"use client";

import { useEffect, useMemo, useState } from "react";
import type { GraphDataset } from "@/lib/catalog";
import {
  browserGraphHistory,
  exportAdjacency,
  parseGraphSearch,
  partitionIncident,
  selectNeighborhood,
  serializeGraphSearch,
  type GraphHistory,
  type GraphLocation,
  type GraphModel,
} from "@/lib/graph";

export function GraphExplorer({
  model,
  initialSearch = "",
  history,
}: {
  model: GraphDataset;
  initialSearch?: string;
  history?: GraphHistory;
}) {
  const viewHistory = useMemo(() => history ?? browserGraphHistory(), [history]);
  const [search, setSearch] = useState(initialSearch);
  const knownIds = useMemo(() => model.nodes.map((node) => node.id), [model.nodes]);
  const graph: GraphModel = useMemo(
    () => ({
      nodes: model.nodes.map((node) => ({ id: node.id, title: node.title })),
      edges: model.edges,
    }),
    [model.edges, model.nodes],
  );
  const byId = useMemo(() => new Map(model.nodes.map((node) => [node.id, node])), [model.nodes]);
  const location = parseGraphSearch(search, knownIds, model.defaultFocusId);
  const neighborhood = selectNeighborhood(graph, location.focus, location.hops);
  const blocks = partitionIncident(location.focus, model.edges, model.labels);
  const adjacency = exportAdjacency(neighborhood);
  const focus = byId.get(location.focus);
  const detail = location.detail ? byId.get(location.detail) : undefined;

  useEffect(() => {
    const read = () => setSearch(viewHistory.read());
    read();
    return viewHistory.subscribe(read);
  }, [viewHistory]);

  function commit(next: GraphLocation) {
    const query = serializeGraphSearch(next);
    viewHistory.push(query);
    setSearch(query ? `?${query}` : "");
  }

  return (
    <div className="mx-auto max-w-7xl space-y-8 px-4 py-10 sm:px-6">
      <header>
        <p className="kicker mb-2">{model.dataspaceTitle}</p>
        <h1 className="text-3xl font-semibold tracking-tight">Graph</h1>
        <p className="mt-3 text-sm text-muted">Focus: <span data-focus={location.focus}>{focus?.title ?? location.focus}</span></p>
      </header>
      <div className="flex flex-wrap gap-2">
        <button type="button" aria-pressed={location.hops === 1} onClick={() => commit({ ...location, hops: 1 })}>1 hop</button>
        <button type="button" aria-pressed={location.hops === 2} onClick={() => commit({ ...location, hops: 2 })}>2 hops</button>
      </div>
      <p data-excluded-count={neighborhood.excludedCount}>
        {neighborhood.excludedCount} relations outside this neighborhood
      </p>
      <section aria-label="Neighborhood">
        <h2 className="mb-3 text-lg">Neighborhood</h2>
        <ul className="space-y-2 text-sm">
          {neighborhood.nodeIds.map((id) => {
            const node = byId.get(id);
            return (
              <li key={id} data-neighborhood={id}>
                <button
                  type="button"
                  className="mr-2 underline"
                  data-focus-node={id}
                  aria-current={id === location.focus ? "true" : undefined}
                  onClick={() => commit({ ...location, focus: id })}
                >
                  {node?.title ?? id}
                </button>
                <button type="button" data-open-detail={id} onClick={() => commit({ ...location, detail: id })}>
                  Open
                </button>
              </li>
            );
          })}
        </ul>
      </section>
      <section aria-label="Records">
        <h2 className="mb-3 text-lg">Records</h2>
        <ul className="flex flex-wrap gap-2 text-sm">
          {model.nodes.map((node) => (
            <li key={node.id}>
              <button type="button" className="underline" data-address={node.id} onClick={() => commit({ ...location, focus: node.id })}>
                {node.title}
              </button>
            </li>
          ))}
        </ul>
      </section>
      <section aria-label="Outgoing">
        <h2 className="mb-3 text-lg">Outgoing</h2>
        {blocks.outgoing.length === 0 ? <p className="text-sm text-muted">No outgoing relations.</p> : (
          <ul className="space-y-1 text-sm">
            {blocks.outgoing.map((relation) => (
              <li key={relation.id} data-relation={relation.id}>{relation.wording}</li>
            ))}
          </ul>
        )}
      </section>
      <section aria-label="Incoming">
        <h2 className="mb-3 text-lg">Incoming</h2>
        {blocks.incoming.length === 0 ? <p className="text-sm text-muted">No incoming relations.</p> : (
          <ul className="space-y-1 text-sm">
            {blocks.incoming.map((relation) => (
              <li key={relation.id} data-relation={relation.id}>{relation.wording}</li>
            ))}
          </ul>
        )}
      </section>
      {blocks.remainder > 0 ? (
        <p>{blocks.remainder} more relations are not listed.</p>
      ) : null}
      {detail ? (
        <article aria-label="Opened detail" data-detail={detail.id}>
          <h2 className="text-lg">{detail.title}</h2>
          <p>{detail.summary}</p>
          <a className="underline" href={detail.href}>Open record</a>
          <button type="button" onClick={() => commit({ ...location, detail: null })}>Close detail</button>
        </article>
      ) : null}
      <section aria-label="Adjacency">
        <h2 className="mb-3 text-lg">Adjacency</h2>
        <pre data-adjacency>{JSON.stringify(adjacency)}</pre>
      </section>
    </div>
  );
}