GHOSTY v0.9.3

--- GHOSTY CLIENT/SERVER
--- v0.9.3
--- by Pazzesco
---
---
--- DISCLAIMER:
--- BY USING THIS SOFTWARE, YOU ACCEPT THE RISK OF ANY AND ALL LOSS, DAMAGE, OR UNSATISFACTORY PERFORMANCE OF THIS SOFTWARE
--- OR PROGRAM RESTS WITH YOU AS THE USER. TO THE EXTENT PERMITTED BY LAW, NEITHER THE AUTHOR, NOR ANY PERSON EITHER
--- EXPRESSLY OR IMPLICITLY, MAKES ANY REPRESENTATION OR WARRANTY REGARDING THE APPROPRIATENESS OF THE USE, OUTPUT, OR
--- RESULTS OF THE USE OF THIS SOFTWARE OR PROGRAM IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY, BEING CURRENT OR
--- OTHERWISE. IF YOU RELY UPON THIS SOFTWARE OR PROGRAM, YOU DO SO AT YOUR OWN RISK, AND YOU ASSUME THE RESPONSIBILITY FOR
--- THE RESULTS. SHOULD THIS SOFTWARE OR PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL LOSSES, INCLUDING, BUT NOT
--- LIMITED TO, ANY NECESSARY SERVICING, REPAIR OR CORRECTION OF ANY PROPERTY INVOLVED.
---
---
---
---
---
---
--- ******************************
--- ** Protocol command reference
---
---
---   *****************
---   ** Command syntax
---
---   <command><image-name>...
---   NOTE: The client command RAWxx does not follow this syntax, since it doesn't use an image-name header.
---
---
---   ************************************
---   ** Transfer commands (client/server)
---
---   PRG - Purges all files from client.
---   MDR - A mkdir command. Additional headers: <directory name>.
---   FIL - A file transfer notification. Actual file contents are transfered in a separate RAW message. Additional headers: <filename><transfer ID>
---   RAWxx - A raw file. xx = transfer ID. Note that there are no image headers, and the file contents are included at the end of the message payload.
---   FIN - Marks the end of file transfering. No more file transfer commands will be accepted.
---
---
---   ******************
---   ** Server Commands
---
---   CVR - Request server compatibility version.
---   UPD - Request a full file system update of a given image. Additional headers: <client-version>
---   PSH - Request to push an image to the server. Additional headers: <client-version>
---
---   ******************
---   ** Client Commands
---
---   CVR - Compatibility version response. Additional headers: <version>
---   NAM - Notification of server's name. Additional headers: <server-name>
---   POK - Push is accepted by server. Transfering can begin.
---   PNK - Push is rejected by server.
---
---
---
--- ************
--- ** Changelog
---
---   * 0.9.3
---     * Added program argument -ifile:<file>. Using this will install a local image file to the hard disk.
---     * Changed the program argument -mkimage:<file>. It now creates a single file of the hard disk's image instead of creating a blank image directory on the server.
---     * Added program argument -pbupdate. Using this will create an image of the computer's hard disk and upload it to Pastebin. Does NOT currently work with hard disks that have binary files.
---     * Added program argument -ipb:<pb-code>. Using this will download a GHOSTY image that was uploaded to Pastebin via GHOSTY.
---     * Added program argument -name, which if used, will place the server name in the lower right-hand corner of the screen.
---     * Added program argument -nopurge. When used, will solely create/replace files on the client when an image is loaded instead of first wiping the system clean.
---
---   * 0.9.2
---     * Fixed a bug that wasn't allowing channel changes using the -channel argument.
---
---   * 0.9.1
---     * Added program argument -upload, which is identical in effect to -update.
---     * Fixed a bug that was preventing normal computers from creating images on a server.
---
---
---
--- ********
--- ** Ideas
---
---   * Single-file retrieval; allow for single-file retrieval from a ghosty server.
---   * Per-image ignore list; images can contain a file that designates certain files/directories to ignore.
---   * An "all" image; an image that copies over every time underneath the normal image (for servers).
---   * Add in authentication for clients/servers.


-- The GHOSTY version.
local version = "0.9.3"

-- The GHOSTY compatibility version. This is the lowest version of GHOSTY that'll still work with the current version.
local compatibility = "0.9.0"

-- The image file version.
local fileVersion = "1.0.0"

-- The image file compatibility version. This is the lowest version of file that'll still work with the current version.
local fileCompatibility = "1.0.0"

-- The default channel to transmit on.
local channel = 7654

-- The different sides to look for the modem.
local sides = {"left", "right", "top", "bottom", "back", "front"}

-- Files/directories to ignore when imaging.
local ignoreFiles = {"/rom", "/disk", "/disk2", "/disk3", "/disk4", "/disk5", "/disk6"}

-- The default images directory.
local imagesDir = "/images"

-- The client timeout when requesting an image.
local clientTimeout = 60.0


local modem
local isClient = true
local running = false
local tIDCount = 1
local hasPurged = false
local lastFile = ""
local transferID = ""
local fileCount = 0
local dirCount = 0
local conflictedFileCount = 0
local timedOut = false
local curImage = ""
local screenState = "main"
local dialogYes = false
local autoAccept = false
local serverName = ""
local keepFiles = false
local locked = false
local args = {...}
local keys = {
    f6=64,
    enter=28,
    upArrow=200,
    downArrow=208,
    leftArrow=203,
    rightArrow=205
}
local banner = {
"GHOSTY",
"                       _---_     ",
"                      / o o .    ",
"                    /        .   ",
"                    /        .   ",
"                     /      .    "
}

--NOTE: Had to dice up pastebin's address to avoid the spam filter picking it up.
function charListToStr(charList) rtn = ""; for i,char in ipairs(charList) do rtn = rtn..char end; return rtn end
local pastebinUploadAddress = charListToStr({'h','t','t','p',':','/','/','p','a','s','t','e','b','i','n','.','c','o','m','/','a','p','i','/','a','p','i','_','p','o','s','t','.','p','h','p'})
local pastebinDownloadAddress = charListToStr({'h','t','t','p',':','/','/','p','a','s','t','e','b','i','n','.','c','o','m','/','r','a','w','.','p','h','p'})



--Draws the GUI to the terminal screen.
function drawGUI()
    --always draw the banner
    term.clear()
    for i,v in ipairs(banner) do
        term.setCursorPos(1,i)
        term.write(v)
    end

    local line = #banner + 2

    -- version
    term.setCursorPos(1,1)
    termWriteRight("v"..version)

    -- server name
    if serverName ~= "" then
        term.setCursorPos(52 - string.len("Server: "..serverName), 18)
        term.write("Server: "..serverName)
    end

    -- channel
    term.setCursorPos(52 - string.len("Channel: "..channel), 19)
    term.write("Channel: "..channel)

    -- exit
    --line = line + 4
    term.setCursorPos(1,19)
    term.write("[F6] Quit")

    if screenState == "main" then
        line = drawMainScreen(line)
    elseif screenState == "push" then
        line = drawPushDialog(line)
    elseif screenState == "pushWait" then
        line = drawPushWait(line)
    end

end


function drawPushWait(line)
    line = line + 2
    term.setCursorPos(1,line)
    term.write ("  Updating image "..curImage.."...")
    term.setCursorBlink(true)
    return line
end


function drawPushDialog(line)
    line = line + 1
    term.setCursorPos(1,line)
    term.write("  Client request to update image: "..curImage)
    line = line + 2
    term.setCursorPos(1,line)
    if dialogYes then
        term.write ("  Accept?   [YES]   no")
    else
        term.write ("  Accept?    yes   [NO]")
    end
    term.setCursorBlink(false)
    return line
end


function drawMainScreen(line)

    -- images list
    line = line + 2
    term.setCursorPos(1,line)
    termWriteCenter("Images")
    local lst = fs.list(imagesDir)
    local timglst = ""
    for i,fil in ipairs(lst) do
        if fs.isDir(imagesDir.."/"..fil) then
            if timglst ~= "" then
                timglst = timglst.."  "
            end
            timglst = timglst..fil
        end
    end
    line = line + 2
    term.setCursorPos(1, line)
    termWriteCenter(timglst)

    term.setCursorBlink(false)
    return line
end


function gui()
    drawGUI()
    while running do
        local evt, p1, p2, p3, p4 = os.pullEvent()
        if evt == "key" then

            if screenState == "main" then
                if p1 == keys["f6"] and not locked then
                    term.clear()
                    term.setCursorPos(1,1)
                    return true
                end
            elseif screenState == "push" then
                if (p1 == keys["leftArrow"] or p1 == keys["rightArrow"]) and not locked then
                    dialogYes = not dialogYes
                end
                if p1 == keys["enter"] and not locked then
                    if dialogYes then
                        acceptPushRequest(curImage)
                        screenState = "pushWait"
                    else
                        declinePushRequest(curImage)
                        screenState = "main"
                    end
                end
            end

        end
        drawGUI()
    end
end


function termWriteCenter(msg)
    local center = (52 - string.len(msg)) / 2
    local oldX, oldY = term.getCursorPos()
    term.setCursorPos(center, oldY)
    term.write(msg)
end


function termWriteRight(msg)
    local right = 52 - string.len(msg)
    local oldX, oldY = term.getCursorPos()
    term.setCursorPos(right, oldY)
    term.write(msg)
end


function changeChannel(newChan)
    if not modem then
        return
    end
    newChan = tonumber(newChan)
    if newChan >= 1 and newChan <= 65535 then
        modem.close(channel)
        channel = tonumber(newChan)
        modem.open(channel)
    end
end


function modemListen()

    while running do
        local event, modemSide, senderChannel, replyChannel, message, senderDistance = os.pullEvent("modem_message")

        -- No incoming files. Continue with normal protocol.
        local command = getHeader(message, 1)
        local image = getHeader(message, 2)

        --- CLIENT/UPDATING SERVER COMMANDS
        if isClient or curImage ~= "" then

            local opDir = "/"
            if isClient == false then
                opDir = imagesDir.."/"..curImage
            end

            if command == "PRG" and image == curImage then
                if not hasPurged then
                    if not keepFiles or not isClient then
                        purgeSystem(opDir)
                    end
                    hasPurged = true
                end
                if isClient == false then
                    if not fs.exists(opDir) then
                        makeDir(opDir)              --create the image
                    end
                end
            end

            if command == "FIL" and image == curImage then
                if hasPurged then
                    lastFile = getHeader(message, 3)
                    transferID = getHeader(message, 4)
                    if not isClient then
                        lastFile = opDir..lastFile
                    end
                else
                    print ("File header sent before purge. Aborted.")
                    error()
                end
            end

            if command == "MDR" and image == curImage then
                if hasPurged then
                    local newDir = getHeader(message, 3)
                    if not isClient then
                        newDir = opDir..newDir
                    end
                    handleMakeDir(newDir, curImage)
                else
                    print ("mkdir command sent before purge. Aborted.")
                    error()
                end
            end

            if string.sub(command, 1, 3) == "RAW" then
                if not isConflictingFilenameWithDir(lastFile) then
                    local tID = string.sub(command, 4, string.len(command))
                    if tID == transferID then
                        local fileData, f2 = string.sub(message, string.len(command) + 3, string.len(message))
                        receiveFile(lastFile, fileData)
                        fileCount = fileCount + 1
                        lastFile = ""
                        transferID = 0
                    end
                else
                    conflictedFileCount = conflictedFileCount + 1
                end
            end

            if command == "FIN" and image == curImage then
                if isClient then
                    printImageInstallResults()
                    break
                else
                    curImage = ""
                    screenState = "main"
                    hasPurged = false
                    drawGUI()
                end
            end

        end

        --- SERVER COMMANDS
        if not isClient then

            if command == "UPD" then
                handleUpdate(image)
            end

            if command == "CVR" then
                if fs.exists(imagesDir.."/"..image) then
                    if fs.isDir(imagesDir.."/"..image) then
                        modem.transmit(channel, channel, "<CVR><"..image.."><"..compatibility..">")
                    end
                end
            end

            if command == "PSH" then
                handlePushRequest(image, getHeader(message, 3))
            end

        --- CLIENT COMMANDS
        else

            if command == "CVR" and image == curImage then
                if not hasPurged then
                    local compVer = getHeader(message, 3)
                    if isCompatibleVersions(version, compVer) then
                        requestUpdate(curImage)
                    else
                        print ("Incompatible GHOSTY versions.")
                        print ("Client version:               "..version)
                        print ("Server compatibility version: "..compVer)
                        break
                    end
                end
            end

            if command == "NAM" and image == curImage then
                serverName = getHeader(message, 3)
                print("Server name: "..serverName)
            end

            if command == "PNK" and image == curImage then
                print("Image update was declined by server.")
                break
            end

            if command == "POK" and image == curImage then
                print("Image update was accepted by server. Updating...")
                modem.transmit(channel, channel, "<PRG><"..curImage..">")
                sendFile("/", curImage)
                modem.transmit(channel, channel, "<FIN><"..curImage..">")
                print("Update sent.")
                break
            end

        end

    end
end


--Extracts ghosty file data and writes its content to the computer's hard disk.
function extractGhostyFileDataToDisk(fileData, purgeDir)
    fVer, dat = getNextLine(fileData)
    fVer = string.gsub(fVer, "File version:","")
    if not isCompatibleVersions(fileVersion, fVer) then
        print ("Incompatible file version.")
        print ("Image file version:  "..fVer)
        print ("Client file version: "..fileVersion)
    end
    fName, dat = getNextLine(dat)
    fName = string.gsub(fName,"Image name:","")
    fSizeTotal, dat = getNextLine(dat)
    fSizeTotal = string.gsub(fSizeTotal, "File data size:", " ")
    fSizeTotal = tonumber(fSizeTotal)
    fCount, dat = getNextLine(dat)
    fCount = string.gsub(fCount, "File count:", "")
    fCount = tonumber(fCount)
    dCount, dat = getNextLine(dat)
    dCount = string.gsub(dCount, "Dir count:", "")
    dCount = tonumber(dCount)
    files = {}
    dirs = {}
    for i = 1, dCount, 1 do
        dName, dat = getNextLine(dat)
        dirs[i] = dName
    end
    for i = 1, fCount, 1 do
        fName, dat = getNextLine(dat)
        fSize, dat = getNextLine(dat)
        fSize = tonumber(fSize)
        files[i] = {fName, fSize}
    end
    --if fSizeTotal ~= string.len(dat) then
    --  print("Image data size is corrupted; does image contain binary files?")
    --  print("Reported data size: "..fSizeTotal)
    --  print("Actual data size:   "..string.len(dat))
    --  return false
    --end
    if purgeDir ~= nil then
        purgeSystem(purgeDir)
        hasPurged = true
    end
    for i = 1, dCount, 1 do
        handleMakeDir(dirs[i])
    end
    datLoc = 1
    for i = 1, fCount, 1 do
        if not isConflictingFilenameWithDir(files[i][1]) then
            if not isIgnoredFile(file) then
                fDat = string.sub(dat, datLoc, datLoc + tonumber(files[i][2]))
                receiveFile(files[i][1], fDat)
                fileCount = fileCount + 1
            end
        end
        datLoc = datLoc + tonumber(files[i][2]) + 1
    end
    return true
end


--Creates ghosty file data from the hard disk.
function makeGhostyFileDataFromDisk(ghostImageName)
    local fList = fs.list("")
    files=""
    filesData=""
    dirs=""
    dCount = 0
    fCount = 0
    for i, file in ipairs(fList) do
        file="/"..file
        if not isIgnoredFile(file) then
            if not fs.isDir(file) then
                local fdata = getFileData(file)
                files=files.."--"..file.."\n--"..string.len(fdata).."\n"
                filesData=filesData..fdata.."\n"
                fCount = fCount + 1
            else
                dirs=dirs.."--"..file.."\n"
                dCount = dCount + 1
            end
        end
    end
    rtn =   "-->-----------------------------------<\n"
          .."-->         GHOSTY image file         <\n"
          .."-->-----------------------------------<\n"
          .."--> This file was generated using     <\n"
          .."--> GHOSTY for ComputerCraft          <\n"
          .."-->                                   <\n"
          .."--> WARNING: Do not edit these values <\n"
          .."-->          unless you know what     <\n"
          .."-->          you're doing!            <\n"
          .."-->-----------------------------------<\n"
          .."--File version:    "..fileCompatibility.."\n"
          .."--Image name:      "..ghostImageName.."\n"
          .."--File data size:  "..string.len(filesData).."\n"
          .."--File count:      "..fCount.."\n"
          .."--Dir count:       "..dCount.."\n"
          .."--> \n"
          .."-->---------------<\n"
          .."-->  Directories  <\n"
          .."-->---------------<\n"
          .."--> \n"
          ..dirs
          .."--> \n"
          .."-->---------<\n"
          .."-->  Files  <\n"
          .."-->---------<\n"
          .."--> \n"
          ..files
          ..filesData.."\n"
    return rtn
end


--Makes an image of the local disk and uploads it to pastebin.
function uploadDiskToPastebin(ghostImageName)
    if not http then
        print ("To upload to Pastebin, the http API is required.")
        print ("Contact your server administrator or set enableAPI_http to true in ComputerCraft.cfg")
        return
    end
    fileData = makeGhostyFileDataFromDisk(ghostImageName)
    print ("Attempting to connect to Pastebin...")
    respAttempt = http.post(pastebinUploadAddress, "api_option=paste&api_dev_key=401a70bae40b60c47071e89a2d4856d6&api_paste_name="..textutils.urlEncode(ghostImageName).."&".."api_paste_code="..textutils.urlEncode(fileData))
    if respAttempt then
        resp = respAttempt.readAll()
        respAttempt.close()
        code = string.match( resp, "[^/]+$" )
        if string.len(code) > 10 then
            print ("Pastebin response: ")
            print (code)
            return
        end
        print ("Uploaded.")
        print ("URL: "..resp)
        print ("To install this image, run 'ghosty -ipb:"..code.."'")
    else
        print ("Failed to connect to Pastebin.")
    end
end


--Downloads and installs a ghosty image from pastebin.
function installImageFromPastebin(pastebinCode)
    print ("Attempting to connect to Pastebin...")
    respAttempt = http.get(pastebinDownloadAddress.."?i="..textutils.urlEncode(pastebinCode))
    if respAttempt then
        resp = respAttempt.readAll()
        respAttempt.close()
        if keepFiles then
            extractGhostyFileDataToDisk(resp)
        else
            extractGhostyFileDataToDisk(resp, "/")
        end
        printImageInstallResults()
    else
        print ("Failed to connect to Pastebin.")
    end
end


--Displays image installation results on terminal screen.
function printImageInstallResults()
    print(fileCount.." files copied.")
    print(dirCount.." directories copied.")
    if conflictedFileCount > 0 then
        print (conflictedFileCount.." files failed to copy. A file name is conflicting with a directory name from the image.")
    end
    print("File system updated.")
end


--Returns the next line in a given string, followed by the remainder of the string (minus the line break)
function getNextLine(strLines)
    local loc
    while string.sub(strLines,1,3) == "-->" do
        loc = string.find(strLines, "\n")
        if loc then
            strLines = string.sub(strLines, loc+1)..""
        else --nothing left, and last line is commented
            return "", ""
        end
    end
    loc = string.find(strLines, "\n")
    if string.sub(strLines,1,2) == "--" then
        strLines = string.sub(strLines,3)..""
        if loc then
            loc = loc - 2
        end
    end
    if loc then
        --NOTE: had to concat empty strings to prevent strange behaviour from returning incorrect results
        return string.sub(strLines,1,loc-1).."", string.sub(strLines, loc+1)..""
    end
    return strLines.."", ""
end


---Sends a file (or entire directory) over the channel.
function sendFile(fileName, masterImage)
    if not fs.exists(fileName) then
        return
    end
    local cFile = fileName
    if not isClient then
        cFile = getClientFilename(fileName, masterImage)
    end
    if string.len(cFile) == 0 then
        cFile = "/"
    end
    if isIgnoredFile(cFile) then
        return
    end
    if fs.isDir(fileName) then
        if cFile ~= "/" then
            makeDirRemote(cFile, masterImage)
        end
        local dirList = fs.list(fileName)
        for i,fil in ipairs(dirList) do
            if fileName == "/" then
                sendFile(fileName..fil, masterImage)
            else
                sendFile(fileName.."/"..fil, masterImage)
            end
        end
    else
        tIDCount = tIDCount + 1
        local tMsg = "<FIL><"..masterImage.."><"..cFile.."><"..tIDCount..masterImage..">"
        modem.transmit(channel, channel, tMsg)
        local fileData = getFileData(fileName)
        modem.transmit(channel, channel, "<RAW"..tIDCount..masterImage..">"..fileData)
    end

end


--Attempts to receive a file and write it to the local disk.
function receiveFile(fileName, fileData)
    if fs.exists(fileName) then
        if not keepFiles then
            print("File already sent; "..fileName)
            return
        end
    end
    writeFileData(fileName, fileData)
end


--Retrieves file data from a local file.
--function getFileData(fileName)
--  local fileHandle = io.open(fileName, "rb")
--  local clock = os.clock() + 4
    -- local fileData = {}
    -- i = 1
    -- for b in fileHandle.read do
        -- fileData[i] = string.char(b)
        -- if os.clock() >= clock then
                -- os.queueEvent("")
                -- coroutine.yield()
            -- clock = os.clock() + 4
        -- end
        -- i = i + 1
    -- end
    -- fileHandle:close()
    -- return table.concat(fileData)
-- end



-- function writeFileData(fileName, fileDat)
    -- local fileHandle = io.open(fileName, "wb")
    -- if fileHandle == nil then
        -- print("Error creating file: "..fileName)
        -- error()
    -- end
    -- local clock = os.clock() + 4
    -- for i=1,string.len(fileDat),1 do
        -- b = string.byte(fileDat, i)
        -- fileHandle:write(b)
        -- if os.clock() >= clock then
                -- os.queueEvent("")
                -- coroutine.yield()
            -- clock = os.clock() + 4
        -- end
    -- end
    -- fileHandle.close()
-- end


function getFileData(fileName)
    local fileHandle = io.open(fileName, "r")
    local fileData = fileHandle:read("*a")
    fileHandle:close()
    return fileData
end


function writeFileData(fileName, fileDat)
    local fileHandle = io.open(fileName, "w")
    if fileHandle == nil then
        print("Error creating file: "..fileName)
        error()
    end
    fileHandle:write(fileDat)
    fileHandle:close()
end


--Sends a remote signal to create a directory for the given image.
function makeDirRemote(dirName, masterImage)
    modem.transmit(channel, channel, "<MDR><"..masterImage.."><"..dirName..">")
end


--Attempts to make a given directory.
function makeDir(dirName)
    local mkOk, errorMsg = pcall(fs.makeDir,dirName)
    if not mkOk then
        print ("Error making directory: "..dirName)
        print (errorMsg)
        return false
    end
    return true
end


--Handles a directory creation request for the given image.
function handleMakeDir(dirName, masterImage)
    if isClient and keepFiles then
        if fs.exists(dirName) then
            dirName = ""
        end
    end
    if dirName ~= "" and makeDir(dirName) then
        dirCount = dirCount + 1
    end
end


---Handles an update request from a client.
function handleUpdate(masterImage)
    tDir = imagesDir.."/"..masterImage
    if not fs.exists(tDir) then
        return
    end
    if not fs.isDir(tDir) then
        return
    end
    modem.transmit(channel, channel, "<PRG><"..masterImage..">")
    if serverName ~= "" then
        modem.transmit(channel, channel, "<NAM><"..masterImage.."><"..serverName..">")
    end
    sendFile(tDir, masterImage)
    modem.transmit(channel, channel, "<FIN><"..masterImage..">")
end


--Handles a push request from a client.
function handlePushRequest(masterImage, clientVer)
    if curImage ~= "" then
        --we're currently receiving another image; decline request
        declinePushRequest(masterImage)
    end
    if not isCompatibleVersions(clientVer, compatibility) then
        modem.transmit(channel, channel, "<CVR><"..masterImage.."><"..compatibility..">")
        return
    end
    curImage = masterImage
    if autoAccept then
        screenState = "pushWait"
        acceptPushRequest(masterImage)
    else
        dialogYes = false
        screenState = "push"
    end
    drawGUI()
end


--Transmits a message, declining a client's push request.
function declinePushRequest(masterImage)
    modem.transmit(channel, channel, "<PNK><"..masterImage..">")
end


--Transmits a message, accepting a client's push request.
function acceptPushRequest(masterImage)
    modem.transmit(channel, channel, "<POK><"..masterImage..">")
end


--Sends an image push request to the server.
function sendPushRequest(masterImage)
    modem.transmit(channel, channel, "<PSH><"..masterImage.."><"..version..">")
end


---Purges all files from the directory. WARNING - use with extreme caution.
function purgeSystem(purgeDir)
    if purgeDir == "/" then
        purgeDir=""
    end
    local dirList = fs.list(purgeDir)
    for i,fil in ipairs(dirList) do
        if isIgnoredFile(purgeDir.."/"..fil) == false then
            local delOk, errorMsg = pcall(fs.delete,purgeDir.."/"..fil)
            if not delOk then
                print ("Error purging file: "..purgeDir.."/"..fil)
                print (errorMsg)
                error()
            end
        end
    end
end


function isIgnoredFile(fileName)
    for j,ignore in ipairs(ignoreFiles) do
        if ignore == fileName then
            return true
        end
    end
    return false
end


function requestUpdate(masterImage)
    modem.transmit(channel, channel, "<UPD><"..masterImage.."><"..version..">")
end


---Gets a header surrounded in <> of a given position, starting at 1.
function getHeader(cmdStr, cmdPos)
    local curPos = 1
    for cmd in string.gmatch(cmdStr, "<(.-)>") do
        if curPos == cmdPos then
            return cmd
        end
        curPos = curPos + 1
    end
    return ""
end


function getClientFilename(serverFilename, imageName)
    local rtn = string.gsub(serverFilename, imagesDir, "", 1)
    rtn = string.gsub(rtn, "/"..imageName, "", 1)
    return rtn
end

--Gets a directory name, stripping off the file name and trailing "/". If the root directory is returned, "/" is returned.
function getDirFromFilename(fileName)
    rtn = string.sub(fileName, 1, string.len(fileName)-string.find(string.reverse(fileName),"/",1))
    if rtn == "" then
        return "/"
    end
    return rtn
end


--Checks the current file system to see if a hypothetical absolute file location would
--conflict with the file system. This would occur if a file exists that is the name of
--one of the directories in the hypothetical file.
function isConflictingFilenameWithDir(fileName)
    dirName = fileName
    while true do
        dirName = getDirFromFilename(dirName)
        if dirName == "/" then
            return false
        end
        if fs.exists(dirName) then
            if not fs.isDir(dirName) then
                return true
            end
        end
    end
    error() --shouldn't reach here
end


--Requests the server for its compatibility version.
function requestCompatibilityVersion(masterImage)
    modem.transmit(channel, channel, "<CVR><"..masterImage..">")
end


--Checks if a version of something meets compatibility requirements.
--Format: major.minor.revision
function isCompatibleVersions(vers, comp)
    versList = getVersionAsList(vers)
    compList = getVersionAsList(comp)
    for i=0,2,1 do
        if versList[i] < compList[i] then
            return false
        end
        if versList[i] > compList[i] then
            return true
        end
    end
    return true
end


--Converts a string containing a version number into a list of numbers, with the major version as the first index.
function getVersionAsList(vers)
    --had to use a round-about way to split this string since gmatch was giving some problems
    verList = {0,0,0}
    index = 0
    s = ""
    for i = 1,string.len(vers),1 do
        local ts = string.sub(vers, i, i)
        if ts ~= "." then
            s = s..ts
        end
        if  ts == "." or i == string.len(vers) then
            verList[index] = tonumber(s)
            index = index + 1
            s = ""
        end
    end
    if (index ~= 3) then
        return {0, 0, 0}
    end
    return verList
end


--Setup used by both client and server.
function setup()
    -- prevent user from terminating
    os.pullEvent = os.pullEventRaw

    for i,side in ipairs(sides) do
        if peripheral.getType(side) == "modem" then
            modem = peripheral.wrap(side)
            modem.open(channel)
            running = true
        end
    end
    if not modem then
        print("No modem attached.")
        error()
    end
end


--Prepares the server's images directory, and also checks for validity.
function prepareImagesDir()
    if not fs.exists(imagesDir) then
        fs.makeDir(imagesDir)
    elseif not fs.isDir(imagesDir) then
        print (imagesDir.." is not a directory! Aborted.")
        error()
    end
end


--Shutdown performed by both client and server.
function shutdown()
    if modem then
        modem.close(channel)
    end
end


--Timeout function that sleeps for so long before returning.
function waitForTimeout()
    os.sleep(clientTimeout)
    timedOut = true
end


--Displays the utility help.
function showHelp()
    print ("GHOSTY v"..version.." disk cloning utility")
    print ("")
    print ("Arguments: ")
    print ("-i:<image>       Requests an image from server. If")
    print ("                 found, the image is installed.")
    print ("-update:<image>  Updates server's image with this")
    print ("                 client's hard disk.")
    print ("-s               Hosts a GHOSTY server.")
    print ("-images:<dir>    Sets the root images directory")
    print ("                 for the server.")
    print ("-a               Auto-accept images from clients.")
    print ("-channel:<#>     Sets the modem channel.")
    print ("-mkimage:<file>  Creates an image file of the hard")
    print ("                 disk.")
    print ("-ifile:<file>    Installs an image from a file.")
    print ("-name:<name>     Displays a name on the server.")
    print ("-nopurge         Keeps current files on client.")
    print ("                 Image files replace client files.")
    print ("-pbupdate        Uploads hard disk's image to")
    print ("                 Pastebin.")
    print ("-ipb:<code>      Installs image from Pastebin.")
end


function main()

    local clientPush = false

    --handle program arguments
    if table.getn(args) > 0 then

        local majorActions = 0

        --Primary arguments
        for i,arg in ipairs(args) do
            if arg == "-server" or arg == "-s" then
                isClient = false
                majorActions = majorActions + 1
            end
            if arg == "-a" then
                autoAccept = true
            end
            if string.sub(arg, 1, 5) == "-ipb:" then
                local tpbcode = string.sub(arg,6,string.len(arg))
                installImageFromPastebin(tpbcode)
                return
            end
            if arg == "-pbupdate" or arg == "-pbupload" then
                uploadDiskToPastebin("GHOSTY_image")
                return
            end
            if string.sub(arg, 1, 3) == "-i:" then
                curImage = string.sub(arg,4,string.len(arg))
                majorActions = majorActions + 1
            end
            if string.sub(arg, 1, 8) == "-images:" then
                local tdir = string.sub(arg,9,string.len(arg))
                if not fs.exists(tdir) then
                    print ("Cannot set images directory: no such directory!")
                    return
                end
                if not fs.isDir(tdir) then
                    print ("Cannot set images directory: not a directory!")
                    return
                end
                imagesDir = tdir
            end
            if string.sub(arg, 1, 8) == "-update:" or string.sub(arg, 1, 8) == "-upload:" then
                curImage = string.sub(arg,9,string.len(arg))
                if curImage == "" then
                    showHelp()
                    return
                end
                clientPush = true
                majorActions = majorActions + 1
            end
            if string.sub(arg, 1, 9) == "-channel:" then
                local tnum = tonumber(string.sub(arg,10,string.len(arg)))
                if tnum == nil then
                    print ("Not a valid channel number.")
                    return
                end
                if tnum < 1 or tnum > 65535 then
                    print ("Out-of-range channel number.")
                    return
                end
                channel = tnum
            end
            if string.sub(arg, 1, 6) == "-name:" then
                serverName = string.sub(arg,7,string.len(arg))
            end
            if arg == "help" or arg == "-help" or arg == "/help" or arg == "?" or arg == "/?" or arg == "-?" then
                showHelp()
                return
            end
        end

        --Secondary arguments (reliant on primary)
        for i,arg in ipairs(args) do
            if string.sub(arg, 1, 8) == "-nopurge" and isClient then
                keepFiles = true
            end
        end

        --Tertiary arguments (reliant on secondary)
        for i,arg in ipairs(args) do
            if string.sub(arg, 1, 9) == "-mkimage:" then
                local timgfile = string.sub(arg, 10)
                if timgfile == "" then
                    print("Usage: -mkimage:<image-filename>")
                    print("Generates an image file of the local hard disk.")
                    return
                end
                local fildat = makeGhostyFileDataFromDisk("GHOSTY_image")
                local fh = io.open(timgfile,"w")
                fh:write(fildat)
                fh:close()
                print ("Image created as file "..timgfile)
                return
            end
            if string.sub(arg, 1, 7) == "-ifile:" then
                local timgfile = string.sub(arg, 8)
                local fh = io.open(timgfile,"r")
                if not fh then
                    print ("Cannot open image file: "..timgfile)
                    return
                end
                local fildat = fh:read("*a")
                fh:close()
                if keepFiles then
                    extractGhostyFileDataToDisk(fildat)
                else
                    extractGhostyFileDataToDisk(fildat, "/")
                end
                print ("Image installed.")
                return
            end
        end

        if majorActions > 1 then
            print("Too many arguments provided.")
            return
        end

        if majorActions < 1 then
            print("Not enough arguments provided.")
            return
        end

    else
        showHelp()
        return
    end
    if curImage == "" and isClient then
        showHelp()
        return
    end

    setup()

    if not isClient then
        prepareImagesDir()
        parallel.waitForAny(gui, modemListen)
    else
        print("GHOSTY v"..version.." client")
        print("Image: "..curImage)
        if clientPush then
            print("Requesting to update image on channel "..channel.."...")
            sendPushRequest(curImage)
        else
            print("Requesting image on channel "..channel.."...")
            requestCompatibilityVersion(curImage)
        end
        parallel.waitForAny(waitForTimeout, modemListen)
        if timedOut then
            print ("Timed out waiting for server.")
        end
    end

    shutdown()

end




main()
sleep(0)