local system = {
    files = {
        ["hint.txt"] = { 
            content = ".hsilgnE ni `kcolnu` dellac si `gnikcolnu` ,yltnerappA ?wonk uoy diD",
            original = "Did you know? Apparently, `unlocking` is called `unlock` in English.", 
            lock = true, 
            time = "2000/12/05" 
        },
        ["memo.txt"] = { 
            content = "emergency decote keyword： 'unlock'", 
            lock = false, 
            time = "2000/12/05" 
        }
    }
}

local bios = {
    name = "compiler@io.bios",
    number = "397619"
}

local OS = {
    name = "compiler.original.OS",
    vertion = "1.0.0",
    up = "1980/05/03"
}
setmetatable(system, { __index = function(t, key) 
    return ">>ERROR: '" .. tostring(key) .. "' は無効な命令です" 
end })
local commands = {}
commands.files = function()
    print("--- SYSTEM FILES ---")
    for name, data in pairs(system.files) do
        print(string.format("    %-12s [%s]", name, data.time))
    end
end

-- OS情報
commands.os = function()
    print("---- OS INFORMATION ----")
    print("OS NAME: " .. OS.name)
    print("OS VERSION: " .. OS.vertion)
    print("OS LAST UPDATE: " .. OS.up)
end
commands.bios = function()
    print("--- BIOS INFORMATION ---")
    print("BIOS NAME: " .. bios.name)
    print("BIOS MODEL NUMBER: " .. bios.number)
end
commands.clear = function()
    print(string.rep("\n", 50))
end
commands.cat = function()
    io.write("ENTER FILENAME: ")
    io.flush()
    local target = io.read():lower()
    local file = system.files[target]
    if file then
        print("----------------------------")
        print("CONTENT: " .. file.content)
        if file.lock then 
            print(">>WARNING: THIS FILE IS ENCRYPTED.") 
        end
            print("----------------------------")
    else
        print(">>ERROR: ファイルが見つかりません")
    end
end
commands.decrypt = function()
    io.write("DECRYPT.TARGET: ")
    io.flush()
    local target = io.read():lower()
    local file = system.files[target]

    if target == "exit" or target == "" then
        print("-- DECRYPT CANCELLED --")
    elseif file and file.lock then
        print("ENCRYPTION DETECTED: " .. file.content)
        io.write("ENTER DECRYPTION KEY: ")
        io.flush()
        local key = io.read():lower()

        if key == "unlock" then
            file.lock = false
            file.content = file.original
            print(">>SUCCESS: DATA RESTORED.")
            print(">>FILE CONTENT: ")
            print(file.content)
        else
            print(">>ERROR: INVALID KEY.")
        end
    else 
        print(">>ERROR: TARGET NOT LOCKED OR NOT FOUND")
    end
end
print("------ BIOS SETUP UTILITY ------")
print("system@admin: BIOS SETUP COMMANDS")
print(">>FILES, OS, BIOS, CAT,")
print(">>DECRYPT, CLEAR, EXIT")

while true do 
    io.write("\nADMIN@ROOT: ") 
    io.flush()
    local input = io.read() 
    if input == nil then break end 

    local cmd = input:lower() 
    if cmd == "exit" then 
        print("-- SYSTEM SHUTDOWN…--") 
        break 
    elseif commands[cmd] then 
        commands[cmd]() 
    else 
        print(system[cmd]) 
    end 
end