oxilean-kernel 0.1.2

//! Auto-generated module
//!
//! 🤖 Generated with [SplitRS](https://github.com/cool-japan/splitrs)

use crate::{Expr, Name};
use std::collections::HashMap;

/// A window iterator that yields overlapping windows of size `n`.
#[allow(dead_code)]
pub struct WindowIterator<'a, T> {
    pub(super) data: &'a [T],
    pub(super) pos: usize,
    pub(super) window: usize,
}
#[allow(dead_code)]
impl<'a, T> WindowIterator<'a, T> {
    /// Creates a new window iterator.
    pub fn new(data: &'a [T], window: usize) -> Self {
        Self {
            data,
            pos: 0,
            window,
        }
    }
}
/// A min-heap implemented as a binary heap.
#[allow(dead_code)]
pub struct MinHeap<T: Ord> {
    data: Vec<T>,
}
#[allow(dead_code)]
impl<T: Ord> MinHeap<T> {
    /// Creates a new empty min-heap.
    pub fn new() -> Self {
        Self { data: Vec::new() }
    }
    /// Inserts an element.
    pub fn push(&mut self, val: T) {
        self.data.push(val);
        self.sift_up(self.data.len() - 1);
    }
    /// Removes and returns the minimum element.
    pub fn pop(&mut self) -> Option<T> {
        if self.data.is_empty() {
            return None;
        }
        let n = self.data.len();
        self.data.swap(0, n - 1);
        let min = self.data.pop();
        if !self.data.is_empty() {
            self.sift_down(0);
        }
        min
    }
    /// Returns a reference to the minimum element.
    pub fn peek(&self) -> Option<&T> {
        self.data.first()
    }
    /// Returns the number of elements.
    pub fn len(&self) -> usize {
        self.data.len()
    }
    /// Returns `true` if empty.
    pub fn is_empty(&self) -> bool {
        self.data.is_empty()
    }
    fn sift_up(&mut self, mut i: usize) {
        while i > 0 {
            let parent = (i - 1) / 2;
            if self.data[i] < self.data[parent] {
                self.data.swap(i, parent);
                i = parent;
            } else {
                break;
            }
        }
    }
    fn sift_down(&mut self, mut i: usize) {
        let n = self.data.len();
        loop {
            let left = 2 * i + 1;
            let right = 2 * i + 2;
            let mut smallest = i;
            if left < n && self.data[left] < self.data[smallest] {
                smallest = left;
            }
            if right < n && self.data[right] < self.data[smallest] {
                smallest = right;
            }
            if smallest == i {
                break;
            }
            self.data.swap(i, smallest);
            i = smallest;
        }
    }
}
/// FFI safety level for external functions.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum FfiSafety {
    /// Safe to call from safe Rust code.
    Safe,
    /// Must be called from unsafe blocks.
    Unsafe,
    /// System call (platform-specific behavior).
    System,
}
/// A counter that can measure elapsed time between snapshots.
#[allow(dead_code)]
pub struct Stopwatch {
    start: std::time::Instant,
    splits: Vec<f64>,
}
#[allow(dead_code)]
impl Stopwatch {
    /// Creates and starts a new stopwatch.
    pub fn start() -> Self {
        Self {
            start: std::time::Instant::now(),
            splits: Vec::new(),
        }
    }
    /// Records a split time (elapsed since start).
    pub fn split(&mut self) {
        self.splits.push(self.elapsed_ms());
    }
    /// Returns total elapsed milliseconds since start.
    pub fn elapsed_ms(&self) -> f64 {
        self.start.elapsed().as_secs_f64() * 1000.0
    }
    /// Returns all recorded split times.
    pub fn splits(&self) -> &[f64] {
        &self.splits
    }
    /// Returns the number of splits.
    pub fn num_splits(&self) -> usize {
        self.splits.len()
    }
}
/// A hierarchical configuration tree.
#[allow(dead_code)]
pub struct ConfigNode {
    key: String,
    value: Option<String>,
    children: Vec<ConfigNode>,
}
#[allow(dead_code)]
impl ConfigNode {
    /// Creates a leaf config node with a value.
    pub fn leaf(key: impl Into<String>, value: impl Into<String>) -> Self {
        Self {
            key: key.into(),
            value: Some(value.into()),
            children: Vec::new(),
        }
    }
    /// Creates a section node with children.
    pub fn section(key: impl Into<String>) -> Self {
        Self {
            key: key.into(),
            value: None,
            children: Vec::new(),
        }
    }
    /// Adds a child node.
    pub fn add_child(&mut self, child: ConfigNode) {
        self.children.push(child);
    }
    /// Returns the key.
    pub fn key(&self) -> &str {
        &self.key
    }
    /// Returns the value, or `None` for section nodes.
    pub fn value(&self) -> Option<&str> {
        self.value.as_deref()
    }
    /// Returns the number of children.
    pub fn num_children(&self) -> usize {
        self.children.len()
    }
    /// Looks up a dot-separated path.
    pub fn lookup(&self, path: &str) -> Option<&str> {
        let mut parts = path.splitn(2, '.');
        let head = parts.next()?;
        let tail = parts.next();
        if head != self.key {
            return None;
        }
        match tail {
            None => self.value.as_deref(),
            Some(rest) => self.children.iter().find_map(|c| c.lookup_relative(rest)),
        }
    }
    fn lookup_relative(&self, path: &str) -> Option<&str> {
        let mut parts = path.splitn(2, '.');
        let head = parts.next()?;
        let tail = parts.next();
        if head != self.key {
            return None;
        }
        match tail {
            None => self.value.as_deref(),
            Some(rest) => self.children.iter().find_map(|c| c.lookup_relative(rest)),
        }
    }
}
/// A sparse vector: stores only non-default elements.
#[allow(dead_code)]
pub struct SparseVec<T: Default + Clone + PartialEq> {
    entries: std::collections::HashMap<usize, T>,
    default_: T,
    logical_len: usize,
}
#[allow(dead_code)]
impl<T: Default + Clone + PartialEq> SparseVec<T> {
    /// Creates a new sparse vector with logical length `len`.
    pub fn new(len: usize) -> Self {
        Self {
            entries: std::collections::HashMap::new(),
            default_: T::default(),
            logical_len: len,
        }
    }
    /// Sets element at `idx`.
    pub fn set(&mut self, idx: usize, val: T) {
        if val == self.default_ {
            self.entries.remove(&idx);
        } else {
            self.entries.insert(idx, val);
        }
    }
    /// Gets element at `idx`.
    pub fn get(&self, idx: usize) -> &T {
        self.entries.get(&idx).unwrap_or(&self.default_)
    }
    /// Returns the logical length.
    pub fn len(&self) -> usize {
        self.logical_len
    }
    /// Returns whether the collection is empty.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }
    /// Returns the number of non-default elements.
    pub fn nnz(&self) -> usize {
        self.entries.len()
    }
}
/// A simple mutable key-value store for test fixtures.
#[allow(dead_code)]
pub struct Fixture {
    data: std::collections::HashMap<String, String>,
}
#[allow(dead_code)]
impl Fixture {
    /// Creates an empty fixture.
    pub fn new() -> Self {
        Self {
            data: std::collections::HashMap::new(),
        }
    }
    /// Sets a key.
    pub fn set(&mut self, key: impl Into<String>, val: impl Into<String>) {
        self.data.insert(key.into(), val.into());
    }
    /// Gets a value.
    pub fn get(&self, key: &str) -> Option<&str> {
        self.data.get(key).map(|s| s.as_str())
    }
    /// Returns the number of entries.
    pub fn len(&self) -> usize {
        self.data.len()
    }
    /// Returns whether the collection is empty.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }
}
/// A write-once cell.
#[allow(dead_code)]
pub struct WriteOnce<T> {
    value: std::cell::Cell<Option<T>>,
}
#[allow(dead_code)]
impl<T: Copy> WriteOnce<T> {
    /// Creates an empty write-once cell.
    pub fn new() -> Self {
        Self {
            value: std::cell::Cell::new(None),
        }
    }
    /// Writes a value.  Returns `false` if already written.
    pub fn write(&self, val: T) -> bool {
        if self.value.get().is_some() {
            return false;
        }
        self.value.set(Some(val));
        true
    }
    /// Returns the value if written.
    pub fn read(&self) -> Option<T> {
        self.value.get()
    }
    /// Returns `true` if the value has been written.
    pub fn is_written(&self) -> bool {
        self.value.get().is_some()
    }
}
/// A reusable scratch buffer for path computations.
#[allow(dead_code)]
pub struct PathBuf {
    components: Vec<String>,
}
#[allow(dead_code)]
impl PathBuf {
    /// Creates a new empty path buffer.
    pub fn new() -> Self {
        Self {
            components: Vec::new(),
        }
    }
    /// Pushes a component.
    pub fn push(&mut self, comp: impl Into<String>) {
        self.components.push(comp.into());
    }
    /// Pops the last component.
    pub fn pop(&mut self) {
        self.components.pop();
    }
    /// Returns the current path as a `/`-separated string.
    pub fn as_str(&self) -> String {
        self.components.join("/")
    }
    /// Returns the depth of the path.
    pub fn depth(&self) -> usize {
        self.components.len()
    }
    /// Clears the path.
    pub fn clear(&mut self) {
        self.components.clear();
    }
}
/// Represents a rewrite rule `lhs → rhs`.
#[allow(dead_code)]
#[allow(missing_docs)]
pub struct RewriteRule {
    /// The name of the rule.
    pub name: String,
    /// A string representation of the LHS pattern.
    pub lhs: String,
    /// A string representation of the RHS.
    pub rhs: String,
    /// Whether this is a conditional rule (has side conditions).
    pub conditional: bool,
}
#[allow(dead_code)]
impl RewriteRule {
    /// Creates an unconditional rewrite rule.
    pub fn unconditional(
        name: impl Into<String>,
        lhs: impl Into<String>,
        rhs: impl Into<String>,
    ) -> Self {
        Self {
            name: name.into(),
            lhs: lhs.into(),
            rhs: rhs.into(),
            conditional: false,
        }
    }
    /// Creates a conditional rewrite rule.
    pub fn conditional(
        name: impl Into<String>,
        lhs: impl Into<String>,
        rhs: impl Into<String>,
    ) -> Self {
        Self {
            name: name.into(),
            lhs: lhs.into(),
            rhs: rhs.into(),
            conditional: true,
        }
    }
    /// Returns a textual representation.
    pub fn display(&self) -> String {
        format!("{}: {} → {}", self.name, self.lhs, self.rhs)
    }
}
/// A simple decision tree node for rule dispatching.
#[allow(dead_code)]
#[allow(missing_docs)]
pub enum DecisionNode {
    /// A leaf with an action string.
    Leaf(String),
    /// An interior node: check `key` equals `val` → `yes_branch`, else `no_branch`.
    Branch {
        key: String,
        val: String,
        yes_branch: Box<DecisionNode>,
        no_branch: Box<DecisionNode>,
    },
}
#[allow(dead_code)]
impl DecisionNode {
    /// Evaluates the decision tree with the given context.
    pub fn evaluate(&self, ctx: &std::collections::HashMap<String, String>) -> &str {
        match self {
            DecisionNode::Leaf(action) => action.as_str(),
            DecisionNode::Branch {
                key,
                val,
                yes_branch,
                no_branch,
            } => {
                let actual = ctx.get(key).map(|s| s.as_str()).unwrap_or("");
                if actual == val.as_str() {
                    yes_branch.evaluate(ctx)
                } else {
                    no_branch.evaluate(ctx)
                }
            }
        }
    }
    /// Returns the depth of the decision tree.
    pub fn depth(&self) -> usize {
        match self {
            DecisionNode::Leaf(_) => 0,
            DecisionNode::Branch {
                yes_branch,
                no_branch,
                ..
            } => 1 + yes_branch.depth().max(no_branch.depth()),
        }
    }
}
/// A fixed-size sliding window that computes a running sum.
#[allow(dead_code)]
pub struct SlidingSum {
    window: Vec<f64>,
    capacity: usize,
    pos: usize,
    sum: f64,
    count: usize,
}
#[allow(dead_code)]
impl SlidingSum {
    /// Creates a sliding sum with the given window size.
    pub fn new(capacity: usize) -> Self {
        Self {
            window: vec![0.0; capacity],
            capacity,
            pos: 0,
            sum: 0.0,
            count: 0,
        }
    }
    /// Adds a value to the window, removing the oldest if full.
    pub fn push(&mut self, val: f64) {
        let oldest = self.window[self.pos];
        self.sum -= oldest;
        self.sum += val;
        self.window[self.pos] = val;
        self.pos = (self.pos + 1) % self.capacity;
        if self.count < self.capacity {
            self.count += 1;
        }
    }
    /// Returns the current window sum.
    pub fn sum(&self) -> f64 {
        self.sum
    }
    /// Returns the window mean, or `None` if empty.
    pub fn mean(&self) -> Option<f64> {
        if self.count == 0 {
            None
        } else {
            Some(self.sum / self.count as f64)
        }
    }
    /// Returns the current window size (number of valid elements).
    pub fn count(&self) -> usize {
        self.count
    }
}
/// FFI values at runtime.
#[derive(Clone, Debug, PartialEq)]
pub enum FfiValue {
    /// Boolean value.
    Bool(bool),
    /// Unsigned integer (up to 64-bit).
    UInt(u64),
    /// Signed integer (up to 64-bit).
    Int(i64),
    /// Floating point number.
    Float(f64),
    /// String value.
    Str(String),
    /// Byte array.
    Bytes(Vec<u8>),
    /// Unit value.
    Unit,
}
impl FfiValue {
    /// Try to convert an OxiLean expression to an FFI value.
    pub fn try_from_expr(expr: &Expr, ty: &FfiType) -> Result<Self, FfiError> {
        match (expr, ty) {
            (Expr::Lit(crate::Literal::Nat(n)), FfiType::UInt64) => Ok(FfiValue::UInt(*n)),
            (Expr::Lit(crate::Literal::Nat(n)), FfiType::UInt32) => {
                if *n <= u32::MAX as u64 {
                    Ok(FfiValue::UInt(*n))
                } else {
                    Err(FfiError::ValueOutOfRange(format!(
                        "u32 range exceeded: {}",
                        n
                    )))
                }
            }
            (Expr::Lit(crate::Literal::Nat(n)), FfiType::Int64) => {
                if *n <= i64::MAX as u64 {
                    Ok(FfiValue::Int(*n as i64))
                } else {
                    Err(FfiError::ValueOutOfRange(format!(
                        "i64 range exceeded: {}",
                        n
                    )))
                }
            }
            (Expr::Lit(crate::Literal::Str(s)), FfiType::String) => Ok(FfiValue::Str(s.clone())),
            _ => Err(FfiError::TypeMismatch(format!(
                "Cannot convert {:?} to {:?}",
                expr, ty
            ))),
        }
    }
    /// Convert an FFI value to an OxiLean expression.
    pub fn to_expr(&self) -> Expr {
        match self {
            FfiValue::Bool(b) => Expr::Const(
                if *b {
                    Name::str("True")
                } else {
                    Name::str("False")
                },
                vec![],
            ),
            FfiValue::UInt(n) => Expr::Lit(crate::Literal::Nat(*n)),
            FfiValue::Int(n) => {
                if *n >= 0 {
                    Expr::Lit(crate::Literal::Nat(*n as u64))
                } else {
                    Expr::Const(Name::str("Int.neg"), vec![])
                }
            }
            FfiValue::Float(f) => Expr::Lit(crate::Literal::Str(f.to_string())),
            FfiValue::Str(s) => Expr::Lit(crate::Literal::Str(s.clone())),
            FfiValue::Bytes(bs) => Expr::Lit(crate::Literal::Str(
                bs.iter().map(|b| format!("{:02x}", b)).collect::<String>(),
            )),
            FfiValue::Unit => Expr::Sort(crate::Level::zero()),
        }
    }
}
/// A generic counter that tracks min/max/sum for statistical summaries.
#[allow(dead_code)]
pub struct StatSummary {
    count: u64,
    sum: f64,
    min: f64,
    max: f64,
}
#[allow(dead_code)]
impl StatSummary {
    /// Creates an empty summary.
    pub fn new() -> Self {
        Self {
            count: 0,
            sum: 0.0,
            min: f64::INFINITY,
            max: f64::NEG_INFINITY,
        }
    }
    /// Records a sample.
    pub fn record(&mut self, val: f64) {
        self.count += 1;
        self.sum += val;
        if val < self.min {
            self.min = val;
        }
        if val > self.max {
            self.max = val;
        }
    }
    /// Returns the mean, or `None` if no samples.
    pub fn mean(&self) -> Option<f64> {
        if self.count == 0 {
            None
        } else {
            Some(self.sum / self.count as f64)
        }
    }
    /// Returns the minimum, or `None` if no samples.
    pub fn min(&self) -> Option<f64> {
        if self.count == 0 {
            None
        } else {
            Some(self.min)
        }
    }
    /// Returns the maximum, or `None` if no samples.
    pub fn max(&self) -> Option<f64> {
        if self.count == 0 {
            None
        } else {
            Some(self.max)
        }
    }
    /// Returns the count of recorded samples.
    pub fn count(&self) -> u64 {
        self.count
    }
}
/// FFI-compatible types.
///
/// Represents types that can be marshalled across FFI boundaries.
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub enum FfiType {
    /// Boolean type (maps to C bool or Rust bool).
    Bool,
    /// 8-bit unsigned integer.
    UInt8,
    /// 16-bit unsigned integer.
    UInt16,
    /// 32-bit unsigned integer.
    UInt32,
    /// 64-bit unsigned integer.
    UInt64,
    /// 8-bit signed integer.
    Int8,
    /// 16-bit signed integer.
    Int16,
    /// 32-bit signed integer.
    Int32,
    /// 64-bit signed integer.
    Int64,
    /// 32-bit floating point.
    Float32,
    /// 64-bit floating point.
    Float64,
    /// String (null-terminated in C).
    String,
    /// Byte array.
    ByteArray,
    /// Unit type (void).
    Unit,
    /// Pointer to another type.
    Ptr(Box<FfiType>),
    /// Function pointer.
    Fn(Vec<FfiType>, Box<FfiType>),
    /// OxiLean-specific opaque type.
    OxiLean(String),
}
impl FfiType {
    /// Check if this type can be safely passed across FFI boundaries.
    pub fn is_ffi_safe(&self) -> bool {
        match self {
            FfiType::Bool
            | FfiType::UInt8
            | FfiType::UInt16
            | FfiType::UInt32
            | FfiType::UInt64
            | FfiType::Int8
            | FfiType::Int16
            | FfiType::Int32
            | FfiType::Int64
            | FfiType::Float32
            | FfiType::Float64
            | FfiType::String
            | FfiType::ByteArray
            | FfiType::Unit => true,
            FfiType::Ptr(inner) => inner.is_ffi_safe(),
            FfiType::Fn(params, ret) => params.iter().all(|t| t.is_ffi_safe()) && ret.is_ffi_safe(),
            FfiType::OxiLean(_) => false,
        }
    }
    /// Get the size in bytes of this type (if known).
    pub fn size_bytes(&self) -> Option<usize> {
        match self {
            FfiType::Bool => Some(1),
            FfiType::UInt8 | FfiType::Int8 => Some(1),
            FfiType::UInt16 | FfiType::Int16 => Some(2),
            FfiType::UInt32 | FfiType::Int32 => Some(4),
            FfiType::UInt64 | FfiType::Int64 => Some(8),
            FfiType::Float32 => Some(4),
            FfiType::Float64 => Some(8),
            FfiType::Unit => Some(0),
            FfiType::Ptr(_) => Some(std::mem::size_of::<*const ()>()),
            FfiType::String | FfiType::ByteArray => None,
            FfiType::Fn(_, _) => Some(std::mem::size_of::<*const ()>()),
            FfiType::OxiLean(_) => None,
        }
    }
}
/// A pair of `StatSummary` values tracking before/after a transformation.
#[allow(dead_code)]
pub struct TransformStat {
    before: StatSummary,
    after: StatSummary,
}
#[allow(dead_code)]
impl TransformStat {
    /// Creates a new transform stat recorder.
    pub fn new() -> Self {
        Self {
            before: StatSummary::new(),
            after: StatSummary::new(),
        }
    }
    /// Records a before value.
    pub fn record_before(&mut self, v: f64) {
        self.before.record(v);
    }
    /// Records an after value.
    pub fn record_after(&mut self, v: f64) {
        self.after.record(v);
    }
    /// Returns the mean reduction ratio (after/before).
    pub fn mean_ratio(&self) -> Option<f64> {
        let b = self.before.mean()?;
        let a = self.after.mean()?;
        if b.abs() < f64::EPSILON {
            return None;
        }
        Some(a / b)
    }
}
/// A pool of reusable string buffers.
#[allow(dead_code)]
pub struct StringPool {
    free: Vec<String>,
}
#[allow(dead_code)]
impl StringPool {
    /// Creates a new empty string pool.
    pub fn new() -> Self {
        Self { free: Vec::new() }
    }
    /// Takes a string from the pool (may be empty).
    pub fn take(&mut self) -> String {
        self.free.pop().unwrap_or_default()
    }
    /// Returns a string to the pool.
    pub fn give(&mut self, mut s: String) {
        s.clear();
        self.free.push(s);
    }
    /// Returns the number of free strings in the pool.
    pub fn free_count(&self) -> usize {
        self.free.len()
    }
}
/// A simple key-value store backed by a sorted Vec for small maps.
#[allow(dead_code)]
pub struct SmallMap<K: Ord + Clone, V: Clone> {
    entries: Vec<(K, V)>,
}
#[allow(dead_code)]
impl<K: Ord + Clone, V: Clone> SmallMap<K, V> {
    /// Creates a new empty small map.
    pub fn new() -> Self {
        Self {
            entries: Vec::new(),
        }
    }
    /// Inserts or replaces the value for `key`.
    pub fn insert(&mut self, key: K, val: V) {
        match self.entries.binary_search_by_key(&&key, |(k, _)| k) {
            Ok(i) => self.entries[i].1 = val,
            Err(i) => self.entries.insert(i, (key, val)),
        }
    }
    /// Returns the value for `key`, or `None`.
    pub fn get(&self, key: &K) -> Option<&V> {
        self.entries
            .binary_search_by_key(&key, |(k, _)| k)
            .ok()
            .map(|i| &self.entries[i].1)
    }
    /// Returns the number of entries.
    pub fn len(&self) -> usize {
        self.entries.len()
    }
    /// Returns `true` if empty.
    pub fn is_empty(&self) -> bool {
        self.entries.is_empty()
    }
    /// Returns all keys.
    pub fn keys(&self) -> Vec<&K> {
        self.entries.iter().map(|(k, _)| k).collect()
    }
    /// Returns all values.
    pub fn values(&self) -> Vec<&V> {
        self.entries.iter().map(|(_, v)| v).collect()
    }
}
/// A tagged union for representing a simple two-case discriminated union.
#[allow(dead_code)]
pub enum Either2<A, B> {
    /// The first alternative.
    First(A),
    /// The second alternative.
    Second(B),
}
#[allow(dead_code)]
impl<A, B> Either2<A, B> {
    /// Returns `true` if this is the first alternative.
    pub fn is_first(&self) -> bool {
        matches!(self, Either2::First(_))
    }
    /// Returns `true` if this is the second alternative.
    pub fn is_second(&self) -> bool {
        matches!(self, Either2::Second(_))
    }
    /// Returns the first value if present.
    pub fn first(self) -> Option<A> {
        match self {
            Either2::First(a) => Some(a),
            _ => None,
        }
    }
    /// Returns the second value if present.
    pub fn second(self) -> Option<B> {
        match self {
            Either2::Second(b) => Some(b),
            _ => None,
        }
    }
    /// Maps over the first alternative.
    pub fn map_first<C, F: FnOnce(A) -> C>(self, f: F) -> Either2<C, B> {
        match self {
            Either2::First(a) => Either2::First(f(a)),
            Either2::Second(b) => Either2::Second(b),
        }
    }
}
/// A simple directed acyclic graph.
#[allow(dead_code)]
pub struct SimpleDag {
    /// `edges[i]` is the list of direct successors of node `i`.
    edges: Vec<Vec<usize>>,
}
#[allow(dead_code)]
impl SimpleDag {
    /// Creates a DAG with `n` nodes and no edges.
    pub fn new(n: usize) -> Self {
        Self {
            edges: vec![Vec::new(); n],
        }
    }
    /// Adds an edge from `from` to `to`.
    pub fn add_edge(&mut self, from: usize, to: usize) {
        if from < self.edges.len() {
            self.edges[from].push(to);
        }
    }
    /// Returns the successors of `node`.
    pub fn successors(&self, node: usize) -> &[usize] {
        self.edges.get(node).map(|v| v.as_slice()).unwrap_or(&[])
    }
    /// Returns `true` if `from` can reach `to` via DFS.
    pub fn can_reach(&self, from: usize, to: usize) -> bool {
        let mut visited = vec![false; self.edges.len()];
        self.dfs(from, to, &mut visited)
    }
    fn dfs(&self, cur: usize, target: usize, visited: &mut Vec<bool>) -> bool {
        if cur == target {
            return true;
        }
        if cur >= visited.len() || visited[cur] {
            return false;
        }
        visited[cur] = true;
        for &next in self.successors(cur) {
            if self.dfs(next, target, visited) {
                return true;
            }
        }
        false
    }
    /// Returns the topological order of nodes, or `None` if a cycle is detected.
    pub fn topological_sort(&self) -> Option<Vec<usize>> {
        let n = self.edges.len();
        let mut in_degree = vec![0usize; n];
        for succs in &self.edges {
            for &s in succs {
                if s < n {
                    in_degree[s] += 1;
                }
            }
        }
        let mut queue: std::collections::VecDeque<usize> =
            (0..n).filter(|&i| in_degree[i] == 0).collect();
        let mut order = Vec::new();
        while let Some(node) = queue.pop_front() {
            order.push(node);
            for &s in self.successors(node) {
                if s < n {
                    in_degree[s] -= 1;
                    if in_degree[s] == 0 {
                        queue.push_back(s);
                    }
                }
            }
        }
        if order.len() == n {
            Some(order)
        } else {
            None
        }
    }
    /// Returns the number of nodes.
    pub fn num_nodes(&self) -> usize {
        self.edges.len()
    }
}
/// FFI function signature.
#[derive(Clone, Debug)]
pub struct FfiSignature {
    /// Parameter types.
    pub params: Vec<FfiType>,
    /// Return type.
    pub ret_type: Box<FfiType>,
}
impl FfiSignature {
    /// Create a new FFI signature.
    pub fn new(params: Vec<FfiType>, ret_type: Box<FfiType>) -> Self {
        FfiSignature { params, ret_type }
    }
    /// Validate the signature for FFI safety.
    pub fn validate(&self) -> Result<(), FfiError> {
        for param in &self.params {
            if !param.is_ffi_safe() {
                return Err(FfiError::InvalidSignature(format!(
                    "Unsafe parameter type: {}",
                    param
                )));
            }
        }
        if !self.ret_type.is_ffi_safe() {
            return Err(FfiError::InvalidSignature(format!(
                "Unsafe return type: {}",
                self.ret_type
            )));
        }
        Ok(())
    }
    /// Check if this signature is valid for a given expression type.
    pub fn matches_expr(&self, expr: &Expr) -> bool {
        matches!(expr, Expr::Const(_, _))
    }
}
/// A non-empty list (at least one element guaranteed).
#[allow(dead_code)]
pub struct NonEmptyVec<T> {
    head: T,
    tail: Vec<T>,
}
#[allow(dead_code)]
impl<T> NonEmptyVec<T> {
    /// Creates a non-empty vec with a single element.
    pub fn singleton(val: T) -> Self {
        Self {
            head: val,
            tail: Vec::new(),
        }
    }
    /// Pushes an element.
    pub fn push(&mut self, val: T) {
        self.tail.push(val);
    }
    /// Returns a reference to the first element.
    pub fn first(&self) -> &T {
        &self.head
    }
    /// Returns a reference to the last element.
    pub fn last(&self) -> &T {
        self.tail.last().unwrap_or(&self.head)
    }
    /// Returns the number of elements.
    pub fn len(&self) -> usize {
        1 + self.tail.len()
    }
    /// Returns whether the collection is empty.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }
    /// Returns all elements as a Vec.
    pub fn to_vec(&self) -> Vec<&T> {
        let mut v = vec![&self.head];
        v.extend(self.tail.iter());
        v
    }
}
/// A simple stack-based calculator for arithmetic expressions.
#[allow(dead_code)]
pub struct StackCalc {
    stack: Vec<i64>,
}
#[allow(dead_code)]
impl StackCalc {
    /// Creates a new empty calculator.
    pub fn new() -> Self {
        Self { stack: Vec::new() }
    }
    /// Pushes an integer literal.
    pub fn push(&mut self, n: i64) {
        self.stack.push(n);
    }
    /// Adds the top two values.  Panics if fewer than two values.
    pub fn add(&mut self) {
        let b = self
            .stack
            .pop()
            .expect("stack must have at least two values for add");
        let a = self
            .stack
            .pop()
            .expect("stack must have at least two values for add");
        self.stack.push(a + b);
    }
    /// Subtracts top from second.
    pub fn sub(&mut self) {
        let b = self
            .stack
            .pop()
            .expect("stack must have at least two values for sub");
        let a = self
            .stack
            .pop()
            .expect("stack must have at least two values for sub");
        self.stack.push(a - b);
    }
    /// Multiplies the top two values.
    pub fn mul(&mut self) {
        let b = self
            .stack
            .pop()
            .expect("stack must have at least two values for mul");
        let a = self
            .stack
            .pop()
            .expect("stack must have at least two values for mul");
        self.stack.push(a * b);
    }
    /// Peeks the top value.
    pub fn peek(&self) -> Option<i64> {
        self.stack.last().copied()
    }
    /// Returns the stack depth.
    pub fn depth(&self) -> usize {
        self.stack.len()
    }
}
/// A label set for a graph node.
#[allow(dead_code)]
pub struct LabelSet {
    labels: Vec<String>,
}
#[allow(dead_code)]
impl LabelSet {
    /// Creates a new empty label set.
    pub fn new() -> Self {
        Self { labels: Vec::new() }
    }
    /// Adds a label (deduplicates).
    pub fn add(&mut self, label: impl Into<String>) {
        let s = label.into();
        if !self.labels.contains(&s) {
            self.labels.push(s);
        }
    }
    /// Returns `true` if `label` is present.
    pub fn has(&self, label: &str) -> bool {
        self.labels.iter().any(|l| l == label)
    }
    /// Returns the count of labels.
    pub fn count(&self) -> usize {
        self.labels.len()
    }
    /// Returns all labels.
    pub fn all(&self) -> &[String] {
        &self.labels
    }
}
/// A versioned record that stores a history of values.
#[allow(dead_code)]
pub struct VersionedRecord<T: Clone> {
    history: Vec<T>,
}
#[allow(dead_code)]
impl<T: Clone> VersionedRecord<T> {
    /// Creates a new record with an initial value.
    pub fn new(initial: T) -> Self {
        Self {
            history: vec![initial],
        }
    }
    /// Updates the record with a new version.
    pub fn update(&mut self, val: T) {
        self.history.push(val);
    }
    /// Returns the current (latest) value.
    pub fn current(&self) -> &T {
        self.history
            .last()
            .expect("VersionedRecord history is always non-empty after construction")
    }
    /// Returns the value at version `n` (0-indexed), or `None`.
    pub fn at_version(&self, n: usize) -> Option<&T> {
        self.history.get(n)
    }
    /// Returns the version number of the current value.
    pub fn version(&self) -> usize {
        self.history.len() - 1
    }
    /// Returns `true` if more than one version exists.
    pub fn has_history(&self) -> bool {
        self.history.len() > 1
    }
}
/// A set of rewrite rules.
#[allow(dead_code)]
pub struct RewriteRuleSet {
    rules: Vec<RewriteRule>,
}
#[allow(dead_code)]
impl RewriteRuleSet {
    /// Creates an empty rule set.
    pub fn new() -> Self {
        Self { rules: Vec::new() }
    }
    /// Adds a rule.
    pub fn add(&mut self, rule: RewriteRule) {
        self.rules.push(rule);
    }
    /// Returns the number of rules.
    pub fn len(&self) -> usize {
        self.rules.len()
    }
    /// Returns `true` if the set is empty.
    pub fn is_empty(&self) -> bool {
        self.rules.is_empty()
    }
    /// Returns all conditional rules.
    pub fn conditional_rules(&self) -> Vec<&RewriteRule> {
        self.rules.iter().filter(|r| r.conditional).collect()
    }
    /// Returns all unconditional rules.
    pub fn unconditional_rules(&self) -> Vec<&RewriteRule> {
        self.rules.iter().filter(|r| !r.conditional).collect()
    }
    /// Looks up a rule by name.
    pub fn get(&self, name: &str) -> Option<&RewriteRule> {
        self.rules.iter().find(|r| r.name == name)
    }
}
/// External function declaration.
#[derive(Clone, Debug)]
pub struct ExternDecl {
    /// Function name in OxiLean.
    pub name: Name,
    /// Type expression of the function.
    pub type_expr: Expr,
    /// Library name (e.g., "libc", "libm").
    pub lib_name: String,
    /// C symbol name.
    pub symbol_name: String,
    /// Safety level.
    pub safety: FfiSafety,
    /// Calling convention.
    pub calling_convention: CallingConvention,
    /// FFI signature.
    pub signature: FfiSignature,
}
impl ExternDecl {
    /// Create a new external declaration.
    pub fn new(
        name: Name,
        type_expr: Expr,
        lib_name: String,
        symbol_name: String,
        safety: FfiSafety,
        calling_convention: CallingConvention,
        signature: FfiSignature,
    ) -> Self {
        ExternDecl {
            name,
            type_expr,
            lib_name,
            symbol_name,
            safety,
            calling_convention,
            signature,
        }
    }
    /// Validate this declaration.
    pub fn validate(&self) -> Result<(), FfiError> {
        self.signature.validate()?;
        if self.lib_name.is_empty() {
            return Err(FfiError::InvalidSignature(
                "Library name cannot be empty".to_string(),
            ));
        }
        if self.symbol_name.is_empty() {
            return Err(FfiError::InvalidSignature(
                "Symbol name cannot be empty".to_string(),
            ));
        }
        Ok(())
    }
}
/// Built-in external functions.
pub struct BuiltinExterns;
impl BuiltinExterns {
    /// Register built-in external functions.
    pub fn register_builtins(registry: &mut ExternRegistry) -> Result<(), FfiError> {
        Self::register_io(registry)?;
        Self::register_string(registry)?;
        Self::register_arithmetic(registry)?;
        Ok(())
    }
    /// Register I/O external functions.
    pub(crate) fn register_io(registry: &mut ExternRegistry) -> Result<(), FfiError> {
        registry.register(ExternDecl::new(
            Name::str("builtin_print"),
            Expr::Const(Name::str("String"), vec![]),
            "libc".to_string(),
            "puts".to_string(),
            FfiSafety::System,
            CallingConvention::C,
            FfiSignature::new(vec![FfiType::String], Box::new(FfiType::Int32)),
        ))?;
        registry.register(ExternDecl::new(
            Name::str("builtin_print_int"),
            Expr::Const(Name::str("Nat"), vec![]),
            "libc".to_string(),
            "printf".to_string(),
            FfiSafety::System,
            CallingConvention::C,
            FfiSignature::new(
                vec![FfiType::String, FfiType::UInt64],
                Box::new(FfiType::Int32),
            ),
        ))?;
        Ok(())
    }
    /// Register string external functions.
    pub(crate) fn register_string(registry: &mut ExternRegistry) -> Result<(), FfiError> {
        registry.register(ExternDecl::new(
            Name::str("builtin_strlen"),
            Expr::Const(Name::str("String"), vec![]),
            "libc".to_string(),
            "strlen".to_string(),
            FfiSafety::Unsafe,
            CallingConvention::C,
            FfiSignature::new(vec![FfiType::String], Box::new(FfiType::UInt64)),
        ))?;
        registry.register(ExternDecl::new(
            Name::str("builtin_strcmp"),
            Expr::Const(Name::str("String"), vec![]),
            "libc".to_string(),
            "strcmp".to_string(),
            FfiSafety::Unsafe,
            CallingConvention::C,
            FfiSignature::new(
                vec![FfiType::String, FfiType::String],
                Box::new(FfiType::Int32),
            ),
        ))?;
        Ok(())
    }
    /// Register arithmetic external functions.
    pub(crate) fn register_arithmetic(registry: &mut ExternRegistry) -> Result<(), FfiError> {
        registry.register(ExternDecl::new(
            Name::str("builtin_abs"),
            Expr::Const(Name::str("Int"), vec![]),
            "libc".to_string(),
            "abs".to_string(),
            FfiSafety::Safe,
            CallingConvention::C,
            FfiSignature::new(vec![FfiType::Int32], Box::new(FfiType::Int32)),
        ))?;
        registry.register(ExternDecl::new(
            Name::str("builtin_sqrt"),
            Expr::Const(Name::str("Float"), vec![]),
            "libm".to_string(),
            "sqrt".to_string(),
            FfiSafety::Safe,
            CallingConvention::C,
            FfiSignature::new(vec![FfiType::Float64], Box::new(FfiType::Float64)),
        ))?;
        Ok(())
    }
}
/// A version record for an external library.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct LibraryVersion {
    /// Library name.
    pub name: String,
    /// Major version.
    pub major: u32,
    /// Minor version.
    pub minor: u32,
    /// Patch version.
    pub patch: u32,
}
impl LibraryVersion {
    /// Create a new version.
    pub fn new(name: &str, major: u32, minor: u32, patch: u32) -> Self {
        Self {
            name: name.to_string(),
            major,
            minor,
            patch,
        }
    }
    /// Whether this version is at least as recent as the given version.
    pub fn at_least(&self, major: u32, minor: u32, patch: u32) -> bool {
        (self.major, self.minor, self.patch) >= (major, minor, patch)
    }
}
/// Metadata about a foreign symbol.
#[derive(Clone, Debug)]
pub struct SymbolMetadata {
    /// Symbol name.
    pub symbol: String,
    /// Library containing the symbol.
    pub library: String,
    /// Whether the symbol is weak (optional link).
    pub weak: bool,
    /// Whether the symbol is thread-local.
    pub thread_local: bool,
}
impl SymbolMetadata {
    /// Create a new symbol metadata.
    pub fn new(symbol: &str, library: &str) -> Self {
        Self {
            symbol: symbol.to_string(),
            library: library.to_string(),
            weak: false,
            thread_local: false,
        }
    }
    /// Mark this symbol as weak.
    pub fn with_weak(mut self) -> Self {
        self.weak = true;
        self
    }
    /// Mark this symbol as thread-local.
    pub fn with_thread_local(mut self) -> Self {
        self.thread_local = true;
        self
    }
}
/// A type-erased function pointer with arity tracking.
#[allow(dead_code)]
pub struct RawFnPtr {
    /// The raw function pointer (stored as usize for type erasure).
    ptr: usize,
    arity: usize,
    name: String,
}
#[allow(dead_code)]
impl RawFnPtr {
    /// Creates a new raw function pointer descriptor.
    pub fn new(ptr: usize, arity: usize, name: impl Into<String>) -> Self {
        Self {
            ptr,
            arity,
            name: name.into(),
        }
    }
    /// Returns the arity.
    pub fn arity(&self) -> usize {
        self.arity
    }
    /// Returns the name.
    pub fn name(&self) -> &str {
        &self.name
    }
    /// Returns the raw pointer value.
    pub fn raw(&self) -> usize {
        self.ptr
    }
}
/// A dependency closure builder (transitive closure via BFS).
#[allow(dead_code)]
pub struct TransitiveClosure {
    adj: Vec<Vec<usize>>,
    n: usize,
}
#[allow(dead_code)]
impl TransitiveClosure {
    /// Creates a transitive closure builder for `n` nodes.
    pub fn new(n: usize) -> Self {
        Self {
            adj: vec![Vec::new(); n],
            n,
        }
    }
    /// Adds a direct edge.
    pub fn add_edge(&mut self, from: usize, to: usize) {
        if from < self.n {
            self.adj[from].push(to);
        }
    }
    /// Computes all nodes reachable from `start` (including `start`).
    pub fn reachable_from(&self, start: usize) -> Vec<usize> {
        let mut visited = vec![false; self.n];
        let mut queue = std::collections::VecDeque::new();
        queue.push_back(start);
        while let Some(node) = queue.pop_front() {
            if node >= self.n || visited[node] {
                continue;
            }
            visited[node] = true;
            for &next in &self.adj[node] {
                queue.push_back(next);
            }
        }
        (0..self.n).filter(|&i| visited[i]).collect()
    }
    /// Returns `true` if `from` can transitively reach `to`.
    pub fn can_reach(&self, from: usize, to: usize) -> bool {
        self.reachable_from(from).contains(&to)
    }
}
/// A flat list of substitution pairs `(from, to)`.
#[allow(dead_code)]
pub struct FlatSubstitution {
    pairs: Vec<(String, String)>,
}
#[allow(dead_code)]
impl FlatSubstitution {
    /// Creates an empty substitution.
    pub fn new() -> Self {
        Self { pairs: Vec::new() }
    }
    /// Adds a pair.
    pub fn add(&mut self, from: impl Into<String>, to: impl Into<String>) {
        self.pairs.push((from.into(), to.into()));
    }
    /// Applies all substitutions to `s` (leftmost-first order).
    pub fn apply(&self, s: &str) -> String {
        let mut result = s.to_string();
        for (from, to) in &self.pairs {
            result = result.replace(from.as_str(), to.as_str());
        }
        result
    }
    /// Returns the number of pairs.
    pub fn len(&self) -> usize {
        self.pairs.len()
    }
    /// Returns `true` if empty.
    pub fn is_empty(&self) -> bool {
        self.pairs.is_empty()
    }
}
/// Registry for external function declarations.
pub struct ExternRegistry {
    /// Map from (lib_name, symbol_name) to ExternDecl.
    decls: HashMap<(String, String), ExternDecl>,
    /// Map from OxiLean name to (lib_name, symbol_name).
    name_map: HashMap<String, (String, String)>,
}
impl ExternRegistry {
    /// Create a new empty registry.
    pub fn new() -> Self {
        ExternRegistry {
            decls: HashMap::new(),
            name_map: HashMap::new(),
        }
    }
    /// Register an external function declaration.
    pub fn register(&mut self, decl: ExternDecl) -> Result<(), FfiError> {
        decl.validate()?;
        let key = (decl.lib_name.clone(), decl.symbol_name.clone());
        if self.decls.contains_key(&key) {
            return Err(FfiError::DuplicateSymbol(format!(
                "{}::{}",
                decl.lib_name, decl.symbol_name
            )));
        }
        let name_str = decl.name.to_string();
        if self.name_map.contains_key(&name_str) {
            return Err(FfiError::DuplicateSymbol(name_str));
        }
        self.name_map.insert(name_str, key.clone());
        self.decls.insert(key, decl);
        Ok(())
    }
    /// Look up a declaration by OxiLean name.
    pub fn lookup(&self, name: &Name) -> Result<&ExternDecl, FfiError> {
        let name_str = name.to_string();
        let key = self
            .name_map
            .get(&name_str)
            .ok_or_else(|| FfiError::SymbolNotFound(name_str.clone()))?;
        self.decls
            .get(key)
            .ok_or(FfiError::SymbolNotFound(name_str))
    }
    /// Look up a declaration by symbol name.
    pub fn lookup_by_symbol(
        &self,
        lib_name: &str,
        symbol_name: &str,
    ) -> Result<&ExternDecl, FfiError> {
        let key = (lib_name.to_string(), symbol_name.to_string());
        self.decls
            .get(&key)
            .ok_or_else(|| FfiError::SymbolNotFound(format!("{}::{}", lib_name, symbol_name)))
    }
    /// Validate all registered declarations.
    pub fn validate_all(&self) -> Result<(), FfiError> {
        for decl in self.decls.values() {
            decl.validate()?;
        }
        Ok(())
    }
    /// Get all registered declarations.
    pub fn all_decls(&self) -> impl Iterator<Item = &ExternDecl> {
        self.decls.values()
    }
    /// Get the number of registered declarations.
    pub fn count(&self) -> usize {
        self.decls.len()
    }
}
/// A token bucket rate limiter.
#[allow(dead_code)]
pub struct TokenBucket {
    capacity: u64,
    tokens: u64,
    refill_per_ms: u64,
    last_refill: std::time::Instant,
}
#[allow(dead_code)]
impl TokenBucket {
    /// Creates a new token bucket.
    pub fn new(capacity: u64, refill_per_ms: u64) -> Self {
        Self {
            capacity,
            tokens: capacity,
            refill_per_ms,
            last_refill: std::time::Instant::now(),
        }
    }
    /// Attempts to consume `n` tokens.  Returns `true` on success.
    pub fn try_consume(&mut self, n: u64) -> bool {
        self.refill();
        if self.tokens >= n {
            self.tokens -= n;
            true
        } else {
            false
        }
    }
    fn refill(&mut self) {
        let now = std::time::Instant::now();
        let elapsed_ms = now.duration_since(self.last_refill).as_millis() as u64;
        if elapsed_ms > 0 {
            let new_tokens = elapsed_ms * self.refill_per_ms;
            self.tokens = (self.tokens + new_tokens).min(self.capacity);
            self.last_refill = now;
        }
    }
    /// Returns the number of currently available tokens.
    pub fn available(&self) -> u64 {
        self.tokens
    }
    /// Returns the bucket capacity.
    pub fn capacity(&self) -> u64 {
        self.capacity
    }
}
/// A trie-based prefix counter.
#[allow(dead_code)]
pub struct PrefixCounter {
    children: std::collections::HashMap<char, PrefixCounter>,
    count: usize,
}
#[allow(dead_code)]
impl PrefixCounter {
    /// Creates an empty prefix counter.
    pub fn new() -> Self {
        Self {
            children: std::collections::HashMap::new(),
            count: 0,
        }
    }
    /// Records a string.
    pub fn record(&mut self, s: &str) {
        self.count += 1;
        let mut node = self;
        for c in s.chars() {
            node = node.children.entry(c).or_default();
            node.count += 1;
        }
    }
    /// Returns how many strings have been recorded that start with `prefix`.
    pub fn count_with_prefix(&self, prefix: &str) -> usize {
        let mut node = self;
        for c in prefix.chars() {
            match node.children.get(&c) {
                Some(n) => node = n,
                None => return 0,
            }
        }
        node.count
    }
}
/// A mutable reference stack for tracking the current "focus" in a tree traversal.
#[allow(dead_code)]
pub struct FocusStack<T> {
    items: Vec<T>,
}
#[allow(dead_code)]
impl<T> FocusStack<T> {
    /// Creates an empty focus stack.
    pub fn new() -> Self {
        Self { items: Vec::new() }
    }
    /// Focuses on `item`.
    pub fn focus(&mut self, item: T) {
        self.items.push(item);
    }
    /// Blurs (pops) the current focus.
    pub fn blur(&mut self) -> Option<T> {
        self.items.pop()
    }
    /// Returns the current focus, or `None`.
    pub fn current(&self) -> Option<&T> {
        self.items.last()
    }
    /// Returns the focus depth.
    pub fn depth(&self) -> usize {
        self.items.len()
    }
    /// Returns `true` if there is no current focus.
    pub fn is_empty(&self) -> bool {
        self.items.is_empty()
    }
}
/// Calling convention for external functions.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum CallingConvention {
    /// Rust calling convention.
    Rust,
    /// C calling convention (platform-dependent).
    C,
    /// System calling convention.
    System,
}
/// FFI-related errors.
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub enum FfiError {
    /// Symbol not found in registry.
    SymbolNotFound(String),
    /// Library not found.
    LibraryNotFound(String),
    /// Type mismatch in conversion.
    TypeMismatch(String),
    /// Value out of range.
    ValueOutOfRange(String),
    /// Invalid function signature.
    InvalidSignature(String),
    /// Duplicate symbol registration.
    DuplicateSymbol(String),
    /// Validation failed.
    ValidationFailed(String),
}
/// A manifest of external libraries required by a compiled OxiLean module.
#[derive(Clone, Debug, Default)]
pub struct LibraryManifest {
    /// Required libraries.
    pub entries: Vec<LibraryVersion>,
}
impl LibraryManifest {
    /// Create an empty manifest.
    pub fn new() -> Self {
        Self::default()
    }
    /// Add a required library.
    pub fn require(&mut self, lib: LibraryVersion) {
        self.entries.push(lib);
    }
    /// Check if a library (by name) is required.
    pub fn requires_lib(&self, name: &str) -> bool {
        self.entries.iter().any(|l| l.name == name)
    }
    /// Number of required libraries.
    pub fn len(&self) -> usize {
        self.entries.len()
    }
    /// Whether the manifest is empty.
    pub fn is_empty(&self) -> bool {
        self.entries.is_empty()
    }
}