From 4cb239c6a0080f9d8cf3ed29544fcaa3e84301cc Mon Sep 17 00:00:00 2001
From: Sven Slootweg <admin@cryto.net>
Date: Wed, 2 Feb 2022 14:16:02 +0100
Subject: [PATCH] WIP, memoize lazy evaluation wrappers

---
 .gitignore                         |  1 +
 run.js                             | 38 +++++++++++++++++++++++-------
 src/astformer/util/measure-time.js |  2 ++
 src/transformers/attribute-sets.js |  2 +-
 src/transformers/functions.js      |  2 +-
 src/transformers/index.js          | 11 +--------
 6 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/.gitignore b/.gitignore
index 1f04195..1907e34 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 node_modules
 private-notes.txt
+old
diff --git a/run.js b/run.js
index 2836b1c..2b89f3a 100644
--- a/run.js
+++ b/run.js
@@ -4,6 +4,7 @@ const fs = require("fs");
 const assert = require("assert");
 
 const transpile = require("./src/transpile");
+const measureTime = require("./src/astformer/util/measure-time");
 
 assert(process.argv[2] != null);
 
@@ -12,13 +13,34 @@ const nixFile = fs.readFileSync(nixFilePath, "utf8");
 
 let transpiled = transpile(nixFile);
 
-console.log("-- EVALUATION RESULT:");
-
-console.log(eval(transpiled)({
+const api = {
 	builtins: {},
-	$$jsNix$extend: function (base, props) {
-		let newObject = Object.create(base);
-		Object.assign(newObject, props);
-		return newObject;
+	$$jsNix$memoize: function (func) {
+		let isCalled = false;
+		let storedResult;
+
+		return function (arg) {
+			if (isCalled === false) {
+				storedResult = func(arg);
+				isCalled = true;
+			}
+
+			return storedResult;
+		};
 	}
-}));
+};
+
+// TODO: Switch to Node `vm` API instead, and check whether there's a polyfill for it for non-Node environments, build a custom one if not
+const context = { module: {}, exports: {} };
+context.module.exports = exports;
+
+new Function("module", transpiled)(context.module);
+
+console.log("-- EVALUATION RESULT:");
+
+// Warm-up for hot VM performance testing
+// for (let i = 0; i < 10000; i++) {
+// 	context.module.exports(api);
+// }
+
+console.log(measureTime(() => context.module.exports(api)));
diff --git a/src/astformer/util/measure-time.js b/src/astformer/util/measure-time.js
index db17728..21576ee 100644
--- a/src/astformer/util/measure-time.js
+++ b/src/astformer/util/measure-time.js
@@ -1,5 +1,7 @@
 "use strict";
 
+// FIXME: Make separate package, measure-function-call or so
+
 function hrtimeToNanoseconds(time) {
 	// If the numbers here become big enough to cause loss of precision, we probably have bigger issues than numeric precision...
 	return (time[0] * 1e9) + time[1];
diff --git a/src/transformers/attribute-sets.js b/src/transformers/attribute-sets.js
index 30741ac..700792c 100644
--- a/src/transformers/attribute-sets.js
+++ b/src/transformers/attribute-sets.js
@@ -13,7 +13,7 @@ let tmplCallLazy = template(`
 `);
 
 let tmplLazyWrapper = template(`(
-	() => %%expression%%
+	$$jsNix$memoize(() => %%expression%%)
 )`);
 
 let tmplLazyWrapperRecursive = template(`(
diff --git a/src/transformers/functions.js b/src/transformers/functions.js
index 32ecbb5..ca8812d 100644
--- a/src/transformers/functions.js
+++ b/src/transformers/functions.js
@@ -34,7 +34,7 @@ let tmplFunctionCall = template(`
 
 // NOTE: Duplicated from `attribute-sets` for now
 let tmplLazyWrapper = template(`(
-	() => %%expression%%
+	$$jsNix$memoize(() => %%expression%%)
 )`);
 
 function functionDefinition({ universal, formals, body }) {
diff --git a/src/transformers/index.js b/src/transformers/index.js
index 9007aa9..e81027e 100644
--- a/src/transformers/index.js
+++ b/src/transformers/index.js
@@ -17,20 +17,11 @@ const printAst = require("../print-ast");
 
 // FIXME: Make strict mode! Otherwise objects will inherit from `global`
 let tmplModule = template(`
-	module.exports = function({ builtins, $$jsNix$extend }) {
+	module.exports = function({ builtins, $$jsNix$memoize }) {
 		return %%contents%%;
 	};
 `);
 
-
-let tmplLetIn = template(`
-	(() => {
-		%%letBindings%%
-
-		return %%expression%%;
-	})()
-`);
-
 let tmplObjectDynamic = template(`
 	(() => {
 		let $$nixJS_object = {};