#include <Arduino.h>
#include <stdint.h>
#include <string.h>

// Compile-time constants (zero runtime CPU cycles wasted)
constexpr uint8_t SENSOR_ID = 42;
constexpr size_t MAX_PAYLOAD_SIZE = 32;

// Packed structure for our telemetry data
struct TelemetryPacket {
    uint8_t id;
    float soil_moisture;
    float battery_voltage;
};

class AgriSensorNode {
private:
    // Static allocation using a fixed C-style array (Zero Heap, 100% Safe)
    uint8_t tx_buffer_[MAX_PAYLOAD_SIZE];
    size_t payload_len_;

public:
    // Constructor initializes state statically
    AgriSensorNode() : payload_len_(0) {
        memset(tx_buffer_, 0, MAX_PAYLOAD_SIZE);
    }

    bool preparePayload(float moisture, float voltage) {
        TelemetryPacket packet{SENSOR_ID, moisture, voltage};
        
        if (sizeof(TelemetryPacket) > MAX_PAYLOAD_SIZE) {
            return false;
        }

        // Copy struct bytes directly into our static buffer
        memcpy(tx_buffer_, &packet, sizeof(TelemetryPacket));
        payload_len_ = sizeof(TelemetryPacket);
        
        return true;
    }

    const uint8_t* getData() const { return tx_buffer_; }
    size_t getLength() const { return payload_len_; }
};

// Global instance allocated statically at boot—zero runtime reallocation
static AgriSensorNode node;

void setup() {
    Serial.begin(115200);
    delay(1000);
    
    Serial.println("=== Zero-Heap Static Allocation Test ===");

    float current_moisture = 34.5f; // Simulated soil reading
    float current_voltage = 3.85f;  // Simulated LiFePO4 voltage

    if (node.preparePayload(current_moisture, current_voltage)) {
        Serial.printf("Payload packed successfully. Size: %u bytes\n", node.getLength());
        
        Serial.print("Raw byte dump in static buffer: ");
        const uint8_t* data = node.getData();
        for(size_t i = 0; i < node.getLength(); i++) {
            Serial.printf("0x%02X ", data[i]);
        }
        Serial.println("\n----------------------------------------");
    }
}

void loop() {
    delay(10000);
    Serial.println("Node idle: Memory footprint is 100% static (No heap fragmentation).");
}