feat(director): add authored camera directions and anchors

src/director/documentFields.js

@@ -0,0 +1,94 @@
+/** Shared bounded JSON and field checks for scene formats. */
+export const SCENE_DOCUMENT_LIMITS = Object.freeze({
+  bytes: 5 * 1024 * 1024,
+  scenes: 256,
+  shots: 10000,
+  collection: 10000,
+  depth: 24,
+  nodes: 200000,
+  string: 65536,
+});
+
+/** A project error identifies a field without echoing its supplied value. */
+export class SceneDocumentError extends Error {
+  constructor(path, reason) {
+    super(`${path}: ${reason}`);
+    this.name = 'SceneDocumentError';
+    this.path = path;
+  }
+}
+export const fail = (path, reason) => {
+  throw new SceneDocumentError(path, reason);
+};
+export const object = (value, path) => {
+  if (!value || typeof value !== 'object' || Array.isArray(value))
+    fail(path, 'expected an object');
+};
+export function fields(value, path, allowed) {
+  object(value, path);
+  for (const key of Object.keys(value)) {
+    if (!allowed.includes(key)) fail(`${path}.${key}`, 'unsupported field');
+  }
+}
+export function string(value, path, max = 256) {
+  if (typeof value !== 'string' || !value.trim() || value.length > max)
+    fail(path, `expected nonempty text, at most ${max} characters`);
+}
+export function number(value, path, min, max, legacy) {
+  const numeric =
+    legacy && typeof value === 'string' && value.trim() ? Number(value) : value;
+  if (
+    typeof numeric !== 'number' ||
+    !Number.isFinite(numeric) ||
+    numeric < min ||
+    numeric > max
+  )
+    fail(path, `expected a number from ${min} to ${max}`);
+}
+export function optional(value, key, path, check) {
+  if (Object.hasOwn(value, key)) check(value[key], `${path}.${key}`);
+}
+export function array(value, path, max = SCENE_DOCUMENT_LIMITS.collection) {
+  if (!Array.isArray(value) || value.length > max)
+    fail(path, `expected an array of at most ${max} entries`);
+}
+export function ids(value, path) {
+  array(value, path);
+  value.forEach((id, index) => string(id, `${path}[${index}]`));
+}
+export function uniqueId(value, path, seen) {
+  if (!Object.hasOwn(value, 'id')) return; // Legacy omissions receive an ID once during migration.
+  string(value.id, `${path}.id`);
+  if (seen.has(value.id)) fail(`${path}.id`, 'duplicate ID');
+  seen.add(value.id);
+}
+export function jsonTree(value, path, budget, depth = 0) {
+  if (
+    ++budget.nodes > SCENE_DOCUMENT_LIMITS.nodes ||
+    depth > SCENE_DOCUMENT_LIMITS.depth
+  )
+    fail(path, 'project complexity limit exceeded');
+  if (value === null || typeof value === 'boolean') return;
+  if (typeof value === 'string') {
+    if (value.length > SCENE_DOCUMENT_LIMITS.string)
+      fail(path, 'text is too long');
+    return;
+  }
+  if (typeof value === 'number' && Number.isFinite(value)) return;
+  if (!value || typeof value !== 'object') fail(path, 'expected a JSON value');
+  if (
+    Object.getPrototypeOf(value) !== Object.prototype &&
+    !Array.isArray(value) &&
+    Object.getPrototypeOf(value) !== null
+  )
+    fail(path, 'expected a JSON object');
+  const entries = Object.entries(value);
+  if (entries.length > SCENE_DOCUMENT_LIMITS.collection)
+    fail(path, 'too many entries');
+  for (const [key, child] of entries) {
+    if (['__proto__', 'constructor', 'prototype'].includes(key))
+      fail(path, 'unsafe object key');
+    if (key.length > 256) fail(path, 'field name is too long');
+    jsonTree(child, `${path}.${key}`, budget, depth + 1);
+  }
+}