Simulate nondeterministic automatons

src/fsm.js

@@ -47,7 +47,7 @@ export function openAutomaton(states, editable = false) {
    */
   function updateUIState() {
     wordInput.value = builder;
-    if (state === -1 || states.length === 0 || !states[state].accepting) {
+    if (typeof Array.from(state).find((state) => states[state].accepting) === 'undefined') {
       light.classList.remove(IS_VALID);
       light.classList.add(IS_INVALID);
     } else {
@@ -55,8 +55,10 @@ export function openAutomaton(states, editable = false) {
       light.classList.add(IS_VALID);
     }
     graph.forEach((node) => node.active = false);
-    if (state in graph.nodes) {
-      graph.nodes[state].active = true;
+    for (const s of state) {
+      if (s in graph.nodes) {
+        graph.nodes[s].active = true;
+      }
     }
     viewer.restart();
   }
@@ -79,11 +81,16 @@ export function openAutomaton(states, editable = false) {
    * @param {string} letter
    */
   function step(letter) {
-    if (state === -1) {
-      return;
-    }
+    /** @type {number[]} */
+    const newStates = [];
     builder += letter;
-    state = states[state].transitions[letter] ?? -1;
+    for (const s of state) {
+      if (s in states) {
+        const transitions = states[s].transitions[letter];
+        newStates.push(...transitions);
+      }
+    }
+    state = newStates;
     updateUIState();
   }
 
@@ -126,8 +133,17 @@ export function openAutomaton(states, editable = false) {
 
 /**
  * @param {import('./examples.js').State[]} states
+ * @returns {number[]}
  */
 function findStart(states) {
-  let state = states.findIndex(state => state.start);
-  return Math.max(state, 0);
+  const starts = [];
+  for (let i = 0; i < states.length; i++) {
+    if (states[i].start) {
+      starts.push(i);
+    }
+  }
+  if (starts.length === 0) {
+    starts.push(0);
+  }
+  return starts;
 }