Encoder

function clr() term.clear() end
function cp(x,y) term.setCursorPos(x,y) end

function encrypt()
    clr() cp(1,1)
    write("Message: ")
    strn = read()
    write("Key: ")
    key = read()
    write("Save to /")
    save = read()
    print("Encrypting...")

    strn = tostring(strn)
    key = tonumber(key)
    if type(strn) ~= "string" then print("strn error") return end
    if type(key) ~= "number" then print("key error") return end

    local cnt = 1
    local encry = {}
    local s_key = {}

    for character in strn:gmatch(".") do
        if #encry < 1 then
            encry[1] = string.byte(character)
        else
            encry[#encry+1] = string.byte(character)
        end
    end

    for character in tostring(key):gmatch(".") do
        if #s_key < 1 then
            s_key[1] = string.byte(character)
        else
            s_key[#s_key+1] = string.byte(character)
        end
    end

    for i=1, #encry do
        encry[i] = encry[i] + s_key[cnt]
        if cnt == #s_key then
            cnt = 1
        else
            cnt = cnt + 1
        end
    end

    print("Done!")
    if save ~= "" then
    if fs.exists(save) then fs.delete(save) end
    local file = fs.open(save, "w")
    for i=1, #encry do
        file.write(encry[i])
    end
    file.close()
    end

    for i=1, #encry do
        write(string.char(encry[i]))
    end
end

function decrypt()
    write("File /")
    save = read()
    if not fs.exists(save) then clr() cp(1,1) print("Invalid") return end
    write("Key: ")
    key = read()
    print("Decrypting...")
    local file = fs.open(save, "r")
    strn = file.readLine()
    file.close()
    strn = tostring(strn)
    local fin = false
    local b_strn = string.len(strn)
    local r_strn = {}
    local s_key = {}
    local cnt = 1

    for character in key:gmatch(".") do
        if #s_key < 1 then
            s_key[1] = string.byte(character)
        else
            s_key[#s_key+1] = string.byte(character)
        end
    end

    local decode = {}

    for character in strn:gmatch(".") do
        if character == "." then
            if #decode < 1 then
                for i=1, #r_strn do
                    if decode[1] == nil then
                        decode[1] = r_strn[i]
                    else
                        decode[1] = decode[1]..r_strn[i]
                    end
                end
                r_strn = {}
            else
                for i=1, #r_strn do
                    if decode[#decode+1] == nil then
                        decode[#decode+1] = r_strn[i]
                    else
                        decode[#decode+1] = decode[#decode+1]..r_strn[i]
                    end
                end
                r_strn = {}
            end
        else
            if #r_strn < 1 then
                r_strn[1] = character
            else
                r_strn[#r_strn+1] = character
            end
        end
    end

    for i=1, #decode do
        decode[i] = tonumber(decode[i])
        decode[i] = decode[i] - s_key[cnt]
        if cnt == #s_key then
            cnt = 1
        else
            cnt = cnt + 1
        end
    end

    for i=1, #decode do
        if i == 1 then
            print(string.char(decode[i]))
        else
            print(string.char(decode[i]*-1))
        end
    end

    local file = fs.open(save, "w")
    for i=1, #decode do
        file.write(decode[i])
    end
    file.close()

    print("Done!")


end

encrypt()