veinmine

local facing = 0 -- everything will be done in local space just because it's simple and easy to add
local startPos = vector.new(0,0,0)
local currentPos = startPos
local lastMinedBlockPos = startPos
local lastMinedTurtlePos = startPos

function getVeinmineBlockData() -- called at the start of the program
    local block, data = turtle.inspect()

    if not block then
        block, data = turtle.inspectDown()
        if not block then
            block, data = turtle.inspectUp()
        end
    end

    return data
end

local veinblock = getVeinmineBlockData()

function inspect(dir)
    local block, data = turtle.inspect()

    if dir < 0 then
        block, data = turtle.inspectDown()
    elseif dir > 0 then
        block, data = turtle.inspectUp()
    end

    if block then
        if data.name == veinblock.name then
            return true
        else
            return false
        end
    else
        return false
    end
end

function dig(dir)
    if dir == 0 then
        turtle.dig()

        local change = vector.new(0,0,0)

        if facing == 0 then
            change = vector.new(0,0,-1)
        elseif facing == 1 then
            change = vector.new(1,0,0)
        elseif facing == 2 then
            change = vector.new(0,0,1)
        elseif facing == 3 then
            change = vector.new(-1,0,0)
        end

        lastMinedBlockPos = currentPos + change
    end

    if dir < 0 then
        turtle.digDown()

        lastMinedBlockPos = currentPos + vector.new(0,-1,0)
    end

    if dir > 0 then
        turtle.digUp()

        lastMinedBlockPos = currentPos + vector.new(0,1,0)
    end
end

function turn(dir)
    if dir < 0 then
        turtle.turnLeft()

        facing = facing - 1

        if facing < 0 then
            facing = 3
        end
    elseif dir > 0 then
        turtle.turnRight()

        facing = facing + 1

        if facing > 3 then
            facing = 0
        end
    end

    --print((facing == 0 and "North") or (facing == 1 and "East") or (facing == 2 and "South") or (facing == 3 and "West"))
end

function lookForVeinmineBlock(depth) -- call if we can't find any blocks
    local ahead, above, below = inspect(0) , inspect(1), inspect(-1)
    local canSeeVeinBlock = ahead or above or below

    print(depth, canSeeVeinBlock)

    if not canSeeVeinBlock then
        turn(1)

        if depth > 3 then
            repeat turtle.down() until turtle.detectDown()
            return true
        end

        lookForVeinmineBlock(depth + 1)
        return false
    end

    if above then
        dig(1)
    end

    if ahead then
        dig(0)
    end

    if below then
        dig(-1)
    end

    local difference = currentPos - lastMinedBlockPos

    if difference.z == 1 then -- north* of the turtle *(north in relative space)
        if facing == 0 then
            turtle.forward()
        elseif facing == 1 then
            turn(-1)
            turtle.forward()
        elseif facing == 2 then
            turn(-1)
            turn(-1)
            turtle.forward()
        elseif facing == 3 then
            turn(1)
            turtle.forward()
        end
    elseif difference.z == -1 then -- south of the turtle
        if facing == 0 then
            turn(-1)
            turn(-1)
            turtle.forward()
        elseif facing == 1 then
            turn(1)
            turtle.forward()
        elseif facing == 2 then
            turtle.forward()
        elseif facing == 3 then
            turn(-1)
            turtle.forward()
        end
    elseif difference.x == 1 then -- east of the turtle
        if facing == 0 then
           turn(1)
           turtle.forward()
        elseif facing == 1 then
            turn(-1)
            turn(-1)
            turtle.forward()
        elseif facing == 2 then
            turn(-1)
            turtle.forward()
        elseif facing == 3 then
            turtle.forward()
        end
    elseif difference.x == -1 then -- west of the turtle
        if facing == 0 then
            turn(-1)
            turtle.forward()
        elseif facing == 1 then
            turtle.forward()
        elseif facing == 2 then
            turn(1)
            turtle.forward()
        elseif facing == 3 then
            turn(1)
            turn(1)
            turtle.forward()
        end
    elseif difference.y == -1 then
        turtle.up()
    elseif difference.y == 1 then
        turtle.down()
    end

    return false
end

while true do
    if lookForVeinmineBlock(0) then
        break
    end
end