import {ForkSeq} from "@lodestar/params";
import {
  getIntersectingIndices,
  isSlashableAttestationData,
  toIndexedAttestationBigint,
} from "@lodestar/state-transition";
import {AttesterSlashing, IndexedAttestation} from "@lodestar/types";

/**
 * Find all slashable pairs within a list of IndexedAttestations and
 * construct AttesterSlashing objects for each.
 */
export function getAttesterSlashingsFromIndexedAttestations(
  fork: ForkSeq,
  indexedAttestations: IndexedAttestation[]
): AttesterSlashing[] {
  const slashings: AttesterSlashing[] = [];

  for (let i = 0; i < indexedAttestations.length; i++) {
    for (let j = i + 1; j < indexedAttestations.length; j++) {
      // Order by source epoch so the surrounding attestation is always first,
      // matching what isSlashableAttestationData expects (one-directional check).
      const [first, second] =
        indexedAttestations[j].data.source.epoch < indexedAttestations[i].data.source.epoch
          ? [indexedAttestations[j], indexedAttestations[i]]
          : [indexedAttestations[i], indexedAttestations[j]];

      if (getIntersectingIndices(first.attestingIndices, second.attestingIndices).length === 0) continue;

      const firstBigint = toIndexedAttestationBigint(first, fork);
      const secondBigint = toIndexedAttestationBigint(second, fork);

      if (!isSlashableAttestationData(firstBigint.data, secondBigint.data)) continue;

      slashings.push({
        attestation1: firstBigint,
        attestation2: secondBigint,
      });
    }
  }

  return slashings;
}