CC-NICCC: ST-NICCC 2000 Port For ComputerCraft Tweaked (Version 0.85)

local function lshift(x, by) return x * 2 ^ by end
local function rshift(x, by) return math.floor(x / 2 ^ by) end
local function band(x, y) return bit32 and bit32.band(x, y) or x % (y + 1) end
local function bor(x, y) return bit32 and bit32.bor(x, y) or x - x % (y + 1) + (x + y) % (y + 1) end

local function downloadFile(url, path)
    print("Downloading " .. url .. "...")
    local response = http.get(url, nil, true)
    if response then
        local file = fs.open(path, "wb")
        file.write(response.readAll())
        file.close()
        response.close()
        print("Download complete!")
        return true
    end
    print("Download failed!")
    return false
end

local sceneUrl = "https://github.com/pulkomandy/beniccc/blob/master/scene1.bin"
local scenePath = "scene1.bin"

if not fs.exists(scenePath) and not downloadFile(sceneUrl, scenePath) then
    error("Failed to download scene1.bin")
end

local w, h = term.getSize()
local DEMO_WIDTH, DEMO_HEIGHT = 256, 200
local SCALE_X, SCALE_Y = w / DEMO_WIDTH, h / DEMO_HEIGHT

local frontBuffer, backBuffer = {}, {}
for y = 1, h do
    frontBuffer[y], backBuffer[y] = {}, {}
    for x = 1, w do
        frontBuffer[y][x] = {bg = colors.black, char = " "}
        backBuffer[y][x] = {bg = colors.black, char = " "}
    end
end

local function decode(raw)
    raw = band(raw, 0xF)
    local bits = band(rshift(raw, 3), 1)
    bits = bor(bits, band(lshift(raw, 1), 0xE))
    return bits * 17
end

local function rgbToTerminal(r, g, b)
    local minDist, bestColor = math.huge, colors.black
    for name, value in pairs(colors) do
        if type(value) == "number" then
            local cr, cg, cb = term.getPaletteColor(value)
            local dr, dg, db = r/255 - cr, g/255 - cg, b/255 - cb
            local dist = dr * dr + dg * dg + db * db
            if dist < minDist then
                minDist, bestColor = dist, value
            end
        end
    end
    return bestColor
end

local file = fs.open(scenePath, "rb")
local sceneData = file.readAll()
file.close()

local position = 1
local function readByte()
    local byte = string.byte(sceneData, position)
    position = position + 1
    return byte
end

local function readWord()
    return bor(lshift(readByte(), 8), readByte())
end

local function drawPolygon(buffer, poly, color)
    local minY, maxY = math.huge, -math.huge
    for _, p in ipairs(poly) do
        minY = math.min(minY, p.y)
        maxY = math.max(maxY, p.y)
    end

    for y = math.max(1, math.floor(minY * SCALE_Y)), math.min(h, math.ceil(maxY * SCALE_Y)) do
        local nodeX = {}
        local j = #poly
        for i = 1, #poly do
            local pi, pj = poly[i], poly[j]
            if (pi.y * SCALE_Y < y and pj.y * SCALE_Y >= y) or (pj.y * SCALE_Y < y and pi.y * SCALE_Y >= y) then
                local x = pi.x + (y / SCALE_Y - pi.y) / (pj.y - pi.y) * (pj.x - pi.x)
                table.insert(nodeX, math.floor(x * SCALE_X))
            end
            j = i
        end

        table.sort(nodeX)
        for i = 1, #nodeX, 2 do
            local startX, endX = nodeX[i], (nodeX[i+1] or w)
            for x = math.max(1, startX), math.min(w, endX) do
                buffer[y][x] = {bg = color, char = " "}
            end
            if i % 10 == 0 then os.queueEvent("yield") os.pullEvent("yield") end
        end
        if y % 10 == 0 then os.queueEvent("yield") os.pullEvent("yield") end
    end
end

local palette = {}
for i = 1, 16 do palette[i] = colors.black end

local frameCount, startTime = 0, os.clock()
local targetFrameTime = 1 / 30

local shouldExit = false

while position <= #sceneData and not shouldExit do
    local frameStartTime = os.clock()

    local flags = readByte()

    if band(flags, 2) ~= 0 then
        local colorMask = readWord()
        for i = 0, 15 do
            if band(colorMask, lshift(1, 15 - i)) ~= 0 then
                local color = readWord()
                local r = decode(color)
                local g = decode(rshift(color, 12))
                local b = decode(rshift(color, 8))
                palette[i + 1] = rgbToTerminal(r,g,b)
            end
        end
    end

    if band(flags, 1) ~= 0 then
        for y = 1, h do
            for x = 1, w do
                backBuffer[y][x] = {bg = palette[1], char = " "}
            end
        end
    end

    if band(flags, 4) ~= 0 then
        local vertices = readByte()
        local points = {}

        for i = 1, vertices do
            points[i] = {x = readByte(), y = readByte()}
            if i % 10 == 0 then os.queueEvent("yield") os.pullEvent("yield") end
        end

        while true do
            local bits = readByte()

            if bits == 0xFF then break
            elseif bits == 0xFE then
                position = band(position - 1 + 0x10000, 0xFFFF0000) + 1
                break
            elseif bits == 0xFD then
                shouldExit = true
                break
            else
                local color = palette[rshift(bits, 4) + 1]
                local numPoints = band(bits, 0xF)
                local poly = {}

                for i = 1, numPoints do
                    local index = readByte() + 1
                    poly[i] = points[index]
                    if i % 10 == 0 then os.queueEvent("yield") os.pullEvent("yield") end
                end

                drawPolygon(backBuffer, poly, color)
            end
            os.queueEvent("yield") os.pullEvent("yield")
        end

    else
        while true do
            local bits = readByte()

            if bits == 0xFF then break
            elseif bits == 0xFE then
                position = band(position - 1 + 0x10000, 0xFFFF0000) + 1
                break
            elseif bits == 0xFD then
                shouldExit = true
                break
            else
                local color = palette[rshift(bits, 4) + 1]
                local numPoints = band(bits, 0xF)
                local poly = {}

                for i = 1, numPoints do
                    poly[i] = {x = readByte(), y = readByte()}
                    if i % 10 == 0 then os.queueEvent("yield") os.pullEvent("yield") end
                end

                drawPolygon(backBuffer, poly, color)
            end
            os.queueEvent("yield") os.pullEvent("yield")
        end
    end

    frontBuffer, backBuffer = backBuffer, frontBuffer

    for y = 1, h do
        for x = 1, w do
            term.setCursorPos(x, y)
            term.setBackgroundColor(frontBuffer[y][x].bg)
            term.write(frontBuffer[y][x].char)
        end
    end

    frameCount = frameCount + 1

    local currentTime = os.clock()
    local fps = frameCount / (currentTime - startTime)
    term.setCursorPos(1, 1)
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)
    term.write(string.format("Frame: %d FPS: %.2f", frameCount, fps))

    local frameEndTime = os.clock()
    local frameTime = frameEndTime - frameStartTime

    if frameTime < targetFrameTime then os.sleep(targetFrameTime - frameTime) end
end

-- Display final statistics
local endTime = os.clock()
local totalTime = endTime - startTime
local avgFPS = frameCount / totalTime
print(string.format("Demo completed in %.2f seconds", totalTime))
print(string.format("Total frames: %d", frameCount))
print(string.format("Average FPS: %.2f", avgFPS))