Turtle

-- load the API
os.loadAPI("ocs/apis/sensor")
-- wrap the sensor
prox = sensor.wrap("right")

local NORTH, EAST, SOUTH, WEST = 0, 1, 2, 3
facing = -1

function initFacing()
    if turtle.detect() then
        turtle.dig()
    end
    local me = prox.getTargetDetails("jhnphm")
    local pos = me.Position
    local x = pos.X
    local z = pos.Z
    turtle.forward()
    me = prox.getTargetDetails("jhnphm")
    pos = me.Position
    x = pos.X-x
    z = pos.Z-z

    if math.abs(x) > math.abs(z) then
        if x > 0 then
            facing = EAST
        else
            facing = WEST
        end
    else
        if z > 0 then
            facing = SOUTH
        else
            facing = NORTH
        end
    end
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
    turtle.turnLeft()
end
function turnLeft()
    facing = (facing - 1) % 4
    turtle.turnLeft()
end
function turnRight()
    facing = (facing + 1) % 4
    turtle.turnRight()
end
function turnTo(heading)
    if heading == NORTH then
        if facing == EAST then
            turnLeft()
        elseif facing == SOUTH then
            turnLeft()
            turnLeft()
        elseif facing == WEST then
            turnRight()
        end
    elseif heading == EAST then
        if facing == SOUTH then
            turnLeft()
        elseif facing == WEST then
            turnLeft()
            turnLeft()
        elseif facing == NORTH then
            turnRight()
        end
    elseif heading == SOUTH then
        if facing == WEST then
            turnLeft()
        elseif facing == NORTH then
            turnLeft()
            turnLeft()
        elseif facing == EAST then
            turnRight()
        end
    elseif heading == WEST then
        if facing == NORTH then
            turnLeft()
        elseif facing == EAST then
            turnLeft()
            turnLeft()
        elseif facing == SOUTH then
            turnRight()
        end
    end
end


function go(x,y,z)
    print("Going to: "..x..","..y..","..z)
    local i
    if math.abs(x) > math.abs(z) then
        if math.floor(x) > 0 then
            turnTo(EAST)
            print("Turning East")
        elseif math.floor(x) < 0 then
            print("Turning West")
            turnTo(WEST)
        end
        print("Moving...")
        turtle.forward()
    else
        if math.floor(z) > 0 then
            print("Turning South")
            turnTo(SOUTH)
        elseif math.floor(z) < 0 then
            print("Turning North")
            turnTo(NORTH)
        end
        if turtle.detect() then
            return
        end
        print("Moving...")
        turtle.forward()
    end
    if math.floor(y) > 0 then
        if turtle.detectUp() then
           return
        end
        print("Moving up...")
        turtle.up()
    elseif math.floor(y) < 0 then
        if turtle.detectDown() then
            return
        end
        print("Moving down...")
        turtle.down()
    end
end


function distance(pos)
  local xd = pos.X
  local yd = pos.Y
  local zd = pos.Z
  return math.sqrt(xd*xd + yd*yd + zd*zd)
end

initFacing()

while true do
    local me = prox.getTargetDetails("jhnphm")
    local pos = me.Position
    local dist = distance(pos)
     print("Position:" ..me.Position.X..','..me.Position.Y..","..me.Position.Z)
    if dist > 4 then
        print("Dist: "..dist)
        go(pos.X, pos.Y, pos.Z)
        dist = distance(pos)
    end
    if dist > 20 then
        break
    end
end