y-octo 0.0.3

High-performance and thread-safe CRDT implementation compatible with Yjs
Documentation 
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use nom::{Parser, multi::count};

use super::*;

const NULL_STR: &str = "null";

#[derive(Debug, Clone, PartialEq)]
#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
pub struct AwarenessState {
    #[cfg_attr(test, proptest(strategy = "0..u32::MAX as u64"))]
    pub(crate) clock: u64,
    // content is usually a json
    pub(crate) content: String,
}

impl AwarenessState {
    pub fn new(clock: u64, content: String) -> Self {
        AwarenessState { clock, content }
    }

    pub fn clock(&self) -> u64 {
        self.clock
    }

    pub fn content(&self) -> &str {
        &self.content
    }

    pub fn is_deleted(&self) -> bool {
        self.content == NULL_STR
    }

    pub(crate) fn add_clock(&mut self) {
        self.clock += 1;
    }

    pub(crate) fn set_clock(&mut self, clock: u64) {
        self.clock = clock;
    }

    pub fn set_content(&mut self, content: String) {
        self.add_clock();
        self.content = content;
    }

    pub fn delete(&mut self) {
        self.set_content(NULL_STR.to_string());
    }
}

impl Default for AwarenessState {
    fn default() -> Self {
        AwarenessState {
            clock: 0,
            content: NULL_STR.to_string(),
        }
    }
}

fn read_awareness_state(input: &[u8]) -> IResult<&[u8], (u64, AwarenessState)> {
    let (tail, client_id) = read_var_u64(input)?;
    let (tail, clock) = read_var_u64(tail)?;
    let (tail, content) = read_var_string(tail)?;

    Ok((tail, (client_id, AwarenessState { clock, content })))
}

fn write_awareness_state<W: Write>(buffer: &mut W, client_id: u64, state: &AwarenessState) -> Result<(), IoError> {
    write_var_u64(buffer, client_id)?;
    write_var_u64(buffer, state.clock)?;
    write_var_string(buffer, state.content.clone())?;

    Ok(())
}

pub type AwarenessStates = HashMap<u64, AwarenessState>;

pub fn read_awareness(input: &[u8]) -> IResult<&[u8], AwarenessStates> {
    let (tail, len) = read_var_u64(input)?;
    let (tail, messages) = count(read_awareness_state, len as usize).parse(tail)?;

    Ok((tail, messages.into_iter().collect()))
}

pub fn write_awareness<W: Write>(buffer: &mut W, clients: &AwarenessStates) -> Result<(), IoError> {
    write_var_u64(buffer, clients.len() as u64)?;

    for (client_id, state) in clients {
        write_awareness_state(buffer, *client_id, state)?;
    }

    Ok(())
}

// TODO(@darkskygit): impl reader/writer
// awareness state message
#[allow(dead_code)]
#[derive(Debug, PartialEq)]
pub struct AwarenessMessage {
    clients: AwarenessStates,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_awareness() {
        let input = [
            3, // count of state
            1, 5, 1, 1, // first state
            2, 10, 2, 2, 3, // second state
            5, 5, 5, 1, 2, 3, 4, 5, // third state
        ];

        let expected = HashMap::from([
            (1, AwarenessState::new(5, String::from_utf8(vec![1]).unwrap())),
            (2, AwarenessState::new(10, String::from_utf8(vec![2, 3]).unwrap())),
            (
                5,
                AwarenessState::new(5, String::from_utf8(vec![1, 2, 3, 4, 5]).unwrap()),
            ),
        ]);

        {
            let (tail, result) = read_awareness(&input).unwrap();
            assert!(tail.is_empty());
            assert_eq!(result, expected);
        }

        {
            let mut buffer = Vec::new();
            // hashmap has not a ordered keys, so buffer not equal each write
            // we need re-parse the buffer to check result
            write_awareness(&mut buffer, &expected).unwrap();
            let (tail, result) = read_awareness(&buffer).unwrap();
            assert!(tail.is_empty());
            assert_eq!(result, expected);
        }
    }
}