#pragma once
///////////////////////////////////////////////////////////////////////////////
// Logger.h - Template class logs messages using services of template policy //
//                                                                           //
// Jim Fawcett, Solution second week Wednesday exercise                      //
// Short Course, Summer 2016                                                 //
///////////////////////////////////////////////////////////////////////////////
/*
 * Note: 
 * - Needed to use _CRT_SECURE_NO_WARNINGS; 
 *   in Project Properties > C/C++ > Preprocessor
 *   due to use of localtime instead of localtime_s 
 *   which needs some rework to code in its vicinity
 * - sigh!
 */
#include <string>
#include <ctime>
#include <chrono>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <sstream>
#include <time.h>

/////////////////////////////////////////////////////////////////////////////
// Logger class logs messages using Write Policy class WP

template <typename WP>
class Logger
{
public:
  Logger(const std::string& userName) : name_(userName) {}
  void logTitle(const std::string& msg);  // write title for batch of logs
  void log(const std::string& msg);       // write log message
  WP& writer();                           // provide access to writer
private:                                  // - needed to open and close file
  std::string name_;
  WP wp_;
};

template <typename WP>
WP& Logger<WP>::writer()
{
  return wp_;
}

template <typename WP>
void Logger<WP>::logTitle(const std::string& msg)
{
  std::string logItem = "\n" + msg + "\n";
  logItem += std::string(msg.size(), '-');
  wp_.write(logItem);
}

std::string systemTime()
{
  std::chrono::system_clock::time_point timestamp = std::chrono::system_clock::now();
  std::time_t now_c = std::chrono::system_clock::to_time_t(timestamp);
  std::ostringstream out;
  out << std::put_time(std::localtime(&now_c), "%F %T");
  return out.str();
}

template <typename WP>
void Logger<WP>::log(const std::string& msg)
{
  std::string logItem = name_ + " " + systemTime() + "\n" + msg;
  wp_.write(logItem);
}

/////////////////////////////////////////////////////////////////////////////
// IWriter interface for Writer Policies

struct IWriter
{
  virtual void write(const std::string& msg) = 0;
  virtual ~IWriter() {}
};

/////////////////////////////////////////////////////////////////////////////
// StdOutWriter class writes log messages to std::cout

class StdOutWriter : public IWriter
{
public:
  virtual void write(const std::string& msg)
  {
    std::cout << "\n" << msg;
  }
};

/////////////////////////////////////////////////////////////////////////////
// FileWriter class writes log messages to file

class FileWriter : public IWriter
{
public:
  bool open(const std::string& filename)
  {
    out_.open(filename);
    if (!out_.good())
    {
      std::cout << "\n\n  can't open log file \"" << filename.c_str() << "\"\n\n";
      return false;
    }
    return true;
  }
  void close()
  {
    out_.close();
  }
  virtual void write(const std::string& msg)
  {
    out_ << "\n" << msg;
  }
private:
  std::ofstream out_;
};