def proj_porvoo(x, y):
    """Project Porvoo coordinates into KKJ3 (EPSG:2393).

    https://www.porvoo.fi/koordinaatti-ja-korkeusjarjestelma
    """
    # pylint: disable=invalid-name
    output_epsg = "EPSG:2393"
    P = x - 6699461.017
    I = y - 427129.490
    x = 6699460.034 + 1.0000817225 * P - 0.0000927982 * I
    y = 3427132.007 + 1.0000817225 * I + 0.0000927982 * P

    return x, y, output_epsg