cortexkit-bus-naming 0.2.0

use std::collections::BTreeSet;
use std::error::Error;
use std::fmt;

use crate::names::AccountNames;
use crate::token::{validate_token, NamingError, TokenKind};

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub enum Principal {
    Participant,
    DeliveryAuthority,
    Bus,
    System,
    /// The module that runs flows (basal): it reads the event stream.
    FlowEngine,
}

impl Principal {
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::Participant => "participant",
            Self::DeliveryAuthority => "delivery-authority",
            Self::Bus => "bus",
            Self::System => "system",
            Self::FlowEngine => "flow-engine",
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub enum Operation {
    Publish,
    Subscribe,
}

impl Operation {
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::Publish => "publish",
            Self::Subscribe => "subscribe",
        }
    }
}

/// One permission entry. The model intentionally has no deny variant.
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub struct AllowEntry {
    pub principal: Principal,
    pub operation: Operation,
    pub subject: String,
}

#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub struct RefusedEntry {
    pub principal: Principal,
    pub operation: Operation,
    pub subject: String,
    pub reason: &'static str,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct GoldenFixture {
    pub account: &'static str,
    pub module_id: &'static str,
    pub bound_agent: &'static str,
    pub foreign_agent: &'static str,
    pub bound_room: &'static str,
    pub unbound_room: &'static str,
    /// Inbox component of the system user in the golden.
    pub system_credential: &'static str,
    /// Module id, and inbox component, of the flow engine in the golden.
    pub flow_engine_module: &'static str,
    /// A module that is neither the participant nor the flow engine; the
    /// golden refuses its event subjects and its durable to both.
    pub foreign_module: &'static str,
    /// Module id, and inbox component, of the delivery authority in the
    /// golden; its ROOM durable is `m_` followed by this id.
    pub delivery_authority_module: &'static str,
}

pub const PINNED_GOLDEN_FIXTURE: GoldenFixture = GoldenFixture {
    account: "box_goldenfixture",
    module_id: "ckbus",
    bound_agent: "agent_gold_a",
    foreign_agent: "agent_gold_b",
    bound_room: "room_gold_bound",
    unbound_room: "room_gold_unbound",
    system_credential: "cksys",
    flow_engine_module: "basal",
    foreign_module: "other",
    delivery_authority_module: "prefrontal-core",
};

/// The session token in the golden's refused peer and effect subjects.
const GOLDEN_SESSION: &str = "session_gold";

/// The event name and version in the golden's refused event subjects.
const GOLDEN_EVENT: &str = "pull_request_review";
const GOLDEN_EVENT_VERSION: u32 = 1;

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PermissionDocument {
    fixture: GoldenFixture,
    allows: Vec<AllowEntry>,
    refused: Vec<RefusedEntry>,
}

impl PermissionDocument {
    pub fn allows(&self) -> &[AllowEntry] {
        &self.allows
    }

    pub fn refused(&self) -> &[RefusedEntry] {
        &self.refused
    }

    pub fn render(&self) -> String {
        let mut output = String::from(
            "# Generated by cortexkit-bus-naming; edit the generator, not this file.\n",
        );
        for (name, value) in [
            ("account", self.fixture.account),
            ("module", self.fixture.module_id),
            ("bound-agent", self.fixture.bound_agent),
            ("foreign-agent", self.fixture.foreign_agent),
            ("bound-room", self.fixture.bound_room),
            ("unbound-room", self.fixture.unbound_room),
            ("flow-engine-module", self.fixture.flow_engine_module),
            ("foreign-module", self.fixture.foreign_module),
            (
                "delivery-authority-module",
                self.fixture.delivery_authority_module,
            ),
        ] {
            output.push_str(&format!("fixture {name} {value}\n"));
        }
        output.push('\n');
        for entry in &self.allows {
            output.push_str(&format!(
                "allow {} {} {}\n",
                entry.principal.as_str(),
                entry.operation.as_str(),
                entry.subject
            ));
        }
        output.push('\n');
        for entry in &self.refused {
            output.push_str(&format!(
                "expect-refused {} {} {} {}\n",
                entry.principal.as_str(),
                entry.operation.as_str(),
                entry.subject,
                entry.reason
            ));
        }
        output
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum GrantError {
    Naming(NamingError),
    InvalidPermissionFile { line: usize, reason: String },
    MissingStreamExpansion { stream: String },
}

impl fmt::Display for GrantError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Naming(error) => error.fmt(f),
            Self::InvalidPermissionFile { line, reason } => {
                write!(f, "invalid permission file at line {line}: {reason}")
            }
            Self::MissingStreamExpansion { stream } => {
                write!(f, "permission file does not expand literal stream {stream}")
            }
        }
    }
}

impl Error for GrantError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match self {
            Self::Naming(error) => Some(error),
            _ => None,
        }
    }
}

impl From<NamingError> for GrantError {
    fn from(value: NamingError) -> Self {
        Self::Naming(value)
    }
}

/// The grant for every host and module except the delivery authority.
///
/// Credentials are account-scoped and name no agents: a participant may pull,
/// inspect and acknowledge any agent's durable on the agent streams, and which
/// durable it actually reads is decided by prefrontal-core, which owns agent
/// residence. It holds no workload publish at all: hosts and modules consume
/// wakes, peer deliveries and effect intents but never produce them.
///
/// It may publish its own module events, on `ck.{acct}.event.{module_id}.>`
/// and on no other module's event subjects.
pub fn participant_permissions(
    account: &AccountNames,
    credential_public: &str,
    module_id: &str,
    bound_rooms: &[&str],
) -> Result<Vec<AllowEntry>, GrantError> {
    let mut entries = BTreeSet::new();
    add_consumer_permissions(
        &mut entries,
        Principal::Participant,
        account,
        credential_public,
        module_id,
        bound_rooms,
    )?;
    Ok(entries.into_iter().collect())
}

/// The grant for the delivery authority, prefrontal-core alone.
///
/// Everything a participant holds, plus publish on each agent stream's own
/// binding: prefrontal-core is the only producer of wakes, peer deliveries and
/// effect intents, so it publishes every agent's wake fires and peer deliveries.
/// Keeping workload publish here, and out of every
/// host credential and out of ck-bus's own, means the module that decides a
/// delivery is the only one that can make one.
///
/// Rooms follow the same shape. prefrontal-core is the only producer and the
/// only consumer of room posts (hosts never consume rooms), so it publishes on
/// the ROOM binding `ck.{acct}.room.*.post` rather than per bound room, which
/// would re-mint its credential on every room create. It reads every room
/// through one module durable, `m_{module_id}` on the ROOM stream, filtered on
/// that binding and created by ck-bus: pull, ack and consumer info are granted
/// on that one durable by name, never with a wildcard consumer token, so it can
/// read no other consumer on ROOM, and it holds no consumer create or delete
/// there.
pub fn delivery_authority_permissions(
    account: &AccountNames,
    credential_public: &str,
    module_id: &str,
    bound_rooms: &[&str],
) -> Result<Vec<AllowEntry>, GrantError> {
    let mut entries = BTreeSet::new();
    add_consumer_permissions(
        &mut entries,
        Principal::DeliveryAuthority,
        account,
        credential_public,
        module_id,
        bound_rooms,
    )?;
    let room_stream = &account.streams().room;
    let room_durable = AccountNames::module_consumer_name(module_id)?;
    for subject in [
        account.wake_binding(),
        account.peer_binding(),
        account.effect_binding(),
        account.room_binding(),
        format!("$JS.API.CONSUMER.MSG.NEXT.{room_stream}.{room_durable}"),
        format!("$JS.API.CONSUMER.INFO.{room_stream}.{room_durable}"),
        format!("$JS.ACK.{room_stream}.{room_durable}.>"),
        format!("$JS.API.STREAM.INFO.{room_stream}"),
    ] {
        add(
            &mut entries,
            Principal::DeliveryAuthority,
            Operation::Publish,
            subject,
        );
    }
    Ok(entries.into_iter().collect())
}

/// The permissions participants and the delivery authority share: their own
/// inbox, the dead-letter record, census reads, bound rooms, publishing their
/// own module events, and reading any agent's durable on the agent streams.
fn add_consumer_permissions(
    entries: &mut BTreeSet<AllowEntry>,
    principal: Principal,
    account: &AccountNames,
    credential_public: &str,
    module_id: &str,
    bound_rooms: &[&str],
) -> Result<(), GrantError> {
    validate_token(TokenKind::CredentialPublic, credential_public)?;

    add(
        entries,
        principal,
        Operation::Subscribe,
        format!("_INBOX.{credential_public}.>"),
    );
    add(
        entries,
        principal,
        Operation::Publish,
        account.effect_dead(),
    );
    add(
        entries,
        principal,
        Operation::Publish,
        account.event_publish_grant(module_id)?,
    );

    // A whole-token `*` in the consumer position: NATS wildcards cannot match the
    // `c_` prefix, so this admits every consumer on the stream. That is safe only
    // because no non-agent durable exists on the agent streams (see
    // `StreamNames::agent_streams`).
    for stream in account.streams().agent_streams() {
        for subject in [
            format!("$JS.ACK.{stream}.*.>"),
            format!("$JS.API.CONSUMER.MSG.NEXT.{stream}.*"),
            format!("$JS.API.CONSUMER.INFO.{stream}.*"),
            format!("$JS.API.STREAM.INFO.{stream}"),
        ] {
            add(entries, principal, Operation::Publish, subject);
        }
    }

    for room_id in bound_rooms {
        validate_token(TokenKind::RoomId, room_id)?;
        add(
            entries,
            principal,
            Operation::Publish,
            account.room_post(room_id)?,
        );
        add(
            entries,
            principal,
            Operation::Subscribe,
            account.room_subscription(room_id)?,
        );
    }

    add_census_read_permissions(entries, principal, account);
    Ok(())
}

pub fn bus_permissions(
    account: &AccountNames,
    credential_public: &str,
) -> Result<Vec<AllowEntry>, GrantError> {
    validate_token(TokenKind::CredentialPublic, credential_public)?;
    let mut entries = BTreeSet::new();
    let inbox = format!("_INBOX.{credential_public}.>");
    for operation in [Operation::Publish, Operation::Subscribe] {
        add(&mut entries, Principal::Bus, operation, inbox.clone());
        add(
            &mut entries,
            Principal::Bus,
            operation,
            account.sentinel_ping(),
        );
        add(
            &mut entries,
            Principal::Bus,
            operation,
            format!("$KV.{}.>", account.buckets().census),
        );
    }
    add_census_read_permissions(&mut entries, Principal::Bus, account);

    let census_stream = &account.buckets().census_stream;
    for subject in [
        format!("$JS.API.STREAM.CREATE.{census_stream}"),
        format!("$JS.API.STREAM.UPDATE.{census_stream}"),
    ] {
        add(&mut entries, Principal::Bus, Operation::Publish, subject);
    }

    // Stream and consumer management on every stream, the event stream
    // included: the consumer-create rows are how ck-bus creates the module
    // durables `m_{module_id}` on the event and ROOM streams, as it creates the
    // agents' `c_` durables on the agent streams.
    for stream in account.streams().all() {
        for subject in [
            format!("$JS.API.STREAM.CREATE.{stream}"),
            format!("$JS.API.STREAM.UPDATE.{stream}"),
            format!("$JS.API.STREAM.INFO.{stream}"),
            format!("$JS.API.STREAM.DELETE.{stream}"),
            format!("$JS.API.CONSUMER.CREATE.{stream}.>"),
            format!("$JS.API.CONSUMER.DURABLE.CREATE.{stream}.>"),
            format!("$JS.API.CONSUMER.INFO.{stream}.>"),
            format!("$JS.API.CONSUMER.DELETE.{stream}.>"),
        ] {
            add(&mut entries, Principal::Bus, Operation::Publish, subject);
        }
    }

    let dead_stream = &account.streams().effect_dead;
    for subject in [
        format!("$JS.ACK.{dead_stream}.c_ckbus_dead.>"),
        format!("$JS.API.CONSUMER.MSG.NEXT.{dead_stream}.c_ckbus_dead"),
        format!("$JS.API.CONSUMER.INFO.{dead_stream}.c_ckbus_dead"),
    ] {
        add(&mut entries, Principal::Bus, Operation::Publish, subject);
    }

    // Agent durable lifecycle: listing the durables, and purging an agent's
    // subject when its durable is deleted (a consumer delete alone leaves its
    // messages in the stream for a later bind to redeliver). The purge filter
    // travels in the request body, which permissions cannot see, so ck-bus's
    // code restricts each purge to one agent's filter.
    for stream in account.streams().agent_streams() {
        for subject in [
            format!("$JS.API.CONSUMER.NAMES.{stream}"),
            format!("$JS.API.STREAM.PURGE.{stream}"),
        ] {
            add(&mut entries, Principal::Bus, Operation::Publish, subject);
        }
    }
    Ok(entries.into_iter().collect())
}

/// The system user's grant. It publishes claims updates, per-account claims
/// lookups (`$SYS.REQ.ACCOUNT.<account>.CLAIMS.LOOKUP`, which the revocation
/// check reads back) and the claims list (`$SYS.REQ.CLAIMS.LIST`, which finds
/// an existing account by name when its id was not recorded, so a lost state
/// file adopts the account instead of creating a second one), kicks, and
/// watches connects; replies to its requests arrive on its own
/// credential-scoped inbox.
pub fn system_permissions(credential_public: &str) -> Result<Vec<AllowEntry>, GrantError> {
    validate_token(TokenKind::CredentialPublic, credential_public)?;
    let mut entries = BTreeSet::new();
    for subject in [
        "$SYS.REQ.CLAIMS.UPDATE",
        "$SYS.REQ.CLAIMS.LIST",
        "$SYS.REQ.ACCOUNT.*.CLAIMS.LOOKUP",
        "$SYS.REQ.SERVER.*.KICK",
    ] {
        add(
            &mut entries,
            Principal::System,
            Operation::Publish,
            subject.to_owned(),
        );
    }
    for subject in [
        "$SYS.ACCOUNT.*.CONNECT".to_owned(),
        "$SYS.ACCOUNT.*.DISCONNECT".to_owned(),
        format!("_INBOX.{credential_public}.>"),
    ] {
        add(
            &mut entries,
            Principal::System,
            Operation::Subscribe,
            subject,
        );
    }
    Ok(entries.into_iter().collect())
}

/// The grant for the flow engine (basal), issued by its attested module id.
///
/// It reads module events and produces nothing: its own inbox, census reads,
/// the dead-letter record, pull and ack on its own durable `m_{module_id}` on
/// the event stream, and ephemeral ordered consumers on that stream for dry-run
/// replay. It publishes on no workload subject and on no event subject.
///
/// The ephemeral consumers rest on three rows. Consumer create is granted only
/// in its unnamed form, the bare `$JS.API.CONSUMER.CREATE.<stream>` with no
/// trailing token: a named or durable create carries the consumer name as a
/// further token and matches nothing here, so the flow engine cannot create a
/// durable, its own included (ck-bus creates that one). Consumer info on any
/// consumer of the stream lets it inspect the ephemeral consumers, whose names
/// the server picks. Publish on the stream's flow-control subjects is needed
/// because an ordered consumer that cannot answer flow control stalls without
/// an error. There is deliberately no consumer delete on the event stream, in
/// any form: the flow engine creates its ephemeral consumers with a short
/// inactivity threshold, so the server removes an abandoned one itself, and
/// without delete the flow engine cannot remove another module's durable.
pub fn flow_engine_permissions(
    account: &AccountNames,
    credential_public: &str,
    module_id: &str,
) -> Result<Vec<AllowEntry>, GrantError> {
    validate_token(TokenKind::CredentialPublic, credential_public)?;
    let durable = AccountNames::module_consumer_name(module_id)?;
    let stream = &account.streams().event;
    let mut entries = BTreeSet::new();

    add(
        &mut entries,
        Principal::FlowEngine,
        Operation::Subscribe,
        format!("_INBOX.{credential_public}.>"),
    );
    add_census_read_permissions(&mut entries, Principal::FlowEngine, account);
    for subject in [
        account.effect_dead(),
        // The flow engine's own durable, `m_{module_id}`.
        format!("$JS.API.CONSUMER.MSG.NEXT.{stream}.{durable}"),
        format!("$JS.API.CONSUMER.INFO.{stream}.{durable}"),
        format!("$JS.ACK.{stream}.{durable}.>"),
        format!("$JS.API.STREAM.INFO.{stream}"),
        // The flow engine's ephemeral ordered consumers, for dry-run replay.
        format!("$JS.API.CONSUMER.CREATE.{stream}"),
        format!("$JS.API.CONSUMER.INFO.{stream}.*"),
        format!("$JS.FC.{stream}.>"),
    ] {
        add(
            &mut entries,
            Principal::FlowEngine,
            Operation::Publish,
            subject,
        );
    }
    Ok(entries.into_iter().collect())
}

pub fn generate_permission_golden(
    fixture: GoldenFixture,
) -> Result<PermissionDocument, GrantError> {
    let account = AccountNames::derive(fixture.account)?;
    validate_token(TokenKind::ModuleId, fixture.module_id)?;
    validate_token(TokenKind::AgentId, fixture.foreign_agent)?;
    validate_token(TokenKind::RoomId, fixture.unbound_room)?;
    validate_token(TokenKind::ModuleId, fixture.foreign_module)?;
    validate_token(TokenKind::ModuleId, fixture.delivery_authority_module)?;

    let mut allows = BTreeSet::new();
    allows.extend(participant_permissions(
        &account,
        fixture.module_id,
        fixture.module_id,
        &[fixture.bound_room],
    )?);
    allows.extend(delivery_authority_permissions(
        &account,
        fixture.delivery_authority_module,
        fixture.delivery_authority_module,
        &[fixture.bound_room],
    )?);
    allows.extend(bus_permissions(&account, fixture.module_id)?);
    allows.extend(system_permissions(fixture.system_credential)?);
    allows.extend(flow_engine_permissions(
        &account,
        fixture.flow_engine_module,
        fixture.flow_engine_module,
    )?);

    let mut refused = BTreeSet::new();
    // Credentials name no agents, so no participant may produce a workload
    // message for any agent, its own or another's.
    for agent_id in [fixture.bound_agent, fixture.foreign_agent] {
        for subject in [
            account.wake_fire(agent_id)?,
            account.peer_delivery(agent_id, GOLDEN_SESSION)?,
            account.effect_intent(agent_id, GOLDEN_SESSION)?,
        ] {
            refused.insert(RefusedEntry {
                principal: Principal::Participant,
                operation: Operation::Publish,
                subject,
                reason: "workload-publish",
            });
        }
    }
    for (operation, subject, reason) in [
        (
            Operation::Publish,
            format!("$KV.{}.forbidden", account.buckets().census),
            "census-write",
        ),
        (
            Operation::Publish,
            account.room_post(fixture.unbound_room)?,
            "unbound-room",
        ),
        (
            Operation::Publish,
            "$SYS.REQ.CLAIMS.UPDATE".to_owned(),
            "system-subject",
        ),
        (
            Operation::Publish,
            account.sentinel_ping(),
            "sentinel-subject",
        ),
        (
            Operation::Publish,
            account.event_subject(fixture.foreign_module, GOLDEN_EVENT, GOLDEN_EVENT_VERSION)?,
            "foreign-module-event",
        ),
    ] {
        refused.insert(RefusedEntry {
            principal: Principal::Participant,
            operation,
            subject,
            reason,
        });
    }
    for principal in [Principal::Participant, Principal::DeliveryAuthority] {
        for stream in [
            &account.streams().room,
            &account.streams().wake,
            &account.streams().peer,
            &account.streams().effect,
        ] {
            refused.insert(RefusedEntry {
                principal,
                operation: Operation::Publish,
                subject: format!("$JS.API.CONSUMER.CREATE.{stream}.c_{}", fixture.bound_agent),
                reason: "consumer-create",
            });
        }
    }
    // The delivery authority publishes on the whole ROOM binding, so an
    // unbound room's post is not refused to it the way it is to a participant.
    for (subject, reason) in [
        (
            format!("$KV.{}.forbidden", account.buckets().census),
            "census-write",
        ),
        ("$SYS.REQ.CLAIMS.UPDATE".to_owned(), "system-subject"),
    ] {
        refused.insert(RefusedEntry {
            principal: Principal::DeliveryAuthority,
            operation: Operation::Publish,
            subject,
            reason,
        });
    }
    for principal in [Principal::Bus, Principal::System] {
        for subject in [
            account.room_post(fixture.bound_room)?,
            account.wake_fire(fixture.bound_agent)?,
            account.peer_delivery(fixture.bound_agent, GOLDEN_SESSION)?,
            account.effect_intent(fixture.bound_agent, GOLDEN_SESSION)?,
        ] {
            refused.insert(RefusedEntry {
                principal,
                operation: Operation::Publish,
                subject,
                reason: "workload-publish",
            });
        }
    }

    // The ROOM module durable is the delivery authority's alone. A participant
    // cannot read it; the delivery authority cannot read another module's
    // durable on ROOM, nor create or delete any ROOM consumer (ck-bus creates
    // its durable); the flow engine does not touch ROOM at all.
    let room_stream = &account.streams().room;
    let room_durable = AccountNames::module_consumer_name(fixture.delivery_authority_module)?;
    let foreign_room_durable = AccountNames::module_consumer_name(fixture.foreign_module)?;
    let participant_room_durable = AccountNames::module_consumer_name(fixture.module_id)?;
    let room_binding = account.room_binding();
    for (principal, subject, reason) in [
        (
            Principal::Participant,
            format!("$JS.API.CONSUMER.MSG.NEXT.{room_stream}.{room_durable}"),
            "room-durable",
        ),
        (
            Principal::Participant,
            format!("$JS.ACK.{room_stream}.{room_durable}.>"),
            "room-durable",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.MSG.NEXT.{room_stream}.{foreign_room_durable}"),
            "foreign-room-durable",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.MSG.NEXT.{room_stream}.{participant_room_durable}"),
            "foreign-room-durable",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.ACK.{room_stream}.{foreign_room_durable}.>"),
            "foreign-room-durable",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.CREATE.{room_stream}"),
            "consumer-create",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.CREATE.{room_stream}.{room_durable}.{room_binding}"),
            "named-consumer-create",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.DURABLE.CREATE.{room_stream}.{room_durable}"),
            "durable-create",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.DELETE.{room_stream}.{room_durable}"),
            "consumer-delete",
        ),
        (
            Principal::DeliveryAuthority,
            format!("$JS.API.CONSUMER.DELETE.{room_stream}.{foreign_room_durable}"),
            "consumer-delete",
        ),
        (
            Principal::FlowEngine,
            format!("$JS.API.CONSUMER.MSG.NEXT.{room_stream}.{room_durable}"),
            "room-stream",
        ),
        (
            Principal::FlowEngine,
            format!("$JS.ACK.{room_stream}.{room_durable}.>"),
            "room-stream",
        ),
        (
            Principal::FlowEngine,
            format!("$JS.API.CONSUMER.INFO.{room_stream}.{room_durable}"),
            "room-stream",
        ),
        (
            Principal::FlowEngine,
            format!("$JS.API.CONSUMER.CREATE.{room_stream}"),
            "room-stream",
        ),
        (
            Principal::FlowEngine,
            format!("$JS.API.STREAM.INFO.{room_stream}"),
            "room-stream",
        ),
        (
            Principal::FlowEngine,
            account.room_post(fixture.bound_room)?,
            "room-stream",
        ),
    ] {
        refused.insert(RefusedEntry {
            principal,
            operation: Operation::Publish,
            subject,
            reason,
        });
    }
    refused.insert(RefusedEntry {
        principal: Principal::FlowEngine,
        operation: Operation::Subscribe,
        subject: account.room_subscription(fixture.bound_room)?,
        reason: "room-stream",
    });

    // The flow engine cannot create a named or durable consumer on the event
    // stream, cannot delete any consumer there, cannot read an agent's
    // durable, and publishes no workload message.
    let event_stream = &account.streams().event;
    let own_durable = AccountNames::module_consumer_name(fixture.flow_engine_module)?;
    let foreign_durable = AccountNames::module_consumer_name(fixture.foreign_module)?;
    for (subject, reason) in [
        (
            format!("$JS.API.CONSUMER.DURABLE.CREATE.{event_stream}.{foreign_durable}"),
            "durable-create",
        ),
        (
            format!(
                "$JS.API.CONSUMER.CREATE.{event_stream}.{own_durable}.{}",
                account.event_binding()
            ),
            "named-consumer-create",
        ),
        (
            format!("$JS.API.CONSUMER.DELETE.{event_stream}.{foreign_durable}"),
            "consumer-delete",
        ),
        (
            format!("$JS.API.CONSUMER.DELETE.{event_stream}.{own_durable}"),
            "consumer-delete",
        ),
        (
            format!(
                "$JS.API.CONSUMER.MSG.NEXT.{}.{}",
                account.streams().wake,
                AccountNames::consumer_name(fixture.bound_agent)?
            ),
            "agent-durable",
        ),
        (account.wake_fire(fixture.bound_agent)?, "workload-publish"),
    ] {
        refused.insert(RefusedEntry {
            principal: Principal::FlowEngine,
            operation: Operation::Publish,
            subject,
            reason,
        });
    }

    let document = PermissionDocument {
        fixture,
        allows: allows.into_iter().collect(),
        refused: refused.into_iter().collect(),
    };
    validate_permission_file(&document.render(), &account)?;
    Ok(document)
}

/// Validates the checked-in line format and its allow-only, whole-token contract.
pub fn validate_permission_file(contents: &str, account: &AccountNames) -> Result<(), GrantError> {
    let expected_streams = account.streams().all();
    let mut expanded_streams = BTreeSet::new();
    let mut seen_entries = BTreeSet::new();

    for (zero_index, raw_line) in contents.lines().enumerate() {
        let line_number = zero_index + 1;
        let line = raw_line.trim();
        if line.is_empty() || line.starts_with('#') {
            continue;
        }
        let fields = line.split_whitespace().collect::<Vec<_>>();
        if fields
            .first()
            .is_some_and(|field| field.eq_ignore_ascii_case("deny"))
        {
            return Err(file_error(
                line_number,
                "deny entries are forbidden; absence from allow is the denial",
            ));
        }

        let subject = match fields.as_slice() {
            ["fixture", _, _] => continue,
            ["allow", principal, operation, subject] => {
                validate_principal(line_number, principal)?;
                validate_operation(line_number, operation)?;
                if !seen_entries.insert(line.to_owned()) {
                    return Err(file_error(line_number, "duplicate permission entry"));
                }
                for stream in expected_streams {
                    if subject.split('.').any(|token| token == stream) {
                        expanded_streams.insert(stream.to_owned());
                    }
                }
                *subject
            }
            ["expect-refused", principal, operation, subject, _] => {
                validate_principal(line_number, principal)?;
                validate_operation(line_number, operation)?;
                if !seen_entries.insert(line.to_owned()) {
                    return Err(file_error(line_number, "duplicate expectation entry"));
                }
                *subject
            }
            _ => {
                return Err(file_error(
                    line_number,
                    "expected fixture, allow, or expect-refused entry",
                ));
            }
        };
        validate_subject(line_number, subject)?;
    }

    for stream in expected_streams {
        if !expanded_streams.contains(stream) {
            return Err(GrantError::MissingStreamExpansion {
                stream: stream.to_owned(),
            });
        }
    }
    Ok(())
}

fn add(
    entries: &mut BTreeSet<AllowEntry>,
    principal: Principal,
    operation: Operation,
    subject: String,
) {
    entries.insert(AllowEntry {
        principal,
        operation,
        subject,
    });
}

fn add_census_read_permissions(
    entries: &mut BTreeSet<AllowEntry>,
    principal: Principal,
    account: &AccountNames,
) {
    add(
        entries,
        principal,
        Operation::Subscribe,
        format!("$KV.{}.>", account.buckets().census),
    );
    let stream = &account.buckets().census_stream;
    for subject in [
        format!("$JS.API.DIRECT.GET.{stream}.>"),
        format!("$JS.API.STREAM.MSG.GET.{stream}"),
        format!("$JS.API.STREAM.INFO.{stream}"),
        format!("$JS.API.CONSUMER.CREATE.{stream}"),
        format!("$JS.API.CONSUMER.CREATE.{stream}.>"),
        format!("$JS.API.CONSUMER.DURABLE.CREATE.{stream}.>"),
        format!("$JS.API.CONSUMER.DELETE.{stream}.>"),
    ] {
        add(entries, principal, Operation::Publish, subject);
    }
}

fn validate_principal(line: usize, principal: &str) -> Result<(), GrantError> {
    if matches!(
        principal,
        "participant" | "delivery-authority" | "bus" | "system" | "flow-engine"
    ) {
        Ok(())
    } else {
        Err(file_error(line, "unknown principal"))
    }
}

fn validate_operation(line: usize, operation: &str) -> Result<(), GrantError> {
    if matches!(operation, "publish" | "subscribe") {
        Ok(())
    } else {
        Err(file_error(line, "unknown permission operation"))
    }
}

fn validate_subject(line: usize, subject: &str) -> Result<(), GrantError> {
    if subject.contains('{') || subject.contains('}') {
        return Err(file_error(line, "template placeholders must be expanded"));
    }
    let tokens = subject.split('.').collect::<Vec<_>>();
    if tokens.iter().any(|token| token.is_empty()) {
        return Err(file_error(line, "subject contains an empty token"));
    }
    for (index, token) in tokens.iter().enumerate() {
        if token.bytes().any(|byte| byte.is_ascii_whitespace()) {
            return Err(file_error(line, "subject tokens cannot contain whitespace"));
        }
        if (token.contains('*') && *token != "*") || (token.contains('>') && *token != ">") {
            return Err(file_error(
                line,
                "wildcards must occupy a whole subject token",
            ));
        }
        if *token == ">" && index + 1 != tokens.len() {
            return Err(file_error(line, "the > wildcard must be the final token"));
        }
    }
    Ok(())
}

fn file_error(line: usize, reason: impl Into<String>) -> GrantError {
    GrantError::InvalidPermissionFile {
        line,
        reason: reason.into(),
    }
}