Add automation editor (#275)

* Add automation editor

* Build JS before running tests

* Add browser warning

* Re-order from/to in state

preact-src/json_textarea.js

@@ -0,0 +1,56 @@
+import { h, Component } from 'preact';
+
+
+export default class JSONTextArea extends Component {
+  constructor(props) {
+    super(props);
+    this.state.isValid = true;
+    this.state.value = JSON.stringify(props.value || {}, null, 2);
+    this.onChange = this.onChange.bind(this);
+  }
+
+  onChange(ev) {
+    const value = ev.target.value;
+    let parsed;
+    let isValid;
+
+    try {
+      parsed = JSON.parse(value);
+      isValid = true;
+    } catch (err) {
+      // Invalid JSON
+      isValid = false;
+    }
+
+    this.setState({
+      value,
+      isValid,
+    });
+    if (isValid) {
+      this.props.onChange(parsed);
+    }
+  }
+
+  componentWillReceiveProps({ value }) {
+    this.setState({
+      value: JSON.stringify(value, null, 2),
+      isValid: true,
+    });
+  }
+
+  render(props, { value, isValid }) {
+    const style = {
+      minWidth: 300,
+    };
+    if (!isValid) {
+      style.border = '1px solid red';
+    }
+    return (
+      <textarea
+        value={value}
+        style={style}
+        onChange={this.onChange}
+      />
+    );
+  }
+}