sekiro 0.14.0

use std::ptr::NonNull;

use crate::dlkr::DLAllocator;

use super::FD4BasicHashString;
use shared::{Subclass, Superclass};

/// Represents a managed resource. The data it represents is immediately handed
/// over to other systems and the ResCap serves as a token for unloading things.
///
/// For example, where the file associated with a gparam `FD4FileCap` is parsed,
/// multiple [FD4ResCap]s are created from the `FD4FileCap`, and the
/// [FD4ResCap]s individually post the data they represent to associated
/// sub-systems. For `GParamResCaps` that means posting the [FD4ResCap]s to the
/// gparam blending system as well as a bunch of other GX structures.
///
/// Source of name: RTTI
#[repr(C)]
#[derive(Superclass)]
pub struct FD4ResCap {
    vftable: usize,

    /// The name of the resource this contains. This may be empty, such as for
    /// repositories that contain further resources.
    pub name: FD4BasicHashString,

    /// The repository this resource is hosted in.
    pub owning_repository: Option<NonNull<FD4ResCapHolder<FD4ResCap>>>,

    /// The next item in the linked list for the bucket in
    /// [Self::owning_repository] that this occupies. `None` if this is the last
    /// element in the list.
    pub next_item: Option<NonNull<FD4ResCap>>,

    _unk58: u64,
    _unk60: u64,
}

/// A hash table of [FD4ResCap]s indexed by [FD4ResCap::name].
///
/// The resource is hashed to a u32 using some FNV variant (using
/// [FD4BasicHashString::hash]). That hash is then modulo'd by
/// [FD4ResCapHolder::bucket_count] to find the appropriate bucket. Collisions
/// are added as the head of the [FD4ResCap::next_item] linked list.
///
/// ```ignore
/// Bucket # = fnv(resource name) % bucket count
///
/// +----------------------------------------------------------....
/// |               FD4ResCapHolder<T>'s map
/// +----------------------------------------------+-----------....
/// |  Bucket 0     |  Bucket 1     |  Bucket 2    |  Bucket 3
/// +---------------+---------------+--------------+-----------....
/// |  FD4ResCap    |  FD4ResCap    |              |  FD4ResCap
/// |  FD4ResCap    |               |              |  FD4ResCap
/// |  FD4ResCap    |               |              |
/// |               |               |              |
/// |               |               |              |
/// +---------------+---------------+--------------+-----------....
/// ```
#[repr(C)]
pub struct FD4ResCapHolder<T>
where
    T: Subclass<FD4ResCap>,
{
    vftable: usize,

    /// The allocator used to expand this if necessary while adding data.
    pub allocator: &'static DLAllocator,

    _unk10: u64,
    _unk18: u32,

    /// The size of the array pointed to be [Self::buckets].
    pub bucket_count: u32,

    /// The buckets this repository contains.
    pub buckets: NonNull<Option<NonNull<T>>>,
}

impl<T> FD4ResCapHolder<T>
where
    T: Subclass<FD4ResCap>,
{
    /// An immutable iterator over this holder's entries, in no guaranteed
    /// order.
    pub fn entries<'a>(&'a self) -> impl Iterator<Item = &'a T> + 'a {
        // For immutable iteration we can store the current chain pointer (if any)
        // and an index into the bucket array.
        struct Iter<'a, T: Subclass<FD4ResCap>> {
            buckets_ptr: *const Option<NonNull<T>>,
            bucket_count: usize,
            current_bucket: usize,
            current_ptr: Option<NonNull<T>>,
            _marker: std::marker::PhantomData<&'a T>,
        }

        impl<'a, T: Subclass<FD4ResCap>> Iterator for Iter<'a, T> {
            type Item = &'a T;
            fn next(&mut self) -> Option<Self::Item> {
                unsafe {
                    // If there is no current pointer, try to advance to the next bucket.
                    while self.current_ptr.is_none() && self.current_bucket < self.bucket_count {
                        let bucket = *self.buckets_ptr.add(self.current_bucket);
                        self.current_bucket += 1;
                        if bucket.is_some() {
                            self.current_ptr = bucket;
                            break;
                        }
                    }
                    // If we have an element, yield it and update current_ptr from its chain.
                    if let Some(ptr) = self.current_ptr {
                        let item = ptr.as_ref();
                        // Copy the next pointer (avoiding borrowing the field).
                        // It's safe to cast here because we know everything in
                        // the container is (a subclass of) T.
                        let next = item.superclass().next_item.map(|p| p.cast());
                        self.current_ptr = next;
                        Some(item)
                    } else {
                        None
                    }
                }
            }
        }

        let buckets_ptr = self.buckets.as_ptr() as *const Option<NonNull<T>>;
        let bucket_count = self.bucket_count as usize;
        Iter {
            buckets_ptr,
            bucket_count,
            current_bucket: 0,
            current_ptr: None,
            _marker: std::marker::PhantomData,
        }
    }

    /// A mutable iterator over this holder's entries, in no guaranteed order.
    pub fn entries_mut<'a>(&'a mut self) -> impl Iterator<Item = &'a mut T> + 'a {
        struct IterMut<'a, T: Subclass<FD4ResCap>> {
            buckets_ptr: *const Option<NonNull<T>>,
            bucket_count: usize,
            current_bucket: usize,
            current_ptr: Option<NonNull<T>>,
            _marker: std::marker::PhantomData<&'a mut T>,
        }

        impl<'a, T: Subclass<FD4ResCap>> Iterator for IterMut<'a, T> {
            type Item = &'a mut T;
            fn next(&mut self) -> Option<Self::Item> {
                unsafe {
                    // If there's no current chain element, advance to the next bucket.
                    while self.current_ptr.is_none() && self.current_bucket < self.bucket_count {
                        let bucket = *self.buckets_ptr.add(self.current_bucket);
                        self.current_bucket += 1;
                        if bucket.is_some() {
                            self.current_ptr = bucket;
                            break;
                        }
                    }
                    // If we have an element, yield it and update from its chain.
                    if let Some(mut ptr) = self.current_ptr {
                        // Obtain a mutable reference from the pointer.
                        // This is safe because our iterator holds unique access.
                        let item = ptr.as_mut();
                        // Copy out the next pointer.
                        let next = item.superclass_mut().next_item.map(|p| p.cast());
                        self.current_ptr = next;
                        Some(item)
                    } else {
                        None
                    }
                }
            }
        }

        // Note: Although self.buckets is stored as NonNull<Option<NonNull<T>>>,
        // we only need its pointer for bucket iteration.
        let buckets_ptr = self.buckets.as_ptr() as *const Option<NonNull<T>>;
        let bucket_count = self.bucket_count as usize;
        IterMut {
            buckets_ptr,
            bucket_count,
            current_bucket: 0,
            current_ptr: None,
            _marker: std::marker::PhantomData,
        }
    }
}