SkateSpots/src/hooks/useTradeAttestations.ts

import { useQuery } from '@tanstack/react-query';
import { useNostr } from '@nostrify/react';
import type { NostrEvent } from '@nostrify/nostrify';
import { useNostrPublish } from '@/hooks/useNostrPublish';
import { useCurrentUser } from '@/hooks/useCurrentUser';
import { MARKETPLACE_ITEM_KIND } from '@/lib/types';

/**
 * Trade attestations (completed deals) — built on the Attestations NIP
 * (kind 31871), see NIP.md → "Trade Attestations".
 *
 * A **listing** (kind 30402) is the *Assertion Event*. When a deal closes:
 *   • the seller publishes a `31871` attesting it (`s=valid`) and naming the
 *     buyer in a `p` tag (our documented extension);
 *   • the buyer may publish a mirror `31871` naming the seller.
 * Two reciprocal attestations on the same listing = a **verified trade**.
 *
 * Payment method is self-reported metadata; the app cannot observe cash/trade
 * deals and never treats these as proof of payment.
 */
export const TRADE_ATTESTATION_KIND = 31871;

/**
 * Attestation Request (kind 31872) — the request side of the flow. A buyer
 * whose deal wasn't recorded by the seller can ask them to publish a `31871`;
 * the seller's client surfaces it and fulfils it in one tap.
 * See NIP.md → "Trade Attestations".
 */
export const TRADE_REQUEST_KIND = 31872;

export const TRADE_METHODS = {
  cash: 'Cash',
  lightning: 'Lightning',
  trade: 'Trade',
  other: 'Other',
} as const;

export type TradeMethod = keyof typeof TRADE_METHODS;
export type TradeRole = 'sold' | 'bought';

export interface ListingCoord {
  kind: number;
  pubkey: string;
  identifier: string;
}

/** Parse an `a` tag ("30402:<pubkey>:<d>") into its parts, or null. */
export function parseListingCoord(aTag: string | undefined): ListingCoord | null {
  if (!aTag) return null;
  const [kindStr, pubkey, ...rest] = aTag.split(':');
  const kind = Number(kindStr);
  if (!Number.isFinite(kind) || !pubkey || rest.length === 0) return null;
  return { kind, pubkey, identifier: rest.join(':') };
}

/**
 * Is this kind-31871 event a *trade* attestation? We require a 30402 assertion
 * (`a` tag) plus a counterparty (`p`) — our documented marker for trades.
 */
export function isTradeAttestation(ev: NostrEvent): boolean {
  if (ev.kind !== TRADE_ATTESTATION_KIND) return false;
  const a = ev.tags.find(([t]) => t === 'a')?.[1];
  const coord = parseListingCoord(a);
  if (!coord || coord.kind !== MARKETPLACE_ITEM_KIND) return false;
  return ev.tags.some(([t]) => t === 'p');
}

/**
 * Is this kind-31872 event a *trade* request? Same marker as attestations: a
 * 30402 assertion (`a`) plus a requested attestor (`p`).
 */
export function isTradeRequest(ev: NostrEvent): boolean {
  if (ev.kind !== TRADE_REQUEST_KIND) return false;
  const coord = parseListingCoord(ev.tags.find(([t]) => t === 'a')?.[1]);
  if (!coord || coord.kind !== MARKETPLACE_ITEM_KIND) return false;
  return ev.tags.some(([t]) => t === 'p');
}

/**
 * Publish a trade attestation (kind 31871, addressable).
 *
 * `d` is derived from the listing + role so re-publishing the same attestation
 * replaces it (e.g. to set `s=revoked`), per the NIP's lifecycle.
 */
export function useTradeAttestation() {
  const { user } = useCurrentUser();
  const { mutateAsync: publish, isPending } = useNostrPublish();

  const publishTrade = async ({
    listing,
    role,
    counterparty,
    method,
    amountSats,
    state = 'valid',
    note,
    requestCoord,
  }: {
    /** The listing being attested. */
    listing: { pubkey: string; identifier: string };
    role: TradeRole;
    /** The other party's pubkey. */
    counterparty: string;
    method?: TradeMethod;
    amountSats?: number;
    state?: 'verifying' | 'valid' | 'revoked';
    note?: string;
    /** The `31872` request coord this attestation fulfils, if any (spec `request` tag). */
    requestCoord?: string;
  }) => {
    if (!user) throw new Error('You must be logged in.');
    if (counterparty === user.pubkey) throw new Error('Pick the other party, not yourself.');

    const coord = `${MARKETPLACE_ITEM_KIND}:${listing.pubkey}:${listing.identifier}`;

    const tags: string[][] = [
      ['d', `${user.pubkey}:trade:${role}:${listing.identifier}`],
      ['a', coord],
      ['s', state],
      ['p', counterparty],
      ['alt', role === 'sold' ? 'SkateSpots: sale completed' : 'SkateSpots: purchase confirmed'],
    ];
    if (method) tags.push(['method', method]);
    if (typeof amountSats === 'number' && amountSats > 0) {
      tags.push(['amount', String(Math.round(amountSats)), 'SATS']);
    }
    if (requestCoord) tags.push(['request', requestCoord]);

    const name = user.pubkey.slice(0, 8);
    const content =
      note?.trim() ||
      (role === 'sold' ? `Sold by ${name}.` : `Bought from ${name}.`);

    await publish({ kind: TRADE_ATTESTATION_KIND, content, tags });
  };

  return { publishTrade, isPending };
}

export interface TradeReputation {
  /** Listings this pubkey sold (they attested as the listing author). */
  sales: number;
  /** Listings they attested as the non-owner party. */
  purchases: number;
  /** Deals where both sides attested the same listing. */
  verified: number;
  /** Per-counterparty count of mutually-confirmed trades (for WoT weighting). */
  verifiedWith: { pubkey: string; count: number }[];
  /** Distinct counterparties involved. */
  counterparties: string[];
  /** Raw trade attestations this pubkey is involved in. */
  attestations: NostrEvent[];
}

/**
 * Trade reputation for a pubkey: seller/buyer positions derived from kind-31871
 * attestations, plus a "verified" count where seller and counterparty both
 * attested the same listing (the strong, mutually-confirmed signal).
 *
 * NOTE: consumers should trust-weight counterparties with the existing WoT
 * score so rings of fresh accounts can't inflate reputation.
 */
export function useTradeReputation(pubkey: string | undefined) {
  const { nostr } = useNostr();

  return useQuery<TradeReputation>({
    queryKey: ['trade-reputation', pubkey],
    enabled: !!pubkey,
    staleTime: 5 * 60 * 1000,
    queryFn: async (c): Promise<TradeReputation> => {
      const empty: TradeReputation = { sales: 0, purchases: 0, verified: 0, verifiedWith: [], counterparties: [], attestations: [] };
      if (!pubkey) return empty;

      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(12000)]);
      const events = await nostr.query(
        [
          { kinds: [TRADE_ATTESTATION_KIND], authors: [pubkey], limit: 200 },
          { kinds: [TRADE_ATTESTATION_KIND], '#p': [pubkey], limit: 200 },
        ],
        { signal },
      );

      const unique = Array.from(new Map(events.map((e) => [e.id, e])).values()).filter(
        (e) => isTradeAttestation(e) && e.tags.find(([t]) => t === 's')?.[1] !== 'revoked',
      );

      // Group by the attested listing coordinate.
      const byListing = new Map<string, NostrEvent[]>();
      for (const ev of unique) {
        const coord = parseListingCoord(ev.tags.find(([t]) => t === 'a')?.[1]);
        if (!coord) continue;
        const key = `${coord.kind}:${coord.pubkey}:${coord.identifier}`;
        const list = byListing.get(key) ?? [];
        list.push(ev);
        byListing.set(key, list);
      }

      const counterparties = new Set<string>();
      const verifiedWith = new Map<string, number>();
      let sales = 0;
      let purchases = 0;
      let verified = 0;

      for (const [key, attestations] of byListing) {
        const coord = parseListingCoord(key);
        if (!coord) continue;
        const seller = coord.pubkey;
        const attestors = new Set(attestations.map((e) => e.pubkey));
        const isVerified = attestors.has(seller) && attestors.size >= 2;
        const involved = attestors.has(pubkey);

        if (involved) {
          if (pubkey === seller) sales++;
          else purchases++;
          if (isVerified) {
            verified++;
            // Attribute the verified trade to the other attestor(s).
            for (const a of attestors) {
              if (a !== pubkey) verifiedWith.set(a, (verifiedWith.get(a) ?? 0) + 1);
            }
          }

          // Record counterparties (everyone else who attested this listing).
          for (const a of attestors) if (a !== pubkey) counterparties.add(a);
          for (const ev of attestations) {
            for (const [, value] of ev.tags.filter(([t]) => t === 'p')) {
              if (value !== pubkey) counterparties.add(value);
            }
          }
        }
      }

      return {
        sales,
        purchases,
        verified,
        verifiedWith: [...verifiedWith.entries()].map(([pubkey, count]) => ({ pubkey, count })),
        counterparties: [...counterparties],
        attestations: unique,
      };
    },
  });
}

/**
 * Trades where someone named the viewer as counterparty and the viewer has NOT
 * yet published their own attestation — used to prompt "confirm this trade".
 */
export function usePendingTradeConfirmations(viewerPubkey: string | undefined) {
  const { nostr } = useNostr();

  return useQuery({
    queryKey: ['pending-trade-confirmations', viewerPubkey],
    enabled: !!viewerPubkey,
    staleTime: 60 * 1000,
    queryFn: async (c) => {
      type Pending = { coord: string; listing: { pubkey: string; identifier: string }; seller: string };
      if (!viewerPubkey) return [] as Pending[];

      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(10000)]);
      const [naming, mine] = await Promise.all([
        nostr.query([{ kinds: [TRADE_ATTESTATION_KIND], '#p': [viewerPubkey], limit: 200 }], { signal }),
        nostr.query([{ kinds: [TRADE_ATTESTATION_KIND], authors: [viewerPubkey], limit: 200 }], { signal }),
      ]);

      const myCoords = new Set(
        mine.filter(isTradeAttestation).map((e) => e.tags.find(([t]) => t === 'a')?.[1]).filter(Boolean),
      );

      const pending: Pending[] = [];
      const seen = new Set<string>();
      for (const ev of naming.filter(isTradeAttestation)) {
        if (ev.pubkey === viewerPubkey) continue;
        const coord = ev.tags.find(([t]) => t === 'a')?.[1];
        const parsed = parseListingCoord(coord);
        // The attestor must be the listing author (i.e. the seller's record).
        if (!coord || !parsed || parsed.pubkey !== ev.pubkey) continue;
        if (myCoords.has(coord) || seen.has(coord)) continue;
        seen.add(coord);
        pending.push({
          coord,
          listing: { pubkey: parsed.pubkey, identifier: parsed.identifier },
          seller: ev.pubkey,
        });
      }
      return pending;
    },
  });
}

/**
 * Trade attestations for one listing, from the viewer's perspective:
 * `iConfirmed` (they attested it) and `counterparty` (who else has).
 */
export function useListingTrade(
  listing: { pubkey: string; identifier: string } | undefined,
  viewerPubkey: string | undefined,
) {
  const { nostr } = useNostr();
  const coord = listing ? `${MARKETPLACE_ITEM_KIND}:${listing.pubkey}:${listing.identifier}` : undefined;

  return useQuery({
    queryKey: ['listing-trade', coord, viewerPubkey],
    enabled: !!coord,
    staleTime: 60 * 1000,
    queryFn: async (c) => {
      if (!coord) return { attestations: [] as NostrEvent[], iConfirmed: false, counterparties: [] as string[] };
      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(10000)]);
      const events = await nostr.query(
        [{ kinds: [TRADE_ATTESTATION_KIND], '#a': [coord], limit: 50 }],
        { signal },
      );
      const attestations = events.filter(
        (e) => isTradeAttestation(e) && e.tags.find(([t]) => t === 's')?.[1] !== 'revoked',
      );
      const authorSet = new Set(attestations.map((e) => e.pubkey));
      const counterparties = new Set<string>();
      for (const ev of attestations) {
        for (const [, value] of ev.tags.filter(([t]) => t === 'p')) {
          if (value !== viewerPubkey) counterparties.add(value);
        }
      }
      for (const a of authorSet) if (a !== viewerPubkey) counterparties.add(a);
      return {
        attestations,
        iConfirmed: !!viewerPubkey && authorSet.has(viewerPubkey),
        counterparties: [...counterparties],
      };
    },
  });
}

/**
 * Publish a trade confirmation request (kind 31872, addressable).
 *
 * A buyer who completed a deal the seller hasn't recorded asks the seller (the
 * listing author) to publish a `31871`. `d` is derived from the listing + the
 * viewer, so re-requesting replaces the previous request.
 */
export function useTradeAttestationRequest() {
  const { user } = useCurrentUser();
  const { mutateAsync: publish, isPending } = useNostrPublish();

  const publishRequest = async ({
    listing,
    attestor,
    note,
    cashuToken,
  }: {
    /** The listing the deal was for. */
    listing: { pubkey: string; identifier: string };
    /** The party asked to attest — normally the seller (listing author). */
    attestor: string;
    note?: string;
    /**
     * Optional escrowed Cashu token (spec `cashu_token`). Only relevant when
     * you created and locked one yourself; a plain token is not escrow.
     */
    cashuToken?: string;
  }) => {
    if (!user) throw new Error('You must be logged in.');
    if (attestor === user.pubkey) throw new Error('Pick the other party, not yourself.');

    const coord = `${MARKETPLACE_ITEM_KIND}:${listing.pubkey}:${listing.identifier}`;
    const tags: string[][] = [
      ['d', `${user.pubkey}:trade-request:${listing.identifier}`],
      ['a', coord],
      ['p', attestor],
      ['alt', 'SkateSpots: trade confirmation requested'],
    ];
    if (cashuToken?.trim()) tags.push(['cashu_token', cashuToken.trim()]);

    await publish({
      kind: TRADE_REQUEST_KIND,
      content: note?.trim() || 'Please confirm our trade so it counts for reputation.',
      tags,
    });
  };

  return { publishRequest, isPending };
}

export interface IncomingTradeRequest {
  coord: string;
  listing: { pubkey: string; identifier: string };
  requestor: string;
  note: string;
  event: NostrEvent;
}

/**
 * Requests naming the viewer as the attestor (i.e. they are the seller) that
 * they have not yet fulfilled. Drives the "confirm this sale" prompt.
 */
export function useIncomingTradeRequests(viewerPubkey: string | undefined) {
  const { nostr } = useNostr();

  return useQuery<IncomingTradeRequest[]>({
    queryKey: ['incoming-trade-requests', viewerPubkey],
    enabled: !!viewerPubkey,
    staleTime: 60 * 1000,
    queryFn: async (c) => {
      if (!viewerPubkey) return [];

      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(10000)]);
      const [requests, mine] = await Promise.all([
        nostr.query([{ kinds: [TRADE_REQUEST_KIND], '#p': [viewerPubkey], limit: 200 }], { signal }),
        nostr.query([{ kinds: [TRADE_ATTESTATION_KIND], authors: [viewerPubkey], limit: 200 }], { signal }),
      ]);

      // Requests the viewer already fulfilled (they attested that listing).
      const fulfilled = new Set(
        mine.filter(isTradeAttestation).map((e) => e.tags.find(([t]) => t === 'a')?.[1]).filter(Boolean),
      );

      const out: IncomingTradeRequest[] = [];
      const seen = new Set<string>();
      for (const ev of requests.filter(isTradeRequest)) {
        if (ev.pubkey === viewerPubkey) continue;
        const coord = ev.tags.find(([t]) => t === 'a')?.[1];
        const parsed = parseListingCoord(coord);
        // Only the listing author (seller) can attest the sale.
        if (!coord || !parsed || parsed.pubkey !== viewerPubkey) continue;
        if (fulfilled.has(coord) || seen.has(coord)) continue;
        seen.add(coord);
        out.push({
          coord,
          listing: { pubkey: parsed.pubkey, identifier: parsed.identifier },
          requestor: ev.pubkey,
          note: ev.content,
          event: ev,
        });
      }
      return out;
    },
  });
}

/**
 * I added a new trade request for a listing. Replaces any previous one (same `d`).
 *
 * For a plain token this is just "a token you happen to include". Real escrow
 * needs the token locked to spending conditions (P2PK/HTLC) plus a release
 * witness — see NIP.md → Trade Attestations → Escrow (not yet implemented).
 */
export function useListingTradeRequest(
  listing: { pubkey: string; identifier: string } | undefined,
  viewerPubkey: string | undefined,
) {
  const { nostr } = useNostr();
  const coord = listing ? `${MARKETPLACE_ITEM_KIND}:${listing.pubkey}:${listing.identifier}` : undefined;

  return useQuery({
    queryKey: ['listing-trade-request', coord, viewerPubkey],
    enabled: !!coord,
    staleTime: 60 * 1000,
    queryFn: async (c) => {
      if (!coord) return { requests: [] as NostrEvent[], iRequested: false };
      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(10000)]);
      const events = (
        await nostr.query([{ kinds: [TRADE_REQUEST_KIND], '#a': [coord], limit: 50 }], { signal })
      ).filter(isTradeRequest);
      return {
        requests: events,
        iRequested: !!viewerPubkey && events.some((e) => e.pubkey === viewerPubkey),
      };
    },
  });
}