Dapper Map Viewer

local g, b = colours.green, colours.blue
local logo = {{0,0,0,b,g,g,g,g,g,b},{0,b,b,g,g,g,g,g,g,g,b,b},{b,b,b,b,g,g,g,g,g,b,b,b,b},{b,g,b,b,b,g,g,g,b,b,b,b,g},{b,b,b,b,b,g,b,b,b,b,b,b,g},{b,b,b,b,b,b,g,g,b,b,b,b,b},{b,b,b,b,b,g,g,g,g,g,b,b,b},{0,b,b,b,b,b,g,g,g,g,b,b},{0,0,0,b,b,b,b,g,g,b}}

local width, height = term.getSize()
term.setBackgroundColour(colours.black)
term.clear()

local logoWidth, logoHeight = 13, 9
local logoY = math.ceil((height - logoHeight) / 2) - 2
paintutils.drawImage(logo, math.ceil((width - logoWidth) / 2), logoY)

local splashText = "A Rather Dapper Mapper"
term.setCursorPos(1 + math.ceil((width - #splashText) / 2), logoY + logoHeight + 2)
term.setBackgroundColour(colours.black)
term.setTextColor(colours.white)
term.write(splashText)

term.setCursorPos(math.ceil((width - 7) / 2), logoY + logoHeight + 3)
term.setTextColor(colours.lightBlue)
term.write("by oeed")
sleep(2)
term.setBackgroundColour(colours.black)
term.clear()

local DAPPER_CLIENT_REQUEST_CHANNEL = 4261
local DAPPER_CLIENT_DATA_CHANNEL = 4262
local DAPPER_CLIENT_REQUEST_MAP = "mapdata"

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

modem.open(DAPPER_CLIENT_REQUEST_CHANNEL)
modem.open(DAPPER_CLIENT_DATA_CHANNEL)

local bannerText = "Connecting..."
local pixels
local positionX, positionY, positionZ
local mapX, mapZ
local isPositionLocked = true
local direction = "o"
local zoom = 1
local directionColour = colours.white
local needsMapRedraw = true
local function location()
    local x, y, z = gps.locate(2)
    if not x or not y or not z then
        bannerText = "No GPS Signal"
        return positionX, positionY, positionZ
    end
    if bannerText == "No GPS Signal" then
        bannerText = nil
    end
    return math.floor(x + 0.5), math.floor(y + 0.5), math.floor(z + 0.5)
end

positionX, positionY, positionZ = location()
mapX = positionX
mapZ = positionZ

local buffer = {}
for x = 1, width do
    buffer[x] = {}
end
local function drawMap()
    if bannerText then
        term.setCursorPos(1 + math.ceil((width - #bannerText) / 2), 1)
        term.setBackgroundColour(colours.white)
        term.clearLine()
        term.setTextColour(colours.red)
        term.write(bannerText)
        for x = 1, width do
            buffer[x][1] = nil
        end
    end
    if pixels then
        local xPixel = math.floor(mapX - (zoom * width) / 2)
        local zPixelStart = math.floor(mapZ - (zoom * height) / 2)
        local directionX, directionY = math.floor((positionX - xPixel) / zoom + 0.5), math.floor((positionZ - zPixelStart) / zoom + 0.5)
        for x = 1, width do
            local xPixels = pixels[xPixel]
            local zPixel = zPixelStart
            local xBuffer = buffer[x]
            for y = 1, height do
                if not bannerText or y > 1 then
                    local pixel = xPixels and xPixels[zPixel]
                    local character, textColour, backgroundColour = " ", colours.black, colours.black
                    if pixel then
                        character = pixel[1]
                        textColour = pixel[2]
                        backgroundColour = pixel[3]
                    end
                    if x == directionX and y == directionY then
                        textColour = directionColour
                        character = direction
                    end
                    local bufferPixel = xBuffer[y]
                    if not bufferPixel or bufferPixel[1] ~= character or bufferPixel[2] ~= textColour or bufferPixel[2] ~= backgroundColour then
                        xBuffer[y] = {character, textColour, backgroundColour}
                        term.setCursorPos(x, y)
                        term.setTextColour(textColour)
                        term.setBackgroundColour(backgroundColour)
                        term.write(character)
                    end
                end
                zPixel = zPixel + zoom
            end
            xPixel = xPixel + zoom
        end
    end
    needsMapRedraw = false
end

modem.transmit(DAPPER_CLIENT_REQUEST_CHANNEL, DAPPER_CLIENT_DATA_CHANNEL, DAPPER_CLIENT_REQUEST_MAP)
local mapTimeoutTime = os.clock() + 2
local redrawTime = os.clock() + 0.05
local updatePositionTime = os.clock() + 1
local mapUpdateTime = os.clock() + 30
local directionFlashTime = os.clock() + 0.5
local updateTimer = os.startTimer(0.05)
local dragX, dragY
local didDrag = false
while true do
    local eventDetails = {os.pullEvent()}
    local event = eventDetails[1]
    if event == "timer" then
        local timer = eventDetails[2]
        if timer == updateTimer then
            local clock = os.clock()
            if mapTimeoutTime and mapTimeoutTime <= clock then
                bannerText = "No Map Server Signal"
            end
            if updatePositionTime <= clock then
                local oldPositionX, oldPositionZ = positionX, positionZ
                positionX, positionY, positionZ = location()
                updatePositionTime = os.clock() + 1
                if positionX ~= oldPositionX or positionZ ~= oldPositionZ then
                    local xDiff, zDiff = positionX - oldPositionX, positionZ - oldPositionZ
                    if math.abs(zDiff) >= math.abs(xDiff) then
                        if zDiff < 0 then
                            direction = "^"
                        else
                            direction = "v"
                        end
                    else
                        if xDiff < 0 then
                            direction = "<"
                        else
                            direction = ">"
                        end
                    end
                    needsMapRedraw = true
                end
                if isPositionLocked then
                    mapX, mapZ = positionX, positionZ
                end
            end
            if directionFlashTime <= clock then
                directionColour = (directionColour == colours.grey) and colours.white or colours.grey
                directionFlashTime = os.clock() + 0.5
                needsMapRedraw = true
            end
            if redrawTime <= clock then
                if needsMapRedraw then
                    drawMap()
                end
                redrawTime = os.clock() + 0.05
            end
            if mapUpdateTime <= clock then
                modem.transmit(DAPPER_CLIENT_REQUEST_CHANNEL, DAPPER_CLIENT_DATA_CHANNEL, DAPPER_CLIENT_REQUEST_MAP)
                mapTimeoutTime = os.clock() + 2
                mapUpdateTime = os.clock() + 30
            end
            updateTimer = os.startTimer(0.05)
        end
    elseif event == "modem_message" then
        local event, side, senderChannel, replyChannel, message, distance = unpack(eventDetails)
        if senderChannel == DAPPER_CLIENT_DATA_CHANNEL then
            needsMapRedraw = true
            pixels = message
            mapUpdateTime = os.clock() + 50
            mapTimeoutTime = false
            if bannerText == "No Map Server Signal" or bannerText == "Connecting..." then
                bannerText = nil
            end
        end
    elseif event == "key" then
        local key = eventDetails[2]
        if key == keys.minus then
            zoom = math.min(zoom + 1, 10)
            needsMapRedraw = true
        elseif key == keys.equals then
            zoom = math.max(zoom - 1, 1)
            needsMapRedraw = true
        elseif key == keys.space then
            isPositionLocked = true
            mapX, mapZ = positionX, positionZ
            needsMapRedraw = true
        end
    elseif event == "mouse_click" then
        dragX, dragY = eventDetails[3], eventDetails[4]
        didDrag = false
    elseif event == "mouse_drag" then
        local x, y = eventDetails[3], eventDetails[4]
        isPositionLocked = false
        mapX = mapX + (dragX - x) * zoom
        mapZ = mapZ + (dragY - y) * zoom
        dragX, dragY = x, y
        needsMapRedraw = true
        didDrag = true
    elseif event == "mouse_up" and not didDrag then
        dragX, dragY = eventDetails[3], eventDetails[4]
    end
end