Miner

tunnelLength = 100
buffer = 2
tunnels = 10
placeTorches = true
blocksBetweenTorches = 10
autoRefuel = true
startLeft = false

trash = {
    dirt = true,
    cobblestone = true,
    stone = true,
    gravel = true,
    quartz = true,
    resource = true,
    nugget = true,
    redstone = true,
    iron_ore = true,
    flint = true
}

local function check()
    for i=2,15 do
        item = turtle.getItemDetail(i)
        if item ~= nil then
            print("Item: "..item.name)
            print(trash[item.name])

            colon = string.find(item.name, ":")

            if trash[string.sub(item.name, colon + 1)] ~= nil and item.count > 0 then
                print("That's trash, throw it out")
                turtle.select(i)
                turtle.dropDown()
            elseif item.name == "minecraft:coal" and autoRefuel then
                if turtle.getItemDetail(1).name == "minecraft:coal" then
                    turtle.transferTo(1, item.count)
                end

                if turtle.getFuelLevel() < 50 then
                    turtle.select(1)
                    turtle.refuel()
                end
            elseif item.name == "minecraft:torch" then
                turtle.transferTo(16, turtle.getItemCount(i))
            end
        end
    end

    os.setComputerLabel("Fuel: "..turtle.getFuelLevel())
    turtle.select(1)
end

local function height()
    turtle.dig()
    turtle.digUp()
    turtle.digDown()

    isBlock, block = turtle.inspect()

    if isBlock and block.name == "minecraft:gravel" then
        height()
    end
end

local function length()
    for i=1,tunnelLength do
        height()

        if (i % (blocksBetweenTorches + 1)) == 0 and placeTorches and turtle.getItemDetail(16) ~= nil and turtle.getItemDetail(16).name == "minecraft:torch" then
            turtle.select(16)
            turtle.placeDown()
            turtle.select(2)
        end

        if i % 15 == 0 then
            check()
        end

        turtle.forward()
    end
end

local function main()
    for k=1,tunnels do
        length()

        if startLeft then
            turtle.turnLeft()
        else
            turtle.turnRight()
        end

        for k=1,buffer + 1 do
            height()
            turtle.forward()
        end

        if startLeft then
            turtle.turnLeft()
            startLeft = false
        else
            turtle.turnRight()
            startLeft = true
        end
    end
end

main()