dev: add endpoint to read app icons

src/backend/src/services/AppIconService.js

@@ -1,6 +1,8 @@
 const { HLWrite } = require("../filesystem/hl_operations/hl_write");
 const { LLMkdir } = require("../filesystem/ll_operations/ll_mkdir");
+const { LLRead } = require("../filesystem/ll_operations/ll_read");
 const { NodePathSelector, NodeChildSelector, RootNodeSelector } = require("../filesystem/node/selectors");
+const { Endpoint } = require("../util/expressutil");
 const { buffer_to_stream } = require("../util/streamutil");
 const BaseService = require("./BaseService");
 
@@ -11,6 +13,52 @@ class AppIconService extends BaseService {
         sharp: require('sharp'),
     }
 
+    async ['__on_install.routes'] (_, { app }) {
+        Endpoint({
+            route: '/app-icon/:app_uid/:size',
+            methods: ['GET'],
+            handler: async (req, res) => {
+                // Validate parameters
+                let { app_uid, size } = req.params;
+                if ( ! ICON_SIZES.includes(Number(size)) ) {
+                    res.status(400).send('Invalid size');
+                    return;
+                }
+                if ( ! app_uid.startsWith('app-') ) {
+                    app_uid = `app-${app_uid}`;
+                }
+
+                // Get icon file node
+                const dir_app_icons = await this.get_app_icons();
+                const node = await dir_app_icons.getChild(`${app_uid}-${size}.png`);
+                await node.fetchEntry();
+
+                const svc_su = this.services.get('su');
+                const ll_read = new LLRead();
+                const stream = await ll_read.run({
+                    fsNode: node,
+                    actor: await svc_su.get_system_actor(),
+                });
+
+                res.set('Content-Type', 'image/png');
+                stream.pipe(res);
+            },
+        }).attach(app);
+    }
+
+    async get_app_icons () {
+        if ( this.dir_app_icons ) {
+            return this.dir_app_icons;
+        }
+
+        const svc_fs = this.services.get('filesystem');
+        const dir_app_icons = await svc_fs.node(
+            new NodePathSelector('/system/app_icons')
+        );
+
+        this.dir_app_icons = dir_app_icons;
+    }
+    
     async ['__on_user.system-user-ready'] () {
         const svc_su = this.services.get('su');
         const svc_fs = this.services.get('filesystem');
@@ -30,6 +78,7 @@ class AppIconService extends BaseService {
                 actor: await svc_su.get_system_actor(),
             });
         }
+        this.dir_app_icons = dir_app_icons;
 
         // Listen for new app icons
         const svc_event = this.services.get('event');