Implement Atom save hook

Save hook is on the atom's `env` and accepts arguments: `(value, payload)`.
Calling the save hook rerenders the atom.

Example:
```
let atom = {
  name: 'my-atom',
  type: 'dom',
  render({env, value, payload}) {
    let el = document.createElement('button');
    let clicks = payload.clicks || 0;
    el.appendChild(document.createTextNode('Clicks: ' + clicks));
    el.onclick = () => {
      payload.clicks = payload.clicks || 0;
      payload.clicks++;
      env.save(value, payload);
    };
    return el;
  }
};
```

Also: improve postAbstract buildFromText to accept data for an atom,
i.e. "abc@(...jsondata...)", e.g.:
```
buildFromText('abc@("name": "my-atom", "value": "bob", "payload": {"foo": "bar"})def');
// -> "abc" + atom with name "my-atom", value "bob", payload {foo: 'bar'} + "def"
```

Fixes #399

ATOMS.md

@@ -29,6 +29,7 @@ must be of the correct type (a DOM Node for the dom renderer, a string of html o
 
   * `name` [string] - the name of the atom
   * `onTeardown` [function] - The atom can pass a callback function: `onTeardown(callbackFn)`. The callback will be called when the rendered content is torn down.
+  * `save` [function] - Call this function with the arguments `(newValue, newPayload)` to update the atom's value and payload and rerender it.
 
 ## Atom Examples
 
@@ -56,3 +57,23 @@ let atom = {
  }
 };
 ```
+
+Example dom atom that uses the `save` hook:
+```js
+let atom = {
+ name: 'click-counter',
+ type: 'dom',
+ render({env, value, payload}) {
+   let clicks = payload.clicks || 0;
+   let button = document.createElement('button');
+   button.appendChild(document.createTextNode('Clicks: ' + clicks));
+
+   button.onclick = () => {
+     payload.clicks = clicks + 1;
+     env.save(value, payload); // updates payload.clicks, rerenders button
+   };
+
+   return button;
+ }
+};
+```

src/js/models/atom-node.js

@@ -25,7 +25,15 @@ export default class AtomNode {
   get env() {
     return {
       name: this.atom.name,
-      onTeardown: (callback) => this._teardownCallback = callback
+      onTeardown: (callback) => this._teardownCallback = callback,
+      save: (value, payload={}) => {
+        this.model.value = value;
+        this.model.payload = payload;
+
+        this.editor._postDidChange();
+        this.teardown();
+        this.render();
+      }
     };
   }
 

src/js/models/post-node-builder.js

@@ -134,13 +134,13 @@ class PostNodeBuilder {
 
   /**
    * @param {String} name
-   * @param {String} [text='']
+   * @param {String} [value='']
    * @param {Object} [payload={}]
    * @param {Markup[]} [markups=[]]
    * @return {Atom}
    */
-  createAtom(name, text='', payload={}, markups=[]) {
-    const atom = new Atom(name, text, payload, markups);
+  createAtom(name, value='', payload={}, markups=[]) {
+    const atom = new Atom(name, value, payload, markups);
     atom.builder = this;
     return atom;
   }

tests/helpers/post-abstract.js

@@ -66,15 +66,46 @@ function parsePositionOffsets(text) {
 }
 
 const DEFAULT_ATOM_NAME = 'some-atom';
+const DEFAULT_ATOM_VALUE = '@atom';
 
 function parseTextIntoMarkers(text, builder) {
   text = text.replace(cursorRegex,'');
   let markers = [];
 
   if (text.indexOf('@') !== -1) {
     let atomIndex = text.indexOf('@');
-    let atom = builder.atom(DEFAULT_ATOM_NAME);
-    let pieces = [text.slice(0, atomIndex), atom, text.slice(atomIndex+1)];
+    let afterAtomIndex = atomIndex + 1;
+    let atomName = DEFAULT_ATOM_NAME,
+        atomValue = DEFAULT_ATOM_VALUE,
+        atomPayload = {};
+
+    // If "@" is followed by "( ... json ... )", parse the json data
+    if (text[atomIndex+1] === "(") {
+      let jsonStartIndex = atomIndex+1;
+      let jsonEndIndex = text.indexOf(")",jsonStartIndex);
+      afterAtomIndex = jsonEndIndex + 1;
+      if (jsonEndIndex === -1) {
+        throw new Error('Atom JSON data had unmatched "(": ' + text);
+      }
+      let jsonString = text.slice(jsonStartIndex+1, jsonEndIndex);
+      jsonString = "{" + jsonString + "}";
+      try {
+        let json = JSON.parse(jsonString);
+        if (json.name) { atomName = json.name; }
+        if (json.value) { atomValue = json.value; }
+        if (json.payload) { atomPayload = json.payload; }
+      } catch(e) {
+        throw new Error('Failed to parse atom JSON data string: ' + jsonString + ', ' + e);
+      }
+    }
+
+    // create the atom
+    let atom = builder.atom(atomName, atomValue, atomPayload);
+
+    // recursively parse the remaining text pieces
+    let pieces = [text.slice(0, atomIndex), atom, text.slice(afterAtomIndex)];
+
+    // join the markers together
     pieces.forEach(piece => {
       if (piece === atom) {
         markers.push(piece);
@@ -151,7 +182,9 @@ function parseSingleText(text, builder) {
  * Use "|" to indicate the cursor position or "<" and ">" to indicate a range.
  * Use "[card-name]" to indicate a card
  * Use asterisks to indicate bold text: "abc *bold* def"
- * Use "@" to indicate an atom
+ * Use "@" to indicate an atom, default values for name,value,payload are DEFAULT_ATOM_NAME,DEFAULT_ATOM_VALUE,{}
+ * Use "@(name, value, payload)" to specify name,value and/or payload for an atom. The string from `(` to `)` is parsed as
+ *   JSON, e.g.: '@("name": "my-atom", "value": "abc", "payload": {"foo": "bar"})' -> atom named "my-atom" with value 'abc', payload {foo: 'bar'}
  * Use "* " at the start of the string to indicate a list item ("ul")
  *
  * Examples:

tests/unit/editor/atom-lifecycle-test.js

@@ -316,3 +316,47 @@ test('mutating the content of an atom does not trigger an update', (assert) => {
     done();
   });
 });
+
+test('atom env has "save" method, rerenders atom', (assert) => {
+  let atomArgs = {};
+  let render = 0;
+  let teardown = 0;
+  let postDidChange = 0;
+  let save;
+
+  const atom = {
+    name: DEFAULT_ATOM_NAME,
+    type: 'dom',
+    render({env, value, payload}) {
+      render++;
+      atomArgs.value = value;
+      atomArgs.payload = payload;
+      save = env.save;
+
+      env.onTeardown(() => teardown++);
+
+      return makeEl('the-atom', value);
+    }
+  };
+
+  editor = Helpers.editor.buildFromText('abc|@("value": "initial-value", "payload": {"foo": "bar"})def', {autofocus: true, atoms:[atom], element: editorElement});
+  editor.postDidChange(() => postDidChange++);
+
+  assert.equal(render, 1, 'precond - renders atom');
+  assert.equal(teardown, 0, 'precond - did not teardown');
+  assert.ok(!!save, 'precond - save hook');
+  assert.deepEqual(atomArgs, {value:'initial-value', payload:{foo: "bar"}}, 'args initially empty');
+  assert.hasElement(`#the-atom`, 'precond - displays atom');
+
+  let value = 'new-value';
+  let payload = {foo: 'baz'};
+  postDidChange = 0;
+
+  save(value, payload);
+
+  assert.equal(render, 2, 'rerenders atom');
+  assert.equal(teardown, 1, 'tears down atom');
+  assert.deepEqual(atomArgs, {value, payload}, 'updates atom values');
+  assert.ok(postDidChange, 'post changed when saving atom');
+  assert.hasElement(`#the-atom:contains(${value})`);
+});