import { Tx } from '@cmdcode/tapscript';
import { readEnvelope } from './inscription.js';

// Rebuild solely from serialized transactions, never collectible/UI sidecars.
// Discovery is a convention, not native ord metaprotocol tag 7 support.
export class MetadataIndex {
  constructor(chain) {
    this.events = [];
    const visit = (raw, height, block) => {
      const tx = Tx.decode(raw);
      if (tx.vin[0]?.witness?.length !== 3) return;
      const item = readEnvelope(tx.vin[0].witness);
      const metadata = item.metadata;
      this.events.push({ id: `${Tx.util.getTxid(tx)}i0`, contentType: item.contentType,
        status: height === null ? 'pending' : 'confirmed', height, block,
        metadata: metadata ?? null, hasMetadata: metadata !== undefined, parent: item.parent,
        protocol: metadata && !Array.isArray(metadata) && typeof metadata === 'object' &&
          Object.hasOwn(metadata, 'protocol') && typeof metadata.protocol === 'string' ? metadata.protocol : null });
    };
    for (const block of chain.blocks) for (const raw of block.raws) visit(raw, block.height, block.hash);
    for (const raw of chain.mempool) visit(raw, null, null);
  }
  forProtocol(name) { return this.events.filter(e => e.protocol === name); }
  get protocols() { return [...new Set(this.events.filter(e => e.protocol !== null).map(e => e.protocol))].sort(); }
  get stats() { return { events: this.events.length, withMetadata: this.events.filter(e => e.hasMetadata).length,
    confirmed: this.events.filter(e => e.status === 'confirmed').length,
    pending: this.events.filter(e => e.status === 'pending').length, protocols: this.protocols }; }
}

// Trusted, application-bundled reducers only. Adding a plugin requires a code change/review.
// No eval, dynamic imports, inscription scripts, or interpretation in MetadataIndex.
const reducers = Object.freeze({
  'event-counter': events => events.reduce((state, event) => ({
    count: state.count + 1, confirmed: state.confirmed + Number(event.status === 'confirmed'),
    pending: state.pending + Number(event.status === 'pending'), ids: [...state.ids, event.id],
  }), { count: 0, confirmed: 0, pending: 0, ids: [] }),
});
export function deriveProtocol(index, protocol, reducerName) {
  if (!Object.hasOwn(reducers, reducerName)) throw new Error('Unknown trusted local reducer.');
  return reducers[reducerName](structuredClone(index.forProtocol(protocol)));
}