chore(tonic-web): include crate in top-level workspace (#648)

This PR adds the tonic-web crate to tonic's workspace members. 
Unit and integration tests should now run as part of CI runs.

tonic-web/src/config.rs

@@ -0,0 +1,168 @@
+use std::collections::{BTreeSet, HashSet};
+use std::convert::TryFrom;
+use std::time::Duration;
+
+use http::{header::HeaderName, HeaderValue};
+use tonic::body::BoxBody;
+use tonic::transport::NamedService;
+use tower_service::Service;
+
+use crate::service::GrpcWeb;
+use crate::BoxError;
+
+const DEFAULT_MAX_AGE: Duration = Duration::from_secs(24 * 60 * 60);
+
+const DEFAULT_EXPOSED_HEADERS: [&str; 2] = ["grpc-status", "grpc-message"];
+
+/// A Configuration builder for grpc_web services.
+///
+/// `Config` can be used to tweak the behavior of tonic_web services. Currently,
+/// `Config` instances only expose cors settings. However, since tonic_web is designed to work
+/// with grpc-web compliant clients only, some cors options have specific default values and not
+/// all settings are configurable.
+///
+/// ## Default values and configuration options
+///
+/// * `allow-origin`: All origins allowed by default. Configurable, but null and wildcard origins
+///    are not supported.
+/// * `allow-methods`: `[POST,OPTIONS]`. Not configurable.
+/// * `allow-headers`: Set to whatever the `OPTIONS` request carries. Not configurable.
+/// * `allow-credentials`: `true`. Configurable.
+/// * `max-age`: `86400`. Configurable.
+/// * `expose-headers`: `grpc-status,grpc-message`. Configurable but values can only be added.
+///    `grpc-status` and `grpc-message` will always be exposed.
+#[derive(Debug, Clone)]
+pub struct Config {
+    pub(crate) allowed_origins: AllowedOrigins,
+    pub(crate) exposed_headers: HashSet<HeaderName>,
+    pub(crate) max_age: Option<Duration>,
+    pub(crate) allow_credentials: bool,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) enum AllowedOrigins {
+    Any,
+    #[allow(clippy::mutable_key_type)]
+    Only(BTreeSet<HeaderValue>),
+}
+
+impl AllowedOrigins {
+    pub(crate) fn is_allowed(&self, origin: &HeaderValue) -> bool {
+        match self {
+            AllowedOrigins::Any => true,
+            AllowedOrigins::Only(origins) => origins.contains(origin),
+        }
+    }
+}
+
+impl Config {
+    pub(crate) fn new() -> Config {
+        Config {
+            allowed_origins: AllowedOrigins::Any,
+            exposed_headers: DEFAULT_EXPOSED_HEADERS
+                .iter()
+                .cloned()
+                .map(HeaderName::from_static)
+                .collect(),
+            max_age: Some(DEFAULT_MAX_AGE),
+            allow_credentials: true,
+        }
+    }
+
+    /// Allow any origin to access this resource.
+    ///
+    /// This is the default value.
+    pub fn allow_all_origins(self) -> Config {
+        Self {
+            allowed_origins: AllowedOrigins::Any,
+            ..self
+        }
+    }
+
+    /// Only allow a specific set of origins to access this resource.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// tonic_web::config().allow_origins(vec!["http://a.com", "http://b.com"]);
+    /// ```
+    pub fn allow_origins<I>(self, origins: I) -> Config
+    where
+        I: IntoIterator,
+        HeaderValue: TryFrom<I::Item>,
+    {
+        // false positive when using HeaderValue, which uses Bytes internally
+        // https://rust-lang.github.io/rust-clippy/master/index.html#mutable_key_type
+        #[allow(clippy::mutable_key_type)]
+        let origins = origins
+            .into_iter()
+            .map(|v| match TryFrom::try_from(v) {
+                Ok(uri) => uri,
+                Err(_) => panic!("invalid origin"),
+            })
+            .collect();
+
+        Self {
+            allowed_origins: AllowedOrigins::Only(origins),
+            ..self
+        }
+    }
+
+    /// Adds multiple headers to the list of exposed headers.
+    ///
+    /// Default: `grpc-status,grpc-message`. These will always be included.
+    pub fn expose_headers<I>(mut self, headers: I) -> Config
+    where
+        I: IntoIterator,
+        HeaderName: TryFrom<I::Item>,
+    {
+        let iter = headers
+            .into_iter()
+            .map(|header| match TryFrom::try_from(header) {
+                Ok(header) => header,
+                Err(_) => panic!("invalid header"),
+            });
+
+        self.exposed_headers.extend(iter);
+        self
+    }
+
+    /// Defines the maximum cache lifetime for operations allowed on this
+    /// resource.
+    ///
+    /// Default: "86400" (24 hours)
+    pub fn max_age<T: Into<Option<Duration>>>(self, max_age: T) -> Config {
+        Self {
+            max_age: max_age.into(),
+            ..self
+        }
+    }
+
+    /// If true, the `access-control-allow-credentials` will be sent.
+    ///
+    /// Default: true
+    pub fn allow_credentials(self, allow_credentials: bool) -> Config {
+        Self {
+            allow_credentials,
+            ..self
+        }
+    }
+
+    /// enable a tonic service to handle grpc-web requests with this configuration values.
+    pub fn enable<S>(&self, service: S) -> GrpcWeb<S>
+    where
+        S: Service<http::Request<hyper::Body>, Response = http::Response<BoxBody>>,
+        S: NamedService + Clone + Send + 'static,
+        S::Future: Send + 'static,
+        S::Error: Into<BoxError> + Send,
+    {
+        tracing::trace!("enabled for {}", S::NAME);
+        GrpcWeb::new(service, self.clone())
+    }
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Config::new()
+    }
+}