Euler

def bend_euler_factory(
    kcl: KCLayout,
    *,
    output_type: type[KC] | None = None,
    additional_info: Callable[
        ...,
        dict[str, MetaData],
    ]
    | dict[str, MetaData]
    | None = None,
    port_type: str = "optical",
    **cell_kwargs: Unpack[CellKWargs],
) -> BendEulerFactory[KC]:
    """Returns a function generating euler bends.

    Will snap ports by default

    Args:
        kcl: The KCLayout which will be owned
        additional_info: Add additional key/values to the
            [`KCell.info`][kfactory.settings.Info]. Can be a static dict
            mapping info name to info value. Or can a callable which takes the straight
            functions' parameters as kwargs and returns a dict with the mapping.
        cell_kwargs: Additional arguments passed as `@kcl.cell(**cell_kwargs)`.
    """
    _additional_info: dict[str, MetaData] = {}
    if _is_additional_info_func(additional_info):
        _additional_info_func: Callable[
            ...,
            dict[str, MetaData],
        ] = additional_info
    else:

        def additional_info_func(
            **kwargs: Any,
        ) -> dict[str, MetaData]:
            return {}

        _additional_info_func = additional_info_func
        _additional_info = additional_info or {}  # ty:ignore[invalid-assignment]
    if cell_kwargs.get("snap_ports") is None:
        cell_kwargs["snap_ports"] = False

    if output_type is not None:
        cell = kcl.cell(output_type=output_type, **cell_kwargs)
    else:
        cell = kcl.cell(output_type=cast("type[KC]", KCell), **cell_kwargs)

    @cell
    def bend_euler(
        width: um,
        radius: um,
        layer: kdb.LayerInfo,
        enclosure: LayerEnclosure | None = None,
        angle: deg = 90,
        resolution: float = 150,
    ) -> KCell:
        """Create a euler bend.

        Args:
            width: Width of the core. [um]
            radius: Radius off the backbone. [um]
            layer: Layer index / LayerEnum of the core.
            enclosure: Slab/exclude definition. [dbu]
            angle: Angle of the bend.
            resolution: Angle resolution for the backbone.
        """
        c = kcl.kcell()
        if angle < 0:
            logger.critical(
                f"Negative lengths are not allowed {angle} as ports"
                " will be inverted. Please use a positive number. Forcing positive"
                " lengths."
            )
            angle = -angle
        if width < 0:
            logger.critical(
                f"Negative widths are not allowed {width} as ports"
                " will be inverted. Please use a positive number. Forcing positive"
                " lengths."
            )
            width = -width
        backbone = euler_bend_points(angle, radius=radius, resolution=resolution)

        center_path = extrude_path(
            target=c,
            layer=layer,
            path=backbone,
            width=width,
            enclosure=enclosure,
            start_angle=0,
            end_angle=angle,
        )
        li = c.kcl.layer(layer)
        c.create_port(
            name="o1",
            layer=li,
            width=c.kcl.to_dbu(width),
            trans=kdb.Trans(2, False, c.kcl.to_dbu(backbone[0]).to_v()),
        )

        if abs(angle % 90) < 0.001:
            _ang = round(angle)
            c.create_port(
                name="o2",
                trans=kdb.Trans(_ang // 90, False, c.kcl.to_dbu(backbone[-1]).to_v()),
                width=round(width / c.kcl.dbu),
                layer=li,
                port_type=port_type,
            )
        else:
            c.create_port(
                name="o2",
                dcplx_trans=kdb.DCplxTrans(1, angle, False, backbone[-1].to_v()),
                width=c.kcl.to_dbu(width),
                layer=li,
                port_type=port_type,
            )
        _info: dict[str, MetaData] = {}
        _info.update(
            _additional_info_func(
                width=width,
                radius=radius,
                layer=li,
                enclosure=enclosure,
                angle=angle,
                resolution=resolution,
            )
        )
        _info.update(_additional_info)
        c.info = Info(**_info)
        c.boundary = center_path

        c.auto_rename_ports()
        return c

    return bend_euler

def bend_s_euler_factory(
    kcl: KCLayout,
    output_type: type[KC] | None = None,
    additional_info: Callable[
        ...,
        dict[str, MetaData],
    ]
    | dict[str, MetaData]
    | None = None,
    port_type: str = "optical",
    **cell_kwargs: Unpack[CellKWargs],
) -> BendSEulerFactory[KC]:
    """Returns a function generating euler s-bends.

    Args:
        kcl: The KCLayout which will be owned
        additional_info: Add additional key/values to the
            [`KCell.info`][kfactory.settings.Info]. Can be a static dict
            mapping info name to info value. Or can a callable which takes the straight
            functions' parameters as kwargs and returns a dict with the mapping.
        cell_kwargs: Additional arguments passed as `@kcl.cell(**cell_kwargs)`.
    """
    _additional_info: dict[str, MetaData] = {}
    if _is_additional_info_func(additional_info):
        _additional_info_func: Callable[
            ...,
            dict[str, MetaData],
        ] = additional_info
    else:

        def additional_info_func(
            **kwargs: Any,
        ) -> dict[str, MetaData]:
            return {}

        _additional_info_func = additional_info_func
        _additional_info = additional_info or {}  # ty:ignore[invalid-assignment]
    if output_type is not None:
        cell = kcl.cell(output_type=output_type, **cell_kwargs)
    else:
        cell = kcl.cell(output_type=cast("type[KC]", KCell), **cell_kwargs)

    @cell
    def bend_s_euler(
        offset: um,
        width: um,
        radius: um,
        layer: kdb.LayerInfo,
        enclosure: LayerEnclosure | None = None,
        resolution: float = 150,
    ) -> KCell:
        """Create a euler s-bend.

        Args:
            offset: Offset between left/right. [um]
            width: Width of the core. [um]
            radius: Radius off the backbone. [um]
            layer: Layer index / LayerEnum of the core.
            enclosure: Slab/exclude definition. [dbu]
            resolution: Angle resolution for the backbone.
        """
        c = kcl.kcell()
        if width < 0:
            logger.critical(
                f"Negative widths are not allowed {width} as ports"
                " will be inverted. Please use a positive number. Forcing positive"
                " lengths."
            )
            width = -width
        backbone = euler_sbend_points(
            offset=offset,
            radius=radius,
            resolution=resolution,
        )
        center_path = extrude_path(
            target=c,
            layer=layer,
            path=backbone,
            width=width,
            enclosure=enclosure,
            start_angle=0,
            end_angle=0,
        )

        v = backbone[-1] - backbone[0]
        if v.x < 0:
            p1 = c.kcl.to_dbu(backbone[-1])
            p2 = c.kcl.to_dbu(backbone[0])
        else:
            p1 = c.kcl.to_dbu(backbone[0])
            p2 = c.kcl.to_dbu(backbone[-1])
        li = c.kcl.layer(layer)
        c.create_port(
            name="o1",
            trans=kdb.Trans(2, False, p1.to_v()),
            width=c.kcl.to_dbu(width),
            port_type=port_type,
            layer=li,
        )
        c.create_port(
            name="o2",
            trans=kdb.Trans(0, False, p2.to_v()),
            width=c.kcl.to_dbu(width),
            port_type=port_type,
            layer=li,
        )
        c.boundary = center_path
        _info: dict[str, MetaData] = {}
        _info.update(
            _additional_info_func(
                offset=offset,
                width=width,
                radius=radius,
                layer=layer,
                enclosure=enclosure,
                resolution=resolution,
            )
        )
        _info.update(_additional_info)
        c.info = Info(**_info)

        c.auto_rename_ports()
        return c

    return bend_s_euler

def euler_bend_points(
    angle_amount: deg = 90, radius: um = 100, resolution: float = 150
) -> list[kdb.DPoint]:
    """Base euler bend, no transformation, emerging from the origin."""
    if angle_amount < 0:
        raise ValueError(f"angle_amount should be positive. Got {angle_amount}")
    # End angle
    eth = angle_amount * np.pi / 180

    # If bend is trivial, return a trivial shape
    if eth == 0:
        return [kdb.DPoint(0, 0)]

    # Total displaced angle
    th = eth / 2

    # Total length of curve
    total_length = 4 * radius * th

    # Compute curve ##
    a = np.sqrt(radius**2 * np.abs(th))
    sq2pi = np.sqrt(2 * np.pi)

    # Function for computing curve coords
    (fasin, facos) = fresnel(np.sqrt(2 / np.pi) * radius * th / a)

    def _xy(s: float) -> kdb.DPoint:
        if th == 0:
            return kdb.DPoint(0, 0)
        if s <= total_length / 2:
            (fsin, fcos) = fresnel(s / (sq2pi * a))
            x = sq2pi * a * fcos
            y = sq2pi * a * fsin
        else:
            (fsin, fcos) = fresnel((total_length - s) / (sq2pi * a))
            x = (
                sq2pi
                * a
                * (
                    facos
                    + np.cos(2 * th) * (facos - fcos)
                    + np.sin(2 * th) * (fasin - fsin)
                )
            )
            y = (
                sq2pi
                * a
                * (
                    fasin
                    - np.cos(2 * th) * (fasin - fsin)
                    + np.sin(2 * th) * (facos - fcos)
                )
            )
        return kdb.DPoint(x, y)

    # Parametric step size
    step = total_length / max(int(th * resolution), 1)

    # Generate points
    return [_xy(i * step) for i in range(round(total_length / step) + 1)]

def euler_endpoint(
    start_point: tuple[float, float] = (0.0, 0.0),
    radius: um = 10.0,
    input_angle: deg = 0.0,
    angle_amount: deg = 90.0,
) -> tuple[float, float]:
    """Gives the end point of a simple Euler bend as a i3.Coord2."""
    th = abs(angle_amount) * np.pi / 180 / 2
    clockwise = angle_amount < 0

    (fsin, fcos) = fresnel(np.sqrt(2 * th / np.pi))

    a = 2 * np.sqrt(2 * np.pi * th) * (np.cos(th) * fcos + np.sin(th) * fsin)
    r = a * radius
    x = r * np.cos(th)
    y = r * np.sin(th)

    if clockwise:
        y *= -1

    return x + start_point[0], y + start_point[1]

def euler_sbend_points(
    offset: um = 5.0, radius: um = 10.0e-6, resolution: float = 150
) -> list[kdb.DPoint]:
    """An Euler s-bend with parallel input and output, separated by an offset."""

    # Function to find root of
    def froot(th: float) -> float:
        end_point = euler_endpoint((0.0, 0.0), radius, 0.0, th)
        return 2 * end_point[1] - abs(offset)

    # Get direction
    direction = 1 if offset >= 0 else -1
    # Check whether offset requires straight section
    a = 0.0
    b = 90.0
    fa = froot(a)
    fb = froot(b)

    if fa * fb < 0:
        # Offset can be produced just by bends alone
        angle = direction * brentq(froot, 0.0, 90.0)
        extra_y = 0.0
    else:
        # Offset is greater than max height of bends
        angle = direction * 90.0
        extra_y = -direction * fb

    spoints = []
    right_point = []
    points_left_half = euler_bend_points(abs(angle), radius, resolution)

    # Second bend
    for pts in points_left_half:
        r_pt_x = 2 * points_left_half[-1].x - pts.x
        r_pt_y = 2 * points_left_half[-1].y - pts.y + extra_y * direction
        pts.y = pts.y * direction
        r_pt_y = r_pt_y * direction
        spoints.append(pts)
        right_point.append(kdb.DPoint(r_pt_x, r_pt_y))
    spoints += right_point[::-1]

    return spoints