//#include <SPI.h>
#include <Adafruit_GFX.h>                             // graphics library for display
#include <Adafruit_SSD1306.h>                         // SSD1306 OLED display library
#include <SD.h>                                       // SD card library
#include "fix_fft.h"                                  // fixed point Fast Fourier Transform library                    
//#include "TMRpcm.h"                                   // For reading WAV audio files



#ifdef __arm__
// should use uinstd.h to define sbrk but Due causes a conflict
extern "C" char* sbrk(int incr);
#else  // __ARM__
extern char *__brkval;
#endif  // __arm__


#define OLED_RESET -1                                  // OLED library likes to see this but it isn't used here with I2C
#define OLED_ADDR 0x3C                                // OLED I2C address
#define audioIn A0                                    // audio input port
#define CS_PIN 10                                     // sd card setup


File root;
Adafruit_SSD1306 display(OLED_RESET);                 // create instance of OLED display
//TMRpcm audio;


void setup() {
   
                         // or 3.3 volts (on 3.3V Arduino boards)


  Serial.begin(9600);

  Serial.print("Initializing SD card... ");

  if (!SD.begin(CS_PIN)) {
    Serial.println("Card initialization failed!");
    while (true);
  }

  Serial.println("INIT DONE");
/*
  Serial.println("Files in the card:");
  root = SD.open("/");
  printDirectory(root, 0);
  Serial.println("FINISHED SETUP");*/


  printfreeMem(0);
   
  /*
  // Example of reading file from the card:
  File textFile = SD.open("README.txt");
  if (textFile) {
    Serial.print("README.txt: ");
    while (textFile.available()) {
      Serial.write(textFile.read());
    }
    textFile.close();
  } else {
    Serial.println("error opening README.txt!");
  }*/
                         // use the default analog reference of 5 volts (on 5V Arduino boards)
  printfreeMem(1);

 // initialize OLED display with address 0x3C for 128x64
  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println(F("SSD1306 allocation failed"));
    while (true);
  }


  delay(2000);         // wait for initializing

  display.clearDisplay();                             // blank the display
  display.setTextSize(1);                             // configure text properties
  display.setTextColor(WHITE);
  analogReference(DEFAULT);  

  //audio.speakerPin = 0;  // set speaker output to pin 9                             
 
  //audio.setVolume(5);    //   0 to 7. Set volume level
  //audio.quality(1);      //  Set 1 for 2x oversampling Set 0 for normal
  
}


//MEMORY LIMITATIONS???
//https://forum.arduino.cc/t/arduino-uno-ssd1306-allocation-failed-need-help-downsizing/604698/5
//https://cdn-learn.adafruit.com/downloads/pdf/memories-of-an-arduino.pdf
// https://www.instructables.com/Playing-Wave-file-using-arduino/
// https://simple-circuit.com/arduino-wave-audio-player-sd-card/



void loop() {


  // The FFT real/imaginary data are stored in a char data type as a signed -128 to 127 number
  // This allows a waveform to swing centered around a 0 reference data point
  // The ADC returns data between 0-1023 so it is scaled to fit within a char by dividing by 4 and subtracting 128.
  // eg (0 / 4) - 128 = -128 and (1023 / 4) - 128 = 127

   char re[16], im[16];                                // real and imaginary FFT result arrays
   byte ylim = 60; 

   printfreeMem(3);

  /*if ( !audio.isPlaying() ) {
      File entry = SD.open("msg.wav");
      audio.play( entry.name() );      // play the audio file
      Serial.print("Playing file: ");
      Serial.println( entry.name() );
  }*/
/*
  for (byte i = 0; i < 16; i++) {                    // read 128 analog input samples from ADC
    int sample = analogRead(audioIn);
    re[i] = sample / 4 - 128;                         // scale the samples to fit within a char variable
    im[i] = 0;                                        // there are no imaginary samples associated with the time domain so set to 0
  };

  printfreeMem(4);

  //fix_fft(re, im, 7, 0);                              // send the samples for FFT conversion, returning the real/imaginary results in the same arrays

  printfreeMem(5);


  display.clearDisplay();                             // clear display
  display.setCursor(0, 0);                            // set cursor to top left corner of the display
  display.print("Audio Spectrum by Shreya");                    // print a header on the top row of the display

   delay(2000);         // wait for initializing

  // The data array will contain frequency bin data in locations 0..127 for samples up to the sampling frequency of approx. 9 KHz
  // Each frequency bin will represent a center frequency of approximately (9 KHz / 128 samples) = 70 Hz
  // Due to Nyquist sampling requirements, we can only consider sampled frequency data up to (sampling rate / 2) or (9 KHz / 2) = 4.5 KHz
  // Therefore we only acknowledge the first 64 frequency bins [0..63] = [0..4.5KHz]

  for (byte i = 0; i < 64; i++) {
    int dat = sqrt(re[i] * re[i] + im[i] * im[i]);     // frequency magnitude is the square root of the sum of the squares of the real and imaginary parts of a vector
    display.drawLine(i * 2, ylim, i * 2, ylim - dat, WHITE); // draw bars for each frequency bin from 0 Hz to 4.5 KHz
  };

  display.display();                                   // update the display
 */
/*
  display.clearDisplay();                             // clear display
  display.setCursor(0, 0);                            // set cursor to top left corner of the display
  display.print("Audio Spectrum");                    // print a header on the top row of the display
  display.display();                                   // update the display
*/
}; 
/*
void printDirectory(File dir, int numTabs) {
  while (true) {

    File entry =  dir.openNextFile();
    if (! entry) {
      // no more files
      break;
    }
    for (uint8_t i = 0; i < numTabs; i++) {
      Serial.print('\t');
    }
    Serial.print(entry.name());
    if (entry.isDirectory()) {
      Serial.println("/");
      printDirectory(entry, numTabs + 1);
    } else {
      // files have sizes, directories do not
      Serial.print("\t\t");
      Serial.println(entry.size(), DEC);
    }
    entry.close();
  }
};*/

void printfreeMem(int index) {
   Serial.print("Freemem ");
   Serial.print(index);
   Serial.print(": ");
   Serial.println(freeMemory());
}

int freeMemory() {
  char top;
#ifdef __arm__
  return &top - reinterpret_cast<char*>(sbrk(0));
#elif defined(CORE_TEENSY) || (ARDUINO > 103 && ARDUINO != 151)
  return &top - __brkval;
#else  // __arm__
  return __brkval ? &top - __brkval : &top - __malloc_heap_start;
#endif  // __arm__
}