/*
    Copyright 2021 0KIMS association.

    * `solidity-verifiers` added comment
        This file is a template built out of [snarkJS](https://github.com/iden3/snarkjs) groth16 verifier.
        See the original ejs template [here](https://github.com/iden3/snarkjs/blob/master/templates/verifier_groth16.sol.ejs)
    *

    snarkJS is a free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    snarkJS is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
    License for more details.

    You should have received a copy of the GNU General Public License
    along with snarkJS. If not, see <https://www.gnu.org/licenses/>.
*/

contract Groth16Verifier {
    // Scalar field size
    uint256 constant r    = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
    // Base field size
    uint256 constant q   = 21888242871839275222246405745257275088696311157297823662689037894645226208583;

    // Verification Key data
    uint256 constant alphax  = {{ vkey_alpha_g1.0[0]    }};
    uint256 constant alphay  = {{ vkey_alpha_g1.0[1]    }};
    uint256 constant betax1  = {{ vkey_beta_g2.0[0][1]  }};
    uint256 constant betax2  = {{ vkey_beta_g2.0[0][0]  }};
    uint256 constant betay1  = {{ vkey_beta_g2.0[1][1]  }};
    uint256 constant betay2  = {{ vkey_beta_g2.0[1][0]  }};
    uint256 constant gammax1 = {{ vkey_gamma_g2.0[0][1] }};
    uint256 constant gammax2 = {{ vkey_gamma_g2.0[0][0] }};
    uint256 constant gammay1 = {{ vkey_gamma_g2.0[1][1] }};
    uint256 constant gammay2 = {{ vkey_gamma_g2.0[1][0] }};
    uint256 constant deltax1 = {{ vkey_delta_g2.0[0][1] }};
    uint256 constant deltax2 = {{ vkey_delta_g2.0[0][0] }};
    uint256 constant deltay1 = {{ vkey_delta_g2.0[1][1] }};
    uint256 constant deltay2 = {{ vkey_delta_g2.0[1][0] }};

    {% for (i, point) in gamma_abc_g1.iter().enumerate() %}
    uint256 constant IC{{i}}x = {{ point.0[0] }};
    uint256 constant IC{{i}}y = {{ point.0[1] }};
    {% endfor %}
    
    // Memory data
    uint16 constant pVk = 0;
    uint16 constant pPairing = 128;

    uint16 constant pLastMem = 896;

    function verifyProof(uint[2] calldata _pA, uint[2][2] calldata _pB, uint[2] calldata _pC, uint[{{ gamma_abc_len - 1 }}] calldata _pubSignals) public view returns (bool) {
        assembly {
            function checkField(v) {
                if iszero(lt(v, r)) {
                    mstore(0, 0)
                    return(0, 0x20)
                }
            }
            
            // G1 function to multiply a G1 value(x,y) to value in an address
            function g1_mulAccC(pR, x, y, s) {
                let success
                let mIn := mload(0x40)
                mstore(mIn, x)
                mstore(add(mIn, 32), y)
                mstore(add(mIn, 64), s)

                success := staticcall(sub(gas(), 2000), 7, mIn, 96, mIn, 64)

                if iszero(success) {
                    mstore(0, 0)
                    return(0, 0x20)
                }

                mstore(add(mIn, 64), mload(pR))
                mstore(add(mIn, 96), mload(add(pR, 32)))

                success := staticcall(sub(gas(), 2000), 6, mIn, 128, pR, 64)

                if iszero(success) {
                    mstore(0, 0)
                    return(0, 0x20)
                }
            }

            function checkPairing(pA, pB, pC, pubSignals, pMem) -> isOk {
                let _pPairing := add(pMem, pPairing)
                let _pVk := add(pMem, pVk)

                mstore(_pVk, IC0x)
                mstore(add(_pVk, 32), IC0y)

                // Compute the linear combination vk_x
                {% for (i, _) in gamma_abc_g1.iter().enumerate() %}
                {% if loop.first -%}
                {%- else -%}
                g1_mulAccC(_pVk, IC{{i}}x, IC{{i}}y, calldataload(add(pubSignals, {{(i-1)*32}})))
                {%- endif -%}
                {% endfor %}

                // -A
                mstore(_pPairing, calldataload(pA))
                mstore(add(_pPairing, 32), mod(sub(q, calldataload(add(pA, 32))), q))

                // B
                mstore(add(_pPairing, 64), calldataload(pB))
                mstore(add(_pPairing, 96), calldataload(add(pB, 32)))
                mstore(add(_pPairing, 128), calldataload(add(pB, 64)))
                mstore(add(_pPairing, 160), calldataload(add(pB, 96)))

                // alpha1
                mstore(add(_pPairing, 192), alphax)
                mstore(add(_pPairing, 224), alphay)

                // beta2
                mstore(add(_pPairing, 256), betax1)
                mstore(add(_pPairing, 288), betax2)
                mstore(add(_pPairing, 320), betay1)
                mstore(add(_pPairing, 352), betay2)

                // vk_x
                mstore(add(_pPairing, 384), mload(add(pMem, pVk)))
                mstore(add(_pPairing, 416), mload(add(pMem, add(pVk, 32))))


                // gamma2
                mstore(add(_pPairing, 448), gammax1)
                mstore(add(_pPairing, 480), gammax2)
                mstore(add(_pPairing, 512), gammay1)
                mstore(add(_pPairing, 544), gammay2)

                // C
                mstore(add(_pPairing, 576), calldataload(pC))
                mstore(add(_pPairing, 608), calldataload(add(pC, 32)))

                // delta2
                mstore(add(_pPairing, 640), deltax1)
                mstore(add(_pPairing, 672), deltax2)
                mstore(add(_pPairing, 704), deltay1)
                mstore(add(_pPairing, 736), deltay2)


                let success := staticcall(sub(gas(), 2000), 8, _pPairing, 768, _pPairing, 0x20)

                isOk := and(success, mload(_pPairing))
            }

            let pMem := mload(0x40)
            mstore(0x40, add(pMem, pLastMem))

            // Validate that all evaluations ∈ F
            {% for (i, _) in gamma_abc_g1.iter().enumerate() %}
            checkField(calldataload(add(_pubSignals, {{i*32}})))
            {% endfor %}

            // Validate all evaluations
            let isValid := checkPairing(_pA, _pB, _pC, _pubSignals, pMem)

            mstore(0, isValid)
            
            return(0, 0x20)
        }
    }
}