colla 0.2.0

Operational Transformation library for nested documents with text and rich-text
Documentation 
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use colla::{
    codec, Change, CodecError, InputLimits, MapChange, MapEntryChange, TextChange, TextOp, Value,
};

#[test]
fn value_and_change_roundtrip() {
    let limits = InputLimits::default();
    let value = Value::map([
        ("i", Value::int(i64::MIN)),
        ("f", Value::float(1.5).unwrap()),
        ("s", Value::string("atomic")),
        ("t", Value::text("editable")),
    ])
    .unwrap();
    let bytes = value.encode();
    assert_eq!(Value::decode(&bytes).unwrap(), value);
    assert_eq!(codec::decode_value(&bytes, &limits).unwrap(), value);

    let change = Change::from(
        MapChange::from_entries([(
            "t",
            MapEntryChange::Modify(Change::from(
                TextChange::from_ops(vec![TextOp::Retain(8), TextOp::Insert("!".into())]).unwrap(),
            )),
        )])
        .unwrap(),
    );
    let bytes = change.encode();
    assert_eq!(Change::decode(&bytes).unwrap(), change);
    assert_eq!(codec::decode_change(&bytes, &limits).unwrap(), change);
}

#[test]
fn decoder_rejects_noncanonical_change() {
    // TextChange([Retain(1), Retain(2)]) -- adjacent retains must merge.
    let bytes = [4, 2, 0, 1, 0, 2];
    assert!(Change::decode(&bytes).is_err());

    // RichTextChange([Insert(Text(""))]) -- snapshot decoding is tolerant,
    // but Change inserts must remain non-empty and canonical.
    let empty_rich_insert = [5, 1, 1, 0, 0, 0];
    assert!(matches!(
        Change::decode(&empty_rich_insert),
        Err(CodecError::NonCanonical {
            context: "RichTextChange",
            ..
        })
    ));
}

#[test]
fn decoder_rejects_adjacent_huge_lengths_without_panicking() {
    fn put_varint(mut value: u64, out: &mut Vec<u8>) {
        while value >= 0x80 {
            out.push((value as u8) | 0x80);
            value >>= 7;
        }
        out.push(value as u8);
    }

    // TextChange([Delete(usize::MAX), Delete(usize::MAX)]). Canonicalization
    // must reject adjacent deletes without first trying to add their lengths.
    let mut bytes = vec![4, 2, 2];
    put_varint(usize::MAX as u64, &mut bytes);
    bytes.push(2);
    put_varint(usize::MAX as u64, &mut bytes);

    assert!(Change::decode(&bytes).is_err());
}

#[test]
fn decoder_rejects_negative_zero() {
    let mut bytes = vec![4];
    bytes.extend_from_slice(&(-0.0f64).to_le_bytes());
    assert!(Value::decode(&bytes).is_err());
}

#[test]
fn input_limits_reject_large_logical_changes_only_when_decoding() {
    let change = Change::from(TextChange::from_ops(vec![TextOp::Delete(9)]).unwrap());
    let limits = InputLimits {
        max_sequence_len: 8,
        ..InputLimits::default()
    };

    assert!(Change::decode_with_limits(&change.encode(), &limits).is_err());
    assert_eq!(
        colla::transform_pair(&change, &Change::noop(), colla::TieBreak::LeftFirst).unwrap(),
        (change, Change::noop())
    );
}

#[test]
fn rich_text_decoder_enforces_snapshot_and_change_logical_lengths() {
    let limits = InputLimits {
        max_sequence_len: 2,
        ..InputLimits::default()
    };
    let snapshot = [7, 1, 0, 3, b'a', b'b', b'c', 0];
    let retain_change = [5, 1, 0, 3, 0];
    let insert_change = [5, 1, 1, 0, 3, b'a', b'b', b'c', 0];

    for result in [
        Value::decode_with_limits(&snapshot, &limits).map(|_| ()),
        Change::decode_with_limits(&retain_change, &limits).map(|_| ()),
        Change::decode_with_limits(&insert_change, &limits).map(|_| ()),
    ] {
        assert!(matches!(
            result,
            Err(CodecError::LimitExceeded {
                name: "sequence length",
                actual: 3,
                limit: 2,
            })
        ));
    }
}

#[test]
fn rich_text_decoder_normalizes_compatible_spans_and_rejects_invalid_text() {
    let adjacent_equal_attrs = [7, 2, 0, 1, b'a', 0, 0, 1, b'b', 0];
    let empty_text = [7, 1, 0, 0, 0];
    let invalid_utf8 = [7, 1, 0, 1, 0xff, 0];

    let adjacent = Value::decode(&adjacent_equal_attrs).unwrap();
    let rich = adjacent.as_rich_text().unwrap();
    assert_eq!(rich.span_count(), 1);
    assert_eq!(rich.to_plain_string(), "ab");

    let empty = Value::decode(&empty_text).unwrap();
    assert!(empty.as_rich_text().unwrap().is_empty());

    assert!(matches!(
        Value::decode(&invalid_utf8),
        Err(CodecError::InvalidUtf8 { .. })
    ));
}

#[test]
fn rich_text_decoder_rejects_explicit_length_overflow() {
    fn put_varint(mut value: u64, out: &mut Vec<u8>) {
        while value >= 0x80 {
            out.push((value as u8) | 0x80);
            value >>= 7;
        }
        out.push(value as u8);
    }

    let mut bytes = vec![5, 2, 0];
    put_varint(usize::MAX as u64, &mut bytes);
    bytes.push(0);
    bytes.push(0);
    bytes.push(1);
    bytes.push(0);

    let limits = InputLimits {
        max_sequence_len: usize::MAX,
        ..InputLimits::default()
    };
    assert!(matches!(
        Change::decode_with_limits(&bytes, &limits),
        Err(CodecError::IntegerOutOfRange { .. })
    ));
}