vsh-runtime 0.5.0

use std::error::Error;
use std::fmt;

use vsh_commit::RecoveryReport;
use vsh_monty::ExecutionStats;
use vsh_policy::{PolicyProfile, PolicyThresholds, RiskFlag, RiskMetrics};
use vsh_store::TransactionRecord;
use vsh_types::{
    BlobId, DiffDigest, DiffEntry, HookId, IntentDigest, PolicyDigest, PrincipalId, ProgramDigest,
    ReadSetDigest, RequestEventId, RuntimeConfigDigest, SnapshotId, TransactionId,
    TransactionState, VPath, WriteSetDigest,
};
use vsh_vfs::EffectEvent;

use crate::runtime::{Receipt, RunMode, RunRequest, Runtime, RuntimeConfig, VshError};

/// Which policy-authorized commit candidates a hook may inspect.
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
pub enum HookScope {
    /// Invoke the hook only for transactions that deterministic policy escalated.
    #[default]
    ReviewRequired,
    /// Invoke the hook for every successful simulation, including read-only requests.
    AllRequests,
}

impl HookScope {
    pub(crate) const fn tag(self) -> u8 {
        match self {
            Self::ReviewRequired => 1,
            Self::AllRequests => 2,
        }
    }

    pub(crate) const fn applies_to(self, state: TransactionState) -> bool {
        match self {
            Self::ReviewRequired => matches!(state, TransactionState::PendingApproval),
            Self::AllRequests => matches!(
                state,
                TransactionState::AutoApproved | TransactionState::PendingApproval
            ),
        }
    }
}

/// Trusted, transaction-bound configuration for one commit hook.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct HookConfig {
    id: HookId,
    scope: HookScope,
    approval_ttl_ms: u64,
    max_reason_bytes: usize,
    max_content_bytes: usize,
}

impl HookConfig {
    /// Build a hook configuration from a stable host-controlled label.
    #[must_use]
    pub fn new(label: &str) -> Self {
        Self {
            id: HookId::digest_label(label),
            scope: HookScope::ReviewRequired,
            approval_ttl_ms: 5 * 60 * 1_000,
            max_reason_bytes: 16 * 1_024,
            max_content_bytes: 0,
        }
    }

    /// Select whether automatic approvals are also reviewed.
    #[must_use]
    pub const fn with_scope(mut self, scope: HookScope) -> Self {
        self.scope = scope;
        self
    }

    /// Set the bounded lifetime of approvals generated by this hook.
    #[must_use]
    pub const fn with_approval_ttl_ms(mut self, approval_ttl_ms: u64) -> Self {
        self.approval_ttl_ms = approval_ttl_ms;
        self
    }

    /// Bound the UTF-8 reason retained in a decision record.
    #[must_use]
    pub const fn with_max_reason_bytes(mut self, max_reason_bytes: usize) -> Self {
        self.max_reason_bytes = max_reason_bytes;
        self
    }

    /// Opt into bounded, immutable before/after and observed-read content evidence.
    ///
    /// Zero (the default) disables additional content capture and delivery.
    #[must_use]
    pub const fn with_max_content_bytes(mut self, maximum: usize) -> Self {
        self.max_content_bytes = maximum;
        self
    }

    /// Return the total content-byte limit for one hook event.
    #[must_use]
    pub const fn max_content_bytes(self) -> usize {
        self.max_content_bytes
    }

    /// Return the opaque hook identity.
    #[must_use]
    pub const fn id(self) -> HookId {
        self.id
    }

    /// Return the configured trigger scope.
    #[must_use]
    pub const fn scope(self) -> HookScope {
        self.scope
    }

    /// Return the hook-generated approval lifetime.
    #[must_use]
    pub const fn approval_ttl_ms(self) -> u64 {
        self.approval_ttl_ms
    }

    /// Return the maximum decision-reason size.
    #[must_use]
    pub const fn max_reason_bytes(self) -> usize {
        self.max_reason_bytes
    }

    pub(crate) fn principal(self) -> PrincipalId {
        PrincipalId::from_bytes(*self.id.as_bytes())
    }
}

impl Default for HookConfig {
    fn default() -> Self {
        Self::new("vsh.commit-hook")
    }
}

/// Deterministic policy outcome that caused a hook event.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum HookBaseline {
    /// Policy authorized the transaction without independent review.
    AutoApproved,
    /// Policy required an independent review.
    ReviewRequired,
}

/// Hash-verified bytes for one transaction-owned path/content identity.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ReviewContent {
    /// Workspace-relative path authorized for content reading.
    pub path: VPath,
    /// Immutable identity referenced by the canonical diff or an observed read.
    pub blob: BlobId,
    /// Complete bytes; partial blobs are never represented as complete evidence.
    pub bytes: Vec<u8>,
}

/// Immutable, bounded evidence supplied to a commit hook.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct RequestEvent {
    /// Event schema understood by the receiver.
    pub schema_version: u16,
    /// Stable delivery identity for idempotent handlers.
    pub event_id: RequestEventId,
    /// Stable configured hook identity.
    pub hook_id: HookId,
    /// Exact transaction that may be committed.
    pub transaction: TransactionId,
    /// State observed while preparing this event.
    pub state: TransactionState,
    /// Policy branch that caused the event.
    pub baseline: HookBaseline,
    /// Immutable base snapshot identity.
    pub base_snapshot: SnapshotId,
    /// Canonical final diff identity.
    pub diff: DiffDigest,
    /// Exact read dependency identity.
    pub read_set: ReadSetDigest,
    /// Exact write precondition identity.
    pub write_set: WriteSetDigest,
    /// Exact untrusted program identity.
    pub program: ProgramDigest,
    /// Exact deterministic policy identity.
    pub policy: PolicyDigest,
    /// Exact security-relevant runtime configuration identity.
    pub runtime_config: RuntimeConfigDigest,
    /// Optional intent identity already bound into the transaction.
    pub intent_digest: Option<IntentDigest>,
    /// Bounded raw intent when available in the artifact.
    pub intent: Option<String>,
    /// Policy profile used for the baseline decision.
    pub policy_profile: PolicyProfile,
    /// Exact policy thresholds used for the baseline decision.
    pub policy_thresholds: PolicyThresholds,
    /// Exact risk metrics evaluated by deterministic policy.
    pub risk_metrics: RiskMetrics,
    /// Stable, sorted risk flags.
    pub risk_flags: Vec<RiskFlag>,
    /// Complete path-ordered canonical diff used by commit.
    pub canonical_diff: Vec<DiffEntry>,
    /// Ordered operation-level effects, containing identities rather than file bytes.
    pub effects: Vec<EffectEvent>,
    /// Independent execution counters.
    pub execution: ExecutionStats,
    /// Whether raw review evidence survived the durable boundary.
    pub evidence_complete: bool,
    /// Whether any evidence was deliberately truncated.
    pub evidence_truncated: bool,
    /// Bounded, read-authorized content from the exact artifact, never live files.
    pub contents: Vec<ReviewContent>,
    /// Whether every canonical content side and observed content read was included.
    ///
    /// Separate from structural evidence completeness. False for missing/stamped,
    /// protected, disabled, or over-budget content.
    pub content_complete: bool,
}

/// Decision returned by a hook handler.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum HookDecision {
    /// Preserve deterministic policy: auto approvals commit; reviews remain pending.
    FollowPolicy,
    /// Approve and commit this exact transaction using the configured hook principal.
    Approve {
        /// Bounded explanation retained with the resolution.
        reason: String,
    },
    /// Keep the transaction pending and return actionable review feedback.
    Review {
        /// Bounded feedback for the caller performing the next review.
        feedback: String,
    },
    /// Terminally reject this exact transaction.
    Reject {
        /// Bounded explanation retained with the resolution.
        reason: String,
    },
}

impl HookDecision {
    /// Construct an approval with a bounded human-readable reason.
    #[must_use]
    pub fn approve(reason: impl Into<String>) -> Self {
        Self::Approve {
            reason: reason.into(),
        }
    }

    /// Construct a review requirement with a bounded human-readable reason.
    #[must_use]
    pub fn review(feedback: impl Into<String>) -> Self {
        Self::Review {
            feedback: feedback.into(),
        }
    }

    /// Construct a terminal rejection with a bounded human-readable reason.
    #[must_use]
    pub fn reject(reason: impl Into<String>) -> Self {
        Self::Reject {
            reason: reason.into(),
        }
    }
}

/// Stable normalized outcome retained next to a hook resolution.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum HookVerdict {
    /// Deterministic policy was preserved.
    FollowPolicy,
    /// The exact transaction was approved by the handler.
    Approve,
    /// The transaction remains pending with handler feedback.
    Review,
    /// The exact transaction was terminally rejected by the handler.
    Reject,
}

/// Provenance for the hook decision applied to one exact event.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct HookDecisionRecord {
    /// Exact immutable event resolved by the handler.
    pub event_id: RequestEventId,
    /// Configured handler identity bound to the event.
    pub hook_id: HookId,
    /// Normalized handler outcome.
    pub verdict: HookVerdict,
    /// Bounded explanation or review feedback supplied by the handler.
    pub reason: String,
    /// Approval principal when and only when the verdict is `Approve`.
    pub principal: Option<PrincipalId>,
}

/// Prepared commit evidence, revalidated by the runtime before resolution.
#[derive(Clone, Debug)]
pub enum CommitPreparation {
    #[doc(hidden)]
    Ready {
        transaction: TransactionId,
        state: TransactionState,
    },
    /// An external handler must decide the supplied immutable event.
    Review(Box<RequestEvent>),
}

impl CommitPreparation {
    /// Return the exact transaction represented by this preparation.
    #[must_use]
    pub const fn transaction(&self) -> TransactionId {
        match self {
            Self::Ready { transaction, .. } => *transaction,
            Self::Review(event) => event.transaction,
        }
    }

    /// Return the request event when a handler must run.
    #[must_use]
    pub fn event(&self) -> Option<&RequestEvent> {
        match self {
            Self::Ready { .. } => None,
            Self::Review(event) => Some(event.as_ref()),
        }
    }

    pub(crate) const fn prepared_state(&self) -> TransactionState {
        match self {
            Self::Ready { state, .. } => *state,
            Self::Review(event) => event.state,
        }
    }
}

/// Result of resolving a prepared commit request.
#[derive(Clone, Debug)]
pub struct CommitResolution {
    /// Current transaction receipt after applying the hook decision.
    pub receipt: Receipt,
    /// Hook provenance, or `None` when deterministic policy was followed directly.
    pub hook: Option<HookDecisionRecord>,
}

/// Contained handler failure. Runtime resolution applies fail-closed semantics first.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct HookHandlerError {
    detail: String,
}

impl HookHandlerError {
    /// Construct a contained handler failure.
    #[must_use]
    pub fn new(detail: impl Into<String>) -> Self {
        Self {
            detail: detail.into(),
        }
    }
}

impl fmt::Display for HookHandlerError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str(&self.detail)
    }
}

impl Error for HookHandlerError {}

/// Synchronous Rust hook. Async hosts should drive `prepare_commit` and
/// `resolve_commit` around their own executor instead of blocking the runtime.
pub trait CommitHook: Send + Sync {
    /// Return a decision from immutable evidence without mutating runtime state.
    ///
    /// # Errors
    ///
    /// Returns [`HookHandlerError`] when the host-owned handler cannot produce a
    /// trustworthy decision. The runtime then keeps the transaction pending.
    fn handle(&self, event: &RequestEvent) -> Result<HookDecision, HookHandlerError>;
}

impl<F> CommitHook for F
where
    F: Fn(&RequestEvent) -> Result<HookDecision, HookHandlerError> + Send + Sync,
{
    fn handle(&self, event: &RequestEvent) -> Result<HookDecision, HookHandlerError> {
        self(event)
    }
}

/// Native runtime plus a host-owned commit handler.
pub struct HookedRuntime<H> {
    runtime: Runtime,
    handler: H,
}

impl<H: CommitHook> HookedRuntime<H> {
    /// Open a runtime whose direct commit path cannot bypass this hook.
    ///
    /// # Errors
    ///
    /// Returns a typed runtime, store, snapshot, or recovery error when the
    /// configured workspace cannot be opened safely.
    pub fn open(config: RuntimeConfig, hook: HookConfig, handler: H) -> Result<Self, VshError> {
        Ok(Self {
            runtime: Runtime::open(config.with_commit_hook(hook))?,
            handler,
        })
    }

    /// Execute one transaction, invoking the handler only for auto mode candidates.
    ///
    /// # Errors
    ///
    /// Returns any simulation, handler, validation, or commit error produced while
    /// processing the exact transaction.
    pub fn run(&self, mut request: RunRequest<'_>, now_unix_ms: u64) -> Result<Receipt, VshError> {
        let mode = request.mode;
        request.mode = RunMode::Preview;
        let receipt = self.runtime.preview(request)?;
        if mode == RunMode::Auto
            && matches!(
                receipt.state,
                TransactionState::AutoApproved | TransactionState::PendingApproval
            )
        {
            return self
                .commit(receipt.transaction, now_unix_ms)
                .map(|resolution| resolution.receipt);
        }
        Ok(receipt)
    }

    /// Execute without invoking the hook or changing host files.
    ///
    /// # Errors
    ///
    /// Returns the same typed simulation failures as [`Runtime::preview`].
    pub fn preview(&self, request: RunRequest<'_>) -> Result<Receipt, VshError> {
        self.runtime.preview(request)
    }

    /// Prepare, invoke the handler without runtime locks, and resolve exactly once.
    ///
    /// # Errors
    ///
    /// Returns a typed preparation, handler, state-validation, approval, or commit
    /// error. Handler failures leave automatic approvals pending.
    pub fn commit(
        &self,
        transaction: TransactionId,
        now_unix_ms: u64,
    ) -> Result<CommitResolution, VshError> {
        let preparation = self.runtime.prepare_commit(transaction)?;
        let decision = match preparation.event() {
            Some(event) => match self.handler.handle(event) {
                Ok(decision) => decision,
                Err(source) => {
                    self.runtime.fail_hook(&preparation)?;
                    return Err(VshError::HookHandler(source));
                }
            },
            None => HookDecision::FollowPolicy,
        };
        self.runtime
            .resolve_commit(&preparation, &decision, now_unix_ms)
    }

    /// Bind an independent approval grant to a pending transaction.
    ///
    /// # Errors
    ///
    /// Returns a typed binding, lifetime, store, or state-transition error.
    pub fn approve(
        &self,
        transaction: TransactionId,
        principal: PrincipalId,
        issued_at_unix_ms: u64,
        expires_at_unix_ms: u64,
    ) -> Result<TransactionRecord, VshError> {
        self.runtime.approve(
            transaction,
            principal,
            issued_at_unix_ms,
            expires_at_unix_ms,
        )
    }

    /// Discard an uncommitted transaction artifact.
    ///
    /// # Errors
    ///
    /// Returns a typed store or artifact-retention error.
    pub fn discard_preview(&self, transaction: TransactionId) -> Result<bool, VshError> {
        self.runtime.discard_preview(transaction)
    }

    /// Recover interrupted commits found in durable state.
    ///
    /// # Errors
    ///
    /// Returns a typed recovery, host-filesystem, or store error.
    pub fn recover(&self) -> Result<RecoveryReport, VshError> {
        self.runtime.recover()
    }

    /// Load the durable record for one transaction.
    ///
    /// # Errors
    ///
    /// Returns a typed store error when the transaction is missing or corrupt.
    pub fn transaction(&self, transaction: TransactionId) -> Result<TransactionRecord, VshError> {
        self.runtime.transaction(transaction)
    }
}