#include <iostream>
#include <fstream>
#include <string>

using namespace std;



void copy();
void cat();
void display();
void outputFile( istream & in, ostream & out );
bool checkIfFileExists( string name );
int main( int argc, char * argv[] )
{

  // Display the menu
  bool flag = true;
  while( flag ) {
    cout << "1: Copy File\n" << "2: Concatenate File\n" << "3: Display File\n" << "4: Exit" << endl;
    cout << "Option: " << flush;
    int option;
    cin >> option;

    switch( option )
      {
      case 1:
	copy();
	break;
      case 2:
	cat();
	break;
      case 3:
	display();
	break;
      default:
	flag = false;
      }

  }

  return 0;
}

// Outputs a file to the specified ostream object. An ofstream is a child
// of the ostream, hence it can be used in place of the out object
void outputFile( istream & in, ostream & out )
{
  // Each stream must be open before calling this function
  string line;
  while( getline(in, line) ) {
    out << line << endl;
  }
}


void copy()
{
  // Needs to ask for the names of the files to use
  string inFilename, outFilename;
  cout << "Enter the source filename: " << flush;
  cin >> inFilename;
  cout << "Enter the destination filename: " << flush;
  cin >> outFilename;

  // Open the source file and check to see that it opened properly
  ifstream in( inFilename.c_str() );
  if( !in.is_open() ) {
    cout << "Error: cannot open file: " << inFilename << endl;
    return;
  }

  if( checkIfFileExists(outFilename) ) {
    // The file exists and the user does not wish to overwrite the file
    in.close();
    cout << "Not opening file for writing" << endl;
    return;
  }

  ofstream out( outFilename.c_str() );
  if( !out.is_open() ) {
    cout << "Error opening file: " << outFilename << endl;
    return;
  }

  // Call the function to output the infile to the outfile
  outputFile( in, out );

  // Must close all files
  in.close();
  out.close();
}


void cat()
{
  // Needs to ask for the names of the files to use
  string inFilename1, inFilename2, outFilename;
  cout << "Enter the source number 1 filename: " << flush;
  cin >> inFilename1;
  cout << "Enter the source number 2 filename: " << flush;
  cin >> inFilename2;
  cout << "Enter the destination filename: " << flush;
  cin >> outFilename;

  // Open the source file and check to see that it opened properly
  ifstream in1( inFilename1.c_str() );
  if( !in1.is_open() ) {
    cout << "Error: cannot open file: " << inFilename1 << endl;
    return;
  }
  ifstream in2( inFilename2.c_str() );
  if( !in2.is_open() ) {
    cout << "Error: cannot open file: " << inFilename2 << endl;
    return;
  }

  if( checkIfFileExists(outFilename) ) {
    // The file exists and the user does not wish to overwrite the file
    in1.close();
    in2.close();
    return;
  }

  ofstream out( outFilename.c_str() );
  if( !out.is_open() ) {
    cout << "Error opening file: " << outFilename << endl;
    return;
  }

  // Call the function to output the first source file to the outfile
  outputFile( in1, out );

  // Call the function to output the second source file to the outfile
  outputFile( in2, out );

  // Remember to close all the files
  in1.close();
  in2.close();
  out.close();
}


void display()
{
  // Needs to ask for the name of the file to use
  string inFilename;
  cout << "Enter the source filename: " << flush;
  cin >> inFilename;

  // Open the source file and check to see that it opened properly
  ifstream in( inFilename.c_str() );
  if( !in.is_open() ) {
    cout << "Error: cannot open file: " << inFilename << endl;
    return;
  }
  // Call the function to output the infile to the screen.
  // Notice the use of 'cout'. cout is an instance of the class 'istream'
  // so it can be used within this function
  outputFile( in, cout );

  // Close the input file
  in.close();
}

bool checkIfFileExists( string name )
{
  // Check for the existence of the output file
  ifstream tempOut( name.c_str() );
  if( tempOut.is_open() ) {
    // The file exists already
    tempOut.close();
    cout << "The file " << name << " already exists. Do you want to overwrite the file? (y/n)" << endl;

    string answer;
    cin >> answer;


    if( answer[0] == 'y' ) {
      return false;
    }
    else {
      return true;
    }
  }
  else {
    tempOut.close();
    return false;
  }
}