skyTerm (ComputerCraft)

-- +--------------------------------------------------------+
-- |                                                        |
-- |                      skyTerm API                       |
-- |                                                        |
-- +--------------------------------------------------------+

local version = "Version 1.1.0"

-- By Jeffrey Alexander, aka Bomb Bloke.
-- Draws pictures in the sky using the /setblock command.
-- Requires a Command Computer, plus ComputerCraft 1.76+ / Minecraft 1.8+.
-- http://www.computercraft.info/forums2/index.php?/topic/22967-skyterm/

-------------------------------------------------------------

-- 1.76+ required due to Command Computer bug in older ComputerCraft builds:
-- https://github.com/dan200/ComputerCraft/issues/36

-------------------------------------------------------------

local palIn = fs.open("world.pal", "r")
palette = textutils.unserialise(palIn.readAll())
palIn.close()

local curCommands, maxCommands, tasks, colourNum = 0, 50, {}, {}

for i = 1, 16 do
    colourNum[math.pow(2, i - 1)] = ("0123456789abcdef"):sub(i, i)
    colourNum[("0123456789abcdef"):sub(i, i)] = i - 1
end

local function doCommand(doThis)
    while curCommands >= maxCommands do os.pullEvent("task_complete") end
    tasks[commands.execAsync(doThis)] = true
    curCommands = curCommands + 1
end

function watch()
    while true do
        local event, id = os.pullEvent("task_complete")
        if tasks[id] then curCommands, tasks[id] = curCommands - 1, nil end
    end
end

function create(x, y, z, facing, width, height, transCol)
    if not (type(x) == "number" and type(y) == "number" and type(z) == "number" and type(facing) == "string" and type(width) == "number" and type(height) == "number" and (type(transCol) == "number" or type(transCol) == "nil")) then
        error("skyTermSmall.create: Expected: number x, number y, number z, string facing, number width, number height.", 2)
    end

    transCol = colourNum[transCol]

    local termObject, textColour, backgroundColour, curX, curY = {}, colours.white, colours.black, 1, 1

    function termObject.isColour()
        return true
    end

    termObject.isColor = termObject.isColour

    function termObject.getSize()
        return width, height
    end

    function termObject.setCursorBlink() end

    function termObject.setCursorPos(newX, newY)
        if type(newX) ~= "number" or type(newY) ~= "number" then error("skyTermSmall.setCursorPos: Expected: number, number Got: " .. type(newX) .. ", " .. type(newY), 2) end
        curX, curY = math.floor(newX), math.floor(newY)
    end

    function termObject.getCursorPos()
        return curX, curY
    end

    function termObject.setTextColour(newCol)
        if type(newCol) ~= "number" or not colourNum[newCol] then error("skyTermSmall.setTextColour: Expected: colour", 2) end
        textColour = newCol
    end

    termObject.setTextColor = termObject.setTextColour

    function termObject.setBackgroundColour(newCol)
        if type(newCol) ~= "number" or not colourNum[newCol] then error("skyTermSmall.setBackgroundColour: Expected: colour", 2) end
        backgroundColour = newCol
    end

    termObject.setBackgroundColor = termObject.setBackgroundColour

    function termObject.getTextColour()
        return textColour
    end

    termObject.getTextColor = termObject.getTextColour

    function termObject.getBackgroundColour()
        return backgroundColour
    end

    termObject.getBackgroundColor = termObject.getBackgroundColour

    local facing, toCoordsString = facing:lower()
    if facing == "north" then toCoordsString = function() return tostring(x - curX + 1).." "..tostring(y - curY + 1).." "..tostring(z) end
    elseif facing == "east" then toCoordsString = function() return tostring(x).." "..tostring(y - curY + 1).." "..tostring(z - curX + 1) end
    elseif facing == "south" then toCoordsString = function() return tostring(x + curX - 1).." "..tostring(y - curY + 1).." "..tostring(z) end
    elseif facing == "west" then toCoordsString = function() return tostring(x).." "..tostring(y - curY + 1).." "..tostring(z + curX - 1) end
    else error("skyTermSmall.create: Invalid facing. Expected: north, south, east, or west.", 2) end

    function termObject.setPixel(x, y, c)
        if x < 0 or y < 0 or x > width or y > height then return end
        curX, curY = x, y
        local palette = palette[c]
        doCommand("setblock " .. toCoordsString() .. " " .. palette[5] .. " " .. palette[6])
    end

    function termObject.blit(_, _, bg)
        if #bg == 0 or curY < 1 or curY > height or curX + #bg < 2 or curX > width then return end

        if curX < 1 then
            bg = bg:sub(2 - curX)
            curX = 1
        end

        if curX + #bg - 1 > width then bg = bg:sub(1, curX + #bg - width) end

        for i = 1, #bg do
            local thisChar = bg:sub(i, i)
            doCommand("setblock " .. toCoordsString() .. (thisChar == transCol and " minecraft:air 0" or (" minecraft:wool " .. colourNum[thisChar])))
            curX = curX + 1
        end
    end

    function termObject.write(text)
        termObject.blit(text, text, string.rep(colourNum[backgroundColour], #text))
    end

    function termObject.clearLine()
        local oldX = curX
        curX = 1
        termObject.blit(nil, nil, string.rep(colourNum[backgroundColour], width))
        curX = oldX
    end

    function termObject.clear()
        local oldY = curY
        for i = 1, height do
            curY = i
            termObject.clearLine()
        end
        curY = oldY
    end

    function termObject.scroll(lines)
        if type(lines) ~= "number" or lines < 1 then error("skyTermSmall.scroll: Expected: number higher than 0", 2) end

        if lines < height then
            local oldX, oldY = curX, curY

            for j = lines + 1, height do for i = 1, width do
                local thisBlock = commands.getBlockInfo((facing == "north") and (x - i + 1) or (facing == "south") and (x + i - 1) or x, y - j + 1, (facing == "east") and (z - i + 1) or (facing == "west") and (z + i - 1) or z)
                curX, curY = i, j - lines
                doCommand("setblock " .. toCoordsString() .. " " .. thisBlock.name .. " " .. thisBlock.metadata)
            end end

            for i = height - lines + 1, height do
                curY = i
                termObject.clearLine()
            end

            curX, curY = oldX, oldY
        else termObject.clear() end
    end

    return termObject
end