OC-NICCC: ST-NICCC 2000 Port For OpenComputers (Version 0.85)

local component = require("component")
local gpu = component.gpu
local internet = require("internet")
local fs = require("filesystem")
local computer = require("computer")

local SCREEN_WIDTH, SCREEN_HEIGHT = gpu.getResolution()
local ASCII_CHARS = " .'`^\",:;Il!i><~+_-?][}{1)(|/tfjrxnuvczXYUJCLQ0OZmwqpdbkhao*#MW&8%B@$"
local SCENE_URL = "https://github.com/dabadab/st-niccc-2000-html5/raw/master/scene1.bin"
local SCENE_FILE = "scene1.bin"
local TARGET_FPS = 30

gpu.setResolution(SCREEN_WIDTH, SCREEN_HEIGHT)

local backBuffer = {}
for y = 1, SCREEN_HEIGHT do
    backBuffer[y] = string.rep(" ", SCREEN_WIDTH)
end

local function downloadFile(url, filename)
    print("OC-NICCC: ST-NICCC 2000 Port For OpenComputers Created By nonogamer9")
    print("THIS IS")
    print("*NOT*")
    print("AN COMPUTERCRAFT DEMO")
    print("Downloading " .. filename .. "...")
    local result = ""
    for chunk in internet.request(url) do
        result = result .. chunk
    end
    local file = io.open(filename, "wb")
    file:write(result)
    file:close()
    print("Download complete! Enjoy The Demo!")
end

local function readBinaryFile(filename)
    local file = io.open(filename, "rb")
    if not file then return nil end
    local content = file:read("*all")
    file:close()
    return content
end

local function decode(raw)
    raw = raw & 0xF
    local bits = (raw >> 3) & 1
    bits = bits | ((raw << 1) & 0xE)
    return bits * 17
end

local function colorToAscii(r, g, b)
    local intensity = (0.299 * r + 0.587 * g + 0.114 * b) / 255
    local index = math.floor(intensity * (#ASCII_CHARS - 1)) + 1
    return ASCII_CHARS:sub(index, index)
end

local function clearBackBuffer()
    for y = 1, SCREEN_HEIGHT - 1 do
        backBuffer[y] = string.rep(" ", SCREEN_WIDTH)
    end
end

local function flushBackBuffer()
    for y = 1, SCREEN_HEIGHT - 1 do
        gpu.set(1, y, backBuffer[y])
    end
end

local function renderFrame(dataStream, colors)
    local align = false
    local flags = string.byte(dataStream:read(1))

    if flags & 2 > 0 then
        local colorsData = dataStream:read(2)
        local colorsValue = (string.byte(colorsData, 1) << 8) | string.byte(colorsData, 2)
        for i = 0, 15 do
            if colorsValue & (1 << (15 - i)) > 0 then
                local colorData = dataStream:read(2)
                local colorValue = (string.byte(colorData, 1) << 8) | string.byte(colorData, 2)
                colors[i + 1] = {
                    red = decode(colorValue),
                    green = decode(colorValue >> 4),
                    blue = decode(colorValue >> 8)
                }
            end
        end
    end

    if flags & 1 > 0 then
        clearBackBuffer()
    end

    local function drawLine(x1, y1, x2, y2, char)
        local dx = math.abs(x2 - x1)
        local dy = math.abs(y2 - y1)
        local sx = x1 < x2 and 1 or -1
        local sy = y1 < y2 and 1 or -1
        local err = dx - dy

        while true do
            if x1 >= 1 and x1 <= SCREEN_WIDTH and y1 >= 1 and y1 <= SCREEN_HEIGHT - 1 then
                local row = backBuffer[y1]
                backBuffer[y1] = row:sub(1, x1 - 1) .. char .. row:sub(x1 + 1)
            end
            if x1 == x2 and y1 == y2 then break end
            local e2 = 2 * err
            if e2 > -dy then
                err = err - dy
                x1 = x1 + sx
            end
            if e2 < dx then
                err = err + dx
                y1 = y1 + sy
            end
        end
    end

    local function drawPolygon(polygon, char)
        for i = 1, #polygon do
            local p1 = polygon[i]
            local p2 = polygon[i % #polygon + 1]
            local x1, y1 = math.floor(p1.x * SCREEN_WIDTH / 320), math.floor(p1.y * (SCREEN_HEIGHT - 1) / 200)
            local x2, y2 = math.floor(p2.x * SCREEN_WIDTH / 320), math.floor(p2.y * (SCREEN_HEIGHT - 1) / 200)
            drawLine(x1, y1, x2, y2, char)
        end
    end

    if flags & 4 > 0 then
        local verticesCount = string.byte(dataStream:read(1))
        local points = {}
        for i = 1, verticesCount do
            local x = string.byte(dataStream:read(1))
            local y = string.byte(dataStream:read(1))
            points[i] = {x = x, y = y}
        end
        while true do
            local bits = string.byte(dataStream:read(1))
            if bits == 0xFF then
                align = false
                break
            elseif bits == 0xFE then
                align = true
                break
            elseif bits == 0xFD then
                return false
            else
                local polygon = {}
                for i = 1, (bits & 0xF) do
                    local index = string.byte(dataStream:read(1))
                    table.insert(polygon, points[index + 1])
                end
                local color = colors[(bits >> 4) + 1]
                local char = colorToAscii(color.red, color.green, color.blue)
                drawPolygon(polygon, char)
            end
        end
    else
        while true do
            local bits = string.byte(dataStream:read(1))
            if bits == 0xFF then
                align = false
                break
            elseif bits == 0xFE then
                align = true
                break
            elseif bits == 0xFD then
                return false
            else
                local polygon = {}
                for i = 1, (bits & 0xF) do
                    local x = string.byte(dataStream:read(1))
                    local y = string.byte(dataStream:read(1))
                    table.insert(polygon, {x = x, y = y})
                end
                local color = colors[(bits >> 4) + 1]
                local char = colorToAscii(color.red, color.green, color.blue)
                drawPolygon(polygon, char)
            end
        end
    end

    if align then
        local position = dataStream:seek("cur", 0)
        position = (position + 0xFFFF) & ~0xFFFF
        dataStream:seek("set", position)
    end

    return true
end

local function main()
    if not fs.exists(SCENE_FILE) then
        downloadFile(SCENE_URL, SCENE_FILE)
    end

    local sceneData = readBinaryFile(SCENE_FILE)
    if not sceneData then
        print("Failed to read " .. SCENE_FILE)
        return
    end

    local dataStream = {
        data = sceneData,
        position = 1,
        read = function(self, count)
            local result = self.data:sub(self.position, self.position + count - 1)
            self.position = self.position + count
            return result
        end,
        seek = function(self, whence, offset)
            if whence == "set" then
                self.position = offset + 1
            elseif whence == "cur" then
                self.position = self.position + offset
            end
            return self.position - 1
        end
    }

    local colors = {}
    for i = 1, 16 do
        colors[i] = {red = 0, green = 0, blue = 0}
    end

    local frameCount = 0
    local lastTime = computer.uptime()
    local fpsUpdateInterval = 0.1
    local lastFpsUpdate = lastTime
    local frameTime = 1 / TARGET_FPS
    local currentFps = 0

    while renderFrame(dataStream, colors) do
        frameCount = frameCount + 1
        local currentTime = computer.uptime()
        if currentTime - lastFpsUpdate >= fpsUpdateInterval then
            currentFps = frameCount / (currentTime - lastFpsUpdate)
            frameCount = 0
            lastFpsUpdate = currentTime
            gpu.fill(1, SCREEN_HEIGHT, SCREEN_WIDTH, 1, " ")
            gpu.set(1, SCREEN_HEIGHT, string.format("FPS: %.1f", currentFps))
        end
        flushBackBuffer()
        local frameDuration = computer.uptime() - currentTime
        if frameDuration < frameTime then
            os.sleep(frameTime - frameDuration)
        end
    end
end

main()