support for filesystem in simulator

sim/dalboard.ts

@@ -15,11 +15,13 @@ namespace pxsim {
         // TODO: not singletons
         neopixelState: NeoPixelState;
         microServoState: MicroServoState;
+        fileSystem: FileSystemState;
 
         constructor() {
             super()
 
             // components
+            this.fileSystem = new FileSystemState();
             this.builtinParts["ledmatrix"] = this.ledMatrixState = new LedMatrixState(runtime);
             this.builtinParts["buttonpair"] = this.buttonPairState = new ButtonPairState({
                 ID_BUTTON_A: DAL.MICROBIT_ID_BUTTON_A,

sim/state/filesystem.ts

@@ -0,0 +1,18 @@
+namespace pxsim.files {
+    export function appendLine(filename: string, text: string) {
+        const b = board();
+        b.fileSystem.append(filename, text + "\r\n");
+    }
+    export function appendString(filename: string, text: string) {
+        const b = board();
+        b.fileSystem.append(filename, text);
+    }
+    export function appendNumber(filename: string, value: number) {
+        const b = board();
+        b.fileSystem.append(filename, value.toString());
+    }
+    export function remove(filename: string) {
+        const b = board();
+        b.fileSystem.remove(filename);
+    }
+}