Light Client Support for Memos (#1)

* Dependency to note-spending-v6 branch

* Spend funds

* Add outgoing memos

* cleanup

* Incoming memo support

* Refactor to LightClient

* Abstract grpc client creation

* TLS example

* Add address command

* Run blocking IO

* Store memos in wallet Tx

* Fetch the full txns only for new transactions

* Comments

* Filter first

* More comments

* Add commands

rust-lightclient/src/commands.rs

@@ -0,0 +1,80 @@
+use std::collections::HashMap;
+
+use crate::LightClient;
+
+pub trait Command {
+    fn help(&self);
+
+    fn short_help(&self) -> String;
+
+    fn exec(&self, args: &[String], lightclient: &LightClient);
+}
+
+struct SyncCommand {}
+
+impl Command for SyncCommand {
+    fn help(&self) {
+        println!("Type sync for syncing");
+    }
+
+    fn short_help(&self) -> String {
+        "Download CompactBlocks and sync to the server".to_string()
+    }
+
+    fn exec(&self, args: &[String], lightclient: &LightClient) {
+        lightclient.do_sync();
+    }
+}
+
+struct HelpCommand {}
+
+impl Command for HelpCommand {
+    fn help(&self) {
+        println!("Lists all available commands");
+    }
+
+    fn short_help(&self) -> String {
+        "Lists all available commands".to_string()
+    }
+
+    fn exec(&self, args: &[String], _: &LightClient) {
+        // Print a list of all commands
+        get_commands().iter().for_each(| (cmd, obj) | {
+            println!("{} - {}", cmd, obj.short_help());
+        });
+    }
+}
+
+struct AddressCommand {}
+impl Command for AddressCommand {
+    fn help(&self) {
+        println!("Show my addresses");
+    }
+
+    fn short_help(&self) -> String {
+        "List all current addresses".to_string()
+    }
+
+    fn exec(&self, args: &[String], lightclient: &LightClient) {
+        lightclient.do_address();
+    }
+}
+
+pub fn get_commands() -> Box<HashMap<String, Box<dyn Command>>> {
+    let mut map: HashMap<String, Box<dyn Command>> = HashMap::new();
+
+    map.insert("sync".to_string(),      Box::new(SyncCommand{}));
+    map.insert("help".to_string(),      Box::new(HelpCommand{}));
+    map.insert("address".to_string(),   Box::new(AddressCommand{}));
+
+    Box::new(map)
+}
+
+pub fn do_user_command(cmd: String, lightclient: &LightClient) {
+    match get_commands().get(&cmd) {
+        Some(cmd) => cmd.exec(&[], lightclient),
+        None      => {
+            println!("Unknown command : {}. Type 'help' for a list of commands", cmd);
+        }
+    }
+}