Some documentation for the light model client

Author: slisson

light-model-client/README.md

@@ -0,0 +1,36 @@
+# Light Model Client
+
+This client is designed to connect to MPS or the Modelix model server.
+It is implemented in Kotlin multi-platform so that it can run in the browser.
+
+While the "advanced model client" provides more features and should be used for long-running processes,
+the "light model client" is optimized for a lower resource consumption and short living processes like in a browser tab.
+The server is responsible for resolving conflicts and to keep the client side model in a valid state.
+
+Creating an instance that loads the entire model from the server can be done like this:
+
+```
+val client = LightModelClientJVM.builder()
+    .url("ws://localhost/json/v2/test-repo/ws") // optional, by default it connects to the MPS plugin
+    .build()
+client.changeQuery(buildModelQuery { 
+    root { 
+        descendants {  }
+    }
+})
+val rootNode = client.waitForRootNode()!!
+client.runRead { 
+    val modules = rootNode.getChildren("modules")
+    // ...
+}
+```
+
+You have to set a *model query* using `changeQuery()` to tell the server in what data you are interested in.
+Without a query the client will not receive any data.
+If you try to access a node that is not included in you *model query* an exception is thrown.
+You can use `INode.isLoaded()` to check is a node was loaded on the client to prevent this exception.
+You can also filter a list of nodes like this: `node.getChildren("modules").filterLoaded()`,
+to iterate only over the nodes that are included in your query.
+
+To read/write any nodes you have to start a read/write transaction by using `runRead {}`/`runWrite {}`.
+An exception is thrown when you try to access a node outside a transaction.