use rustc_middle::ty::{TyKind, TypeAndMut};
use rustc_target::abi::{LayoutOf, Size};

use crate::stacked_borrows::Tag;
use crate::*;

fn assert_ptr_target_min_size<'mir, 'tcx: 'mir>(
    ecx: &MiriEvalContext<'mir, 'tcx>,
    operand: OpTy<'tcx, Tag>,
    min_size: u64,
) -> InterpResult<'tcx, ()> {
    let target_ty = match operand.layout.ty.kind {
        TyKind::RawPtr(TypeAndMut { ty, mutbl: _ }) => ty,
        _ => panic!("Argument to pthread function was not a raw pointer"),
    };
    let target_layout = ecx.layout_of(target_ty)?;
    assert!(target_layout.size.bytes() >= min_size);
    Ok(())
}

// pthread_mutexattr_t is either 4 or 8 bytes, depending on the platform.

// Our chosen memory layout for emulation (does not have to match the platform layout!):
// store an i32 in the first four bytes equal to the corresponding libc mutex kind constant
// (e.g. PTHREAD_MUTEX_NORMAL).

fn mutexattr_get_kind<'mir, 'tcx: 'mir>(
    ecx: &MiriEvalContext<'mir, 'tcx>,
    attr_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
    // Ensure that the following read at an offset to the attr pointer is within bounds
    assert_ptr_target_min_size(ecx, attr_op, 4)?;
    let attr_place = ecx.deref_operand(attr_op)?;
    let kind_place = attr_place.offset(Size::ZERO, MemPlaceMeta::None, ecx.i32_layout()?, ecx)?;
    ecx.read_scalar(kind_place.into())
}

fn mutexattr_set_kind<'mir, 'tcx: 'mir>(
    ecx: &mut MiriEvalContext<'mir, 'tcx>,
    attr_op: OpTy<'tcx, Tag>,
    kind: impl Into<ScalarMaybeUndef<Tag>>,
) -> InterpResult<'tcx, ()> {
    // Ensure that the following write at an offset to the attr pointer is within bounds
    assert_ptr_target_min_size(ecx, attr_op, 4)?;
    let attr_place = ecx.deref_operand(attr_op)?;
    let kind_place = attr_place.offset(Size::ZERO, MemPlaceMeta::None, ecx.i32_layout()?, ecx)?;
    ecx.write_scalar(kind.into(), kind_place.into())
}

// pthread_mutex_t is between 24 and 48 bytes, depending on the platform.

// Our chosen memory layout for the emulated mutex (does not have to match the platform layout!):
// bytes 0-3: reserved for signature on macOS
// (need to avoid this because it is set by static initializer macros)
// bytes 4-7: count of how many times this mutex has been locked, as a u32
// bytes 12-15 or 16-19 (depending on platform): mutex kind, as an i32
// (the kind has to be at its offset for compatibility with static initializer macros)

fn mutex_get_locked_count<'mir, 'tcx: 'mir>(
    ecx: &MiriEvalContext<'mir, 'tcx>,
    mutex_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
    // Ensure that the following read at an offset to the mutex pointer is within bounds
    assert_ptr_target_min_size(ecx, mutex_op, 20)?;
    let mutex_place = ecx.deref_operand(mutex_op)?;
    let locked_count_place =
        mutex_place.offset(Size::from_bytes(4), MemPlaceMeta::None, ecx.u32_layout()?, ecx)?;
    ecx.read_scalar(locked_count_place.into())
}

fn mutex_set_locked_count<'mir, 'tcx: 'mir>(
    ecx: &mut MiriEvalContext<'mir, 'tcx>,
    mutex_op: OpTy<'tcx, Tag>,
    locked_count: impl Into<ScalarMaybeUndef<Tag>>,
) -> InterpResult<'tcx, ()> {
    // Ensure that the following write at an offset to the mutex pointer is within bounds
    assert_ptr_target_min_size(ecx, mutex_op, 20)?;
    let mutex_place = ecx.deref_operand(mutex_op)?;
    let locked_count_place =
        mutex_place.offset(Size::from_bytes(4), MemPlaceMeta::None, ecx.u32_layout()?, ecx)?;
    ecx.write_scalar(locked_count.into(), locked_count_place.into())
}

fn mutex_get_kind<'mir, 'tcx: 'mir>(
    ecx: &mut MiriEvalContext<'mir, 'tcx>,
    mutex_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
    // Ensure that the following read at an offset to the mutex pointer is within bounds
    assert_ptr_target_min_size(ecx, mutex_op, 20)?;
    let mutex_place = ecx.deref_operand(mutex_op)?;
    let kind_offset = if ecx.pointer_size().bytes() == 8 { 16 } else { 12 };
    let kind_place = mutex_place.offset(
        Size::from_bytes(kind_offset),
        MemPlaceMeta::None,
        ecx.i32_layout()?,
        ecx,
    )?;
    ecx.read_scalar(kind_place.into())
}

fn mutex_set_kind<'mir, 'tcx: 'mir>(
    ecx: &mut MiriEvalContext<'mir, 'tcx>,
    mutex_op: OpTy<'tcx, Tag>,
    kind: impl Into<ScalarMaybeUndef<Tag>>,
) -> InterpResult<'tcx, ()> {
    // Ensure that the following write at an offset to the mutex pointer is within bounds
    assert_ptr_target_min_size(ecx, mutex_op, 20)?;
    let mutex_place = ecx.deref_operand(mutex_op)?;
    let kind_offset = if ecx.pointer_size().bytes() == 8 { 16 } else { 12 };
    let kind_place = mutex_place.offset(
        Size::from_bytes(kind_offset),
        MemPlaceMeta::None,
        ecx.i32_layout()?,
        ecx,
    )?;
    ecx.write_scalar(kind.into(), kind_place.into())
}

// pthread_rwlock_t is between 32 and 56 bytes, depending on the platform.

// Our chosen memory layout for the emulated rwlock (does not have to match the platform layout!):
// bytes 0-3: reserved for signature on macOS
// (need to avoid this because it is set by static initializer macros)
// bytes 4-7: reader count, as a u32
// bytes 8-11: writer count, as a u32

fn rwlock_get_readers<'mir, 'tcx: 'mir>(
    ecx: &MiriEvalContext<'mir, 'tcx>,
    rwlock_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
    // Ensure that the following read at an offset to the rwlock pointer is within bounds
    assert_ptr_target_min_size(ecx, rwlock_op, 12)?;
    let rwlock_place = ecx.deref_operand(rwlock_op)?;
    let readers_place =
        rwlock_place.offset(Size::from_bytes(4), MemPlaceMeta::None, ecx.u32_layout()?, ecx)?;
    ecx.read_scalar(readers_place.into())
}

fn rwlock_set_readers<'mir, 'tcx: 'mir>(
    ecx: &mut MiriEvalContext<'mir, 'tcx>,
    rwlock_op: OpTy<'tcx, Tag>,
    readers: impl Into<ScalarMaybeUndef<Tag>>,
) -> InterpResult<'tcx, ()> {
    // Ensure that the following write at an offset to the rwlock pointer is within bounds
    assert_ptr_target_min_size(ecx, rwlock_op, 12)?;
    let rwlock_place = ecx.deref_operand(rwlock_op)?;
    let readers_place =
        rwlock_place.offset(Size::from_bytes(4), MemPlaceMeta::None, ecx.u32_layout()?, ecx)?;
    ecx.write_scalar(readers.into(), readers_place.into())
}

fn rwlock_get_writers<'mir, 'tcx: 'mir>(
    ecx: &MiriEvalContext<'mir, 'tcx>,
    rwlock_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
    // Ensure that the following read at an offset to the rwlock pointer is within bounds
    assert_ptr_target_min_size(ecx, rwlock_op, 12)?;
    let rwlock_place = ecx.deref_operand(rwlock_op)?;
    let writers_place =
        rwlock_place.offset(Size::from_bytes(8), MemPlaceMeta::None, ecx.u32_layout()?, ecx)?;
    ecx.read_scalar(writers_place.into())
}

fn rwlock_set_writers<'mir, 'tcx: 'mir>(
    ecx: &mut MiriEvalContext<'mir, 'tcx>,
    rwlock_op: OpTy<'tcx, Tag>,
    writers: impl Into<ScalarMaybeUndef<Tag>>,
) -> InterpResult<'tcx, ()> {
    // Ensure that the following write at an offset to the rwlock pointer is within bounds
    assert_ptr_target_min_size(ecx, rwlock_op, 12)?;
    let rwlock_place = ecx.deref_operand(rwlock_op)?;
    let writers_place =
        rwlock_place.offset(Size::from_bytes(8), MemPlaceMeta::None, ecx.u32_layout()?, ecx)?;
    ecx.write_scalar(writers.into(), writers_place.into())
}

impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
    fn pthread_mutexattr_init(&mut self, attr_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let default_kind = this.eval_libc("PTHREAD_MUTEX_DEFAULT")?;
        mutexattr_set_kind(this, attr_op, default_kind)?;

        Ok(0)
    }

    fn pthread_mutexattr_settype(
        &mut self,
        attr_op: OpTy<'tcx, Tag>,
        kind_op: OpTy<'tcx, Tag>,
    ) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let kind = this.read_scalar(kind_op)?.not_undef()?;
        if kind == this.eval_libc("PTHREAD_MUTEX_NORMAL")?
            || kind == this.eval_libc("PTHREAD_MUTEX_ERRORCHECK")?
            || kind == this.eval_libc("PTHREAD_MUTEX_RECURSIVE")?
        {
            mutexattr_set_kind(this, attr_op, kind)?;
        } else {
            let einval = this.eval_libc_i32("EINVAL")?;
            return Ok(einval);
        }

        Ok(0)
    }

    fn pthread_mutexattr_destroy(&mut self, attr_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        mutexattr_set_kind(this, attr_op, ScalarMaybeUndef::Undef)?;

        Ok(0)
    }

    fn pthread_mutex_init(
        &mut self,
        mutex_op: OpTy<'tcx, Tag>,
        attr_op: OpTy<'tcx, Tag>,
    ) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let attr = this.read_scalar(attr_op)?.not_undef()?;
        let kind = if this.is_null(attr)? {
            this.eval_libc("PTHREAD_MUTEX_DEFAULT")?
        } else {
            mutexattr_get_kind(this, attr_op)?.not_undef()?
        };

        mutex_set_locked_count(this, mutex_op, Scalar::from_u32(0))?;
        mutex_set_kind(this, mutex_op, kind)?;

        Ok(0)
    }

    fn pthread_mutex_lock(&mut self, mutex_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let kind = mutex_get_kind(this, mutex_op)?.not_undef()?;
        let locked_count = mutex_get_locked_count(this, mutex_op)?.to_u32()?;

        if kind == this.eval_libc("PTHREAD_MUTEX_NORMAL")? {
            if locked_count == 0 {
                mutex_set_locked_count(this, mutex_op, Scalar::from_u32(1))?;
                Ok(0)
            } else {
                throw_machine_stop!(TerminationInfo::Deadlock);
            }
        } else if kind == this.eval_libc("PTHREAD_MUTEX_ERRORCHECK")? {
            if locked_count == 0 {
                mutex_set_locked_count(this, mutex_op, Scalar::from_u32(1))?;
                Ok(0)
            } else {
                this.eval_libc_i32("EDEADLK")
            }
        } else if kind == this.eval_libc("PTHREAD_MUTEX_RECURSIVE")? {
            match locked_count.checked_add(1) {
                Some(new_count) => {
                    mutex_set_locked_count(this, mutex_op, Scalar::from_u32(new_count))?;
                    Ok(0)
                }
                None => this.eval_libc_i32("EAGAIN"),
            }
        } else {
            throw_ub_format!("called pthread_mutex_lock on an unsupported type of mutex");
        }
    }

    fn pthread_mutex_trylock(&mut self, mutex_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let kind = mutex_get_kind(this, mutex_op)?.not_undef()?;
        let locked_count = mutex_get_locked_count(this, mutex_op)?.to_u32()?;

        if kind == this.eval_libc("PTHREAD_MUTEX_NORMAL")?
            || kind == this.eval_libc("PTHREAD_MUTEX_ERRORCHECK")?
        {
            if locked_count == 0 {
                mutex_set_locked_count(this, mutex_op, Scalar::from_u32(1))?;
                Ok(0)
            } else {
                this.eval_libc_i32("EBUSY")
            }
        } else if kind == this.eval_libc("PTHREAD_MUTEX_RECURSIVE")? {
            match locked_count.checked_add(1) {
                Some(new_count) => {
                    mutex_set_locked_count(this, mutex_op, Scalar::from_u32(new_count))?;
                    Ok(0)
                }
                None => this.eval_libc_i32("EAGAIN"),
            }
        } else {
            throw_ub_format!("called pthread_mutex_trylock on an unsupported type of mutex");
        }
    }

    fn pthread_mutex_unlock(&mut self, mutex_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let kind = mutex_get_kind(this, mutex_op)?.not_undef()?;
        let locked_count = mutex_get_locked_count(this, mutex_op)?.to_u32()?;

        if kind == this.eval_libc("PTHREAD_MUTEX_NORMAL")? {
            if locked_count != 0 {
                mutex_set_locked_count(this, mutex_op, Scalar::from_u32(0))?;
                Ok(0)
            } else {
                throw_ub_format!("unlocked a PTHREAD_MUTEX_NORMAL mutex that was not locked");
            }
        } else if kind == this.eval_libc("PTHREAD_MUTEX_ERRORCHECK")? {
            if locked_count != 0 {
                mutex_set_locked_count(this, mutex_op, Scalar::from_u32(0))?;
                Ok(0)
            } else {
                this.eval_libc_i32("EPERM")
            }
        } else if kind == this.eval_libc("PTHREAD_MUTEX_RECURSIVE")? {
            match locked_count.checked_sub(1) {
                Some(new_count) => {
                    mutex_set_locked_count(this, mutex_op, Scalar::from_u32(new_count))?;
                    Ok(0)
                }
                None => {
                    // locked_count was already zero
                    this.eval_libc_i32("EPERM")
                }
            }
        } else {
            throw_ub_format!("called pthread_mutex_unlock on an unsupported type of mutex");
        }
    }

    fn pthread_mutex_destroy(&mut self, mutex_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        if mutex_get_locked_count(this, mutex_op)?.to_u32()? != 0 {
            throw_ub_format!("destroyed a locked mutex");
        }

        mutex_set_kind(this, mutex_op, ScalarMaybeUndef::Undef)?;
        mutex_set_locked_count(this, mutex_op, ScalarMaybeUndef::Undef)?;

        Ok(0)
    }

    fn pthread_rwlock_rdlock(&mut self, rwlock_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
        let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
        if writers != 0 {
            throw_machine_stop!(TerminationInfo::Deadlock);
        } else {
            match readers.checked_add(1) {
                Some(new_readers) => {
                    rwlock_set_readers(this, rwlock_op, Scalar::from_u32(new_readers))?;
                    Ok(0)
                }
                None => this.eval_libc_i32("EAGAIN"),
            }
        }
    }

    fn pthread_rwlock_tryrdlock(&mut self, rwlock_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
        let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
        if writers != 0 {
            this.eval_libc_i32("EBUSY")
        } else {
            match readers.checked_add(1) {
                Some(new_readers) => {
                    rwlock_set_readers(this, rwlock_op, Scalar::from_u32(new_readers))?;
                    Ok(0)
                }
                None => this.eval_libc_i32("EAGAIN"),
            }
        }
    }

    fn pthread_rwlock_wrlock(&mut self, rwlock_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
        let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
        if readers != 0 {
            throw_machine_stop!(TerminationInfo::Deadlock);
        } else if writers != 0 {
            throw_machine_stop!(TerminationInfo::Deadlock);
        } else {
            rwlock_set_writers(this, rwlock_op, Scalar::from_u32(1))?;
            Ok(0)
        }
    }

    fn pthread_rwlock_trywrlock(&mut self, rwlock_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
        let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
        if readers != 0 || writers != 0 {
            this.eval_libc_i32("EBUSY")
        } else {
            rwlock_set_writers(this, rwlock_op, Scalar::from_u32(1))?;
            Ok(0)
        }
    }

    fn pthread_rwlock_unlock(&mut self, rwlock_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        let readers = rwlock_get_readers(this, rwlock_op)?.to_u32()?;
        let writers = rwlock_get_writers(this, rwlock_op)?.to_u32()?;
        if let Some(new_readers) = readers.checked_sub(1) {
            rwlock_set_readers(this, rwlock_op, Scalar::from_u32(new_readers))?;
            Ok(0)
        } else if writers != 0 {
            rwlock_set_writers(this, rwlock_op, Scalar::from_u32(0))?;
            Ok(0)
        } else {
            throw_ub_format!("unlocked an rwlock that was not locked");
        }
    }

    fn pthread_rwlock_destroy(&mut self, rwlock_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
        let this = self.eval_context_mut();

        if rwlock_get_readers(this, rwlock_op)?.to_u32()? != 0
            || rwlock_get_writers(this, rwlock_op)?.to_u32()? != 0
        {
            throw_ub_format!("destroyed a locked rwlock");
        }

        rwlock_set_readers(this, rwlock_op, ScalarMaybeUndef::Undef)?;
        rwlock_set_writers(this, rwlock_op, ScalarMaybeUndef::Undef)?;

        Ok(0)
    }
}