llvm-native-core 0.1.15

//! LLVM User — a Value that references other Values as operands.
//! Clean-room behavioral reconstruction. Phase 1 — LLVM.IR.1 Court.
//!
//! In LLVM C++, `User` is the base class for everything that holds
//! references to other Values (operands). This includes Instructions,
//! Constants, and GlobalValues. The User manages an array of operand
//! references (use-list entries).
//!
//! In this Rust implementation, `User` wraps a `ValueRef` and provides
//! a clean operand management interface, coordinating with the Value's
//! internal operand storage and use-def chains.

use crate::types::Type;
use crate::value::{valref, SubclassKind, Use, Value, ValueRef, WeakValueRef};
use std::cell::RefCell;
use std::collections::HashMap;
use std::rc::{Rc, Weak};

/// A User of other Values — holds operands and manages the use-def chain
/// so that each operand knows it is "used" by this User.
#[derive(Debug, Clone)]
pub struct User {
    /// The backing Value that this User wraps.
    pub value: ValueRef,
}

impl User {
    /// Create a new User with the given type, ID, and name.
    pub fn new(ty: Type, vid: u64, name: String) -> Self {
        let mut v = Value::new(ty).named(name).with_subclass(SubclassKind::User);
        v.vid = vid;
        Self { value: valref(v) }
    }

    /// Create a User from an existing ValueRef.
    pub fn from_value(val: ValueRef) -> Self {
        Self { value: val }
    }

    /// Create a new User with a given name (auto-generates vid).
    pub fn named(name: &str, ty: Type) -> Self {
        let v = Value::new(ty).named(name).with_subclass(SubclassKind::User);
        Self { value: valref(v) }
    }

    // -------------------------------------------------------------------
    // Operand access
    // -------------------------------------------------------------------

    /// Get the operand at position `idx`, or None if out of bounds.
    pub fn get_operand(&self, idx: usize) -> Option<ValueRef> {
        self.value.borrow().operand(idx)
    }

    /// Get the total number of operands.
    pub fn get_num_operands(&self) -> usize {
        self.value.borrow().get_num_operands()
    }

    /// Set the operand at position `idx` to `val`. The previous operand
    /// (if any) has its use-list updated.
    pub fn set_operand(&mut self, idx: usize, val: ValueRef) {
        let mut v = self.value.borrow_mut();

        // Ensure we have enough space
        while v.operands.len() <= idx {
            v.operands.push(valref(Value::new(Type::void()))); // placeholder
        }

        // Remove old use from the previous operand
        if idx < v.operands.len() {
            let old_val = &v.operands[idx];
            old_val.borrow_mut().remove_use(&self.value);
        }

        // Set new operand
        v.operands[idx] = val.clone();
        v.num_operands = v.operands.len();

        // Register this user as a use of the new operand
        val.borrow_mut().add_use(Rc::downgrade(&self.value), idx);
    }

    /// Add an operand at the end.
    pub fn add_operand(&mut self, val: ValueRef) {
        let mut v = self.value.borrow_mut();
        let idx = v.operands.len();
        v.operands.push(val.clone());
        v.num_operands = v.operands.len();
        drop(v);
        // Register this user as a use of the new operand
        val.borrow_mut().add_use(Rc::downgrade(&self.value), idx);
    }

    /// Remove the operand at position `idx`. All subsequent operands are
    /// shifted left, and their use-list entries are updated.
    pub fn remove_operand(&mut self, idx: usize) {
        let mut v = self.value.borrow_mut();
        if idx >= v.operands.len() {
            return;
        }

        // Remove the use from the removed operand
        v.operands[idx].borrow_mut().remove_use(&self.value);

        // Remove the operand
        v.operands.remove(idx);

        // Update operand indices for remaining operands
        for (i, op) in v.operands.iter().enumerate().skip(idx) {
            // Update the use entry's operand_no
            let uses = &mut op.borrow_mut().uses;
            for u in uses.iter_mut() {
                if let Some(user_rc) = u.user.upgrade() {
                    if Rc::ptr_eq(&user_rc, &self.value) && u.operand_no > idx {
                        u.operand_no = i;
                    }
                }
            }
        }
        v.num_operands = v.operands.len();
    }

    /// Replace an operand: all occurrences of `old` are replaced with
    /// `new`.
    pub fn replace_operand(&mut self, old: ValueRef, new: ValueRef) -> usize {
        let mut count = 0;
        let mut v = self.value.borrow_mut();
        for i in 0..v.operands.len() {
            if Rc::ptr_eq(&v.operands[i], &old) {
                // Remove use from old
                old.borrow_mut().remove_use(&self.value);
                // Set new operand
                v.operands[i] = Rc::clone(&new);
                // Register use of new
                new.borrow_mut().add_use(Rc::downgrade(&self.value), i);
                count += 1;
            }
        }
        count
    }

    /// Check whether `val` is one of this user's operands.
    pub fn has_operand(&self, val: &ValueRef) -> bool {
        let v = self.value.borrow();
        v.operands.iter().any(|op| Rc::ptr_eq(op, val))
    }

    /// Get all operands as a Vec.
    pub fn get_all_operands(&self) -> Vec<ValueRef> {
        self.value.borrow().get_all_operands()
    }

    /// Drop all references (clear operands). This removes this user from
    /// the use-lists of all its operands.
    pub fn drop_all_references(&mut self) {
        let mut v = self.value.borrow_mut();
        for op in &v.operands {
            op.borrow_mut().remove_use(&self.value);
        }
        v.operands.clear();
        v.num_operands = 0;
    }

    /// Check whether this user uses the given value as an operand.
    pub fn is_user_of(&self, val: &ValueRef) -> bool {
        self.has_operand(val)
    }

    /// Get the value reference for this user.
    pub fn as_value_ref(&self) -> ValueRef {
        Rc::clone(&self.value)
    }

    /// Get the name of this user.
    pub fn get_name(&self) -> String {
        self.value.borrow().name.clone()
    }

    /// Set the name of this user.
    pub fn set_name(&mut self, name: &str) {
        self.value.borrow_mut().name = name.to_string();
    }

    /// Get the type of this user.
    pub fn get_type(&self) -> Type {
        self.value.borrow().ty.clone()
    }

    // -------------------------------------------------------------------
    // Use-list introspection
    // -------------------------------------------------------------------

    /// Get the values that use this user.
    pub fn get_users(&self) -> Vec<ValueRef> {
        self.value.borrow().get_uses()
    }

    /// Get the number of values that use this user.
    pub fn get_num_users(&self) -> usize {
        self.value.borrow().num_uses()
    }

    /// Check if this user has any users.
    pub fn has_users(&self) -> bool {
        !self.value.borrow().use_empty()
    }

    /// Replace all uses of this user with `new_value`.
    pub fn replace_all_uses_with(&mut self, new_value: &ValueRef) {
        self.value.borrow_mut().replace_all_uses_with(new_value);
    }
}

// ===========================================================================
// Use Tracking
// ===========================================================================

impl User {
    /// Returns an iterator over the uses of this value (values that use this user).
    pub fn use_begin(&self) -> UseIterator {
        UseIterator {
            uses: self.value.borrow().uses.clone(),
            index: 0,
        }
    }

    /// Returns an end sentinel for the use iterator.
    pub fn use_end(&self) -> UseIterator {
        UseIterator {
            uses: self.value.borrow().uses.clone(),
            index: self.value.borrow().uses.len(),
        }
    }

    /// Get the total number of uses of this value (LLVM-style name).
    pub fn get_num_uses(&self) -> usize {
        self.value.borrow().num_uses()
    }

    /// Check whether this value has exactly `n` uses.
    pub fn has_n_uses(&self, n: usize) -> bool {
        self.value.borrow().has_n_uses(n)
    }

    /// Check whether this value has `n` or more uses.
    pub fn has_n_uses_or_more(&self, n: usize) -> bool {
        self.value.borrow().num_uses() >= n
    }

    /// Check whether this value has exactly one use.
    pub fn has_one_use(&self) -> bool {
        self.value.borrow().has_one_use()
    }

    /// If this value has exactly one use, return that user.
    pub fn get_unique_use(&self) -> Option<ValueRef> {
        self.value.borrow().get_unique_use()
    }

    /// Check whether this value has zero uses.
    pub fn use_empty(&self) -> bool {
        self.value.borrow().use_empty()
    }

    /// Check whether the use-list is empty (LLVM alias).
    pub fn has_no_uses(&self) -> bool {
        self.use_empty()
    }

    /// Replace uses of `from` with `to` within this user's operands.
    /// Returns the number of replacements made.
    pub fn replace_uses_of_with(&mut self, from: &ValueRef, to: &ValueRef) -> usize {
        let mut count = 0;
        let mut v = self.value.borrow_mut();
        for i in 0..v.operands.len() {
            if Rc::ptr_eq(&v.operands[i], from) {
                // Remove use from old
                from.borrow_mut().remove_use(&self.value);
                // Set new operand
                v.operands[i] = Rc::clone(to);
                // Register use of new
                to.borrow_mut().add_use(Rc::downgrade(&self.value), i);
                count += 1;
            }
        }
        count
    }

    /// Replace all uses of this value with `new_value`, optionally using a
    /// value map for batched RAUW operations. The map tracks old→new
    /// mappings so that multiple RAUWs can be resolved consistently.
    pub fn replace_all_uses_with_map(&mut self, new_value: &ValueRef, value_map: &mut ValueMap) {
        // Record the mapping for later resolution
        let old_vid = self.value.borrow().vid;
        let new_vid = new_value.borrow().vid;
        value_map.insert(old_vid, new_vid);

        // Perform the replacement
        self.value.borrow_mut().replace_all_uses_with(new_value);
    }

    /// Check whether this value has any registered value handles.
    pub fn has_value_handle(&self) -> bool {
        self.value.borrow().has_value_handle()
    }

    /// Add a callback to be invoked when this value is RAUW'd or deleted.
    pub fn add_value_handle(&mut self, handle: ValueHandle) {
        self.value.borrow_mut().add_value_handle(handle);
    }

    /// Remove a value handle by its ID.
    pub fn remove_value_handle(&mut self, handle_id: u64) -> bool {
        self.value.borrow_mut().remove_value_handle(handle_id)
    }

    /// Get the number of registered value handles.
    pub fn get_num_value_handles(&self) -> usize {
        self.value.borrow().get_num_value_handles()
    }
}

// ===========================================================================
// Use Iterator
// ===========================================================================

/// Iterator over the uses of a Value.
#[derive(Debug, Clone)]
pub struct UseIterator {
    uses: Vec<Use>,
    index: usize,
}

impl UseIterator {
    /// Create a new use iterator from a value's use list.
    pub fn new(uses: Vec<Use>) -> Self {
        Self { uses, index: 0 }
    }

    /// Get the current use, if any.
    pub fn get(&self) -> Option<&Use> {
        self.uses.get(self.index)
    }

    /// Get the user of the current use, if any.
    pub fn get_user(&self) -> Option<ValueRef> {
        self.uses.get(self.index).and_then(|u| u.user.upgrade())
    }

    /// Get the operand number of the current use.
    pub fn get_operand_no(&self) -> Option<usize> {
        self.uses.get(self.index).map(|u| u.operand_no)
    }

    /// Advance to the next use.
    pub fn advance(&mut self) {
        self.index += 1;
    }

    /// Check if the iterator is at the end.
    pub fn is_end(&self) -> bool {
        self.index >= self.uses.len()
    }

    /// Check if the iterator is at the beginning.
    pub fn is_begin(&self) -> bool {
        self.index == 0
    }

    /// Get the raw Use reference at the current position.
    pub fn get_use(&self) -> Option<&Use> {
        self.uses.get(self.index)
    }

    /// Set the operand number for the current use.
    pub fn set_operand_no(&mut self, op_no: usize) {
        if let Some(u) = self.uses.get_mut(self.index) {
            u.operand_no = op_no;
        }
    }
}

impl Iterator for UseIterator {
    type Item = ValueRef;

    fn next(&mut self) -> Option<Self::Item> {
        while self.index < self.uses.len() {
            let u = &self.uses[self.index];
            self.index += 1;
            if let Some(user) = u.user.upgrade() {
                return Some(user);
            }
            // Skip expired weak references
        }
        None
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let remaining = self.uses.len().saturating_sub(self.index);
        (0, Some(remaining))
    }
}

// ===========================================================================
// Operand Iterator
// ===========================================================================

/// Iterator over the operands of a User.
#[derive(Debug, Clone)]
pub struct OperandIterator {
    operands: Vec<ValueRef>,
    index: usize,
}

impl OperandIterator {
    /// Create a new operand iterator from a user's operands.
    pub fn new(operands: Vec<ValueRef>) -> Self {
        Self { operands, index: 0 }
    }

    /// Get the current operand, if any.
    pub fn get(&self) -> Option<&ValueRef> {
        self.operands.get(self.index)
    }

    /// Get the operand use entry for the current operand, if the user
    /// can be identified. Returns (user, operand_no).
    pub fn get_operand_use(&self, user: &ValueRef) -> Option<Use> {
        self.operands.get(self.index).map(|_| Use {
            user: Rc::downgrade(user),
            operand_no: self.index,
        })
    }

    /// Advance to the next operand.
    pub fn advance(&mut self) {
        self.index += 1;
    }

    /// Check if the iterator is at the end.
    pub fn is_end(&self) -> bool {
        self.index >= self.operands.len()
    }

    /// Check if the iterator is at the beginning.
    pub fn is_begin(&self) -> bool {
        self.index == 0
    }

    /// Reset to the beginning.
    pub fn reset(&mut self) {
        self.index = 0;
    }
}

impl Iterator for OperandIterator {
    type Item = ValueRef;

    fn next(&mut self) -> Option<Self::Item> {
        if self.index < self.operands.len() {
            let val = Rc::clone(&self.operands[self.index]);
            self.index += 1;
            Some(val)
        } else {
            None
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let remaining = self.operands.len().saturating_sub(self.index);
        (remaining, Some(remaining))
    }

    fn count(self) -> usize {
        self.operands.len().saturating_sub(self.index)
    }
}

impl ExactSizeIterator for OperandIterator {}

// ===========================================================================
// Operand Utilities (LLVM-style aliases)
// ===========================================================================

impl User {
    /// Begin operand iterator (LLVM-style name).
    pub fn operand_begin(&self) -> OperandIterator {
        OperandIterator::new(self.value.borrow().operands.clone())
    }

    /// End operand iterator (LLVM-style name).
    pub fn operand_end(&self) -> OperandIterator {
        let ops = self.value.borrow().operands.clone();
        OperandIterator {
            index: ops.len(),
            operands: ops,
        }
    }

    /// Get the Use entry for the operand at `idx`.
    pub fn get_operand_use(&self, idx: usize) -> Option<Use> {
        let v = self.value.borrow();
        if idx < v.operands.len() {
            Some(Use {
                user: Rc::downgrade(&self.value),
                operand_no: idx,
            })
        } else {
            None
        }
    }

    /// Check whether `val` is one of this user's operands (LLVM-style name).
    pub fn has_operand_value(&self, val: &ValueRef) -> bool {
        self.has_operand(val)
    }

    /// Get the use at position `idx` in this value's use-list.
    pub fn get_use(&self, idx: usize) -> Option<Use> {
        self.value.borrow().uses.get(idx).cloned()
    }

    /// Get the user at position `idx` in this value's use-list.
    pub fn get_user(&self, idx: usize) -> Option<ValueRef> {
        self.value
            .borrow()
            .uses
            .get(idx)
            .and_then(|u| u.user.upgrade())
    }

    /// Get the operand number at position `idx` in this value's use-list.
    pub fn get_use_operand_no(&self, idx: usize) -> Option<usize> {
        self.value.borrow().uses.get(idx).map(|u| u.operand_no)
    }

    /// Mutate the type of this value and all of its operands to the new type.
    /// This is a dangerous operation used during IR transformations (e.g.,
    /// opaque pointer migration, type legalization). All operand values
    /// have their types mutated as well.
    pub fn mutate_types(&mut self, new_type: Type) {
        let mut v = self.value.borrow_mut();
        v.mutate_type(new_type.clone());

        // Mutate all operands
        for op in &v.operands {
            op.borrow_mut().mutate_type(new_type.clone());
        }
    }

    /// Mutate the types of all operands to `new_type` without changing
    /// this user's own type.
    pub fn mutate_operand_types(&mut self, new_type: Type) {
        let v = self.value.borrow();
        for op in &v.operands {
            op.borrow_mut().mutate_type(new_type.clone());
        }
    }
}

// ===========================================================================
// ValueMap — batched RAUW resolution
// ===========================================================================

/// A map from old value IDs to new value IDs, used for batched RAUW
/// (replaceAllUsesWith) operations. When multiple values are being replaced
/// simultaneously, the map ensures consistent resolution order.
#[derive(Debug, Clone, Default)]
pub struct ValueMap {
    map: HashMap<u64, u64>,
}

impl ValueMap {
    /// Create a new empty value map.
    pub fn new() -> Self {
        Self {
            map: HashMap::new(),
        }
    }

    /// Insert a mapping from old value ID to new value ID.
    pub fn insert(&mut self, old_vid: u64, new_vid: u64) {
        self.map.insert(old_vid, new_vid);
    }

    /// Look up the replacement for a value ID, following chains.
    pub fn lookup(&self, vid: u64) -> u64 {
        let mut current = vid;
        // Follow the chain up to a reasonable depth to avoid cycles
        for _ in 0..64 {
            match self.map.get(&current) {
                Some(&next) => current = next,
                None => break,
            }
        }
        current
    }

    /// Check whether a value ID has a mapping.
    pub fn contains(&self, vid: u64) -> bool {
        self.map.contains_key(&vid)
    }

    /// Get the number of mappings.
    pub fn len(&self) -> usize {
        self.map.len()
    }

    /// Check if the map is empty.
    pub fn is_empty(&self) -> bool {
        self.map.is_empty()
    }

    /// Clear all mappings.
    pub fn clear(&mut self) {
        self.map.clear();
    }

    /// Resolve all mappings transitively. After this call, every key
    /// maps directly to its final target (no chains).
    pub fn resolve_all(&mut self) {
        let keys: Vec<u64> = self.map.keys().cloned().collect();
        for key in keys {
            let resolved = self.lookup(key);
            self.map.insert(key, resolved);
        }
    }
}

// ===========================================================================
// Use Extensions
// ===========================================================================

impl Use {
    /// Get the user of this use, if still alive.
    pub fn get_user(&self) -> Option<ValueRef> {
        self.user.upgrade()
    }

    /// Get the operand number for this use.
    pub fn get_operand_no(&self) -> usize {
        self.operand_no
    }

    /// Set the operand number for this use.
    pub fn set_operand_no(&mut self, op_no: usize) {
        self.operand_no = op_no;
    }

    /// Get the operand value from the user, if the user is still alive.
    pub fn get(&self) -> Option<ValueRef> {
        self.user
            .upgrade()
            .and_then(|user| user.borrow().operand(self.operand_no))
    }

    /// Set the operand value in the user, if the user is still alive.
    pub fn set(&self, val: ValueRef) -> bool {
        if let Some(user_rc) = self.user.upgrade() {
            let mut user = user_rc.borrow_mut();
            if self.operand_no < user.operands.len() {
                // Remove old use
                user.operands[self.operand_no]
                    .borrow_mut()
                    .remove_use(&user_rc);
                // Set new operand
                user.operands[self.operand_no] = Rc::clone(&val);
                val.borrow_mut()
                    .add_use(Rc::downgrade(&user_rc), self.operand_no);
                return true;
            }
        }
        false
    }

    /// Get the type of the used value.
    pub fn get_value_type(&self) -> Option<Type> {
        self.get().map(|v| v.borrow().ty.clone())
    }

    /// Check if this use still points to a live value.
    pub fn is_valid(&self) -> bool {
        self.user.upgrade().is_some()
    }

    /// Create a Use from a user and operand number.
    pub fn new(user: &ValueRef, operand_no: usize) -> Self {
        Self {
            user: Rc::downgrade(user),
            operand_no,
        }
    }

    /// Get the user's value ID.
    pub fn get_user_vid(&self) -> Option<u64> {
        self.user.upgrade().map(|u| u.borrow().vid)
    }

    /// Get the user's name.
    pub fn get_user_name(&self) -> Option<String> {
        self.user.upgrade().map(|u| u.borrow().name.clone())
    }
}

// ===========================================================================
// ValueHandle — Callbacks on RAUW and Deletion
// ===========================================================================

/// The kind of callback a ValueHandle should invoke.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ValueHandleKind {
    /// Weak handle: simply tracks the value; no callback on RAUW.
    Weak,
    /// Callback handle: invokes a user-provided closure on RAUW.
    Callback,
    /// Asserting handle: panics if the value is deleted without being RAUW'd.
    Asserting,
    /// Tracking handle: automatically updates to point to the new value on RAUW.
    Tracking,
    /// Poisoning handle: invalidates itself on RAUW or deletion.
    Poisoning,
}

/// Callback invoked when a tracked value is replaced or deleted.
#[derive(Clone)]
pub enum ValueHandleCallback {
    /// No callback (for Weak handles).
    None,
    /// A closure that receives the old value and the new value (None if deleted).
    #[allow(clippy::type_complexity)]
    Func(Rc<dyn Fn(&ValueRef, Option<&ValueRef>)>),
    /// Asserting: panics with the given message if the value is deleted.
    Assert(String),
    /// Tracking: a shared cell holding the current value reference.
    Tracking(Rc<RefCell<Option<ValueRef>>>),
}

impl std::fmt::Debug for ValueHandleCallback {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::None => write!(f, "None"),
            Self::Func(_) => write!(f, "Func(...)"),
            Self::Assert(msg) => write!(f, "Assert({})", msg),
            Self::Tracking(_) => write!(f, "Tracking(...)"),
        }
    }
}

/// A handle that tracks a Value and optionally invokes callbacks when the
/// value is replaced (RAUW) or deleted.
#[derive(Debug, Clone)]
pub struct ValueHandle {
    pub id: u64,
    pub kind: ValueHandleKind,
    pub callback: ValueHandleCallback,
}

impl ValueHandle {
    /// Create a new weak value handle.
    pub fn new_weak(id: u64) -> Self {
        Self {
            id,
            kind: ValueHandleKind::Weak,
            callback: ValueHandleCallback::None,
        }
    }

    /// Create a new callback value handle that invokes `f` on RAUW.
    pub fn new_callback<F>(id: u64, f: F) -> Self
    where
        F: Fn(&ValueRef, Option<&ValueRef>) + 'static,
    {
        Self {
            id,
            kind: ValueHandleKind::Callback,
            callback: ValueHandleCallback::Func(Rc::new(f)),
        }
    }

    /// Create an asserting value handle that panics if the value is deleted
    /// without being RAUW'd first.
    pub fn new_asserting(id: u64, msg: impl Into<String>) -> Self {
        Self {
            id,
            kind: ValueHandleKind::Asserting,
            callback: ValueHandleCallback::Assert(msg.into()),
        }
    }

    /// Create a tracking value handle that automatically follows RAUW.
    pub fn new_tracking(id: u64, cell: Rc<RefCell<Option<ValueRef>>>) -> Self {
        Self {
            id,
            kind: ValueHandleKind::Tracking,
            callback: ValueHandleCallback::Tracking(cell),
        }
    }

    /// Create a poisoning value handle that invalidates on RAUW.
    pub fn new_poisoning(id: u64) -> Self {
        Self {
            id,
            kind: ValueHandleKind::Poisoning,
            callback: ValueHandleCallback::None,
        }
    }

    /// Invoke the handle's callback. Called when the tracked value is RAUW'd.
    pub fn on_rauw(&self, old_val: &ValueRef, new_val: &ValueRef) {
        match &self.callback {
            ValueHandleCallback::Func(f) => f(old_val, Some(new_val)),
            ValueHandleCallback::Tracking(cell) => {
                *cell.borrow_mut() = Some(Rc::clone(new_val));
            }
            ValueHandleCallback::Assert(_) => {
                // Asserting handles don't fire on RAUW; they only fire on deletion
            }
            ValueHandleCallback::None => {}
        }
    }

    /// Invoke the handle's callback when the tracked value is deleted.
    pub fn on_delete(&self, old_val: &ValueRef) {
        match &self.callback {
            ValueHandleCallback::Func(f) => f(old_val, None),
            ValueHandleCallback::Assert(msg) => {
                panic!(
                    "AssertingVH: value '{}' (vid={}) was deleted without being RAUW'd: {}",
                    old_val.borrow().name,
                    old_val.borrow().vid,
                    msg
                );
            }
            ValueHandleCallback::Tracking(cell) => {
                *cell.borrow_mut() = None;
            }
            ValueHandleCallback::None => {}
        }
    }
}

// ===========================================================================
// WeakVH — Simple weak reference that tracks a Value
// ===========================================================================

/// A weak value handle that does not prevent the value from being destroyed.
/// Useful for caching and non-owning references that should not keep values alive.
#[derive(Debug, Clone)]
pub struct WeakVH {
    weak_ref: WeakValueRef,
}

impl WeakVH {
    /// Create a WeakVH tracking the given value.
    pub fn new(val: &ValueRef) -> Self {
        Self {
            weak_ref: Rc::downgrade(val),
        }
    }

    /// Try to get the tracked value. Returns None if the value has been destroyed.
    pub fn get(&self) -> Option<ValueRef> {
        self.weak_ref.upgrade()
    }

    /// Check if the tracked value is still alive.
    pub fn is_alive(&self) -> bool {
        self.weak_ref.upgrade().is_some()
    }

    /// Update the tracked value.
    pub fn reset(&mut self, val: &ValueRef) {
        self.weak_ref = Rc::downgrade(val);
    }

    /// Called when the tracked value is RAUW'd. WeakVH does nothing.
    pub fn all_uses_replaced_with(&mut self, _new_val: &ValueRef) {
        // Weak handles don't follow RAUW; they just keep pointing
        // to the old value (which may become dead).
    }
}

// ===========================================================================
// CallbackVH — ValueHandle that invokes a callback on RAUW/deletion
// ===========================================================================

/// A value handle that invokes a user-provided callback when the tracked
/// value is RAUW'd or deleted.
#[derive(Clone)]
pub struct CallbackVH {
    handle: ValueHandle,
    tracked: WeakValueRef,
}

impl CallbackVH {
    /// Create a CallbackVH that invokes `f` on RAUW/deletion.
    pub fn new<F>(id: u64, val: &ValueRef, f: F) -> Self
    where
        F: Fn(&ValueRef, Option<&ValueRef>) + 'static,
    {
        Self {
            handle: ValueHandle::new_callback(id, f),
            tracked: Rc::downgrade(val),
        }
    }

    /// Get the tracked value, if still alive.
    pub fn get(&self) -> Option<ValueRef> {
        self.tracked.upgrade()
    }

    /// Check if the tracked value is still alive.
    pub fn is_alive(&self) -> bool {
        self.tracked.upgrade().is_some()
    }

    /// Update tracking to a new value (does not fire callback).
    pub fn reset(&mut self, val: &ValueRef) {
        self.tracked = Rc::downgrade(val);
    }

    /// Called when the tracked value is RAUW'd.
    pub fn all_uses_replaced_with(&self, new_val: &ValueRef) {
        if let Some(old) = self.tracked.upgrade() {
            self.handle.on_rauw(&old, new_val);
        }
    }

    /// Called when the tracked value is deleted.
    pub fn deleted(&self) {
        if let Some(old) = self.tracked.upgrade() {
            self.handle.on_delete(&old);
        }
    }
}

impl std::fmt::Debug for CallbackVH {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("CallbackVH")
            .field("handle_id", &self.handle.id)
            .field("alive", &self.is_alive())
            .finish()
    }
}

// ===========================================================================
// AssertingVH — Panics on deletion without RAUW
// ===========================================================================

/// A value handle that asserts (panics) if the tracked value is deleted
/// without first being RAUW'd. This is useful for catching use-after-free
/// bugs in IR transformations.
#[derive(Debug, Clone)]
pub struct AssertingVH {
    handle: ValueHandle,
    tracked: WeakValueRef,
    was_rauwed: Rc<RefCell<bool>>,
}

impl AssertingVH {
    /// Create an AssertingVH with a custom panic message.
    pub fn new(id: u64, val: &ValueRef, msg: impl Into<String>) -> Self {
        Self {
            handle: ValueHandle::new_asserting(id, msg),
            tracked: Rc::downgrade(val),
            was_rauwed: Rc::new(RefCell::new(false)),
        }
    }

    /// Create an AssertingVH with a default panic message.
    pub fn new_default(id: u64, val: &ValueRef) -> Self {
        let name = val.borrow().name.clone();
        Self::new(id, val, format!("AssertingVH: value '{}' deleted", name))
    }

    /// Get the tracked value, if still alive.
    pub fn get(&self) -> Option<ValueRef> {
        self.tracked.upgrade()
    }

    /// Check if the tracked value is still alive.
    pub fn is_alive(&self) -> bool {
        self.tracked.upgrade().is_some()
    }

    /// Called when the tracked value is RAUW'd.
    pub fn all_uses_replaced_with(&mut self, _new_val: &ValueRef) {
        *self.was_rauwed.borrow_mut() = true;
    }

    /// Called when the tracked value is deleted.
    pub fn deleted(&self) {
        if !*self.was_rauwed.borrow() {
            if let Some(old) = self.tracked.upgrade() {
                self.handle.on_delete(&old);
            }
        }
    }
}

// ===========================================================================
// TrackingVH — Automatically follows RAUW
// ===========================================================================

/// A value handle that automatically updates to point to the replacement
/// value when the tracked value is RAUW'd. This is the most commonly used
/// value handle in LLVM for maintaining up-to-date references during
/// transformations.
#[derive(Debug, Clone)]
pub struct TrackingVH {
    cell: Rc<RefCell<Option<ValueRef>>>,
}

impl TrackingVH {
    /// Create a TrackingVH tracking the given value.
    pub fn new(val: &ValueRef) -> Self {
        let cell = Rc::new(RefCell::new(Some(Rc::clone(val))));
        // Register as a value handle so the value knows to update us on RAUW
        let mut v = val.borrow_mut();
        let handle = ValueHandle::new_tracking(v.vid, Rc::clone(&cell));
        v.add_value_handle(handle);
        Self { cell }
    }

    /// Get the currently tracked value. Returns None if the value was deleted.
    pub fn get(&self) -> Option<ValueRef> {
        self.cell.borrow().clone()
    }

    /// Check if the tracked value is still alive.
    pub fn is_alive(&self) -> bool {
        self.cell.borrow().is_some()
    }

    /// Update to track a different value.
    pub fn reset(&mut self, val: &ValueRef) {
        let mut v = val.borrow_mut();
        let handle = ValueHandle::new_tracking(v.vid, Rc::clone(&self.cell));
        v.add_value_handle(handle);
        *self.cell.borrow_mut() = Some(Rc::clone(val));
    }

    /// Called when the tracked value is RAUW'd (handled automatically).
    pub fn all_uses_replaced_with(&self, new_val: &ValueRef) {
        *self.cell.borrow_mut() = Some(Rc::clone(new_val));
    }

    /// Called when the tracked value is deleted.
    pub fn deleted(&self) {
        *self.cell.borrow_mut() = None;
    }

    /// Dereference to the underlying ValueRef, panicking if deleted.
    pub fn unwrap(&self) -> ValueRef {
        self.get().expect("TrackingVH: value has been deleted")
    }
}

// ===========================================================================
// PoisoningVH — Invalidates on RAUW/deletion
// ===========================================================================

/// A value handle that becomes "poisoned" (invalidated) when the tracked
/// value is RAUW'd or deleted. Any subsequent attempt to dereference the
/// handle will return None. This is used to detect when a cached reference
/// becomes stale.
#[derive(Debug, Clone)]
pub struct PoisoningVH {
    value: WeakValueRef,
    poisoned: Rc<RefCell<bool>>,
}

impl PoisoningVH {
    /// Create a PoisoningVH tracking the given value.
    pub fn new(val: &ValueRef) -> Self {
        Self {
            value: Rc::downgrade(val),
            poisoned: Rc::new(RefCell::new(false)),
        }
    }

    /// Get the tracked value. Returns None if poisoned or deleted.
    pub fn get(&self) -> Option<ValueRef> {
        if *self.poisoned.borrow() {
            return None;
        }
        self.value.upgrade()
    }

    /// Check if the handle is poisoned.
    pub fn is_poisoned(&self) -> bool {
        *self.poisoned.borrow()
    }

    /// Called when the tracked value is RAUW'd.
    pub fn all_uses_replaced_with(&self, _new_val: &ValueRef) {
        *self.poisoned.borrow_mut() = true;
    }

    /// Called when the tracked value is deleted.
    pub fn deleted(&self) {
        *self.poisoned.borrow_mut() = true;
    }

    /// Update to track a new value (unpoisons).
    pub fn reset(&mut self, val: &ValueRef) {
        self.value = Rc::downgrade(val);
        *self.poisoned.borrow_mut() = false;
    }
}

// ===========================================================================
// ValueHandle registry methods for Value
// ===========================================================================

impl crate::value::Value {
    /// Check whether this value has any registered value handles.
    pub fn has_value_handle(&self) -> bool {
        // Stored in subclass_data extension; we use bit 0 as a flag
        (self.subclass_data & 0x8000_0000) != 0
    }

    /// Get the number of registered value handles.
    pub fn get_num_value_handles(&self) -> usize {
        if self.has_value_handle() {
            // The count is stored in the metadata map under a special key
            self.metadata.get(&0xFFFF_FFFE).copied().unwrap_or(0) as usize
        } else {
            0
        }
    }

    /// Add a value handle to this value's tracking list.
    pub fn add_value_handle(&mut self, _handle: ValueHandle) {
        // Set the has-handle flag
        self.subclass_data |= 0x8000_0000;
        let count = self.get_num_value_handles() + 1;
        self.metadata.insert(0xFFFF_FFFE, count as u32);
        // In a full implementation, handles would be stored in a side-table.
        // For now, we track the count so that RAUW and deletion can check
        // whether handles need to be notified.
    }

    /// Remove a value handle by ID. Returns true if a handle was removed.
    pub fn remove_value_handle(&mut self, _handle_id: u64) -> bool {
        if !self.has_value_handle() {
            return false;
        }
        let count = self.get_num_value_handles();
        if count > 0 {
            let new_count = count - 1;
            if new_count == 0 {
                self.subclass_data &= !0x8000_0000;
                self.metadata.remove(&0xFFFF_FFFE);
            } else {
                self.metadata.insert(0xFFFF_FFFE, new_count as u32);
            }
            true
        } else {
            false
        }
    }

    /// Notify all registered value handles that this value is being RAUW'd.
    pub fn notify_handles_rauw(&self, _new_val: &ValueRef) {
        if !self.has_value_handle() {
            return;
        }
        // In a full implementation, iterate the handle list and call on_rauw.
        // The handles are stored externally and keyed by (vid, handle_id).
    }

    /// Notify all registered value handles that this value is being deleted.
    pub fn notify_handles_deleted(&self) {
        if !self.has_value_handle() {
            return;
        }
        // In a full implementation, iterate the handle list and call on_delete.
    }
}

// ===========================================================================
// RAUW with ValueMap integration
// ===========================================================================

/// Perform a batched replaceAllUsesWith across multiple values.
/// The `replacements` map specifies old→new mappings. All replacements
/// are resolved against each other so that chains are handled correctly.
pub fn batch_replace_all_uses_with(
    replacements: &HashMap<u64, ValueRef>,
    value_map: &mut ValueMap,
) {
    // First, resolve all chains in the value map
    // Then apply each replacement
    let mut ordered: Vec<(u64, ValueRef)> = replacements
        .iter()
        .map(|(k, v)| (*k, Rc::clone(v)))
        .collect();
    for (old_vid, new_val) in &ordered {
        value_map.insert(*old_vid, new_val.borrow().vid);
    }
    value_map.resolve_all();
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

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

    fn make_val(name: &str, ty: Type) -> ValueRef {
        valref(Value::new(ty).named(name))
    }

    #[test]
    fn test_user_new() {
        let u = User::new(Type::i32(), 1, "myuser".to_string());
        assert_eq!(u.get_name(), "myuser");
        assert_eq!(u.get_num_operands(), 0);
    }

    #[test]
    fn test_user_named() {
        let u = User::named("hello", Type::void());
        assert_eq!(u.get_name(), "hello");
    }

    #[test]
    fn test_from_value() {
        let val = valref(
            Value::new(Type::i32())
                .named("val")
                .with_subclass(SubclassKind::User),
        );
        let u = User::from_value(val.clone());
        assert!(Rc::ptr_eq(&u.value, &val));
    }

    #[test]
    fn test_add_and_get_operand() {
        let mut u = User::named("user", Type::void());
        let op1 = make_val("op1", Type::i32());
        let op2 = make_val("op2", Type::i64());

        u.add_operand(op1.clone());
        u.add_operand(op2.clone());

        assert_eq!(u.get_num_operands(), 2);
        let got0 = u.get_operand(0).unwrap();
        assert!(Rc::ptr_eq(&got0, &op1));
        let got1 = u.get_operand(1).unwrap();
        assert!(Rc::ptr_eq(&got1, &op2));
        assert!(u.get_operand(2).is_none());
    }

    #[test]
    fn test_set_operand() {
        let mut u = User::named("user", Type::void());
        let op1 = make_val("op1", Type::i32());
        let op2 = make_val("op2", Type::i32());

        u.add_operand(op1.clone());
        assert_eq!(u.get_num_operands(), 1);

        u.set_operand(0, op2.clone());
        assert!(Rc::ptr_eq(&u.get_operand(0).unwrap(), &op2));
    }

    #[test]
    fn test_set_operand_grows() {
        let mut u = User::named("user", Type::void());
        let op = make_val("op", Type::i32());
        // Set operand at index 2 (auto-grows with placeholders)
        u.set_operand(2, op.clone());
        assert!(u.get_num_operands() >= 3);
        assert!(Rc::ptr_eq(&u.get_operand(2).unwrap(), &op));
    }

    #[test]
    fn test_remove_operand() {
        let mut u = User::named("user", Type::void());
        let op1 = make_val("op1", Type::i32());
        let op2 = make_val("op2", Type::i32());
        let op3 = make_val("op3", Type::i32());

        u.add_operand(op1.clone());
        u.add_operand(op2.clone());
        u.add_operand(op3.clone());
        assert_eq!(u.get_num_operands(), 3);

        u.remove_operand(1);
        assert_eq!(u.get_num_operands(), 2);
        assert!(Rc::ptr_eq(&u.get_operand(0).unwrap(), &op1));
        assert!(Rc::ptr_eq(&u.get_operand(1).unwrap(), &op3));
    }

    #[test]
    fn test_remove_operand_out_of_bounds_no_panic() {
        let mut u = User::named("user", Type::void());
        let op = make_val("op", Type::i32());
        u.add_operand(op);
        u.remove_operand(99); // should not panic
        assert_eq!(u.get_num_operands(), 1);
    }

    #[test]
    fn test_has_operand() {
        let mut u = User::named("user", Type::void());
        let op1 = make_val("op1", Type::i32());
        let op2 = make_val("op2", Type::i32());

        u.add_operand(op1.clone());
        assert!(u.has_operand(&op1));
        assert!(!u.has_operand(&op2));
    }

    #[test]
    fn test_replace_operand() {
        let mut u = User::named("user", Type::void());
        let old1 = make_val("old1", Type::i32());
        let old2 = make_val("old2", Type::i32());
        let new = make_val("new", Type::i32());

        u.add_operand(old1.clone());
        u.add_operand(old2.clone());
        u.add_operand(old1.clone()); // duplicate

        let count = u.replace_operand(old1.clone(), new.clone());
        assert_eq!(count, 2);
        assert!(!u.has_operand(&old1));
        assert!(u.has_operand(&old2));
        assert!(u.has_operand(&new));
    }

    #[test]
    fn test_drop_all_references() {
        let mut u = User::named("user", Type::void());
        let op1 = make_val("op1", Type::i32());
        let op2 = make_val("op2", Type::i32());

        u.add_operand(op1.clone());
        u.add_operand(op2.clone());

        // Both operands should have this user in their use-list
        assert!(op1.borrow().num_uses() > 0);
        assert!(op2.borrow().num_uses() > 0);

        u.drop_all_references();
        assert_eq!(u.get_num_operands(), 0);
    }

    #[test]
    fn test_is_user_of() {
        let mut u = User::named("user", Type::void());
        let op = make_val("op", Type::i32());
        u.add_operand(op.clone());
        assert!(u.is_user_of(&op));

        let other = make_val("other", Type::i32());
        assert!(!u.is_user_of(&other));
    }

    #[test]
    fn test_get_users() {
        let u = User::named("inner", Type::void());
        let outer = User::named("outer", Type::void());

        // Make outer use inner
        let mut outer_mut = outer;
        outer_mut.add_operand(u.as_value_ref());

        let users = u.get_users();
        assert_eq!(users.len(), 1);
    }

    #[test]
    fn test_replace_all_uses_with() {
        let mut old_user = User::named("old", Type::i32());
        let new_val = make_val("new_val", Type::i32());

        // Create another user that uses old_user
        let mut consumer = User::named("consumer", Type::void());
        consumer.add_operand(old_user.as_value_ref());

        // Replace all uses of old_user with new_val
        old_user.replace_all_uses_with(&new_val);

        // consumer should now reference new_val
        assert!(consumer.has_operand(&new_val));
    }

    #[test]
    fn test_get_name_and_set_name() {
        let mut u = User::named("original", Type::void());
        assert_eq!(u.get_name(), "original");
        u.set_name("renamed");
        assert_eq!(u.get_name(), "renamed");
    }

    #[test]
    fn test_get_type() {
        let u = User::named("user", Type::i64());
        let ty = u.get_type();
        assert!(ty.is_integer());
        assert_eq!(ty.integer_bit_width(), 64);
    }

    #[test]
    fn test_get_all_operands() {
        let mut u = User::named("user", Type::void());
        let op1 = make_val("op1", Type::i32());
        let op2 = make_val("op2", Type::i32());
        u.add_operand(op1.clone());
        u.add_operand(op2.clone());

        let all = u.get_all_operands();
        assert_eq!(all.len(), 2);
        assert!(Rc::ptr_eq(&all[0], &op1));
        assert!(Rc::ptr_eq(&all[1], &op2));
    }

    #[test]
    fn test_use_list_consistency() {
        let mut u = User::named("user", Type::void());
        let op = make_val("op", Type::i32());

        // Before adding, op should have no uses
        assert_eq!(op.borrow().num_uses(), 0);

        u.add_operand(op.clone());
        // After adding, op should have one use (this user)
        assert_eq!(op.borrow().num_uses(), 1);

        u.remove_operand(0);
        // After removing, op should have no uses again
        assert_eq!(op.borrow().num_uses(), 0);
    }
}