"use client";

import { useMemo } from "react";
import { useQueries, useQuery } from "@tanstack/react-query";
import type { DisplaySummary } from "../lib/transcripts";
import type { Manifest } from "../lib/manifest";
import { readerFor } from "../lib/archive/readers";

export type SummariesState = {
  manifest: Manifest | null;
  summaries: DisplaySummary[];
  loadedPages: number;
  pageCount: number;
  summariesReady: boolean;
  error: Error | null;
};

export function useManifest(origin = "") {
  return useQuery<Manifest>({
    queryKey: ["manifest", origin],
    queryFn: () => readerFor(origin).readSummariesManifest(),
  });
}

export function useSummaries(origin = ""): SummariesState {
  const manifestQuery = useManifest(origin);
  const manifest = manifestQuery.data ?? null;
  const pageCount = manifest?.pageCount ?? 0;

  const pageQueries = useQueries({
    queries: Array.from({ length: pageCount }, (_, i) => ({
      queryKey: ["summaries-page", origin, i],
      queryFn: () => readerFor(origin).readSummariesPage(i),
      enabled: pageCount > 0,
    })),
  });

  const loadedPages = pageQueries.filter((q) => q.data).length;
  const summariesReady = pageCount > 0 && loadedPages === pageCount;

  // Concatenate available pages; sort once all pages are in. Pages may arrive
  // out of order, so a late sort keeps the newest-first ordering stable
  // regardless of arrival order. Matches the LMDB composite-key order
  // [uploadDate, channelSlug, id] reversed.
  const summaries = useMemo<DisplaySummary[]>(() => {
    if (loadedPages === 0) return [];
    const out: DisplaySummary[] = [];
    for (const q of pageQueries) if (q.data) out.push(...q.data);
    if (summariesReady) {
      out.sort(
        (a, b) =>
          b.uploadDate.localeCompare(a.uploadDate) ||
          a.channelSlug.localeCompare(b.channelSlug) ||
          a.id.localeCompare(b.id),
      );
    }
    return out;
    // pageQueries identity changes every render; key off loadedPages + ready.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [loadedPages, summariesReady]);

  const error =
    manifestQuery.error instanceof Error
      ? manifestQuery.error
      : (pageQueries.find((q) => q.error)?.error as Error | undefined) ?? null;

  return {
    manifest,
    summaries,
    loadedPages,
    pageCount,
    summariesReady,
    error,
  };
}