Keep a 16 program cache for ircbotRun()

README.md

@@ -23,7 +23,6 @@ TODO
 ### gir.js
 * Make VM and transformMultiplyLoops use a Proxied object that gives out 0
   for nonexistent elements for tape and allows using [] interface
-* Keep a cache of compiled programs in `ircbotRun()`
 * Support for other types of EOF?
 
 ### gir.html

gir.js

@@ -928,10 +928,64 @@ function compile(program, enableExtensions = true) {
 	return optimize(parse(program, enableExtensions));
 }
 
+const programCacheSize = 16;
+// string → {compiled: [flatCommandObjects], extensions: bool}
+let programCache = new Map();
+
+// (string, bool) → [flatCommandObjects]
+function cachedCompile(program, enableExtensions = true) {
+	function compileToCache() {
+		console.log('compile'); //debg
+		// Are we already in the cache? If yes, drop the old one,
+		// since something must have been changed if we're called
+		if(programCache.has(program)) {
+			programCache.delete(program);
+		}
+
+		let compiled = compile(program, enableExtensions);
+		programCache.set(program, {compiled: compiled,
+			extensions: enableExtensions});
+
+		// Are we over the cache size? If yes, drop the least
+		// recently added
+		if(programCache.size > programCacheSize) {
+			console.log('delete');
+			// .keys() gives them in insertion order. Since
+			// there isn't a nice way to extract a thing out
+			// of an iterator, use a for loop and break out
+			// after first round
+			for(let leastRecentlyUsed of programCache.keys()) {
+				programCache.delete(leastRecentlyUsed);
+				break;
+			}
+		}
+	}
+
+	if(programCache.has(program)) {
+		// There is a compiled version of this program
+		let {compiled, extensions} = programCache.get(program);
+
+		// If extensions enabled state is the same as ours, we can
+		// just update the useOrder and return this
+		// If not, we need to compile a new program
+		if(extensions == enableExtensions) {
+			return compiled;
+		} else {
+			compileToCache();
+			let {compiled} = programCache.get(program);
+			return compiled;
+		}
+	} else {
+		compileToCache();
+		let {compiled} = programCache.get(program);
+		return compiled;
+	}
+}
+
 // (string, string, int) → string
 function ircbotRun(program, input, maxCycles = 400000) {
 	// TODO; Cache programs
-	let compiled = compile(program);
+	let compiled = cachedCompile(program);
 	let vm = newVM(compiled, encodeUTF8(input));
 
 	let result = runVM(vm, maxCycles);