/****************************************************************************
Project: 4
Class: CEG 221
File Name: Project4p2
Instructor: DeJongh
Due Date: May 28th
Overview: This program ultilizes a menu that allows the user to open binary files with
          data of type STR in them, and to then preform various tasks on the files.
Program Structure: This program loops a menu for the user to preform various tasks.
                   The first option is to simply open a binary file. The second option is
                   to count the number of records in the file. The third option is to
                   print all the records in the file
****************************************************************************/
#include <stdio.h>

typedef struct
{
        int data;
        char name[15];
}STR;

void openFile(FILE **fptr); //function prototypes
int recCount(FILE *fptr);
void printFile(FILE *fptr);
void printRec(FILE *fptr);
void changeRec(FILE *fptr);
void addRec(FILE *fptr);
void closeFile(FILE *fptr);


int main(void)
{
    int option;
    FILE *fptr = NULL;

    while(option != 8){
        printf("\tMenu\n");   //main menu for the user to select cases
        printf("1. Open File\n");
        printf("2. Count Records\n");
        printf("3. Print Records\n");
        printf("4. Print nth record\n");
        printf("5. Change the nth record\n");
        printf("6. Add a record at the end\n");
        printf("7. Close the file\n");
        printf("8. Exit\n");

        printf("\nInput: ");
        fflush(stdin);
        scanf("%d",&option); //user propmt for menu option
        printf("\n");

        switch (option) {          //switch statement that allows user to choose file manipulation
             case 1: openFile(&fptr);
                     break;
             case 2: printf("There are %d records in this file.\n",recCount(fptr));
                     break;
             case 3: printFile(fptr);
                     break;
             case 4: printRec(fptr);
                     break;
             case 5: changeRec(fptr);
                     break;
             case 6: addRec(fptr);
                     break;
             case 7: closeFile(fptr);
                     fptr = NULL;
                     break;
             case 8: break;
             default: printf("Invalid menu selection.\n");
             }
        system("pause");
        system("cls");
    }//end while


    printf("Thank you for using my program.\n");
    system("pause");
    return 0;
}//end main
/*******************************************************************
This function simply opens a binary file for reading and writing later on.

Outputs: it does not return anything but sets the file pointer ftpr to the opened file
********************************************************************/
void openFile(FILE **fptr)
{
     char filename[25];

     do
     {
       printf("Enter file name to open: ");
       scanf("%s",filename);//user propmt to open the desired file

       *fptr = fopen(filename,"r + b");
       if(*fptr == NULL) //tests to see if if file opening was successful or not
                printf("The file was not found.\n");
     }while(*fptr == NULL);

     printf("The file was opened.\n");

}
/*******************************************************************
This function counts the number of records in the file that was read. It does this by
seeking the file postion marker to the end of the file, taking the number of bytes in the file
and then dividing it but the size of the data type STR to determine the number of records.

Outputs: and integer number, which is how many records there are in the file
********************************************************************/
int recCount(FILE *fptr) //counts the number of integers in the file
{
    int filesize;

    if(fptr == NULL){
            printf("No file is currently open.\n");
            return;
            }

    filesize = fseek(fptr,0,SEEK_END); //set position pointer to end of the file
    filesize = (ftell(fptr) + 1)/sizeof(STR);
         //determine the number of records by dividing the total number of bytes by the size of STR
    return filesize;
}
/*******************************************************************
This function prints all the records in the file that was opened by the openFile function

Outputs: prints out all of the records in the file, the integer and the string values
         in a list with their corresponding record number
********************************************************************/
void printFile(FILE *fptr)
{
     int recNum = 0;
     STR record;

     if(fptr == NULL){ //tests to see if a file has been opened
            printf("No file is currently open.\n");
            return;
            }

     fseek(fptr,0,SEEK_SET); //set file position mark to end
     fread(&record, sizeof(STR),1,fptr); //read the first value in the file
     while(!feof(fptr))
     {
         printf("Record %2d: %3d  %3s\n",recNum++,record.data,record.name);
         fread(&record,sizeof(STR),1,fptr); //reads the next value in the function with each iteration
     }
}
/*******************************************************************
This function prints the nth record in the file. The record that is printed is input by
the user.

Outputs: the nth record in the file which was determined by the user
********************************************************************/
void printRec(FILE *fptr)//prints the desired nth record in the file
{
    int filesize,nth;
    STR record;
    fpos_t pos;

    if(fptr == NULL){ //checks to see if a file was opened
            printf("No file is currently open.\n");
            return;
            }

    filesize = fseek(fptr,0,SEEK_END); //put position poiner at end of file
    filesize = (ftell(fptr) + 1)/sizeof(STR);

    do
    {
    printf("Please enter the nth Record you would like to print(1...%d): ",filesize);
    scanf("%d",&nth); //user prompt for the nth record
    if(!(nth >0 && nth <= filesize)) //checks to see if the record is valid
             printf("There is no %dth Record.\n",nth);
    }while(!(nth >0 && nth <= filesize));

    pos = (nth - 1) * sizeof(STR); //1 corresponds to the 0 value of the file

    fsetpos(fptr,&pos); //set postion pointer
    fread(&record, sizeof(STR),1,fptr); //read the integer

    printf("The %dth Record is %d %s\n",nth,record.data,record.name);
}
/*******************************************************************
This function changes the nth record which is input by the user. It allows them to
pick which record they would like to change, and also allows them to change each
individual part of the record.

Outputs: it changes the desired file and then tells them that the record was changed
********************************************************************/
void changeRec(FILE *fptr)
{
    int filesize,nth,newdata;
    STR record;
    fpos_t pos;

    if(fptr == NULL){ //checks to see if a file was opened
            printf("No file is currently open.\n");
            return;
            }

    filesize = fseek(fptr,0,SEEK_END); //put position poiner at end of file
    filesize = (ftell(fptr) + 1)/sizeof(STR);
    do
    {
    printf("Please enter the nth Record you would like to change (1...%d): ",filesize);
    scanf("%d",&nth); //user input for the desired record to change
    if(!(nth >0 && nth <= filesize))
             printf("There is no %dth Record.\n",nth);
    }while(!(nth >0 && nth <= filesize));

    pos = (nth - 1) * sizeof(STR); //1 corresponds to the 0 value of the file
    fsetpos(fptr,&pos); //set postion pointer

    printf("Please enter the new integer data you would like to input: ");
    scanf("%d",&record.data); // user propmt for new int data

    printf("Please enter the new string data you would like to input: ");
    scanf("%s",&record.name);//user prompt for new string data

    fwrite(&record, sizeof(STR), 1, fptr); //writes the new data into the target file

    printf("The new data was written.\n");
}
/*******************************************************************
This function adds are record to the end of the file. It propmts the user for the
new data and then writes it to the end of the file

Outputs: adds a new record to the end of the file
********************************************************************/
void addRec(FILE *fptr)
{
    int filesize,newdata;
    STR record;
    fpos_t pos;

    if(fptr == NULL){
            printf("No file is currently open.\n");
            return;
            }

    filesize = fseek(fptr,0,SEEK_END); //put position poiner at end of file
    filesize = (ftell(fptr) + 1)/sizeof(STR);

    printf("Enter the integer data you would like to input at the end of the file: ");
    scanf("%d",&record.data); //first user prompt for new int data
    printf("Enter the string data you would like to input at the end of the file: ");
    scanf("%s",&record.name);//second user prompt for new string data

    fwrite(&record, sizeof(STR), 1, fptr); //writes the new data to the end of the file

}
/*******************************************************************
This function closes the file

Outputs: closes the file and then tells the user if it was closed or an error occured
********************************************************************/
void closeFile(FILE *fptr)
{
     if(fclose(fptr)==0)
           printf("The file was closed.\n");
     else
           printf("An error occured\n");

}