First, naive and wrong attempt, have to add interval later on

4-grow-only-counter/src/main.rs

@@ -2,6 +2,9 @@ use std::io::{self, BufRead, Write};
 
 use serde::{Deserialize, Serialize};
 
+const SEQ_KV: &str = "seq-kv";
+const KEY: &str = "counter";
+
 #[derive(Serialize, Deserialize, Debug)]
 struct Message {
 	src: String,
@@ -27,11 +30,12 @@ enum Body {
 		in_reply_to: u64,
 	},
 	Read {
-		msg_id: u64,
+		msg_id: Option<u64>,
+		key: Option<String>,
 	},
 	ReadOk {
+		in_reply_to: Option<u64>,
 		value: u64,
-		in_reply_to: u64,
 	},
 	Add {
 		msg_id: u64,
@@ -40,7 +44,6 @@ enum Body {
 	AddOk {
 		in_reply_to: u64,
 	},
-	//SEQ-KV
 	Write {
 		msg_id: u64,
 		key: String,
@@ -49,6 +52,16 @@ enum Body {
 	WriteOk {
 		in_reply_to: u64,
 	},
+	Cas {
+		msg_id: u64,
+		key: String,
+		from: u64,
+		to: u64,
+	},
+	CasOk {
+		msg_id: u64,
+		in_reply_to: u64,
+	},
 }
 
 fn main() {
@@ -57,15 +70,39 @@ fn main() {
 	let mut stderr = io::stderr();
 
 	let mut id = String::new();
+	let mut counter = 0;
+	let mut tmp_counter = 0;
 
 	for line in stdin.lock().lines() {
+		let input = serde_json::from_str::<Message>(&line.as_ref().unwrap());
+
+		if let Err(e) = input {
+			writeln!(stderr, "Error: {:?}", e).unwrap();
+			stderr.flush().unwrap();
+			continue;
+		}
 		let input: Message = serde_json::from_str(&line.unwrap()).unwrap();
+
 		match input.body {
-			Body::Error { text, .. } => {
-				let output_json = serde_json::to_string(&text).unwrap();
-				writeln!(stderr, "{}", output_json).unwrap();
-				stdout.flush().unwrap();
-			}
+			Body::Error { code, .. } => match code {
+				22 => {
+					let output = Message {
+						src: id.clone(),
+						dest: SEQ_KV.to_string(),
+						body: Body::Read {
+							msg_id: Some(2),
+							key: Some(KEY.to_string()),
+						},
+					};
+					let output_json = serde_json::to_string(&output).unwrap();
+					writeln!(stdout, "{}", output_json).unwrap();
+					stdout.flush().unwrap();
+				}
+				_ => {
+					writeln!(stderr, "Error: {:?}", input).unwrap();
+					stderr.flush().unwrap();
+				}
+			},
 			Body::Init {
 				msg_id, node_id, ..
 			} => {
@@ -82,31 +119,47 @@ fn main() {
 
 				let output = Message {
 					src: id.clone(),
-					dest: "seq-kv".to_string(),
+					dest: SEQ_KV.to_string(),
 					body: Body::Write {
-						msg_id: 1,
-						key: "TEST".to_string(),
-						value: 42,
+						msg_id,
+						key: KEY.to_string(),
+						value: counter,
 					},
 				};
 				let output_json = serde_json::to_string(&output).unwrap();
 				writeln!(stdout, "{}", output_json).unwrap();
 				stdout.flush().unwrap();
 			}
-			Body::Read { msg_id } => {
+			Body::Read { msg_id, .. } => {
 				let output = Message {
 					src: id.clone(),
 					dest: input.src,
 					body: Body::ReadOk {
 						in_reply_to: msg_id,
-						value: 42,
+						value: counter,
 					},
 				};
 				let output_json = serde_json::to_string(&output).unwrap();
 				writeln!(stdout, "{}", output_json).unwrap();
+
 				stdout.flush().unwrap();
 			}
-			Body::Add { msg_id, .. } => {
+			Body::Add { msg_id, delta } => {
+				tmp_counter += delta;
+
+				let output = Message {
+					src: id.clone(),
+					dest: SEQ_KV.to_string(),
+					body: Body::Cas {
+						msg_id,
+						key: KEY.to_string(),
+						from: counter,
+						to: tmp_counter,
+					},
+				};
+				let output_json = serde_json::to_string(&output).unwrap();
+				writeln!(stdout, "{}", output_json).unwrap();
+
 				let output = Message {
 					src: id.clone(),
 					dest: input.src,
@@ -121,6 +174,15 @@ fn main() {
 			Body::WriteOk { .. } => {
 				//
 			}
+			Body::AddOk { .. } => {
+				//
+			}
+			Body::CasOk { .. } => {
+				counter = tmp_counter;
+			}
+			Body::ReadOk { value, .. } => {
+				counter = value;
+			}
 			_ => println!("Unhandled message: {:?}", input),
 		}
 	}