diff --git a/dingus/dingus.js b/dingus/dingus.js
index 9a4c6a9..70b92df 100644
--- a/dingus/dingus.js
+++ b/dingus/dingus.js
@@ -2,155 +2,242 @@ const STATUS = document.getElementById("status-line");
 const ERRORS = document.getElementById("error-root");
 const TREE = document.getElementById("tree-root");
 
-function show_tree() {
-  ERRORS.classList.add("hidden");
-  TREE.classList.remove("hidden");
-}
-
-function show_errors() {
-  ERRORS.classList.remove("hidden");
-  TREE.classList.add("hidden");
-}
-
-const DOC_CHAINS = {};
-function chain_document_submit(kind, editor, on_success) {
-  let pending = null;
-  let next = null;
-
-  function do_submit() {
-    const document = editor.doc.getValue();
-    if (window.localStorage) {
-      window.localStorage.setItem(kind, document);
-    }
-
-    if (pending) {
-      console.log("Old still pending, parking it...");
-      next = document;
-    } else {
-      pending = document;
-      worker.postMessage({kind, data: document});
-      console.log("Document submitted");
-    }
-  }
-
-  function on_result(message) {
-    pending = null;
-    if (next) {
-      pending = next;
-      next = null;
-
-      worker.postMessage({kind, data: document});
-      console.log("Posted another document");
-    }
-
-    if (message.status === "ok" && on_success) {
-      on_success(message);
-    }
-
-    if (message.status === "error") {
-      render_errors(message.errors);
-    }
-  }
-  DOC_CHAINS[kind] = on_result;
-
-  let change_timer_id = null;
-  editor.doc.on("change", () => {
-    clearTimeout(change_timer_id);
-    change_timer_id = setTimeout(() => {
-      change_timer_id = null;
-      do_submit();
-    }, 100);
-  });
-
-  if (window.localStorage) {
-    const value = window.localStorage.getItem(kind);
-    if (value) {
-      editor.doc.setValue(value);
-    }
-  }
-
-  return do_submit;
-}
-
-const worker = new Worker('worker.js');
-worker.onmessage = (e) => {
-  const message = e.data;
-
-  const chain = DOC_CHAINS[message.kind];
-  if (chain) {
-    chain(message);
-  }
-
-  STATUS.innerText = message.message;
+const INITIAL_STATE = {
+  worker: null,
+  status: "Initializing...",
+  tree: null,
+  errors: [],
+  grammar: {
+    last: null,
+    pending: null,
+    next: null,
+  },
+  input: {
+    last: null,
+    pending: null,
+    next: null,
+  },
 };
 
-let grammar_editor = null;
-let input_editor = null;
 
-function render_errors(errors) {
-  ERRORS.innerText = errors.join("\n")
-}
+/*
+ * Render a tree `node` into the DOM.
+ */
+function render_tree_node(node, input_editor) {
+  const tree_div = document.createElement("div");
+  tree_div.classList.add("parsed-node");
 
-function render_parse_results(message) {
-  function render_tree_node(parent, node) {
-    const tree_div = document.createElement("div");
-    tree_div.classList.add("parsed-node");
+  const node_label = document.createElement("a");
+  node_label.innerText = node.name;
+  node_label.setAttribute("href", "#");
+  node_label.onclick = () => {
+    const doc = input_editor.doc;
+    doc.setSelection(
+      doc.posFromIndex(node.start),
+      doc.posFromIndex(node.end),
+      {scroll: true},
+    );
+  };
+  if (node.start == node.end) {
+    node_label.classList.add("parsed-error-node");
+  }
+  tree_div.appendChild(node_label);
 
-    const node_label = document.createElement("a");
-    node_label.innerText = node.name;
-    node_label.setAttribute("href", "#");
-    node_label.onclick = () => {
-      const doc = input_editor.doc;
-      doc.setSelection(
-        doc.posFromIndex(node.start),
-        doc.posFromIndex(node.end),
-        {scroll: true},
-      );
-    };
-    if (node.start == node.end) {
-      node_label.classList.add("parsed-error-node");
+
+  if (node.kind === "tree") {
+    tree_div.classList.add("parsed-tree");
+    for (const child of node.children) {
+      tree_div.appendChild(render_tree_node(child, input_editor));
     }
-    tree_div.appendChild(node_label);
-
-
-    if (node.kind === "tree") {
-      tree_div.classList.add("parsed-tree");
-      for (const child of node.children) {
-        render_tree_node(tree_div, child);
-      }
-    } else {
-      tree_div.classList.add("parsed-token");
-    }
-    parent.appendChild(tree_div);
+  } else {
+    tree_div.classList.add("parsed-token");
   }
 
-  const root = document.getElementById("tree-root");
-  root.innerHTML = "";
-  render_tree_node(root, message.tree);
-  render_errors(message.errors);
+  return tree_div;
 }
 
+
+/*
+ * Render the state out into the DOM, the bindings to which we have already
+ * established. Fully side-effecting, no shadow DOM here.
+ */
+function render_state(state, input_editor) {
+  STATUS.innerText = state.status;
+
+  ERRORS.innerText = state.errors.join("\n");
+
+  TREE.innerHTML = "";
+  if (state.tree) {
+    TREE.appendChild(render_tree_node(state.tree, input_editor));
+  }
+}
+
+/*
+ * Post a changed document out to the worker, if the worker can take it,
+ * otherwise just queue it for submission.
+ */
+function post_document(worker, kind, state, document) {
+  if (window.localStorage) {
+    window.localStorage.setItem(kind, document);
+  }
+
+  let new_state = {...state};
+  if (new_state.pending) {
+    new_state.next = document;
+  } else {
+    new_state.pending = document;
+    new_state.next = null;
+    worker.postMessage({kind, data: document});
+  }
+  return new_state;
+}
+
+/*
+ * Handle a document submission by rotating in the next document to be
+ * submitted. (Documents flow from next -> pending -> last.)
+ */
+function rotate_document(worker, kind, state) {
+  let new_state = {...state, last: state.pending, pending: null};
+  if (new_state.next) {
+    new_state.pending = new_state.next;
+    new_state.next = null;
+    worker.postMessage({kind, data: new_state.pending});
+  }
+  return new_state;
+}
+
+/*
+ * Update the state given the message and return a new state.
+ *
+ * This can be side-effecting, in that it might also post messages to the worker
+ * (to rotate documents and whatnot). (Maybe we should do something about that?)
+ */
+function update(state, message) {
+  let new_state = {...state};
+  if (message.message) {
+    new_state.status = message.message;
+  }
+
+  if (message.kind === "grammar") {
+    if (message.status === "changed") {
+      new_state.grammar = post_document(
+        new_state.worker,
+        "grammar",
+        new_state.grammar,
+        message.data,
+      );
+    } else if (message.status === "ok" || message.status === "error") {
+      new_state.grammar = rotate_document(new_state.worker, "grammar", new_state.grammar);
+
+      if (message.status === "ok") {
+        // Re-submit the input, using whatever the latest document state was.
+        new_state.input = post_document(
+          new_state.worker,
+          "input",
+          new_state.input,
+          new_state.input.next || new_state.input.pending || new_state.input.last,
+        );
+      }
+
+      if (message.status === "error") {
+        // Record the errors.
+        new_state.errors = [];
+      }
+    }
+  }
+
+  if (message.kind === "input") {
+    if (message.status === "changed") {
+      new_state.input = post_document(
+        new_state.worker,
+        "input",
+        new_state.input,
+        message.data,
+      );
+    } else if (message.status === "ok" || message.status === "error") {
+      new_state.input = rotate_document(new_state.worker, "input", new_state.input);
+
+      if (message.status === "ok") {
+        new_state.tree = message.tree;
+        new_state.errors = message.errors;
+      }
+
+      if (message.status === "error") {
+        new_state.errors = message.errors;
+      }
+    }
+  }
+
+  //console.log(state, message, new_state);
+  return new_state;
+}
+
+/*
+ * Construct a new "message handler" by wrapping up the state into an update/
+ * render loop.
+ */
+function message_handler(worker, input_editor) {
+  let state = {...INITIAL_STATE, worker};
+  render_state(state, input_editor);
+
+  return (message) => {
+    state = update(state, message);
+    render_state(state, input_editor);
+  };
+}
+
+// And we can set up the codemirror editors to publish their changes.
 function setup_editors() {
-  grammar_editor = CodeMirror.fromTextArea(
+  function setup_editor(kind, editor, handler) {
+    let change_timer_id = null;
+    editor.doc.on("change", () => {
+      clearTimeout(change_timer_id);
+      change_timer_id = setTimeout(() => {
+        change_timer_id = null;
+        handler({
+          kind,
+          status: "changed",
+          data: editor.doc.getValue(),
+        });
+      }, 100);
+    });
+
+    if (window.localStorage) {
+      const value = window.localStorage.getItem(kind);
+      if (value) {
+        editor.doc.setValue(value);
+      }
+    }
+  }
+
+  // Construct the editors and worker and stuff but don't wire the handler
+  // yet...
+  const worker = new Worker('worker.js');
+  const grammar_editor = CodeMirror.fromTextArea(
     document.getElementById("grammar"),
     {
       lineNumbers: true,
       mode: "python",
     },
   );
-
-  input_editor = CodeMirror.fromTextArea(
+  const input_editor = CodeMirror.fromTextArea(
     document.getElementById("input"),
     {
       lineNumbers: true,
     },
   );
 
-  const submit_input = chain_document_submit(
-    "input", input_editor, render_parse_results);
+  // ...now we can construct the handler with what it needs....
+  const handler = message_handler(worker, input_editor);
 
-  chain_document_submit(
-    "grammar", grammar_editor, submit_input);
+  // ...and finally hook the event sources to the handler.
+  worker.onmessage = (e) => {
+    const message = e.data;
+    handler(message);
+  };
+
+  setup_editor("grammar", grammar_editor, handler);
+  setup_editor("input", input_editor, handler);
 }
 
 setup_editors();