//! Functions and types related to the layout checking.

use std::{cmp::Ordering, fmt, mem};

#[allow(unused_imports)]
use core_extensions::{matches, SelfOps};

use std::{
    borrow::Borrow,
    cell::Cell,
    collections::hash_map::{Entry, HashMap},
};

use crate::{
    abi_stability::{
        extra_checks::{
            ExtraChecksBox, ExtraChecksError, ExtraChecksRef, TypeChecker, TypeCheckerMut,
        },
        ConstGeneric,
    },
    prefix_type::{FieldAccessibility, FieldConditionality},
    sabi_types::{CmpIgnored, ParseVersionError, VersionStrings},
    std_types::{RArc, RBox, RBoxError, RErr, RNone, ROk, RResult, RSome, RStr, RVec, UTypeId},
    traits::IntoReprC,
    type_layout::{
        tagging::TagErrors, FmtFullType, IncompatibleWithNonExhaustive, IsExhaustive, ReprAttr,
        TLData, TLDataDiscriminant, TLDiscriminant, TLEnum, TLField, TLFieldOrFunction, TLFunction,
        TLNonExhaustive, TLPrimitive, TypeLayout,
    },
    type_level::downcasting::TD_Opaque,
    utils::{max_by, min_max_by},
};

mod errors;

pub use self::errors::{
    AbiInstability, AbiInstability as AI, AbiInstabilityError, AbiInstabilityErrors,
    ExtraCheckError,
};

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

/// What is AbiChecker::check_fields being called with.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Ord, PartialOrd, Hash)]
#[repr(C)]
enum FieldContext {
    Fields,
    Subfields,
    PhantomFields,
}

//////

#[derive(Debug, Copy, Clone, PartialEq, Eq, Ord, PartialOrd, Hash)]
#[repr(C)]
struct CheckingUTypeId {
    type_id: UTypeId,
}

impl CheckingUTypeId {
    fn new(this: &'static TypeLayout) -> Self {
        Self {
            type_id: this.get_utypeid(),
        }
    }
}

//////

#[derive(Debug, PartialEq, Eq, Ord, PartialOrd, Hash)]
pub enum CheckingState {
    Checking { layer: u32 },
    Compatible,
    Error,
}

//////

/// Represents an error where a value was expected,but another value was found.
#[derive(Debug, PartialEq, Eq, Clone)]
#[repr(C)]
pub struct ExpectedFound<T> {
    pub expected: T,
    pub found: T,
}

#[allow(clippy::missing_const_for_fn)]
impl<T> ExpectedFound<T> {
    pub fn new<O, F>(this: O, other: O, mut field_getter: F) -> ExpectedFound<T>
    where
        F: FnMut(O) -> T,
    {
        ExpectedFound {
            expected: field_getter(this),
            found: field_getter(other),
        }
    }

    pub fn as_ref(&self) -> ExpectedFound<&T> {
        ExpectedFound {
            expected: &self.expected,
            found: &self.found,
        }
    }

    pub fn map<F, U>(self, mut f: F) -> ExpectedFound<U>
    where
        F: FnMut(T) -> U,
    {
        ExpectedFound {
            expected: f(self.expected),
            found: f(self.found),
        }
    }

    pub fn display_str(&self) -> Option<ExpectedFound<String>>
    where
        T: fmt::Display,
    {
        Some(self.as_ref().map(|x| format!("{:#}", x)))
    }

    pub fn debug_str(&self) -> Option<ExpectedFound<String>>
    where
        T: fmt::Debug,
    {
        Some(self.as_ref().map(|x| format!("{:#?}", x)))
    }
}

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

#[derive(Debug)]
#[repr(C)]
pub struct CheckedPrefixTypes {
    this: &'static TypeLayout,
    this_prefix: __PrefixTypeMetadata,
    other: &'static TypeLayout,
    other_prefix: __PrefixTypeMetadata,
}

#[derive(Debug, Copy, Clone)]
#[repr(C)]
pub struct NonExhaustiveEnumWithContext {
    layout: &'static TypeLayout,
    enum_: TLEnum,
    nonexhaustive: &'static TLNonExhaustive,
}

#[derive(Debug, Clone)]
#[repr(C)]
pub struct ExtraChecksBoxWithContext {
    t_lay: &'static TypeLayout,
    o_lay: &'static TypeLayout,
    extra_checks: ExtraChecksBox,
}

#[derive(Debug, Copy, Clone)]
#[repr(C)]
pub struct CheckedNonExhaustiveEnums {
    this: NonExhaustiveEnumWithContext,
    other: NonExhaustiveEnumWithContext,
}

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

struct AbiChecker {
    stack_trace: RVec<ExpectedFound<TLFieldOrFunction>>,
    checked_prefix_types: RVec<CheckedPrefixTypes>,
    checked_nonexhaustive_enums: RVec<CheckedNonExhaustiveEnums>,
    checked_extra_checks: RVec<ExtraChecksBoxWithContext>,

    visited: HashMap<(CheckingUTypeId, CheckingUTypeId), CheckingState>,

    errors: RVec<AbiInstabilityError>,

    /// Layer 0 is checking a type layout,
    ///
    /// Layer 1 is checking the type layout
    ///     of a const parameter/ExtraCheck,
    ///
    /// Layer 2 is checking the type layout
    ///     of a const parameter/ExtraCheck
    ///     of a const parameter/ExtraCheck,
    ///
    /// It is an error to attempt to check the layout of types that are
    /// in the middle of being checked in outer layers.
    current_layer: u32,

    error_index: usize,
}

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

impl AbiChecker {
    fn new() -> Self {
        Self {
            stack_trace: RVec::new(),
            checked_prefix_types: RVec::new(),
            checked_nonexhaustive_enums: RVec::new(),
            checked_extra_checks: RVec::new(),

            visited: HashMap::default(),
            errors: RVec::new(),
            current_layer: 0,
            error_index: 0,
        }
    }

    #[inline]
    fn check_fields<I, F>(
        &mut self,
        errs: &mut RVec<AbiInstability>,
        t_lay: &'static TypeLayout,
        o_lay: &'static TypeLayout,
        ctx: FieldContext,
        t_fields: I,
        o_fields: I,
    ) where
        I: ExactSizeIterator<Item = F>,
        F: Borrow<TLField>,
    {
        if t_fields.len() == 0 && o_fields.len() == 0 {
            return;
        }

        let t_data = t_lay.data();

        let is_prefix = match &t_data {
            TLData::PrefixType { .. } => true,
            TLData::Enum(enum_) => !enum_.exhaustiveness.is_exhaustive(),
            _ => false,
        };
        match (t_fields.len().cmp(&o_fields.len()), is_prefix) {
            (Ordering::Greater, _) | (Ordering::Less, false) => {
                push_err(
                    errs,
                    &t_fields,
                    &o_fields,
                    |x| x.len(),
                    AI::FieldCountMismatch,
                );
            }
            (Ordering::Equal, _) | (Ordering::Less, true) => {}
        }

        let acc_fields: Option<(FieldAccessibility, FieldAccessibility)> =
            match (&t_data, &o_lay.data()) {
                (TLData::PrefixType(t_prefix), TLData::PrefixType(o_prefix)) => {
                    Some((t_prefix.accessible_fields, o_prefix.accessible_fields))
                }
                _ => None,
            };

        for (field_i, (this_f, other_f)) in t_fields.zip(o_fields).enumerate() {
            let this_f = this_f.borrow();
            let other_f = other_f.borrow();
            if this_f.name() != other_f.name() {
                push_err(errs, this_f, other_f, |x| *x, AI::UnexpectedField);
                continue;
            }

            let t_field_abi = this_f.layout();
            let o_field_abi = other_f.layout();

            let is_accessible = match (ctx, acc_fields) {
                (FieldContext::Fields, Some((l, r))) => {
                    l.at(field_i).is_accessible() && r.at(field_i).is_accessible()
                }
                _ => true,
            };

            if is_accessible {
                if this_f.lifetime_indices() != other_f.lifetime_indices() {
                    push_err(errs, this_f, other_f, |x| *x, AI::FieldLifetimeMismatch);
                }

                self.stack_trace.push(ExpectedFound {
                    expected: (*this_f).into(),
                    found: (*other_f).into(),
                });

                let sf_ctx = FieldContext::Subfields;

                let func_ranges = this_f.function_range().iter().zip(other_f.function_range());
                for (t_func, o_func) in func_ranges {
                    self.error_index += 1;
                    let errs_index = self.error_index;
                    let mut errs_ = RVec::<AbiInstability>::new();
                    let errs = &mut errs_;

                    self.stack_trace.push(ExpectedFound {
                        expected: t_func.into(),
                        found: o_func.into(),
                    });

                    if t_func.paramret_lifetime_indices != o_func.paramret_lifetime_indices {
                        push_err(errs, t_func, o_func, |x| x, AI::FnLifetimeMismatch);
                    }

                    if t_func.qualifiers() != o_func.qualifiers() {
                        push_err(errs, t_func, o_func, |x| x, AI::FnQualifierMismatch);
                    }

                    self.check_fields(
                        errs,
                        t_lay,
                        o_lay,
                        sf_ctx,
                        t_func.get_params_ret_iter(),
                        o_func.get_params_ret_iter(),
                    );

                    if !errs_.is_empty() {
                        self.errors.push(AbiInstabilityError {
                            stack_trace: self.stack_trace.clone(),
                            errs: errs_,
                            index: errs_index,
                            _priv: (),
                        });
                    }

                    self.stack_trace.pop();
                }

                let _ = self.check_inner(t_field_abi, o_field_abi);
                self.stack_trace.pop();
            } else {
                self.stack_trace.push(ExpectedFound {
                    expected: (*this_f).into(),
                    found: (*other_f).into(),
                });

                let t_field_layout = &t_field_abi;
                let o_field_layout = &o_field_abi;
                if t_field_layout.size() != o_field_layout.size() {
                    push_err(errs, t_field_layout, o_field_layout, |x| x.size(), AI::Size);
                }
                if t_field_layout.alignment() != o_field_layout.alignment() {
                    push_err(
                        errs,
                        t_field_layout,
                        o_field_layout,
                        |x| x.alignment(),
                        AI::Alignment,
                    );
                }
                self.stack_trace.pop();
            }
        }
    }

    fn check_inner(
        &mut self,
        this: &'static TypeLayout,
        other: &'static TypeLayout,
    ) -> Result<(), ()> {
        let t_cuti = CheckingUTypeId::new(this);
        let o_cuti = CheckingUTypeId::new(other);
        let cuti_pair = (t_cuti, o_cuti);

        self.error_index += 1;
        let errs_index = self.error_index;
        let mut errs_ = RVec::<AbiInstability>::new();
        let mut top_level_errs_ = RVec::<AbiInstabilityError>::new();
        let t_lay = &this;
        let o_lay = &other;

        let start_errors = self.errors.len();

        match self.visited.entry(cuti_pair) {
            Entry::Occupied(mut entry) => match entry.get_mut() {
                CheckingState::Checking { layer } if self.current_layer == *layer => return Ok(()),
                cs @ CheckingState::Checking { .. } => {
                    *cs = CheckingState::Error;
                    self.errors.push(AbiInstabilityError {
                        stack_trace: self.stack_trace.clone(),
                        errs: rvec![AbiInstability::CyclicTypeChecking {
                            interface: this,
                            implementation: other,
                        }],
                        index: errs_index,
                        _priv: (),
                    });
                    return Err(());
                }
                CheckingState::Compatible => {
                    return Ok(());
                }
                CheckingState::Error => {
                    return Err(());
                }
            },
            Entry::Vacant(entry) => {
                entry.insert(CheckingState::Checking {
                    layer: self.current_layer,
                });
            }
        }

        (|| {
            let errs = &mut errs_;
            let top_level_errs = &mut top_level_errs_;
            if t_lay.name() != o_lay.name() {
                push_err(errs, t_lay, o_lay, |x| x.full_type(), AI::Name);
                return;
            }
            let (t_package, t_ver_str) = t_lay.package_and_version();
            let (o_package, o_ver_str) = o_lay.package_and_version();
            if t_package != o_package {
                push_err(errs, t_lay, o_lay, |x| x.package(), AI::Package);
                return;
            }

            if this.is_nonzero() != other.is_nonzero() {
                push_err(errs, this, other, |x| x.is_nonzero(), AI::NonZeroness);
            }

            if t_lay.repr_attr() != o_lay.repr_attr() {
                push_err(errs, t_lay, o_lay, |x| x.repr_attr(), AI::ReprAttr);
            }

            {
                let x = (|| {
                    let l = t_ver_str.parsed()?;
                    let r = o_ver_str.parsed()?;
                    Ok(l.is_loosely_compatible(r))
                })();
                match x {
                    Ok(false) => {
                        push_err(
                            errs,
                            t_lay,
                            o_lay,
                            |x| x.package_version(),
                            AI::PackageVersion,
                        );
                    }
                    Ok(true) => {}
                    Err(parse_error) => {
                        errs.push(AI::PackageVersionParseError(parse_error));
                        return;
                    }
                }
            }
            {
                let t_gens = t_lay.generics();
                let o_gens = o_lay.generics();

                let t_consts = t_gens.const_params();
                let o_consts = o_gens.const_params();
                if t_gens.lifetime_count() != o_gens.lifetime_count()
                    || t_gens.const_params().len() != o_gens.const_params().len()
                {
                    push_err(errs, t_lay, o_lay, |x| x.full_type(), AI::GenericParamCount);
                }

                let mut ty_checker = TypeCheckerMut::from_ptr(&mut *self, TD_Opaque);
                for (l, r) in t_consts.iter().zip(o_consts.iter()) {
                    match l.is_equal(r, ty_checker.sabi_reborrow_mut()) {
                        Ok(false) | Err(_) => {
                            push_err(errs, l, r, |x| *x, AI::MismatchedConstParam);
                        }
                        Ok(true) => {}
                    }
                }
            }

            // Checking phantom fields
            self.check_fields(
                errs,
                this,
                other,
                FieldContext::PhantomFields,
                this.phantom_fields().iter(),
                other.phantom_fields().iter(),
            );

            match (t_lay.size().cmp(&o_lay.size()), this.is_prefix_kind()) {
                (Ordering::Greater, _) | (Ordering::Less, false) => {
                    push_err(errs, t_lay, o_lay, |x| x.size(), AI::Size);
                }
                (Ordering::Equal, _) | (Ordering::Less, true) => {}
            }
            if t_lay.alignment() != o_lay.alignment() {
                push_err(errs, t_lay, o_lay, |x| x.alignment(), AI::Alignment);
            }

            let t_discr = t_lay.data_discriminant();
            let o_discr = o_lay.data_discriminant();
            if t_discr != o_discr {
                errs.push(AI::TLDataDiscriminant(ExpectedFound {
                    expected: t_discr,
                    found: o_discr,
                }));
            }

            let t_tag = t_lay.tag().to_checkable();
            let o_tag = o_lay.tag().to_checkable();
            if let Err(tag_err) = t_tag.check_compatible(&o_tag) {
                errs.push(AI::TagError { err: tag_err });
            }

            match (t_lay.extra_checks(), o_lay.extra_checks()) {
                (None, _) => {}
                (Some(_), None) => {
                    errs.push(AI::NoneExtraChecks);
                }
                (Some(t_extra_checks), Some(o_extra_checks)) => {
                    let mut ty_checker = TypeCheckerMut::from_ptr(&mut *self, TD_Opaque);

                    let res = handle_extra_checks_ret(
                        t_extra_checks.clone(),
                        o_extra_checks.clone(),
                        errs,
                        top_level_errs,
                        move || {
                            let ty_checker_ = ty_checker.sabi_reborrow_mut();
                            rtry!(t_extra_checks.check_compatibility(t_lay, o_lay, ty_checker_));

                            let ty_checker_ = ty_checker.sabi_reborrow_mut();
                            let opt = rtry!(t_extra_checks.combine(o_extra_checks, ty_checker_));

                            opt.map(|combined| ExtraChecksBoxWithContext {
                                t_lay,
                                o_lay,
                                extra_checks: combined,
                            })
                            .piped(ROk)
                        },
                    );

                    if let Ok(RSome(x)) = res {
                        self.checked_extra_checks.push(x);
                    }
                }
            }

            match (t_lay.data(), o_lay.data()) {
                (TLData::Opaque { .. }, _) => {
                    // No checks are necessary
                }

                (TLData::Primitive(t_prim), TLData::Primitive(o_prim)) => {
                    if t_prim != o_prim {
                        errs.push(AI::MismatchedPrimitive(ExpectedFound {
                            expected: t_prim,
                            found: o_prim,
                        }));
                    }
                }
                (TLData::Primitive { .. }, _) => {}

                (TLData::Struct { fields: t_fields }, TLData::Struct { fields: o_fields }) => {
                    self.check_fields(
                        errs,
                        this,
                        other,
                        FieldContext::Fields,
                        t_fields.iter(),
                        o_fields.iter(),
                    );
                }
                (TLData::Struct { .. }, _) => {}

                (TLData::Union { fields: t_fields }, TLData::Union { fields: o_fields }) => {
                    self.check_fields(
                        errs,
                        this,
                        other,
                        FieldContext::Fields,
                        t_fields.iter(),
                        o_fields.iter(),
                    );
                }
                (TLData::Union { .. }, _) => {}

                (TLData::Enum(t_enum), TLData::Enum(o_enum)) => {
                    self.check_enum(errs, this, other, t_enum, o_enum);
                    let t_as_ne = t_enum.exhaustiveness.as_nonexhaustive();
                    let o_as_ne = o_enum.exhaustiveness.as_nonexhaustive();
                    if let (Some(this_ne), Some(other_ne)) = (t_as_ne, o_as_ne) {
                        self.checked_nonexhaustive_enums
                            .push(CheckedNonExhaustiveEnums {
                                this: NonExhaustiveEnumWithContext {
                                    layout: this,
                                    enum_: t_enum,
                                    nonexhaustive: this_ne,
                                },
                                other: NonExhaustiveEnumWithContext {
                                    layout: other,
                                    enum_: o_enum,
                                    nonexhaustive: other_ne,
                                },
                            });
                    }
                }
                (TLData::Enum { .. }, _) => {}

                (TLData::PrefixType(t_prefix), TLData::PrefixType(o_prefix)) => {
                    let this_prefix = __PrefixTypeMetadata::with_prefix_layout(t_prefix, t_lay);
                    let other_prefix = __PrefixTypeMetadata::with_prefix_layout(o_prefix, o_lay);

                    self.check_prefix_types(errs, &this_prefix, &other_prefix);

                    self.checked_prefix_types.push(CheckedPrefixTypes {
                        this,
                        this_prefix,
                        other,
                        other_prefix,
                    })
                }
                (TLData::PrefixType { .. }, _) => {}
            }
        })();

        self.errors.extend(top_level_errs_);

        let check_st = self.visited.get_mut(&cuti_pair).unwrap();
        if errs_.is_empty()
            && self.errors.len() == start_errors
            && *check_st != CheckingState::Error
        {
            *check_st = CheckingState::Compatible;
            Ok(())
        } else {
            *check_st = CheckingState::Error;

            self.errors.push(AbiInstabilityError {
                stack_trace: self.stack_trace.clone(),
                errs: errs_,
                index: errs_index,
                _priv: (),
            });

            Err(())
        }
    }

    fn check_enum(
        &mut self,
        errs: &mut RVec<AbiInstability>,
        this: &'static TypeLayout,
        other: &'static TypeLayout,
        t_enum: TLEnum,
        o_enum: TLEnum,
    ) {
        let TLEnum {
            fields: t_fields, ..
        } = t_enum;
        let TLEnum {
            fields: o_fields, ..
        } = o_enum;

        let t_fcount = t_enum.field_count.as_slice();
        let o_fcount = o_enum.field_count.as_slice();

        let t_exhaus = t_enum.exhaustiveness;
        let o_exhaus = o_enum.exhaustiveness;

        match (t_exhaus.as_nonexhaustive(), o_exhaus.as_nonexhaustive()) {
            (Some(this_ne), Some(other_ne)) => {
                if let Err(e) = this_ne.check_compatible(this) {
                    errs.push(AI::IncompatibleWithNonExhaustive(e))
                }
                if let Err(e) = other_ne.check_compatible(other) {
                    errs.push(AI::IncompatibleWithNonExhaustive(e))
                }
            }
            (Some(_), None) | (None, Some(_)) => {
                push_err(
                    errs,
                    t_enum,
                    o_enum,
                    |x| x.exhaustiveness,
                    AI::MismatchedExhaustiveness,
                );
            }
            (None, None) => {}
        }

        if t_exhaus.is_exhaustive() && t_fcount.len() != o_fcount.len()
            || t_exhaus.is_nonexhaustive() && t_fcount.len() > o_fcount.len()
        {
            push_err(errs, t_fcount, o_fcount, |x| x.len(), AI::TooManyVariants);
        }

        if let Err(d_errs) = t_enum.discriminants.compare(&o_enum.discriminants) {
            errs.extend(d_errs);
        }

        let mut t_names = t_enum.variant_names.as_str().split(';');
        let mut o_names = o_enum.variant_names.as_str().split(';');
        let mut total_field_count = 0;
        for (t_field_count, o_field_count) in t_fcount.iter().zip(o_fcount) {
            let t_name = t_names.next().unwrap_or("<this unavailable>");
            let o_name = o_names.next().unwrap_or("<other unavailable>");

            total_field_count += usize::from(*t_field_count);

            if t_field_count != o_field_count {
                push_err(
                    errs,
                    *t_field_count,
                    *o_field_count,
                    |x| x as usize,
                    AI::FieldCountMismatch,
                );
            }

            if t_name != o_name {
                push_err(errs, t_name, o_name, RStr::from_str, AI::UnexpectedVariant);
                continue;
            }
        }

        let min_field_count = t_fields.len().min(o_fields.len());
        if total_field_count != min_field_count {
            push_err(
                errs,
                total_field_count,
                min_field_count,
                |x| x,
                AI::FieldCountMismatch,
            );
        }

        self.check_fields(
            errs,
            this,
            other,
            FieldContext::Fields,
            t_fields.iter(),
            o_fields.iter(),
        );
    }

    fn check_prefix_types(
        &mut self,
        errs: &mut RVec<AbiInstability>,
        this: &__PrefixTypeMetadata,
        other: &__PrefixTypeMetadata,
    ) {
        if this.prefix_field_count != other.prefix_field_count {
            push_err(
                errs,
                this,
                other,
                |x| x.prefix_field_count,
                AI::MismatchedPrefixSize,
            );
        }

        if this.conditional_prefix_fields != other.conditional_prefix_fields {
            push_err(
                errs,
                this,
                other,
                |x| x.conditional_prefix_fields,
                AI::MismatchedPrefixConditionality,
            );
        }

        self.check_fields(
            errs,
            this.layout,
            other.layout,
            FieldContext::Fields,
            this.fields.iter(),
            other.fields.iter(),
        );
    }

    /// Combines the prefix types into a global map of prefix types.
    fn final_prefix_type_checks(
        &mut self,
        globals: &CheckingGlobals,
    ) -> Result<(), AbiInstabilityError> {
        self.error_index += 1;
        let mut errs_ = RVec::<AbiInstability>::new();
        let errs = &mut errs_;

        let mut prefix_type_map = globals.prefix_type_map.lock().unwrap();

        for pair in mem::take(&mut self.checked_prefix_types) {
            // let t_lay=pair.this_prefix;
            let errors_before = self.errors.len();
            let t_utid = pair.this.get_utypeid();
            let o_utid = pair.other.get_utypeid();
            // let t_fields=pair.this_prefix.fields;
            // let o_fields=pair.other_prefix.fields;

            let t_index = prefix_type_map.get_index(&t_utid);
            let mut o_index = prefix_type_map.get_index(&o_utid);

            if t_index == o_index {
                o_index = None;
            }

            let (min_prefix, mut max_prefix) = pair.this_prefix.min_max(pair.other_prefix);

            match (t_index, o_index) {
                (None, None) => {
                    max_prefix.combine_fields_from(&min_prefix);

                    let i = prefix_type_map
                        .get_or_insert(t_utid, max_prefix)
                        .into_inner()
                        .index;
                    prefix_type_map.associate_key(o_utid, i);
                }
                (Some(im_index), None) | (None, Some(im_index)) => {
                    max_prefix.combine_fields_from(&min_prefix);

                    let im_prefix = prefix_type_map.get_mut_with_index(im_index).unwrap();
                    let im_prefix_addr = im_prefix as *const _ as usize;

                    let (min_prefix, max_prefix) =
                        min_max_by(im_prefix, &mut max_prefix, |x| x.fields.len());

                    self.check_prefix_types(errs, min_prefix, max_prefix);
                    if !errs.is_empty() || errors_before != self.errors.len() {
                        break;
                    }

                    max_prefix.combine_fields_from(&*min_prefix);

                    if im_prefix_addr != (max_prefix as *mut _ as usize) {
                        mem::swap(min_prefix, max_prefix);
                    }

                    prefix_type_map.associate_key(t_utid, im_index);
                    prefix_type_map.associate_key(o_utid, im_index);
                }
                (Some(l_index), Some(r_index)) => {
                    let (l_prefix, r_prefix) =
                        prefix_type_map.get2_mut_with_index(l_index, r_index);
                    let l_prefix = l_prefix.unwrap();
                    let r_prefix = r_prefix.unwrap();

                    let (replace, with) = if l_prefix.fields.len() < r_prefix.fields.len() {
                        (l_index, r_index)
                    } else {
                        (r_index, l_index)
                    };

                    let (min_prefix, max_prefix) =
                        min_max_by(l_prefix, r_prefix, |x| x.fields.len());
                    self.check_prefix_types(errs, min_prefix, max_prefix);
                    if !errs.is_empty() || errors_before != self.errors.len() {
                        break;
                    }

                    max_prefix.combine_fields_from(&*min_prefix);

                    prefix_type_map.replace_with_index(replace, with);
                }
            }
        }

        if errs_.is_empty() {
            Ok(())
        } else {
            Err(AbiInstabilityError {
                stack_trace: self.stack_trace.clone(),
                errs: errs_,
                index: self.error_index,
                _priv: (),
            })
        }
    }

    /// Combines the nonexhaustive enums into a global map of nonexhaustive enums.
    fn final_non_exhaustive_enum_checks(
        &mut self,
        globals: &CheckingGlobals,
    ) -> Result<(), AbiInstabilityError> {
        self.error_index += 1;
        let mut errs_ = RVec::<AbiInstability>::new();
        let errs = &mut errs_;

        let mut nonexhaustive_map = globals.nonexhaustive_map.lock().unwrap();

        for pair in mem::take(&mut self.checked_nonexhaustive_enums) {
            let CheckedNonExhaustiveEnums { this, other } = pair;
            let errors_before = self.errors.len();

            let t_utid = this.layout.get_utypeid();
            let o_utid = other.layout.get_utypeid();

            let t_index = nonexhaustive_map.get_index(&t_utid);
            let mut o_index = nonexhaustive_map.get_index(&o_utid);

            if t_index == o_index {
                o_index = None;
            }

            let mut max_ = max_by(this, other, |x| x.enum_.variant_count());

            match (t_index, o_index) {
                (None, None) => {
                    let i = nonexhaustive_map
                        .get_or_insert(t_utid, max_)
                        .into_inner()
                        .index;

                    nonexhaustive_map.associate_key(o_utid, i);
                }
                (Some(im_index), None) | (None, Some(im_index)) => {
                    let im_nonexh = nonexhaustive_map.get_mut_with_index(im_index).unwrap();
                    let im_nonexh_addr = im_nonexh as *const _ as usize;

                    let (min_nonexh, max_nonexh) =
                        min_max_by(im_nonexh, &mut max_, |x| x.enum_.variant_count());

                    self.check_enum(
                        errs,
                        min_nonexh.layout,
                        max_nonexh.layout,
                        min_nonexh.enum_,
                        max_nonexh.enum_,
                    );

                    if !errs.is_empty() || errors_before != self.errors.len() {
                        break;
                    }

                    if im_nonexh_addr != (max_nonexh as *mut _ as usize) {
                        mem::swap(min_nonexh, max_nonexh);
                    }

                    nonexhaustive_map.associate_key(t_utid, im_index);
                    nonexhaustive_map.associate_key(o_utid, im_index);
                }
                (Some(l_index), Some(r_index)) => {
                    let (l_nonexh, r_nonexh) =
                        nonexhaustive_map.get2_mut_with_index(l_index, r_index);
                    let l_nonexh = l_nonexh.unwrap();
                    let r_nonexh = r_nonexh.unwrap();

                    let (replace, with) =
                        if l_nonexh.enum_.variant_count() < r_nonexh.enum_.variant_count() {
                            (l_index, r_index)
                        } else {
                            (r_index, l_index)
                        };

                    let (min_nonexh, max_nonexh) =
                        min_max_by(l_nonexh, r_nonexh, |x| x.enum_.variant_count());

                    self.check_enum(
                        errs,
                        min_nonexh.layout,
                        max_nonexh.layout,
                        min_nonexh.enum_,
                        max_nonexh.enum_,
                    );

                    if !errs.is_empty() || errors_before != self.errors.len() {
                        break;
                    }

                    nonexhaustive_map.replace_with_index(replace, with);
                }
            }
        }

        if errs_.is_empty() {
            Ok(())
        } else {
            Err(AbiInstabilityError {
                stack_trace: self.stack_trace.clone(),
                errs: errs_,
                index: self.error_index,
                _priv: (),
            })
        }
    }

    /// Combines the ExtraChecksBox into a global map.
    fn final_extra_checks(
        &mut self,
        globals: &CheckingGlobals,
    ) -> Result<(), RVec<AbiInstabilityError>> {
        self.error_index += 1;

        let mut top_level_errs_ = RVec::<AbiInstabilityError>::new();

        let mut errs_ = RVec::<AbiInstability>::new();
        let errs = &mut errs_;
        let top_level_errs = &mut top_level_errs_;

        let mut extra_checker_map = globals.extra_checker_map.lock().unwrap();

        for with_context in mem::take(&mut self.checked_extra_checks) {
            let ExtraChecksBoxWithContext {
                t_lay,
                o_lay,
                extra_checks,
            } = with_context;

            let errors_before = self.errors.len();
            let type_checker = TypeCheckerMut::from_ptr(&mut *self, TD_Opaque);
            let t_utid = t_lay.get_utypeid();
            let o_utid = o_lay.get_utypeid();

            let t_index = extra_checker_map.get_index(&t_utid);
            let mut o_index = extra_checker_map.get_index(&o_utid);

            if t_index == o_index {
                o_index = None;
            }

            match (t_index, o_index) {
                (None, None) => {
                    let i = extra_checker_map
                        .get_or_insert(t_utid, extra_checks)
                        .into_inner()
                        .index;
                    extra_checker_map.associate_key(o_utid, i);
                }
                (Some(im_index), None) | (None, Some(im_index)) => {
                    let other_checks = extra_checker_map.get_mut_with_index(im_index).unwrap();

                    combine_extra_checks(
                        errs,
                        top_level_errs,
                        type_checker,
                        other_checks,
                        &[extra_checks.sabi_reborrow()],
                    );

                    if !errs.is_empty() || errors_before != self.errors.len() {
                        break;
                    }

                    extra_checker_map.associate_key(t_utid, im_index);
                    extra_checker_map.associate_key(o_utid, im_index);
                }
                (Some(l_index), Some(r_index)) => {
                    let (l_extra_checks, r_extra_checks) =
                        extra_checker_map.get2_mut_with_index(l_index, r_index);
                    let l_extra_checks = l_extra_checks.unwrap();
                    let r_extra_checks = r_extra_checks.unwrap();

                    combine_extra_checks(
                        errs,
                        top_level_errs,
                        type_checker,
                        l_extra_checks,
                        &[r_extra_checks.sabi_reborrow(), extra_checks.sabi_reborrow()],
                    );

                    if !errs.is_empty() || errors_before != self.errors.len() {
                        break;
                    }

                    extra_checker_map.replace_with_index(r_index, l_index);
                }
            }
        }

        if errs_.is_empty() {
            Ok(())
        } else {
            top_level_errs.push(AbiInstabilityError {
                stack_trace: self.stack_trace.clone(),
                errs: errs_,
                index: self.error_index,
                _priv: (),
            });
            Err(top_level_errs_)
        }
    }
}

/// Checks that the layout of `interface` is compatible with `implementation`.
///
/// # Warning
///
/// This function is not symmetric,
/// the first parameter must be the expected layout,
/// and the second must be actual layout.
///
pub fn check_layout_compatibility(
    interface: &'static TypeLayout,
    implementation: &'static TypeLayout,
) -> Result<(), AbiInstabilityErrors> {
    check_layout_compatibility_with_globals(interface, implementation, get_checking_globals())
}

#[inline(never)]
pub fn check_layout_compatibility_with_globals(
    interface: &'static TypeLayout,
    implementation: &'static TypeLayout,
    globals: &CheckingGlobals,
) -> Result<(), AbiInstabilityErrors> {
    let mut errors: RVec<AbiInstabilityError>;

    if interface.is_prefix_kind() || implementation.is_prefix_kind() {
        let mut errs = RVec::with_capacity(1);
        push_err(
            &mut errs,
            interface,
            implementation,
            |x| x.data_discriminant(),
            AI::TLDataDiscriminant,
        );
        errors = vec![AbiInstabilityError {
            stack_trace: vec![].into(),
            errs,
            index: 0,
            _priv: (),
        }]
        .into();
    } else {
        let mut checker = AbiChecker::new();
        let _ = checker.check_inner(interface, implementation);
        if checker.errors.is_empty() {
            if let Err(e) = checker.final_prefix_type_checks(globals) {
                checker.errors.push(e);
            }
            if let Err(e) = checker.final_non_exhaustive_enum_checks(globals) {
                checker.errors.push(e);
            }
            if let Err(e) = checker.final_extra_checks(globals) {
                checker.errors.extend(e);
            }
        }
        errors = checker.errors;
    }

    if errors.is_empty() {
        Ok(())
    } else {
        errors.sort_by_key(|x| x.index);
        Err(AbiInstabilityErrors {
            interface,
            implementation,
            errors,
            _priv: (),
        })
    }
}

/// Checks that the layout of `interface` is compatible with `implementation`,
pub(crate) extern "C" fn check_layout_compatibility_for_ffi(
    interface: &'static TypeLayout,
    implementation: &'static TypeLayout,
) -> RResult<(), RBoxError> {
    extern_fn_panic_handling! {
        let mut is_already_inside=false;
        INSIDE_LAYOUT_CHECKER.with(|inside|{
            is_already_inside=inside.get();
            inside.set(true);
        });
        let _guard=LayoutCheckerGuard;

        if is_already_inside {
            let errors =
                vec![AbiInstabilityError {
                    stack_trace: vec![].into(),
                    errs:vec![AbiInstability::ReentrantLayoutCheckingCall].into(),
                    index: 0,
                    _priv:(),
                }].into_c();

            Err(AbiInstabilityErrors{ interface, implementation, errors, _priv:() })
        }else{
            check_layout_compatibility(interface,implementation)
        }.map_err(RBoxError::new)
         .into_c()
    }
}

/// Checks that the layout of `interface` is compatible with `implementation`,
///
/// If this function is called within a dynamic library,
/// it must be called during or after the function that exports its root module is called.
///
/// **DO NOT** call this in the static initializer of a dynamic library,
/// since this library relies on setting up its global state before
/// calling the root module loader.
///
/// # Warning
///
/// This function is not symmetric,
/// the first parameter must be the expected layout,
/// and the second must be actual layout.
///
///
pub extern "C" fn exported_check_layout_compatibility(
    interface: &'static TypeLayout,
    implementation: &'static TypeLayout,
) -> RResult<(), RBoxError> {
    extern_fn_panic_handling! {
        (crate::globals::initialized_globals().layout_checking)
            (interface,implementation)
    }
}

impl AbiChecker {
    fn check_compatibility_inner(
        &mut self,
        interface: &'static TypeLayout,
        implementation: &'static TypeLayout,
    ) -> RResult<(), ()> {
        let error_count_before = self.errors.len();

        self.current_layer += 1;

        let res = self.check_inner(interface, implementation);

        self.current_layer -= 1;

        if error_count_before == self.errors.len() && res.is_ok() {
            ROk(())
        } else {
            RErr(())
        }
    }
}

unsafe impl TypeChecker for AbiChecker {
    fn check_compatibility(
        &mut self,
        interface: &'static TypeLayout,
        implementation: &'static TypeLayout,
    ) -> RResult<(), ExtraChecksError> {
        self.check_compatibility_inner(interface, implementation)
            .map_err(|_| ExtraChecksError::TypeChecker)
    }

    fn local_check_compatibility(
        &mut self,
        interface: &'static TypeLayout,
        implementation: &'static TypeLayout,
    ) -> RResult<(), ExtraChecksError> {
        let error_count_before = self.errors.len();

        dbg!(error_count_before);
        println!(
            "interface:{} implementation:{}",
            interface.full_type(),
            implementation.full_type()
        );

        self.check_compatibility_inner(interface, implementation)
            .map_err(|_| {
                AbiInstabilityErrors {
                    interface,
                    implementation,
                    errors: self.errors.drain(error_count_before..).collect(),
                    _priv: (),
                }
                .piped(RBoxError::new)
                .piped(ExtraChecksError::TypeCheckerErrors)
            })
    }
}

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

thread_local! {
    static INSIDE_LAYOUT_CHECKER:Cell<bool>=Cell::new(false);
}

struct LayoutCheckerGuard;

impl Drop for LayoutCheckerGuard {
    fn drop(&mut self) {
        INSIDE_LAYOUT_CHECKER.with(|inside| {
            inside.set(false);
        });
    }
}

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

use std::sync::Mutex;

use crate::{
    multikey_map::MultiKeyMap, prefix_type::__PrefixTypeMetadata, sabi_types::LateStaticRef,
    utils::leak_value,
};

#[derive(Debug)]
pub struct CheckingGlobals {
    pub prefix_type_map: Mutex<MultiKeyMap<UTypeId, __PrefixTypeMetadata>>,
    pub nonexhaustive_map: Mutex<MultiKeyMap<UTypeId, NonExhaustiveEnumWithContext>>,
    pub extra_checker_map: Mutex<MultiKeyMap<UTypeId, ExtraChecksBox>>,
}

#[allow(clippy::new_without_default)]
impl CheckingGlobals {
    pub fn new() -> Self {
        CheckingGlobals {
            prefix_type_map: MultiKeyMap::new().piped(Mutex::new),
            nonexhaustive_map: MultiKeyMap::new().piped(Mutex::new),
            extra_checker_map: MultiKeyMap::new().piped(Mutex::new),
        }
    }
}

static CHECKING_GLOBALS: LateStaticRef<&CheckingGlobals> = LateStaticRef::new();

pub fn get_checking_globals() -> &'static CheckingGlobals {
    CHECKING_GLOBALS.init(|| CheckingGlobals::new().piped(leak_value))
}

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

pub(crate) fn push_err<O, U, FG, VC>(
    errs: &mut RVec<AbiInstability>,
    this: O,
    other: O,
    field_getter: FG,
    mut variant_constructor: VC,
) where
    FG: FnMut(O) -> U,
    VC: FnMut(ExpectedFound<U>) -> AbiInstability,
{
    let x = ExpectedFound::new(this, other, field_getter);
    let x = variant_constructor(x);
    errs.push(x);
}

fn handle_extra_checks_ret<F, R>(
    expected_extra_checks: ExtraChecksRef<'_>,
    found_extra_checks: ExtraChecksRef<'_>,
    errs: &mut RVec<AbiInstability>,
    top_level_errs: &mut RVec<AbiInstabilityError>,
    f: F,
) -> Result<R, ()>
where
    F: FnOnce() -> RResult<R, ExtraChecksError>,
{
    let make_extra_check_error = move |e: RBoxError| -> AbiInstability {
        ExtraCheckError {
            err: RArc::new(e),
            expected_err: ExpectedFound {
                expected: expected_extra_checks
                    .piped_ref(RBoxError::from_fmt)
                    .piped(RArc::new),

                found: found_extra_checks
                    .piped_ref(RBoxError::from_fmt)
                    .piped(RArc::new),
            },
        }
        .piped(CmpIgnored::new)
        .piped(AI::ExtraCheckError)
    };
    match f() {
        ROk(x) => Ok(x),
        RErr(ExtraChecksError::TypeChecker) => Err(()),
        RErr(ExtraChecksError::TypeCheckerErrors(e)) => {
            match e.downcast::<AbiInstabilityErrors>() {
                Ok(e) => top_level_errs.extend(RBox::into_inner(e).errors),
                Err(e) => errs.push(make_extra_check_error(e)),
            }
            Err(())
        }
        RErr(ExtraChecksError::NoneExtraChecks) => {
            errs.push(AI::NoneExtraChecks);
            Err(())
        }
        RErr(ExtraChecksError::ExtraChecks(e)) => {
            errs.push(make_extra_check_error(e));
            Err(())
        }
    }
}

fn combine_extra_checks(
    errs: &mut RVec<AbiInstability>,
    top_level_errs: &mut RVec<AbiInstabilityError>,
    mut ty_checker: TypeCheckerMut<'_>,
    extra_checks: &mut ExtraChecksBox,
    slic: &[ExtraChecksRef<'_>],
) {
    for other in slic {
        let other_ref = other.sabi_reborrow();
        let ty_checker = ty_checker.sabi_reborrow_mut();
        let opt_ret = handle_extra_checks_ret(
            extra_checks.sabi_reborrow(),
            other.sabi_reborrow(),
            errs,
            top_level_errs,
            || extra_checks.sabi_reborrow().combine(other_ref, ty_checker),
        );

        match opt_ret {
            Ok(RSome(new)) => {
                *extra_checks = new;
            }
            Ok(RNone) => {}
            Err(_) => break,
        }
    }
}