Add get_help function

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mosaic-tile"
-version = "0.3.1"
+version = "0.4.0"
 authors = ["Brooks J Rady <b.j.rady@gmail.com>"]
 edition = "2018"
 description = "A small client-side library for writing mosaic plugins (tiles)"

src/shim.rs

@@ -1,4 +1,4 @@
-use serde::{Deserialize, Serialize};
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use std::{io, path::Path};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
@@ -24,9 +24,7 @@ pub enum Key {
 }
 
 pub fn get_key() -> Key {
-    let mut json = String::new();
-    io::stdin().read_line(&mut json).unwrap();
-    serde_json::from_str(&json).unwrap()
+    deserialize_from_stdin().unwrap()
 }
 
 pub fn open_file(path: &Path) {
@@ -39,8 +37,20 @@ pub fn set_selectable(selectable: bool) {
     unsafe { host_set_selectable(selectable) };
 }
 
+pub fn get_help() -> Vec<String> {
+    unsafe { host_get_help() };
+    deserialize_from_stdin().unwrap_or_default()
+}
+
+fn deserialize_from_stdin<T: DeserializeOwned>() -> Option<T> {
+    let mut json = String::new();
+    io::stdin().read_line(&mut json).unwrap();
+    serde_json::from_str(&json).ok()
+}
+
 #[link(wasm_import_module = "mosaic")]
 extern "C" {
     fn host_open_file();
     fn host_set_selectable(selectable: i32);
+    fn host_get_help();
 }