#include <gtest/gtest.h>

#include <cstdint>
#include <limits>
#include <sstream>

#include "dpf/fp61.hpp"

namespace
{

using dpf::fp61;
using dpf::fp61_mod;

}  // namespace

TEST(Fp61, ReduceCanonicalizesTheModulus)
{
    EXPECT_EQ(fp61::reduce(0), 0u);
    EXPECT_EQ(fp61::reduce(1), 1u);
    EXPECT_EQ(fp61::reduce(fp61_mod), 0u);
    EXPECT_EQ(fp61::reduce(fp61_mod + 1), 1u);
    EXPECT_EQ(fp61::reduce(std::uint64_t{1} << 61), 1u);
    EXPECT_EQ(fp61::reduce(std::numeric_limits<std::uint64_t>::max()), 7u);
    EXPECT_EQ(fp61::reduce(fp61::reduce(fp61_mod + 9)), fp61::reduce(9));
}

TEST(Fp61, ArithmeticWrapsInTheField)
{
    const fp61 a{fp61_mod - 1};
    const fp61 b{3};
    EXPECT_EQ((a + b).raw(), 2u);
    EXPECT_EQ((b - a).raw(), 4u);
    EXPECT_EQ((-a).raw(), 1u);
    EXPECT_EQ((-fp61{0}).raw(), 0u);
    EXPECT_EQ((a - a).raw(), 0u);
    EXPECT_EQ((-(-a)).raw(), a.raw());
    EXPECT_EQ((a * fp61{1}).raw(), a.raw());
    EXPECT_EQ((a * fp61{0}).raw(), 0u);
    EXPECT_EQ((fp61{2} * fp61{3}).raw(), 6u);
}

TEST(Fp61, MultiplicationDistributes)
{
    const fp61 a{1000};
    const fp61 b{fp61_mod - 5};
    const fp61 c{17};
    EXPECT_EQ(((a + b) * c).raw(), (a * c + b * c).raw());
    EXPECT_EQ((a * b).raw(), (b * a).raw());
}

TEST(Fp61, StreamPrintsTheReducedValue)
{
    std::ostringstream os;
    os << fp61{fp61_mod + 4};
    EXPECT_EQ(os.str(), "4");
}