use crate::types::Type;

/// Opcodes supported by the VM
#[derive(Copy, Clone, Debug)]
#[repr(u8)]
pub enum Opcode {
    /// Elliptic curve addition
    EcAdd = 0x00,
    /// Elliptic curve multiplication
    EcMul = 0x01,
    /// Elliptic curve multiplication with a Base field element
    EcMulBase = 0x02,
    /// Elliptic curve multiplication with a u64 wrapped in a Scalar element
    EcMulShort = 0x03,

    /// Get the x coordinate of an elliptic curve point
    EcGetX = 0x08,
    /// Get the y coordinate of an elliptic curve point
    EcGetY = 0x09,

    /// Poseidon hash of N elements
    PoseidonHash = 0x10,

    /// Calculate merkle root given given a position, Merkle path, and an element
    CalculateMerkleRoot = 0x20,

    /// Constrain a Base field element to a circuit's public input
    ConstrainInstance = 0xf0,

    /// Intermediate opcode for the compiler, should never appear in the result
    Noop = 0xff,
}

impl Opcode {
    /// Return a tuple of vectors of types that are accepted by a specific opcode
    /// `r.0` is the return type(s) and `r.1` is the argument type(s).
    pub fn arg_types(&self) -> (Vec<Type>, Vec<Type>) {
        match self {
            // (return_type, opcode_arg_types)
            Opcode::EcAdd => (vec![Type::EcPoint], vec![Type::EcPoint, Type::EcPoint]),
            Opcode::EcMul => (vec![Type::EcPoint], vec![Type::Scalar, Type::EcFixedPoint]),
            Opcode::EcMulBase => (vec![Type::EcPoint], vec![Type::Base, Type::EcFixedPoint]),
            Opcode::EcMulShort => (vec![Type::EcPoint], vec![Type::Base, Type::EcFixedPoint]),
            Opcode::EcGetX => (vec![Type::Base], vec![Type::EcPoint]),
            Opcode::EcGetY => (vec![Type::Base], vec![Type::EcPoint]),
            Opcode::PoseidonHash => (vec![Type::Base], vec![Type::BaseArray]),
            Opcode::CalculateMerkleRoot => {
                (vec![Type::Base], vec![Type::Uint32, Type::MerklePath, Type::Base])
            }
            Opcode::ConstrainInstance => (vec![], vec![Type::Base]),
            Opcode::Noop => (vec![], vec![]),
        }
    }
}