QR code generator for Computer Craft

qr.lua

-- SPDX-FileCopyrightText: 2025 TwoSquirrels
-- SPDX-License-Identifier: Apache-2.0

local qrencode = dofile("luaqrcode/qrencode.lua")

--- Generate a QR code matrix with padding.
--- @param text string the text to encode
--- @return boolean[][]|nil matrix the QR code matrix or nil if failed
local function qrcode(text)
    local ok, tab = qrencode.qrcode(text)
    if not ok then
        return nil
    end

    local matrix = {}
    for i = 1, #tab + 2 do
        matrix[i] = {}
        for j = 1, #tab + 2 do
            matrix[i][j] = false
        end
    end
    for i = 1, #tab do
        for j = 1, #tab do
            matrix[i + 1][j + 1] = tab[i][j] > 0
        end
    end

    return matrix
end

--- Move the turtle to the specified direction.
--- @param left boolean whether to turn left
local function turn(left)
    if left then
        turtle.turnLeft()
    else
        turtle.turnRight()
    end
end

--- Move the turtle forward, dig or attack if necessary.
--- @return boolean whether the turtle moved forward
local function forceForward()
    if turtle.getFuelLevel() == 0 then
        print("Error: out of fuel!")
        return false
    end
    while not turtle.forward() do
        if turtle.detect() then
            turtle.dig()
        else
            turtle.attack()
        end
    end
    return true
end

--- Elevate the turtle to the specified direction, dig or attack if necessary.
--- @param up boolean whether to elevate up
--- @return boolean whether the turtle elevated
local function forceElevate(up)
    if turtle.getFuelLevel() == 0 then
        print("Error: out of fuel!")
        return false
    end
    if up then
        while not turtle.up() do
            if turtle.detectUp() then
                turtle.digUp()
            else
                turtle.attackUp()
            end
        end
    else
        while not turtle.down() do
            if turtle.detectDown() then
                turtle.digDown()
            else
                turtle.attackDown()
            end
        end
    end
    return true
end

--- Place a block at the vertical position, dig or attack if necessary.
--- @param slot integer the slot number
--- @param up boolean whether to place up
local function forcePlaceVertical(slot, up)
    turtle.select(slot)
    if up then
        while not turtle.placeUp() do
            if turtle.detectUp() then
                turtle.digUp()
            else
                turtle.attackUp()
            end
        end
    else
        while not turtle.placeDown() do
            if turtle.detectDown() then
                turtle.digDown()
            else
                turtle.attackDown()
            end
        end
    end
end

--- Get the slot with the specified color.
--- @param black boolean whether to get the black slot (white: 1-8 slots, black: 9-16 slots)
--- @return integer|nil slot the slot number or nil if not found
local function getSlot(black)
    local slot = black and 9 or 1
    for _ = 1, 8 do
        turtle.select(slot)
        if turtle.getItemCount(slot) > 0 then
            return slot
        end
        slot = slot + 1
    end
    return nil
end

--- Check if the turtle has enough fuel. Print an error message if not.
--- @param required integer the required fuel level
--- @return boolean whether the turtle has enough fuel
local function checkFuel(required)
    if turtle.getFuelLevel() < required then
        print("Error: not enough fuel! (required: " .. required .. ", stock: " .. turtle.getFuelLevel() .. ")")
        return false
    end
    return true
end

--- Check if the turtle has enough blocks. Print an error message if not.
--- @param required { [1]: integer, [2]: integer } the required number of blocks ([1]: 1-8 slots, [2]: 9-16 slots)
--- @return boolean whether the turtle has enough blocks
local function checkStock(required)
    local stock = {0, 0}
    for i = 1, 8 do
        stock[1] = stock[1] + turtle.getItemCount(i)
    end
    for i = 9, 16 do
        stock[2] = stock[2] + turtle.getItemCount(i)
    end

    local shortage = false
    if stock[1] < required[1] then
        print("Error: not enough WHITE blocks! (required: " .. required[1] .. ", stock: " .. stock[1] .. ")")
        shortage = true
    end
    if stock[2] < required[2] then
        print("Error: not enough BLACK blocks! (required: " .. required[2] .. ", stock: " .. stock[2] .. ")")
        shortage = true
    end
    return not shortage
end

--- @type table<string, { [1]: integer, [2]: integer }>
local DIRECTIONS = {
    ul = {-1, -1},
    ur = {-1, 1},
    dl = {1, -1},
    dr = {1, 1},
}

--- @type string[]
local args = {...}
if #args < 2 or #args > 3 or not DIRECTIONS[args[1]] then
    print("Error: invalid arguments!")
    print("")
    print("Usage: qr [ul|ur|dl|dr] <text>")
    print("")
    print("Hint: Place WHITE blocks in the UPPER row and")
    print("            BLACK blocks in the LOWER row of the inventory.")
    print("")
    return 1
end

-- generate the QR code

local matrix = qrcode(table.concat(args, " ", 2))
if not matrix then
    print("Error: failed to generate QR code!")
    return 1
end
print("QR code size: " .. #matrix .. "x" .. #matrix)
if #matrix > 31 then
    print("Error: QR code is too large! (max 31x31)")
    return 1
end

local qrDir = DIRECTIONS[args[1]]
local mi, mj = qrDir[1] >= 0 and 0 or #matrix + 1, qrDir[2] >= 0 and 1 or #matrix
local dmi, dmj = qrDir[1], qrDir[2]

-- check if the turtle has enough fuel and blocks

if not checkFuel(#matrix * #matrix) then
    return 1
end

local requiredBlocks = {0, 0}
for i = 1, #matrix do
    for j = 1, #matrix do
        if matrix[i][j] then
            requiredBlocks[2] = requiredBlocks[2] + 1
        else
            requiredBlocks[1] = requiredBlocks[1] + 1
        end
    end
end
if not checkStock(requiredBlocks) then
    return 1
end

-- draw the QR code

print("Drawing QR code...")

for i = 1, #matrix do
    turn(dmj < 0)

    -- draw a row
    for j = 1, #matrix do
        if turtle.getFuelLevel() == 0 then
            print("Error: out of fuel!")
            return 1
        end

        if j == 1 then
            forceElevate(dmi < 0)
            mi = mi + dmi
        else
            forceForward()
            mj = mj + dmj
        end

        local slot = getSlot(matrix[mi][mj])
        if not slot then
            print("Error: not enough blocks!")
            return 1
        end
        forcePlaceVertical(slot, dmi >= 0)
    end

    dmj = -dmj
    turn(dmj < 0)

    print("Progress: " .. i .. "/" .. #matrix)
end

print("QR code drawn!")

-- return to the starting point

print("Returning to the starting point...")

dmi = -dmi
dmj = -dmj

turn(dmj < 0)
turn(dmj < 0)
forceForward()
for _ = 1, #matrix do
    forceElevate(dmi < 0)
end
if #matrix % 2 == 1 then
    turn(dmj < 0)
    for _ = 1, #matrix - 1 do
        forceForward()
    end
end

print("Returned to the starting point! Have a nice day!")

前提として、luaqrcode/ に qrencode.lua をダウンロードして入れておく必要があります