/***************************** MIDIFreqDif ********************************************************
 *  MIDIFreqDif                                                                                         *
 *  ====================                                                                                *
 *                                                                                                      *
 *  By: Beau Wright                                                                                     *
 *                                                                                                      *
 *  Description:                                                                                        *
 *  ------                                                                                              *
 *  This program takes the input of two MIDI note numbers between 0 and 127 and computes the            *
 *  frequency difference between them. It can also output a Csound file with the audible sweep between  *
 *  the two frequencies.                                                                                *
 *                                                                                                      *
 ********************************************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>

int acceptAndValidateInput (unsigned int which);
double calculateFrequency(int note);
void printToFile(double f1, double f2);

int main()
{
    int note1,note2, answer;
    double f1,f2,dif;

    /*Takes in values for MIDI notes and checks to make sure
     they are valid (between 0 and 127). It will ask the user again for valid numbers
     if they are not in this range.*/
    note1 = acceptAndValidateInput(1);
    note2 = acceptAndValidateInput(2);
    f1 = calculateFrequency(note1);
    f2 = calculateFrequency(note2);

    /*dif (difference) is first entered note's frequency (f1)
     subtracted from the second entered note's frequency (f2).*/
    dif = f1 - f2;
    if (dif < 0)
    {
        dif *= -1;
    }
    printf("\nThe difference in frequency is %f Hz\n", dif);

    /*Now asking the user to save a Csound file or exit*/
    printf("\nEnter 1 to save as a Csound file, enter 2 to exit ");
    scanf("%d", &answer);

    if (answer == 1)
        printToFile(f1, f2);
    return 0;
}

/**
 * Takes in values for MIDI notes and checks to make sure
 * they are valid (between 0 and 127). It will ask the user again for valid numbers.
 * If valid, this will return the note entered.
 */
int acceptAndValidateInput(unsigned int which)
{
    int note;
    while (1)
    {
        printf("Please enter MIDI note #%u (0-127): ", which);
        scanf("%d", &note);
        if (note < 0 || note > 127)
            printf("The value entered was invalid. Try again.\n");

        else
            return note;
    }
}

/**
 * Calculates a note's frequency using the formula to calculate frequency from MIDI notes.
 */
double calculateFrequency(int note)
{
    double frequency, exponent;

    /*Here is the formula for calculating frequency from MIDI notes. First we find the exponent.*/
    exponent = (note - 69)/12.0;

    // Now, calculate the actual frequency
    frequency = pow(2, exponent) * 440;

    return frequency;
}

/**
 * Prints to a Csound file and replaces the proper frequency variables with the input
 */
void printToFile(double f1, double f2)
{
    /*Case 1 prints to a Csound file and replaces the proper frequency variables with the input from above*/
    char csdFileName[256];
    printf("\nEnter a name for your new csd file (excluding \".csd\"): ");
    scanf("%s", csdFileName);
    strcat(csdFileName, ".csd");
    FILE *csdFilePointer = fopen(csdFileName, "w");
    if(csdFilePointer)
    {
        fprintf(csdFilePointer, "\n<CsoundSynthesizer>\n");
        fprintf(csdFilePointer, "\n<CsInstruments>\n");
        fprintf(csdFilePointer, "\nsr       =       44100");
        fprintf(csdFilePointer, "\nkr       =       4410\n");
        fprintf(csdFilePointer, "\nksmps    =       10\n");
        fprintf(csdFilePointer, "nchnls =       1\n");
        fprintf(csdFilePointer, "\ninstr 1\n");
        fprintf(csdFilePointer, "\nkgliss linseg p5, p3, p6");
        fprintf(csdFilePointer, "\nkamp linseg, 0, p3/2, p4, p3/2, 0\n");
        fprintf(csdFilePointer, "\na1   oscil   kamp, kgliss,   1\n");
        fprintf(csdFilePointer, "\nout   a1\n");
        fprintf(csdFilePointer, "\nendin\n");
        fprintf(csdFilePointer, "\n</CsInstruments>\n");
        fprintf(csdFilePointer, "\n<CsScore>\n");
        fprintf(csdFilePointer, "\nf1   0   4096  10   1 .8 .7 .6 .5 .4 .3\n");
        fprintf(csdFilePointer, "\n     ;amp    ;freq1    ;freq2\n");
        fprintf(csdFilePointer, "\ni1 0 6   10000    %f      %f\n",f1, f2);
        fprintf(csdFilePointer, "\n</CsScore>\n");
        fprintf(csdFilePointer, "\n</CsoundSynthesizer>\n");
    }
    fclose(csdFilePointer);
    printf("\nThe Csound file has been saved to the same directory as this program\n");
    else
    {
        printf("Writing to file failed. :(\n");
    }
}