// CS1320-5
// 1999 Oct 28
// scribed by Geoffrey Derber and Jeffrey D. Oldham

// N-Way Merge Program

// This program merges the lines of files together, sending them to
// the standard output.

// The program repeatedly prints one line from each of the files
// specified on the command line.  For example, if the files specified 
// on the command line are file0, file1, file2, and file2, it produces 
// the following output:
// first line of file0
// first line of file1
// first line of file2
// first line of file3
// second line of file0
// second line of file1
// second line of file2
// second line of file3
// ...

// If a file contains no more lines, it does not affect the output.
// If no files are specified, the program produces no output.

#include<iostream.h>
#include<stdlib.h>
#include<fstream.h>

int main(int argc, char *argv[]) // the file names are argv[1], ...,
				// argv[argc-1]
{
  // The main data structure!
  // We will use an array of file streams.
  // The ifstream file_list[i] corresponds to the file with name
  //  argv[i+1].
  ifstream file_list[1000];
  for(int x=0;x<argc-1;++x)
    {
      file_list[x].open(argv[x+1]);
      if(file_list[x].fail()) {
	cout<<"error"<<endl;
	exit(1);
      }
    }

  // CP: Read the contents of the files in the appropriate order.
  // CP: Print out the lines interleaved.
  char line[1000];
  bool printedLine;
  do {				// Added by JDO.
    printedLine = false;	// Added by JDO
    for(int x=0; x<argc-1;x++)
      // JJ: use getline() to obtain the lines
      if(file_list[x].getline(line,1000)) {
	cout<<line<<endl;
	printedLine = true;	// Added by JDO
      }
  } while (printedLine);	// Added by JDO

  // The code presented in class was almost correct, but it just
  // printed the first line from each file.  We had to wrap it in a
  // loop that continues as long as some file still has lines. JDO

  // Close up all the file streams.
  for(int x=0;x<argc;++x)
    file_list[x].close();

  return 0;
}