chore(example): add example in progress (#271)

Signed-off-by: jokemanfire <hu.dingyang@zte.com.cn>

examples/servers/src/common/progress_demo.rs

@@ -0,0 +1,132 @@
+use std::{
+    io,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+use futures::Stream;
+use rmcp::{
+    ErrorData as McpError, RoleServer, ServerHandler, handler::server::tool::ToolRouter, model::*,
+    service::RequestContext, tool, tool_handler, tool_router,
+};
+use serde_json::json;
+use tokio_stream::StreamExt;
+use tracing::debug;
+
+// a Stream data source that generates data in chunks
+#[derive(Clone)]
+struct StreamDataSource {
+    data: Vec<u8>,
+    chunk_size: usize,
+    position: usize,
+}
+
+impl StreamDataSource {
+    pub fn new(data: Vec<u8>, chunk_size: usize) -> Self {
+        Self {
+            data,
+            chunk_size,
+            position: 0,
+        }
+    }
+    pub fn from_text(text: &str) -> Self {
+        Self::new(text.as_bytes().to_vec(), 1)
+    }
+}
+
+impl Stream for StreamDataSource {
+    type Item = Result<Vec<u8>, io::Error>;
+
+    fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.get_mut();
+        if this.position >= this.data.len() {
+            return Poll::Ready(None);
+        }
+
+        let start = this.position;
+        let end = (start + this.chunk_size).min(this.data.len());
+        let chunk = this.data[start..end].to_vec();
+        this.position = end;
+        Poll::Ready(Some(Ok(chunk)))
+    }
+}
+
+#[derive(Clone)]
+pub struct ProgressDemo {
+    data_source: StreamDataSource,
+    tool_router: ToolRouter<Self>,
+}
+
+#[tool_router]
+impl ProgressDemo {
+    #[allow(dead_code)]
+    pub fn new() -> Self {
+        Self {
+            tool_router: Self::tool_router(),
+            data_source: StreamDataSource::from_text("Hello, world!"),
+        }
+    }
+    #[tool(description = "Process data stream with progress updates")]
+    async fn stream_processor(
+        &self,
+        ctx: RequestContext<RoleServer>,
+    ) -> Result<CallToolResult, McpError> {
+        let mut counter = 0;
+
+        let mut data_source = self.data_source.clone();
+        loop {
+            let chunk = data_source.next().await;
+            if chunk.is_none() {
+                break;
+            }
+
+            let chunk = chunk.unwrap().unwrap();
+            let chunk_str = String::from_utf8_lossy(&chunk);
+            counter += 1;
+            // create progress notification param
+            let progress_param = ProgressNotificationParam {
+                progress_token: ProgressToken(NumberOrString::Number(counter)),
+                progress: counter as f64,
+                total: None,
+                message: Some(chunk_str.to_string()),
+            };
+
+            match ctx.peer.notify_progress(progress_param).await {
+                Ok(_) => {
+                    debug!("Processed record: {}", chunk_str);
+                }
+                Err(e) => {
+                    return Err(McpError::internal_error(
+                        format!("Failed to notify progress: {}", e),
+                        Some(json!({
+                            "record": chunk_str,
+                            "progress": counter,
+                            "error": e.to_string()
+                        })),
+                    ));
+                }
+            }
+        }
+
+        Ok(CallToolResult::success(vec![Content::text(format!(
+            "Processed {} records successfully",
+            counter
+        ))]))
+    }
+}
+
+#[tool_handler]
+impl ServerHandler for ProgressDemo {
+    fn get_info(&self) -> ServerInfo {
+        ServerInfo {
+            protocol_version: ProtocolVersion::V_2024_11_05,
+            capabilities: ServerCapabilities::builder().enable_tools().build(),
+            server_info: Implementation::from_build_env(),
+            instructions: Some(
+                "This server demonstrates progress notifications during long-running operations. \
+                 Use the tools to see real-time progress updates for batch processing"
+                    .to_string(),
+            ),
+        }
+    }
+}