feat(plugin): implementing the method to generate the invoice to put inside the coffee conf

This commit assume that the developer of the plugins is running
a lightning node and is allow to receive payments with lightning.

So this is a helper method that help you to generate an BOLT 12
invoice without understand how to do it :)

Signed-off-by: Vincenzo Palazzo <[email protected]>

Author: vincenzopalazzo

coffee_plugin/src/plugin/plugin_mod.rs

@@ -2,6 +2,7 @@
 //! Coffee as a core lightning plugin.
 use std::fmt::Display;
 
+use serde::{Deserialize, Serialize};
 use serde_json::{json, Value};
 use tokio::runtime::Runtime;
 
@@ -124,3 +125,28 @@ fn coffee_remote(plugin: &mut Plugin<State>, request: Value) -> Result<Value, Pl
         .map_err(from)?;
     Ok(json!({}))
 }
+
+#[rpc_method(
+    rpc_name = "coffee_generate_tip",
+    description = "Generate the BOLT 12 to add inside a plugin configuration to receive donation"
+)]
+fn coffee_generate_tip(plugin: &mut Plugin<State>, request: Value) -> Result<Value, PluginError> {
+    let runtime = Runtime::new().unwrap();
+    let coffee = plugin.state.coffee();
+
+    #[derive(Serialize, Deserialize, Debug)]
+    struct Offer {
+        pub bolt12: String,
+    }
+
+    let offer = runtime
+        .block_on(async {
+            let mut coffee = coffee.lock().unwrap();
+            coffee.cln::<Value, Offer>("offer", json!({
+                "amount": "any",
+                "description": "Generating BOLT 12 for coffee tips regarding the plugin ...",
+            })).await
+        })
+        .map_err(from)?;
+    Ok(serde_json::to_value(offer)?)
+}