Initial import

src/service/Canon.ts

@@ -0,0 +1,56 @@
+import {Canonical} from "./Canonical";
+import {Singleton} from "@extollo/di";
+
+/**
+ * Error throw when a duplicate canonical key is registered.
+ * @extends Error
+ */
+export class DuplicateResolverKeyError extends Error {
+    constructor(key: string) {
+        super(`There is already a canonical unit with the scope ${key} registered.`)
+    }
+}
+
+/**
+ * Error throw when a key that isn't registered with the service.
+ * @extends Error
+ */
+export class NoSuchCanonicalResolverKeyError extends Error {
+    constructor(key: string) {
+        super(`There is no such canonical unit with the scope ${key} registered.`)
+    }
+
+}
+
+/**
+ * Service used to access various canonical resources.
+ */
+@Singleton()
+export class Canon {
+    /**
+     * The resources registered with this service. Map of canonical service name
+     * to canonical service instance.
+     * @type object
+     */
+    protected resources: { [key: string]: Canonical<any> } = {}
+
+    /**
+     * Get a canonical resource by its name key.
+     * @param {string} key
+     * @return Canonical
+     */
+    resource<T>(key: string): Canonical<T> {
+        if ( !this.resources[key] ) throw new NoSuchCanonicalResolverKeyError(key)
+        return this.resources[key] as Canonical<T>
+    }
+
+    /**
+     * Register a canonical resource.
+     * @param {Canonical} unit
+     */
+    registerCanonical(unit: Canonical<any>) {
+        const key = unit.canonicalItems
+        if ( this.resources[key] ) throw new DuplicateResolverKeyError(key)
+        this.resources[key] = unit
+    }
+}