#include <algorithm>
#include <fstream>
#include <iostream>
#include <iterator>
#include <map>
#include <stdexcept>
#include <string>
#include <vector>
#include <set>

/*
$ ./a.out example.txt 
The following parameters are not defined:
#0
#1
#2
#3

$ ./a.out example.txt first second
The following parameters are not defined:
#2
#3

$ ./a.out example.txt first second third fourth
In this text first is a parameter, and the same is true for second
meaning that first and second can be whatever we want. Also, as a test
we add fourth as well, thus skipping the third argument (but as a test
we include third here).

 */

int main(int argc, char** argv)
{
    if (argc < 2)
    {
	std::cerr << "USAGE: " << argv[0] << " TEXT [PARAMETERS...]\n";
	return 1;
    }

    std::ifstream ifs { argv[1] };
    if (!ifs)
    {
	std::cerr << "Error: Unable to open file '" << argv[1] << "'\n";
	return 2;
    }
   
    std::vector<std::string> text {
	std::istream_iterator<std::string>{ifs},
	std::istream_iterator<std::string>{}
    };

    int index { 0 };
    std::map<std::string, std::string> parameters;
    std::transform(argv + 2, argv + argc, std::inserter(parameters, parameters.end()),
		   [&index](std::string const& argument)
		   {
		       return std::make_pair("#" + std::to_string(index++), argument);
		   });

    // Find undefined parameters
    std::set<std::string> unset_parameters { };
    std::copy_if(std::begin(text), std::end(text),
		 std::inserter(unset_parameters, std::end(unset_parameters)),
		 [&parameters](std::string const& word)
		 {
		     if (word.front() != '#')
			 return false;
		     return parameters.find(word) == std::end(parameters);
		 });

    // Report error on undefined parameters
    if (unset_parameters.size() > 0)
    {
	std::cerr << "The following parameters are not defined:\n";
	std::copy(std::begin(unset_parameters), std::end(unset_parameters),
		  std::ostream_iterator<std::string>{std::cerr, "\n"});
	return 3;
    }

    // Substitute in the parameters
    std::transform(std::begin(text), std::end(text), std::begin(text),
		   [&parameters](std::string const& word)
		   {
		       if (word.front() != '#')
			   return word;
		       return parameters[word];
		   });

    // Print the finnished text
    std::copy(std::begin(text), std::end(text),
	      std::ostream_iterator<std::string>{std::cout, " "});

    std::cout << std::endl;
}