/// Boundary mode - where chunks can be split.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Boundary {
    /// Never split inside a Record (sessions)
    Record,
    /// Split on markdown ATX headings (documentation)
    Heading,
}

/// Trigger for flushing a chunk.
#[derive(Clone, Debug)]
pub enum FlushTrigger {
    /// Flush when this many tokens is reached
    Tokens(usize),
    // OrIdle(Duration) will land with the first streaming source.
    // Carrying the enum now means that change is one variant, not a signature change
    // threaded through the loop.
}

/// Chunking policy.
#[derive(Clone, Debug)]
pub struct ChunkPolicy {
    /// Maximum tokens per chunk (default 5000 - GRU-Mem paper default)
    pub max_tokens: usize,
    /// Boundary mode - never split inside a Record
    pub split_on: Boundary,
    /// Flush trigger
    pub flush: FlushTrigger,
}

impl Default for ChunkPolicy {
    fn default() -> Self {
        ChunkPolicy {
            max_tokens: 5000,
            split_on: Boundary::Record,
            flush: FlushTrigger::Tokens(5000),
        }
    }
}

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

    #[test]
    fn test_default_chunk_policy() {
        let policy = ChunkPolicy::default();
        assert_eq!(policy.max_tokens, 5000);
        assert_eq!(policy.split_on, Boundary::Record);
    }
}