Add api permissions groundwork

shared/src/apiPermissions.test.ts

@@ -0,0 +1,13 @@
+import { ApiPermissions, hasPermission } from "./apiPermissions";
+import test from "ava";
+
+test("Directly granted permissions match", t => {
+  t.is(hasPermission([ApiPermissions.ManageAccess], ApiPermissions.ManageAccess), true);
+  t.is(hasPermission([ApiPermissions.ManageAccess], ApiPermissions.Owner), false);
+});
+
+test("Implicitly granted permissions by hierarchy match", t => {
+  t.is(hasPermission([ApiPermissions.ManageAccess], ApiPermissions.EditConfig), true);
+  t.is(hasPermission([ApiPermissions.ManageAccess], ApiPermissions.ReadConfig), true);
+  t.is(hasPermission([ApiPermissions.EditConfig], ApiPermissions.ManageAccess), false);
+});

shared/src/apiPermissions.ts

@@ -0,0 +1,79 @@
+export enum ApiPermissions {
+  Owner = "OWNER",
+  ManageAccess = "MANAGE_ACCESS",
+  EditConfig = "EDIT_CONFIG",
+  ReadConfig = "READ_CONFIG",
+}
+
+interface IPermissionHierarchy extends Partial<Record<ApiPermissions, IPermissionHierarchy>> {}
+
+export const permissionHierarchy: IPermissionHierarchy = {
+  [ApiPermissions.Owner]: {
+    [ApiPermissions.ManageAccess]: {
+      [ApiPermissions.EditConfig]: {
+        [ApiPermissions.ReadConfig]: {},
+      },
+    },
+  },
+};
+
+/**
+ * Checks whether granted permissions include the specified permission, taking into account permission hierarchy i.e.
+ * that in the case of nested permissions, having a top level permission implicitly grants you any permissions nested
+ * under it as well
+ */
+export function hasPermission(grantedPermissions: ApiPermissions[], permissionToCheck: ApiPermissions): boolean {
+  // Directly granted
+  if (grantedPermissions.includes(permissionToCheck)) {
+    return true;
+  }
+
+  // Check by hierarchy
+  if (checkTreeForPermission(permissionHierarchy, grantedPermissions, permissionToCheck)) {
+    return true;
+  }
+
+  return false;
+}
+
+function checkTreeForPermission(
+  tree: IPermissionHierarchy,
+  grantedPermissions: ApiPermissions[],
+  permission: ApiPermissions,
+): boolean {
+  for (const [perm, nested] of Object.entries(tree)) {
+    // Top-level permission granted, implicitly grant all nested permissions as well
+    if (grantedPermissions.includes(perm as ApiPermissions)) {
+      // Permission we were looking for was found nested under this permission -> granted
+      if (treeIncludesPermission(nested, permission)) {
+        return true;
+      }
+
+      // Permission we were looking for was not found nested under this permission
+      // Since direct grants are not handled by this function, we can skip any further checks for this nested tree
+      continue;
+    }
+
+    // Top-level permission not granted, check further nested permissions
+    if (checkTreeForPermission(nested, grantedPermissions, permission)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+function treeIncludesPermission(tree: IPermissionHierarchy, permission: ApiPermissions): boolean {
+  for (const [perm, nested] of Object.entries(tree)) {
+    if (perm === permission) {
+      return true;
+    }
+
+    const nestedResult = treeIncludesPermission(nested, permission);
+    if (nestedResult) {
+      return true;
+    }
+  }
+
+  return false;
+}