/* University College London Dept of P&A course in C++ 3C59 
| all rights reserved 2000
|
| Module:  Consolidation excercise: 
|
| Title: ComptonAnalysis 
|
| Class: DataReader
|   
| Description:  
|
|     This is an example of a class which performs some well defined service for
|     its client. In this case it is an "IO helper", meaning that its job is to help
|     the client with obtaining input to the program.  
|
|     In this simple example it actually only does one thing, which is to read a file
|     and use it to make a vector of Datum class objects. However it could equally well
|     also implement a method to get datums frome keyboard, or via an http://..
|     connection to some remote web-server. In each case it would still returen a vector
|     of Datum objects to the client.
|
|     To be clear, this is a pretty dumb example purely because it is kep to be about as 
|     short as possible. However the message you are supposed to get from this is:
|
|       classes can be written to provide a set all sorts of services. Classes are not
|       limited to merely representing some piece of data such as a measurement.
|
| Author: P.Clarke 
*/

#ifndef  _datareader_h
#define  _datareader_h 1

#include <cmath>
#include <vector>
#include <iostream>
#include <fstream>
#include <string>

#include "Datum.h"

//-----------------------------------------------
// Here we start the class declaration as normal
  
class DataReader {

  private:

    // In this dump class it doesnt really need anym  private member variables, but
    // they would go here if it did.

  public:


    // --------------------------------------------
    // Beginning of method

    // This method performs the service of returning to the caller a vector
    // of Datum objects. It does this by accessing a file on disk which contains
    // the numbers it needs to make each Datum. It will stick them all into a vector
    // of datum objects and return this as its return argument.

    // It starts with the method signature as normal. 
    // In case this looks strange to you then read it like this (reading left to right) 
    // (i) it will return a vector of Datum objects
    // (ii) it is called readFromFile
    // (iii) it takes one argument which is an object of the string class
    
    std::vector<Datum> readFromFile(  std::string filename ) 
    {

      // Here is the code of the method

      // ...................
      // First make an (empty) vector which we will fill in this method

      std::vector<Datum>  tempStore ;


      // ....................
      // Open an the input file specified as the argument to the method for reading 
      // (the .c_str() is a silly complication which was explained in class)

      std::ifstream  inputFile( filename.c_str() ) ;
      if( ! inputFile ) 
      {
        // Print an error message and return the empty vector
        std::cout << " Error - could not open input file " << filename << std::endl ;
        return tempStore ;
      }


      // ...................
      // Now go through the file, reading each line at a time

      while( inputFile )
      {
        // Read three numbers from one line of the file
        float angle, energy, err ;
        inputFile >> angle >> energy >> err ;

        // Fix up line - explained in class
        if( ! inputFile ) break ;

        // Make a new Datum with them
        Datum tempDatum ;
        tempDatum.initialise( angle, energy, err ) ;

        // Stick it in the vector which was made at beginning of method
        tempStore.push_back( tempDatum ) ;

      }

      // At this point we have filled the vector called tempStore with lots of
      // Datum objects created from the file/ all that remains is to return
      // it to the caller

      return tempStore ;

    } // End of method

};  // End of class

#endif