ttrpg-character-builder/app/shared/snapshot.ts

import { createHash } from 'node:crypto';

import type { SystemDefinition } from './types.ts';

/** Canonical JSON for stable hashing (sorted keys). */
export function canonicalJson(value: unknown): string {
  return JSON.stringify(sortKeys(value));
}

function sortKeys(value: unknown): unknown {
  if (Array.isArray(value)) return value.map(sortKeys);
  if (value && typeof value === 'object') {
    const obj = value as Record<string, unknown>;
    const out: Record<string, unknown> = {};
    for (const key of Object.keys(obj).sort()) {
      out[key] = sortKeys(obj[key]);
    }
    return out;
  }
  return value;
}

export function snapshotHash(system: SystemDefinition): string {
  const payload = {
    id: system.id,
    schemaVersion: system.schemaVersion,
    revision: system.revision,
    bricks: system.bricks,
    creationRules: system.creationRules,
    sheetLayout: system.sheetLayout,
    compendium: system.compendium,
  };
  return createHash('sha256').update(canonicalJson(payload)).digest('hex');
}