server/lynxkite_ops.py

"""Graph analytics operations. To be split into separate files when we have more."""

import os
from . import ops
from collections import deque
import dataclasses
import functools
import matplotlib
import networkx as nx
import pandas as pd
import polars as pl
import traceback
import typing

op = ops.op_registration("LynxKite")


@dataclasses.dataclass
class RelationDefinition:
    """Defines a set of edges."""

    df: str  # The DataFrame that contains the edges.
    source_column: (
        str  # The column in the edge DataFrame that contains the source node ID.
    )
    target_column: (
        str  # The column in the edge DataFrame that contains the target node ID.
    )
    source_table: str  # The DataFrame that contains the source nodes.
    target_table: str  # The DataFrame that contains the target nodes.
    source_key: str  # The column in the source table that contains the node ID.
    target_key: str  # The column in the target table that contains the node ID.


@dataclasses.dataclass
class Bundle:
    """A collection of DataFrames and other data.

    Can efficiently represent a knowledge graph (homogeneous or heterogeneous) or tabular data.
    It can also carry other data, such as a trained model.
    """

    dfs: dict[str, pd.DataFrame] = dataclasses.field(default_factory=dict)
    relations: list[RelationDefinition] = dataclasses.field(default_factory=list)
    other: dict[str, typing.Any] = None

    @classmethod
    def from_nx(cls, graph: nx.Graph):
        edges = nx.to_pandas_edgelist(graph)
        d = dict(graph.nodes(data=True))
        nodes = pd.DataFrame(d.values(), index=d.keys())
        nodes["id"] = nodes.index
        return cls(
            dfs={"edges": edges, "nodes": nodes},
            relations=[
                RelationDefinition(
                    df="edges",
                    source_column="source",
                    target_column="target",
                    source_table="nodes",
                    target_table="nodes",
                    source_key="id",
                    target_key="id",
                )
            ],
        )

    @classmethod
    def from_df(cls, df: pd.DataFrame):
        return cls(dfs={"df": df})

    def to_nx(self):
        # TODO: Use relations.
        graph = nx.from_pandas_edgelist(self.dfs["edges"])
        if "nodes" in self.dfs:
            nx.set_node_attributes(
                graph, self.dfs["nodes"].set_index("id").to_dict("index")
            )
        return graph

    def copy(self):
        """Returns a medium depth copy of the bundle. The Bundle is completely new, but the DataFrames and RelationDefinitions are shared."""
        return Bundle(
            dfs=dict(self.dfs),
            relations=list(self.relations),
            other=dict(self.other) if self.other else None,
        )


def nx_node_attribute_func(name):
    """Decorator for wrapping a function that adds a NetworkX node attribute."""

    def decorator(func):
        @functools.wraps(func)
        def wrapper(graph: nx.Graph, **kwargs):
            graph = graph.copy()
            attr = func(graph, **kwargs)
            nx.set_node_attributes(graph, attr, name)
            return graph

        return wrapper

    return decorator


def disambiguate_edges(ws):
    """If an input plug is connected to multiple edges, keep only the last edge."""
    seen = set()
    for edge in reversed(ws.edges):
        if (edge.target, edge.targetHandle) in seen:
            ws.edges.remove(edge)
        seen.add((edge.target, edge.targetHandle))


@ops.register_executor("LynxKite")
async def execute(ws):
    catalog = ops.CATALOGS["LynxKite"]
    disambiguate_edges(ws)
    outputs = {}
    failed = 0
    while len(outputs) + failed < len(ws.nodes):
        for node in ws.nodes:
            if node.id in outputs:
                continue
            # TODO: Take the input/output handles into account.
            inputs = [edge.source for edge in ws.edges if edge.target == node.id]
            if all(input in outputs for input in inputs):
                inputs = [outputs[input] for input in inputs]
                data = node.data
                op = catalog[data.title]
                params = {**data.params}
                # Convert inputs.
                try:
                    for i, (x, p) in enumerate(zip(inputs, op.inputs.values())):
                        if p.type == nx.Graph and isinstance(x, Bundle):
                            inputs[i] = x.to_nx()
                        elif p.type == Bundle and isinstance(x, nx.Graph):
                            inputs[i] = Bundle.from_nx(x)
                        elif p.type == Bundle and isinstance(x, pd.DataFrame):
                            inputs[i] = Bundle.from_df(x)
                    output = op(*inputs, **params)
                except Exception as e:
                    traceback.print_exc()
                    data.error = str(e)
                    failed += 1
                    continue
                if len(op.inputs) == 1 and op.inputs.get("multi") == "*":
                    # It's a flexible input. Create n+1 handles.
                    data.inputs = {f"input{i}": None for i in range(len(inputs) + 1)}
                data.error = None
                outputs[node.id] = output
                if (
                    op.type == "visualization"
                    or op.type == "table_view"
                    or op.type == "image"
                ):
                    data.display = output


@op("Import Parquet")
def import_parquet(*, filename: str):
    """Imports a Parquet file."""
    return pd.read_parquet(filename)


@op("Import CSV")
def import_csv(
    *, filename: str, columns: str = "<from file>", separator: str = "<auto>"
):
    """Imports a CSV file."""
    return pd.read_csv(
        filename,
        names=pd.api.extensions.no_default
        if columns == "<from file>"
        else columns.split(","),
        sep=pd.api.extensions.no_default if separator == "<auto>" else separator,
    )


@op("Create scale-free graph")
def create_scale_free_graph(*, nodes: int = 10):
    """Creates a scale-free graph with the given number of nodes."""
    return nx.scale_free_graph(nodes)


@op("Compute PageRank")
@nx_node_attribute_func("pagerank")
def compute_pagerank(graph: nx.Graph, *, damping=0.85, iterations=100):
    return nx.pagerank(graph, alpha=damping, max_iter=iterations)


@op("Compute betweenness centrality")
@nx_node_attribute_func("betweenness_centrality")
def compute_betweenness_centrality(graph: nx.Graph, *, k=10):
    return nx.betweenness_centrality(graph, k=k, backend="cugraph")


@op("Discard loop edges")
def discard_loop_edges(graph: nx.Graph):
    graph = graph.copy()
    graph.remove_edges_from(nx.selfloop_edges(graph))
    return graph


@op("SQL")
def sql(bundle: Bundle, *, query: ops.LongStr, save_as: str = "result"):
    """Run a SQL query on the DataFrames in the bundle. Save the results as a new DataFrame."""
    bundle = bundle.copy()
    if os.environ.get("NX_CUGRAPH_AUTOCONFIG", "").strip().lower() == "true":
        with pl.Config() as cfg:
            cfg.set_verbose(True)
            res = (
                pl.SQLContext(bundle.dfs)
                .execute(query)
                .collect(engine="gpu")
                .to_pandas()
            )
            # TODO: Currently `collect()` moves the data from cuDF to Polars. Then we convert it to Pandas,
            # which (hopefully) puts it back into cuDF. Hopefully we will be able to keep it in cuDF.
    else:
        res = pl.SQLContext(bundle.dfs).execute(query).collect().to_pandas()
    bundle.dfs[save_as] = res
    return bundle


@op("Organize bundle")
def organize_bundle(bundle: Bundle, *, code: ops.LongStr):
    """Lets you rename/copy/delete DataFrames, and modify relations. TODO: Use a declarative solution instead of Python code. Add UI."""
    bundle = bundle.copy()
    exec(code, globals(), {"bundle": bundle})
    return bundle


@op("Sample graph")
def sample_graph(graph: nx.Graph, *, nodes: int = 100):
    """Takes a (preferably connected) subgraph."""
    sample = set()
    to_expand = deque([0])
    while to_expand and len(sample) < nodes:
        node = to_expand.pop()
        for n in graph.neighbors(node):
            if n not in sample:
                sample.add(n)
                to_expand.append(n)
            if len(sample) == nodes:
                break
    return nx.Graph(graph.subgraph(sample))


def _map_color(value):
    cmap = matplotlib.cm.get_cmap("viridis")
    value = (value - value.min()) / (value.max() - value.min())
    rgba = cmap(value)
    return [
        "#{:02x}{:02x}{:02x}".format(int(r * 255), int(g * 255), int(b * 255))
        for r, g, b in rgba[:, :3]
    ]


@op("Visualize graph", view="visualization")
def visualize_graph(graph: Bundle, *, color_nodes_by: ops.NodeAttribute = None):
    nodes = graph.dfs["nodes"].copy()
    if color_nodes_by:
        nodes["color"] = _map_color(nodes[color_nodes_by])
    nodes = nodes.to_records()
    edges = graph.dfs["edges"].drop_duplicates(["source", "target"])
    edges = edges.to_records()
    pos = nx.spring_layout(graph.to_nx(), iterations=max(1, int(10000 / len(nodes))))
    v = {
        "animationDuration": 500,
        "animationEasingUpdate": "quinticInOut",
        "series": [
            {
                "type": "graph",
                "roam": True,
                "lineStyle": {
                    "color": "gray",
                    "curveness": 0.3,
                },
                "emphasis": {
                    "focus": "adjacency",
                    "lineStyle": {
                        "width": 10,
                    },
                },
                "data": [
                    {
                        "id": str(n.id),
                        "x": float(pos[n.id][0]),
                        "y": float(pos[n.id][1]),
                        # Adjust node size to cover the same area no matter how many nodes there are.
                        "symbolSize": 50 / len(nodes) ** 0.5,
                        "itemStyle": {"color": n.color} if color_nodes_by else {},
                    }
                    for n in nodes
                ],
                "links": [
                    {"source": str(r.source), "target": str(r.target)} for r in edges
                ],
            },
        ],
    }
    return v


def collect(df: pd.DataFrame):
    if isinstance(df, pl.LazyFrame):
        df = df.collect()
    if isinstance(df, pl.DataFrame):
        return [[d[c] for c in df.columns] for d in df.to_dicts()]
    return df.values.tolist()


@op("View tables", view="table_view")
def view_tables(bundle: Bundle):
    v = {
        "dataframes": {
            name: {
                "columns": [str(c) for c in df.columns],
                "data": collect(df),
            }
            for name, df in bundle.dfs.items()
        },
        "relations": bundle.relations,
        "other": bundle.other,
    }
    return v