feat: add readdir delegate for sharing user homedirs

packages/backend/src/filesystem/hl_operations/hl_readdir.js

@@ -19,6 +19,7 @@
 const APIError = require("../../api/APIError");
 const { chkperm } = require("../../helpers");
 const { TYPE_DIRECTORY } = require("../FSNodeContext");
+const { LLListUsers } = require("../ll_operations/ll_listusers");
 const { LLReadDir } = require("../ll_operations/ll_readdir");
 const { LLReadShares } = require("../ll_operations/ll_readshares");
 const { HLFilesystemOperation } = require("./definitions");
@@ -48,7 +49,10 @@ class HLReadDir extends HLFilesystemOperation {
             namediff: await subject.get('name') !== user.username
             }
         );
-        if (
+        if ( subject.isRoot ) {
+            const ll_listusers = new LLListUsers();
+            children = await ll_listusers.run(this.values);
+        } else if (
             await subject.isUserDirectory() &&
             await subject.get('name') !== user.username
         ) {

packages/backend/src/filesystem/ll_operations/ll_listusers.js

@@ -0,0 +1,39 @@
+const { RootNodeSelector, NodeChildSelector } = require("../node/selectors");
+const { LLFilesystemOperation } = require("./definitions");
+
+class LLListUsers extends LLFilesystemOperation {
+    static description = `
+        List user directories which are relevant to the
+        current actor.
+    `;
+    
+    async _run () {
+        const { context } = this;
+        const svc = context.get('services');
+        const svc_permission = svc.get('permission');
+        const svc_fs = svc.get('filesystem');
+
+        const user = this.values.user;
+        const issuers = await svc_permission.list_user_permission_issuers(user);
+
+        const nodes = [];
+        
+        nodes.push(await svc_fs.node(new NodeChildSelector(
+            new RootNodeSelector(),
+            user.username,
+        )));
+
+        for ( const issuer of issuers ) {
+            const node = await svc_fs.node(new NodeChildSelector(
+                new RootNodeSelector(),
+                issuer.username));
+            nodes.push(node);
+        }
+        
+        return nodes;
+    }
+}
+
+module.exports = {
+    LLListUsers,
+};

packages/backend/src/services/auth/PermissionService.js

@@ -583,6 +583,25 @@ class PermissionService extends BaseService {
             ]
         );
     }
+    
+    /**
+     * List the users that have any permissions granted to the
+     * specified user.
+     */
+    async list_user_permission_issuers (user) {
+        const rows = await this.db.read(
+            'SELECT DISTINCT issuer_user_id FROM `user_to_user_permissions` ' +
+            'WHERE `holder_user_id` = ?',
+            [ user.id ],
+        );
+        
+        const users = [];
+        for ( const row of rows ) {
+            users.push(await get_user({ id: row.issuer_user_id }));
+        }
+
+        return users;
+    }
 
     get_parent_permissions (permission) {
         const parent_perms = [];