const uint8_t BLUE_PIN  = 9;   // PWM
const uint8_t GREEN_PIN = 10;  // PWM
const uint8_t RED_PIN   = 11;  // PWM
const uint8_t POT_PIN   = A5;  // analog input

// thresholds for dividing potentiometer into thirds
constexpr int T1 = 341;
constexpr int T2 = 682;

// previous printed values for change detection
int prevBlue = -1;
int prevGreen = -1;
int prevRed = -1;

// manual overrides (-1 = follow potentiometer). Values 0..255
int manualBlue = -1;
int manualGreen = -1;
int manualRed = -1;

// serial command buffer
char cmdBuf[64];
size_t cmdIndex = 0;

static inline void printPrompt() {
  Serial.print("> ");
}

static void to_upper_inplace(char *s) {
  for (char *p = s; *p; ++p) {
    if (*p >= 'a' && *p <= 'z') *p = *p - ('a' - 'A');
  }
}

static void trim_trailing_spaces(char *s) {
  size_t n = strlen(s);
  while (n > 0 && (s[n - 1] == ' ' || s[n - 1] == '\t')) {
    s[--n] = '\0';
  }
}

// handle a single segment
void handleSegment(char *seg) {
  trim_trailing_spaces(seg);
  if (seg[0] == '\0') return;

  // extract name (up to first whitespace) and optional value
  char name[16] = {0};
  int value = -1;
  char *p = seg;
  while (*p && *p != ' ' && *p != '\t') ++p;
  size_t n = (size_t)(p - seg);
  if (n >= sizeof(name)) n = sizeof(name) - 1;
  // copy name and uppercase it
  for (size_t i = 0; i < n; ++i) {
    char c = seg[i];
    if (c >= 'a' && c <= 'z') c = c - ('a' - 'A');
    name[i] = c;
  }
  name[n] = '\0';

  if (*p) {
    while (*p == ' ' || *p == '\t') ++p;
    value = atoi(p);
  }

  if (strcmp(name, "BLUE") == 0) {
    manualBlue = constrain(value, 0, 255);
    Serial.print("\r\nManual Blue set to: ");
    Serial.println(manualBlue);
  } else if (strcmp(name, "GREEN") == 0) {
    manualGreen = constrain(value, 0, 255);
    Serial.print("\r\nManual Green set to: ");
    Serial.println(manualGreen);
  } else if (strcmp(name, "RED") == 0) {
    manualRed = constrain(value, 0, 255);
    Serial.print("\r\nManual Red set to: ");
    Serial.println(manualRed);
  } else if (strcmp(name, "AUTO") == 0) {
    manualBlue = manualGreen = manualRed = -1;
    Serial.println("\r\nReturning control to potentiometer");
  } else if (strcmp(name, "HELP") == 0) {
    Serial.println("\r\nCommands:");
    Serial.println("  BLUE <0-255>   - set Blue PWM directly");
    Serial.println("  GREEN <0-255>  - set Green PWM directly");
    Serial.println("  RED <0-255>    - set Red PWM directly");
    Serial.println("  AUTO           - return control to potentiometer");
    Serial.println("  You may send multiple commands separated by commas:");
    Serial.println("    e.g. BLUE 255,GREEN 128,RED 0");
  } else {
    Serial.print("\r\nUnknown command: '");
    Serial.print(name);
    Serial.println("'. Type HELP for usage.");
  }
}

// process a full command line which may contain comma-separated segments
void processCommand(const char *cmd) {
  if (!cmd || !*cmd) return;
  const char *p = cmd;
  while (*p) {
    // skip leading whitespace
    while (*p == ' ' || *p == '\t') ++p;
    if (!*p) break;

    // find segment end
    const char *end = p;
    while (*end && *end != ',') ++end;

    // copy into local buffer
    char seg[48];
    size_t len = (size_t)(end - p);
    if (len >= sizeof(seg)) len = sizeof(seg) - 1;
    strncpy(seg, p, len);
    seg[len] = '\0';

    // trim leading spaces
    char *segStart = seg;
    while (*segStart == ' ' || *segStart == '\t') ++segStart;
    if (segStart != seg) memmove(seg, segStart, strlen(segStart) + 1);

    trim_trailing_spaces(seg);

    if (seg[0] != '\0') handleSegment(seg);

    // advance past comma if present
    p = end;
    if (*p == ',') ++p;
  }

  printPrompt();
}

void setup() {
  delay(200);
  Serial.begin(9600);

  Serial.println("\n\nPotentiometer RGB with Serial Control (manual: 0-255)");
  printPrompt();

  pinMode(BLUE_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(RED_PIN, OUTPUT);
}

void loop() {
  // ---- Serial input + echo + backspace ----
  while (Serial.available()) {
    int c = Serial.read();
    if (c == '\r') continue; // ignore CR

    // Backspace or DEL
    if (c == 8 || c == 127) {
      if (cmdIndex > 0) {
        cmdIndex--;
        Serial.print("\b \b");
      }
      continue;
    }

    // Newline -> process command line
    if (c == '\n') {
      cmdBuf[cmdIndex] = '\0';
      Serial.println();
      processCommand(cmdBuf);
      cmdIndex = 0;
      continue;
    }

    // Printable char -> buffer + echo
    if (c >= 32 && c <= 126) {
      if (cmdIndex < sizeof(cmdBuf) - 1) {
        cmdBuf[cmdIndex++] = (char)c;
        Serial.write((char)c);
      }
    }
  }

  // ---- Read pot and compute PWM ----
  int potValue = analogRead(POT_PIN);

  int blueBrightness;
  if (manualBlue >= 0) {
    blueBrightness = manualBlue;
  } else {
    if (potValue <= T1) {
      // scale (0..T1) -> (0..255)
      blueBrightness = (uint32_t)potValue * 255 / T1;
    } else {
      blueBrightness = 0;
    }
  }

  int greenBrightness;
  if (manualGreen >= 0) {
    greenBrightness = manualGreen;
  } else {
    if (potValue > T1 && potValue <= T2) {
      greenBrightness = (uint32_t)(potValue - T1) * 255 / (T2 - T1);
    } else {
      greenBrightness = 0;
    }
  }

  int redBrightness;
  if (manualRed >= 0) {
    redBrightness = manualRed;
  } else {
    if (potValue > T2) {
      redBrightness = (uint32_t)(potValue - T2) * 255 / (1023 - T2);
    } else {
      redBrightness = 0;
    }
  }

  analogWrite(BLUE_PIN, blueBrightness);
  analogWrite(GREEN_PIN, greenBrightness);
  analogWrite(RED_PIN, redBrightness);

  // ---- Print changed values with small hysteresis ----
  bool anyPrinted = false;
  if (abs(blueBrightness - prevBlue) > 3) {
    Serial.print("\r\nBlue LED PWM: ");
    Serial.println(blueBrightness);
    prevBlue = blueBrightness;
    anyPrinted = true;
  }
  if (abs(greenBrightness - prevGreen) > 3) {
    Serial.print("\r\nGreen LED PWM: ");
    Serial.println(greenBrightness);
    prevGreen = greenBrightness;
    anyPrinted = true;
  }
  if (abs(redBrightness - prevRed) > 3) {
    Serial.print("\r\nRed LED PWM: ");
    Serial.println(redBrightness);
    prevRed = redBrightness;
    anyPrinted = true;
  }
  if (anyPrinted) printPrompt();

  delay(50);
}