Dapper Map Server

local args = {...}
if #args > 1 then
    print("Usage: mapserver <database path>")
    return
end

local DAPPER_CLIENT_REQUEST_CHANNEL = 4261
local DAPPER_CLIENT_DATA_CHANNEL = 4262
local DAPPER_SCAN_DATA_CHANNEL = 4263
local DAPPER_SCAN_ACKNOWLEDGE_CHANNEL = 4264
local DAPPER_SCAN_NEXT_REQUEST_CHANNEL = 4265
local DAPPER_SCAN_NEXT_REPLY_CHANNEL = 4266

local DAPPER_SCAN_REQUEST_NEXT = "nextblock"
local DAPPER_CLIENT_REQUEST_MAP = "mapdata"

os.setComputerLabel("Dapper Mapper Server")
print("Dapper Mapper Server by oeed")
local modem = peripheral.find("modem")
if not modem or not modem.isWireless() then
    error("Please connect a wireless modem and re-run the program.", 0)
end

print("Loading map database...")
local database
local databasePath = args[1] and args[1] or "/database"
if fs.exists(databasePath) then
    local h = fs.open(databasePath, "r")
    if h then
        database = textutils.unserialize(h.readAll())
        h.close()
    end
    if not database then
        error("Failed to read database '" .. databasePath .. "', it may be corrupt.", 0)
    end
else
    database = {
        blocks = {}
    }
end

local function saveDatabase()
    local h = fs.open(databasePath, "w")
    if h then
        local serialised = textutils.serialize(database)
        local availableSpace = fs.getFreeSpace("/") + fs.getSize(databasePath)
        if availableSpace < #serialised then
            printError("WARNING! Insufficient space to save database!")
        else
            print("Saved database. Size: " .. #serialised .. "B")
            h.write(serialised)
        end
        h.close()
    else
        printError("WARNING! Failed to save database (couldn't open file).")
    end
end

print("Downloading latest block catalogue from GitHub...")
local catalogueHandle = http.get("https://raw.githubusercontent.com/oeed/Dapper/master/Server/catalogue?"..os.time())
local catalogueRaw
if not catalogueHandle then
    print("Failed to download catalogue, trying to read a local copy.")
    local h = fs.open("catalogue", "r")
    if h then
        catalogueRaw = h.readAll()
        h.close()
    end
else
    catalogueRaw = catalogueHandle.readAll()
    local h = fs.open("catalogue", "w")
    if h then
        h.write(catalogueRaw)
        h.close()
    end
end
if not catalogueRaw then
    error("Couldn't access a copy of the block catalogue!", 0)
end
local catalogue = loadstring("return " .. catalogueRaw)()
if not catalogue then
    error("The catalogue was corrupt, sorry! Try deleting your local copy or check GitHub.", 0)
end

modem.open(DAPPER_CLIENT_REQUEST_CHANNEL)
modem.open(DAPPER_CLIENT_DATA_CHANNEL)
modem.open(DAPPER_SCAN_DATA_CHANNEL)
modem.open(DAPPER_SCAN_ACKNOWLEDGE_CHANNEL)
modem.open(DAPPER_SCAN_NEXT_REQUEST_CHANNEL)
modem.open(DAPPER_SCAN_NEXT_REPLY_CHANNEL)

print("Awaiting requests...")

-- Pixel = text, textColour, backgroundColour
local function identifyBlock(block)
    local name, state = block.name, block.state
    if catalogue[name] then
        for i, catalogueItem in ipairs(catalogue[name]) do
            local catalogueState, pixel = catalogueItem[1], catalogueItem[2]
            local match = true
            for k, v in pairs(catalogueState) do
                if v ~= state[k] then
                    match = false
                    break
                end
            end
            if match then
                return pixel
            end
        end
    end
    return {"?", colours.lightGrey, colours.grey}
end

while true do
    local event, side, senderChannel, replyChannel, message, distance = os.pullEvent("modem_message")
    if senderChannel == DAPPER_SCAN_DATA_CHANNEL then
        print("Received new map data!")
        if type(message) == "table" then
            local receivedScans = {}
            local lastYield = os.clock()
            for i, scan in pairs(message) do
                if type(scan.x) == "number" and type(scan.z) == "number" and type(scan.block) == "table" then
                    local xBlocks = database.blocks[scan.x]
                    if not xBlocks then
                        xBlocks = {}
                        database.blocks[scan.x] = xBlocks
                    end
                    if i % 200 == 199 then
                        local clock = os.clock()
                        if clock - lastYield >= 5 then
                            print("Yielding")
                            os.queueEvent("blah")
                            os.pullEvent()
                            lastYield = clock
                        end
                    end
                    xBlocks[scan.z] = scan.block
                    table.insert(receivedScans, {x = scan.x, z = scan.z})
                end
            end
            modem.transmit(DAPPER_SCAN_ACKNOWLEDGE_CHANNEL, 0, receivedScans)
            print("Added " .. #receivedScans .. " new blocks!")
        end
        saveDatabase()
    elseif senderChannel == DAPPER_SCAN_NEXT_REQUEST_CHANNEL then
        if type(message) == "table" then
            if type(message.startX) == "number" and type(message.stopX) == "number" and type(message.startZ) == "number" and type(message.stopZ) == "number" then
                print("Request for next block...")
                local response = {}
                local found = false
                for x = message.startX, message.stopX, 1 do
                    for z = message.startZ, message.stopZ, 1 do
                        if not database.blocks[x] or not database.blocks[x][z] then
                            print("Found " .. x .. ", " .. z)
                            response.x = x
                            response.z = z
                            found = true
                            break
                        end
                    end
                    if found then
                        break
                    end
                end
                modem.transmit(DAPPER_SCAN_NEXT_REPLY_CHANNEL, 0, response)
            end
        end
    elseif senderChannel == DAPPER_CLIENT_REQUEST_CHANNEL then
        if message == DAPPER_CLIENT_REQUEST_MAP then
            print("A client requested map data!")
            local pixels = {}
            for x, xBlocks in pairs(database.blocks) do
                local xPixels = {}
                for y, block in pairs(xBlocks) do
                    xPixels[y] = identifyBlock(block)
                end
                pixels[x] = xPixels
            end
            modem.transmit(DAPPER_CLIENT_DATA_CHANNEL, 0, pixels)
        end
    end
end