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import {assertString} from '../asserts';import {Hash, makeNewFakeHashFunction, hashOf} from '../hash';import type {Value} from '../kv/store';
type Refs = readonly Hash[];
export interface Chunk<V extends Value = Value> {  readonly hash: Hash;  readonly data: V;  /**   * Meta is an array of refs. If there are no refs we do not write a meta   * chunk.   */  readonly meta: Refs;}
class ChunkImpl<V extends Value = Value> implements Chunk<V> {  readonly hash: Hash;  readonly data: V;  readonly meta: Refs;
  constructor(hash: Hash, data: V, meta: Refs) {    this.hash = hash;    this.data = data;    this.meta = meta;  }}
export function assertMeta(v: unknown): asserts v is Refs {  if (!Array.isArray(v)) {    throw new Error('Meta must be an array');  }  for (const e of v) {    assertString(e);  }}
export function createChunk<V extends Value>(  data: V,  refs: Refs,  chunkHasher: ChunkHasher,): Chunk<V> {  const hash = chunkHasher(data);  return new ChunkImpl(hash, data, refs);}
export function createChunkWithHash<V extends Value>(  hash: Hash,  data: V,  refs: Refs,): Chunk<V> {  return new ChunkImpl(hash, data, refs);}
export async function createChunkWithNativeHash<V extends Value>(  data: V,  refs: Refs,): Promise<Chunk<V>> {  const hash = await hashOf(data);  return createChunkWithHash(hash, data, refs);}
export type CreateChunk = <V extends Value>(data: V, refs: Refs) => Chunk<V>;
export type ChunkHasher = (data: Value) => Hash;
export function makeTestChunkHasher(prefix = 'fake'): ChunkHasher {  const makeHash = makeNewFakeHashFunction(prefix);  const map = new Map<string, Hash>();  const ch: ChunkHasher = data => {    const jsonString = JSON.stringify(data);    const h = map.get(jsonString);    if (h) {      return h;    }    const h2 = makeHash();    map.set(jsonString, h2);    return h2;  };  return ch;}
export function throwChunkHasher(_data: Value): Hash {  throw new Error('unexpected call to compute chunk hash');}