import { useState } from "react";

import type { TimelineSnapshot } from "./Timeline";
import type { Graph } from "./types";

export interface RunResults {
  f?: number;
  // By input name; only those worked out so far
  derivatives: Record<string, number>;
}

// What finished runs have found for this function at these input values, across modes and seeds
export default function useRunResults(graph: Graph | null, { run, state, flow, iteration, lastIteration }: TimelineSnapshot): RunResults {
  const [saved, setSaved] = useState<{ key: string | null; results: RunResults }>({ key: null, results: { derivatives: {} } });
  const key = graph && run ? JSON.stringify([graph, run.inputs]) : null;
  const results = saved.key === key ? saved.results : { derivatives: {} };

  // Set during render, so a finished run's results show with its last frame
  if (graph && run && state && !flow && iteration === lastIteration) {
    const found =
      run.mode === "forward"
        ? { [run.seed]: state.derivatives[graph.output] }
        : Object.fromEntries(graph.inputs.map((name, i) => [name, state.derivatives[graph.nodes[i].id]]));
    const f = state.values[graph.output];
    if (saved.key !== key || results.f !== f || Object.entries(found).some(([name, value]) => results.derivatives[name] !== value)) {
      setSaved({ key, results: { f, derivatives: { ...results.derivatives, ...found } } });
    }
  }
  return results;
}