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/*!
Traits for types wrapped in `VirtualWrapper<_>`
*/

use std::{mem,marker::PhantomData};

use crate::{
    erased_types::{GetImplFlags, VirtualWrapperTrait},
    std_types::{RBoxError, RCow, RStr,StaticStr,utypeid::new_utypeid},
    version::VersionStrings,
    return_value_equality::ReturnValueEquality,
};

use super::TypeInfo;

#[allow(unused_imports)]
use crate::type_level_bool::{False, True};

/**
An `implementation type`,
with an associated `interface type` which describes the traits that 
must be implemented when constructing a `VirtualWrapper` from Self,
using the `from_value` and `from_ptr` constructors,
so as to pass an opaque type across ffi.

To initialize `INFO` you can use the `impl_get_type_info` macro.

# Uniqueness

Users of this trait can't enforce that they are the only ones with the same interface,
therefore they should handle the `Err(..)`s returned
from the `VirtualWrapper::*_unerased` functions whenever
the convert back and forth between `Self` and `Self::Interface`.


*/
pub trait ImplType: Sized + 'static + Send + Sync {
    type Interface: InterfaceType;

    const INFO: &'static TypeInfo;
}

/**
Defines the usable/required traits when creating a 
`VirtualWrapper<Pointer<OpaqueType< ThisType >>>`
from a type that implements `ImplType<Interface= ThisType >` .

The value of every one of these associated types is `True`/`False`.

On `True`,the trait would be required by and usable in `VirtualWrapper`.

On `False`,the trait would not be required by and not usable in `VirtualWrapper`.

*/
pub trait InterfaceType: Sized + 'static + Send + Sync + GetImplFlags {
    type Clone;

    type Default;

    type Display;

    type Debug;

    type Serialize;

    type Eq;

    type PartialEq;

    type Ord;

    type PartialOrd;

    type Hash;

    type Deserialize;

    // type FmtWrite;
    // type IoWrite;
    // type IoRead;
    // type IoBufRead;
}



/**
Describes how this `implementation type` is serialized.
*/
pub trait SerializeImplType: ImplType {
    fn serialize_impl<'a>(&'a self) -> Result<RCow<'a, str>, RBoxError>;
}

/**
Describes how this `interface type` is deserialized.

Generally this delegates to a library function,so that the implementation can be delegated
to the `implementation crate`.

*/
pub trait DeserializeInterfaceType: InterfaceType<Deserialize = True> {
    type Deserialized: VirtualWrapperTrait<Interface = Self>;

    fn deserialize_impl(s: RStr<'_>) -> Result<Self::Deserialized, RBoxError>;
}



/////////////////////////////////////////////////////////////////////



//////////////////////////////////////////////////////////////////


/// Helper struct for Wrapping any type in a 
/// `VirtualWrapper<Pointer< OpaqueTyoe< Interface > >>`.
pub struct InterfaceFor<T,Interface>(
    PhantomData<fn()->(T,Interface)>
);

impl<T,Interface> ImplType for InterfaceFor<T,Interface>
where 
    Interface:InterfaceType,
    T:'static,
{
    type Interface=Interface;
    
    const INFO:&'static TypeInfo=&TypeInfo{
        size:mem::size_of::<T>(),
        alignment:mem::align_of::<T>(),
        uid:ReturnValueEquality{
            function:new_utypeid::<T>
        },
        name:StaticStr::new("<erased>"),
        file:StaticStr::new("<unavailable>"),
        package:StaticStr::new("<unavailable>"),
        package_version:VersionStrings{
            major:StaticStr::new("99"),
            minor:StaticStr::new("99"),
            patch:StaticStr::new("99"),
        },
        _private_field:(),
    };
}


/////////////////////////////////////////////////////////////////////


impl InterfaceType for () {
    type Clone=False;

    type Default=False;

    type Display=False;

    type Debug=False;

    type Serialize=False;

    type Eq=False;

    type PartialEq=False;

    type Ord=False;

    type PartialOrd=False;

    type Hash=False;

    type Deserialize=False;
}