/**
* This program reads a random access file sequentially,
* updates data already written to the file, creates new
* data to be placed in the file, and deletes data
* already in the file.
*/
#include <stdio.h>
struct clientData {
    int acctNum;
    char lastName[ 15 ];
    char firstName[ 10 ];
    double balance;
};
int enterChoice( void );
void textFile( FILE * );
void updateRecord( FILE * );
void newRecord( FILE * );
void deleteRecord( FILE * );

int main()
{
    FILE *cfPtr;
    int choice;
    if ( ( cfPtr = fopen( "credit.dat", "r+b" ) ) == NULL ) printf( "File could not be opened.\n" );
    else {
        while ( ( choice = enterChoice() ) != 5 ) {
            switch ( choice ) {
                case 1: textFile( cfPtr ); break;
                case 2: updateRecord( cfPtr );break;
                case 3: newRecord( cfPtr );break;
                case 4: deleteRecord( cfPtr );break;
            }
        }
        fclose( cfPtr );
    }
    return 0;
}
void textFile( FILE *readPtr )
{
    FILE *writePtr;
    struct clientData client = { 0, "", "", 0.0 };
    if ( ( writePtr = fopen( "accounts.txt", "wt" ) ) == NULL ) printf( "File could not be opened.\n" );
    else {
        rewind( readPtr );
        fprintf( writePtr, "%-6s%-16s%-11s%10s\n", "Acct", "Last Name", "First Name","Balance" );
        while ( !feof( readPtr ) ) {
            fread( &client, sizeof( struct clientData ), 1, readPtr );
            if ( client.acctNum != 0 )
                fprintf( writePtr, "%-6d%-16s%-11s%10.2f\n", client.acctNum, client.lastName, client.firstName, client.balance );
        }
        fclose( writePtr );
    }
}

void updateRecord( FILE *fPtr )
{
    int account;
    double transaction;
    struct clientData client = { 0, "", "", 0.0 };

    printf( "Enter account to update ( 1 - 100 ): " );
    scanf( "%d", &account );
    fseek( fPtr, ( account - 1 ) * sizeof( struct clientData ), SEEK_SET );
    fread( &client, sizeof( struct clientData ), 1, fPtr );
    if ( client.acctNum == 0 )
    printf( "Acount #%d has no information.\n", account );
    else {
        printf( "%-6d%-16s%-11s%10.2f\n\n",client.acctNum, client.lastName,client.firstName, client.balance );
        printf( "Enter charge ( + ) or payment ( - ): " );
        scanf( "%lf", &transaction );
        client.balance += transaction;
        printf( "%-6d%-16s%-11s%10.2f\n",client.acctNum, client.lastName,client.firstName, client.balance );
        fseek( fPtr,( account - 1 ) * sizeof( struct clientData ),SEEK_SET );
        fwrite( &client, sizeof( struct clientData ), 1,fPtr );
    }
}

void deleteRecord( FILE *fPtr )
{
    struct clientData client,
    blankClient = { 0, "", "", 0 };
    int accountNum;
    printf( "Enter account number to delete ( 1 - 100 ): " );
    scanf( "%d", &accountNum );
    fseek( fPtr, ( accountNum - 1 ) * sizeof( struct clientData ), SEEK_SET );
    fread( &client, sizeof( struct clientData ), 1, fPtr );
    if ( client.acctNum == 0 )
    printf( "Account %d does not exist.\n", accountNum );
    else {
        fseek( fPtr, ( accountNum - 1 ) * sizeof( struct clientData ), SEEK_SET );
        fwrite( &blankClient, sizeof( struct clientData ), 1, fPtr );
    }
}

void newRecord( FILE *fPtr )
{
    struct clientData client = { 0, "", "", 0.0 };
    int accountNum;

    printf( "Enter new account number ( 1 - 100 ): " );
    scanf( "%d", &accountNum );

    fseek( fPtr,( accountNum - 1 ) * sizeof( struct clientData ),SEEK_SET );

    fread( &client, sizeof( struct clientData ), 1, fPtr );

    if ( client.acctNum != 0 )
    printf( "Account #%d already contains information.\n", client.acctNum );
    else {
        printf( "Enter lastname, firstname, balance\n? " );
        scanf( "%s%s%lf", &client.lastName, &client.firstName, &client.balance );
        client.acctNum = accountNum;

        fseek( fPtr, ( client.acctNum - 1 ) * sizeof( struct clientData ), SEEK_SET );
        fwrite( &client, sizeof( struct clientData ), 1, fPtr );
    }
}
int enterChoice( void )
{
    int menuChoice;
    printf( "\nEnter your choice\n 1 - store a formatted text file of acounts called\n \"accounts.txt\" for printing\n 2 - update an account\n3 - add a new account\n4 - delete an account\n5 - end program\n? " );
    scanf( "%d", &menuChoice );
    return menuChoice;
}