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import {assert} from './asserts';import {encode} from './base32-encode';import type {ReadonlyJSONValue} from './json';import * as utf8 from './utf8';
export const BYTE_LENGTH = 20;
export const STRING_LENGTH = 32;
// We use an opaque type so that we can make sure that a hash is always a hash.// TypeScript does not have direct support but we can use a trick described// here://// https://evertpot.com/opaque-ts-types///// The basic idea is to declare a type that cannot be created. We then use// functions that cast a string to this type.//
// By using declare we tell the type system that there is a unique symbol.// However, there is no such symbol but the type system does not care.declare const hashTag: unique symbol;
/** * Opaque type representing a hash. The only way to create one is using `parse` * or `hashOf` (except for static unsafe cast of course). */export type Hash = {[hashTag]: true};
const hashRe = /^[0-9a-v]{32}$/;const tempHashRe = /^t\/[0-9a-v]{30}$/;
/** * Computes a SHA512 hash of the given data. */export async function hashOf(value: ReadonlyJSONValue): Promise<Hash> {  const typedArray = utf8.encode(JSON.stringify(value));  const buf = await crypto.subtle.digest('SHA-512', typedArray);  const buf2 = new Uint8Array(buf, 0, BYTE_LENGTH);  return encode(buf2) as unknown as Hash;}
export function parse(s: string): Hash {  assertHash(s);  return s;}
export const emptyHash = '00000000000000000000000000000000' as unknown as Hash;
// Temp hashes needs to have the same length as non temp hashes. This is// important because we split B+Tree nodes based on the size and we want the// size to be the same independent of whether the hash is temp or not.
export const newTempHash = makeNewTempHashFunction();
/** * Creates a new temp hash function. * @param prefix The prefix of the hash. If left out the prefix is 't/' which * signifies a temp hash. */export function makeNewTempHashFunction(): () => Hash {  return makeNewFakeHashFunction('t/');}
/** * Creates a new fake hash function. * @param prefix The prefix of the hash. If the prefix starts with 't/' it is * considered a temp hash. */export function makeNewFakeHashFunction(hashPrefix: string): () => Hash {  let tempHashCounter = 0;  return () => {    // Must not overlap with hashOf results    return (hashPrefix +      (tempHashCounter++)        .toString()        .padStart(STRING_LENGTH - hashPrefix.length, '0')) as unknown as Hash;  };}
export function isHash(v: unknown): v is Hash {  return typeof v === 'string' && (hashRe.test(v) || tempHashRe.test(v));}
export function isTempHash(v: unknown): v is Hash {  return typeof v === 'string' && tempHashRe.test(v);}
export function assertNotTempHash(hash: Hash): void {  if (tempHashRe.test(hash as unknown as string)) {    throw new Error('Unexpected temp hash');  }}
export function assertHash(v: unknown): asserts v is Hash {  if (!isHash(v)) {    throw new Error(`Invalid hash: '${v}'`);  }}
/** * Generates a fake hash useful for testing. */export function fakeHash(s: string): Hash {  const fake = 'fake';  assert(    /^[a-v0-9]*$/.test(s),    `Fake hash must be a valid substring of a hash: ${s}`,  );  assert(s.length <= STRING_LENGTH - fake.length, 'Fake hash is too long');  return (fake +    s.padStart(STRING_LENGTH - fake.length, '0')) as unknown as Hash;}