redix 1.4.1

#![cfg_attr(test, feature(test))]

///  Representation of a radix tree as implemented in this file, that contains
///  the strings "foo", "foobar" and "footer" after the insertion of each
///  word. When the node represents a key inside the radix tree, we write it
///  between [], otherwise it is written between ().
///
///  This is the vanilla representation:
///
/// ```text
///               (f) ""
///                 \
///                 (o) "f"
///                   \
///                   (o) "fo"
///                     \
///                   [t   b] "foo"
///                   /     \
///          "foot" (e)     (a) "foob"
///                 /         \
///       "foote" (r)         (r) "fooba"
///               /             \
///     "footer" []             [] "foobar"
/// ```
///
///  However, this implementation implements a very common optimization where
///  successive nodes having a single child are "compressed" into the node
///  itself as a string of characters, each representing a next-level child,
///  and only the link to the node representing the last character node is
///  provided inside the representation. So the above representation is turned
///  into:
///
/// ```text
///                   ["foo"] ""
///                      |
///                   [t   b] "foo"
///                   /     \
///         "foot" ("er")    ("ar") "foob"
///                  /          \
///        "footer" []          [] "foobar"
/// ```
///
///  However this optimization makes the implementation a bit more complex.
///  For instance if a key "first" is added in the above radix tree, a
///  "node splitting" operation is needed, since the "foo" prefix is no longer
///  composed of nodes having a single child one after the other. This is the
///  above tree and the resulting node splitting after this event happens:
///
///
/// ```text
///                     (f) ""
///                     /
///                  (i o) "f"
///                  /   \
///     "firs"  ("rst")  (o) "fo"
///               /        \
///     "first" []       [t   b] "foo"
///                      /     \
///            "foot" ("er")    ("ar") "foob"
///                     /          \
///           "footer" []          [] "foobar"
/// ```
///
///  Similarly after deletion, if a new chain of nodes having a single child
///  is created (the chain must also not include nodes that represent keys),
///  it must be compressed back into a single node.
extern crate libc;
extern crate nix;

use std::{
    alloc::{alloc, dealloc, Layout},
    error, fmt,
    mem::{size_of, MaybeUninit},
    ptr,
};

use nix::errno::Errno;

pub const GREATER: &str = ">";
pub const GREATER_EQUAL: &str = ">=";
pub const LESSER: &str = "<";
pub const LESSER_EQUAL: &str = "<=";
pub const EQUAL: &str = "=";
pub const BEGIN: &str = "^";
pub const END: &str = "$";

pub const RAX_NODE_MAX_SIZE: libc::c_int = (1 << 29) - 1;
pub const RAX_STACK_STATIC_ITEMS: libc::c_int = 32;
pub const RAX_ITER_STATIC_LEN: libc::c_int = 128;
pub const RAX_ITER_JUST_SEEKED: libc::c_int = 1 << 0;
pub const RAX_ITER_EOF: libc::c_int = 1 << 1;
pub const RAX_ITER_SAFE: libc::c_int = 1 << 2;

/// Return the existing Rax allocator.
///
/// # Safety
///
/// Must only be called when no other thread is modifying the allocator.
pub unsafe fn allocator() -> (
    extern "C" fn(size: libc::size_t) -> *mut u8,
    extern "C" fn(ptr: *mut libc::c_void, size: libc::size_t) -> *mut u8,
    extern "C" fn(ptr: *mut libc::c_void),
) {
    (rax_malloc, rax_realloc, rax_free)
}

/// Rax internally makes calls to "malloc", "realloc" and "free" for all
/// of it's heap memory needs. These calls can be patched with the
/// supplied hooks. Do not call this method after Rax has been used at
/// all. This must be called before using or calling any other Rax API
/// function.
///
/// # Safety
///
/// Must be called before any Rax allocation occurs. Not thread-safe.
pub unsafe fn set_allocator(
    malloc: extern "C" fn(size: libc::size_t) -> *mut u8,
    realloc: extern "C" fn(ptr: *mut libc::c_void, size: libc::size_t) -> *mut u8,
    free: extern "C" fn(ptr: *mut libc::c_void),
) {
    rax_malloc = malloc;
    rax_realloc = realloc;
    rax_free = free;
}

#[derive(Debug)]
pub enum RaxError {
    Generic(GenericError),
    OutOfMemory(),
}

impl RaxError {
    pub fn generic(message: &str) -> RaxError {
        RaxError::Generic(GenericError::new(message))
    }
}

/// Redis has a beautiful Radix Tree implementation in ANSI C. This
/// brings it to Rust and creates a safe Map like wrapper for it. This
/// is very similar in utility to a BTreeMap, but RAX is likely much
/// faster and more efficient. Naive testing showed a 2x-4x improvement
/// for all common operations. The only disadvantage to BTreeMap is that
/// BTree's allow much more flexibility in regards to comparing keys.
/// Radix trees are lexicographically only. Composite keys where the
/// non-last member is variable length could be something BTrees could
/// handle much easier.
///
/// Internal RAX Node Layout
///
/// uint32_t iskey:1;     /* Does this node contain a key? */
/// uint32_t isnull:1;    /* Associated value is NULL (don't store it). */
/// uint32_t iscompr:1;   /* Node is compressed. */
/// uint32_t size:29;     /* Number of children, or compressed string len. */
///
/// +----+---+--------+--------+--------+--------+
/// |HDR |xyz| x-ptr  | y-ptr  | z-ptr  |dataptr |
/// +----+---+--------+--------+--------+--------+
///
/// As is evident above, there is no storage penalty for NULL values.
///
/// Keys are represented in compressed form therefore, there is no need
/// to pump in Boxed keys or any sort of heap allocated chunk of memory.
/// Stack or heap keys may be used from rust. Values can either be a
/// sizeof<usize> size integer or it's a data pointer to a heap
/// allocated / Boxed value.
///
/// Iterators were designed to be fast and attempt to only use stack
/// allocated memory. RaxMap provides a model to take full advantage of
/// stack allocated iterators through wrapping in a closure.
///
/// #Examples
///
/// ```
/// use redix::RaxMap;
/// let mut r = RaxMap::new();
/// r.insert(1, "my heap allocation".to_string());
/// r.insert(2, "my other heap allocation".to_string());
///
/// r.iter(|r, iter| {
///     // Place iterator at the first entry.
///     if !iter.seek_min() {
///         // EOF
///         return;
///     }
///
///     // Can test EOF at any time.
///     if iter.eof() {
///         // EOF
///         return;
///     }
///
///     while iter.forward() {
///         iter.key();
///         iter.value();
///     }
///     // In reverse
///     // Place iterator at the end.
///     if !iter.seek_max() {
///         // EOF
///         return;
///     }
///     while iter.back() {
///         iter.key();
///         iter.value();
///     }
///
///     // Seek
///     if !iter.seek(">=", 2) {
///         // EOF
///     }
///     while iter.forward() {
///         iter.key();
///         iter.value();
///     }
/// });
/// ```
pub struct RaxMap<K: RaxKey, V> {
    pub rax: *mut rax,
    phantom: std::marker::PhantomData<(K, V)>,
}

impl<K: RaxKey, V> Drop for RaxMap<K, V> {
    fn drop(&mut self) {
        // SAFETY: self.rax is non-null (guaranteed by try_new/new).
        // raxFreeWithCallback frees all nodes and invokes the callback
        // on each stored value pointer so we can drop the Box<V>.
        unsafe {
            raxFreeWithCallback(self.rax, RaxFreeWithCallbackWrapper::<V>);
        }
    }
}

// SAFETY: RaxMap owns a unique heap allocation. No shared mutable
// state, therefore safe to transfer between threads.
unsafe impl<K: RaxKey + Send, V: Send> Send for RaxMap<K, V> {}

// SAFETY: &RaxMap only allows read-only access (find/get) which don't
// mutate the underlying C tree, therefore safe to share across threads.
unsafe impl<K: RaxKey + Sync, V: Sync> Sync for RaxMap<K, V> {}

impl<K: RaxKey, V> Default for RaxMap<K, V> {
    fn default() -> Self {
        Self::new()
    }
}

/// Implementation of RaxMap
impl<K: RaxKey, V> RaxMap<K, V> {
    /// Create a new RaxMap.
    ///
    /// # Panics
    ///
    /// Panics if `raxNew()` returns NULL (out of memory).
    pub fn new() -> RaxMap<K, V> {
        #[expect(clippy::disallowed_methods)]
        Self::try_new().expect("raxNew: out of memory")
    }

    /// Fallible constructor.
    ///
    /// Returns `Err(OutOfMemory)` when `raxNew()` returns NULL.
    pub fn try_new() -> Result<RaxMap<K, V>, RaxError> {
        // SAFETY: raxNew() allocates a new rax tree.
        // We check for NULL before storing the pointer.
        let ptr = unsafe { raxNew() };

        if ptr.is_null() {
            return Err(RaxError::OutOfMemory());
        }

        Ok(RaxMap {
            rax: ptr,
            phantom: std::marker::PhantomData,
        })
    }

    /// The number of entries in the RAX
    pub fn len(&self) -> u64 {
        unsafe { raxSize(self.rax) }
    }

    /// The number of entries in the RAX
    pub fn size(&self) -> u64 {
        unsafe { raxSize(self.rax) }
    }

    /// Returns true if the RAX is empty.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Prints the Rax as ASCII art to stdout.
    pub fn show(&self) {
        unsafe { raxShow(self.rax) }
    }

    /// Insert or replace existing key with a NULL value.
    pub fn insert_null(&mut self, key: K) -> Result<Option<V>, RaxError> {
        unsafe {
            // Allocate a pointer to catch the old value.
            let old: &mut *mut u8 = &mut ptr::null_mut();

            // Integer values require Big Endian to allow the Rax to fully optimize
            // storing them since it will be able to compress the prefixes especially
            // for 64/128bit numbers.
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let r = raxInsert(
                self.rax,
                // Grab a raw pointer to the key. Keys are most likely
                // allocated on the stack. The rax will keep it's own
                // copy of the key so we don't want to keep in in the
                // heap twice and it exists in the rax in it's
                // compressed form.
                ptr,
                len,
                std::ptr::null_mut(),
                old,
            );

            if r == 0 && Errno::last() == Errno::ENOMEM {
                Err(RaxError::OutOfMemory())
            } else if old.is_null() {
                Ok(None)
            } else {
                // Read previous value out and free it.
                let old_ptr = *old as *mut V;
                let value = ptr::read(old_ptr);
                let layout = Layout::new::<V>();
                if layout.size() != 0 {
                    dealloc(old_ptr as *mut u8, layout);
                }
                Ok(Some(value))
            }
        }
    }

    /// Try to insert a new entry into the RAX if an existing one does not exist.
    pub fn try_insert(&mut self, key: K, data: V) -> Result<Option<V>, RaxError> {
        let value_ptr = try_alloc_value(data).map_err(|_| RaxError::OutOfMemory())?;
        unsafe {
            // Allocate a pointer to catch the old value.
            let old: &mut *mut u8 = &mut ptr::null_mut();

            // Integer values require Big Endian to allow the Rax to
            // fully optimize storing them since it will be able to
            // compress the prefixes especially for 64/128bit numbers.
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let r = raxTryInsert(
                self.rax,
                // Grab a raw pointer to the key. Keys are most likely
                // allocated on the stack. The rax will keep it's own
                // copy of the key so we don't want to keep in in the
                // heap twice and it exists in the rax in it's
                // compressed form.
                ptr,
                len,
                value_ptr as *mut u8,
                old,
            );

            if r == 0 {
                // Reclaim allocation not stored by rax.
                let value = ptr::read(value_ptr);
                let layout = Layout::new::<V>();
                if layout.size() != 0 {
                    dealloc(value_ptr as *mut u8, layout);
                }
                if Errno::last() == Errno::ENOMEM {
                    Err(RaxError::OutOfMemory())
                } else {
                    Ok(Some(value))
                }
            } else if old.is_null() {
                Ok(None)
            } else {
                let old_ptr = *old as *mut V;
                let value = ptr::read(old_ptr);
                let layout = Layout::new::<V>();
                if layout.size() != 0 {
                    dealloc(old_ptr as *mut u8, layout);
                }
                Ok(Some(value))
            }
        }
    }

    /// Try to insert a raw pointer value into the RAX.
    ///
    /// # Safety
    ///
    /// `value` must be a valid pointer or null.
    pub unsafe fn try_insert_ptr(
        &mut self,
        key: K,
        value: *mut u8,
    ) -> Result<Option<*mut u8>, RaxError> {
        // Allocate a pointer to catch the old value.
        let old: &mut *mut u8 = &mut ptr::null_mut();

        // Integer values require Big Endian to allow the Rax to fully optimize
        // storing them since it will be able to compress the prefixes especially
        // for 64/128bit numbers.
        let k = key.encode();
        let (ptr, len) = k.to_buf();

        let r = raxTryInsert(
            self.rax,
            // Grab a raw pointer to the key. Keys are most likely allocated
            // on the stack. The rax will keep it's own copy of the key so we
            // don't want to keep in in the heap twice and it exists in the
            // rax in it's compressed form.
            ptr, len, value, old,
        );

        if r == 0 {
            if Errno::last() == Errno::ENOMEM {
                Err(RaxError::OutOfMemory())
            } else {
                Ok(Some(value))
            }
        } else if old.is_null() {
            Ok(None)
        } else {
            // This shouldn't happen, but if it does let's be safe and
            // not leak memory.
            Ok(Some(*old))
        }
    }

    /// Insert a new entry into the RAX replacing and returning the
    /// existing entry for the supplied key.
    pub fn insert(&mut self, key: K, data: V) -> Result<Option<V>, RaxError> {
        let value_ptr = try_alloc_value(data).map_err(|_| RaxError::OutOfMemory())?;
        unsafe {
            // Allocate a pointer to catch the old value.
            let old: &mut *mut u8 = &mut ptr::null_mut();

            // Integer values require Big Endian to allow the Rax to
            // fully optimize storing them since it will be able to
            // compress the prefixes especially for 64/128bit numbers.
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let r = raxInsert(
                self.rax,
                // Grab a raw pointer to the key. Keys are most likely
                // allocated on the stack. The rax will keep it's own
                // copy of the key so we don't want to keep in in the
                // heap twice and it exists in the rax in it's
                // compressed form.
                ptr,
                len,
                value_ptr as *mut u8,
                old,
            );

            if r == 0 && Errno::last() == Errno::ENOMEM {
                // Reclaim allocation after failed insert.
                dealloc_value(value_ptr);
                Err(RaxError::OutOfMemory())
            } else if old.is_null() {
                Ok(None)
            } else {
                // Read previous value out and free it.
                let old_ptr = *old as *mut V;
                let value = ptr::read(old_ptr);
                let layout = Layout::new::<V>();
                if layout.size() != 0 {
                    dealloc(old_ptr as *mut u8, layout);
                }
                Ok(Some(value))
            }
        }
    }

    /// Insert a raw pointer value into the RAX.
    ///
    /// # Safety
    ///
    /// `value` must be a valid pointer or null.
    pub unsafe fn insert_ptr(
        &mut self,
        key: K,
        value: *mut u8,
    ) -> Result<Option<*mut u8>, RaxError> {
        // Allocate a pointer to catch the old value.
        let old: &mut *mut u8 = &mut ptr::null_mut();

        // Integer values require Big Endian to allow the Rax to fully optimize
        // storing them since it will be able to compress the prefixes especially
        // for 64/128bit numbers.
        let k = key.encode();
        let (ptr, len) = k.to_buf();

        let r = raxInsert(
            self.rax,
            // Grab a raw pointer to the key. Keys are most likely allocated
            // on the stack. The rax will keep it's own copy of the key so we
            // don't want to keep in in the heap twice and it exists in the
            // rax in it's compressed form.
            ptr, len, value, old,
        );

        if r == 0 && Errno::last() == Errno::ENOMEM {
            Err(RaxError::OutOfMemory())
        } else if old.is_null() {
            Ok(None)
        } else {
            // Box the previous value since Rax is done with it and it's
            // our responsibility now to drop it. Once this Box goes out
            // of scope the value is dropped and memory reclaimed.
            Ok(Some(*old))
        }
    }

    /// Remove an entry from the RAX and return the associated value.
    pub fn remove(&mut self, key: K) -> (bool, Option<V>) {
        unsafe {
            let old: &mut *mut u8 = &mut ptr::null_mut();
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let r = raxRemove(self.rax, ptr, len, old);

            if old.is_null() {
                (r == 1, None)
            } else {
                // Read value out and free it.
                let old_ptr = *old as *mut V;
                let value = ptr::read(old_ptr);
                let layout = Layout::new::<V>();
                if layout.size() != 0 {
                    dealloc(old_ptr as *mut u8, layout);
                }
                (r == 1, Some(value))
            }
        }
    }

    /// Find a key and return whether it exists along with its value.
    pub fn find_exists(&self, key: K) -> (bool, Option<&V>) {
        unsafe {
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let value = raxFind(self.rax, ptr, len);

            if value.is_null() {
                (true, None)
            } else if value == raxNotFound {
                (false, None)
            } else {
                // transmute to the value so we don't drop the actual value accidentally.
                // While the key associated to the value is in the RAX then we cannot
                // drop it.
                (true, Some(&*(value as *const V)))
            }
        }
    }

    /// Same as get but added for semantics parity.
    pub fn find(&self, key: K) -> Option<&V> {
        unsafe {
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let value = raxFind(self.rax, ptr, len);

            if value.is_null() || value == raxNotFound {
                None
            } else {
                // transmute to the value so we don't drop the actual value accidentally.
                // While the key associated to the value is in the RAX then we cannot
                // drop it.
                Some(&*(value as *const V))
            }
        }
    }

    /// Get the value associated with the key.
    pub fn get(&self, key: K) -> Option<&V> {
        unsafe {
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let value = raxFind(self.rax, ptr, len);

            if value.is_null() || value == raxNotFound {
                None
            } else {
                // transmute to the value so we don't drop the actual value accidentally.
                // While the key associated to the value is in the RAX then we cannot
                // drop it.
                Some(&*(value as *const V))
            }
        }
    }

    /// Determines if the supplied key exists in the Rax.
    pub fn exists(&self, key: K) -> bool {
        unsafe {
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let value = raxFind(self.rax, ptr, len);

            !(value.is_null() || value == raxNotFound)
        }
    }

    /// Seek to the minimum key and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn seek_min<F>(&mut self, f: F)
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_min();
            f(self, &mut iter)
        }
    }

    /// Seek to the minimum key and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn seek_min_result<R, F>(&mut self, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_min();
            f(self, &mut iter)
        }
    }

    /// Seek to the maximum key and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn seek_max<F>(&mut self, f: F)
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_max();
            f(self, &mut iter)
        }
    }

    /// Seek to the maximum key and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn seek_max_result<R, F>(&mut self, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_max();
            f(self, &mut iter)
        }
    }

    /// Seek to the given key using the specified operator and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn seek<F>(&mut self, op: &str, key: K, f: F)
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek(op, key);
            f(self, &mut iter)
        }
    }

    /// Seek to the given key using the specified operator and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn seek_result<R, F>(&mut self, op: &str, key: K, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek(op, key);
            f(self, &mut iter)
        }
    }

    /// Create an iterator and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn iter<F>(&mut self, f: F)
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            f(self, &mut iter)
        }
    }

    /// Create an iterator and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the map inside the closure is undefined behaviour.
    pub fn iter_result<F, R>(&mut self, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxMap<K, V>, &mut RaxIterator<K, V>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            f(self, &mut iter)
        }
    }
}

/// RaxMap but without the values. The "isnull" bit will be set for
/// all entries.
/// #Examples
///
/// ```
/// use redix::RaxSet;
/// let mut r = RaxSet::new();
/// r.insert(1);
/// r.insert(2);
///
/// r.iter(|r, iter| {
///     // Place iterator at the first entry.
///     if !iter.seek_min() {
///         // EOF
///         return;
///     }
///
///     // Can test EOF at any time.
///     if iter.eof() {
///         // EOF
///         return;
///     }
///
///     while iter.forward() {
///         iter.key();
///     }
///     // In reverse
///     // Place iterator at the end.
///     if !iter.seek_max() {
///         // EOF
///         return;
///     }
///     while iter.back() {
///         iter.key();
///     }
///
///     // Seek
///     if !iter.seek(">=", 2) {
///         // EOF
///     }
///     while iter.forward() {
///         iter.key();
///     }
/// });
/// ```
pub struct RaxSet<K: RaxKey> {
    rax: *mut rax,
    _marker: std::marker::PhantomData<K>,
}

impl<K: RaxKey> Drop for RaxSet<K> {
    fn drop(&mut self) {
        // SAFETY: self.rax is non-null.
        unsafe { raxFree(self.rax) }
    }
}

// SAFETY: RaxSet owns a unique heap allocation. No shared mutable
// state, therefore safe to transfer between threads.
unsafe impl<K: RaxKey + Send> Send for RaxSet<K> {}

// SAFETY: &RaxSet only allows read-only access (find/get) which don't
// mutate the underlying C tree, therefore safe to share across threads.
unsafe impl<K: RaxKey + Sync> Sync for RaxSet<K> {}

impl<K: RaxKey> Default for RaxSet<K> {
    fn default() -> Self {
        Self::new()
    }
}

/// Implementation of RaxSet.
impl<K: RaxKey> RaxSet<K> {
    /// Create a new RaxSet.
    ///
    /// # Panics
    ///
    /// Panics if `raxNew()` returns NULL (out of memory).
    pub fn new() -> RaxSet<K> {
        #[expect(clippy::disallowed_methods)]
        Self::try_new().expect("raxNew: out of memory")
    }

    /// Fallible constructor.
    ///
    /// Returns `Err(OutOfMemory)` when `raxNew()` returns NULL.
    pub fn try_new() -> Result<RaxSet<K>, RaxError> {
        // SAFETY: raxNew() allocates a new rax tree. We check for NULL
        // before storing the pointer.
        let ptr = unsafe { raxNew() };

        if ptr.is_null() {
            return Err(RaxError::OutOfMemory());
        }

        Ok(RaxSet {
            rax: ptr,
            _marker: std::marker::PhantomData,
        })
    }

    /// The number of entries in the RAX
    pub fn len(&self) -> u64 {
        unsafe { raxSize(self.rax) }
    }

    /// The number of entries in the RAX
    pub fn size(&self) -> u64 {
        unsafe { raxSize(self.rax) }
    }

    /// Prints the Rax as ASCII art to stdout.
    pub fn show(&self) {
        unsafe { raxShow(self.rax) }
    }

    /// Returns true if the RAX is empty.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Insert a new entry into the RAX replacing and returning the existing
    /// entry for the supplied key.
    pub fn insert(&mut self, key: K) -> Result<bool, RaxError> {
        unsafe {
            // Integer values require Big Endian to allow the Rax to fully optimize
            // storing them since it will be able to compress the prefixes especially
            // for 64/128bit numbers.
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let r = raxTryInsert(
                self.rax,
                // Grab a raw pointer to the key. Keys are most likely allocated
                // on the stack. The rax will keep it's own copy of the key so we
                // don't want to keep in in the heap twice and it exists in the
                // rax in it's compressed form.
                ptr,
                len,
                std::ptr::null_mut(),
                std::ptr::null_mut(),
            );

            if r == 0 {
                if Errno::last() == Errno::ENOMEM {
                    Err(RaxError::OutOfMemory())
                } else {
                    Ok(false)
                }
            } else {
                Ok(true)
            }
        }
    }

    pub fn remove(&mut self, key: K) -> bool {
        unsafe {
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let r = raxRemove(self.rax, ptr, len, &mut std::ptr::null_mut());

            r == 1
        }
    }

    /// Determines if the supplied key exists in the Rax.
    pub fn exists(&self, key: K) -> bool {
        unsafe {
            let k = key.encode();
            let (ptr, len) = k.to_buf();

            let value = raxFind(self.rax, ptr, len);

            value != raxNotFound
        }
    }

    /// Seek to the minimum key and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn seek_min<F>(&mut self, f: F)
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_min();
            f(self, &mut iter)
        }
    }

    /// Seek to the minimum key and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn seek_min_result<R, F>(&mut self, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_min();
            f(self, &mut iter)
        }
    }

    /// Seek to the maximum key and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn seek_max<F>(&mut self, f: F)
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_max();
            f(self, &mut iter)
        }
    }

    /// Seek to the maximum key and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn seek_max_result<R, F>(&mut self, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek_max();
            f(self, &mut iter)
        }
    }

    /// Seek to the given key using the specified operator and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn seek<F>(&mut self, op: &str, key: K, f: F)
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek(op, key);
            f(self, &mut iter)
        }
    }

    /// Seek to the given key using the specified operator and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn seek_result<R, F>(&mut self, op: &str, key: K, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter.seek(op, key);
            f(self, &mut iter)
        }
    }

    /// Create an iterator and execute the closure.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn iter<F>(&mut self, f: F)
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>),
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            f(self, &mut iter)
        }
    }

    /// Create an iterator and execute the closure, returning a result.
    ///
    /// # Safety
    ///
    /// Mutating the set inside the closure is undefined behaviour.
    pub fn iter_result<F, R>(&mut self, f: F) -> Result<R, RaxError>
    where
        F: Fn(&mut RaxSet<K>, &mut RaxIterator<K, usize>) -> Result<R, RaxError>,
    {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, usize>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, self.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            f(self, &mut iter)
        }
    }
}

// Same as RaxMap except values are not pointers to heap allocations.
// Instead the "data pointer" in the RAX is the value. This means we
// have sizeof<usize> worth of bytes to play with. Perhaps, in the future
// we could create data values of any size, but for now we have the size
// of pointers to work with or null which has no added size to a rax node.
//pub struct RaxIntMap<K: RaxKey> {
//    rax: *mut rax,
//    _marker: std::marker::PhantomData<K>,
//}
//
//impl<K: RaxKey> RaxIntMap<K> {
//    pub fn new() -> RaxIntMap<K> {
//        RaxIntMap {
//            rax: unsafe { raxNew() },
//            _marker: std::marker::PhantomData,
//        }
//    }
//
//    /// Insert a new entry into the RAX replacing and returning the existing
//    /// entry for the supplied key.
//    pub fn insert(&mut self, key: K, value: usize) -> Result<Option<usize>, RaxError> {
//        unsafe {
//            // Allocate a pointer to catch the old value.
//            let old: &mut *mut u8 = &mut ptr::null_mut();
//
//            // Integer values require Big Endian to allow the Rax to fully optimize
//            // storing them since it will be able to compress the prefixes especially
//            // for 64/128bit numbers.
//            let k = key.encode();
//            let (ptr, len) = k.to_buf();
//
//            let r = raxInsert(
//                self.rax,
//                // Grab a raw pointer to the key. Keys are most likely allocated
//                // on the stack. The rax will keep it's own copy of the key so we
//                // don't want to keep in in the heap twice and it exists in the
//                // rax in it's compressed form.
//                ptr,
//                len,
//                &value as *const _ as *mut u8,
//                old,
//            );
//
//            if r == 0 && Errno::last() == Errno::ENOMEM {
//                Err(RaxError::OutOfMemory())
//            } else if old.is_null() {
//                Ok(None)
//            } else {
//                Ok(Some(std::mem::transmute(*old)))
//            }
//        }
//    }
//
//    /// Insert a new entry into the RAX if an existing one does not exist.
//    pub fn try_insert(&mut self, key: K, data: usize) -> Result<Option<usize>, RaxError> {
//        unsafe {
//            // Allocate a pointer to catch the old value.
//            let old: &mut *mut u8 = &mut ptr::null_mut();
//
//            // Integer values require Big Endian to allow the Rax to fully optimize
//            // storing them since it will be able to compress the prefixes especially
//            // for 64/128bit numbers.
//            let k = key.encode();
//            let (ptr, len) = k.to_buf();
//
//            let r = raxTryInsert(
//                self.rax,
//                // Grab a raw pointer to the key. Keys are most likely allocated
//                // on the stack. The rax will keep it's own copy of the key so we
//                // don't want to keep in in the heap twice and it exists in the
//                // rax in it's compressed form.
//                ptr,
//                len,
//                &data as *const _ as *mut u8,
//                old,
//            );
//
//            if r == 0 {
//                if Errno::last() == Errno::ENOMEM {
//                    Err(RaxError::OutOfMemory())
//                } else if old.is_null() {
//                    Ok(None)
//                } else {
//                    Ok(Some(transmute(*old)))
//                }
//            } else if old.is_null() {
//                Ok(None)
//            } else {
//                Ok(Some(std::mem::transmute(*old)))
//            }
//        }
//    }
//}

pub trait RaxKey<RHS = Self>: Clone + Default + std::fmt::Debug {
    type Output: RaxKey;

    fn encode(self) -> Self::Output;

    fn to_buf(&self) -> (*const u8, usize);

    /// # Safety
    ///
    /// `ptr` must be valid for reads of `len` bytes.
    unsafe fn from_buf(ptr: *const u8, len: usize) -> RHS;
}

impl RaxKey for f32 {
    type Output = u32;

    fn encode(self) -> Self::Output {
        // Encode as u32 Big Endian
        self.to_bits().to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        // This should never get called since we represent as a u32
        (
            self as *const _ as *const u8,
            std::mem::size_of::<Self::Output>(),
        )
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> f32 {
        assert_eq!(len, std::mem::size_of::<f32>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe {
            // We used a BigEndian u32 to encode so let's reverse it
            f32::from_bits(u32::from_be(
                *(ptr as *mut [u8; std::mem::size_of::<Self::Output>()] as *mut u32),
            ))
        }
    }
}

impl RaxKey for f64 {
    type Output = u64;

    fn encode(self) -> Self::Output {
        // Encode as u64 Big Endian
        self.to_bits().to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        // This should never get called since we represent as a u64
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> f64 {
        assert_eq!(len, std::mem::size_of::<f64>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe {
            // We used a BigEndian u64 to encode so let's reverse it
            f64::from_bits(u64::from_be(
                *(ptr as *mut [u8; size_of::<Self::Output>()] as *mut u64),
            ))
        }
    }
}

impl RaxKey for isize {
    type Output = isize;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> isize {
        assert_eq!(len, std::mem::size_of::<isize>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { isize::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut isize)) }
    }
}

impl RaxKey for usize {
    type Output = usize;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (
            self as *const _ as *const u8,
            std::mem::size_of::<Self::Output>(),
        )
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> usize {
        assert_eq!(len, std::mem::size_of::<usize>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe {
            usize::from_be(*(ptr as *mut [u8; std::mem::size_of::<Self::Output>()] as *mut usize))
        }
    }
}

impl RaxKey for i16 {
    type Output = i16;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> Self {
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { i16::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut i16)) }
    }
}

impl RaxKey for u16 {
    type Output = u16;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> u16 {
        assert_eq!(len, std::mem::size_of::<u16>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { u16::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut u16)) }
    }
}

impl RaxKey for i32 {
    type Output = i32;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> i32 {
        assert_eq!(len, std::mem::size_of::<i32>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { i32::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut i32)) }
    }
}

impl RaxKey for u32 {
    type Output = u32;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> u32 {
        assert_eq!(len, std::mem::size_of::<u32>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { u32::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut u32)) }
    }
}

impl RaxKey for i64 {
    type Output = i64;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> i64 {
        assert_eq!(len, std::mem::size_of::<i64>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { i64::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut i64)) }
    }
}

impl RaxKey for u64 {
    type Output = u64;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> u64 {
        assert_eq!(len, std::mem::size_of::<u64>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { u64::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut u64)) }
    }
}

impl RaxKey for i128 {
    type Output = i128;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> i128 {
        assert_eq!(len, std::mem::size_of::<i128>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { i128::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut i128)) }
    }
}

impl RaxKey for u128 {
    type Output = u128;

    fn encode(self) -> Self::Output {
        self.to_be()
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self as *const _ as *const u8, size_of::<Self::Output>())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> u128 {
        assert_eq!(len, std::mem::size_of::<u128>());
        if len != size_of::<Self::Output>() {
            return Self::default();
        }
        unsafe { u128::from_be(*(ptr as *mut [u8; size_of::<Self::Output>()] as *mut u128)) }
    }
}

impl RaxKey for Vec<u8> {
    type Output = Vec<u8>;

    fn encode(self) -> Vec<u8> {
        self
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self.as_ptr(), self.len())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> Vec<u8> {
        unsafe { std::slice::from_raw_parts(ptr, len).to_vec() }
    }
}

impl<'a> RaxKey for &'a [u8] {
    type Output = &'a [u8];

    fn encode(self) -> &'a [u8] {
        self
    }

    fn to_buf(&self) -> (*const u8, usize) {
        (self.as_ptr(), self.len())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> &'a [u8] {
        unsafe { std::slice::from_raw_parts(ptr, len) }
    }
}

//impl RaxKey for SDS {
//    type Output = SDS;
//
//    fn encode(self) -> Self::Output {
//        self
//    }
//
//    fn to_buf(&self) -> (*const u8, usize) {
//        (self.as_ptr(), self.len())
//    }
//
//    unsafe fn from_buf(ptr: *const u8, len: usize) -> SDS {
//        SDS::from_ptr(ptr, len)
//    }
//}

impl<'a> RaxKey for &'a str {
    type Output = &'a str;

    fn encode(self) -> Self::Output {
        self
    }

    fn to_buf(&self) -> (*const u8, usize) {
        ((*self).as_ptr(), self.len())
    }

    unsafe fn from_buf(ptr: *const u8, len: usize) -> &'a str {
        unsafe { std::str::from_utf8(std::slice::from_raw_parts(ptr, len)).unwrap_or_default() }
    }
}

#[repr(C)]
pub struct RaxIterator<K: RaxKey, V> {
    pub flags: libc::c_int,
    pub rt: *mut rax,
    pub key: *mut u8,
    pub data: *mut libc::c_void,
    pub key_len: libc::size_t,
    pub key_max: libc::size_t,
    pub key_static_string: [u8; 128],
    pub node: *mut raxNode,
    pub stack: raxStack,
    pub node_cb: Option<raxNodeCallback>,
    _marker: std::marker::PhantomData<(K, V)>,
}

/// Free up memory.
impl<K: RaxKey, V> Drop for RaxIterator<K, V> {
    fn drop(&mut self) {
        unsafe {
            // Fix key pointer if it still points at the (moved) inline buffer.
            if self.key_max == RAX_ITER_STATIC_LEN as usize {
                self.key = self.key_static_string.as_mut_ptr();
            }

            // Fix stack pointer if it still points at the (moved) inline array.
            if self.stack.maxitems == RAX_STACK_STATIC_ITEMS as usize {
                self.stack.stack = self.stack.static_items.as_mut_ptr();
            }

            raxStop(&raw mut *self as *mut raxIterator);
        }
    }
}

/// Implement std::Iterator
impl<K: RaxKey, V: 'static> Iterator for RaxIterator<K, V> {
    type Item = (K, Option<&'static V>);

    fn next(&mut self) -> Option<<Self as Iterator>::Item> {
        unsafe {
            if raxNext(&raw mut *self as *mut raxIterator) == 1 {
                let data: *mut libc::c_void = self.data;
                if data.is_null() {
                    None
                } else {
                    let val = data as *const V;
                    if val.is_null() {
                        Some((self.key(), None))
                    } else {
                        Some((self.key(), Some(&*val)))
                    }
                }
            } else {
                None
            }
        }
    }
}

/// Implement std::DoubleEndedIterator
impl<K: RaxKey, V: 'static> DoubleEndedIterator for RaxIterator<K, V> {
    fn next_back(&mut self) -> Option<<Self as Iterator>::Item> {
        unsafe {
            if raxPrev(&raw mut *self as *mut raxIterator) == 1 {
                let data: *mut libc::c_void = self.data;
                if data.is_null() {
                    None
                } else {
                    let val = data as *const V;
                    if val.is_null() {
                        Some((self.key(), None))
                    } else {
                        Some((self.key(), Some(&*val)))
                    }
                }
            } else {
                None
            }
        }
    }
}

/// Core iterator implementation
impl<K: RaxKey, V> RaxIterator<K, V> {
    /// Create a new iterator for the given RaxMap.
    pub fn new(r: RaxMap<K, V>) -> RaxIterator<K, V> {
        // SAFETY: Iterator is initialized with raxStart before use.
        unsafe {
            let mut iter = MaybeUninit::<RaxIterator<K, V>>::uninit();
            raxStart(iter.as_mut_ptr() as *mut raxIterator, r.rax);
            let mut iter = iter.assume_init();
            iter.fixup();
            iter
        }
    }

    pub fn print_ptr(&self) {
        println!("ptr = {:p}", self);
        println!("ptr = {:p}", self as *const _ as *const raxIterator);
    }

    pub fn seek_min(&mut self) -> bool {
        unsafe {
            if raxSeek(
                &raw mut *self as *mut raxIterator,
                BEGIN.as_ptr(),
                std::ptr::null(),
                0,
            ) == 1
            {
                self.forward()
            } else {
                false
            }
        }
    }

    pub fn seek_max(&mut self) -> bool {
        unsafe {
            if raxSeek(
                &raw mut *self as *mut raxIterator,
                END.as_ptr(),
                std::ptr::null(),
                0,
            ) == 1
            {
                self.back()
            } else {
                false
            }
        }
    }

    pub fn back(&mut self) -> bool {
        unsafe { raxPrev(&raw mut *self as *mut raxIterator) == 1 }
    }

    pub fn forward(&mut self) -> bool {
        unsafe { raxNext(&raw mut *self as *mut raxIterator) == 1 }
    }

    /// Key at current position
    pub fn key(&self) -> K {
        unsafe { K::from_buf(self.key, self.key_len) }
    }

    /// Raw key bytes at current position
    pub fn key_bytes(&self) -> &[u8] {
        unsafe { std::slice::from_raw_parts(self.key, self.key_len) }
    }

    /// Data at current position.
    pub fn value(&self) -> Option<&V> {
        unsafe {
            let data: *mut libc::c_void = self.data;
            if data.is_null() {
                None
            } else {
                Some(&*(data as *const V))
            }
        }
    }

    pub fn lesser(&mut self, key: K) -> bool {
        self.seek(LESSER, key)
    }

    pub fn lesser_equal(&mut self, key: K) -> bool {
        self.seek(LESSER_EQUAL, key)
    }

    pub fn greater(&mut self, key: K) -> bool {
        self.seek(GREATER, key)
    }

    pub fn greater_equal(&mut self, key: K) -> bool {
        self.seek(GREATER_EQUAL, key)
    }

    pub fn seek(&mut self, op: &str, key: K) -> bool {
        unsafe {
            let k = key.encode();
            let (p, len) = k.to_buf();
            raxSeek(&raw mut *self as *mut raxIterator, op.as_ptr(), p, len) == 1
                && self.flags & RAX_ITER_EOF != 0
        }
    }

    pub fn seek_raw(&mut self, op: &str, key: K) -> i32 {
        unsafe {
            let k = key.encode();
            let (p, len) = k.to_buf();
            raxSeek(&raw mut *self as *mut raxIterator, op.as_ptr(), p, len)
        }
    }

    pub fn seek_bytes(&mut self, op: &str, ele: &[u8]) -> bool {
        unsafe {
            raxSeek(
                &raw mut *self as *mut raxIterator,
                op.as_ptr(),
                ele.as_ptr(),
                ele.len() as libc::size_t,
            ) == 1
        }
    }

    /// Return if the iterator is in an EOF state. This happens when raxSeek()
    /// failed to seek an appropriate element, so that raxNext() or raxPrev()
    /// will return zero, or when an EOF condition was reached while iterating
    /// with next() and prev().
    pub fn eof(&self) -> bool {
        self.flags & RAX_ITER_EOF != 0
    }

    /// Fix self-referential pointers invalidated by a move.
    pub fn fixup(&mut self) {
        self.key = self.key_static_string.as_mut_ptr();
        self.stack.stack = self.stack.static_items.as_mut_ptr();
    }
}

impl fmt::Display for RaxError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            RaxError::Generic(ref err) => write!(f, "{err}"),
            RaxError::OutOfMemory() => write!(f, "out of memory"),
        }
    }
}

impl error::Error for RaxError {
    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
        match *self {
            // N.B. Both of these implicitly cast `err` from their concrete
            // types (either `&io::Error` or `&num::ParseIntError`)
            // to a trait object `&Error`. This works because both error types
            // implement `Error`.
            RaxError::Generic(ref err) => Some(err),
            RaxError::OutOfMemory() => Some(self),
        }
    }
}

#[derive(Debug)]
pub struct GenericError {
    message: String,
}

impl GenericError {
    pub fn new(message: &str) -> GenericError {
        GenericError {
            message: String::from(message),
        }
    }
}

impl fmt::Display for GenericError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Store error: {}", self.message)
    }
}

impl error::Error for GenericError {}

// Writes `value` into a new heap slot.
//
// Returns the raw pointer on success or the value back on allocation failure.
fn try_alloc_value<T>(value: T) -> Result<*mut T, T> {
    let layout = Layout::new::<T>();
    unsafe {
        let ptr = if layout.size() == 0 {
            ptr::NonNull::<T>::dangling().as_ptr()
        } else {
            let raw = alloc(layout);
            if raw.is_null() {
                return Err(value);
            }
            raw as *mut T
        };
        ptr.write(value);
        Ok(ptr)
    }
}

// Reclaim a heap-allocated value produced by [`try_alloc_value`],
// dropping the value and freeing the memory.
//
// # Safety
//
// `ptr` must have been returned by [`try_alloc_value`] and must not
// have been freed yet.
unsafe fn dealloc_value<T>(ptr: *mut T) {
    ptr::drop_in_place(ptr);
    let layout = Layout::new::<T>();
    if layout.size() != 0 {
        dealloc(ptr as *mut u8, layout);
    }
}

#[repr(C)]
pub struct rax;

#[repr(C)]
pub struct raxNode;

#[repr(C)]
pub struct raxStack {
    stack: *mut *mut libc::c_void,
    items: libc::size_t,
    maxitems: libc::size_t,
    static_items: [*mut libc::c_void; 32],
    oom: libc::c_int,
}

#[repr(C)]
pub struct raxIterator;

#[allow(non_snake_case)]
#[allow(non_camel_case_types)]
extern "C" fn RaxFreeWithCallbackWrapper<V>(v: *mut libc::c_void) {
    // SAFETY: v was allocated by try_alloc_value and is being freed
    // during raxFreeWithCallback.
    unsafe {
        dealloc_value(v as *mut V);
    }
}

#[allow(non_camel_case_types)]
type raxNodeCallback = extern "C" fn(v: *mut libc::c_void);

type RaxFreeCallback = extern "C" fn(v: *mut libc::c_void);

#[allow(improper_ctypes)]
#[allow(non_snake_case)]
#[allow(non_camel_case_types)]
#[link(name = "rax", kind = "static")]
extern "C" {
    pub static raxNotFound: *mut u8;

    pub static mut rax_malloc: extern "C" fn(size: libc::size_t) -> *mut u8;
    pub static mut rax_realloc:
        extern "C" fn(ptr: *mut libc::c_void, size: libc::size_t) -> *mut u8;
    pub static mut rax_free: extern "C" fn(ptr: *mut libc::c_void);

    pub fn raxIteratorSize() -> libc::c_int;

    pub fn raxNew() -> *mut rax;

    pub fn raxFree(rax: *mut rax);

    pub fn raxFreeWithCallback(rax: *mut rax, callback: RaxFreeCallback);

    pub fn raxInsert(
        rax: *mut rax,
        s: *const u8,
        len: libc::size_t,
        data: *const u8,
        old: &mut *mut u8,
    ) -> libc::c_int;

    pub fn raxTryInsert(
        rax: *mut rax,
        s: *const u8,
        len: libc::size_t,
        data: *const u8,
        old: *mut *mut u8,
    ) -> libc::c_int;

    pub fn raxRemove(
        rax: *mut rax,
        s: *const u8,
        len: libc::size_t,
        old: &mut *mut u8,
    ) -> libc::c_int;

    pub fn raxFind(rax: *mut rax, s: *const u8, len: libc::size_t) -> *mut u8;

    pub fn raxIteratorNew(rt: *mut rax) -> *mut raxIterator;

    pub fn raxStart(it: *mut raxIterator, rt: *mut rax);

    pub fn raxSeek(
        it: *mut raxIterator,
        op: *const u8,
        ele: *const u8,
        len: libc::size_t,
    ) -> libc::c_int;

    pub fn raxNext(it: *mut raxIterator) -> libc::c_int;

    pub fn raxPrev(it: *mut raxIterator) -> libc::c_int;

    pub fn raxRandomWalk(it: *mut raxIterator, steps: libc::size_t) -> libc::c_int;

    pub fn raxCompare(
        it: *mut raxIterator,
        op: *const u8,
        key: *mut u8,
        key_len: libc::size_t,
    ) -> libc::c_int;

    pub fn raxStop(it: *mut raxIterator);

    pub fn raxEOF(it: *mut raxIterator) -> libc::c_int;

    pub fn raxShow(rax: *mut rax);

    pub fn raxSize(rax: *mut rax) -> u64;
}

#[cfg(test)]
mod tests {
    extern crate test;
    use std::{
        self,
        default::Default,
        fmt,
        time::{Duration, Instant},
    };

    use super::*;

    extern "C" fn rax_malloc_hook(size: libc::size_t) -> *mut u8 {
        unsafe {
            println!("malloc");
            libc::malloc(size) as *mut u8
        }
    }

    extern "C" fn rax_realloc_hook(ptr: *mut libc::c_void, size: libc::size_t) -> *mut u8 {
        unsafe {
            println!("realloc");
            libc::realloc(ptr, size) as *mut u8
        }
    }

    extern "C" fn rax_free_hook(ptr: *mut libc::c_void) {
        unsafe {
            println!("free");
            libc::free(ptr)
        }
    }

    pub struct MyMsg<'a>(&'a str);

    impl<'a> Drop for MyMsg<'a> {
        fn drop(&mut self) {
            println!("dropped -> {}", self.0);
        }
    }

    #[derive(Clone, Copy)]
    pub struct Stopwatch {
        start_time: Option<Instant>,
        elapsed: Duration,
    }

    impl Default for Stopwatch {
        fn default() -> Stopwatch {
            Stopwatch {
                start_time: None,
                elapsed: Duration::from_secs(0),
            }
        }
    }

    impl fmt::Display for Stopwatch {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            return write!(f, "{}ms", self.elapsed_ms());
        }
    }

    #[expect(unused)]
    impl Stopwatch {
        pub fn new() -> Stopwatch {
            let sw: Stopwatch = Default::default();
            return sw;
        }
        pub fn start_new() -> Stopwatch {
            let mut sw = Stopwatch::new();
            sw.start();
            return sw;
        }

        pub fn start(&mut self) {
            self.start_time = Some(Instant::now());
        }
        pub fn stop(&mut self) {
            self.elapsed = self.elapsed();
            self.start_time = None;
        }
        pub fn reset(&mut self) {
            self.elapsed = Duration::from_secs(0);
            self.start_time = None;
        }
        pub fn restart(&mut self) {
            self.reset();
            self.start();
        }

        pub fn is_running(&self) -> bool {
            return self.start_time.is_some();
        }

        pub fn elapsed(&self) -> Duration {
            match self.start_time {
                Some(t1) => {
                    return t1.elapsed() + self.elapsed;
                }
                None => {
                    return self.elapsed;
                }
            }
        }
        pub fn elapsed_ms(&self) -> i64 {
            let dur = self.elapsed();
            return (dur.as_secs() * 1000 + (dur.subsec_nanos() / 1000000) as u64) as i64;
        }
    }

    #[test]
    fn bench() {
        let ops = 1000000;
        println!("{} operations per function", ops);

        for _ in 0..2 {
            println!();
            println!("Gets...");
            {
                let r = &mut RaxSet::<u64>::new();
                for x in 0..2000 {
                    r.insert(x).expect("whoops!");
                }

                let sw = Stopwatch::start_new();
                for _po in 0..ops {
                    r.exists(1601);
                }

                println!("RaxSet::get       {}ms", sw.elapsed_ms());
            }
            {
                let r = &mut RaxMap::<u64, &str>::new();
                for x in 0..2000 {
                    r.insert_null(x).expect("whoops!");
                }

                match r.find(1601) {
                    Some(v) => println!("{}", v),
                    None => {}
                }

                let sw = Stopwatch::start_new();

                for _po in 0..ops {
                    r.find(1601);
                }

                println!("RaxMap::get       {}ms", sw.elapsed_ms());
            }

            {
                let r = &mut RaxMap::<u64, &str>::new();
                for x in 0..2000 {
                    r.insert_null(x).expect("whoops!");
                }
                let sw = Stopwatch::start_new();

                for _po in 0..ops {
                    r.iter(|_, iter| {
                        iter.seek(EQUAL, 1601);
                    });
                }

                println!("RaxCursor:seek    {}ms", sw.elapsed_ms());
            }
            {
                let r = &mut std::collections::HashSet::<u64>::new();
                for x in 0..2000 {
                    r.insert(x);
                }

                let sw = Stopwatch::start_new();

                let xx = 300;
                for _po in 0..ops {
                    r.get(&xx);
                }

                println!("HashSet::get      {}ms", sw.elapsed_ms());
            }
            {
                let r = &mut std::collections::HashMap::<u64, &str>::new();
                for x in 0..2000 {
                    r.insert(x, "");
                }

                let sw = Stopwatch::start_new();

                let xx = 300;
                for _po in 0..ops {
                    r.get(&xx);
                }

                println!("HashMap::get      {}ms", sw.elapsed_ms());
            }
            {
                let r = &mut std::collections::BTreeSet::<u64>::new();
                for x in 0..2000 {
                    r.insert(x);
                }

                let sw = Stopwatch::start_new();

                let xx = 300;
                for _po in 0..ops {
                    r.get(&xx);
                }

                println!("BTreeSet::get      {}ms", sw.elapsed_ms());
            }
            {
                let r = &mut std::collections::BTreeMap::<u64, &str>::new();
                for x in 0..2000 {
                    r.insert(x, "");
                }

                let sw = Stopwatch::start_new();

                let xx = 300;
                for _po in 0..ops {
                    r.get(&xx);
                }

                println!("BTreeMap::get     {}ms", sw.elapsed_ms());
            }

            println!();
            println!("Inserts...");
            {
                let r = &mut RaxMap::<u64, &str>::new();
                let sw = Stopwatch::start_new();

                for x in 0..ops {
                    r.insert(x, "").expect("whoops!");
                }

                println!("RaxMap::insert        {}ms", sw.elapsed_ms());
            }

            {
                let r = &mut RaxSet::<u64>::new();
                let sw = Stopwatch::start_new();

                for x in 0..ops {
                    r.insert(x).expect("whoops!");
                }

                println!("RaxSet::insert        {}ms", sw.elapsed_ms());
            }

            {
                let r = &mut std::collections::BTreeSet::<u64>::new();
                let sw = Stopwatch::start_new();

                for x in 0..ops {
                    r.insert(x);
                }

                println!("BTreeSet::insert      {}ms", sw.elapsed_ms());
            }
            {
                let r = &mut std::collections::BTreeMap::<u64, &str>::new();
                let sw = Stopwatch::start_new();

                for x in 0..ops {
                    r.insert(x, "");
                }

                println!("BTreeMap::insert      {}ms", sw.elapsed_ms());
            }

            {
                let r = &mut std::collections::HashMap::<u64, &str>::new();
                let sw = Stopwatch::start_new();

                for x in 0..ops {
                    r.insert(x, "");
                }

                println!("HashMap::insert       {}ms", sw.elapsed_ms());
            }
        }
    }

    #[test]
    fn bench_rax_find() {
        for _ in 0..10 {
            let r = &mut RaxMap::<u64, &str>::new();
            for x in 0..2000 {
                r.insert_null(x).expect("whoops!");
            }

            match r.find(1601) {
                Some(v) => println!("{}", v),
                None => {}
            }

            let sw = Stopwatch::start_new();

            for _po in 0..1000000 {
                r.find(1601);
            }

            println!("Thing took {}ms", sw.elapsed_ms());
        }
    }

    #[test]
    fn bench_rax_cur_find() {
        for _ in 0..10 {
            let r = &mut RaxMap::<u64, &str>::new();
            for x in 0..2000 {
                r.insert_null(x).expect("whoops!");
            }

            match r.find(1601) {
                Some(v) => println!("{}", v),
                None => {}
            }

            let sw = Stopwatch::start_new();

            for _po in 0..1000000 {
                r.iter(|_, iter| {
                    iter.seek(EQUAL, 1601);
                });
            }

            println!("RaxMap::cursor_find {}ms", sw.elapsed_ms());
        }
    }

    #[test]
    fn bench_rax_insert() {
        for _ in 0..10 {
            let r = &mut RaxMap::<u64, &str>::new();
            //
            let sw = Stopwatch::start_new();

            for x in 0..1000000 {
                r.insert(x, "").expect("whoops!");
            }

            println!("RaxMap::insert {}ms", sw.elapsed_ms());
            println!("Size {}", r.size());
        }
    }

    #[test]
    fn bench_rax_insert_show() {
        let r = &mut RaxMap::<u64, &str>::new();
        //
        let sw = Stopwatch::start_new();

        for x in 0..100 {
            r.insert(x, "").expect("whoops!");
        }

        r.show();
        println!("RaxMap::insert {}ms", sw.elapsed_ms());
        assert_eq!(r.size(), 100);
    }

    #[test]
    fn bench_rax_replace() {
        let ops = 1000000;
        for _ in 0..2 {
            let r = &mut RaxMap::<u64, &str>::new();
            // Insert values
            for x in 0..ops {
                r.insert(x, "").expect("whoops!");
            }

            let sw = Stopwatch::start_new();

            for x in 0..ops {
                // Replace existing key
                r.insert(x, "").expect("whoops!");
            }

            println!("RaxMap::replace {}ms", sw.elapsed_ms());
            assert_eq!(r.size(), ops);
        }
    }

    #[test]
    fn key_str() {
        unsafe {
            set_allocator(rax_malloc_hook, rax_realloc_hook, rax_free_hook);
        }

        let mut r = RaxMap::<&str, MyMsg>::new();

        let key = "hello-way";

        r.insert(key, MyMsg("world 80")).expect("whoops!");
        r.insert("hello-war", MyMsg("world 80")).expect("whoops!");

        r.insert("hello-wares", MyMsg("world 80")).expect("whoops!");
        r.insert("hello", MyMsg("world 100")).expect("whoops!");

        {
            match r.find("hello") {
                Some(v) => println!("Found {}", v.0),
                None => println!("Not Found"),
            }
        }

        r.show();

        r.iter(|_, iter| {
            if !iter.seek_min() {
                return;
            }
            while iter.forward() {
                println!("{}", iter.key());
            }
            if !iter.seek_max() {
                return;
            }
            while iter.back() {
                println!("{}", iter.key());
            }
        });
    }

    #[test]
    fn key_f64() {
        println!("sizeof(Rax) {}", std::mem::size_of::<RaxMap<f64, MyMsg>>());

        let mut r = RaxMap::<f64, MyMsg>::new();

        r.insert(100.01, MyMsg("world 100")).expect("whoops!");
        r.insert(80.20, MyMsg("world 80")).expect("whoops!");
        r.insert(100.00, MyMsg("world 200")).expect("whoops!");
        r.insert(99.10, MyMsg("world 1")).expect("whoops!");

        r.show();

        r.iter(|_, iter| {
            //            for (k, v) in iter {
            //
            //            }
            iter.seek_min();
            while iter.forward() {
                println!("{}", iter.key());
            }
            iter.seek_max();
            while iter.back() {
                println!("{}", iter.key());
            }
        });
    }

    #[test]
    fn key_u64() {
        println!("sizeof(Rax) {}", std::mem::size_of::<RaxMap<u64, MyMsg>>());

        let mut r = RaxMap::<u64, MyMsg>::new();

        r.insert(100, MyMsg("world 100")).expect("whoops!");
        r.insert(80, MyMsg("world 80")).expect("whoops!");
        r.insert(200, MyMsg("world 200")).expect("whoops!");
        r.insert(1, MyMsg("world 1")).expect("whoops!");

        r.show();

        //        let result = r.iter_result(move |it| {
        //
        //            if !it.seek(GREATER_EQUAL, 800) {
        //                println!("Not Found");
        //                return Ok("");
        //            }
        //
        //            if it.eof() {
        //                println!("Not Found");
        //                return Ok("");
        //            }
        //
        //            while it.forward() {
        //                println!("Key Len = {}", it.key());
        //                println!("Data = {}", it.data().unwrap().0);
        //            }
        //
        //            Ok("")
        //        });

        //        r.seek(GREATER_EQUAL, 80, |_, iter| {
        //            for (key, value) in iter {
        //                println!("Key Len = {}", key);
        //                println!("Data = {}", value.unwrap().0);
        //            }
        //        });

        //        r.seek_result(GREATER_EQUAL, 80, |_, iter| {
        //            for (key, value) in iter {
        //                println!("Key Len = {}", key);
        //                println!("Data = {}", value.unwrap().0);
        //            }
        //            Ok(())
        //        });

        r.seek_min(|_, it| {
            for (key, value) in it.rev() {
                println!("Key Len = {}", key);
                println!("Data = {}", value.unwrap().0);
            }
        });

        //        r.iter(move |it| {
        //            if !it.seek(GREATER_EQUAL, 800) {
        //                println!("Not Found");
        //                return;
        //            }
        //
        //
        //
        //            while it.forward() {
        //                println!("Key Len = {}", it.key());
        //                println!("Data = {}", it.data().unwrap().0);
        //            }
        //        });

        //        let result = r.iter_apply(move |r, it| {
        //            if !it.seek(GREATER_EQUAL, 800) {
        //                println!("Out of Memory");
        //                return Ok("");
        //            }
        //
        //            r.insert(800, MyMsg("moved"));
        //            it.seek(GREATER_EQUAL, 800);
        //
        //            if it.eof() {
        //                println!("Not Found");
        //                return Ok("");
        //            }
        //
        //            while it.back() {
        //                println!("Key Len = {}", it.key());
        //                println!("Data = {}", it.data().unwrap().0);
        //            }
        //
        //            Ok("")
        //        });
    }
}