/// Modular multiplication of the type.
pub trait ModMul<T> {
    /// Modular multiplication using the given modulus type. If it's possible,
    /// we suggest using Barrett values, which are much faster than doing
    /// modulo with the number types.
    fn modmul(&self, x: &Self, m: &T) -> Self;
}

macro_rules! modmul_impls {
    ($name: ident, $dbl: ident, $barrett: ident) => {
        impl ModMul<$name> for $name {
            fn modmul(&self, x: &$name, m: &$name) -> $name {
                let mulres      = (self as &$name) * x;
                let bigm        = $dbl::from(m);
                let (_, bigres) = mulres.divmod(&bigm);
                $name::from(bigres)
            }
        }

        impl ModMul<$barrett> for $name {
            fn modmul(&self, x: &$name, m: &$barrett) -> $name {
                let mulres = (self as &$name) * x;
                m.reduce(&mulres)
            }
        }
    };
}

#[cfg(test)]
macro_rules! generate_modmul_tests {
    ($name: ident, $lname: ident) => {
        #[test]
        fn $lname() {
            generate_modmul_tests!(body $name, $lname);
        }
    };
    (ignore $name: ident, $lname: ident) => {
        #[test]
        #[ignore]
        fn $lname() {
            generate_modmul_tests!(body $name, $lname);
        }
    };
    (body $name: ident, $lname: ident) => {
        let fname = format!("testdata/modmul/{}.tests", stringify!($name));
        run_test(fname.to_string(), 6, |case| {
            let (neg0, abytes) = case.get("a").unwrap();
            let (neg1, bbytes) = case.get("b").unwrap();
            let (neg2, mbytes) = case.get("m").unwrap();
            let (neg3, cbytes) = case.get("c").unwrap();
            assert!(!neg0 && !neg1 && !neg2 && !neg3);

            let a = $name::from_bytes(abytes);
            let b = $name::from_bytes(bbytes);
            let m = $name::from_bytes(mbytes);
            let c = $name::from_bytes(cbytes);
            assert_eq!(c, a.modmul(&b, &m));
        });
    };
}

#[cfg(test)]
macro_rules! generate_barrett_modmul_tests {
    ($name: ident, $lname: ident, $bname: ident) => {
        #[test]
        fn $lname() {
            generate_barrett_modmul_tests!(body $name, $lname, $bname);
        }
    };
    (ignore $name: ident, $lname: ident, $bname: ident) => {
        #[test]
        #[ignore]
        fn $lname() {
            generate_barrett_modmul_tests!(body $name, $lname, $bname);
        }
    };
    (body $name: ident, $lname: ident, $bname: ident) => {
        let fname = format!("testdata/modmul/{}.tests", stringify!($name));
        run_test(fname.to_string(), 6, |case| {
            let (neg0, abytes) = case.get("a").unwrap();
            let (neg1, bbytes) = case.get("b").unwrap();
            let (neg2, mbytes) = case.get("m").unwrap();
            let (neg3, cbytes) = case.get("c").unwrap();
            let (neg4, kbytes) = case.get("k").unwrap();
            let (neg5, ubytes) = case.get("u").unwrap();
            assert!(!neg0 && !neg1 && !neg2 && !neg3 && !neg4 && !neg5);

            let a    = $name::from_bytes(abytes);
            let b    = $name::from_bytes(bbytes);
            let m    = $name::from_bytes(mbytes);
            let c    = $name::from_bytes(cbytes);
            let kbig = $name::from_bytes(kbytes);
            let k    = usize::from(kbig);
            let mu   = $bname::from_bytes(ubytes);
            let bar  = $name::new_barrett(k, $bname::from(m), mu);

            if k == a.value.len() {
                assert_eq!(c, a.modmul(&b, &bar));
            }


        });
    };
}