logup 0.1.0

Logup is a UNIX-style command that can be used to pipe stdout logs to location on disk or in the cloud without the need of an agent, logrotate, systemd or other configuration files
Documentation 
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use crate::writer::AsyncLogWriter;
use async_trait::async_trait;
use mem::take;
use std::cmp::min;
use std::mem;
use std::time::SystemTime;

pub struct LinesWriter<T: AsyncLogWriter> {
    inner: T,
    buf: Vec<u8>,
    max_line_size: usize,
}

impl<T: AsyncLogWriter> LinesWriter<T> {
    pub fn new(inner: T, max_line_size: usize) -> Self {
        Self {
            inner,
            buf: Vec::new(),
            max_line_size,
        }
    }
}

#[async_trait]
impl<T: AsyncLogWriter + Send> AsyncLogWriter for LinesWriter<T> {
    async fn write_logs(&mut self, time: SystemTime, buf: &[u8]) -> std::io::Result<()> {
        let mut buf = buf;
        while !buf.is_empty() {
            if let Some(pos) = buf.iter().position(|&b| b == b'\n') {
                let len = min(self.buf.len() + pos + 1, self.max_line_size) - self.buf.len();
                let line = &buf[..len];
                if !self.buf.is_empty() {
                    let mut newbuf = take(&mut self.buf);
                    newbuf.extend_from_slice(line); // concatenate to previous buffer
                    self.buf.clear(); // clear before the next line could fail
                    self.inner.write_logs(time, newbuf.as_slice()).await?;
                } else {
                    self.inner.write_logs(time, line).await?;
                }
                buf = &buf[len..];
            } else {
                // no newline found, buffer
                let len = min(self.buf.len() + buf.len(), self.max_line_size) - self.buf.len();
                buf = &buf[..len];
                self.buf.extend_from_slice(buf);
                buf = &buf[len..];
            }
        }
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use crate::writer::{AsyncLogWriter, MockAsyncLogWriter};
    use crate::writer_lines::LinesWriter;
    use mockall::predicate::eq;
    use std::time::SystemTime;

    #[tokio::test]
    async fn split_lines1() {
        let mut mock = MockAsyncLogWriter::new();
        let time = SystemTime::now();

        mock.expect_write_logs()
            .with(eq(time), eq(b"line1\n".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"line2\n".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"line3extra\n".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"veryveryveryver".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"yverylonglonglo".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"ngline\n".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs().times(0);

        let mut writer = LinesWriter::new(mock, 15);
        writer
            .write_logs(time, b"line1\nline2\nline3")
            .await
            .unwrap();
        writer
            .write_logs(
                time,
                b"extra\nveryveryveryveryverylonglonglongline\nbuffered",
            )
            .await
            .unwrap();
    }

    #[tokio::test]
    async fn split_lines2() {
        let mut mock = MockAsyncLogWriter::new();
        let time = SystemTime::now();

        mock.expect_write_logs()
            .with(eq(time), eq(b"foof".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"oo\n".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"barb".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs()
            .with(eq(time), eq(b"ar\n".to_vec()))
            .times(1)
            .returning(|_, _| Ok(()));
        mock.expect_write_logs().times(0);

        let mut writer = LinesWriter::new(mock, 4);
        writer.write_logs(time, b"foofoo\nbarbar\n").await.unwrap();
    }
}