--- Day 8: Handheld Halting ---

#include <string>
#include <vector>
#include <sstream>
#include <iostream>
#include <iterator>

void RestoreProgram(std::vector<std::string>& assembly)
{
    for (unsigned int i = 0; i < assembly.size(); i++)
    {
        std::string& command = assembly[i];
        if (command[command.size() - 1] == '!')
        {
            command[command.size() - 1] = '\n';
        }
    }
}

bool RunProgram(std::vector<std::string>& assembly)
{
    int acc = 0;
    int pos = 0;

    while (true)
    {
        if (pos >= assembly.size()) //Assume program ended successfully
        {
            std::cout << "Accumulator returned: " << acc << std::endl;
            RestoreProgram(assembly);
            return true;
        }

        std::string& command = assembly[pos];

        std::istringstream iss(command);
        std::vector<std::string> results(std::istream_iterator<std::string>{iss},
            std::istream_iterator<std::string>());

        if (command[command.size() - 1] == '!')
        {
            std::cout << "Infinite Loop Error! Last Pos: " << pos << std::endl;
            RestoreProgram(assembly);
            return false;
        }
        else if (results[0] == "acc")
        {
            acc += atoi(results[1].c_str());
            pos++;
        }
        else if (results[0] == "jmp")
        {
            pos += atoi(results[1].c_str());
        }
        else //Assume nop
        {
            pos++;
        }

        //std::cout << "Command: " << results[0] << " " << results[1] << " Pos: " << pos << " Acc " << acc << std::endl;
        command[command.size() - 1] = '!';
    }
}

int main()
{
    std::vector<std::string> instructions;

    std::string text;
    while (getline(std::cin, text))
        instructions.push_back(text);

    std::cout << "Number of Instructions: " << instructions.size() << std::endl;

    for (unsigned int i = 0; i < instructions.size(); i++)
    {
        if (instructions[i][0] == 'n')
        {
            instructions[i][0] = 'j';
            instructions[i][1] = 'm';
            if (!RunProgram(instructions))
            {
                instructions[i][0] = 'n';
                instructions[i][1] = 'o';
            }
            else
            {
                std::cout << "Corrupted NOP found at line: " << i << std::endl;
                return 0;
            }
        }
        else if (instructions[i][0] == 'j')
        {
            instructions[i][0] = 'n';
            instructions[i][1] = 'o';
            if (!RunProgram(instructions))
            {
                instructions[i][0] = 'j';
                instructions[i][1] = 'm';
            }
            else
            {
                std::cout << "Corrupted JMP found at line: " << i << std::endl;
                return 0;
            }
        }
    }

    std::cout << "No fix found! :(" << std::endl;
    return 0;
}