add problem 05

2026-07-12 19:59:04 +02:00
parent 518d68a1d3
commit 9ba67af68a
3 changed files with 364 additions and 0 deletions
@@ -0,0 +1,131 @@
+use anyhow::bail;
+use tokio::{
+    io::{AsyncReadExt, AsyncWriteExt, Result},
+    net::TcpStream,
+};
+
+const TONYS_ADDRESS: &str = "7YWHMfk9JZe0LM0g1ZauHuiSxhI";
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let listener = tokio::net::TcpListener::bind("0.0.0.0:10000").await?;
+
+    loop {
+        let (socket, _) = listener.accept().await?;
+        tokio::spawn(async move {
+            match handle_connection(socket).await {
+                Ok(_) => (),
+                Err(err) => {
+                    dbg!(err);
+                }
+            }
+        });
+    }
+}
+
+async fn handle_connection(socket: TcpStream) -> anyhow::Result<()> {
+    let (mut downstream_reader, mut downstream_writer) = tokio::io::split(socket);
+
+    let upstream = tokio::net::TcpStream::connect("chat.protohackers.com:16963").await?;
+    let (mut upstream_reader, mut upstream_writer) = tokio::io::split(upstream);
+
+    let mut downstream_read_buffer = Vec::with_capacity(1024);
+    let mut upstream_read_buffer = Vec::with_capacity(1024);
+
+    loop {
+        tokio::select! {
+            read_amount = read_to_buffer(&mut upstream_reader, &mut upstream_read_buffer) => {
+                match read_amount {
+                    Ok(_) => (),
+                    Err(_) => {
+                        return Ok(());
+                    }
+                };
+
+                let message = match handle_message(&mut upstream_read_buffer) {
+                    Ok(s) => s,
+                    Err(_) => continue,
+                };
+
+                downstream_writer.write_all(&message.into_bytes()).await?;
+            }
+            // receive from downstream, send to upstream
+            read_amount = read_to_buffer(&mut downstream_reader, &mut downstream_read_buffer) => {
+                match read_amount {
+                    Ok(_) => (),
+                    Err(_) => {
+                        return Ok(());
+                    }
+                };
+
+                let message = match handle_message(&mut downstream_read_buffer) {
+                    Ok(s) => s,
+                    Err(_) => continue,
+                };
+
+                upstream_writer.write_all(&message.into_bytes()).await?;
+
+            }
+
+        };
+    }
+}
+
+fn find_next_newline(read_buffer: &[u8]) -> Option<usize> {
+    read_buffer.iter().position(|c| *c == b'\n')
+}
+
+async fn read_to_buffer(
+    reader: &mut tokio::io::ReadHalf<TcpStream>,
+    read_buffer: &mut Vec<u8>,
+) -> anyhow::Result<usize> {
+    let mut read_amount = 0;
+
+    while !read_buffer.contains(&b'\n') {
+        read_amount += reader.read_buf(read_buffer).await?;
+        if read_amount == 0 {
+            bail!("user disconnected");
+        }
+    }
+    Ok(read_amount)
+}
+
+fn replace_boguscoin_addresses(s: String) -> String {
+    let trimmed = s.trim_end_matches('\n');
+    let mut result = String::new();
+
+    let mut words = trimmed.split(' ').peekable();
+
+    while let Some(word) = words.next() {
+        if is_boguscoin_addres(word) {
+            result.push_str(TONYS_ADDRESS);
+        } else {
+            result.push_str(word);
+        }
+        if words.peek().is_some() {
+            result.push(' ');
+        }
+    }
+
+    result.push('\n');
+    result
+}
+
+fn is_boguscoin_addres(s: &str) -> bool {
+    s.starts_with('7')
+        && (26..=35).contains(&s.len())
+        && s.chars().all(|c| c.is_ascii_alphanumeric())
+}
+
+fn handle_message(read_buffer: &mut Vec<u8>) -> anyhow::Result<String> {
+    let newline = match find_next_newline(read_buffer) {
+        Some(idx) => idx,
+        None => bail!("continue"),
+    };
+    let before_newline = read_buffer.drain(0..=newline).collect();
+
+    let message = String::from_utf8(before_newline)?;
+    let message = replace_boguscoin_addresses(message);
+
+    Ok(message)
+}