/**
 * Region backfill — admin tooling
 * ─────────────────────────────────────────────────────────────────────────────
 * Spots and shops created before reverse geocoding landed (2026-10-01) have a
 * geohash/coordinates but no `city` / `country` tag. On the map they render
 * normally; in `/stats` they can only ever be "Uncategorised". The community
 * stats therefore under-count a country relative to the map's pins.
 *
 * This hook finds the LOGGED-IN user's own untagged spots/shops, re-derives the
 * region tags from each pin's coordinates (the same `reverseGeocodeRegions()`
 * that create/edit use) and republishes the addressable event with those tags
 * added. It only ever touches the current user's content — an addressable event
 * can only be replaced by its author's key.
 *
 * Faithful to the original event: every existing tag is preserved; only an
 * out-of-date `city`/`country`/`country_code` is replaced.
 */

import { useCallback, useMemo, useState } from 'react';
import { useQuery, useQueryClient } from '@tanstack/react-query';
import { useNostr } from '@nostrify/react';
import ngeohash from 'ngeohash';
import type { NostrEvent } from '@nostrify/nostrify';

import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useSkateRelays } from '@/hooks/useSkateRelays';
import { SKATE_SPOT_KIND, SKATE_SHOP_KIND } from '@/lib/types';
import { reverseGeocodeRegions } from '@/lib/geocodeRegions';

/** Nominatim's usage policy allows at most one request per second. */
const GEOCODE_SPACING_MS = 1100;
const REGION_TAG_NAMES = new Set(['city', 'country', 'country_code']);

export interface BackfillCandidate {
  id: string;
  kind: number;
  identifier: string;
  title: string;
}

export interface BackfillResult {
  updated: number;
  skipped: number;
  failed: number;
}

/** Same definition the stats use to decide a location is "tagged". */
function hasRegionTag(event: NostrEvent): boolean {
  return event.tags.some(
    ([name, value]) => (name === 'city' || name === 'country') && !!value?.trim(),
  );
}

/** Coordinates from explicit lat/lon tags, else decoded from the geohash. */
function coordsOf(event: NostrEvent): { lat: number; lng: number } | null {
  const latTag = event.tags.find(([name]) => name === 'lat')?.[1];
  const lonTag = event.tags.find(([name]) => name === 'lon')?.[1];
  if (latTag && lonTag) {
    const lat = parseFloat(latTag);
    const lng = parseFloat(lonTag);
    if (
      Number.isFinite(lat) && Number.isFinite(lng) &&
      lat >= -90 && lat <= 90 && lng >= -180 && lng <= 180
    ) {
      return { lat, lng };
    }
  }

  const geohash = event.tags.find(([name]) => name === 'g')?.[1];
  if (geohash) {
    try {
      const { latitude, longitude } = ngeohash.decode(geohash);
      if (Number.isFinite(latitude) && Number.isFinite(longitude)) {
        return { lat: latitude, lng: longitude };
      }
    } catch {
      /* not a decodable geohash */
    }
  }
  return null;
}

export function useRegionBackfill(enabled = true) {
  const { user } = useCurrentUser();
  const { nostr } = useNostr();
  const { querySkateContent, getWriteRelays } = useSkateRelays();
  const queryClient = useQueryClient();
  const [progress, setProgress] = useState<{ done: number; total: number } | null>(null);

  const eventsQuery = useQuery({
    queryKey: ['region-backfill', user?.pubkey ?? 'anon'],
    enabled: enabled && !!user,
    staleTime: 0,
    queryFn: async () => {
      if (!user) return [];
      const signal = AbortSignal.timeout(15000);
      return querySkateContent(
        [{ kinds: [SKATE_SPOT_KIND, SKATE_SHOP_KIND], authors: [user.pubkey], limit: 500 }],
        { signal },
      );
    },
  });

  const candidates = useMemo<BackfillCandidate[]>(
    () =>
      (eventsQuery.data ?? [])
        .filter((event) => !hasRegionTag(event))
        .map((event) => ({
          id: event.id,
          kind: event.kind,
          identifier: event.tags.find(([name]) => name === 'd')?.[1] ?? '',
          title: event.tags.find(([name]) => name === 'title')?.[1] ?? '(untitled)',
        })),
    [eventsQuery.data],
  );

  const backfill = useCallback(async (): Promise<BackfillResult> => {
    if (!user) throw new Error('Log in first.');
    const events = (eventsQuery.data ?? []).filter((event) => !hasRegionTag(event));
    const relays = getWriteRelays();
    const result: BackfillResult = { updated: 0, skipped: 0, failed: 0 };
    setProgress({ done: 0, total: events.length });

    for (let i = 0; i < events.length; i += 1) {
      const event = events[i];
      try {
        const coords = coordsOf(event);
        if (!coords) {
          result.skipped += 1;
          continue;
        }
        const geo = await reverseGeocodeRegions(coords.lat, coords.lng);
        if (!geo.city && !geo.country && !geo.countryCode) {
          result.skipped += 1;
          continue;
        }

        // Preserve every existing tag; only refresh the region tags.
        const tags = event.tags.filter(([name]) => !REGION_TAG_NAMES.has(name));
        if (geo.city) tags.push(['city', geo.city]);
        if (geo.country) tags.push(['country', geo.country]);
        if (geo.countryCode) tags.push(['country_code', geo.countryCode]);

        const signed = await user.signer.signEvent({
          kind: event.kind,
          content: event.content,
          created_at: Math.floor(Date.now() / 1000),
          tags,
        });

        // Publish where the stats READ (community relay + the author's relays).
        const published = await Promise.allSettled(
          relays.map((url) =>
            nostr.relay(url).event(signed, { signal: AbortSignal.timeout(8000) }),
          ),
        );
        if (published.some((r) => r.status === 'fulfilled')) result.updated += 1;
        else result.failed += 1;
      } catch {
        result.failed += 1;
      } finally {
        setProgress({ done: i + 1, total: events.length });
      }

      // Respect Nominatim's 1 req/s limit (no need to wait after the last one).
      if (i < events.length - 1) {
        await new Promise((resolve) => setTimeout(resolve, GEOCODE_SPACING_MS));
      }
    }

    setProgress(null);
    queryClient.invalidateQueries({ queryKey: ['skate-spots'] });
    queryClient.invalidateQueries({ queryKey: ['growth-stats'] });
    queryClient.invalidateQueries({ queryKey: ['region-backfill'] });
    return result;
  }, [user, eventsQuery.data, nostr, getWriteRelays, queryClient]);

  return {
    candidates,
    isLoading: eventsQuery.isLoading,
    backfill,
    progress,
    isRunning: progress !== null,
  };
}