pos1 = getPosition(object1) -- player
pos2 = getPosition(object2) -- enemy

-- get the direction of object2 if it's face is oriented toward the Y axis
dir2 = getRotatedVector(object2, vec3(0, 1, 0))

-- get the vector between object1 and object2
vec = pos1 - pos2

-- find the angle between dir2 and vec
dotValue = dot(normalize(dir2), normalize(vec)) -- dot product returns the cosinus of the angle
angle = math.acos(dotValue) -- get the angle in radian
angle = math.deg(angle) -- convert to degree

-- get 2d vector length
function getLength2d(vec)

    return math.sqrt(vec[1]*vec[1] + vec[2]*vec[2])

end

-- normalize 2d vector
function normalize2d(vec)

    length = getLength2d(vec)
    vec[1] = vec[1] / length
    vec[2] = vec[2] / length
    return vec

end

function lookAt(object, dir, rotSpeed)

    -- compute object X dir and Y dir
    rot = getRotation(object)

    zAngle = math.rad(rot[3])
    sinZ = math.sin(zAngle)
    cosZ = math.cos(zAngle)

    YDir = normalize2d({sinZ, -cosZ})
    XDir = {-YDir[2], YDir[1]}

    -- dot products for orientation and angle
    ori = (dir[1]*XDir[1] + dir[2]*XDir[2])
    angle = math.acos(dir[1]*YDir[1] + dir[2]*YDir[2])

    if ori < 0 then
        angle = - angle
    end

    rotate(object, {0, 0, 1}, math.deg(angle) * rotSpeed)

end

pos1 = getPosition(obj1) -- use getTransformedPosition instead of getPosition if the objects are parented
pos2 = getPosition(obj2)
distance = length(pos2 - pos1)