Support named route groups; canonical namespaces

src/service/Canonical.ts

@@ -2,7 +2,7 @@
  * Base type for a canonical definition.
  */
 import {Canon} from "./Canon";
-import {universalPath, UniversalPath} from "@extollo/util";
+import {universalPath, UniversalPath, ErrorWithContext} from "@extollo/util";
 import {Logging} from "./Logging";
 import {Inject} from "@extollo/di";
 import * as nodePath from 'path'
@@ -14,6 +14,8 @@ export interface CanonicalDefinition {
     imported: any,
 }
 
+export type CanonicalResolver<T> = (key: string) => T | undefined
+
 /**
  * Base type for a canonical name reference.
  */
@@ -55,6 +57,12 @@ export abstract class Canonical<T> extends Unit {
      */
     protected loadedItems: { [key: string]: T } = {}
 
+    /**
+     * Object mapping canonical namespaces to resolver functions.
+     * @protected
+     */
+    protected loadedNamespaces: { [key: string]: CanonicalResolver<T> } = {}
+
     /**
      * Resolve a canonical reference from its string form to a CanonicalReference.
      * @param {string} reference
@@ -86,9 +94,36 @@ export abstract class Canonical<T> extends Unit {
     }
 
     public get(key: string): T | undefined {
+        if ( key.startsWith('@') ) {
+            const [namespace, ...rest] = key.split(':')
+            key = rest.join(':')
+
+            if ( !this.loadedNamespaces[namespace] ) {
+                throw new ErrorWithContext(`Unable to find namespace for ${this.canonicalItem}: ${namespace}`, {
+                    canonicalItem: this.canonicalItem,
+                    namespace,
+                    key,
+                })
+            }
+
+            return this.loadedNamespaces[namespace](key)
+        }
+
         return this.loadedItems[key]
     }
 
+    public registerNamespace(name: string, resolver: CanonicalResolver<T>) {
+        if ( !name.startsWith('@') ) {
+            throw new ErrorWithContext(`Canonical namespaces must start with @.`, { name })
+        }
+
+        if ( this.loadedNamespaces[name] ) {
+            this.logging.warn(`Replacing canonical namespace resolver for: ${name}`)
+        }
+
+        this.loadedNamespaces[name] = resolver
+    }
+
     public async up() {
         for await ( const entry of this.path.walk() ) {
             if ( !entry.endsWith(this.suffix) ) {