tus-protocol 0.1.0

//! TUS server configuration.
//!
//! This module defines the configuration options for a TUS server,
//! including supported extensions, size limits, and timeouts.

use std::collections::HashSet;
use std::time::Duration;

use crate::error::Error;

/// Characters escaped when an upload id is placed in a URL path segment:
/// everything except RFC 3986 unreserved characters.
const PATH_SEGMENT_ENCODE: &percent_encoding::AsciiSet = &percent_encoding::NON_ALPHANUMERIC
    .remove(b'-')
    .remove(b'_')
    .remove(b'.')
    .remove(b'~');

/// The TUS protocol version supported by this implementation.
pub const TUS_VERSION: &str = "1.0.0";

/// Resumable header value for the TUS protocol.
pub const TUS_RESUMABLE: &str = "1.0.0";

/// Default cap on bytes buffered in memory while accepting a request body whose
/// length is not known in advance (chunked transfer encoding / no
/// `Content-Length`). See [`Config::max_intake_buffer`].
pub const DEFAULT_MAX_INTAKE_BUFFER: u64 = 8 * 1024 * 1024;

/// TUS server configuration.
///
/// # Defaults
///
/// [`Config::default`] enables Creation, Termination, and
/// Creation-Defer-Length; accepts standard empty Creation requests; uses
/// `/files` as the base path; has no maximum upload size, no expiration, and a
/// 30-second lock timeout; does not trust forwarded proxy headers; and caps
/// in-memory intake buffering for bodies of unknown length at
/// [`DEFAULT_MAX_INTAKE_BUFFER`].
///
/// # Examples
///
/// ```rust
/// use std::time::Duration;
/// use tus_protocol::{Config, Extension};
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// // `try_with_extension` returns an error instead of panicking when the
/// // current build cannot service the extension (see [`Config::with_extension`]
/// // for the panicking counterpart and when each is appropriate).
/// let config = Config::new()
///     .with_base_path("/uploads")
///     .with_max_size(100 * 1024 * 1024)
///     .with_expiration(Duration::from_secs(24 * 60 * 60))
///     .try_with_extension(Extension::Concatenation)?;
///
/// assert_eq!(config.base_path(), "/uploads");
/// assert!(config.has_extension(Extension::Concatenation));
/// # Ok(())
/// # }
/// ```
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub struct Config {
    /// Maximum upload size in bytes. None means unlimited.
    max_size: Option<u64>,

    /// Enabled TUS extensions.
    extensions: HashSet<Extension>,

    /// Supported checksum algorithms (only relevant if Checksum extension is enabled).
    checksum_algorithms: HashSet<ChecksumAlgorithm>,

    /// Default expiration duration for uploads. None means uploads don't expire.
    expiration: Option<Duration>,

    /// Lock acquisition timeout.
    lock_timeout: Duration,

    /// Base path for the TUS endpoint (e.g., "/files").
    base_path: String,

    /// Base URL for absolute Location headers (e.g., "http://localhost:8080").
    /// If set, Location headers will be absolute URLs.
    base_url: Option<String>,

    /// Whether to respect forwarded headers (X-Forwarded-Host, X-Forwarded-Proto).
    respect_forwarded_headers: bool,

    /// Maximum chunk size per PATCH request. None means unlimited.
    max_chunk_size: Option<u64>,

    /// Maximum bytes buffered in memory while accepting a request body whose
    /// length is not known in advance (chunked transfer encoding / no
    /// `Content-Length`, e.g. checksum trailers). `None` disables the cap
    /// (unbounded intake buffering). Bodies with a known `Content-Length`
    /// stream in constant memory and are not affected.
    max_intake_buffer: Option<u64>,

    /// Whether to disable download (GET) endpoint.
    disable_download: bool,

    /// Whether to allow standard empty Creation requests.
    allow_empty_creation: bool,
}

impl Default for Config {
    fn default() -> Self {
        let mut extensions = HashSet::new();
        extensions.insert(Extension::Creation);
        extensions.insert(Extension::Termination);
        extensions.insert(Extension::CreationDeferLength);

        Self {
            max_size: None,
            extensions,
            checksum_algorithms: HashSet::new(),
            expiration: None,
            lock_timeout: Duration::from_secs(30),
            base_path: "/files".to_string(),
            base_url: None,
            respect_forwarded_headers: false,
            max_chunk_size: None,
            max_intake_buffer: Some(DEFAULT_MAX_INTAKE_BUFFER),
            disable_download: false,
            allow_empty_creation: true,
        }
    }
}

impl Config {
    /// Creates a new configuration with default settings.
    pub fn new() -> Self {
        Self::default()
    }

    /// Creates a configuration with all extensions enabled, including the
    /// non-standard `ConcatenationUnfinished`.
    ///
    /// Note: advertising `concatenation-unfinished` means final uploads with
    /// incomplete partials are accepted (the extension's defining behavior),
    /// which supersedes the core concatenation requirement that partials must
    /// be complete. If you want strict core-concatenation semantics, use
    /// [`Config::default()`] plus explicit `.with_extension(...)` calls
    /// and don't enable `ConcatenationUnfinished`.
    #[must_use]
    pub fn all_extensions() -> Self {
        Self {
            extensions: Extension::supported().iter().copied().collect(),
            checksum_algorithms: [
                ChecksumAlgorithm::Sha1,
                ChecksumAlgorithm::Sha256,
                ChecksumAlgorithm::Md5,
                ChecksumAlgorithm::Crc32,
            ]
            .into_iter()
            .collect(),
            ..Self::default()
        }
    }

    /// Sets the maximum upload size.
    #[must_use]
    pub fn with_max_size(mut self, size: u64) -> Self {
        self.max_size = Some(size);
        self
    }

    /// Adds an extension to the enabled set.
    ///
    /// When enabling the Checksum extension, default algorithms (sha1) are automatically
    /// added if no algorithms are already configured. Use `with_checksum()` to add
    /// additional algorithms.
    ///
    /// # Panics
    ///
    /// Panics when enabling [`Extension::Checksum`] or
    /// [`Extension::ChecksumTrailer`] without the `checksum` Cargo feature:
    /// the extension would be advertised but no algorithm could ever verify a
    /// request. Enable the `checksum` feature of `tus-protocol` to use these
    /// extensions.
    ///
    /// Because whether the `checksum` feature is enabled is often decided by
    /// Cargo feature unification rather than by the code calling this method,
    /// prefer [`Config::try_with_extension`] when the extension set is not
    /// statically known to be serviceable by the current build.
    #[must_use]
    pub fn with_extension(self, ext: Extension) -> Self {
        self.try_with_extension(ext).unwrap_or_else(|err| {
            panic!("{err}");
        })
    }

    /// Adds an extension to the enabled set, returning an error instead of
    /// panicking when the current build cannot service it.
    ///
    /// Enabling [`Extension::Checksum`] or [`Extension::ChecksumTrailer`]
    /// without the `checksum` Cargo feature returns
    /// [`Error::ExtensionNotSupported`]: the extension would be advertised but
    /// no algorithm could ever verify a request. This is the fallible
    /// counterpart to [`Config::with_extension`]; use it when whether the
    /// `checksum` feature is enabled is not under this call site's control.
    ///
    /// When enabling the Checksum extension, default algorithms (sha1) are
    /// automatically added if no algorithms are already configured.
    ///
    /// # Errors
    ///
    /// Returns [`Error::ExtensionNotSupported`] when enabling a checksum
    /// extension without the `checksum` Cargo feature.
    pub fn try_with_extension(mut self, ext: Extension) -> Result<Self, Error> {
        #[cfg(not(feature = "checksum"))]
        if matches!(ext, Extension::Checksum | Extension::ChecksumTrailer) {
            return Err(Error::ExtensionNotSupported(format!(
                "{}: enable the `checksum` feature of tus-protocol",
                ext.as_str()
            )));
        }

        self.extensions.insert(ext);
        // When enabling Checksum extension, ensure at least sha1 is available
        #[cfg(feature = "checksum")]
        if matches!(ext, Extension::Checksum | Extension::ChecksumTrailer) {
            self.extensions.insert(Extension::Checksum);
            if self.checksum_algorithms.is_empty() {
                self.checksum_algorithms.insert(ChecksumAlgorithm::Sha1);
            }
        }
        Ok(self)
    }

    /// Removes an extension from the enabled set.
    #[must_use]
    pub fn without_extension(mut self, ext: Extension) -> Self {
        self.extensions.remove(&ext);
        self
    }

    /// Sets the expiration duration for uploads.
    #[must_use]
    pub fn with_expiration(mut self, duration: Duration) -> Self {
        self.expiration = Some(duration);
        self.extensions.insert(Extension::Expiration);
        self
    }

    /// Sets the lock acquisition timeout.
    #[must_use]
    pub fn with_lock_timeout(mut self, timeout: Duration) -> Self {
        self.lock_timeout = timeout;
        self
    }

    /// Sets the base path for the TUS endpoint.
    #[must_use]
    pub fn with_base_path(mut self, path: impl Into<String>) -> Self {
        self.base_path = path.into();
        self
    }

    /// Sets the base URL for absolute Location headers.
    ///
    /// When set, Location headers will include the full URL (e.g., "http://localhost:8080/files/abc").
    /// The base URL should not include a trailing slash.
    #[must_use]
    pub fn with_base_url(mut self, url: impl Into<String>) -> Self {
        self.base_url = Some(url.into());
        self
    }

    /// Trusts the `X-Forwarded-Host` and `X-Forwarded-Proto` request headers
    /// when building absolute `Location` URLs.
    ///
    /// Disabled by default, and it should stay disabled unless a trusted
    /// reverse proxy sits in front of the server. These headers are
    /// client-supplied: if untrusted requests reach the server directly, an
    /// attacker can set `X-Forwarded-Host` to an arbitrary value and poison the
    /// `Location` URL returned from Creation (a classic host-header injection /
    /// URL-poisoning vector). Only enable this when a proxy you control
    /// **overwrites** (not appends to) `X-Forwarded-Host` / `X-Forwarded-Proto`
    /// on every inbound request, so clients cannot forge them. Setting
    /// [`with_base_url`](Self::with_base_url) instead pins the origin explicitly
    /// and takes precedence over forwarded headers.
    #[must_use]
    pub fn with_respect_forwarded_headers(mut self) -> Self {
        self.respect_forwarded_headers = true;
        self
    }

    /// Sets the maximum chunk size per PATCH request.
    #[must_use]
    pub fn with_max_chunk_size(mut self, size: u64) -> Self {
        self.max_chunk_size = Some(size);
        self
    }

    /// Sets the maximum bytes buffered in memory for a request body whose
    /// length is not known in advance (chunked transfer encoding / no
    /// `Content-Length`).
    ///
    /// Bodies with a known `Content-Length` stream to storage in constant
    /// memory and are unaffected. A body without `Content-Length` (chunked
    /// transfer encoding, including checksum-trailer uploads) must be buffered
    /// to discover its size before it can be committed, so this bounds that
    /// buffer. Exceeding it fails the request with `413 Payload Too Large`.
    ///
    /// Defaults to [`DEFAULT_MAX_INTAKE_BUFFER`]. Raise it for deployments that
    /// accept large chunked uploads, or call
    /// [`without_intake_buffer_limit`](Self::without_intake_buffer_limit) to
    /// remove the cap entirely.
    ///
    /// Note the distinction between the two edge cases: `size == 0` *disables*
    /// buffering support, so any non-empty unknown-length body is rejected with
    /// `413` on its first chunk, whereas
    /// [`without_intake_buffer_limit`](Self::without_intake_buffer_limit) leaves
    /// the buffer *unbounded*.
    #[must_use]
    pub fn with_max_intake_buffer(mut self, size: u64) -> Self {
        self.max_intake_buffer = Some(size);
        self
    }

    /// Removes the in-memory intake-buffer cap, allowing a body of unknown
    /// length (chunked transfer / no `Content-Length`) to be buffered without
    /// bound.
    ///
    /// This re-enables the memory-exhaustion exposure that
    /// [`with_max_intake_buffer`](Self::with_max_intake_buffer) guards against;
    /// only use it when an upstream layer already bounds request body size.
    #[must_use]
    pub fn without_intake_buffer_limit(mut self) -> Self {
        self.max_intake_buffer = None;
        self
    }

    /// Disables the download endpoint.
    #[must_use]
    pub fn without_download(mut self) -> Self {
        self.disable_download = true;
        self
    }

    /// Adds a checksum algorithm to the supported set and enables the
    /// Checksum extension.
    ///
    /// SHA-1 is always added alongside the given algorithm because the tus
    /// specification requires servers supporting the Checksum extension to
    /// accept SHA-1. Trailer checksums are a separate extension; enable them
    /// explicitly with `with_extension(Extension::ChecksumTrailer)`.
    #[cfg(feature = "checksum")]
    #[must_use]
    pub fn with_checksum(mut self, algorithm: ChecksumAlgorithm) -> Self {
        self.checksum_algorithms.insert(algorithm);
        self.checksum_algorithms.insert(ChecksumAlgorithm::Sha1);
        self.extensions.insert(Extension::Checksum);
        self
    }

    /// Rejects empty creation requests.
    ///
    /// The tus Creation extension uses an empty `POST` with `Upload-Length` as
    /// its standard creation example, and it is accepted by default. Calling
    /// this is an opt-in non-compliant mode for deployments that only want
    /// Creation-With-Upload requests to create new resources.
    #[must_use]
    pub fn without_empty_creation(mut self) -> Self {
        self.allow_empty_creation = false;
        self
    }

    /// Checks if an extension is enabled.
    pub fn has_extension(&self, ext: Extension) -> bool {
        self.extensions.contains(&ext)
    }

    /// Returns the configured maximum upload size in bytes, if any.
    pub fn max_size(&self) -> Option<u64> {
        self.max_size
    }

    /// Returns the supported checksum algorithms, sorted by name.
    ///
    /// The internal collection type is deliberately not exposed so it can
    /// change without breaking callers.
    pub fn checksum_algorithms(&self) -> Vec<ChecksumAlgorithm> {
        let mut algorithms: Vec<_> = self.checksum_algorithms.iter().copied().collect();
        algorithms.sort_by_key(|algorithm| algorithm.as_str());
        algorithms
    }

    /// Returns whether a checksum algorithm is supported.
    pub fn supports_checksum_algorithm(&self, algorithm: ChecksumAlgorithm) -> bool {
        self.checksum_algorithms.contains(&algorithm)
    }

    /// Returns the configured expiration duration, if any.
    pub fn expiration(&self) -> Option<Duration> {
        self.expiration
    }

    /// Returns the lock acquisition timeout.
    pub fn lock_timeout(&self) -> Duration {
        self.lock_timeout
    }

    /// Returns the base path for TUS endpoints.
    pub fn base_path(&self) -> &str {
        &self.base_path
    }

    /// Returns the configured base URL for absolute Location headers.
    pub fn base_url(&self) -> Option<&str> {
        self.base_url.as_deref()
    }

    /// Returns whether forwarded proxy headers should be trusted.
    pub fn respects_forwarded_headers(&self) -> bool {
        self.respect_forwarded_headers
    }

    /// Returns the maximum PATCH chunk size, if configured.
    pub fn max_chunk_size(&self) -> Option<u64> {
        self.max_chunk_size
    }

    /// Returns the in-memory intake-buffer cap for bodies of unknown length,
    /// if any. `None` means intake buffering is unbounded.
    pub fn max_intake_buffer(&self) -> Option<u64> {
        self.max_intake_buffer
    }

    /// Returns whether the download endpoint is disabled.
    pub fn is_download_disabled(&self) -> bool {
        self.disable_download
    }

    /// Returns whether empty creation requests are allowed.
    pub fn allows_empty_creation(&self) -> bool {
        self.allow_empty_creation
    }

    /// Returns the extensions as a comma-separated string for the Tus-Extension header.
    pub fn extensions_string(&self) -> String {
        let mut exts: Vec<_> = self.extensions.iter().map(|e| e.as_str()).collect();
        exts.sort();
        exts.join(",")
    }

    /// Returns the checksum algorithms as a comma-separated string.
    pub fn checksum_algorithms_string(&self) -> String {
        self.checksum_algorithms()
            .iter()
            .map(|a| a.as_str())
            .collect::<Vec<_>>()
            .join(",")
    }

    /// Builds the full URL for an upload.
    ///
    /// The upload id is percent-encoded as a path segment so externally
    /// seeded ids with reserved characters still yield a usable Location.
    ///
    /// Uses the following priority for base URL:
    /// 1. Config's base_url if set
    /// 2. Request's base URL (from scheme + host) if provided
    /// 3. Falls back to relative path
    pub fn upload_url(&self, upload_id: &str, request_base_url: Option<&str>) -> String {
        let upload_id = percent_encoding::utf8_percent_encode(upload_id, PATH_SEGMENT_ENCODE);
        let base = self.base_url.as_deref().or(request_base_url);
        match base {
            Some(base) => format!("{}{}/{}", base, self.base_path, upload_id),
            None => format!("{}/{}", self.base_path, upload_id),
        }
    }
}

/// TUS protocol extensions.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum Extension {
    /// Creation extension - allows creating new uploads via POST.
    Creation,
    /// Creation with upload - allows including data in the initial POST request.
    CreationWithUpload,
    /// Creation with deferred length - allows uploads without knowing size upfront.
    CreationDeferLength,
    /// Termination extension - allows deleting uploads via DELETE.
    Termination,
    /// Expiration extension - uploads can expire and be cleaned up.
    Expiration,
    /// Concatenation extension - allows merging partial uploads.
    Concatenation,
    /// Concatenation-Unfinished extension - allows creating final uploads before all partials are complete.
    ConcatenationUnfinished,
    /// Checksum extension - allows verifying chunk integrity.
    Checksum,
    /// Checksum trailer extension - allows checksums to be sent as HTTP trailers.
    ChecksumTrailer,
}

impl Extension {
    /// Returns the extension name as used in the Tus-Extension header.
    pub fn as_str(self) -> &'static str {
        match self {
            Extension::Creation => "creation",
            Extension::CreationWithUpload => "creation-with-upload",
            Extension::CreationDeferLength => "creation-defer-length",
            Extension::Termination => "termination",
            Extension::Expiration => "expiration",
            Extension::Concatenation => "concatenation",
            Extension::ConcatenationUnfinished => "concatenation-unfinished",
            Extension::Checksum => "checksum",
            Extension::ChecksumTrailer => "checksum-trailer",
        }
    }

    /// Returns all extensions supported by this build.
    pub fn supported() -> &'static [Extension] {
        &[
            Extension::Creation,
            Extension::CreationWithUpload,
            Extension::CreationDeferLength,
            Extension::Termination,
            Extension::Expiration,
            Extension::Concatenation,
            Extension::ConcatenationUnfinished,
            #[cfg(feature = "checksum")]
            Extension::Checksum,
            #[cfg(feature = "checksum")]
            Extension::ChecksumTrailer,
        ]
    }
}

impl std::fmt::Display for Extension {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl std::str::FromStr for Extension {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "creation" => Ok(Extension::Creation),
            "creation-with-upload" => Ok(Extension::CreationWithUpload),
            "creation-defer-length" => Ok(Extension::CreationDeferLength),
            "termination" => Ok(Extension::Termination),
            "expiration" => Ok(Extension::Expiration),
            "concatenation" => Ok(Extension::Concatenation),
            "concatenation-unfinished" => Ok(Extension::ConcatenationUnfinished),
            "checksum" => Ok(Extension::Checksum),
            "checksum-trailer" => Ok(Extension::ChecksumTrailer),
            other => Err(Error::ExtensionNotSupported(other.to_string())),
        }
    }
}

/// Checksum algorithms supported by the checksum extension.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum ChecksumAlgorithm {
    /// SHA-1 hash.
    Sha1,
    /// SHA-256 hash.
    Sha256,
    /// MD5 hash.
    Md5,
    /// CRC32 checksum.
    Crc32,
}

impl ChecksumAlgorithm {
    /// Returns the algorithm name as used in the Tus-Checksum-Algorithm header.
    pub fn as_str(self) -> &'static str {
        match self {
            ChecksumAlgorithm::Sha1 => "sha1",
            ChecksumAlgorithm::Sha256 => "sha256",
            ChecksumAlgorithm::Md5 => "md5",
            ChecksumAlgorithm::Crc32 => "crc32",
        }
    }
}

impl std::fmt::Display for ChecksumAlgorithm {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl std::str::FromStr for ChecksumAlgorithm {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s.to_lowercase().as_str() {
            "sha1" => Ok(ChecksumAlgorithm::Sha1),
            "sha256" => Ok(ChecksumAlgorithm::Sha256),
            "md5" => Ok(ChecksumAlgorithm::Md5),
            "crc32" => Ok(ChecksumAlgorithm::Crc32),
            other => Err(Error::UnsupportedChecksum(other.to_string())),
        }
    }
}

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

    #[test]
    fn test_supported_extensions_match_build_features() {
        let extensions = Extension::supported();

        assert!(extensions.contains(&Extension::Creation));
        assert!(extensions.contains(&Extension::ConcatenationUnfinished));

        #[cfg(feature = "checksum")]
        {
            assert!(extensions.contains(&Extension::Checksum));
            assert!(extensions.contains(&Extension::ChecksumTrailer));
        }

        #[cfg(not(feature = "checksum"))]
        {
            assert!(!extensions.contains(&Extension::Checksum));
            assert!(!extensions.contains(&Extension::ChecksumTrailer));
        }
    }

    #[test]
    fn test_default_config() {
        let config = Config::default();
        assert!(config.has_extension(Extension::Creation));
        assert!(config.has_extension(Extension::Termination));
        assert!(!config.has_extension(Extension::Checksum));
    }

    #[cfg(feature = "checksum")]
    #[test]
    fn test_builder_pattern() {
        let config = Config::new()
            .with_max_size(1024 * 1024 * 100) // 100 MB
            .with_extension(Extension::Checksum)
            .with_checksum(ChecksumAlgorithm::Sha256)
            .with_expiration(Duration::from_secs(3600))
            .with_base_path("/uploads");

        assert_eq!(config.max_size(), Some(100 * 1024 * 1024));
        assert!(config.has_extension(Extension::Checksum));
        assert!(config.has_extension(Extension::Expiration));
        assert!(config.supports_checksum_algorithm(ChecksumAlgorithm::Sha256));
        assert_eq!(config.base_path(), "/uploads");
    }

    #[cfg(not(feature = "checksum"))]
    #[test]
    #[should_panic(expected = "enable the `checksum` feature")]
    fn with_extension_panics_for_checksum_without_feature() {
        let _ = Config::new().with_extension(Extension::Checksum);
    }

    #[cfg(not(feature = "checksum"))]
    #[test]
    #[should_panic(expected = "enable the `checksum` feature")]
    fn with_extension_panics_for_checksum_trailer_without_feature() {
        let _ = Config::new().with_extension(Extension::ChecksumTrailer);
    }

    #[cfg(not(feature = "checksum"))]
    #[test]
    fn try_with_extension_errors_for_checksum_without_feature() {
        let err = Config::new()
            .try_with_extension(Extension::Checksum)
            .unwrap_err();
        assert!(matches!(err, Error::ExtensionNotSupported(_)));
    }

    #[test]
    fn try_with_extension_accepts_non_checksum_extensions() {
        let config = Config::new()
            .try_with_extension(Extension::Concatenation)
            .unwrap();
        assert!(config.has_extension(Extension::Concatenation));
    }

    #[cfg(feature = "checksum")]
    #[test]
    fn checksum_algorithms_are_returned_sorted_by_name() {
        let config = Config::new()
            .with_checksum(ChecksumAlgorithm::Sha256)
            .with_checksum(ChecksumAlgorithm::Crc32);

        let names: Vec<&str> = config
            .checksum_algorithms()
            .into_iter()
            .map(|algorithm| algorithm.as_str())
            .collect();
        assert_eq!(names, vec!["crc32", "sha1", "sha256"]);
    }

    #[test]
    fn test_extensions_string() {
        let config = Config::new()
            .with_extension(Extension::Creation)
            .with_extension(Extension::Termination);

        let exts = config.extensions_string();
        assert!(exts.contains("creation"));
        assert!(exts.contains("termination"));
    }
}