#ifndef INPUT_WRAPPER_H
#define INPUT_WRAPPER_H

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

class InputWrapper {
 private:
    std::streambuf *inbuf;
    std::ifstream fin;

 public:
 InputWrapper(int argc, const char* argv[]) : inbuf(NULL) {
	if (argc>1) {
	    fin.open(argv[1]);
	    if (fin.is_open()) {
		inbuf = std::cin.rdbuf(fin.rdbuf());
	    } else {
		std::cout << "Input file '" << argv[1] << "' not found.\n";
		std::cout << "Defaulting to keyboard input.\n\n";
	    }
	}
    }

    ~InputWrapper() {
	if (inbuf) std::cin.rdbuf(inbuf);       // restore cin
    }

    // raises runtime_error on end of input
    std::string generalQuestion(const std::string& prompt="") {
	std::cout << prompt;
	bool done(false);
	std::string response;
	while (!done) {
	    if (getline(std::cin, response)) {
		if (inbuf)
		    std::cout << response << std::endl;   // echo input from file
		if (response.length() > 0)
		    done = true;
	    } else {
		if (inbuf) {
		    // switch back to keyboard input
		    std::cin.clear();
		    std::cin.rdbuf(inbuf);
		    inbuf = NULL;
		} else {
		    throw std::runtime_error("unexpected end of input reached.");
		}
	    }
	}
	return response;
    }
};

#endif