gstp 0.9.0

use anyhow::{Result, bail};
use bc_components::{ARID, PrivateKeys};
use bc_envelope::{Signer, prelude::*};
use bc_xid::XIDDocument;

use super::Continuation;

#[derive(Debug, Clone, PartialEq)]
pub struct SealedResponse {
    response: Response,
    sender: XIDDocument,
    // This is the continuation we're going to self-encrypt and send to the
    // peer.
    state: Option<Envelope>,
    // This is a continuation we previously received from the peer and want to
    // send back to them.
    peer_continuation: Option<Envelope>,
}

impl std::fmt::Display for SealedResponse {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "SealedResponse({}, state: {}, peer_continuation: {})",
            self.response.summary(),
            self.state
                .as_ref()
                .map_or("None".to_string(), |state| state.format_flat()),
            self.peer_continuation
                .clone()
                .map_or_else(|| "None".to_string(), |_| "Some".to_string())
        )
    }
}

impl SealedResponse {
    //
    // Success Composition
    //

    pub fn new_success(id: ARID, sender: impl AsRef<XIDDocument>) -> Self {
        Self {
            response: Response::new_success(id),
            sender: sender.as_ref().clone(),
            state: None,
            peer_continuation: None,
        }
    }

    //
    // Failure Composition
    //

    pub fn new_failure(id: ARID, sender: impl AsRef<XIDDocument>) -> Self {
        Self {
            response: Response::new_failure(id),
            sender: sender.as_ref().clone(),
            state: None,
            peer_continuation: None,
        }
    }

    /// An early failure takes place before the message has been decrypted,
    /// and therefore the ID and sender public key are not known.
    pub fn new_early_failure(sender: impl AsRef<XIDDocument>) -> Self {
        Self {
            response: Response::new_early_failure(),
            sender: sender.as_ref().clone(),
            state: None,
            peer_continuation: None,
        }
    }
}

pub trait SealedResponseBehavior: ResponseBehavior {
    //
    // Composition
    //

    /// Adds state to the request that the peer may return at some future time.
    fn with_state(self, state: impl EnvelopeEncodable) -> Self;

    fn with_optional_state(self, state: Option<impl EnvelopeEncodable>)
    -> Self;

    /// Adds a continuation we previously received from the recipient and want
    /// to send back to them.
    fn with_peer_continuation(
        self,
        peer_continuation: Option<&Envelope>,
    ) -> Self;

    //
    // Parsing
    //

    fn sender(&self) -> &XIDDocument;

    fn state(&self) -> Option<&Envelope>;

    fn peer_continuation(&self) -> Option<&Envelope>;
}

impl SealedResponseBehavior for SealedResponse {
    //
    // Composition
    //

    /// Adds state to the request that the peer may return at some future time.
    fn with_state(mut self, state: impl EnvelopeEncodable) -> Self {
        if self.response.is_ok() {
            self.state = Some(state.into_envelope());
        } else {
            panic!("Cannot set state on a failed response");
        }
        self
    }

    fn with_optional_state(
        mut self,
        state: Option<impl EnvelopeEncodable>,
    ) -> Self {
        if let Some(state) = state {
            self.with_state(state)
        } else {
            self.state = None;
            self
        }
    }

    /// Adds a continuation we previously received from the recipient and want
    /// to send back to them.
    fn with_peer_continuation(
        mut self,
        peer_continuation: Option<&Envelope>,
    ) -> Self {
        self.peer_continuation = peer_continuation.cloned();
        self
    }

    //
    // Parsing
    //

    fn sender(&self) -> &XIDDocument { self.sender.as_ref() }

    fn state(&self) -> Option<&Envelope> { self.state.as_ref() }

    fn peer_continuation(&self) -> Option<&Envelope> {
        self.peer_continuation.as_ref()
    }
}

impl ResponseBehavior for SealedResponse {
    fn with_result(mut self, result: impl EnvelopeEncodable) -> Self {
        self.response = self.response.with_result(result);
        self
    }

    /// If the result is `None`, the value of the response will be the null
    /// envelope.
    fn with_optional_result(
        mut self,
        result: Option<impl EnvelopeEncodable>,
    ) -> Self {
        self.response = self.response.with_optional_result(result);
        self
    }

    /// If no error is provided, the value of the response will be the unknown
    /// value.
    fn with_error(mut self, error: impl EnvelopeEncodable) -> Self {
        self.response = self.response.with_error(error);
        self
    }

    /// If the error is `None`, the value of the response will be the unknown
    /// value.
    fn with_optional_error(
        mut self,
        error: Option<impl EnvelopeEncodable>,
    ) -> Self {
        self.response = self.response.with_optional_error(error);
        self
    }

    fn is_ok(&self) -> bool { self.response.is_ok() }

    fn is_err(&self) -> bool { self.response.is_err() }

    fn ok(&self) -> Option<&(ARID, Envelope)> { self.response.ok() }

    fn err(&self) -> Option<&(Option<ARID>, Envelope)> { self.response.err() }

    fn id(&self) -> Option<ARID> { self.response.id() }

    fn expect_id(&self) -> ARID { self.response.expect_id() }

    fn result(&self) -> Result<&Envelope> { self.response.result() }

    fn extract_result<T>(&self) -> Result<T>
    where
        T: TryFrom<CBOR, Error = dcbor::Error> + 'static,
    {
        self.response.extract_result()
    }

    fn error(&self) -> Result<&Envelope> { self.response.error() }

    fn extract_error<T>(&self) -> Result<T>
    where
        T: TryFrom<CBOR, Error = dcbor::Error> + 'static,
    {
        self.response.extract_error()
    }
}

impl SealedResponse {
    pub fn to_envelope(
        &self,
        valid_until: Option<&Date>,
        sender: Option<&dyn Signer>,
        recipient: Option<&XIDDocument>,
    ) -> Result<Envelope> {
        let sender_continuation: Option<Envelope>;
        if let Some(state) = &self.state {
            let continuation =
                Continuation::new(state).with_optional_valid_until(valid_until);
            let sender_encryption_key =
                self.sender.encryption_key().ok_or_else(|| {
                    anyhow::anyhow!("Sender must have an encryption key")
                })?;
            sender_continuation =
                Some(continuation.to_envelope(Some(sender_encryption_key)));
        } else {
            sender_continuation = None;
        }

        let mut result = self
            .response
            .clone()
            .into_envelope()
            .add_assertion(known_values::SENDER, self.sender.to_envelope())
            .add_optional_assertion(
                known_values::SENDER_CONTINUATION,
                sender_continuation,
            )
            .add_optional_assertion(
                known_values::RECIPIENT_CONTINUATION,
                self.peer_continuation.clone(),
            );

        if let Some(sender_private_key) = sender {
            result = result.sign(sender_private_key);
        }

        if let Some(recipient) = recipient {
            let recipient_encryption_key =
                recipient.encryption_key().ok_or_else(|| {
                    anyhow::anyhow!("Recipient must have an encryption key")
                })?;
            result = result.encrypt_to_recipient(recipient_encryption_key);
        }

        Ok(result)
    }

    pub fn try_from_encrypted_envelope(
        encrypted_envelope: &Envelope,
        expected_id: Option<ARID>,
        now: Option<&Date>,
        recipient_private_key: &PrivateKeys,
    ) -> Result<Self> {
        let signed_envelope =
            encrypted_envelope.decrypt_to_recipient(recipient_private_key)?;
        let sender: XIDDocument = signed_envelope
            .try_unwrap()?
            .object_for_predicate(known_values::SENDER)?
            .try_into()?;
        let sender_verification_key =
            sender.verification_key().ok_or_else(|| {
                anyhow::anyhow!("Sender must have a verification key")
            })?;
        let response_envelope =
            signed_envelope.verify(sender_verification_key)?;
        let peer_continuation = response_envelope
            .optional_object_for_predicate(known_values::SENDER_CONTINUATION)?;
        if let Some(some_peer_continuation) = peer_continuation.clone() {
            if !some_peer_continuation.subject().is_encrypted() {
                bail!("Peer continuation must be encrypted");
            }
        }
        let encrypted_continuation = response_envelope
            .optional_object_for_predicate(
                known_values::RECIPIENT_CONTINUATION,
            )?;
        let state: Option<Envelope>;
        if let Some(encrypted_continuation) = encrypted_continuation {
            let continuation = Continuation::try_from_envelope(
                &encrypted_continuation,
                expected_id,
                now,
                Some(recipient_private_key),
            )?;
            if continuation.state().is_null() {
                state = None;
            } else {
                state = Some(continuation.state().clone());
            }
        } else {
            state = None;
        }
        let response = Response::try_from(response_envelope)?;
        Ok(Self { response, sender, state, peer_continuation })
    }
}