//! Traits describing individual records
//!
//! This module defines two traits:
//! * `Record` describes how a type can be treated
//!   as a record.  If you are writing a custom record
//!   type, this is the trait to implement.
//! * `Record` provides methods for user code to work
//!   with records, it is automatically implemented for
//!   all types that implement `Record` with an
//!   appropriate `Header`.

use crate::prelude::*;

use crate::col::{Col, ColProxy};
use crate::header::{Header, HasCol, AsListRefs};

pub mod proj;
pub mod tuple;
pub mod rename;

/// Required methods for implementing a record
///
/// Implementing this trait marks a type as a record type, and
/// the `Record` extenstion methods will be automatically
/// provided.
pub trait Record:Sized + Clone {
    type Cols: Header;

    fn into_cols(self)->Self::Cols {
        self.clone_cols()
    }

    fn clone_cols(&self)->Self::Cols {
        Self::Cols::clone_from_rec_unchecked(self)
    }

    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
        self.col_opt::<C>().unwrap()
    }

    fn col_opt<C:Col>(&self)->Option<&C>;

    fn project<NewCols:Header>(self) -> proj::Projection<Self, NewCols>
    where NewCols: ProjectFrom<Self::Cols> {
        proj::Projection::new(self)
    }

    fn project_into<R:FromRecord<Self::Cols>>(self)->R {
        R::from_rec(self).0
    }

    fn rename_col<A:Col, B:Col<Inner=A>>(self)->rename::Rename<Self,A,B>
    where rename::Rename<Self,A,B>: Record {
        rename::Rename { inner: self, cols: std::marker::PhantomData }
    }
}

pub struct ErasedExtRecord<'a,Cols: Header>(
    <Cols as AsListRefs<'a>>::AsRefs
);

impl<'a, H:Header> Copy for ErasedExtRecord<'a,H> {}
impl<'a, H:Header> Clone for ErasedExtRecord<'a,H> {
    fn clone(&self)->Self { *self }
}

impl<'a,Cols:Header> Record for ErasedExtRecord<'a,Cols>
where <Cols as AsListRefs<'a>>::AsRefs: ExternalRecord<'a, Cols=Cols> {
    type Cols = Cols;

    fn into_cols(self)->Self::Cols { self.0.into_cols() }
    fn clone_cols(&self)->Self::Cols { self.0.clone_cols() }
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> { self.0.col_ref() }
    fn col_opt<C:Col>(&self)->Option<&C> { self.0.col_opt() }
}

impl<'a,Cols:Header> ExternalRecord<'a> for ErasedExtRecord<'a,Cols>
where <Cols as AsListRefs<'a>>::AsRefs: ExternalRecord<'a, Cols=Cols> {
    fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
        self.0.ext_col_ref()
    }
    fn ext_col_opt<C:Col>(&self)->Option<&'a C> {
        self.0.ext_col_opt()
    }
}

impl<'a,Cols:Header> FromExternalRecord<'a> for ErasedExtRecord<'a,Cols>
{
    type Cols = Cols;
    fn from_ext_rec_raw(r:impl ExternalRecord<'a, Cols=Cols>)->Self {
        ErasedExtRecord(
            Cols::ref_from_ext_rec_unchecked(r)
        )
    }
}

pub trait ExternalRecord<'a>: Record + Copy {
    fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
        self.ext_col_opt::<C>().unwrap()
    }

    fn ext_col_opt<C:Col>(&self)->Option<&'a C>;

    fn erase_type(self)->ErasedExtRecord<'a, Self::Cols> {
        ErasedExtRecord::from_ext_rec_raw(self)
    }
}

impl<'a, R:Record> ExternalRecord<'a> for &'a R {
    fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
        <R as Record>::col_ref(self)
    }
    fn ext_col_opt<C:Col>(&self)->Option<&'a C> {
        <R as Record>::col_opt(self)
    }
}

impl<'a> ExternalRecord<'a> for HNil {
    fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
        unreachable!();
    }
    fn ext_col_opt<C:Col>(&self)->Option<&'a C> {
        None
    }
}

impl<'a,R> ExternalRecord<'a> for OpaqueRecord<R>
where R:ExternalRecord<'a> {
    fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
        self.0.ext_col_ref()
    }
    fn ext_col_opt<C:Col>(&self)->Option<&'a C> {
        self.0.ext_col_opt()
    }
}

impl<'a,H,T> ExternalRecord<'a> for HCons<&'a H, T>
where
    H: Col,
    T: ExternalRecord<'a>,
    Self: Record
{
    fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
        self.ext_col_opt().unwrap()
    }
    fn ext_col_opt<C:Col>(&self)->Option<&'a C> {
        if std::any::TypeId::of::<C>() == std::any::TypeId::of::<H>() {
            // Safety: These are the same type and have the same
            //         lifetime
            Some(unsafe { &*(self.head as *const H as *const C) })
        } else {
            self.tail.ext_col_opt()
        }
    }
}

#[derive(Copy,Clone,Default,Eq,PartialEq,Ord,PartialOrd,Hash)]
#[repr(transparent)]
pub struct OpaqueRecord<R>(R);

impl<R> OpaqueRecord<R> {
    pub fn new(r:R)->Self { OpaqueRecord(r) }
}

impl<R:Record> Record for OpaqueRecord<R> {
    type Cols = R::Cols;

    #[inline(always)]
    fn into_cols(self)->Self::Cols { self.0.into_cols() }
    #[inline(always)]
    fn clone_cols(&self)->Self::Cols { self.0.clone_cols() }
    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> { self.0.col_ref() }
    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C> { self.0.col_opt() }
}

impl Record for HNil {
    type Cols = HNil;

    #[inline(always)]
    fn into_cols(self)->HNil { HNil }

    #[inline(always)]
    fn clone_cols(&self)->HNil { HNil }

    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C
    { unreachable!() }

    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C>
    { None }
}


impl<H:ColProxy, T:Record> Record for HCons<H,T>
where HCons<H::For, T::Cols>: Header, Self:Clone
{
    type Cols = HCons<H::For, T::Cols>;

    #[inline(always)]
    fn into_cols(self)->Self::Cols {
        HCons { head: self.head.into_col(),
                tail: self.tail.into_cols() }
    }

    #[inline(always)]
    fn clone_cols(&self)->Self::Cols {
        HCons { head: self.head.col_ref().clone(),
                tail: self.tail.clone_cols() }
    }

    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
        self.col_opt().unwrap_or_else(|| unreachable!())
    }

    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C> {
        (self.head.col_ref() as &dyn ::core::any::Any)
            .downcast_ref()
            .or_else(|| self.tail.col_opt())
    }
}

pub trait BorrowRecord {
    type Cols: Header;
    type Inner: Record<Cols=Self::Cols> + ?Sized;
    fn borrow_rec(&self) -> &Self::Inner;
}

impl<R:Record + ?Sized> BorrowRecord for R {
    type Cols = R::Cols;
    type Inner = R;
    #[inline(always)]
    fn borrow_rec(&self)->&Self::Inner { self }
}

impl<'a, Ptr:BorrowRecord+?Sized> Record for &'a Ptr {
    type Cols = Ptr::Cols;
    
    #[inline(always)]
    fn into_cols(self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(self))
    }

    #[inline(always)]
    fn clone_cols(&self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(*self))
    }

    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
        Ptr::Inner::col_ref(Ptr::borrow_rec(*self))
    }

    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C> {
        Ptr::Inner::col_opt(Ptr::borrow_rec(*self))
    }
}

impl<Ptr: BorrowRecord+?Sized> Record for std::rc::Rc<Ptr> {
    type Cols = Ptr::Cols;
    
    #[inline(always)]
    fn into_cols(self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(&self))
    }

    #[inline(always)]
    fn clone_cols(&self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(&*self))
    }

    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
        Ptr::Inner::col_ref(Ptr::borrow_rec(&*self))
    }

    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C> {
        Ptr::Inner::col_opt(Ptr::borrow_rec(&*self))
    }
}

impl<Ptr: BorrowRecord+?Sized> Record for std::sync::Arc<Ptr> {
    type Cols = Ptr::Cols;
    
    #[inline(always)]
    fn into_cols(self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(&self))
    }

    #[inline(always)]
    fn clone_cols(&self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(&*self))
    }

    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
        Ptr::Inner::col_ref(Ptr::borrow_rec(&*self))
    }

    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C> {
        Ptr::Inner::col_opt(Ptr::borrow_rec(&*self))
    }
}

impl<Ptr: BorrowRecord+Clone> Record for std::boxed::Box<Ptr> {
    type Cols = Ptr::Cols;
    
    #[inline(always)]
    fn into_cols(self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(&self))
    }

    #[inline(always)]
    fn clone_cols(&self)->Self::Cols {
        Ptr::Inner::clone_cols(Ptr::borrow_rec(&*self))
    }

    #[inline(always)]
    fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
        Ptr::Inner::col_ref(Ptr::borrow_rec(&*self))
    }

    #[inline(always)]
    fn col_opt<C:Col>(&self)->Option<&C> {
        Ptr::Inner::col_opt(Ptr::borrow_rec(&*self))
    }
}


impl<H,T> FromRecordImpl for HCons<H,T> where Self:Header {
    type Cols = Self;
    fn from_rec_raw(rec: impl Record<Cols=Self::Cols>)->Self {
        rec.into_cols()
    }
}

pub trait FromRecordImpl: Sized {
    type Cols: Header;

    fn from_rec_raw(rec: impl Record<Cols=Self::Cols>)->Self;
}

pub trait FromRecord<SrcCols:Header>: Sized {
    type Remainder: Header;

    fn from_rec(rec: impl Record<Cols=SrcCols>)->(Self, Self::Remainder);
}

pub trait FromRecordUnchecked<'a>: Sized {
    fn from_ref_unchecked(_:&impl ExternalRecord<'a>)->Self;
}

impl<'a> FromRecordUnchecked<'a> for HNil {
    fn from_ref_unchecked(_:&impl ExternalRecord<'a>)->Self { HNil }
}

impl<'a,H:Col,T:FromRecordUnchecked<'a>>
FromRecordUnchecked<'a> for HCons<&'a H,T> {
    fn from_ref_unchecked(r:&impl ExternalRecord<'a>)->Self {
        HCons { head: r.ext_col_opt::<H>().unwrap(),
                tail: T::from_ref_unchecked(r) }
    }
}

pub trait FromExternalRecord<'a>: Sized {
    type Cols: Header;
    fn from_ext_rec_raw(rec: impl ExternalRecord<'a, Cols=Self::Cols>)->Self;

    fn from_ext_rec<H>(rec: impl ExternalRecord<'a, Cols=H>)->Self
    where H:Header, Self::Cols: ProjectFrom<H> {
        Self::from_ext_rec_raw(rec.project())
    }
}

impl<'a> FromExternalRecord<'a> for HNil {
    type Cols = HNil;
    fn from_ext_rec_raw(_: impl ExternalRecord<'a, Cols=Self::Cols>)->Self {
        HNil
    }
}

impl<'a,H,T> FromExternalRecord<'a> for HCons<H, T>
where H:FromExternalRecord<'a>,
      H: ColProxy,
//      Self: ExternalRecord<'a, Cols=HCons<H,T::Cols>>,
      T:FromExternalRecord<'a>,
      HCons<H::For,T::Cols>: Header {
    type Cols = HCons<H::For,T::Cols>;
    fn from_ext_rec_raw(rec: impl ExternalRecord<'a, Cols=Self::Cols>)->Self {
        HCons {
            head: H::from_ext_rec_raw(proj::Projection::new_unchecked(rec)),
            tail: T::from_ext_rec_raw(proj::Projection::new_unchecked(rec))
        }
    }
}

/*
impl<'a> FromExternalRecord<'a> for ... where Self:FromRecordImpl {
    type Cols = <Self as FromRecordImpl>::Cols;
    fn from_ext_rec_raw(rec: impl ExternalRecord<'a, Cols=Self::Cols>)->Self {
        Self::from_rec(rec)
    }
}
*/

use crate::header::{ProjectFrom, ProjectRefFrom};
impl<T:FromRecordImpl, SrcCols:Header> FromRecord<SrcCols> for T
where T::Cols: ProjectFrom<SrcCols> + Record<Cols=T::Cols>
{
    type Remainder = <T::Cols as ProjectFrom<SrcCols>>::Remainder;

    #[inline(always)]
    fn from_rec(rec: impl Record<Cols=SrcCols>)->(Self, Self::Remainder) {
        let (cols, remainder) = T::Cols::project_from(rec.into_cols());
        (Self::from_rec_raw(cols), remainder)
    }
}

#[test]
fn test() {
    col!{pub A: u32};
    col!{pub B: &'static str};

    use tylisp::sexpr;

    assert_trait!{ HNil: Record };
    assert_trait!{ sexpr!{A}: Record };
    assert_trait!{ sexpr!{std::rc::Rc<A>, &B}: Record<Cols=sexpr!{A,B}> };
    assert_trait!{ sexpr!{std::rc::Rc<A>}: Record };
    assert_trait!{ &sexpr!{std::rc::Rc<A>, &B}: Record<Cols=sexpr!{A,B}> };
    fn f(_:impl Record) {}
    f(HNil);
//    f(tylisp::sexpr_val!{A(4)});
}