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// Copyright (C) 2019-2023 Aleo Systems Inc.
// This file is part of the snarkVM library.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at:
// http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use super::*;

impl<E: Environment> FromBits for Group<E> {
    type Boolean = Boolean<E>;

    /// Initializes a new group element from the x-coordinate as a list of little-endian bits *without* trailing zeros.
    fn from_bits_le(bits_le: &[Self::Boolean]) -> Self {
        // Derive the x-coordinate for the affine group element.
        let x = Field::from_bits_le(bits_le);
        // Recover the y-coordinate and return the affine group element.
        Self::from_x_coordinate(x)
    }

    /// Initializes a new group element from the x-coordinate as a list of big-endian bits *without* leading zeros.
    fn from_bits_be(bits_be: &[Self::Boolean]) -> Self {
        // Derive the x-coordinate for the affine group element.
        let x = Field::from_bits_be(bits_be);
        // Recover the y-coordinate and return the affine group element.
        Self::from_x_coordinate(x)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use snarkvm_circuit_environment::Circuit;

    const ITERATIONS: u64 = 100;

    fn check_from_bits_le(mode: Mode, num_constants: u64, num_public: u64, num_private: u64, num_constraints: u64) {
        let mut rng = TestRng::default();

        for i in 0..ITERATIONS {
            // Sample a random element.
            let expected = Uniform::rand(&mut rng);
            let candidate = Group::<Circuit>::new(mode, expected).to_bits_le();

            Circuit::scope(&format!("{mode} {i}"), || {
                let candidate = Group::<Circuit>::from_bits_le(&candidate);
                assert_eq!(expected, candidate.eject_value());
                assert_scope!(num_constants, num_public, num_private, num_constraints);
            });
            Circuit::reset();
        }
    }

    fn check_from_bits_be(mode: Mode, num_constants: u64, num_public: u64, num_private: u64, num_constraints: u64) {
        let mut rng = TestRng::default();

        for i in 0..ITERATIONS {
            // Sample a random element.
            let expected = Uniform::rand(&mut rng);
            let candidate = Group::<Circuit>::new(mode, expected).to_bits_be();

            Circuit::scope(&format!("{mode} {i}"), || {
                let candidate = Group::<Circuit>::from_bits_be(&candidate);
                assert_eq!(expected, candidate.eject_value());
                assert_scope!(num_constants, num_public, num_private, num_constraints);
            });
            Circuit::reset();
        }
    }

    #[test]
    fn test_from_bits_le_constant() {
        check_from_bits_le(Mode::Constant, 11, 0, 0, 0);
    }

    #[test]
    fn test_from_bits_le_public() {
        check_from_bits_le(Mode::Public, 4, 0, 267, 266);
    }

    #[test]
    fn test_from_bits_le_private() {
        check_from_bits_le(Mode::Private, 4, 0, 267, 266);
    }

    #[test]
    fn test_from_bits_be_constant() {
        check_from_bits_be(Mode::Constant, 11, 0, 0, 0);
    }

    #[test]
    fn test_from_bits_be_public() {
        check_from_bits_be(Mode::Public, 4, 0, 267, 266);
    }

    #[test]
    fn test_from_bits_be_private() {
        check_from_bits_be(Mode::Private, 4, 0, 267, 266);
    }
}