use std::iter;

use rustc::mir;
use rustc::mir::interpret::{InterpResult, PointerArithmetic};
use rustc::ty;
use rustc::ty::layout::{self, Align, LayoutOf, Size};
use rustc_apfloat::Float;
use syntax::source_map::Span;

use crate::*;

impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
    fn call_intrinsic(
        &mut self,
        span: Span,
        instance: ty::Instance<'tcx>,
        args: &[OpTy<'tcx, Tag>],
        ret: Option<(PlaceTy<'tcx, Tag>, mir::BasicBlock)>,
        unwind: Option<mir::BasicBlock>,
    ) -> InterpResult<'tcx> {
        let this = self.eval_context_mut();
        if this.emulate_intrinsic(span, instance, args, ret)? {
            return Ok(());
        }
        let tcx = &{ this.tcx.tcx };
        let substs = instance.substs;

        // All these intrinsics take raw pointers, so if we access memory directly
        // (as opposed to through a place), we have to remember to erase any tag
        // that might still hang around!
        let intrinsic_name = &*tcx.item_name(instance.def_id()).as_str();

        // Handle diverging intrinsics.
        let (dest, ret) = match intrinsic_name {
            "abort" => {
                throw_machine_stop!(TerminationInfo::Abort);
            }
            "miri_start_panic" => return this.handle_miri_start_panic(args, unwind),
            _ =>
                if let Some(p) = ret {
                    p
                } else {
                    throw_unsup_format!("unimplemented (diverging) intrinsic: {}", intrinsic_name);
                },
        };

        match intrinsic_name {
            "arith_offset" => {
                let offset = this.read_scalar(args[1])?.to_machine_isize(this)?;
                let ptr = this.read_scalar(args[0])?.not_undef()?;

                let pointee_ty = substs.type_at(0);
                let pointee_size = this.layout_of(pointee_ty)?.size.bytes() as i64;
                let offset = offset.overflowing_mul(pointee_size).0;
                let result_ptr = ptr.ptr_wrapping_signed_offset(offset, this);
                this.write_scalar(result_ptr, dest)?;
            }

            "assume" => {
                let cond = this.read_scalar(args[0])?.to_bool()?;
                if !cond {
                    throw_ub_format!("`assume` intrinsic called with `false`");
                }
            }

            "volatile_load" => {
                let place = this.deref_operand(args[0])?;
                this.copy_op(place.into(), dest)?;
            }

            "volatile_store" => {
                let place = this.deref_operand(args[0])?;
                this.copy_op(args[1], place.into())?;
            }

            #[rustfmt::skip]
            | "atomic_load"
            | "atomic_load_relaxed"
            | "atomic_load_acq"
            => {
                let place = this.deref_operand(args[0])?;
                let val = this.read_scalar(place.into())?; // make sure it fits into a scalar; otherwise it cannot be atomic

                // Check alignment requirements. Atomics must always be aligned to their size,
                // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
                // be 8-aligned).
                let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
                this.memory.check_ptr_access(place.ptr, place.layout.size, align)?;

                this.write_scalar(val, dest)?;
            }

            #[rustfmt::skip]
            | "atomic_store"
            | "atomic_store_relaxed"
            | "atomic_store_rel"
            => {
                let place = this.deref_operand(args[0])?;
                let val = this.read_scalar(args[1])?; // make sure it fits into a scalar; otherwise it cannot be atomic

                // Check alignment requirements. Atomics must always be aligned to their size,
                // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
                // be 8-aligned).
                let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
                this.memory.check_ptr_access(place.ptr, place.layout.size, align)?;

                this.write_scalar(val, place.into())?;
            }

            #[rustfmt::skip]
            | "atomic_fence_acq"
            | "atomic_fence_rel"
            | "atomic_fence_acqrel"
            | "atomic_fence"
            => {
                // we are inherently singlethreaded and singlecored, this is a nop
            }

            _ if intrinsic_name.starts_with("atomic_xchg") => {
                let place = this.deref_operand(args[0])?;
                let new = this.read_scalar(args[1])?;
                let old = this.read_scalar(place.into())?;

                // Check alignment requirements. Atomics must always be aligned to their size,
                // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
                // be 8-aligned).
                let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
                this.memory.check_ptr_access(place.ptr, place.layout.size, align)?;

                this.write_scalar(old, dest)?; // old value is returned
                this.write_scalar(new, place.into())?;
            }

            _ if intrinsic_name.starts_with("atomic_cxchg") => {
                let place = this.deref_operand(args[0])?;
                let expect_old = this.read_immediate(args[1])?; // read as immediate for the sake of `binary_op()`
                let new = this.read_scalar(args[2])?;
                let old = this.read_immediate(place.into())?; // read as immediate for the sake of `binary_op()`

                // Check alignment requirements. Atomics must always be aligned to their size,
                // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
                // be 8-aligned).
                let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
                this.memory.check_ptr_access(place.ptr, place.layout.size, align)?;

                // `binary_op` will bail if either of them is not a scalar.
                let eq = this.overflowing_binary_op(mir::BinOp::Eq, old, expect_old)?.0;
                let res = Immediate::ScalarPair(old.to_scalar_or_undef(), eq.into());
                // Return old value.
                this.write_immediate(res, dest)?;
                // Update ptr depending on comparison.
                if eq.to_bool()? {
                    this.write_scalar(new, place.into())?;
                }
            }

            #[rustfmt::skip]
            | "atomic_or"
            | "atomic_or_acq"
            | "atomic_or_rel"
            | "atomic_or_acqrel"
            | "atomic_or_relaxed"
            | "atomic_xor"
            | "atomic_xor_acq"
            | "atomic_xor_rel"
            | "atomic_xor_acqrel"
            | "atomic_xor_relaxed"
            | "atomic_and"
            | "atomic_and_acq"
            | "atomic_and_rel"
            | "atomic_and_acqrel"
            | "atomic_and_relaxed"
            | "atomic_nand"
            | "atomic_nand_acq"
            | "atomic_nand_rel"
            | "atomic_nand_acqrel"
            | "atomic_nand_relaxed"
            | "atomic_xadd"
            | "atomic_xadd_acq"
            | "atomic_xadd_rel"
            | "atomic_xadd_acqrel"
            | "atomic_xadd_relaxed"
            | "atomic_xsub"
            | "atomic_xsub_acq"
            | "atomic_xsub_rel"
            | "atomic_xsub_acqrel"
            | "atomic_xsub_relaxed"
            => {
                let place = this.deref_operand(args[0])?;
                if !place.layout.ty.is_integral() {
                    bug!("Atomic arithmetic operations only work on integer types");
                }
                let rhs = this.read_immediate(args[1])?;
                let old = this.read_immediate(place.into())?;

                // Check alignment requirements. Atomics must always be aligned to their size,
                // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
                // be 8-aligned).
                let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
                this.memory.check_ptr_access(place.ptr, place.layout.size, align)?;

                this.write_immediate(*old, dest)?; // old value is returned
                let (op, neg) = match intrinsic_name.split('_').nth(1).unwrap() {
                    "or" => (mir::BinOp::BitOr, false),
                    "xor" => (mir::BinOp::BitXor, false),
                    "and" => (mir::BinOp::BitAnd, false),
                    "xadd" => (mir::BinOp::Add, false),
                    "xsub" => (mir::BinOp::Sub, false),
                    "nand" => (mir::BinOp::BitAnd, true),
                    _ => bug!(),
                };
                // Atomics wrap around on overflow.
                let val = this.binary_op(op, old, rhs)?;
                let val = if neg { this.unary_op(mir::UnOp::Not, val)? } else { val };
                this.write_immediate(*val, place.into())?;
            }

            "breakpoint" => unimplemented!(), // halt miri

            #[rustfmt::skip]
            | "copy"
            | "copy_nonoverlapping"
            => {
                let elem_ty = substs.type_at(0);
                let elem_layout = this.layout_of(elem_ty)?;
                let elem_size = elem_layout.size.bytes();
                let count = this.read_scalar(args[2])?.to_machine_usize(this)?;
                let elem_align = elem_layout.align.abi;

                let size = Size::from_bytes(count * elem_size);
                let src = this.read_scalar(args[0])?.not_undef()?;
                let src = this.memory.check_ptr_access(src, size, elem_align)?;
                let dest = this.read_scalar(args[1])?.not_undef()?;
                let dest = this.memory.check_ptr_access(dest, size, elem_align)?;

                if let (Some(src), Some(dest)) = (src, dest) {
                    this.memory.copy(
                        src,
                        dest,
                        size,
                        intrinsic_name.ends_with("_nonoverlapping"),
                    )?;
                }
            }

            "discriminant_value" => {
                let place = this.deref_operand(args[0])?;
                let discr_val = this.read_discriminant(place.into())?.0;
                this.write_scalar(Scalar::from_uint(discr_val, dest.layout.size), dest)?;
            }

            #[rustfmt::skip]
            | "sinf32"
            | "fabsf32"
            | "cosf32"
            | "sqrtf32"
            | "expf32"
            | "exp2f32"
            | "logf32"
            | "log10f32"
            | "log2f32"
            | "floorf32"
            | "ceilf32"
            | "truncf32"
            | "roundf32"
            => {
                // FIXME: Using host floats.
                let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
                let f = match intrinsic_name {
                    "sinf32" => f.sin(),
                    "fabsf32" => f.abs(),
                    "cosf32" => f.cos(),
                    "sqrtf32" => f.sqrt(),
                    "expf32" => f.exp(),
                    "exp2f32" => f.exp2(),
                    "logf32" => f.ln(),
                    "log10f32" => f.log10(),
                    "log2f32" => f.log2(),
                    "floorf32" => f.floor(),
                    "ceilf32" => f.ceil(),
                    "truncf32" => f.trunc(),
                    "roundf32" => f.round(),
                    _ => bug!(),
                };
                this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
            }

            #[rustfmt::skip]
            | "sinf64"
            | "fabsf64"
            | "cosf64"
            | "sqrtf64"
            | "expf64"
            | "exp2f64"
            | "logf64"
            | "log10f64"
            | "log2f64"
            | "floorf64"
            | "ceilf64"
            | "truncf64"
            | "roundf64"
            => {
                // FIXME: Using host floats.
                let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
                let f = match intrinsic_name {
                    "sinf64" => f.sin(),
                    "fabsf64" => f.abs(),
                    "cosf64" => f.cos(),
                    "sqrtf64" => f.sqrt(),
                    "expf64" => f.exp(),
                    "exp2f64" => f.exp2(),
                    "logf64" => f.ln(),
                    "log10f64" => f.log10(),
                    "log2f64" => f.log2(),
                    "floorf64" => f.floor(),
                    "ceilf64" => f.ceil(),
                    "truncf64" => f.trunc(),
                    "roundf64" => f.round(),
                    _ => bug!(),
                };
                this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
            }

            #[rustfmt::skip]
            | "fadd_fast"
            | "fsub_fast"
            | "fmul_fast"
            | "fdiv_fast"
            | "frem_fast"
            => {
                let a = this.read_immediate(args[0])?;
                let b = this.read_immediate(args[1])?;
                let op = match intrinsic_name {
                    "fadd_fast" => mir::BinOp::Add,
                    "fsub_fast" => mir::BinOp::Sub,
                    "fmul_fast" => mir::BinOp::Mul,
                    "fdiv_fast" => mir::BinOp::Div,
                    "frem_fast" => mir::BinOp::Rem,
                    _ => bug!(),
                };
                this.binop_ignore_overflow(op, a, b, dest)?;
            }

            #[rustfmt::skip]
            | "minnumf32"
            | "maxnumf32"
            | "copysignf32"
            => {
                let a = this.read_scalar(args[0])?.to_f32()?;
                let b = this.read_scalar(args[1])?.to_f32()?;
                let res = match intrinsic_name {
                    "minnumf32" => a.min(b),
                    "maxnumf32" => a.max(b),
                    "copysignf32" => a.copy_sign(b),
                    _ => bug!(),
                };
                this.write_scalar(Scalar::from_f32(res), dest)?;
            }

            #[rustfmt::skip]
            | "minnumf64"
            | "maxnumf64"
            | "copysignf64"
            => {
                let a = this.read_scalar(args[0])?.to_f64()?;
                let b = this.read_scalar(args[1])?.to_f64()?;
                let res = match intrinsic_name {
                    "minnumf64" => a.min(b),
                    "maxnumf64" => a.max(b),
                    "copysignf64" => a.copy_sign(b),
                    _ => bug!(),
                };
                this.write_scalar(Scalar::from_f64(res), dest)?;
            }

            "exact_div" =>
                this.exact_div(this.read_immediate(args[0])?, this.read_immediate(args[1])?, dest)?,

            "forget" => {}

            #[rustfmt::skip]
            | "likely"
            | "unlikely"
            => {
                // These just return their argument
                let b = this.read_immediate(args[0])?;
                this.write_immediate(*b, dest)?;
            }

            "init" => {
                // Check fast path: we don't want to force an allocation in case the destination is a simple value,
                // but we also do not want to create a new allocation with 0s and then copy that over.
                // FIXME: We do not properly validate in case of ZSTs and when doing it in memory!
                // However, this only affects direct calls of the intrinsic; calls to the stable
                // functions wrapping them do get their validation.
                // FIXME: should we check that the destination pointer is aligned even for ZSTs?
                if !dest.layout.is_zst() {
                    match dest.layout.abi {
                        layout::Abi::Scalar(ref s) => {
                            let x = Scalar::from_int(0, s.value.size(this));
                            this.write_scalar(x, dest)?;
                        }
                        layout::Abi::ScalarPair(ref s1, ref s2) => {
                            let x = Scalar::from_int(0, s1.value.size(this));
                            let y = Scalar::from_int(0, s2.value.size(this));
                            this.write_immediate(Immediate::ScalarPair(x.into(), y.into()), dest)?;
                        }
                        _ => {
                            // Do it in memory
                            let mplace = this.force_allocation(dest)?;
                            mplace.meta.unwrap_none(); // must be sized
                            this.memory.write_bytes(
                                mplace.ptr,
                                iter::repeat(0u8).take(dest.layout.size.bytes() as usize),
                            )?;
                        }
                    }
                }
            }

            "pref_align_of" => {
                let ty = substs.type_at(0);
                let layout = this.layout_of(ty)?;
                let align = layout.align.pref.bytes();
                let ptr_size = this.pointer_size();
                let align_val = Scalar::from_uint(align as u128, ptr_size);
                this.write_scalar(align_val, dest)?;
            }

            "move_val_init" => {
                let place = this.deref_operand(args[0])?;
                this.copy_op(args[1], place.into())?;
            }

            "offset" => {
                let offset = this.read_scalar(args[1])?.to_machine_isize(this)?;
                let ptr = this.read_scalar(args[0])?.not_undef()?;
                let result_ptr = this.pointer_offset_inbounds(ptr, substs.type_at(0), offset)?;
                this.write_scalar(result_ptr, dest)?;
            }

            "panic_if_uninhabited" => {
                let ty = substs.type_at(0);
                let layout = this.layout_of(ty)?;
                if layout.abi.is_uninhabited() {
                    // FIXME: This should throw a panic in the interpreted program instead.
                    throw_unsup_format!("Trying to instantiate uninhabited type {}", ty)
                }
            }

            "powf32" => {
                // FIXME: Using host floats.
                let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
                let f2 = f32::from_bits(this.read_scalar(args[1])?.to_u32()?);
                this.write_scalar(Scalar::from_u32(f.powf(f2).to_bits()), dest)?;
            }

            "powf64" => {
                // FIXME: Using host floats.
                let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
                let f2 = f64::from_bits(this.read_scalar(args[1])?.to_u64()?);
                this.write_scalar(Scalar::from_u64(f.powf(f2).to_bits()), dest)?;
            }

            "fmaf32" => {
                let a = this.read_scalar(args[0])?.to_f32()?;
                let b = this.read_scalar(args[1])?.to_f32()?;
                let c = this.read_scalar(args[2])?.to_f32()?;
                let res = a.mul_add(b, c).value;
                this.write_scalar(Scalar::from_f32(res), dest)?;
            }

            "fmaf64" => {
                let a = this.read_scalar(args[0])?.to_f64()?;
                let b = this.read_scalar(args[1])?.to_f64()?;
                let c = this.read_scalar(args[2])?.to_f64()?;
                let res = a.mul_add(b, c).value;
                this.write_scalar(Scalar::from_f64(res), dest)?;
            }

            "powif32" => {
                // FIXME: Using host floats.
                let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
                let i = this.read_scalar(args[1])?.to_i32()?;
                this.write_scalar(Scalar::from_u32(f.powi(i).to_bits()), dest)?;
            }

            "powif64" => {
                // FIXME: Using host floats.
                let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
                let i = this.read_scalar(args[1])?.to_i32()?;
                this.write_scalar(Scalar::from_u64(f.powi(i).to_bits()), dest)?;
            }

            "size_of_val" => {
                let mplace = this.deref_operand(args[0])?;
                let (size, _) = this
                    .size_and_align_of_mplace(mplace)?
                    .expect("size_of_val called on extern type");
                let ptr_size = this.pointer_size();
                this.write_scalar(Scalar::from_uint(size.bytes() as u128, ptr_size), dest)?;
            }

            #[rustfmt::skip]
            | "min_align_of_val"
            | "align_of_val"
            => {
                let mplace = this.deref_operand(args[0])?;
                let (_, align) = this
                    .size_and_align_of_mplace(mplace)?
                    .expect("size_of_val called on extern type");
                let ptr_size = this.pointer_size();
                this.write_scalar(Scalar::from_uint(align.bytes(), ptr_size), dest)?;
            }

            "unchecked_div" => {
                let l = this.read_immediate(args[0])?;
                let r = this.read_immediate(args[1])?;
                let rval = r.to_scalar()?.to_bits(args[1].layout.size)?;
                if rval == 0 {
                    throw_ub_format!("Division by 0 in unchecked_div");
                }
                this.binop_ignore_overflow(mir::BinOp::Div, l, r, dest)?;
            }

            "unchecked_rem" => {
                let l = this.read_immediate(args[0])?;
                let r = this.read_immediate(args[1])?;
                let rval = r.to_scalar()?.to_bits(args[1].layout.size)?;
                if rval == 0 {
                    throw_ub_format!("Division by 0 in unchecked_rem");
                }
                this.binop_ignore_overflow(mir::BinOp::Rem, l, r, dest)?;
            }

            #[rustfmt::skip]
            | "unchecked_add"
            | "unchecked_sub"
            | "unchecked_mul"
            => {
                let l = this.read_immediate(args[0])?;
                let r = this.read_immediate(args[1])?;
                let op = match intrinsic_name {
                    "unchecked_add" => mir::BinOp::Add,
                    "unchecked_sub" => mir::BinOp::Sub,
                    "unchecked_mul" => mir::BinOp::Mul,
                    _ => bug!(),
                };
                let (res, overflowed, _ty) = this.overflowing_binary_op(op, l, r)?;
                if overflowed {
                    throw_ub_format!("Overflowing arithmetic in {}", intrinsic_name);
                }
                this.write_scalar(res, dest)?;
            }

            "uninit" => {
                // Check fast path: we don't want to force an allocation in case the destination is a simple value,
                // but we also do not want to create a new allocation with 0s and then copy that over.
                // FIXME: We do not properly validate in case of ZSTs and when doing it in memory!
                // However, this only affects direct calls of the intrinsic; calls to the stable
                // functions wrapping them do get their validation.
                // FIXME: should we check alignment for ZSTs?
                if !dest.layout.is_zst() {
                    match dest.layout.abi {
                        layout::Abi::Scalar(..) => {
                            let x = ScalarMaybeUndef::Undef;
                            this.write_immediate(Immediate::Scalar(x), dest)?;
                        }
                        layout::Abi::ScalarPair(..) => {
                            let x = ScalarMaybeUndef::Undef;
                            this.write_immediate(Immediate::ScalarPair(x, x), dest)?;
                        }
                        _ => {
                            // Do it in memory
                            let mplace = this.force_allocation(dest)?;
                            mplace.meta.unwrap_none();
                            let ptr = mplace.ptr.assert_ptr();
                            // We know the return place is in-bounds
                            this.memory.get_raw_mut(ptr.alloc_id)?.mark_definedness(
                                ptr,
                                dest.layout.size,
                                false,
                            );
                        }
                    }
                }
            }

            "write_bytes" => {
                let ty = substs.type_at(0);
                let ty_layout = this.layout_of(ty)?;
                let val_byte = this.read_scalar(args[1])?.to_u8()?;
                let ptr = this.read_scalar(args[0])?.not_undef()?;
                let count = this.read_scalar(args[2])?.to_machine_usize(this)?;
                let byte_count = ty_layout.size * count;
                this.memory
                    .write_bytes(ptr, iter::repeat(val_byte).take(byte_count.bytes() as usize))?;
            }

            name => throw_unsup_format!("unimplemented intrinsic: {}", name),
        }

        this.dump_place(*dest);
        this.go_to_block(ret);
        Ok(())
    }
}