kaynine-runtime 0.1.0

//! Default decision chain (SPEC §8.3 决策优先级): 硬拒绝 → grants → session →
//! product → default. v0.1 delivers the combinator plus the grant layer; the
//! session layer is an empty placeholder (documented plan simplification) and
//! the product/default layers are closures the host supplies as ordinary
//! `Policy` implementations stacked into the chain.

use kaynine_core::error::PolicyError;
use kaynine_core::policy::{Decision, Policy, PolicyRequest};
use kaynine_core::store::SessionStore;
use std::sync::Arc;

/// Ordered policy combinator: layers are evaluated in priority order
/// (hard-deny first). Any `Deny` short-circuits immediately; otherwise the
/// first `Ask` is remembered while later layers keep running (a later Deny
/// still wins — deny beats ask); if no layer denies, the first Ask wins; all
/// Allow → Allow.
pub struct PolicyChain {
    pub layers: Vec<Arc<dyn Policy>>,
}

impl PolicyChain {
    pub fn new(layers: Vec<Arc<dyn Policy>>) -> Self {
        Self { layers }
    }
}

#[async_trait::async_trait]
impl Policy for PolicyChain {
    async fn evaluate(&self, request: PolicyRequest) -> Result<Decision, PolicyError> {
        let mut first_ask: Option<Decision> = None;
        for layer in &self.layers {
            match layer.evaluate(request.clone()).await? {
                Decision::Deny { reason } => return Ok(Decision::Deny { reason }),
                Decision::Ask => {
                    first_ask.get_or_insert(Decision::Ask);
                }
                Decision::Allow => {}
            }
        }
        Ok(first_ask.unwrap_or(Decision::Allow))
    }
}

/// Grant layer: reads the session store's persisted `policy_grants` rows for
/// the namespace and matches them against the call's declared capabilities by
/// serialized equality (Capability 全等; path/origin wildcards are deferred to
/// product closures). A match grants Allow; no match defers to later layers
/// with Ask.
///
/// Grant payload contract:
/// `{"grant_id": "...", "namespace": "...", "capability": <Capability serde>}`
pub struct GrantPolicy {
    pub store: Arc<dyn SessionStore>,
    pub namespace: String,
}

#[async_trait::async_trait]
impl Policy for GrantPolicy {
    async fn evaluate(&self, request: PolicyRequest) -> Result<Decision, PolicyError> {
        let grants = self
            .store
            .list_grants(&self.namespace)
            .await
            .map_err(|e| PolicyError::Evaluate(e.to_string()))?;
        let call_caps: Vec<serde_json::Value> = request
            .call
            .capabilities
            .iter()
            .map(serde_json::to_value)
            .collect::<Result<_, _>>()
            .map_err(|e| PolicyError::Evaluate(e.to_string()))?;
        for grant in &grants {
            let Some(granted) = grant.get("capability") else {
                continue;
            };
            if call_caps.iter().any(|cap| cap == granted) {
                return Ok(Decision::Allow);
            }
        }
        // No persisted grant: defer to the next layer (typically Ask).
        Ok(Decision::Ask)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use kaynine_core::ids::{RunId, SessionId, ToolCallId};
    use kaynine_core::policy::DenyAllPolicy;
    use kaynine_core::store::SessionStore;
    use kaynine_core::testing::ScriptedPolicy;
    use kaynine_core::tool::{Capability, PreparedToolCall};
    use kaynine_store::sqlite::SqliteStore;
    use std::collections::VecDeque;
    use std::sync::Mutex;

    struct FixedPolicy(Decision);

    #[async_trait::async_trait]
    impl Policy for FixedPolicy {
        async fn evaluate(&self, _request: PolicyRequest) -> Result<Decision, PolicyError> {
            Ok(self.0.clone())
        }
    }

    fn request_with_caps(caps: Vec<Capability>) -> PolicyRequest {
        PolicyRequest {
            call: PreparedToolCall {
                call_id: ToolCallId::from("call-1"),
                name: "bash".into(),
                arguments: serde_json::json!({}),
                capabilities: caps,
            },
            session_id: SessionId::from("s"),
            run_id: RunId::from("r"),
            turn: 1,
        }
    }

    #[tokio::test]
    async fn policy_chain_priority() {
        // Hard-deny beats ask.
        let chain = PolicyChain::new(vec![
            Arc::new(FixedPolicy(Decision::Ask)),
            Arc::new(DenyAllPolicy {
                reason: "机密".into(),
            }),
        ]);
        assert_eq!(
            chain.evaluate(request_with_caps(vec![])).await.unwrap(),
            Decision::Deny {
                reason: "机密".into()
            }
        );

        // Ask beats allow (first ask wins, later allows do not override).
        let chain = PolicyChain::new(vec![
            Arc::new(FixedPolicy(Decision::Allow)),
            Arc::new(FixedPolicy(Decision::Ask)),
            Arc::new(FixedPolicy(Decision::Allow)),
        ]);
        assert_eq!(
            chain.evaluate(request_with_caps(vec![])).await.unwrap(),
            Decision::Ask
        );

        // All allow → Allow.
        let chain = PolicyChain::new(vec![
            Arc::new(FixedPolicy(Decision::Allow)),
            Arc::new(FixedPolicy(Decision::Allow)),
        ]);
        assert_eq!(
            chain.evaluate(request_with_caps(vec![])).await.unwrap(),
            Decision::Allow
        );
    }

    #[tokio::test]
    async fn policy_chain_defers_to_scripted_order() {
        // ScriptedPolicy pops per evaluate; chain must evaluate layers in order.
        let script = ScriptedPolicy {
            decisions: Mutex::new(VecDeque::from(vec![Decision::Ask])),
        };
        let chain = PolicyChain::new(vec![
            Arc::new(script),
            Arc::new(FixedPolicy(Decision::Allow)),
        ]);
        assert_eq!(
            chain.evaluate(request_with_caps(vec![])).await.unwrap(),
            Decision::Ask
        );
    }

    async fn store_with_grant(capability: &Capability) -> Arc<SqliteStore> {
        let path =
            std::env::temp_dir().join(format!("kaynine-grant-test-{}.db", uuid::Uuid::new_v4()));
        let store = SqliteStore::open(&path).expect("open store");
        store.migrate().await.expect("migrate");
        store
            .insert_grant(
                "grant-1",
                "prod",
                serde_json::json!({
                    "grant_id": "grant-1",
                    "namespace": "prod",
                    "capability": capability,
                }),
            )
            .await
            .expect("insert grant");
        // Leak the path: the temp file is cleaned up by the OS; tests are
        // short-lived.
        Arc::new(store)
    }

    #[tokio::test]
    async fn grant_policy_allows_matched_capability() {
        let cap = Capability::FileRead {
            path: "/tmp/data".into(),
        };
        let store = store_with_grant(&cap).await;
        let policy = GrantPolicy {
            store: store as Arc<dyn SessionStore>,
            namespace: "prod".into(),
        };

        // Matched → Allow.
        assert_eq!(
            policy
                .evaluate(request_with_caps(vec![
                    Capability::NetworkAccess {
                        origin: "example.com".into()
                    },
                    cap.clone()
                ]))
                .await
                .unwrap(),
            Decision::Allow
        );

        // Unmatched → Ask (defers to later layers).
        assert_eq!(
            policy
                .evaluate(request_with_caps(vec![Capability::FileWrite {
                    path: "/tmp/data".into()
                }]))
                .await
                .unwrap(),
            Decision::Ask
        );
    }
}