//! Interfaces needed to support testing with multi-precision floating point numbers.
//!
//! Within this module, the macros create a submodule for each `libm` function. These contain
//! a struct named `Operation` that implements [`MpOp`].

use std::cmp::Ordering;
use std::ffi::{c_int, c_long};

use az::Az;
use gmp_mpfr_sys::mpfr::rnd_t;
use rug::Assign;
pub use rug::Float as MpFloat;
use rug::float::Round;
use rug::float::Round::Nearest;
use rug::ops::{PowAssignRound, RemAssignRound};

use crate::{Float, MathOp};

/// Create a multiple-precision float with the correct number of bits for a concrete float type.
fn new_mpfloat<F: Float>() -> MpFloat {
    MpFloat::new(F::SIG_BITS + 1)
}

/// Set subnormal emulation and convert to a concrete float type.
fn prep_retval<F: Float>(mp: &mut MpFloat, ord: Ordering) -> F
where
    for<'a> &'a MpFloat: az::Cast<F>,
{
    mp.subnormalize_ieee_round(ord, Nearest);
    (&*mp).az::<F>()
}

/// Structures that represent a float operation.
///
pub trait MpOp: MathOp {
    /// The struct itself should hold any context that can be reused among calls to `run` (allocated
    /// `MpFloat`s).
    type MpTy;

    /// Create a new instance.
    fn new_mp() -> Self::MpTy;

    /// Perform the operation.
    ///
    /// Usually this means assigning inputs to cached floats, performing the operation, applying
    /// subnormal approximation, and converting the result back to concrete values.
    fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet;
}

/// Implement `MpOp` for functions with a single return value.
macro_rules! impl_mp_op {
    // Matcher for unary functions
    (
        fn_name: $fn_name:ident,
        RustFn: fn($_fty:ty,) -> $_ret:ty,
        attrs: [$($attr:meta),*],
        fn_extra: $fn_name_normalized:expr,
    ) => {
        paste::paste! {
            $(#[$attr])*
            impl MpOp for crate::op::$fn_name::Routine {
                type MpTy = MpFloat;

                fn new_mp() -> Self::MpTy {
                    new_mpfloat::<Self::FTy>()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.assign(input.0);
                    let ord = this.[< $fn_name_normalized _round >](Nearest);
                    prep_retval::<Self::RustRet>(this, ord)
                }
            }
        }
    };
    // Matcher for binary functions
    (
        fn_name: $fn_name:ident,
        RustFn: fn($_fty:ty, $_fty2:ty,) -> $_ret:ty,
        attrs: [$($attr:meta),*],
        fn_extra: $fn_name_normalized:expr,
    ) => {
        paste::paste! {
            $(#[$attr])*
            impl MpOp for crate::op::$fn_name::Routine {
                type MpTy = (MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (new_mpfloat::<Self::FTy>(), new_mpfloat::<Self::FTy>())
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(input.1);
                    let ord = this.0.[< $fn_name_normalized _round >](&this.1, Nearest);
                    prep_retval::<Self::RustRet>(&mut this.0, ord)
                }
            }
        }
    };
    // Matcher for ternary functions
    (
        fn_name: $fn_name:ident,
        RustFn: fn($_fty:ty, $_fty2:ty, $_fty3:ty,) -> $_ret:ty,
        attrs: [$($attr:meta),*],
        fn_extra: $fn_name_normalized:expr,
    ) => {
        paste::paste! {
            $(#[$attr])*
            impl MpOp for crate::op::$fn_name::Routine {
                type MpTy = (MpFloat, MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (
                        new_mpfloat::<Self::FTy>(),
                        new_mpfloat::<Self::FTy>(),
                        new_mpfloat::<Self::FTy>(),
                    )
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(input.1);
                    this.2.assign(input.2);
                    let ord = this.0.[< $fn_name_normalized _round >](&this.1, &this.2, Nearest);
                    prep_retval::<Self::RustRet>(&mut this.0, ord)
                }
            }
        }
    };
}

libm_macros::for_each_function! {
    callback: impl_mp_op,
    emit_types: [RustFn],
    skip: [
        // Most of these need a manual implementation
        fabs, ceil, copysign, floor, rint, round, trunc,
        fabsf, ceilf, copysignf, floorf, rintf, roundf, truncf,
        fmod, fmodf, frexp, frexpf, ilogb, ilogbf, jn, jnf, ldexp, ldexpf,
        lgamma_r, lgammaf_r, modf, modff, nextafter, nextafterf, pow,powf,
        remquo, remquof, scalbn, scalbnf, sincos, sincosf, yn, ynf,
        copysignf16, copysignf128, fabsf16, fabsf128,
    ],
    fn_extra: match MACRO_FN_NAME {
        // Remap function names that are different between mpfr and libm
        expm1 | expm1f => exp_m1,
        fabs | fabsf => abs,
        fdim | fdimf => positive_diff,
        fma | fmaf => mul_add,
        fmax | fmaxf => max,
        fmin | fminf => min,
        lgamma | lgammaf => ln_gamma,
        log | logf => ln,
        log1p | log1pf => ln_1p,
        tgamma | tgammaf => gamma,
        _ => MACRO_FN_NAME_NORMALIZED
    }
}

/// Implement unary functions that don't have a `_round` version
macro_rules! impl_no_round {
    // Unary matcher
    ($($fn_name:ident => $rug_name:ident;)*) => {
        paste::paste! {
            $( impl_no_round!{ @inner_unary $fn_name, $rug_name } )*
        }
    };

    (@inner_unary $fn_name:ident, $rug_name:ident) => {
        impl MpOp for crate::op::$fn_name::Routine {
            type MpTy = MpFloat;

            fn new_mp() -> Self::MpTy {
                new_mpfloat::<Self::FTy>()
            }

            fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                this.assign(input.0);
                this.$rug_name();
                prep_retval::<Self::RustRet>(this, Ordering::Equal)
            }
        }
    };
}

impl_no_round! {
    ceil => ceil_mut;
    ceilf => ceil_mut;
    fabs => abs_mut;
    fabsf => abs_mut;
    floor => floor_mut;
    floorf => floor_mut;
    rint => round_even_mut; // FIXME: respect rounding mode
    rintf => round_even_mut; // FIXME: respect rounding mode
    round => round_mut;
    roundf => round_mut;
    trunc => trunc_mut;
    truncf => trunc_mut;
}

#[cfg(f16_enabled)]
impl_no_round! {
    fabsf16 => abs_mut;
}

#[cfg(f128_enabled)]
impl_no_round! {
    fabsf128 => abs_mut;
}

/// Some functions are difficult to do in a generic way. Implement them here.
macro_rules! impl_op_for_ty {
    ($fty:ty, $suffix:literal) => {
        paste::paste! {
            impl MpOp for crate::op::[<modf $suffix>]::Routine {
                type MpTy = (MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (new_mpfloat::<Self::FTy>(), new_mpfloat::<Self::FTy>())
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(&this.0);
                    let (ord0, ord1) = this.0.trunc_fract_round(&mut this.1, Nearest);
                    (
                        prep_retval::<Self::FTy>(&mut this.1, ord0),
                        prep_retval::<Self::FTy>(&mut this.0, ord1),
                    )
                }
            }

            impl MpOp for crate::op::[<pow $suffix>]::Routine {
                type MpTy = (MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (new_mpfloat::<Self::FTy>(), new_mpfloat::<Self::FTy>())
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(input.1);
                    let ord = this.0.pow_assign_round(&this.1, Nearest);
                    prep_retval::<Self::RustRet>(&mut this.0, ord)
                }
            }

            impl MpOp for crate::op::[<fmod $suffix>]::Routine {
                type MpTy = (MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (new_mpfloat::<Self::FTy>(), new_mpfloat::<Self::FTy>())
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(input.1);
                    let ord = this.0.rem_assign_round(&this.1, Nearest);
                    prep_retval::<Self::RustRet>(&mut this.0, ord)
                }
            }

            impl MpOp for crate::op::[<frexp $suffix>]::Routine {
                type MpTy = MpFloat;

                fn new_mp() -> Self::MpTy {
                    new_mpfloat::<Self::FTy>()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    // Implementation taken from `rug::Float::to_f32_exp`.
                    this.assign(input.0);
                    let exp = this.get_exp().unwrap_or(0);
                    if exp != 0 {
                        *this >>= exp;
                    }

                    (prep_retval::<Self::FTy>(this, Ordering::Equal), exp)
                }
            }

            impl MpOp for crate::op::[<ilogb $suffix>]::Routine {
                type MpTy = MpFloat;

                fn new_mp() -> Self::MpTy {
                    new_mpfloat::<Self::FTy>()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.assign(input.0);

                    // `get_exp` follows `frexp` for `0.5 <= |m| < 1.0`. Adjust the exponent by
                    // one to scale the significand to `1.0 <= |m| < 2.0`.
                    this.get_exp().map(|v| v - 1).unwrap_or_else(|| {
                        if this.is_infinite() {
                            i32::MAX
                        } else {
                            // Zero or NaN
                            i32::MIN
                        }
                    })
                }
            }

            impl MpOp for crate::op::[<jn $suffix>]::Routine {
                type MpTy = MpFloat;

                fn new_mp() -> Self::MpTy {
                    new_mpfloat::<Self::FTy>()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    let (n, x) = input;
                    this.assign(x);
                    let ord = this.jn_round(n, Nearest);
                    prep_retval::<Self::FTy>(this, ord)
                }
            }

            // `ldexp` and `scalbn` are the same for binary floating point, so just forward all
            // methods.
            impl MpOp for crate::op::[<ldexp $suffix>]::Routine {
                type MpTy = <crate::op::[<scalbn $suffix>]::Routine as MpOp>::MpTy;

                fn new_mp() -> Self::MpTy {
                    <crate::op::[<scalbn $suffix>]::Routine as MpOp>::new_mp()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    <crate::op::[<scalbn $suffix>]::Routine as MpOp>::run(this, input)
                }
            }

            impl MpOp for crate::op::[<scalbn $suffix>]::Routine {
                type MpTy = MpFloat;

                fn new_mp() -> Self::MpTy {
                    new_mpfloat::<Self::FTy>()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.assign(input.0);
                    *this <<= input.1;
                    prep_retval::<Self::FTy>(this, Ordering::Equal)
                }
            }

            impl MpOp for crate::op::[<sincos $suffix>]::Routine {
                type MpTy = (MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (new_mpfloat::<Self::FTy>(), new_mpfloat::<Self::FTy>())
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(0.0);
                    let (sord, cord) = this.0.sin_cos_round(&mut this.1, Nearest);
                    (
                        prep_retval::<Self::FTy>(&mut this.0, sord),
                        prep_retval::<Self::FTy>(&mut this.1, cord)
                    )
                }
            }

            impl MpOp for crate::op::[<remquo $suffix>]::Routine {
                type MpTy = (MpFloat, MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (
                        new_mpfloat::<Self::FTy>(),
                        new_mpfloat::<Self::FTy>(),
                        new_mpfloat::<Self::FTy>()
                    )
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(input.1);
                    let (ord, ql) = mpfr_remquo(&mut this.2, &this.0, &this.1, Nearest);

                    // `remquo` integer results are sign-magnitude representation. Transfer the
                    // sign bit from the long result to the int result.
                    let clear = !(1 << (c_int::BITS - 1));
                    let sign = ((ql >> (c_long::BITS - 1)) as i32) << (c_int::BITS - 1);
                    let q = (ql as i32) & clear | sign;

                    (prep_retval::<Self::FTy>(&mut this.2, ord), q)
                }
            }

            impl MpOp for crate::op::[<yn $suffix>]::Routine {
                type MpTy = MpFloat;

                fn new_mp() -> Self::MpTy {
                    new_mpfloat::<Self::FTy>()
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    let (n, x) = input;
                    this.assign(x);
                    let ord = this.yn_round(n, Nearest);
                    prep_retval::<Self::FTy>(this, ord)
                }
            }
        }
    };
}

/// Version of `impl_op_for_ty` with only functions that have `f16` and `f128` implementations.
macro_rules! impl_op_for_ty_all {
    ($fty:ty, $suffix:literal) => {
        paste::paste! {
            impl MpOp for crate::op::[<copysign $suffix>]::Routine {
                type MpTy = (MpFloat, MpFloat);

                fn new_mp() -> Self::MpTy {
                    (new_mpfloat::<Self::FTy>(), new_mpfloat::<Self::FTy>())
                }

                fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
                    this.0.assign(input.0);
                    this.1.assign(input.1);
                    this.0.copysign_mut(&this.1);
                    prep_retval::<Self::RustRet>(&mut this.0, Ordering::Equal)
                }
            }
        }
    };
}

impl_op_for_ty!(f32, "f");
impl_op_for_ty!(f64, "");

#[cfg(f16_enabled)]
impl_op_for_ty_all!(f16, "f16");
impl_op_for_ty_all!(f32, "f");
impl_op_for_ty_all!(f64, "");
#[cfg(f128_enabled)]
impl_op_for_ty_all!(f128, "f128");

// `lgamma_r` is not a simple suffix so we can't use the above macro.
impl MpOp for crate::op::lgamma_r::Routine {
    type MpTy = MpFloat;

    fn new_mp() -> Self::MpTy {
        new_mpfloat::<Self::FTy>()
    }

    fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
        this.assign(input.0);
        let (sign, ord) = this.ln_abs_gamma_round(Nearest);
        let ret = prep_retval::<Self::FTy>(this, ord);
        (ret, sign as i32)
    }
}

impl MpOp for crate::op::lgammaf_r::Routine {
    type MpTy = MpFloat;

    fn new_mp() -> Self::MpTy {
        new_mpfloat::<Self::FTy>()
    }

    fn run(this: &mut Self::MpTy, input: Self::RustArgs) -> Self::RustRet {
        this.assign(input.0);
        let (sign, ord) = this.ln_abs_gamma_round(Nearest);
        let ret = prep_retval::<Self::FTy>(this, ord);
        (ret, sign as i32)
    }
}

/// `rug` does not provide `remquo` so this exposes `mpfr_remquo`. See rug#76.
fn mpfr_remquo(r: &mut MpFloat, x: &MpFloat, y: &MpFloat, round: Round) -> (Ordering, c_long) {
    let r = r.as_raw_mut();
    let x = x.as_raw();
    let y = y.as_raw();
    let mut q: c_long = 0;

    let round = match round {
        Round::Nearest => rnd_t::RNDN,
        Round::Zero => rnd_t::RNDZ,
        Round::Up => rnd_t::RNDU,
        Round::Down => rnd_t::RNDD,
        Round::AwayZero => rnd_t::RNDA,
        _ => unreachable!(),
    };

    // SAFETY: mutable and const pointers are valid and do not alias, by Rust's rules.
    let ord = unsafe { gmp_mpfr_sys::mpfr::remquo(r, &mut q, x, y, round) };
    (ord.cmp(&0), q)
}