///////////////////////////////////////////////////////////////
// MT2-Q2 - child thread searches text file                  //
//                                                           //
// Jim Fawcett, CSE687 - Object Oriented Design, Spring 2018 //
///////////////////////////////////////////////////////////////
/*
*  There are only three ways to get a result computed by a thread:
*  1. Call async(threadproc, args...) and get result from returned
*     future.
*  2. Create a lambda that captures a variable to store result
*     and pass the lambda as the first argument to a std::thread.
*     Then, join the thread, then observe the result in the 
*     value of the captured variable.
*  3. Pass a variable, var, to store result with std::ref(var)
*     to the thread, along with the thread function and any
*     parameters it needs.  Then join the thread, and only
*     after returning from the join, observe the result stored
*     in var.
*  The first two methods are preferred, and both are illustrated
*  in this solution.
*/
#include <thread>
#include <future>
#include <fstream>
#include <iostream>
#include <string>
#include <functional>

bool textSearch(const std::string& fileName, const std::string& text)
{
  std::ifstream in(fileName);
  if (!in.good())
  {
    std::cout << "\n  can't open file \"" << fileName.c_str() << "\"";
    return false;
  }
  std::string line;
  while (std::getline(in, line).good())
  {
    if (line.find(text) != std::string::npos)
    {
      in.close();
      return true;
    }
  }
  in.close();
  return false;
}

int main()
{
  std::cout << "\n  MT2-Q2 - thread searches text file";
  std::cout << "\n ------------------------------------\n";

  std::string fileSpec = "../MT2-Q1/MT2-Q1.cpp";
  std::string text = "CSE687";

  bool result;
  std::function<void(const std::string&, const std::string&)> sf = 
    [&result](const std::string& fileSpec, const std::string& str) {
    result = textSearch(fileSpec, str);
  };
  std::thread thrd(sf, fileSpec, text);
  std::cout << "\n  main thread started search thread";
  thrd.join();

  if (result == true)
    std::cout << "\n  found \"" << text << "\" in " << fileSpec;
  else
    std::cout << "\n  did not find \"" << text << "\" in " << fileSpec;

  auto future1 = std::async(textSearch, fileSpec, text);
  std::cout << "\n  main thread returned from async";

  if (future1.get() == true)
    std::cout << "\n  found \"" << text << "\" in " << fileSpec;
  else
    std::cout << "\n  did not find \"" << text << "\" in " << fileSpec;

  text = "foobar";
  auto future2 = std::async(textSearch, fileSpec, text);
  std::cout << "\n  main thread returned from async";

  if (future2.get() == true)
    std::cout << "\n  found \"" << text << "\" in " << fileSpec;
  else
    std::cout << "\n  did not find \"" << text << "\" in " << fileSpec;

  std::cout << "\n\n";
}