vtc_client/rooms/

mod.rs

//! Client surface for the `rooms/*` Trust Tasks.
//!
//! # What is different about these calls
//!
//! Every other method on [`crate::VtcClient`] carries an operator token: the community
//! knows who you are, and its ACL decides what you may do. **A room call carries no token
//! at all.** It carries a presentation — a membership credential and the authority chain
//! the room itself issued — and the host decides from that alone.
//!
//! That is not a convenience. It is what makes a room portable: a host that consulted its
//! own records to authorize a room operation would become part of that room's membership,
//! and the room could no longer move to a different host without reissuing credentials.
//! So [`RoomSession`] deliberately holds no session, and none of these methods reads
//! `self.token`.
//!
//! # Holding the chain
//!
//! A [`RoomSession`] carries the whole authority chain, **leaf first**, and sends all of it
//! on every call. The host never fetches a link it was not given — resolving one over the
//! network would make verification depend on availability, turn an identifier into a
//! request the host can be induced to make against an address the *caller* chooses, and
//! signal credential use to whoever hosts that identifier.
//!
//! # Agents hold less than their humans
//!
//! The case the design exists for: a member holds `read`/`write`, and equips their agent
//! with a chain one link longer whose leaf confers only `read`, expires in hours, and is
//! bound to the agent. The agent's `RoomSession` is built exactly like the member's — the
//! difference is entirely in the credentials it was handed, which is the point.

// The group-key and sealing layers live in `vti-rooms` — a VTA needs both to open a
// record on an agent's behalf, and a VTA must not depend on a VTC client. Re-exported
// under their old paths so a caller that had `vtc-client` with `mls` is unaffected.
#[cfg(feature = "mls")]
pub use vti_rooms::{mls, sealed};

use crate::{VtcClient, VtcError};

// The wire types and their Type URIs, from the crate that also stores and serves them.
//
// These were defined a second time here until the group-key layer moved out and the
// duplication became a compile error — two structs of one wire form, identical and with
// nothing checking they stayed that way, which is the drift the schema-conformance suite in
// `vti-rooms` exists to catch and could not see from over here.
pub use vti_rooms::Visibility;
pub use vti_rooms::authz::MAX_CHAIN_DEPTH;
pub use vti_rooms::wire::{
    AuthorityPresentation, CleartextContent, ListRecordsResponse, MintEpochResponse, OwnerResponse,
    PutRecordResponse, ROOMS_CREATE_TYPE, ROOMS_EPOCH_MINT_TYPE, ROOMS_OWNER_CLAIM_TYPE,
    ROOMS_OWNER_TRANSFER_TYPE, ROOMS_RECORDS_GET_TYPE, ROOMS_RECORDS_LIST_TYPE,
    ROOMS_RECORDS_PUT_TYPE, SealedContent,
};

/// A caller's standing in one room.
///
/// Holds the credentials, not a session. Build one per room per identity — a member's and
/// their agent's are different sessions against the same room, differing only in the chain
/// they carry.
#[derive(Debug, Clone)]
pub struct RoomSession {
    room_id: String,
    presentation: AuthorityPresentation,
}

impl RoomSession {
    /// Build a session from a membership credential and an authority chain.
    ///
    /// `authority` is **leaf first**: the credential being relied on comes first, and the
    /// one the room issued comes last. Rejected here if it is empty or deeper than
    /// [`MAX_CHAIN_DEPTH`], so a caller learns locally rather than from a rejected request.
    pub fn new(
        room_id: impl Into<String>,
        membership: impl Into<String>,
        authority: Vec<String>,
    ) -> Result<Self, VtcError> {
        if authority.is_empty() {
            return Err(VtcError::Url(
                "an authority chain is required: a room operation is authorized by the chain, \
                 never by a session"
                    .into(),
            ));
        }
        if authority.len() > MAX_CHAIN_DEPTH {
            return Err(VtcError::Url(format!(
                "authority chain is {} deep, exceeding the maximum of {MAX_CHAIN_DEPTH}",
                authority.len()
            )));
        }
        Ok(Self {
            room_id: room_id.into(),
            presentation: AuthorityPresentation {
                membership: membership.into(),
                authority,
                subject_binding: None,
            },
        })
    }

    /// Attach the same-subject proof a `private` room requires.
    ///
    /// Without it a private-room call is refused: two parties could otherwise pool
    /// credentials — one contributing membership, the other authority — and present as a
    /// single party holding both.
    pub fn with_subject_binding(mut self, binding: impl Into<String>) -> Self {
        self.presentation.subject_binding = Some(binding.into());
        self
    }

    /// The room this session acts on.
    pub fn room_id(&self) -> &str {
        &self.room_id
    }

    /// How many links the chain carries. Depth 1 is a grant straight from the room;
    /// depth 2 is typically a member's agent.
    pub fn chain_depth(&self) -> usize {
        self.presentation.authority.len()
    }
}

impl VtcClient {
    /// Register a room with this host.
    ///
    /// The caller brings `room_id`: a room identified by something its host chose could not
    /// move to another host without changing identity.
    pub async fn create_room(
        &self,
        room_id: &str,
        owner_did: &str,
        visibility: Visibility,
        retention_days: Option<u32>,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<serde_json::Value, VtcError> {
        let payload = serde_json::json!({
            "roomId": room_id,
            "ownerDid": owner_did,
            "visibility": visibility,
            "retentionDays": retention_days,
        });
        self.room_task(
            ROOMS_CREATE_TYPE,
            payload,
            signer_did,
            private_key_multibase,
        )
        .await
    }

    /// Write a record.
    ///
    /// Exactly one of `sealed` / `cleartext` — the host refuses the other shape for the
    /// room's tier, so passing both or neither is a request it cannot honour.
    ///
    /// `expected_version` is an optional precondition: `Some(0)` means create-only, and
    /// `Some(n)` requires the stored record to be at version `n`. A mismatch comes back
    /// carrying the current version, so a caller does not have to re-read to learn what it
    /// lost to.
    #[allow(clippy::too_many_arguments)]
    pub async fn put_record(
        &self,
        session: &RoomSession,
        key: &str,
        sealed: Option<SealedContent>,
        cleartext: Option<CleartextContent>,
        expected_version: Option<u64>,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<PutRecordResponse, VtcError> {
        let mut payload = serde_json::json!({
            "roomId": session.room_id,
            "key": key,
            "presentation": session.presentation,
        });
        if let Some(s) = sealed {
            payload["sealed"] =
                serde_json::to_value(s).map_err(|e| VtcError::Url(e.to_string()))?;
        }
        if let Some(c) = cleartext {
            payload["cleartext"] =
                serde_json::to_value(c).map_err(|e| VtcError::Url(e.to_string()))?;
        }
        if let Some(v) = expected_version {
            payload["expectedVersion"] = serde_json::json!(v);
        }
        let value = self
            .room_task(
                ROOMS_RECORDS_PUT_TYPE,
                payload,
                signer_did,
                private_key_multibase,
            )
            .await?;
        serde_json::from_value(value).map_err(|e| VtcError::Http {
            status: 200,
            body: format!("put response is not a PutRecordResponse: {e}"),
        })
    }

    /// Read one record.
    ///
    /// Presents exactly as a write does, and needs no session — which is the point on a
    /// sealed room: authorizing reads by session would hand the host a member identifier on
    /// every access, and a period of those reconstructs the membership the tier withholds.
    pub async fn get_record(
        &self,
        session: &RoomSession,
        key: &str,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<serde_json::Value, VtcError> {
        let payload = serde_json::json!({
            "roomId": session.room_id,
            "key": key,
            "presentation": session.presentation,
        });
        self.room_task(
            ROOMS_RECORDS_GET_TYPE,
            payload,
            signer_did,
            private_key_multibase,
        )
        .await
    }

    /// List record metadata.
    ///
    /// Never returns bodies — fetch the handful that matter with [`VtcClient::get_record`].
    /// `since_version` is the incremental-sync watermark, and the response **includes
    /// tombstones**: a caller that never saw a retraction would resurrect the record on its
    /// next full rebuild.
    pub async fn list_records(
        &self,
        session: &RoomSession,
        prefix: Option<&str>,
        since_version: Option<u64>,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<ListRecordsResponse, VtcError> {
        let mut payload = serde_json::json!({
            "roomId": session.room_id,
            "presentation": session.presentation,
        });
        if let Some(p) = prefix {
            payload["prefix"] = serde_json::json!(p);
        }
        if let Some(v) = since_version {
            payload["sinceVersion"] = serde_json::json!(v);
        }
        let value = self
            .room_task(
                ROOMS_RECORDS_LIST_TYPE,
                payload,
                signer_did,
                private_key_multibase,
            )
            .await?;
        serde_json::from_value(value).map_err(|e| VtcError::Http {
            status: 200,
            body: format!("list response is not a ListRecordsResponse: {e}"),
        })
    }

    /// Advance the room's key epoch — how a member is removed.
    ///
    /// Requires a chain conferring `admin`. `epoch` must be exactly one greater than the
    /// current one. The host records the number and never learns the key: distributing it
    /// to the remaining members happens out of its sight.
    pub async fn mint_epoch(
        &self,
        session: &RoomSession,
        epoch: u32,
        reason: Option<&str>,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<MintEpochResponse, VtcError> {
        let mut payload = serde_json::json!({
            "roomId": session.room_id,
            "epoch": epoch,
            "presentation": session.presentation,
        });
        if let Some(r) = reason {
            payload["reason"] = serde_json::json!(r);
        }
        let value = self
            .room_task(
                ROOMS_EPOCH_MINT_TYPE,
                payload,
                signer_did,
                private_key_multibase,
            )
            .await?;
        serde_json::from_value(value).map_err(|e| VtcError::Http {
            status: 200,
            body: format!("mint response is not a MintEpochResponse: {e}"),
        })
    }

    /// Hand the room to another member, deliberately and while still present.
    ///
    /// Requires a chain conferring `admin` — the same grant that mints epochs, since
    /// transferring is the more consequential of the two.
    ///
    /// **The host does not check that `new_owner_did` is a member**, and cannot: it holds no
    /// roster and no MLS group state. That obligation is the outgoing owner's, who can see
    /// the group. Give the room to someone who cannot commit and they inherit a room they
    /// cannot renew.
    pub async fn transfer_owner(
        &self,
        session: &RoomSession,
        new_owner_did: &str,
        reason: Option<&str>,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<OwnerResponse, VtcError> {
        let mut payload = serde_json::json!({
            "roomId": session.room_id,
            "newOwnerDid": new_owner_did,
            "presentation": session.presentation,
        });
        if let Some(r) = reason {
            payload["reason"] = serde_json::json!(r);
        }
        self.owner_task(
            ROOMS_OWNER_TRANSFER_TYPE,
            payload,
            signer_did,
            private_key_multibase,
        )
        .await
    }

    /// Claim a room whose owner has stopped renewing it.
    ///
    /// `nomination` is the succession credential the room issued to this claimant in
    /// advance. All three of the host's conditions must hold together: a valid nomination,
    /// a room that has been **dormant** past its grace window — not merely lapsed — and the
    /// claimant's own membership, which is what `session` carries.
    ///
    /// A claim does not renew the room. It hands over a dormant room, and the new owner's
    /// first act should be the epoch mint that proves they can perform it.
    pub async fn claim_owner(
        &self,
        session: &RoomSession,
        nomination: &str,
        reason: Option<&str>,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<OwnerResponse, VtcError> {
        let mut payload = serde_json::json!({
            "roomId": session.room_id,
            "nomination": nomination,
            "presentation": session.presentation,
        });
        if let Some(r) = reason {
            payload["reason"] = serde_json::json!(r);
        }
        self.owner_task(
            ROOMS_OWNER_CLAIM_TYPE,
            payload,
            signer_did,
            private_key_multibase,
        )
        .await
    }

    /// The shared tail of the two succession verbs, which answer with one shape.
    async fn owner_task(
        &self,
        type_uri: &str,
        payload: serde_json::Value,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<OwnerResponse, VtcError> {
        let value = self
            .room_task(type_uri, payload, signer_did, private_key_multibase)
            .await?;
        serde_json::from_value(value).map_err(|e| VtcError::Http {
            status: 200,
            body: format!("{type_uri} response is not an OwnerResponse: {e}"),
        })
    }

    /// Send one `rooms/*` document and return its response payload.
    ///
    /// The one place a room call is made, so the no-token property is visible in a single
    /// function rather than repeated across five: this builds a signed document and posts
    /// it, and never touches `self.token`.
    async fn room_task(
        &self,
        type_uri: &str,
        payload: serde_json::Value,
        signer_did: &str,
        private_key_multibase: &str,
    ) -> Result<serde_json::Value, VtcError> {
        let doc = vta_sdk::trust_task_sign::build_signed(
            type_uri,
            payload,
            signer_did,
            private_key_multibase,
            &self.vtc_did,
        )
        .await
        .map_err(|e| VtcError::Signing(e.to_string()))?;

        let resp = self
            .http
            .post(format!("{}/trust-tasks", self.base_url))
            .header("content-type", "application/json")
            .body(doc)
            .send()
            .await?;
        if !resp.status().is_success() {
            let status = resp.status().as_u16();
            let body = resp.text().await.unwrap_or_default();
            return Err(VtcError::Http { status, body });
        }

        let text = resp.text().await?;
        let response_doc: trust_tasks_rs::TrustTask<serde_json::Value> =
            serde_json::from_str(&text).map_err(|e| VtcError::Http {
                status: 200,
                body: format!("unexpected room response (not a Trust Task document): {e}: {text}"),
            })?;
        Ok(response_doc.payload)
    }
}

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

    #[test]
    fn a_session_requires_a_chain() {
        let err = RoomSession::new("did:key:zRoom", "vmc", vec![]).unwrap_err();
        assert!(
            format!("{err}").contains("authorized by the chain"),
            "a room session without a chain has nothing to present: {err}"
        );
    }

    #[test]
    fn a_session_refuses_a_chain_past_the_ceiling() {
        let chain: Vec<String> = (0..=MAX_CHAIN_DEPTH).map(|i| format!("vac-{i}")).collect();
        let err = RoomSession::new("did:key:zRoom", "vmc", chain).unwrap_err();
        assert!(format!("{err}").contains("exceeding the maximum"), "{err}");
    }

    /// The agent case, at the level the client models it: same construction, one more link,
    /// and the narrowing lives in the credentials rather than in any flag here.
    #[test]
    fn a_members_session_and_their_agents_differ_only_in_the_chain() {
        let member = RoomSession::new("did:key:zRoom", "vmc", vec!["vac-member".into()])
            .expect("member session");
        let agent = RoomSession::new(
            "did:key:zRoom",
            "vmc",
            vec!["vac-agent".into(), "vac-member".into()],
        )
        .expect("agent session");

        assert_eq!(member.room_id(), agent.room_id());
        assert_eq!(member.chain_depth(), 1, "a grant straight from the room");
        assert_eq!(agent.chain_depth(), 2, "one attenuation deeper");
    }

    #[test]
    fn a_subject_binding_is_attached_only_when_asked_for() {
        let s = RoomSession::new("did:key:zRoom", "vmc", vec!["vac".into()]).unwrap();
        assert!(s.presentation.subject_binding.is_none());
        let s = s.with_subject_binding("proof");
        assert_eq!(s.presentation.subject_binding.as_deref(), Some("proof"));
    }

    /// The wire shape a host reads. `camelCase`, and the binding omitted rather than null
    /// when absent — a host distinguishes absent from present-but-empty.
    #[test]
    fn a_presentation_serialises_camel_case_and_omits_an_absent_binding() {
        let s = RoomSession::new("did:key:zRoom", "vmc", vec!["a".into(), "b".into()]).unwrap();
        let v = serde_json::to_value(&s.presentation).unwrap();
        assert_eq!(v["membership"], "vmc");
        assert_eq!(v["authority"][0], "a", "leaf first");
        assert!(v.get("subjectBinding").is_none());

        let s = s.with_subject_binding("bind");
        let v = serde_json::to_value(&s.presentation).unwrap();
        assert_eq!(v["subjectBinding"], "bind");
    }

    #[test]
    fn visibility_serialises_lowercase_as_the_host_expects() {
        assert_eq!(
            serde_json::to_value(Visibility::Attributed).unwrap(),
            serde_json::json!("attributed")
        );
    }
}