// This program creates a file, adds data to the file, displays the file,
// appends more data to the file, displays the file, and then deletes the file.
// It will not run if the file already exists.

function createFile(filename)
{
    var fs = require('fs')

    fs.writeFile(filename, "C\tF\n",  function(err) 
    {
        if (err) return console.error(err);
    });

    for(var c = 0; c <= 50; c++)
    {
        var f = c * 9 / 5 + 32;
        fs.appendFile(filename, c + "\t" + f + "\n", function (err) 
        {
            if (err) 
            {
                return console.error(err);
            }
        });
    }
}

function readFile(filename)
{
    var file = require('readline').createInterface(
    {
      input: require('fs').createReadStream(filename)
    });
    
    file.on('line', function (line) 
    {
        console.log(line);
    });
}

function appendFile(filename)
{
    var fs = require('fs')

    for(var c = 51; c <= 100; c++)
    {
        var f = c * 9 / 5 + 32;
        fs.appendFile(filename, c + "\t" + f + "\n", function (err) 
        {
            if (err) 
            {
                return console.error(err);
            }
        });
    }
}

function deleteFile(filename)
{
    var fs = require("fs");

    fs.unlink(filename, function(err) 
    {
        if (err) 
        {
            return console.error(err);
        }
    });
}

function fileExists(filename)
{
    var fs = require('fs');
    return fs.existsSync(filename);
}

function main()
{
    var filename = "~file.txt";

    if(fileExists(filename))
    {
        console.log("File already exists.")
    }
    else
    {
        createFile(filename);
        readFile(filename);
        appendFile(filename);
        deleteFile(filename);
    }
}

main();