Added a get_help function to the plugin API

src/errors.rs

@@ -266,6 +266,8 @@ impl From<&PluginInstruction> for PluginContext {
 
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub enum AppContext {
+    GetState,
+    SetState,
     Exit,
     Error,
 }
@@ -273,6 +275,8 @@ pub enum AppContext {
 impl From<&AppInstruction> for AppContext {
     fn from(app_instruction: &AppInstruction) -> Self {
         match *app_instruction {
+            AppInstruction::GetState(_) => AppContext::GetState,
+            AppInstruction::SetState(_) => AppContext::SetState,
             AppInstruction::Exit => AppContext::Exit,
             AppInstruction::Error(_) => AppContext::Error,
         }

src/input.rs

@@ -1,9 +1,8 @@
-/// Module for handling input
-use crate::os_input_output::OsApi;
 use crate::pty_bus::PtyInstruction;
 use crate::screen::ScreenInstruction;
 use crate::CommandIsExecuting;
 use crate::{errors::ContextType, wasm_vm::PluginInstruction};
+use crate::{os_input_output::OsApi, update_state, AppState};
 use crate::{AppInstruction, SenderWithContext, OPENCALLS};
 
 struct InputHandler {
@@ -45,6 +44,9 @@ impl InputHandler {
         self.send_app_instructions.update(err_ctx);
         self.send_screen_instructions.update(err_ctx);
         loop {
+            update_state(&self.send_app_instructions, |_| AppState {
+                input_mode: self.mode,
+            });
             match self.mode {
                 InputMode::Normal => self.read_normal_mode(),
                 InputMode::Command => self.read_command_mode(false),
@@ -112,12 +114,10 @@ impl InputHandler {
                     // multiple commands. If we're already in persistent mode, it'll return us to normal mode.
                     match self.mode {
                         InputMode::Command => self.mode = InputMode::CommandPersistent,
-                        InputMode::CommandPersistent => {
+                        InputMode::CommandPersistent => self.mode = InputMode::Normal,
-                            self.mode = InputMode::Normal;
-                            return;
-                        }
                         _ => panic!(),
                     }
+                    return;
                 }
                 [27] => {
                     // Esc
@@ -262,7 +262,7 @@ impl InputHandler {
                     self.command_is_executing.wait_until_pane_is_closed();
                 }
                 //@@@khs26 Write this to the powerbar?
-                _ => {}
+                _ => continue,
             }
 
             if self.mode == InputMode::Command {
@@ -299,7 +299,7 @@ impl InputHandler {
 ///   normal mode
 /// - Exiting means that we should start the shutdown process for mosaic or the given
 ///   input handler
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub enum InputMode {
     Normal,
     Command,
@@ -307,6 +307,36 @@ pub enum InputMode {
     Exiting,
 }
 
+// FIXME: This should be auto-generated from the soon-to-be-added `get_default_keybinds`
+pub fn get_help(mode: &InputMode) -> Vec<String> {
+    let command_help = vec![
+        "<n/b/z> Split".into(),
+        "<j/k/h/l> Resize".into(),
+        "<p> Focus Next".into(),
+        "<x> Close Pane".into(),
+        "<q> Quit".into(),
+        "<PgUp/PgDown> Scroll".into(),
+        "<1> New Tab".into(),
+        "<2> Next Tab".into(),
+        "<3> Last Tab".into(),
+    ];
+    match mode {
+        InputMode::Normal => vec!["<Ctrl-g> Command Mode".into()],
+        InputMode::Command => [
+            vec![
+                "<Ctrl-g> Persistent Mode".into(),
+                "<ESC> Normal Mode".into(),
+            ],
+            command_help,
+        ]
+        .concat(),
+        InputMode::CommandPersistent => {
+            [vec!["<Ctrl-g/ESC> Normal Mode".into()], command_help].concat()
+        }
+        InputMode::Exiting => vec!["Bye from Mosaic!".into()],
+    }
+}
+
 /// Entry point to the module that instantiates a new InputHandler and calls its
 /// reading loop
 pub fn input_loop(

src/main.rs

@@ -16,14 +16,15 @@ mod utils;
 
 mod wasm_vm;
 
-use std::cell::RefCell;
 use std::collections::HashMap;
 use std::io::Write;
 use std::os::unix::net::UnixStream;
 use std::path::PathBuf;
 use std::sync::mpsc::{channel, sync_channel, Receiver, SendError, Sender, SyncSender};
 use std::thread;
+use std::{cell::RefCell, sync::mpsc::TrySendError};
 
+use input::InputMode;
 use panes::PaneId;
 use serde::{Deserialize, Serialize};
 use structopt::StructOpt;
@@ -85,6 +86,14 @@ impl<T: Clone> SenderWithContext<T> {
         }
     }
 
+    pub fn try_send(&self, event: T) -> Result<(), TrySendError<(T, ErrorContext)>> {
+        if let SenderType::SyncSender(ref s) = self.sender {
+            s.try_send((event, self.err_ctx))
+        } else {
+            panic!("try_send can only be called on SyncSenders!")
+        }
+    }
+
     pub fn update(&mut self, new_ctx: ErrorContext) {
         self.err_ctx = new_ctx;
     }
@@ -125,13 +134,44 @@ pub fn main() {
     }
 }
 
+// FIXME: It would be good to add some more things to this over time
+#[derive(Debug, Clone)]
+pub struct AppState {
+    pub input_mode: InputMode,
+}
+
+impl Default for AppState {
+    fn default() -> Self {
+        Self {
+            input_mode: InputMode::Normal,
+        }
+    }
+}
+
+// FIXME: Make this a method on the big `Communication` struct, so that app_tx can be extracted
+// from self instead of being explicitly passed here
+pub fn update_state(
+    app_tx: &SenderWithContext<AppInstruction>,
+    update_fn: impl FnOnce(AppState) -> AppState,
+) {
+    let (state_tx, state_rx) = channel();
+
+    drop(app_tx.send(AppInstruction::GetState(state_tx)));
+    let state = state_rx.recv().unwrap();
+
+    drop(app_tx.send(AppInstruction::SetState(update_fn(state))))
+}
+
 #[derive(Clone)]
 pub enum AppInstruction {
+    GetState(Sender<AppState>),
+    SetState(AppState),
     Exit,
     Error(String),
 }
 
 pub fn start(mut os_input: Box<dyn OsApi>, opts: CliArgs) {
+    let mut app_state = AppState::default();
     let mut active_threads = vec![];
 
     let command_is_executing = CommandIsExecuting::new();
@@ -399,6 +439,7 @@ pub fn start(mut os_input: Box<dyn OsApi>, opts: CliArgs) {
             .spawn({
                 let mut send_pty_instructions = send_pty_instructions.clone();
                 let mut send_screen_instructions = send_screen_instructions.clone();
+                let mut send_app_instructions = send_app_instructions.clone();
 
                 move || {
                     let store = Store::default();
@@ -413,6 +454,7 @@ pub fn start(mut os_input: Box<dyn OsApi>, opts: CliArgs) {
                         err_ctx.add_call(ContextType::Plugin(PluginContext::from(&event)));
                         send_screen_instructions.update(err_ctx);
                         send_pty_instructions.update(err_ctx);
+                        send_app_instructions.update(err_ctx);
                         match event {
                             PluginInstruction::Load(pid_tx, path) => {
                                 // FIXME: Cache this compiled module on disk. I could use `(de)serialize_to_file()` for that
@@ -441,6 +483,7 @@ pub fn start(mut os_input: Box<dyn OsApi>, opts: CliArgs) {
                                     plugin_id,
                                     send_pty_instructions: send_pty_instructions.clone(),
                                     send_screen_instructions: send_screen_instructions.clone(),
+                                    send_app_instructions: send_app_instructions.clone(),
                                     wasi_env,
                                 };
 
@@ -602,6 +645,8 @@ pub fn start(mut os_input: Box<dyn OsApi>, opts: CliArgs) {
         send_screen_instructions.update(err_ctx);
         send_pty_instructions.update(err_ctx);
         match app_instruction {
+            AppInstruction::GetState(state_tx) => drop(state_tx.send(app_state.clone())),
+            AppInstruction::SetState(state) => app_state = state,
             AppInstruction::Exit => {
                 let _ = send_screen_instructions.send(ScreenInstruction::Quit);
                 let _ = send_pty_instructions.send(PtyInstruction::Quit);

src/wasm_vm.rs

@@ -1,8 +1,14 @@
-use std::{path::PathBuf, sync::mpsc::Sender};
+use std::{
+    path::PathBuf,
+    sync::mpsc::{channel, Sender},
+};
 use wasmer::{imports, Function, ImportObject, Store, WasmerEnv};
 use wasmer_wasi::WasiEnv;
 
-use crate::{panes::PaneId, pty_bus::PtyInstruction, screen::ScreenInstruction, SenderWithContext};
+use crate::{
+    input::get_help, panes::PaneId, pty_bus::PtyInstruction, screen::ScreenInstruction,
+    AppInstruction, SenderWithContext,
+};
 
 #[derive(Clone, Debug)]
 pub enum PluginInstruction {
@@ -18,6 +24,7 @@ pub enum PluginInstruction {
 pub struct PluginEnv {
     pub plugin_id: u32,
     pub send_screen_instructions: SenderWithContext<ScreenInstruction>,
+    pub send_app_instructions: SenderWithContext<AppInstruction>,
     pub send_pty_instructions: SenderWithContext<PtyInstruction>, // FIXME: This should be a big bundle of all of the channels
     pub wasi_env: WasiEnv,
 }
@@ -29,6 +36,7 @@ pub fn mosaic_imports(store: &Store, plugin_env: &PluginEnv) -> ImportObject {
         "mosaic" => {
             "host_open_file" => Function::new_native_with_env(store, plugin_env.clone(), host_open_file),
             "host_set_selectable" => Function::new_native_with_env(store, plugin_env.clone(), host_set_selectable),
+            "host_get_help" => Function::new_native_with_env(store, plugin_env.clone(), host_get_help),
         }
     }
 }
@@ -54,6 +62,21 @@ fn host_set_selectable(plugin_env: &PluginEnv, selectable: i32) {
         .unwrap()
 }
 
+fn host_get_help(plugin_env: &PluginEnv) {
+    let (state_tx, state_rx) = channel();
+    // FIXME: If I changed the application so that threads were sent the termination
+    // signal and joined one at a time, there would be an order to shutdown, so I
+    // could get rid of this .is_ok() check and the .try_send()
+    if plugin_env
+        .send_app_instructions
+        .try_send(AppInstruction::GetState(state_tx))
+        .is_ok()
+    {
+        let help = get_help(&state_rx.recv().unwrap().input_mode);
+        wasi_write_string(&plugin_env.wasi_env, &serde_json::to_string(&help).unwrap());
+    }
+}
+
 // Helper Functions ---------------------------------------------------------------------------------------------------
 
 // FIXME: Unwrap city