/* 
 * 
 * CSI2131
 * 
 * Jeff Souza 
 * 
 * Lab7
 * 
 */

#include <iostream>
#include <string>
#include <fstream>
#include <iomanip>     // for setw, setiosflags, etc...
using namespace std;

// the number of records to read in
const int num_records = 10;
// the number of fields in each record
const int num_fields = 5;
// the length of the record length indicator
const int length_ind_size = 2;

// output length for each field 
const int output_lengths[] = {12,12,5,3,4};


// read a record by its RRN
string readRecordbyRRN(int, istream&);

// write a record using the report format
void writeRecord(string, ostream&);



// main method
int main( )
{
  
  fstream input;                      // input stream
  fstream output;                     // output stream
  string rec;

  char inputname[40];                 // input filename
  char outputname[40];                // output filename

  cout << "What is the input file name? ";
  cin >> inputname;

  cout << "What is the output (report) file name? ";
  cin >> outputname;

  
  // open the input file for input, of course
  input.open(inputname, ios::in);

  // Check to make sure that we could open the files properly!
  if (input.fail()) {
    cerr << "Could not open file ";
    cerr << inputname;
    cerr << ".\n";
    return 1;
  }


  // open the output for output
  output.open(outputname, ios::out);

  // outout the header of the report
  output << "LAST NAME    FIRST NAME   MONTH DAY YEAR" << endl;
  output << "------------ ------------ ----- --- ----" << endl;

  // reads records in reverse order and copy the in output 
  for (int i=num_records-1;i>=0; i--){
        rec = readRecordbyRRN(i, input);
        writeRecord(rec, output);  
  }

  cout << endl << "Program completed successfully !!" << endl;
  cout << "Check output file out." << endl << endl;

  input.close();
  output.close();

  return 0;
}

// read a student from a istream by its RRN
string readRecordbyRRN(int rrn, istream& input)
{
  
    char ind[length_ind_size];    // stores the length indicator digits
    int rec_size;                 // stores the length indicator
    string record = "";           // the record to be returned
    char aux;                     // auxiliar char

    input.seekg(0, ios::beg);     // move read pointer to the beginning

    // read the length indicator and store it in rec_size
    input >> ind[0];
    input >> ind[1];
    rec_size = atoi(ind);

    // keep reading lenght indicator and skipping records 
    for (int i=1;i<=rrn;i++){
        input.seekg(rec_size-2, ios::cur);
        input >> ind[0];
        input >> ind[1];
        rec_size = atoi(ind);
    }

    // read the record chars
    for (int j=0;j<rec_size-2;j++){
        input >> aux;
        record = record + aux;
    }

    // return the record
    return record;
}

// write a student in the ostream
void writeRecord(string r, ostream& output)
{
    string c, aux;          // auxiliar strings
    int j=-1;                
    
    // read all fields in the record
    for (int i=0;i<num_fields;i++){
        j++;    
        aux = "";
        c = r.substr(j,1);
        // read chars and concatenate them until gets a "|"
        while (c!= "|"){
            aux = aux + c;
            j++;
            c = r.substr(j,1);
        }
        // output the field by using its output size (sizes[i])
        output << setw(output_lengths[i]+1) << setiosflags(ios::left) << aux;
    }

    output << endl;
}