netlist ¤

def build_net_map(netlist: dict) -> tuple[dict[str, int], int]:
    """Maps every port (e.g. 'R1,p1') to a generic Node Index (integer).

    Returns:
        port_to_idx: dict mapping 'Instance,Pin' -> int index
        num_nets: Total number of unique electrical nodes (excluding Ground).

    """
    g = nx.Graph()

    for src, targets in netlist.get("connections", {}).items():
        if isinstance(targets, str):
            targets = [targets]
        for tgt in targets:
            g.add_edge(src, tgt)

    for net in netlist.get("nets", []):
        g.add_edge(net["p1"], net["p2"])

    components = list(nx.connected_components(g))
    components.sort(key=lambda x: natsorted(list(x))[0])

    port_to_idx = {}
    current_idx = 1

    for comp in components:
        is_ground = any("GND" in node for node in comp)
        net_id = 0 if is_ground else current_idx

        for node in comp:
            port_to_idx[node] = net_id

        if not is_ground:
            current_idx += 1

    return port_to_idx, current_idx

def build_net_map_kfnetlist(nl: kfnl.Netlist) -> tuple[dict[str, int], int]:
    """Map every port in a kfnetlist.Netlist to a node index.

    Each ``Net`` in the netlist becomes one electrical node.  Nets
    containing a ground instance port, or a synthetic net label containing
    ``"GND"``, are assigned node index 0.

    Returns:
        port_to_idx: ``{"Instance,port": node_id, ...}``
        num_nets: next free node index (== number of non-ground nets + 1).

    """
    port_to_idx: dict[str, int] = {}
    current_idx = 1

    for net in nl.nets:
        is_ground = any(
            (
                isinstance(m, kfnl.PortRef)
                and (m.instance == "GND" or (m.instance in nl.instances and nl.instances[m.instance].component == "ground"))
            )
            or (isinstance(m, kfnl.NetlistPort) and "GND" in m.name)
            for m in net
        )
        net_id = 0 if is_ground else current_idx

        for member in net:
            if isinstance(member, kfnl.PortRef):
                port_to_idx[f"{member.instance},{member.port}"] = net_id
            elif isinstance(member, kfnl.NetlistPort):
                port_to_idx[member.name] = net_id

        if not is_ground:
            current_idx += 1

    return port_to_idx, current_idx

def draw_circuit_graph(  # noqa: C901, PLR0912, PLR0915
    netlist: dict[str, dict] | kfnl.Netlist,
    layout_attempts: int = 10,
    *,
    show: bool = True,
) -> mpl.figure.Figure:
    """Visualize a circuit netlist as a connectivity graph.

    Accepts either a SAX-format dict or a ``kfnetlist.Netlist``.

    Args:
        netlist: Circuit description (SAX dict or kfnetlist.Netlist).
        show: If ``True``, call ``plt.show()`` before returning.
        layout_attempts: Number of spring-layout seeds to try.

    Returns:
        The :class:`matplotlib.figure.Figure` containing the rendered graph.

    """
    if isinstance(netlist, kfnl.Netlist):
        port_map, _ = build_net_map_kfnetlist(netlist)
        instance_names = list(netlist.instances)
    else:
        port_map, _ = build_net_map(netlist)
        instance_names = list(netlist.get("instances", {}))

    G = nx.Graph()

    for name in instance_names:
        if name == "GND":
            G.add_node(name, color="black", size=1500, label=name)
        else:
            G.add_node(name, color="red", size=2000, label=name)

    net_groups = {}

    for port_str, net_idx in port_map.items():
        if "," not in port_str:
            continue

        inst_name, pin_name = port_str.split(",", 1)

        G.add_node(port_str, color="skyblue", size=300, label=pin_name, parent=inst_name)

        if inst_name in G.nodes:
            G.add_edge(inst_name, port_str, weight=10, type="internal")

        if net_idx not in net_groups:
            net_groups[net_idx] = []
        net_groups[net_idx].append(port_str)

    edge_labels = {}

    for net_idx, ports in net_groups.items():
        if len(ports) > 1:
            for i in range(len(ports) - 1):
                u, v = ports[i], ports[i + 1]
                G.add_edge(u, v, weight=1, type="external")
                edge_labels[(u, v)] = str(net_idx)

    def make_initial_pos(seed: int) -> dict:
        rng = np.random.default_rng(seed)
        pos = {}
        instance_nodes = [n for n, d in G.nodes(data=True) if d.get("color") in ["red", "black"]]

        # Place instances on a rough grid / random spread
        for name in instance_nodes:
            pos[name] = rng.uniform(-1, 1, size=2)

        # Place each port with a small random offset from its parent
        for n, d in G.nodes(data=True):
            if d.get("color") == "skyblue":
                parent = d.get("parent")
                if parent and parent in pos:
                    pos[n] = pos[parent] + rng.uniform(-0.1, 0.1, size=2)
                else:
                    pos[n] = rng.uniform(-1, 1, size=2)
        return pos

    def count_crossings(pos: dict[str, np.ndarray]) -> int:

        def segments_intersect(p1: np.ndarray, p2: np.ndarray, p3: np.ndarray, p4: np.ndarray) -> bool:

            def cross(o: np.ndarray, a: np.ndarray, b: np.ndarray) -> float:
                return float((a[0] - o[0]) * (b[1] - o[1]) - (a[1] - o[1]) * (b[0] - o[0]))

            d1 = cross(p3, p4, p1)
            d2 = cross(p3, p4, p2)
            d3 = cross(p1, p2, p3)
            d4 = cross(p1, p2, p4)

            return bool(((d1 > 0 and d2 < 0) or (d1 < 0 and d2 > 0)) and ((d3 > 0 and d4 < 0) or (d3 < 0 and d4 > 0)))

        edges = list(G.edges())
        crossings = 0
        for i in range(len(edges)):
            for j in range(i + 1, len(edges)):
                u1, v1 = edges[i]
                u2, v2 = edges[j]
                # Skip pairs that share a node (adjacent edges always "meet", not cross)
                if u1 in (u2, v2) or v1 in (u2, v2):
                    continue
                p1, p2 = pos[u1], pos[v1]
                p3, p4 = pos[u2], pos[v2]
                if segments_intersect(p1, p2, p3, p4):
                    crossings += 1
        return crossings

    best_pos = None
    best_crossings = float("inf")

    for attempt in range(layout_attempts):
        seed = attempt  # deterministic across runs with same layout_attempts
        init_pos = make_initial_pos(seed)
        candidate_pos = nx.spring_layout(
            G,
            pos=init_pos,  # warm start near the desired structure
            fixed=None,  # let everything move, but start well
            k=0.5,
            iterations=80,  # more iterations since we have a good warm start
            weight="weight",
            seed=seed,
        )
        crossings = count_crossings(candidate_pos)
        if crossings < best_crossings:
            best_crossings = crossings
            best_pos = candidate_pos

    pos = best_pos

    fig = plt.figure(figsize=(10, 8))

    instance_nodes = [n for n, d in G.nodes(data=True) if d.get("color") in ["red", "black"]]
    port_nodes = [n for n, d in G.nodes(data=True) if d.get("color") == "skyblue"]

    nx.draw_networkx_nodes(
        G,
        pos,
        nodelist=instance_nodes,
        node_color=[G.nodes[n]["color"] for n in instance_nodes],
        node_size=[G.nodes[n]["size"] for n in instance_nodes],
    )

    nx.draw_networkx_labels(
        G,
        pos,
        labels={n: n for n in instance_nodes},
        font_color="white",
        font_weight="bold",
    )

    nx.draw_networkx_nodes(G, pos, nodelist=port_nodes, node_color="skyblue", node_size=300)

    port_labels = {n: G.nodes[n]["label"] for n in port_nodes}
    nx.draw_networkx_labels(G, pos, labels=port_labels, font_size=8, font_color="black")

    internal_edges = [(u, v) for u, v, d in G.edges(data=True) if d.get("type") == "internal"]
    nx.draw_networkx_edges(G, pos, edgelist=internal_edges, width=2.0, alpha=0.5)

    external_edges = [(u, v) for u, v, d in G.edges(data=True) if d.get("type") == "external"]
    nx.draw_networkx_edges(G, pos, edgelist=external_edges, width=1.5, style="dashed", edge_color="gray")

    nx.draw_networkx_edge_labels(G, pos, edge_labels=edge_labels, font_color="blue")

    ax = plt.gca()
    ax.set_title("Circuit Connectivity Graph")
    ax.axis("off")
    fig.tight_layout()

    if show:
        plt.show()

    return fig

def sax_to_kfnetlist(
    sax_dict: dict,
) -> tuple[kfnl.Netlist, dict[str, dict[str, Any]]]:
    """Convert a SAX-format netlist dict to a ``kfnetlist.Netlist``.

    Pairwise SAX ``connections`` (and GDSFactory-style ``nets`` lists)
    are grouped into equivalence classes via union-find, then emitted as
    one ``kfnetlist.Net`` per class.

    Returns:
        A 2-tuple ``(netlist, settings_override)`` where
        *settings_override* maps instance names to their full settings
        dict (including non-JSON-safe values such as complex numbers).
        When all settings are JSON-safe the override dict is empty.

    """
    nl = kfnl.Netlist()
    settings_override: dict[str, dict[str, Any]] = {}

    # --- instances ---
    for name, data in sax_dict.get("instances", {}).items():
        raw_settings = data.get("settings") or {}
        safe_settings = {k: v for k, v in raw_settings.items() if _is_json_safe(v)}
        nl.create_inst(
            name=name,
            kcl="",
            component=data["component"],
            settings=safe_settings or None,
        )
        if len(safe_settings) != len(raw_settings):
            settings_override[name] = raw_settings

    # --- ports ---
    declared_ports: set[str] = set()
    top_port_targets: list[tuple[str, str]] = []
    for port_name, target in sax_dict.get("ports", {}).items():
        nl.create_port(port_name)
        declared_ports.add(port_name)
        top_port_targets.append((port_name, target))

    # --- connectivity: union-find over SAX connections + GDSFactory nets ---
    parent: dict[str, str] = {}

    def _find(x: str) -> str:
        if x not in parent:
            parent[x] = x
        while parent[x] != x:
            parent[x] = parent[parent[x]]
            x = parent[x]
        return x

    def _union(a: str, b: str) -> None:
        ra, rb = _find(a), _find(b)
        if ra != rb:
            parent[ra] = rb

    known_instances = set(sax_dict.get("instances", {}))

    def _net_member_ref(port_str: str) -> kfnl.PortRef | kfnl.NetlistPort:
        if "," not in port_str:
            msg = f"Expected SAX port reference 'instance,port', got {port_str!r}"
            raise ValueError(msg)
        inst, _port = port_str.split(",", 1)
        if inst not in known_instances:
            if port_str not in declared_ports:
                nl.create_port(port_str)
                declared_ports.add(port_str)
            return kfnl.NetlistPort(port_str)
        return kfnl.PortRef(instance=inst, port=_port)

    for src, targets in sax_dict.get("connections", {}).items():
        if isinstance(targets, str):
            targets = [targets]
        for tgt in targets:
            _find(src)
            _find(tgt)
            _union(src, tgt)

    for net_entry in sax_dict.get("nets", []):
        p1, p2 = net_entry["p1"], net_entry["p2"]
        _find(p1)
        _find(p2)
        _union(p1, p2)

    for _port_name, target in top_port_targets:
        _find(target)

    # Group ports by their root → one kfnetlist.Net per group
    groups: dict[str, list[str]] = defaultdict(list)
    for port in parent:
        groups[_find(port)].append(port)

    top_ports_by_root: dict[str, list[str]] = defaultdict(list)
    for port_name, target in top_port_targets:
        top_ports_by_root[_find(target)].append(port_name)

    for root, members in groups.items():
        refs = [kfnl.NetlistPort(port_name) for port_name in top_ports_by_root.get(root, [])]
        for port_str in sorted(members):
            refs.append(_net_member_ref(port_str))
        nl.create_net(*refs)

    nl.sort()
    return nl, settings_override