// #include <Arduino.h>

// // --- Hardware Configuration ---
// #define IN1 9
// #define IN2 10
// #define IN3 11
// #define IN4 12

// // The step sequence (standard for 28BYJ-48 motors)
// int stepSequence[8][4] = {
//   { 1, 0, 0, 0 },
//   { 1, 1, 0, 0 },
//   { 0, 1, 0, 0 },
//   { 0, 1, 1, 0 },
//   { 0, 0, 1, 0 },
//   { 0, 0, 1, 1 },
//   { 0, 0, 0, 1 },
//   { 1, 0, 0, 1 }
// };

// // --- Configuration Constants ---
// const int STEPS_PER_REV = 4096; 
// int stepInterval = 1;           
// bool autoMode = true;           

// // --- State Variables ---
// long targetSteps = 0;           
// long currentStepCount = 0;      
// unsigned long lastMoveTime = 0; // Timer for movement steps
// int speedScale = 1;             

// // --- Auto Mode Specific Variables ---
// unsigned long autoTimer = 0;      // Tracks time since last auto-move
// unsigned long autoInterval = 5000; // 5 seconds delay between moves
// int autoState = 0;                // 0 = Waiting, 1 = Moving
// int autoStepsToMove = 0;          // Calculated steps for 15 degrees
// int autoStepIndex = 0;            // Current step index within the move

// void setStep(int a, int b, int c, int d) {
//   digitalWrite(IN1, a);
//   digitalWrite(IN2, b);
//   digitalWrite(IN3, c);
//   digitalWrite(IN4, d);
// }

// void setup() {
//   pinMode(IN1, OUTPUT);
//   pinMode(IN2, OUTPUT);
//   pinMode(IN3, OUTPUT);
//   pinMode(IN4, OUTPUT);
  
//   Serial.begin(9600);
//   while (!Serial) {}; 
  
//   stepInterval = map(speedScale, 1, 50, 1, 100);
  
//   // Calculate steps for 15 degrees once
//   autoStepsToMove = (int)((15.0 / 360.0) * STEPS_PER_REV);
  
//   autoTimer = millis(); // Start the 5s timer immediately
//   Serial.println("System Started.");
//   Serial.println("Current Mode: AUTO (15 degrees every 5 seconds)");
//   Serial.println("Send a number or 's[1-50]' to switch to MANUAL mode.");
// }

// void loop() {
//   // --- 1. SERIAL INPUT PROCESSING (HIGHEST PRIORITY) ---
//   // If ANY input is received, switch to manual mode IMMEDIATELY.
//   if (Serial.available() > 0) {
//     String input = Serial.readString();
//     input.trim();

//     if (input.length() > 0) {
//       if (input.startsWith("s")) {
//         // Handle Speed change
//         int newSpeed = input.substring(1).toInt();
//         if (newSpeed >= 1 && newSpeed <= 50) {
//             speedScale = newSpeed;
//             stepInterval = map(speedScale, 1, 50, 1, 100);
            
//             // If we were moving, stop immediately
//             currentStepCount = targetSteps; 
//             autoStepIndex = autoStepsToMove; // Force auto move to finish logic (or reset)
            
//             Serial.print("Success: Speed set to ");
//             Serial.println(speedScale);
//         } else {
//             Serial.println("Error: Use scale 1-50.");
//         }
//       } else {
//         // Handle Degree change
//         float val = input.toFloat();
//         if (val != 0) {
//           targetSteps = (long)((val / 360.0) * STEPS_PER_REV);
//           currentStepCount = 0; // Reset count to start from zero
//           lastMoveTime = millis();
//           autoMode = false;     // SWITCH TO MANUAL MODE
//           autoState = 0;        // Reset auto state machine
          
//           Serial.print("Switching to Manual Mode. Target: ");
//           Serial.print(val);
//           Serial.println(" degrees.");
//         }
//       }
//     }
//   }

//   // --- 2. EXECUTION LOGIC ---

//   if (autoMode) {
//     /* 
//        NON-BLOCKING AUTO MODE:
//        State Machine:
//        0: Waiting for 5 seconds
//        1: Moving the 15 degrees
//     */
    
//     if (autoState == 0) {
//       // Check if 5 seconds have passed
//       if (millis() - autoTimer >= autoInterval) {
//         autoTimer = millis(); // Reset timer
//         autoState = 1;        // Start moving
//         autoStepIndex = 0;    // Reset step counter for this move
//         lastMoveTime = millis(); // Start the step timer
//       }
//     } 
//     else if (autoState == 1) {
//       // Move one step if enough time passed
//       if (millis() - lastMoveTime >= (unsigned long)stepInterval) {
//         lastMoveTime = millis();
        
//         // Calculate sequence index
//         int seqIdx = autoStepIndex % 8;
//         setStep(stepSequence[seqIdx][0], stepSequence[seqIdx][1], 
//                 stepSequence[seqIdx][2], stepSequence[seqIdx][3]);
        
//         autoStepIndex++;

//         // Check if we finished the 15-degree move
//         if (autoStepIndex >= autoStepsToMove) {
//           autoState = 0; // Back to waiting
//           Serial.println("Auto move complete. Waiting 5s...");
//         }
//       }
//     }
//   } 
//   else {
//     /* 
//        MANUAL MODE:
//        Non-blocking movement toward target.
//     */
//     if (currentStepCount != targetSteps) {
//         if (millis() - lastMoveTime >= (unsigned long)stepInterval) {
//             lastMoveTime = millis();
            
//             // Determine direction
//             long direction = (targetSteps > currentStepCount) ? 1 : -1;
            
//             // Calculate sequence index (handling negative modulo correctly)
//             int seqIdx = (int)((currentStepCount % 8 + 8) % 8);
//             setStep(stepSequence[seqIdx][0], 
//                     stepSequence[seqIdx][1], 
//                     stepSequence[seqIdx][2], 
//                     stepSequence[seqIdx][3]);

//             currentStepCount += direction;
//         }
//     }
//   }
// }