rustpad/src/collab.rs

/*
 * Copyright (C) 2026 Mateusz Gruszczynski @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 *
 * Free for non-commercial and evaluation use under terms of BSL/GPLv3.
 * Commercial or production use requires a valid paid license.
 * See LICENSE file in repository root for details.
 */

use serde::{Deserialize, Serialize};
use std::{
    collections::{HashMap, VecDeque},
    error::Error,
    fmt,
};

pub const MAX_OPERATION_COMPONENTS: usize = 4096;
const MAX_OPERATION_OWNER_SPANS: usize = 8192;
const MAX_OPERATION_INSERT_BYTES: usize = 2_000_000;
const MAX_OWNER_LENGTH: usize = 120;
const MAX_OPERATION_HISTORY: usize = 512;
const MAX_OPERATION_HISTORY_BYTES: usize = 8 * 1024 * 1024;
const AUTHORSHIP_VERSION: u8 = 2;
const OWNER_COLOR_SEPARATOR: char = '\u{001f}';

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct OwnerSpan {
    pub start: usize,
    pub end: usize,
    pub owner: String,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum OperationComponent {
    Retain {
        count: usize,
    },
    Delete {
        count: usize,
    },
    Insert {
        text: String,
        #[serde(default)]
        owners: Vec<OwnerSpan>,
    },
}

#[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq, Eq)]
pub struct TextOperation {
    #[serde(default)]
    pub components: Vec<OperationComponent>,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct OwnerReplacement {
    pub owner: String,
    pub replacement: String,
}

#[derive(Debug, Clone, Serialize)]
pub struct AppliedOperation {
    pub base_revision_id: i64,
    pub revision_id: i64,
    pub client_id: String,
    pub update_id: u64,
    pub operation: TextOperation,
    pub owner_replacements: Vec<OwnerReplacement>,
}

#[derive(Debug)]
pub struct CollaborativeDocument {
    pub content: String,
    pub owner_map: String,
    pub revision_id: i64,
    history: VecDeque<AppliedOperation>,
    history_bytes: usize,
    acknowledged_updates: HashMap<String, u64>,
}

impl CollaborativeDocument {
    pub fn new(content: String, owner_map: String, revision_id: i64) -> Self {
        Self {
            content,
            owner_map,
            revision_id,
            history: VecDeque::new(),
            history_bytes: 0,
            acknowledged_updates: HashMap::new(),
        }
    }

    pub fn transform_from(
        &self,
        base_revision_id: i64,
        operation: &TextOperation,
        client_id: &str,
        update_id: u64,
    ) -> Result<TextOperation, OperationError> {
        let mut transformed = normalize_operation(operation)?;
        if base_revision_id == self.revision_id {
            return Ok(transformed);
        }

        let Some(start) = self
            .history
            .iter()
            .position(|entry| entry.base_revision_id == base_revision_id)
        else {
            return Err(OperationError::RevisionUnavailable);
        };

        let mut expected_revision = base_revision_id;
        for applied in self.history.iter().skip(start) {
            if applied.base_revision_id != expected_revision {
                return Err(OperationError::RevisionUnavailable);
            }
            let incoming_has_priority =
                operation_key_before(client_id, update_id, &applied.client_id, applied.update_id);
            transformed =
                transform_operation(&transformed, &applied.operation, incoming_has_priority)?;
            expected_revision = applied.revision_id;
            if expected_revision == self.revision_id {
                return Ok(transformed);
            }
        }
        Err(OperationError::RevisionUnavailable)
    }

    pub fn acknowledge(&mut self, client_id: &str, update_id: u64) {
        self.acknowledged_updates
            .entry(client_id.to_owned())
            .and_modify(|acknowledged| *acknowledged = (*acknowledged).max(update_id))
            .or_insert(update_id);
    }

    pub fn has_applied_update(&self, client_id: &str, update_id: u64) -> bool {
        self.acknowledged_updates
            .get(client_id)
            .is_some_and(|acknowledged| update_id <= *acknowledged)
    }

    pub fn acknowledged_updates(&self, client_id: &str) -> Vec<u64> {
        self.acknowledged_updates
            .get(client_id)
            .copied()
            .into_iter()
            .collect()
    }

    pub fn operations_after(&self, revision_id: i64) -> Option<Vec<AppliedOperation>> {
        if revision_id == self.revision_id {
            return Some(Vec::new());
        }
        let start = self
            .history
            .iter()
            .position(|entry| entry.base_revision_id == revision_id)?;
        let mut expected_revision = revision_id;
        let mut operations = Vec::new();
        for applied in self.history.iter().skip(start) {
            if applied.base_revision_id != expected_revision {
                return None;
            }
            operations.push(applied.clone());
            expected_revision = applied.revision_id;
            if expected_revision == self.revision_id {
                return Some(operations);
            }
        }
        None
    }

    pub fn record(&mut self, operation: AppliedOperation) {
        self.acknowledge(&operation.client_id, operation.update_id);
        self.history_bytes = self
            .history_bytes
            .saturating_add(applied_operation_size(&operation));
        self.history.push_back(operation);
        while self.history.len() > MAX_OPERATION_HISTORY
            || self.history_bytes > MAX_OPERATION_HISTORY_BYTES
        {
            let Some(removed) = self.history.pop_front() else {
                break;
            };
            self.history_bytes = self
                .history_bytes
                .saturating_sub(applied_operation_size(&removed));
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ComponentKind {
    Retain,
    Delete,
    Insert,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum OperationError {
    InvalidComponent,
    InvalidUtf16Boundary,
    LengthMismatch,
    TooManyComponents,
    RevisionUnavailable,
    Serialization,
}

impl fmt::Display for OperationError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        let message = match self {
            Self::InvalidComponent => "invalid text operation component",
            Self::InvalidUtf16Boundary => "text operation splits a UTF-16 character",
            Self::LengthMismatch => "text operation length does not match the document",
            Self::TooManyComponents => "text operation contains too many components",
            Self::RevisionUnavailable => "the base revision is no longer available",
            Self::Serialization => "invalid authorship metadata",
        };
        formatter.write_str(message)
    }
}

impl Error for OperationError {}

fn applied_operation_size(operation: &AppliedOperation) -> usize {
    let components = operation
        .operation
        .components
        .iter()
        .map(|component| match component {
            OperationComponent::Retain { .. } | OperationComponent::Delete { .. } => 24,
            OperationComponent::Insert { text, owners } => {
                32usize.saturating_add(text.len()).saturating_add(
                    owners
                        .iter()
                        .map(|span| 24usize.saturating_add(span.owner.len()))
                        .sum::<usize>(),
                )
            }
        })
        .sum::<usize>();
    components
        .saturating_add(operation.client_id.len())
        .saturating_add(
            operation
                .owner_replacements
                .iter()
                .map(|replacement| replacement.owner.len() + replacement.replacement.len() + 16)
                .sum::<usize>(),
        )
}

fn operation_key_before(
    left_client_id: &str,
    left_update_id: u64,
    right_client_id: &str,
    right_update_id: u64,
) -> bool {
    left_client_id < right_client_id
        || (left_client_id == right_client_id && left_update_id < right_update_id)
}

fn component_kind(component: &OperationComponent) -> ComponentKind {
    match component {
        OperationComponent::Retain { .. } => ComponentKind::Retain,
        OperationComponent::Delete { .. } => ComponentKind::Delete,
        OperationComponent::Insert { .. } => ComponentKind::Insert,
    }
}

fn component_length(component: &OperationComponent) -> usize {
    match component {
        OperationComponent::Retain { count } | OperationComponent::Delete { count } => *count,
        OperationComponent::Insert { text, .. } => text.encode_utf16().count(),
    }
}

fn normalize_owner_spans(spans: &[OwnerSpan], length: usize) -> Vec<OwnerSpan> {
    let mut sorted = spans
        .iter()
        .filter_map(|span| {
            let start = span.start.min(length);
            let end = span.end.min(length).max(start);
            if span.owner.is_empty() || end <= start {
                None
            } else {
                Some(OwnerSpan {
                    start,
                    end,
                    owner: span.owner.clone(),
                })
            }
        })
        .collect::<Vec<_>>();
    sorted.sort_by_key(|span| (span.start, span.end));
    let mut result: Vec<OwnerSpan> = Vec::new();
    for mut span in sorted {
        if let Some(previous) = result.last_mut() {
            if previous.owner == span.owner && span.start <= previous.end {
                previous.end = previous.end.max(span.end);
                continue;
            }
            if span.start < previous.end {
                span.start = previous.end;
            }
        }
        if span.end > span.start {
            result.push(span);
        }
    }
    result
}

fn slice_owner_spans(spans: &[OwnerSpan], start: usize, length: usize) -> Vec<OwnerSpan> {
    let end = start.saturating_add(length);
    let sliced = spans
        .iter()
        .filter_map(|span| {
            let overlap_start = start.max(span.start);
            let overlap_end = end.min(span.end);
            (overlap_end > overlap_start).then(|| OwnerSpan {
                start: overlap_start - start,
                end: overlap_end - start,
                owner: span.owner.clone(),
            })
        })
        .collect::<Vec<_>>();
    normalize_owner_spans(&sliced, length)
}

fn shift_owner_spans(spans: &[OwnerSpan], offset: usize) -> Vec<OwnerSpan> {
    spans
        .iter()
        .map(|span| OwnerSpan {
            start: span.start + offset,
            end: span.end + offset,
            owner: span.owner.clone(),
        })
        .collect()
}

fn append_component(
    components: &mut Vec<OperationComponent>,
    component: OperationComponent,
) -> Result<(), OperationError> {
    match component {
        OperationComponent::Retain { count } => {
            if count == 0 {
                return Ok(());
            }
            if let Some(OperationComponent::Retain { count: previous }) = components.last_mut() {
                *previous = previous
                    .checked_add(count)
                    .ok_or(OperationError::InvalidComponent)?;
            } else {
                components.push(OperationComponent::Retain { count });
            }
        }
        OperationComponent::Delete { count } => {
            if count == 0 {
                return Ok(());
            }
            if let Some(OperationComponent::Delete { count: previous }) = components.last_mut() {
                *previous = previous
                    .checked_add(count)
                    .ok_or(OperationError::InvalidComponent)?;
            } else {
                components.push(OperationComponent::Delete { count });
            }
        }
        OperationComponent::Insert { text, owners } => {
            let length = text.encode_utf16().count();
            if length == 0 {
                return Ok(());
            }
            let owners = normalize_owner_spans(&owners, length);
            if let Some(OperationComponent::Insert {
                text: previous_text,
                owners: previous_owners,
            }) = components.last_mut()
            {
                let offset = previous_text.encode_utf16().count();
                previous_text.push_str(&text);
                previous_owners.extend(shift_owner_spans(&owners, offset));
                *previous_owners =
                    normalize_owner_spans(previous_owners, previous_text.encode_utf16().count());
            } else {
                components.push(OperationComponent::Insert { text, owners });
            }
        }
    }
    if components.len() > MAX_OPERATION_COMPONENTS {
        return Err(OperationError::TooManyComponents);
    }
    Ok(())
}

pub fn normalize_operation(operation: &TextOperation) -> Result<TextOperation, OperationError> {
    if operation.components.len() > MAX_OPERATION_COMPONENTS {
        return Err(OperationError::TooManyComponents);
    }
    let mut inserted_bytes = 0usize;
    let mut owner_span_count = 0usize;
    let mut components = Vec::with_capacity(operation.components.len());
    for component in &operation.components {
        if let OperationComponent::Insert { text, owners } = component {
            inserted_bytes = inserted_bytes
                .checked_add(text.len())
                .ok_or(OperationError::InvalidComponent)?;
            owner_span_count = owner_span_count
                .checked_add(owners.len())
                .ok_or(OperationError::InvalidComponent)?;
            let text_length = text.encode_utf16().count();
            if inserted_bytes > MAX_OPERATION_INSERT_BYTES
                || owner_span_count > MAX_OPERATION_OWNER_SPANS
                || owners.iter().any(|span| {
                    span.start > span.end
                        || span.end > text_length
                        || utf16_byte_index(text, span.start).is_err()
                        || utf16_byte_index(text, span.end).is_err()
                        || span.owner.chars().count() > MAX_OWNER_LENGTH
                        || span.owner.chars().any(|character| {
                            character.is_control() && character != OWNER_COLOR_SEPARATOR
                        })
                })
            {
                return Err(OperationError::InvalidComponent);
            }
        }
        append_component(&mut components, component.clone())?;
    }
    Ok(TextOperation { components })
}

pub fn operation_base_length(operation: &TextOperation) -> Result<usize, OperationError> {
    normalize_operation(operation)?
        .components
        .iter()
        .try_fold(0usize, |length, component| {
            let component_length = match component {
                OperationComponent::Retain { count } | OperationComponent::Delete { count } => {
                    *count
                }
                OperationComponent::Insert { .. } => 0,
            };
            length
                .checked_add(component_length)
                .ok_or(OperationError::InvalidComponent)
        })
}

pub fn operation_from_edit(
    previous_content: &str,
    next_content: &str,
    next_owner_map: &str,
) -> TextOperation {
    let mut previous_prefix_bytes = 0usize;
    let mut next_prefix_bytes = 0usize;
    for (previous, next) in previous_content.chars().zip(next_content.chars()) {
        if previous != next {
            break;
        }
        previous_prefix_bytes += previous.len_utf8();
        next_prefix_bytes += next.len_utf8();
    }

    let previous_remainder = &previous_content[previous_prefix_bytes..];
    let next_remainder = &next_content[next_prefix_bytes..];
    let mut previous_suffix_bytes = 0usize;
    let mut next_suffix_bytes = 0usize;
    for (previous, next) in previous_remainder
        .chars()
        .rev()
        .zip(next_remainder.chars().rev())
    {
        if previous != next {
            break;
        }
        previous_suffix_bytes += previous.len_utf8();
        next_suffix_bytes += next.len_utf8();
    }

    let previous_middle_end = previous_content.len() - previous_suffix_bytes;
    let next_middle_end = next_content.len() - next_suffix_bytes;
    let previous_prefix = &previous_content[..previous_prefix_bytes];
    let previous_middle = &previous_content[previous_prefix_bytes..previous_middle_end];
    let next_middle = &next_content[next_prefix_bytes..next_middle_end];
    let suffix = &previous_content[previous_middle_end..];

    let prefix_length = previous_prefix.encode_utf16().count();
    let deleted_length = previous_middle.encode_utf16().count();
    let inserted_length = next_middle.encode_utf16().count();
    let suffix_length = suffix.encode_utf16().count();
    let next_authorship = parse_authorship(next_content, next_owner_map);
    let inserted_owners = slice_owner_spans(&next_authorship.spans, prefix_length, inserted_length);

    let mut components = Vec::new();
    if prefix_length > 0 {
        components.push(OperationComponent::Retain {
            count: prefix_length,
        });
    }
    if deleted_length > 0 {
        components.push(OperationComponent::Delete {
            count: deleted_length,
        });
    }
    if !next_middle.is_empty() {
        components.push(OperationComponent::Insert {
            text: next_middle.to_owned(),
            owners: inserted_owners,
        });
    }
    if suffix_length > 0 {
        components.push(OperationComponent::Retain {
            count: suffix_length,
        });
    }
    TextOperation { components }
}

pub fn replace_operation(
    base_length: usize,
    content: String,
    owners: Vec<OwnerSpan>,
) -> TextOperation {
    let mut components = Vec::new();
    if base_length > 0 {
        components.push(OperationComponent::Delete { count: base_length });
    }
    if !content.is_empty() {
        components.push(OperationComponent::Insert {
            text: content,
            owners,
        });
    }
    TextOperation { components }
}

struct OperationCursor {
    components: Vec<OperationComponent>,
    index: usize,
    offset: usize,
}

impl OperationCursor {
    fn new(operation: &TextOperation) -> Result<Self, OperationError> {
        Ok(Self {
            components: normalize_operation(operation)?.components,
            index: 0,
            offset: 0,
        })
    }

    fn current(&self) -> Option<&OperationComponent> {
        self.components.get(self.index)
    }

    fn kind(&self) -> Option<ComponentKind> {
        self.current().map(component_kind)
    }

    fn remaining(&self) -> usize {
        self.current()
            .map(|component| component_length(component).saturating_sub(self.offset))
            .unwrap_or(0)
    }

    fn take(&mut self, count: usize) -> Result<OperationComponent, OperationError> {
        let component = self
            .current()
            .cloned()
            .ok_or(OperationError::InvalidComponent)?;
        if count == 0 || count > self.remaining() {
            return Err(OperationError::InvalidComponent);
        }
        let component_length = component_length(&component);
        let part = match component {
            OperationComponent::Retain { .. } => OperationComponent::Retain { count },
            OperationComponent::Delete { .. } => OperationComponent::Delete { count },
            OperationComponent::Insert { text, owners } => OperationComponent::Insert {
                text: slice_utf16(&text, self.offset, count)?.to_owned(),
                owners: slice_owner_spans(&owners, self.offset, count),
            },
        };
        self.offset += count;
        if self.offset == component_length {
            self.index += 1;
            self.offset = 0;
        }
        Ok(part)
    }

    fn take_remaining(&mut self) -> Result<OperationComponent, OperationError> {
        let count = self.remaining();
        self.take(count)
    }
}

pub fn transform_operation(
    left_operation: &TextOperation,
    right_operation: &TextOperation,
    left_before_right: bool,
) -> Result<TextOperation, OperationError> {
    if operation_base_length(left_operation)? != operation_base_length(right_operation)? {
        return Err(OperationError::LengthMismatch);
    }
    let mut left = OperationCursor::new(left_operation)?;
    let mut right = OperationCursor::new(right_operation)?;
    let mut left_prime = Vec::new();

    while left.current().is_some() || right.current().is_some() {
        if left.kind() == Some(ComponentKind::Insert)
            && (right.kind() != Some(ComponentKind::Insert) || left_before_right)
        {
            append_component(&mut left_prime, left.take_remaining()?)?;
            continue;
        }
        if right.kind() == Some(ComponentKind::Insert) {
            let count = right.remaining();
            right.take_remaining()?;
            append_component(&mut left_prime, OperationComponent::Retain { count })?;
            continue;
        }
        let (Some(left_kind), Some(right_kind)) = (left.kind(), right.kind()) else {
            return Err(OperationError::InvalidComponent);
        };
        let count = left.remaining().min(right.remaining());
        match (left_kind, right_kind) {
            (ComponentKind::Retain, ComponentKind::Retain) => {
                append_component(&mut left_prime, OperationComponent::Retain { count })?;
            }
            (ComponentKind::Delete, ComponentKind::Retain) => {
                append_component(&mut left_prime, OperationComponent::Delete { count })?;
            }
            (ComponentKind::Retain, ComponentKind::Delete)
            | (ComponentKind::Delete, ComponentKind::Delete) => {}
            _ => return Err(OperationError::InvalidComponent),
        }
        left.take(count)?;
        right.take(count)?;
    }
    Ok(TextOperation {
        components: left_prime,
    })
}

fn utf16_byte_index(value: &str, offset: usize) -> Result<usize, OperationError> {
    if offset == 0 {
        return Ok(0);
    }
    let mut current = 0usize;
    for (byte_index, character) in value.char_indices() {
        if current == offset {
            return Ok(byte_index);
        }
        current += character.len_utf16();
        if current > offset {
            return Err(OperationError::InvalidUtf16Boundary);
        }
    }
    if current == offset {
        Ok(value.len())
    } else {
        Err(OperationError::LengthMismatch)
    }
}

fn slice_utf16(value: &str, start: usize, length: usize) -> Result<&str, OperationError> {
    let start_byte = utf16_byte_index(value, start)?;
    let end_byte = utf16_byte_index(value, start.saturating_add(length))?;
    value
        .get(start_byte..end_byte)
        .ok_or(OperationError::InvalidUtf16Boundary)
}

#[derive(Debug, Clone, Serialize, Deserialize)]
struct AuthorshipModel {
    #[serde(default = "authorship_version")]
    version: u8,
    #[serde(default)]
    spans: Vec<OwnerSpan>,
}

fn authorship_version() -> u8 {
    AUTHORSHIP_VERSION
}

#[derive(Debug, Deserialize)]
#[serde(untagged)]
enum RawAuthorship {
    Model(AuthorshipModel),
    LineOwners(Vec<String>),
}

fn parse_authorship(content: &str, raw: &str) -> AuthorshipModel {
    let length = content.encode_utf16().count();
    match serde_json::from_str::<RawAuthorship>(raw) {
        Ok(RawAuthorship::Model(model)) if model.version == AUTHORSHIP_VERSION => AuthorshipModel {
            version: AUTHORSHIP_VERSION,
            spans: normalize_owner_spans(&model.spans, length),
        },
        Ok(RawAuthorship::LineOwners(owners)) => {
            let lines = content.split('\n').collect::<Vec<_>>();
            let mut offset = 0usize;
            let mut spans = Vec::new();
            for (index, line) in lines.iter().enumerate() {
                let line_length =
                    line.encode_utf16().count() + usize::from(index + 1 < lines.len());
                let owner = owners.get(index).cloned().unwrap_or_default();
                if !owner.is_empty() && line_length > 0 {
                    spans.push(OwnerSpan {
                        start: offset,
                        end: offset + line_length,
                        owner,
                    });
                }
                offset += line_length;
            }
            AuthorshipModel {
                version: AUTHORSHIP_VERSION,
                spans: normalize_owner_spans(&spans, length),
            }
        }
        _ => AuthorshipModel {
            version: AUTHORSHIP_VERSION,
            spans: Vec::new(),
        },
    }
}

fn copy_retained_spans(
    target: &mut Vec<OwnerSpan>,
    spans: &[OwnerSpan],
    source_start: usize,
    length: usize,
    output_start: usize,
) {
    let source_end = source_start + length;
    for span in spans {
        let start = source_start.max(span.start);
        let end = source_end.min(span.end);
        if end > start {
            target.push(OwnerSpan {
                start: output_start + start - source_start,
                end: output_start + end - source_start,
                owner: span.owner.clone(),
            });
        }
    }
}

pub fn apply_operation_to_document(
    content: &str,
    owner_map: &str,
    operation: &TextOperation,
    owner_replacements: &[OwnerReplacement],
) -> Result<(String, String), OperationError> {
    let operation = normalize_operation(operation)?;
    let content_length = content.encode_utf16().count();
    if operation_base_length(&operation)? != content_length {
        return Err(OperationError::LengthMismatch);
    }

    let source_model = parse_authorship(content, owner_map);
    let mut output_spans = Vec::new();
    let mut source_offset = 0usize;
    let mut output_offset = 0usize;
    let mut output_content = String::new();

    for component in &operation.components {
        match component {
            OperationComponent::Retain { count } => {
                output_content.push_str(slice_utf16(content, source_offset, *count)?);
                copy_retained_spans(
                    &mut output_spans,
                    &source_model.spans,
                    source_offset,
                    *count,
                    output_offset,
                );
                source_offset += *count;
                output_offset += *count;
            }
            OperationComponent::Delete { count } => {
                source_offset += *count;
            }
            OperationComponent::Insert { text, owners } => {
                output_content.push_str(text);
                output_spans.extend(shift_owner_spans(owners, output_offset));
                output_offset += text.encode_utf16().count();
            }
        }
    }
    if source_offset != content_length {
        return Err(OperationError::LengthMismatch);
    }

    for span in &mut output_spans {
        let identity = span
            .owner
            .split(OWNER_COLOR_SEPARATOR)
            .next()
            .unwrap_or_default();
        if let Some(replacement) = owner_replacements.iter().find(|replacement| {
            replacement.owner == identity && !replacement.replacement.is_empty()
        }) {
            span.owner.clone_from(&replacement.replacement);
        }
    }
    let model = AuthorshipModel {
        version: AUTHORSHIP_VERSION,
        spans: normalize_owner_spans(&output_spans, output_offset),
    };
    let owner_map = serde_json::to_string(&model).map_err(|_| OperationError::Serialization)?;
    Ok((output_content, owner_map))
}

pub fn owner_spans_from_map(content: &str, owner_map: &str) -> Vec<OwnerSpan> {
    parse_authorship(content, owner_map).spans
}

#[cfg(test)]
#[path = "tests/collab.rs"]
mod tests;