ai/src/util/canonical-hash.ts

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import { convertUint8ArrayToBase64 } from '@ai-sdk/provider-utils';

const encoder = new TextEncoder();

/**
 * Deterministic JSON serialization: object keys are sorted so that two
 * structurally-equal values always produce the same string regardless of key
 * insertion order. Used as the input to content hashing.
 */
export function canonicalJSON(value: unknown): string {
  if (value === null || value === undefined) {
    return JSON.stringify(value);
  }
  if (typeof value !== 'object') {
    return JSON.stringify(value);
  }
  if (Array.isArray(value)) {
    return `[${value.map(canonicalJSON).join(',')}]`;
  }
  const keys = Object.keys(value as Record<string, unknown>).sort();
  const entries = keys.map(
    k =>
      `${JSON.stringify(k)}:${canonicalJSON((value as Record<string, unknown>)[k])}`,
  );
  return `{${entries.join(',')}}`;
}

export function toBase64url(bytes: Uint8Array): string {
  return convertUint8ArrayToBase64(bytes)
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=+$/g, '');
}

/**
 * Canonical SHA-256 digest (base64url) of an arbitrary JSON-serializable value.
 */
export async function hashCanonical(value: unknown): Promise<string> {
  const digest = await crypto.subtle.digest(
    'SHA-256',
    encoder.encode(canonicalJSON(value)),
  );
  return toBase64url(new Uint8Array(digest));
}