import { useMemo } from 'react';
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
import { useNostr } from '@nostrify/react';
import type { NostrEvent } from '@nostrify/nostrify';
import {
  SPOT_STATUS_KIND,
  SKATE_SPOT_KIND,
  parseSpotStatusReport,
  type SpotStatusReport,
  type SpotStatusValue,
} from '@/lib/types';
import { useBatchTrustScores } from '@/hooks/useBatchTrustScores';
import { useNostrPublish } from '@/hooks/useNostrPublish';
import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useSkateRelays } from '@/hooks/useSkateRelays';

/** Reports older than this are ignored entirely (spots do change back). */
const REPORT_MAX_AGE_SECONDS = 180 * 24 * 60 * 60; // 180 days

/** Half-life for recency weighting — a report loses half its weight every 30 days. */
const RECENCY_HALF_LIFE_SECONDS = 30 * 24 * 60 * 60;

export interface AggregatedSpotStatus {
  /** The winning (highest-weighted) status, or null if no reports. */
  status: SpotStatusValue | null;
  /** Confidence 0–1 = winning weight / total weight. */
  confidence: number;
  /** Number of distinct reporters contributing. */
  reporterCount: number;
  /** Timestamp of the most recent report used. */
  lastReportedAt: number | null;
  /** Per-status weighted tallies (for a breakdown UI if desired). */
  tallies: Record<SpotStatusValue, number>;
}

function spotRefFor(pubkey: string, identifier: string): string {
  return `${SKATE_SPOT_KIND}:${pubkey}:${identifier}`;
}

/**
 * Compute a recency weight in (0, 1]. A brand-new report = 1; a report one
 * half-life old = 0.5; and so on. This makes fresh reports dominate stale ones,
 * so a spot that was "gone" but got rebuilt naturally recovers over time.
 */
function recencyWeight(createdAt: number, now: number): number {
  const age = Math.max(0, now - createdAt);
  return Math.pow(0.5, age / RECENCY_HALF_LIFE_SECONDS);
}

/**
 * Aggregate a list of reports into a single consensus status.
 *
 * Each report contributes `recencyWeight × trustWeight`. Trust weight comes from
 * the reporter's trust score (0–100) mapped to a floor of 0.2 so that even
 * untrusted users have *some* voice, but followed/verified users dominate.
 * Only the most recent report from each reporter counts (people change their
 * minds; we don't let one person stuff the ballot).
 */
function aggregate(
  reports: SpotStatusReport[],
  trustScores: Map<string, number> | undefined,
  now: number,
): AggregatedSpotStatus {
  const empty: AggregatedSpotStatus = {
    status: null,
    confidence: 0,
    reporterCount: 0,
    lastReportedAt: null,
    tallies: { active: 0, bust: 0, skate_stopped: 0, closed: 0, gone: 0 },
  };

  if (reports.length === 0) return empty;

  // Keep only the most recent report per reporter, within the max age window.
  const latestByReporter = new Map<string, SpotStatusReport>();
  for (const r of reports) {
    if (now - r.createdAt > REPORT_MAX_AGE_SECONDS) continue;
    const existing = latestByReporter.get(r.pubkey);
    if (!existing || r.createdAt > existing.createdAt) {
      latestByReporter.set(r.pubkey, r);
    }
  }

  if (latestByReporter.size === 0) return empty;

  const tallies: Record<SpotStatusValue, number> = {
    active: 0,
    bust: 0,
    skate_stopped: 0,
    closed: 0,
    gone: 0,
  };

  let totalWeight = 0;
  let lastReportedAt = 0;

  for (const r of latestByReporter.values()) {
    const trust = trustScores?.get(r.pubkey) ?? 0;
    // Map trust 0–100 → 0.2–1.0 so everyone counts a little, trusted users more.
    const trustWeight = 0.2 + (Math.min(100, Math.max(0, trust)) / 100) * 0.8;
    const weight = recencyWeight(r.createdAt, now) * trustWeight;

    tallies[r.status] += weight;
    totalWeight += weight;
    if (r.createdAt > lastReportedAt) lastReportedAt = r.createdAt;
  }

  // Find the winning status.
  let winning: SpotStatusValue = 'active';
  let winningWeight = -1;
  (Object.keys(tallies) as SpotStatusValue[]).forEach((s) => {
    if (tallies[s] > winningWeight) {
      winningWeight = tallies[s];
      winning = s;
    }
  });

  return {
    status: winning,
    confidence: totalWeight > 0 ? winningWeight / totalWeight : 0,
    reporterCount: latestByReporter.size,
    lastReportedAt: lastReportedAt || null,
    tallies,
  };
}

/**
 * Fetch raw status reports for a SINGLE spot (used on the detail page).
 */
export function useSpotStatusReports(spotPubkey: string, spotIdentifier: string) {
  const { nostr } = useNostr();
  const spotRef = spotRefFor(spotPubkey, spotIdentifier);

  return useQuery({
    queryKey: ['spot-status-reports', spotRef],
    queryFn: async (c) => {
      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(5000)]);
      const events = await nostr.query(
        [{ kinds: [SPOT_STATUS_KIND], '#a': [spotRef], limit: 200 }],
        { signal },
      );
      return events
        .map(parseSpotStatusReport)
        .filter((r): r is SpotStatusReport => r !== null)
        .sort((a, b) => b.createdAt - a.createdAt);
    },
    enabled: !!spotPubkey && !!spotIdentifier,
    staleTime: 60_000,
  });
}

/**
 * Aggregated consensus status for a SINGLE spot, trust- and recency-weighted.
 */
export function useSpotStatus(spotPubkey: string, spotIdentifier: string) {
  const { data: reports, isLoading } = useSpotStatusReports(spotPubkey, spotIdentifier);

  const reporterPubkeys = useMemo(
    () => Array.from(new Set((reports ?? []).map((r) => r.pubkey))),
    [reports],
  );
  const { data: trustScores } = useBatchTrustScores(reporterPubkeys);

  const aggregated = useMemo(
    () => aggregate(reports ?? [], trustScores, Math.floor(Date.now() / 1000)),
    [reports, trustScores],
  );

  return { aggregated, reports: reports ?? [], isLoading };
}

/**
 * Batch: aggregated status for MANY spots at once (used on the map + cards).
 * Returns a Map keyed by spot coordinate (`30818:pubkey:dtag`).
 */
export function useBatchSpotStatus(spots: Array<{ pubkey: string; identifier: string }>) {
  const { querySkateContent, getQueryKeySuffix } = useSkateRelays();

  const spotRefs = useMemo(
    () => spots.map((s) => spotRefFor(s.pubkey, s.identifier)),
    [spots],
  );

  const reportsQuery = useQuery({
    queryKey: ['batch-spot-status', getQueryKeySuffix(), spotRefs.slice().sort().join(',')],
    queryFn: async (c) => {
      if (spotRefs.length === 0) return [] as NostrEvent[];
      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(8000)]);
      // Relays index single-letter tags, so '#a' with many refs is one query.
      const events = await querySkateContent(
        [{ kinds: [SPOT_STATUS_KIND], '#a': spotRefs, limit: 1000 }],
        { signal },
      );
      return events;
    },
    enabled: spotRefs.length > 0,
    staleTime: 60_000,
  });

  const reportsByRef = useMemo(() => {
    const map = new Map<string, SpotStatusReport[]>();
    for (const ev of reportsQuery.data ?? []) {
      const report = parseSpotStatusReport(ev);
      if (!report) continue;
      const list = map.get(report.spotRef) ?? [];
      list.push(report);
      map.set(report.spotRef, list);
    }
    return map;
  }, [reportsQuery.data]);

  const reporterPubkeys = useMemo(() => {
    const set = new Set<string>();
    for (const list of reportsByRef.values()) {
      for (const r of list) set.add(r.pubkey);
    }
    return Array.from(set);
  }, [reportsByRef]);

  const { data: trustScores } = useBatchTrustScores(reporterPubkeys);

  const statusByRef = useMemo(() => {
    const now = Math.floor(Date.now() / 1000);
    const map = new Map<string, AggregatedSpotStatus>();
    for (const [ref, list] of reportsByRef.entries()) {
      map.set(ref, aggregate(list, trustScores, now));
    }
    return map;
  }, [reportsByRef, trustScores]);

  return {
    statusByRef,
    isLoading: reportsQuery.isLoading,
    getStatus: (pubkey: string, identifier: string) =>
      statusByRef.get(spotRefFor(pubkey, identifier)) ?? null,
  };
}

/**
 * Publish a new status report for a spot.
 */
export function usePublishSpotStatus() {
  const { mutateAsync: publishEvent } = useNostrPublish();
  const { user } = useCurrentUser();
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: async (params: {
      spotPubkey: string;
      spotIdentifier: string;
      spotTitle: string;
      status: SpotStatusValue;
      note?: string;
    }) => {
      if (!user) throw new Error('You must be logged in to report a spot status.');

      const spotRef = spotRefFor(params.spotPubkey, params.spotIdentifier);

      await publishEvent({
        kind: SPOT_STATUS_KIND,
        content: (params.note ?? '').slice(0, 500),
        tags: [
          ['a', spotRef],
          ['K', String(SKATE_SPOT_KIND)],
          ['status', params.status],
          ['t', 'spot-status'],
          [
            'alt',
            `Spot status report: "${params.spotTitle}" is ${params.status.replace('_', '-')}`,
          ],
        ],
      });

      return { spotRef };
    },
    onSuccess: ({ spotRef }) => {
      queryClient.invalidateQueries({ queryKey: ['spot-status-reports', spotRef] });
      queryClient.invalidateQueries({ queryKey: ['batch-spot-status'] });
    },
  });
}