import {BeaconConfig} from "@lodestar/config";
import {ForkSeq} from "@lodestar/params";
import {AttesterSlashing, Slot} from "@lodestar/types";
import {Index2PubkeyCache} from "../cache/pubkeyCache.js";
import {CachedBeaconStateAllForks} from "../types.js";
import {getAttesterSlashableIndices, isSlashableAttestationData, isSlashableValidator} from "../util/index.js";
import {isValidIndexedAttestationBigint} from "./isValidIndexedAttestation.js";
import {slashValidator} from "./slashValidator.js";

/**
 * Process an AttesterSlashing operation. Initiates the exit of a validator, decreases the balance of the slashed
 * validators and increases the block proposer balance.
 *
 * PERF: Work depends on number of AttesterSlashing per block. On regular networks the average is 0 / block.
 */
export function processAttesterSlashing(
  fork: ForkSeq,
  state: CachedBeaconStateAllForks,
  attesterSlashing: AttesterSlashing,
  verifySignatures = true
): void {
  const {epochCtx} = state;
  assertValidAttesterSlashing(
    state.config,
    epochCtx.index2pubkey,
    state.slot,
    state.validators.length,
    attesterSlashing,
    verifySignatures
  );

  const intersectingIndices = getAttesterSlashableIndices(attesterSlashing);

  let slashedAny = false;
  const validators = state.validators; // Get the validators sub tree once for all indices
  // Spec requires to sort indexes beforehand
  for (const index of intersectingIndices.sort((a, b) => a - b)) {
    if (isSlashableValidator(validators.getReadonly(index), epochCtx.epoch)) {
      slashValidator(fork, state, index);
      slashedAny = true;
    }
  }

  if (!slashedAny) {
    throw new Error("AttesterSlashing did not result in any slashings");
  }
}

export function assertValidAttesterSlashing(
  config: BeaconConfig,
  index2pubkey: Index2PubkeyCache,
  stateSlot: Slot,
  validatorsLen: number,
  attesterSlashing: AttesterSlashing,
  verifySignatures = true
): void {
  const attestation1 = attesterSlashing.attestation1;
  const attestation2 = attesterSlashing.attestation2;

  if (!isSlashableAttestationData(attestation1.data, attestation2.data)) {
    throw new Error("AttesterSlashing is not slashable");
  }

  // In state transition, AttesterSlashing attestations are only partially validated. Their slot and epoch could
  // be higher than the clock and the slashing would still be valid. Same applies to attestation data index, which
  // can be any arbitrary value. Must use bigint variants to hash correctly to all possible values
  for (const [i, attestation] of [attestation1, attestation2].entries()) {
    if (
      !isValidIndexedAttestationBigint(config, index2pubkey, stateSlot, validatorsLen, attestation, verifySignatures)
    ) {
      throw new Error(`AttesterSlashing attestation${i} is invalid`);
    }
  }
}