1 files changed, 85 insertions, 0 deletions
diff --git a/deno_typescript/system_loader.js b/deno_typescript/system_loader.js
new file mode 100644
index 000000000..c1365f6c8
--- /dev/null
+++ b/deno_typescript/system_loader.js
@@ -0,0 +1,85 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+// This is a specialised implementation of a System module loader.
+
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+let System;
+let __inst;
+
+(() => {
+  const mMap = new Map();
+  System = {
+    register(id, deps, f) {
+      mMap.set(id, {
+        id,
+        deps,
+        f,
+        exp: {}
+      });
+    }
+  };
+
+  const gC = (data, main) => {
+    const { id } = data;
+    return {
+      id,
+      import: async id => mMap.get(id)?.exp,
+      meta: { url: id, main }
+    };
+  };
+
+  const gE = data => {
+    const { exp } = data;
+    return (id, value) => {
+      const values = typeof id === "string" ? { [id]: value } : id;
+      for (const [id, value] of Object.entries(values)) {
+        Object.defineProperty(exp, id, {
+          value,
+          writable: true,
+          enumerable: true
+        });
+      }
+    };
+  };
+
+  const iQ = [];
+
+  const enq = ids => {
+    for (const id of ids) {
+      if (!iQ.includes(id)) {
+        const { deps } = mMap.get(id);
+        iQ.push(id);
+        enq(deps);
+      }
+    }
+  };
+
+  const dr = async main => {
+    const rQ = [];
+    let id;
+    while ((id = iQ.pop())) {
+      const m = mMap.get(id);
+      const { f } = m;
+      if (!f) {
+        return;
+      }
+      rQ.push([m.deps, f(gE(m), gC(m, id === main))]);
+      m.f = undefined;
+    }
+    let r;
+    while ((r = rQ.shift())) {
+      const [deps, { execute, setters }] = r;
+      for (let i = 0; i < deps.length; i++) setters[i](mMap.get(deps[i])?.exp);
+      const e = execute();
+      if (e) await e;
+    }
+  };
+
+  __inst = async id => {
+    System = undefined;
+    __inst = undefined;
+    enq([id]);
+    await dr(id);
+    return mMap.get(id)?.exp;
+  };
+})();