#include <FS.h>
#include <SD.h>
#include <SPI.h>

#define MIC_PIN 1       // ADC input pin (besser A1 statt 1)
#define BUTTON_PIN 0     // Boot button
#define LED_PIN 38       // Status LED
#define SD_CS 10         // SD card Chip Select

File audioFile;
bool isRecording = false;
bool buttonPressed = false;

const int sampleRate = 22050;  // Sample rate in Hz
unsigned long lastSampleTime = 0;
uint32_t audioDataBytes = 0;
int recordingCount = 1;

// Audio processing variables
int16_t dcOffset = 2048; // DC bias removal (12-bit ADC center)
int16_t lastSample = 0;  // For simple low-pass filtering

// Create WAV file header
void createWavHeader(File &file, uint32_t sampleRate, uint16_t bitsPerSample, uint16_t channels, uint32_t dataSize) {
  file.seek(0);

  // Main RIFF chunk
  file.write((const uint8_t*)"RIFF", 4);
  uint32_t totalSize = 36 + dataSize;
  file.write((uint8_t *)&totalSize, 4);
  file.write((const uint8_t*)"WAVE", 4);

  // Format chunk
  file.write((const uint8_t*)"fmt ", 4);
  uint32_t fmtChunkSize = 16;
  file.write((uint8_t *)&fmtChunkSize, 4);
  uint16_t audioFormat = 1; // PCM
  file.write((uint8_t *)&audioFormat, 2);
  file.write((uint8_t *)&channels, 2);
  file.write((uint8_t *)&sampleRate, 4);
  uint32_t byteRate = sampleRate * channels * bitsPerSample / 8;
  file.write((uint8_t *)&byteRate, 4);
  uint16_t blockAlign = channels * bitsPerSample / 8;
  file.write((uint8_t *)&blockAlign, 2);
  file.write((uint8_t *)&bitsPerSample, 2);

  // Data chunk header
  file.write((const uint8_t*)"data", 4);
  file.write((uint8_t *)&dataSize, 4);
}

void setup() {
  Serial.begin(115200);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  delay(100);

  if (!SD.begin(SD_CS)) {
    Serial.println("Oops! Can't find the SD card. Please check the connection.");
    while (1) {
      digitalWrite(LED_PIN, HIGH);
      delay(200);
      digitalWrite(LED_PIN, LOW);
      delay(200);
    }
  }

  Serial.println("🎤 Audio Recorder Ready!");
  Serial.println("Press the button to start recording, press again to stop.");

  digitalWrite(LED_PIN, HIGH);
  delay(100);
  digitalWrite(LED_PIN, LOW);
}

void loop() {
  handleButtonPress();

  if (isRecording) {
    recordAudioSample();
  }
}

void handleButtonPress() {
  bool currentButtonState = (digitalRead(BUTTON_PIN) == LOW);

  if (currentButtonState && !buttonPressed) {
    buttonPressed = true;
    delay(30); // debounce

    if (!isRecording) {
      beginRecording();
    } else {
      finishRecording();
    }
  } else if (!currentButtonState) {
    buttonPressed = false;
  }
}

void recordAudioSample() {
  unsigned long currentTime = micros();

  if (currentTime - lastSampleTime >= (1000000UL / sampleRate)) {
    lastSampleTime = currentTime;

    int rawSample = analogRead(MIC_PIN);

    int16_t centeredSample = rawSample - dcOffset;

    // Sanfterer Lowpass Filter für ausgewogenen Klang
    centeredSample = (centeredSample * 5 + lastSample * 3) / 8;
    lastSample = centeredSample;

    // Verstärkung anpassen
    int16_t processedSample = centeredSample * 6;

    // Soft limiting
    if (processedSample > 16000) processedSample = 16000;
    if (processedSample < -16000) processedSample = -16000;

    audioFile.write((uint8_t)(processedSample & 0xFF));
    audioFile.write((uint8_t)(processedSample >> 8));
    audioDataBytes += 2;
  }
}

void beginRecording() {
  char fileName[30];
  snprintf(fileName, sizeof(fileName), "/audio_clip_%03d.wav", recordingCount);

  audioFile = SD.open(fileName, FILE_WRITE);
  if (!audioFile) {
    Serial.println("Sorry, couldn't create the audio file. Please try again.");
    return;
  }

  lastSample = 0;

  // DC Offset Kalibrierung
  int32_t offsetSum = 0;
  for (int i = 0; i < 100; i++) {
    offsetSum += analogRead(MIC_PIN);
    delayMicroseconds(100);
  }
  dcOffset = offsetSum / 100;

  // Platzhalter WAV-Header schreiben
  for (int i = 0; i < 44; i++) {
    audioFile.write((uint8_t)0);
  }

  audioDataBytes = 0;
  recordingCount++;
  Serial.println("🔴 Recording started: " + String(fileName));
  Serial.println("DC offset calibrated to: " + String(dcOffset));
  digitalWrite(LED_PIN, HIGH);
  isRecording = true;
}

void finishRecording() {
  isRecording = false;

  createWavHeader(audioFile, sampleRate, 16, 1, audioDataBytes);

  audioFile.close();

  Serial.println("⏹ Recording stopped.");
  Serial.println("File saved successfully!");
  digitalWrite(LED_PIN, LOW);
}