grpc 0.9.0-alpha.2

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//! Definitions and implementations for call credentials (e.g. OAuth2).

use std::fmt::Debug;
use std::sync::Arc;

use tonic::async_trait;

use crate::StatusError;
use crate::attributes::Attributes;
use crate::credentials::SecurityLevel;
use crate::metadata::MetadataMap;

/// Details regarding the call, e.g. URL and method.
///
/// The fully qualified method name is constructed as:
/// `service_url` + "/" + `method_name`
pub struct CallDetails {
    service_url: String,
    method_name: String,
}

impl CallDetails {
    /// Creates a new instance containing the base URL and method name suffix
    /// (e.g., `Method` in `package.Service/Method`).
    pub fn new(service_url: impl Into<String>, method_name: impl Into<String>) -> Self {
        Self {
            service_url: service_url.into(),
            method_name: method_name.into(),
        }
    }

    /// Returns the base URL of the service for this call.
    pub fn service_url(&self) -> &str {
        &self.service_url
    }

    /// The method name suffix (e.g., `Method` in `package.Service/Method`).
    pub fn method_name(&self) -> &str {
        &self.method_name
    }
}

/// Details about a connection available to the client.
pub struct ClientConnectionSecurityInfo {
    security_protocol: &'static str,
    security_level: SecurityLevel,
    /// Stores extra data derived from the underlying protocol.
    attributes: Attributes,
}

impl ClientConnectionSecurityInfo {
    /// Constructs a new instance containing the provided security info.
    // TODO: make attributes optional by removing from the constructor?
    pub fn new(
        security_protocol: &'static str,
        security_level: SecurityLevel,
        attributes: Attributes,
    ) -> Self {
        Self {
            security_protocol,
            security_level,
            attributes,
        }
    }

    /// Returns the security protocol for the connection set by the
    /// [`ChannelCredentials`](super::ChannelCredentials).
    pub fn security_protocol(&self) -> &'static str {
        self.security_protocol
    }

    /// Returns the security level of the connection set by the
    /// [`ChannelCredentials`](super::ChannelCredentials).
    pub fn security_level(&self) -> SecurityLevel {
        self.security_level
    }

    /// Returns arbitrary data set by the
    /// [`ChannelCredentials`](super::ChannelCredentials).
    pub fn attributes(&self) -> &Attributes {
        &self.attributes
    }
}

/// A trait for credentials that need to attach security information to every
/// individual RPC (e.g., OAuth2 tokens, JWTs).
#[async_trait]
pub trait CallCredentials: Send + Sync + Debug {
    /// Generates the authentication metadata for a specific call.
    ///
    /// This method is called by the transport layer on each request.
    /// Implementations should populate the provided `metadata` map with the
    /// necessary authorization headers (e.g., `authorization: Bearer <token>`).
    ///
    /// If this returns an `Err`, the RPC will fail immediately with a status
    /// derived from the error if the status code is in the range defined in
    /// gRFC A54. Otherwise, the RPC is failed with an internal status.
    ///
    /// # Cancellation Safety
    ///
    /// Implementations of this method must be cancel safe as the future may be
    /// dropped due to RPC timeouts.
    async fn get_metadata(
        &self,
        call_details: &CallDetails,
        auth_info: &ClientConnectionSecurityInfo,
        metadata: &mut MetadataMap,
    ) -> Result<(), StatusError>;

    /// Indicates the minimum transport security level required to send
    /// these credentials.
    ///
    /// **Default:** Returns [`SecurityLevel::PrivacyAndIntegrity`].
    fn minimum_channel_security_level(&self) -> SecurityLevel {
        SecurityLevel::PrivacyAndIntegrity
    }
}

/// A composite implementation of [`CallCredentials`] that combines
/// multiple credentials.
///
/// The inner credentials are invoked sequentially during metadata retrieval.
#[derive(Debug)]
pub struct CompositeCallCredentials {
    creds: Vec<Arc<dyn CallCredentials>>,
}

impl CompositeCallCredentials {
    /// Creates a new [`CompositeCallCredentials`] with the first two credentials.
    pub fn new(first: Arc<dyn CallCredentials>, second: Arc<dyn CallCredentials>) -> Self {
        Self {
            creds: vec![first, second],
        }
    }

    /// Adds an additional [`CallCredentials`] to the composite.
    pub fn with_call_credentials(mut self, creds: Arc<dyn CallCredentials>) -> Self {
        self.creds.push(creds);
        self
    }
}

#[async_trait]
impl CallCredentials for CompositeCallCredentials {
    async fn get_metadata(
        &self,
        call_details: &CallDetails,
        auth_info: &ClientConnectionSecurityInfo,
        metadata: &mut MetadataMap,
    ) -> Result<(), StatusError> {
        for cred in &self.creds {
            cred.get_metadata(call_details, auth_info, metadata).await?;
        }
        Ok(())
    }

    fn minimum_channel_security_level(&self) -> SecurityLevel {
        self.creds
            .iter()
            .map(|c| c.minimum_channel_security_level())
            .max()
            .expect("CompositeCallCredentials must hold at least two children.")
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::metadata::AsciiMetadataKey;
    use crate::metadata::AsciiMetadataValue;

    #[derive(Debug)]
    struct MockCallCredentials {
        key: String,
        value: String,
        security_level: SecurityLevel,
    }

    #[async_trait]
    impl CallCredentials for MockCallCredentials {
        async fn get_metadata(
            &self,
            _call_details: &CallDetails,
            _auth_info: &ClientConnectionSecurityInfo,
            metadata: &mut MetadataMap,
        ) -> Result<(), StatusError> {
            metadata.insert(
                self.key.parse::<AsciiMetadataKey>().unwrap(),
                AsciiMetadataValue::try_from(&self.value).unwrap(),
            );
            Ok(())
        }

        fn minimum_channel_security_level(&self) -> SecurityLevel {
            self.security_level
        }
    }

    #[tokio::test]
    async fn test_composite_call_credentials() {
        let cred1 = Arc::new(MockCallCredentials {
            key: "key1".to_string(),
            value: "value1".to_string(),
            security_level: SecurityLevel::IntegrityOnly,
        });
        let cred2 = Arc::new(MockCallCredentials {
            key: "key2".to_string(),
            value: "value2".to_string(),
            security_level: SecurityLevel::PrivacyAndIntegrity,
        });

        let composite = CompositeCallCredentials::new(cred1, cred2);

        let call_details = CallDetails {
            service_url: "url".to_string(),
            method_name: "method".to_string(),
        };
        let auth_info = ClientConnectionSecurityInfo::new(
            "test",
            SecurityLevel::PrivacyAndIntegrity,
            Attributes::new(),
        );
        let mut metadata = MetadataMap::new();

        composite
            .get_metadata(&call_details, &auth_info, &mut metadata)
            .await
            .unwrap();

        assert_eq!(metadata.get("key1").unwrap(), "value1");
        assert_eq!(metadata.get("key2").unwrap(), "value2");
        assert_eq!(
            composite.minimum_channel_security_level(),
            SecurityLevel::PrivacyAndIntegrity
        );
    }
}