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use crate::{
    ser::{SeekSerializer, Serializer},
    util::AlignedVec,
    Archive, ArchiveUnsized, Fallible, RelPtr, Unreachable,
};
use core::{
    borrow::{Borrow, BorrowMut},
    mem,
};
use std::io;

/// Wraps a type that implements [`io::Write`](std::io::Write) and equips it with [`Serializer`].
///
/// ## Examples
/// ```
/// use rkyv::ser::{serializers::WriteSerializer, Serializer};
///
/// let mut serializer = WriteSerializer::new(Vec::new());
/// assert_eq!(serializer.pos(), 0);
/// serializer.write(&[0u8, 1u8, 2u8, 3u8]);
/// assert_eq!(serializer.pos(), 4);
/// let buf = serializer.into_inner();
/// assert_eq!(buf.len(), 4);
/// assert_eq!(buf, vec![0u8, 1u8, 2u8, 3u8]);
/// ```
pub struct WriteSerializer<W: io::Write> {
    inner: W,
    pos: usize,
}

impl<W: io::Write> WriteSerializer<W> {
    /// Creates a new serializer from a writer.
    #[inline]
    pub fn new(inner: W) -> Self {
        Self::with_pos(inner, 0)
    }

    /// Creates a new serializer from a writer, and assumes that the underlying writer is currently
    /// at the given position.
    #[inline]
    pub fn with_pos(inner: W, pos: usize) -> Self {
        Self { inner, pos }
    }

    /// Consumes the serializer and returns the internal writer used to create it.
    #[inline]
    pub fn into_inner(self) -> W {
        self.inner
    }
}

impl<W: io::Write> Fallible for WriteSerializer<W> {
    type Error = io::Error;
}

impl<W: io::Write> Serializer for WriteSerializer<W> {
    #[inline]
    fn pos(&self) -> usize {
        self.pos
    }

    #[inline]
    fn write(&mut self, bytes: &[u8]) -> Result<(), Self::Error> {
        self.pos += self.inner.write(bytes)?;
        Ok(())
    }
}

impl<W: io::Write + io::Seek> SeekSerializer for WriteSerializer<W> {
    #[inline]
    fn seek(&mut self, offset: usize) -> Result<(), Self::Error> {
        self.inner.seek(io::SeekFrom::Start(offset as u64))?;
        self.pos = offset;
        Ok(())
    }
}

/// A serializer made specifically to work with [`AlignedVec`](crate::util::AlignedVec).
///
/// This serializer makes it easier for the compiler to perform emplacement optimizations and may
/// give better performance than a basic `WriteSerializer`.
pub struct AlignedSerializer<A> {
    inner: A,
}

impl<A: Borrow<AlignedVec>> AlignedSerializer<A> {
    /// Creates a new `AlignedSerializer` by wrapping a `Borrow<AlignedVec>`.
    #[inline]
    pub fn new(inner: A) -> Self {
        Self { inner }
    }

    /// Consumes the serializer and returns the underlying type.
    #[inline]
    pub fn into_inner(self) -> A {
        self.inner
    }
}

impl<A> Fallible for AlignedSerializer<A> {
    type Error = Unreachable;
}

impl<A: Borrow<AlignedVec> + BorrowMut<AlignedVec>> Serializer for AlignedSerializer<A> {
    #[inline]
    fn pos(&self) -> usize {
        self.inner.borrow().len()
    }

    #[inline]
    fn write(&mut self, bytes: &[u8]) -> Result<(), Self::Error> {
        self.inner.borrow_mut().extend_from_slice(bytes);
        Ok(())
    }

    #[inline]
    unsafe fn resolve_aligned<T: Archive + ?Sized>(
        &mut self,
        value: &T,
        resolver: T::Resolver,
    ) -> Result<usize, Self::Error> {
        let pos = self.pos();
        debug_assert!(pos & (mem::align_of::<T::Archived>() - 1) == 0);
        let vec = self.inner.borrow_mut();
        let additional = mem::size_of::<T::Archived>();
        vec.reserve(additional);
        vec.set_len(vec.len() + additional);

        let ptr = vec
            .as_mut_ptr()
            .add(pos)
            .cast::<mem::MaybeUninit<T::Archived>>();
        ptr.write_bytes(0, 1);

        value.resolve(pos, resolver, &mut *ptr);
        Ok(pos)
    }

    #[inline]
    unsafe fn resolve_unsized_aligned<T: ArchiveUnsized + ?Sized>(
        &mut self,
        value: &T,
        to: usize,
        metadata_resolver: T::MetadataResolver,
    ) -> Result<usize, Self::Error> {
        let from = self.pos();
        debug_assert!(from & (mem::align_of::<RelPtr<T::Archived>>() - 1) == 0);
        let vec = self.inner.borrow_mut();
        let additional = mem::size_of::<RelPtr<T::Archived>>();
        vec.reserve(additional);
        vec.set_len(vec.len() + additional);

        let ptr = vec
            .as_mut_ptr()
            .add(from)
            .cast::<mem::MaybeUninit<RelPtr<T::Archived>>>();
        ptr.write_bytes(0, 1);

        value.resolve_unsized(from, to, metadata_resolver, &mut *ptr);
        Ok(from)
    }
}