CC. Uni. GradeServ

local clientAssignmentDirectory = "usr/"
local userList = "user_list"
local adminUser = "KillaVanilla"
local adminPass = "something"
local lastAccessTimes = {}
local logfile = "server.log"
local logServ = 117

function log(stuff)
    local lHandle = fs.open(logfile, "a")
    lHandle.writeLine(stuff)
    lHandle.close()
end

local function spec_print(...)
    local args2 = {...}
    local str = ""
    for i,v in ipairs(args2) do
        str = str..v
    end
    rednet.send(logServ, textutils.serialize({"LOGSERV", "GradeServ", str}))
    if http then
        local wHandle = http.get("http://timeapi.org/utc/now")
        if wHandle then
            str = "[ RL TIME: "..wHandle.readAll().." UTC] "..str
        else
            str = "[ MC TIME: Day "..os.day().." @ "..textutils.formatTime(os.time()).."} "..str
        end
    end
    print(str)
    log(str)
end

local successMsg = textutils.serialize({"assignment", "return_code", "success"})

assert(fs.exists(userList), userList.." does not exist!")
for i,v in ipairs(rs.getSides()) do
    if peripheral.getType(v) == "modem" then
        rednet.open(v)
    end
end

if not fs.exists(clientAssignmentDirectory) then
    fs.makeDir(clientAssignmentDirectory)
end

local handle = io.open(userList, "r")
local cred_table = {}
for line in handle:lines() do
    string.gsub(line, "([%a%p%d]+)%s+([%a%p%d]+)", function(user, pass) cred_table[user] = pass if not fs.exists(fs.combine(clientAssignmentDirectory, user)) then fs.makeDir(fs.combine(clientAssignmentDirectory, user)) end end)
end
cred_table[adminUser] = adminPass
handle:close()

local function runTests(inputFile) -- run a simple pair of tests designed to catch (lazy) cheaters and weed out obviously-wrong answers.
    if not fs.exists(inputFile) then
        spec_print("Attempted to run test on nonexistent file: "..input)
        return "false", "File does not exist"
    end
    local iHandle = fs.open(inputFile, "r")
    local input = iHandle.readAll()
    iHandle.close()
    for i,v in ipairs(fs.list(clientAssignmentDirectory)) do
        if fs.isDir(fs.combine(clientAssignmentDirectory, v)) then
            for i,file in ipairs(fs.list(fs.combine(clientAssignmentDirectory, v))) do
                if file ~= "SanityTests.log" then
                    local handle = fs.open(fs.combine(fs.combine(clientAssignmentDirectory, v), file), "r")
                    if handle.readAll() == input then
                        handle.close()
                        return "false" -- cheater!
                    end
                    handle.close()
                end
            end
        end
    end
    local ok, err = pcall(loadstring(input))
    return tostring(ok)
end

local function getLoginCredent(id)
    for i,v in pairs(lastAccessTimes) do
        if v[2] == id then
            return true, i
        end
    end
end

local function runSanityTests()
    for userID,user in ipairs(fs.list(clientAssignmentDirectory)) do
        if fs.isDir(fs.combine(clientAssignmentDirectory, user)) then
            local sanityLog = fs.open(fs.combine(fs.combine(clientAssignmentDirectory, user), "SanityTests.log"), "w")
            for fileID, fileName in ipairs(fs.list(fs.combine(clientAssignmentDirectory, user))) do
                if fileName ~= "SanityTests.log" then
                    sanityLog.writeLine(fileName..": "..runTests(fs.combine(fs.combine(clientAssignmentDirectory, user), fileName)))
                end
            end
            sanityLog.close()
        end
    end
end


local function listenerThread()
    while true do
        local id, msg = rednet.receive()
        msg = textutils.unserialize(msg)
        if msg then
            local hasLoggedIn, user = getLoginCredent(id)
            local isAdmin = false
            if hasLoggedIn then
                isAdmin = (user == adminUser)
            end
            if msg[1] == "assignment" then
                if msg[2] == "login" then
                    if cred_table[msg[3]] == msg[4] then
                        if msg[3] == adminUser then
                            spec_print("ID "..id.." logged in as "..msg[3]..". (admin account)")
                        else
                            spec_print("ID "..id.." logged in as "..msg[3]..". (student account)")
                        end
                        lastAccessTimes[msg[3]] = {os.clock(), id}
                        rednet.send(id, successMsg)
                    end
                elseif hasLoggedIn then
                    if msg[2] == "logout" then
                        spec_print("ID "..id.." ("..user..") logged out.")
                        lastAccessTimes[user] = nil
                        rednet.send(id, successMsg)
                    elseif msg[2] == "submit" then
                        if not fs.exists(fs.combine(clientAssignmentDirectory..user, msg[3])) then
                            local file = fs.open(fs.combine(clientAssignmentDirectory..user, msg[3]), "w")
                            file.write(msg[4])
                            file.close()
                            spec_print("ID "..id.." ("..user..") submitted an assignment as file "..msg[3].." ("..fs.getSize(fs.combine(clientAssignmentDirectory..user, msg[3])).." bytes written).")
                            rednet.send(id, successMsg)
                        end
                        lastAccessTimes[user][1] = os.clock()
                    elseif msg[2] == "get_results" then
                        spec_print("ID "..id.." ("..user..") downloaded his/her test results.")
                        local file = fs.open(fs.combine(clientAssignmentDirectory..user, "SanityTests.log"), "r")
                        rednet.send(id, textutils.serialize({"assignment", "results", file.readAll()}))
                        file.close()
                        lastAccessTimes[user][1] = os.clock()
                    elseif isAdmin then
                        local fullFileName = fs.combine(clientAssignmentDirectory, msg[3])
                        if msg[2] == "get" then
                            if fs.exists(fullFileName) then
                                spec_print("ID "..id.." ("..user..") downloaded file "..fullFileName..".")
                                local handle = fs.open(fullFileName, "r")
                                rednet.send(id, textutils.serialize({"assignment", "file", msg[3], handle.readAll()}))
                                handle.close()
                            end
                        elseif msg[2] == "list" then
                            spec_print("ID "..id.." ("..user..") requested directory listing for "..fullFileName..".")
                            if fs.exists(fullFileName) and fs.isDir(fullFileName) then
                                rednet.send(id, textutils.serialize({"assignment", "list", msg[3], fs.list(fullFileName)}))
                            end
                        elseif msg[2] == "put" then
                            local handle = fs.open(fullFileName, "w")
                            handle.write(msg[4])
                            handle.close()
                            spec_print("ID "..id.." ("..user..") uploaded file "..fullFileName.." ("..fs.getSize(fullFileName).." bytes written).")
                            rednet.send(id, successMsg)
                        elseif msg[2] == "delete" then
                            if fs.exists(fullfileName) then
                                fs.delete(fullFileName)
                                spec_print("ID "..id.." ("..user..") deleted file "..fullFileName..".")
                            end
                        end
                    end
                end
            end
        end
    end
end

local function timedEventThread()
    local sanityTestItr = 0
    while true do
        local lastAccessTimes_clone = {}
        for i,v in pairs(lastAccessTimes) do
            if os.clock() < v[1]+300 then
                lastAccessTimes_clone[i] = v
            else
                spec_print("Automatically logging out ID "..v[2].." ("..i..") due to inactivity.")
            end
        end
        lastAccessTimes = lastAccessTimes_clone
        sanityTestItr = sanityTestItr+1
        if sanityTestItr >= 30 then
            runSanityTests()
            sanityTestItr = 0
        end
        os.sleep(1)
    end
end

spec_print("GradeServ V1.2 is ONLINE!")
parallel.waitForAll(listenerThread, timedEventThread)