#include <iostream>
#include <fstream>
using std::ios;
using std::ifstream;
using std::ofstream;
#include <string>
using std::string;
#include <unordered_map>
using std::unordered_map;
#include <vector>
using std::vector;

void loadHosts(unordered_map<string, size_t>& target,
	const char* sourceFile);
void outputHosts(const unordered_map<string, size_t>& source,
	const char* outputDirectory);

int main(
#ifndef _DEBUG
	const int argc, const char* argv[]
#endif
)
{
#ifdef _DEBUG
	const char* argv[] = { __FILE__, "C:/hosts1.txt" , "C:/hosts2.txt",
		"C:/hosts3.txt", "C:/"};
	int argc = 5;
#endif

	if (argc < 2)
	{
		std::cout << "Usage: "
			<< argv[0]
			<< " <hosts_file_1.txt> ... <hosts_file_n.txt> <output_folder>\n\n";
		return 1;
	}

	vector<const char*> inputFilenames;
	for (size_t argIdx = 1; argIdx < argc - 1; ++argIdx)
	{
		inputFilenames.push_back(argv[argIdx]);
	}

	unordered_map<string, size_t> counter;
	for (const char* sourceFilepath : inputFilenames)
	{
		loadHosts(counter, sourceFilepath);
	}

#ifdef _DEBUG
	ofstream log("log.txt", ios::trunc);
	for (const auto& KVP : counter)
	{
		if(KVP.second > 1)
		{
			log << KVP.first << " " << KVP.second << '\n';
		}
	}
	log.close();
#endif

	outputHosts(counter, argv[argc - 1]);

	return 0;
}

void loadHosts(unordered_map<string, size_t>& target,
	const char* sourceFilepath)
{
	ifstream inFile(sourceFilepath);
	if (!inFile.good())
	{
		std::cout << "\nCould not open "
			<< sourceFilepath
			<< " for reading!\n";
		return;
	}

	while (!inFile.eof())
	{
		string line;
		inFile >> line;

		if (line == "0.0.0.0" || line == "0")
		{
			inFile >> line;
			++target[line];
		}
		else
		{
			inFile.ignore(UINT64_MAX, '\n');
		}
	}

	if (inFile.bad())
	{
		std::cout << "\nError processing " << sourceFilepath << '\n';
	}
	else
	{
		std::cout << '\n' << sourceFilepath << " loaded successfully!\n";
	}
}

void outputHosts(const unordered_map<string, size_t>& source,
	const char* outputDirectory)
{
	string outputFile = outputDirectory;
	outputFile += "hosts";
	ofstream outFile(outputFile, ios::trunc);
	if (!outFile.good())
	{
		std::cout << "\nCould not open new file for writing hosts!\n";
		return;
	}

	for (const auto& KVP : source)
	{
		outFile << "0.0.0.0 "
			<< KVP.first
			<< '\n';
	}

	if (outFile.bad())
	{
		std::cout << "\nError processing output hosts file!\n";
	}
	else
	{
		std::cout << "\nSuccess! Output file: "
			<< outputFile << "\n\n";
	}
}