergencyActive) {
        vTaskDelete(NULL);
        return;
    }

    // ------------------------------------------------------------
    // Weight measurement
    // ------------------------------------------------------------
    float weightCentreDistanceCm = sp.d1 - (item.lengthCm / 2.0f);

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

    int64_t weightCentreTimeUs =
        edges.fallUs + travelTimeUs(weightCentreDistanceCm, sp.v1);

    item.weightG = sampleWeightSensor(weightCentreTimeUs, item.lengthCm);

    // ------------------------------------------------------------
    // G3 weight decision
    // ------------------------------------------------------------
    if (!weightIsValid(item.weightG)) {
        item.destination = 1;
        item.trackingNumber = 0;

        reserveAreaSlot(1);

        scheduleGateCommand(&g_gate3Ctrl,
                            &g3ActiveCommandId,
                            &g3LastAppliedSetTimeUs,
                            true,
                            g3TimeUs,
                            item.lengthCm);

        waitUntilTimeUs(g3TimeUs + 5000);

        if (!emergencyActive) {
            markProductArrived(item.destination,
                               item.lengthCm,
                               item.weightG,
                               item.trackingNumber);
        }

        vTaskDelete(NULL);
        return;
    }

    scheduleGateCommand(&g_gate3Ctrl,
                        &g3ActiveCommandId,
                        &g3LastAppliedSetTimeUs,
                        false,
                        g3TimeUs,
                        item.lengthCm);

    if (emergencyActive) {
        vTaskDelete(NULL);
        return;
    }

    // ------------------------------------------------------------
    // Barcode reading
    // ------------------------------------------------------------
    float barcodeCentreDistanceCm = sp.d3 - (item.lengthCm / 2.0f);

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

    int64_t barcodeCentreTimeUs =
        edges.fallUs + travelTimeUs(barcodeCentreDistanceCm, sp.v1);

    item.trackingNumber = sampleBarcodeSensor(barcodeCentreTimeUs, item.lengthCm);

    // ------------------------------------------------------------
    // G4 route decision
    // ------------------------------------------------------------
    if (productIsArea2(item.lengthCm, item.weightG)) {
        item.destination = 2;

        reserveAreaSlot(2);

        scheduleGateCommand(&g_gate4Ctrl,
                            &g4ActiveCommandId,
                            &g4LastAppliedSetTimeUs,
                            false,
                            g4TimeUs,
                            item.lengthCm);

        int64_t arriveUs = g4TimeUs + travelTimeUs(sp.d5, sp.v2);
        waitUntilTimeUs(arriveUs);
    }
    else {
        item.destination = 3;

        reserveAreaSlot(3);

        scheduleGateCommand(&g_gate4Ctrl,
                            &g4ActiveCommandId,
                            &g4LastAppliedSetTimeUs,
                            true,
                            g4TimeUs,
                            item.lengthCm);

        int64_t arriveUs = g4TimeUs + travelTimeUs(sp.d6, sp.v3);
        waitUntilTimeUs(arriveUs);
    }

    if (!emergencyActive) {
        markProductArrived(item.destination,
                           item.lengthCm,
                           item.weightG,
                           item.trackingNumber);
    }

    vTaskDelete(NULL);
}


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

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

    while (true) {
        // ------------------------------------------------------------
        // Serial command processing
        // ------------------------------------------------------------
        while (Serial.available() > 0) {
            String command = Serial.readStringUntil('\n');
            command.trim();

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

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

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

                    xSemaphoreGive(stateMutex);
                }

                Serial.printf("sortSTAT: %.2f,%.2f,%.2f,%.2f,%.2f,%.2f\n",
                              Lavg, L2avg, L3avg, Wavg, W2avg, W3avg);
            }
            else if (command == "reset") {
                resetControllerOnly();
            }
            else if (command == "emergency") {
                emergencyActive = true;

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

                Serial.println("EMERGENCY: System halted");
            }
            else {
                // Unknown input ignored.
            }
        }

        // ------------------------------------------------------------
        // Capacity check
        // ------------------------------------------------------------
        refreshIntakeGate();

        // ------------------------------------------------------------
        // sortRT output
        // ------------------------------------------------------------
        if (stateMutex != NULL) {
            xSemaphoreTake(stateMutex, portMAX_DELAY);

            Serial.printf("sortRT: %03d,%03d,%03d",
                          ctrlStats.arrived[0],
                          ctrlStats.arrived[1],
                          ctrlStats.arrived[2]);

            for (int i = 0; i < recentCount; i++) {
                int idx =
                    (recentWritePos - recentCount + i + SORTRT_HISTORY_LEN)
                    % SORTRT_HISTORY_LEN;

                completed_product_t p = recentProducts[idx];

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

            Serial.println();

            xSemaphoreGive(stateMutex);
        }

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


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

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

    edgeQueue = xQueueCreate(10, sizeof(sensor_edges_t));

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

    stateMutex = xSemaphoreCreateMutex();

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

    // Initial safe gate states.
    g_gate1Ctrl = true;
    g_gate2Ctrl = false;
    g_gate3Ctrl = false;
    g_gate4Ctrl = false;

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

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

    // Randomize product generation.
    randomSeed((uint32_t)esp_timer_get_time());

    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");
}