codex/codex-rs/rmcp-client/src/http_client_adapter_tests.rs

use std::io::ErrorKind;

use pretty_assertions::assert_eq;

use super::SseEventSizeLimit;

#[test]
fn lf_terminators_reset_the_event_limit() {
    let mut limit = SseEventSizeLimit::new(Some(8));

    limit
        .observe(b"data: a\n\ndata: b\n\n")
        .expect("LF-terminated events must have independent size limits");

    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 0));
}

#[test]
fn carriage_return_terminators_reset_the_event_limit() {
    let mut limit = SseEventSizeLimit::new(Some(8));

    limit
        .observe(b"data: a\r\rdata: b\r\r")
        .expect("CR-terminated events must have independent size limits");

    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 0));
}

#[test]
fn crlf_terminators_split_across_chunks_reset_the_event_limit() {
    let mut limit = SseEventSizeLimit::new(Some(8));

    limit
        .observe(b"data: a\r")
        .expect("a CR must finish the first event field");
    limit
        .observe(b"\n\r")
        .expect("a split CRLF must not finish another field");
    limit
        .observe(b"\ndata: b\r")
        .expect("the blank CRLF must reset the first event");
    limit
        .observe(b"\n\r\n")
        .expect("the second split CRLF event must remain within the limit");

    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 0));
}

#[test]
fn event_at_the_exact_size_limit_is_accepted() {
    let mut limit = SseEventSizeLimit::new(Some(9));

    limit
        .observe(b"data: ab\n\n")
        .expect("an event at the exact limit must be accepted");

    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 0));
}

#[test]
fn completed_keepalive_comments_do_not_accumulate() {
    let mut limit = SseEventSizeLimit::new(Some(6));

    limit
        .observe(&b": ping\n".repeat(/*n*/ 64))
        .expect("completed keepalive comments must not accumulate");

    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 0));
}

#[test]
fn split_keepalive_comments_are_discarded_only_when_complete() {
    let mut limit = SseEventSizeLimit::new(Some(6));

    limit
        .observe(b": pi")
        .expect("an incomplete comment within the limit must be retained");
    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 4));

    limit
        .observe(b"ng\n: ping\n")
        .expect("only completed comments may be excluded from the limit");

    assert_eq!((limit.retained_bytes, limit.line_bytes), (0, 0));
}

#[test]
fn comments_do_not_reset_accumulated_event_data() {
    let mut limit = SseEventSizeLimit::new(Some(14));

    limit
        .observe(b"data: a\n")
        .expect("the first data field must fit");
    limit
        .observe(b": ping\n")
        .expect("a completed comment must not count as event data");

    let error = limit
        .observe(b"data: b\n")
        .expect_err("a comment must not reset previously retained data");

    assert_eq!(
        (error.kind(), error.to_string()),
        (
            ErrorKind::InvalidData,
            "MCP response body exceeds 14 bytes".to_string(),
        )
    );
}

#[test]
fn an_unterminated_comment_remains_size_limited() {
    let mut limit = SseEventSizeLimit::new(Some(6));

    limit
        .observe(b": ping")
        .expect("a comment at the exact limit must be accepted");

    let error = limit
        .observe(b"!")
        .expect_err("an unterminated comment must not bypass the limit");

    assert_eq!(
        (error.kind(), error.to_string()),
        (
            ErrorKind::InvalidData,
            "MCP response body exceeds 6 bytes".to_string(),
        )
    );
}

#[test]
fn multiline_data_counts_parser_inserted_newlines() {
    let mut limit = SseEventSizeLimit::new(Some(18));

    let error = limit
        .observe(b"data: aaa\ndata: bbb\n\n")
        .expect_err("joined multiline event data must remain size limited");

    assert_eq!(
        (error.kind(), error.to_string()),
        (
            ErrorKind::InvalidData,
            "MCP response body exceeds 18 bytes".to_string(),
        )
    );
}

#[test]
fn legacy_sse_streams_remain_unlimited() {
    let mut limit = SseEventSizeLimit::new(/*maximum_bytes*/ None);

    limit
        .observe(&[b'x'; 128])
        .expect("legacy SSE streams must not gain a message limit");

    assert_eq!(
        (
            limit.retained_bytes,
            limit.line_bytes,
            limit.line_is_comment,
            limit.previous_was_carriage_return,
            limit.failed,
        ),
        (0, 0, false, false, false)
    );
}

#[test]
fn rejected_events_remain_rejected() {
    let mut limit = SseEventSizeLimit::new(Some(8));

    limit
        .observe(b"data: abc")
        .expect_err("an oversized event must be rejected");

    let error = limit
        .observe(b"")
        .expect_err("a rejected event must not be resumed");

    assert_eq!(
        (error.kind(), error.to_string()),
        (
            ErrorKind::InvalidData,
            "oversized MCP SSE event was already rejected".to_string(),
        )
    );
}

#[test]
fn size_accounting_saturates_without_overflow() {
    let mut limit = SseEventSizeLimit::new(Some(usize::MAX - 1));
    limit.retained_bytes = usize::MAX - 2;
    limit.line_bytes = 1;

    let error = limit
        .observe(b"x")
        .expect_err("saturating counts must still reject an oversized event");

    assert_eq!((error.kind(), limit.failed), (ErrorKind::InvalidData, true));
}