fix: better type inference via getBox(es)

DenizUgur · DenizUgur · commit 9f49117c27d6 · 2025-07-30T15:45:19.000-07:00
relates to #499
diff --git a/entries/types.ts b/entries/types.ts
@@ -89,6 +89,18 @@ export type SampleGroupEntryKind = InstanceOf<
   Extends<BoxRegistry['sampleGroupEntry'], typeof SampleGroupEntry>
 >;
 
+export type AllRegisteredBoxes = {
+  [K in AllIdentifiers]: K extends keyof BoxRegistry['box']
+    ? InstanceOf<BoxRegistry['box'][K]>
+    : K extends keyof BoxRegistry['sampleEntry']
+      ? InstanceOf<BoxRegistry['sampleEntry'][K]>
+      : K extends keyof BoxRegistry['sampleGroupEntry']
+        ? InstanceOf<BoxRegistry['sampleGroupEntry'][K]>
+        : K extends keyof BoxRegistry['uuid']
+          ? InstanceOf<BoxRegistry['uuid'][K]>
+          : never;
+};
+
 export interface FragmentedTrack<TUser> {
   id: number;
   user: TUser;
diff --git a/src/isofile.ts b/src/isofile.ts
@@ -84,6 +84,7 @@ import { BoxRegistry } from '#/registry';
 import { MP4BoxStream } from '#/stream';
 import type {
   AllIdentifiers,
+  AllRegisteredBoxes,
   BoxKind,
   Description,
   EntityGroup,
@@ -921,17 +922,17 @@ export class ISOFile<TSegmentUser = unknown, TSampleUser = unknown> {
   }
 
   /* Find and return specific boxes using recursion and early return */
-  getBox(type: AllIdentifiers) {
+  getBox<T extends AllIdentifiers>(type: T): AllRegisteredBoxes[T] {
     const result = this.getBoxes(type, true);
     return result.length ? result[0] : undefined;
   }
 
-  getBoxes(type: AllIdentifiers, returnEarly: boolean) {
-    const result: Array<Box> = [];
+  getBoxes<T extends AllIdentifiers>(type: T, returnEarly: boolean) {
+    const result: Array<AllRegisteredBoxes[T]> = [];
 
     const sweep = (root: Box | ISOFile) => {
       if (root instanceof Box && root.type && root.type === type) {
-        result.push(root);
+        result.push(root as unknown as AllRegisteredBoxes[T]);
       }
 
       const inner: Array<Box> = [];
