dev: hooks and sequencing functions for ServiceManager

src/putility/src/concepts/Service.js

@@ -1,4 +1,5 @@
 const { AdvancedBase } = require("../AdvancedBase");
+const ServiceFeature = require("../features/ServiceFeature");
 
 const NOOP = async () => {};
 
@@ -11,6 +12,10 @@ const TService = Symbol('TService');
  * becoming the common base for both and a useful utility in general.
  */
 class Service extends AdvancedBase {
+    static FEATURES = [
+        ServiceFeature,
+    ];
+
     async __on (id, args) {
         const handler = this.__get_event_handler(id);
 
@@ -48,7 +53,10 @@ class Service extends AdvancedBase {
                 return this._construct(o);
             },
             get_depends () {
-                return this.get_depends?.() ?? [];
+                return [
+                    ...(this.constructor.DEPENDS ?? []),
+                    ...(this.get_depends?.() ?? []),
+                ];
             }
         }
     }

src/putility/src/features/PropertiesFeature.js

@@ -36,19 +36,17 @@ module.exports = {
             };
             instance._.properties[k] = state;
 
+            let spec = null;
             if ( typeof properties[k] === 'object' ) {
-                // This will be supported in the future.
-                throw new Error(`Property ${k} in ${instance.constructor.name} ` +
-                    `is not a supported property specification.`);
+                spec = properties[k];
+            } else if ( typeof properties[k] === 'function' ) {
+                spec = {};
+                spec.value = properties[k]();
             }
 
-            let value = (() => {
-                if ( typeof properties[k] === 'function' ) {
-                    return properties[k]();
-                }
-
-                return properties[k];
-            })();
+            if ( spec === null ) {
+                throw new Error('this will never happen');
+            }
 
             Object.defineProperty(instance, k, {
                 get: () => {
@@ -60,11 +58,17 @@ module.exports = {
                             old_value: instance[k],
                         });
                     }
+                    const old_value = instance[k];
                     state.value = value;
+                    if ( spec.post_set ) {
+                        spec.post_set.call(instance, value, {
+                            old_value,
+                        });
+                    }
                 },
             });
 
-            state.value = value;
+            state.value = spec.value;
         }
     }
 }

src/putility/src/features/ServiceFeature.js

@@ -0,0 +1,28 @@
+const { TTopics } = require("../traits/traits");
+
+module.exports = {
+    install_in_instance: (instance, { parameters }) => {
+        // Convenient definition of listeners between services,
+        // which also makes these connections able to be understood as data
+        // without processing any code.
+        const hooks = instance._get_merged_static_array('HOOKS');
+        instance._.init_hooks = instance._.init_hooks ?? [];
+
+        for ( const spec of hooks ) {
+
+            // We need to wait for the service to be initialized, because
+            // that's when the dependency services have already been
+            // initialized and are ready to accept listeners.
+            instance._.init_hooks.push(() => {
+                const service_entry =
+                    instance._.context.services.info(spec.service);
+                const service_instance = service_entry.instance;
+
+                service_instance.as(TTopics).sub(
+                    spec.event,
+                    spec.do.bind(instance),
+                );
+            });
+        }
+    }
+};

src/putility/src/system/ServiceManager.js

@@ -1,5 +1,6 @@
 const { AdvancedBase } = require("../AdvancedBase");
 const { TService } = require("../concepts/Service");
+const { TeePromise } = require("../libs/promise");
 
 const mkstatus = name => {
     const c = class {
@@ -34,21 +35,26 @@ class ServiceManager extends AdvancedBase {
             return `running (since ${this.start_ts})`;
         }
     }
-    constructor () {
+    constructor ({ context }) {
         super();
 
+        this.context = context;
+
         this.services_l_ = [];
         this.services_m_ = {};
         this.service_infos_ = {};
 
-        this.init_listeners_ = {};
+        this.init_listeners_ = [];
         // services which are waiting for dependency servicces to be
         // initialized; mapped like: waiting_[dependency] = Set(dependents)
         this.waiting_ = {};
     }
     async register (name, factory, options = {}) {
+        await new Promise(rslv => setTimeout(rslv, 0));
+
         const ins = factory.create({
             parameters: options.parameters ?? {},
+            context: this.context,
         });
         const entry = {
             name,
@@ -63,10 +69,51 @@ class ServiceManager extends AdvancedBase {
     info (name) {
         return this.services_m_[name];
     }
+    get (name) {
+        const info = this.services_m_[name];
+        if ( ! info ) throw new Error(`Service not registered: ${name}`);
+        if ( ! (info.status instanceof this.constructor.StatusRunning ) ) {
+            return undefined;
+        }
+        return info.instance;
+    }
 
-    async maybe_init_ (name) {
-        const entry = this.services_m_[name];
-        const depends = entry.instance.as(TService).get_depends();
+    /**
+     * Wait for the specified list of services to be initialized.
+     * @param {*} depends - list of services to wait for
+     */
+    async wait_for_init (depends) {
+        let check;
+
+        await new Promise(rslv => {
+            check = () => {
+                // Get the list of required services that are not
+                // yet initialized
+                const waiting_for = this.get_waiting_for_(depends);
+
+                console.log('CHECK --- ', waiting_for, new Error());
+
+                // If there's nothing to wait for, remove the listener
+                // on service initializations and resolve
+                if ( waiting_for.length === 0 ) {
+                    const i = this.init_listeners_.indexOf(check);
+                    if ( i !== -1 ) {
+                        this.init_listeners_.splice(i, 1);
+                    }
+                    rslv();
+
+                    return true;
+                }
+            };
+
+            // Services might already be registered
+            if ( check() ) return;
+
+            this.init_listeners_.push(check);
+        });
+    };
+
+    get_waiting_for_ (depends) {
         const waiting_for = [];
         for ( const depend of depends ) {
             const depend_entry = this.services_m_[depend];
@@ -78,6 +125,13 @@ class ServiceManager extends AdvancedBase {
                 waiting_for.push(depend);
             }
         }
+        return waiting_for;
+    }
+
+    async maybe_init_ (name) {
+        const entry = this.services_m_[name];
+        const depends = entry.instance.as(TService).get_depends();
+        const waiting_for = this.get_waiting_for_(depends);
 
         if ( waiting_for.length === 0 ) {
             await this.init_service_(name);
@@ -97,7 +151,7 @@ class ServiceManager extends AdvancedBase {
 
     // called when a service has all of its dependencies initialized
     // and is ready to be initialized itself
-    async init_service_ (name) {
+    async init_service_ (name, modifiers = {}) {
         const entry = this.services_m_[name];
         entry.status = new this.constructor.StatusInitializing();
 
@@ -111,10 +165,18 @@ class ServiceManager extends AdvancedBase {
         const promises = [];
         if ( maybe_ready_set ) {
             for ( const dependent of maybe_ready_set.values() ) {
-                promises.push(this.maybe_init_(dependent));
+                promises.push(this.maybe_init_(dependent, {
+                    no_init_listeners: true
+                }));
             }
         }
         await Promise.all(promises);
+
+        if ( ! modifiers.no_init_listeners ) {
+            for ( const lis of this.init_listeners_ ) {
+                await lis();
+            }
+        }
     }
 }