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use crate::allocators::allocator::Allocator;
use crate::allocators::bit_set::bit_set_allocator::BitSetAllocator;
use crate::allocators::bump_allocator::BumpAllocator;
use crate::allocators::global::local_allocator::LocalAllocator;
use crate::allocators::global::memory_range::MemoryRange;
use crate::allocators::multiple_binary_search_tree_allocator::MultipleBinarySearchTreeAllocator;

use crate::memory_address::MemoryAddress;
use crate::memory_sources::memory_source::MemorySource;
use std::alloc::AllocErr;
use std::fmt::Debug;
use std::num::NonZeroUsize;

/// An allocator designed for contexts with different lifetimes.
///
/// This allocator NEVER grows or shrinks its memory region.
///
/// This allocator is not thread-safe.
#[derive(Debug)]
pub enum ContextAllocator<MS: MemorySource> {
    /// Use this variant for contexts with short-lived lifetimes.
    ///
    /// Very fast allocation and almost costless deallocation, at the expense of the strong likelihood of running out of memory.
    ///
    /// Reallocation is very expensive when growing unless reallocating the most recently made allocation.
    ShortLived(BumpAllocator<MS>),

    /// Use this variant for contexts with slightly longer than short-lived lifetimes.
    ///
    /// Slower allocation and deallocation but reallocation is less expensive than for `ShortLived`.
    MediumLived(BitSetAllocator<MS>),

    /// Use this variant for contexts with long-lived lifetimes.
    LongLived(MultipleBinarySearchTreeAllocator<MS>),
}

impl<MS: MemorySource> Allocator for ContextAllocator<MS> {
    #[inline(always)]
    fn allocate(
        &self,
        non_zero_size: NonZeroUsize,
        non_zero_power_of_two_alignment: NonZeroUsize,
    ) -> Result<MemoryAddress, AllocErr> {
        use self::ContextAllocator::*;

        match *self {
            ShortLived(ref allocator) => {
                allocator.allocate(non_zero_size, non_zero_power_of_two_alignment)
            }

            MediumLived(ref allocator) => {
                allocator.allocate(non_zero_size, non_zero_power_of_two_alignment)
            }

            LongLived(ref allocator) => {
                allocator.allocate(non_zero_size, non_zero_power_of_two_alignment)
            }
        }
    }

    #[inline(always)]
    fn deallocate(
        &self,
        non_zero_size: NonZeroUsize,
        non_zero_power_of_two_alignment: NonZeroUsize,
        current_memory: MemoryAddress,
    ) {
        use self::ContextAllocator::*;

        match *self {
            ShortLived(ref allocator) => allocator.deallocate(
                non_zero_size,
                non_zero_power_of_two_alignment,
                current_memory,
            ),

            MediumLived(ref allocator) => allocator.deallocate(
                non_zero_size,
                non_zero_power_of_two_alignment,
                current_memory,
            ),

            LongLived(ref allocator) => allocator.deallocate(
                non_zero_size,
                non_zero_power_of_two_alignment,
                current_memory,
            ),
        }
    }

    #[inline(always)]
    fn growing_reallocate(
        &self,
        non_zero_new_size: NonZeroUsize,
        non_zero_power_of_two_alignment: NonZeroUsize,
        non_zero_current_size: NonZeroUsize,
        current_memory: MemoryAddress,
    ) -> Result<MemoryAddress, AllocErr> {
        use self::ContextAllocator::*;

        match *self {
            ShortLived(ref allocator) => allocator.growing_reallocate(
                non_zero_new_size,
                non_zero_power_of_two_alignment,
                non_zero_current_size,
                current_memory,
            ),

            MediumLived(ref allocator) => allocator.growing_reallocate(
                non_zero_new_size,
                non_zero_power_of_two_alignment,
                non_zero_current_size,
                current_memory,
            ),

            LongLived(ref allocator) => allocator.growing_reallocate(
                non_zero_new_size,
                non_zero_power_of_two_alignment,
                non_zero_current_size,
                current_memory,
            ),
        }
    }

    #[inline(always)]
    fn shrinking_reallocate(
        &self,
        non_zero_new_size: NonZeroUsize,
        non_zero_power_of_two_alignment: NonZeroUsize,
        non_zero_current_size: NonZeroUsize,
        current_memory: MemoryAddress,
    ) -> Result<MemoryAddress, AllocErr> {
        use self::ContextAllocator::*;

        match *self {
            ShortLived(ref allocator) => allocator.shrinking_reallocate(
                non_zero_new_size,
                non_zero_power_of_two_alignment,
                non_zero_current_size,
                current_memory,
            ),

            MediumLived(ref allocator) => allocator.shrinking_reallocate(
                non_zero_new_size,
                non_zero_power_of_two_alignment,
                non_zero_current_size,
                current_memory,
            ),

            LongLived(ref allocator) => allocator.shrinking_reallocate(
                non_zero_new_size,
                non_zero_power_of_two_alignment,
                non_zero_current_size,
                current_memory,
            ),
        }
    }
}

impl<MS: MemorySource> LocalAllocator for ContextAllocator<MS> {
    #[inline(always)]
    fn memory_range(&self) -> MemoryRange {
        use self::ContextAllocator::*;

        match *self {
            ShortLived(ref allocator) => allocator.memory_range(),

            MediumLived(ref allocator) => allocator.memory_range(),

            LongLived(ref allocator) => allocator.memory_range(),
        }
    }
}