[Feat] Type safe helpers for patch remove linked Ids

[luchillo17]

This relates mostly to deleting 1 to 1 linked documents & files, but would be nice to have type safe helpers like these ones:

/**
 * Reusable helper type: keys in T whose values are assignable to V
 * @example
 * type A = KeysOfType<{ a: string; b: number }, string>; // 'a'
 * type B = KeysOfType<{ a: string; b: number }, number>; // 'b'
 * type C = KeysOfType<{ a: string; b: number }, string | number>; // 'a' | 'b'
 */
export type KeysOfType<T, V> = {
  [K in keyof T]-?: T[K] extends V ? K : never;
}[keyof T];

export async function deleteRemovedReferences<
  T extends Doc<TableNames>,
  K extends KeysOfType<T, Id<TableNames> | undefined>,
>(ctx: MutationCtx, oldDoc: T, newDoc: Partial<T>, idFields: K[]) {
  for (const field of idFields) {
    const oldId = oldDoc?.[field] as Id<TableNames> | undefined;
    const newId = newDoc?.[field] as Id<TableNames> | undefined;

    if (oldId && !newId) {
      await ctx.db.delete(oldId);
    }
  }
}

export async function deleteRemovedFileReferences<
  T extends Doc<TableNames>,
  K extends KeysOfType<T, Id<'files'> | undefined>,
>(ctx: MutationCtx, oldDoc: T, newDoc: Partial<T>, fileFields: K[]) {
  const idsToRemove: Id<'files'>[] = fileFields
    .filter((field) => oldDoc?.[field] && !newDoc?.[field])
    .map((field) => oldDoc?.[field] as Id<'files'>);

  if (idsToRemove.length > 0) {
    await ctx.runMutation(api.files.remove, {
      ids: idsToRemove,
    });
  }
}

And here's how these are used:

export const upsertDoctorProfile = mutation({
  args: { payload: v.any() },
  handler: async (ctx, args) => {
    const identity = await ctx.auth.getUserIdentity();
    if (!identity) throw new Error('Not authenticated');

    const parsed = DoctorProfileSchema.pipe(
      DoctorProfileFilesNullToUndefinedTransform,
    ).parse(args.payload);

    const existing = await ctx.db
      .query('doctorProfiles')
      .withIndex('by_user', (q) => q.eq('userId', identity.subject))
      .unique();

    if (!existing) {
      await ctx.db.insert(
        'doctorProfiles',
        addUpdatedAt({ userId: identity.subject, ...parsed }),
      );
      return true;
    }

    // Determine files to remove before patching
    await deleteRemovedFileReferences(ctx, existing, parsed, [
      'idCardFileId',
      'diplomaFileId',
      'graduationCertificateFileId',
      'rethusCertificateFileId',
      'homologationCertificateFileId',
      'habilitationBadgeFileId',
    ]);

    await ctx.db.patch(existing._id, addUpdatedAt({ ...parsed }));
    return true;
  },
});