import {BitArray, byteArrayEquals} from "@chainsafe/ssz";
import {FINALIZED_ROOT_DEPTH, NEXT_SYNC_COMMITTEE_DEPTH} from "@lodestar/params";
import {altair, phase0, ssz} from "@lodestar/types";

export const GENESIS_SLOT = 0;
export const ZERO_HASH = new Uint8Array(32);
export const ZERO_PUBKEY = new Uint8Array(48);
export const ZERO_SYNC_COMMITTEE = ssz.altair.SyncCommittee.defaultValue();
export const ZERO_NEXT_SYNC_COMMITTEE_BRANCH = Array.from({length: NEXT_SYNC_COMMITTEE_DEPTH}, () => ZERO_HASH);
export const ZERO_HEADER = ssz.phase0.BeaconBlockHeader.defaultValue();
export const ZERO_FINALITY_BRANCH = Array.from({length: FINALIZED_ROOT_DEPTH}, () => ZERO_HASH);
/** From https://notes.ethereum.org/@vbuterin/extended_light_client_protocol#Optimistic-head-determining-function */
const SAFETY_THRESHOLD_FACTOR = 2;

export function sumBits(bits: BitArray): number {
  return bits.getTrueBitIndexes().length;
}

export function getSafetyThreshold(maxActiveParticipants: number): number {
  return Math.floor(maxActiveParticipants / SAFETY_THRESHOLD_FACTOR);
}

export function isSyncCommitteeUpdate(update: altair.LightClientUpdate): boolean {
  return (
    // Fast return for when constructing full LightClientUpdate from partial updates
    update.nextSyncCommitteeBranch !== ZERO_NEXT_SYNC_COMMITTEE_BRANCH &&
    update.nextSyncCommitteeBranch.some((branch) => !byteArrayEquals(branch, ZERO_HASH))
  );
}

export function isFinalityUpdate(update: altair.LightClientUpdate): boolean {
  return (
    // Fast return for when constructing full LightClientUpdate from partial updates
    update.finalityBranch !== ZERO_FINALITY_BRANCH &&
    update.finalityBranch.some((branch) => !byteArrayEquals(branch, ZERO_HASH))
  );
}

export function isZeroedHeader(header: phase0.BeaconBlockHeader): boolean {
  // Fast return for when constructing full LightClientUpdate from partial updates
  return header === ZERO_HEADER || byteArrayEquals(header.bodyRoot, ZERO_HASH);
}

export function isZeroedSyncCommittee(syncCommittee: altair.SyncCommittee): boolean {
  // Fast return for when constructing full LightClientUpdate from partial updates
  return syncCommittee === ZERO_SYNC_COMMITTEE || byteArrayEquals(syncCommittee.pubkeys[0], ZERO_PUBKEY);
}