use sp1_core_executor::events::ByteRecord;
use sp1_hypercube::{air::SP1AirBuilder, Word};
use sp1_primitives::consts::{u32_to_u16_limbs, WORD_SIZE};

use slop_air::AirBuilder;
use slop_algebra::{AbstractField, Field};
use sp1_derive::{AlignedBorrow, InputExpr, InputParams, IntoShape, SP1OperationBuilder};

use crate::{
    air::{SP1Operation, SP1OperationBuilder, WordAirBuilder},
    operations::{U16MSBOperation, U16MSBOperationInput},
};

/// A set of columns needed to compute the ADDW of two words.
#[derive(AlignedBorrow, Default, Debug, Clone, Copy, IntoShape, SP1OperationBuilder)]
#[repr(C)]
pub struct AddwOperation<T> {
    /// The result of the ADDW operation.
    pub value: [T; WORD_SIZE / 2],
    /// The msb of the result.
    pub msb: U16MSBOperation<T>,
}

impl<F: Field> AddwOperation<F> {
    pub fn populate(&mut self, record: &mut impl ByteRecord, a_u64: u64, b_u64: u64) {
        let value = (a_u64 as u32).wrapping_add(b_u64 as u32);
        let limbs = u32_to_u16_limbs(value);
        self.value = [F::from_canonical_u16(limbs[0]), F::from_canonical_u16(limbs[1])];
        // Range check
        record.add_u16_range_checks(&limbs);
        self.msb.populate_msb(record, limbs[1]);
    }

    /// Evaluate the addw operation.
    /// Assumes that `a`, `b` are valid `Word`s of u16 limbs.
    /// Constrains that `is_real` is boolean.
    /// If `is_real` is true, the `value` is constrained to a the lower u32 of the ADDW result.
    /// Also, the `msb` will be constrained to equal the most significant bit of the `value`.
    pub fn eval<AB>(
        builder: &mut AB,
        a: Word<AB::Expr>,
        b: Word<AB::Expr>,
        cols: AddwOperation<AB::Var>,
        is_real: AB::Expr,
    ) where
        AB: SP1AirBuilder + SP1OperationBuilder<U16MSBOperation<<AB as AirBuilder>::F>>,
    {
        builder.assert_bool(is_real.clone());

        let base = AB::F::from_canonical_u32(1 << 16);
        let mut builder_is_real = builder.when(is_real.clone());
        let mut carry = AB::Expr::zero();

        // The set of constraints are
        //  - carry is initialized to zero
        //  - 2^16 * carry_next + value[i] = a[i] + b[i] + carry
        //  - carry is boolean
        //  - 0 <= value[i] < 2^16
        for i in 0..WORD_SIZE / 2 {
            carry = (a[i].clone() + b[i].clone() - cols.value[i] + carry) * base.inverse();
            builder_is_real.assert_bool(carry.clone());
        }

        // Range check each limb.
        builder.slice_range_check_u16(&cols.value, is_real.clone());

        <U16MSBOperation<AB::F> as SP1Operation<AB>>::eval(
            builder,
            U16MSBOperationInput::new(cols.value[1].into(), cols.msb, is_real.clone()),
        );
    }
}

#[derive(Debug, Clone, InputParams, InputExpr)]
pub struct AddwOperationInput<AB: SP1AirBuilder> {
    pub a: Word<AB::Expr>,
    pub b: Word<AB::Expr>,
    pub cols: AddwOperation<AB::Var>,
    pub is_real: AB::Expr,
}

impl<AB> SP1Operation<AB> for AddwOperation<AB::F>
where
    AB: SP1AirBuilder + SP1OperationBuilder<U16MSBOperation<<AB as AirBuilder>::F>>,
{
    type Input = AddwOperationInput<AB>;
    type Output = ();

    fn lower(builder: &mut AB, input: Self::Input) -> Self::Output {
        Self::eval(builder, input.a, input.b, input.cols, input.is_real);
    }
}
