mine_v5.lua

--digs 2x2 with 3d search

--globals
local input = {...}
DISTANCE = input[1]
moves = {}
index = 1
DIR = 1
M_vectors = {3, 4, 1, 2, 6, 5}

--main functions

function tunnel()
    turtle.dig()
    dig()
    turtle.forward()
    inspect_d(1)
    change_d('left')
    turtle.dig()
    dig()
    turtle.forward()
    inspect_d(1)
    inspect_d(2)
    turtle.digUp()
    digUp()
    turtle.up()
    inspect_d(2)
    inspect_d(3)
    change_d('right')
    change_d('right')
    turtle.dig()
    dig()
    turtle.forward()
    inspect_d(3)
    inspect_d(2)
    turtle.down()
    inspect_d(2)
    change_d('left')
end

function dig()
    while turtle.detect() == true do
        turtle.dig()
    end
end

function digUp()
    while turtle.detectUp() == true do
        turtle.digUp()
    end
end

function check(dir)
    local found = false
    if dir == 1 then
        is_block, data = turtle.inspectDown()
    elseif dir == 2 then
        is_block, data = turtle.inspect()
    elseif dir == 3 then
        is_block, data = turtle.inspectUp()
    end
    if is_block and data.name == 'minecraft:diamond_ore' then
        found = true
    end
    return found
end

function change_d(dir)
    if dir == 'left' then
        turtle.turnLeft()
        if DIR == 1 then
            DIR = 4
        else
            DIR = DIR -1
        end
    elseif dir == 'right' then
        turtle.turnRight()
        if DIR == 4 then
            DIR = 1
        else
            DIR = DIR + 1
        end
    end
end

function inspect_base(dir)
    local success = check(dir)
    if success and dir == 2 then
        turtle.dig()
        turtle.forward()
        moves[index] = DIR
        index = index + 1
    elseif success and dir == 1 then
        turtle.digDown()
        turtle.down()
        moves[index] = 5
        index = index + 1
    elseif success and dir == 3 then
        turtle.digUp()
        turtle.up()
        moves[index] = 6
        index = index + 1
    end
    return success
end

function inspect_loop()
    i = 1
    j = 2
    while moves[1] ~= nil do
        local found = inspect_base(j)
        if not found and j == 2 then
            change_d('right')
            i = i + 1
            if i == 5 then
                j = 1
            end
        elseif not found and j == 1 then
            j = 3
        elseif not found and j == 3 then
            reverse()
            i = 1
            j = 2
        else
            i = 1
            j = 2
        end
    end
end

function turn(goal)
    while DIR ~= goal do
        change_d('right')
    end
end

function reverse()
    index = index - 1
    i = moves[index]
    goal = M_vectors[i]
    if goal < 5 then
        turn(goal)
        turtle.forward()
        moves[index] = nil
    else
        if goal == 5 then
            turtle.down()
            moves[index] = nil
        elseif goal == 6 then
            turtle.up()
            moves[index] = nil
        end
    end
end

function inspect_d(dir)
    local current_d = DIR
    local found = inspect_base(dir)
    if found then
        inspect_loop()
        turn(current_d)
    end
end

--aux functions

function refuel()
    if turtle.getFuelLevel() < 80 then
        turtle.select(1)
        turtle.refuel(1)
    end
end

function eject()
    for i = 1, 16 do
        turtle.select(i)
        local data = turtle.getItemDetail()
        if data ~= nil and data.name == 'minecraft:cobblestone' then
            turtle.drop()
        end
    end
end

--main

function main()
    refuel()
    for i = 1, DISTANCE do
        tunnel()
        if (i % 10) == 0 then
            refuel()
            eject()
        end
        print(i)
    end
    turtle.turnRight()
    turtle.turnRight()
    eject()
    for i = 1, DISTANCE do
        turtle.forward()
    end
end

main()