[SPEC] Anchor integration into wasm-utils

[lazovicff]

Anchor will have its own ProofInput, Leaf, and Proof. It will also have its own generate_proof function. This should be placed in src/wasm/anchor.rs

ProofInput:

struct ProofInput {
    leaves: Vec<Vec<u8>>,
    index: u64,
    roots: Vec<Vec<u8>>,
    recipient: Vec<u8>,
    relayer: Vec<u8>,
    commitment: Vec<u8>,
    fee: u128,
    refund: u128,
}

pub struct ProofInputBuilder {
    leaves: Option<Vec<Vec<u8>>>,
    index: Option<u64>,
    roots: Option<Vec<Vec<u8>>>,
    recipient: Option<Vec<u8>>,
    relayer: Vec<u8>,
    commitment: Vec<u8>,
    fee: Option<u128>,
    refund: Option<u128>,
}

For Proof:

#[wasm_bindgen]
pub struct Proof {
    #[wasm_bindgen(skip)]
    pub proof: String,
    #[wasm_bindgen(skip)]
    pub nullifier_hash: String,
    #[wasm_bindgen(skip)]
    pub roots: Vec<String>,
}

#[wasm_bindgen]
impl Proof {
    #[wasm_bindgen(getter)]
    pub fn proof(&self) -> JsString {
        self.proof.clone().into()
    }
    
    #[wasm_bindgen(getter)]
    pub fn nullifier_hash(&self) -> JsString {
        self.nullifier_hash.clone().into()
    }
    
    #[wasm_bindgen(getter)]
    pub fn roots(&self) -> Vec<JsString> {
        self.roots.clone().into()
    }
}

#[wasm_bindgen]
fn generate_proof_js(note: Note, proof_input: ProofInput) -> Proof {
    // Get the values from note and proof_input and convert them to rust types
    // Call generate_proof from arkworks gadgets repo which returns proof (Vec<u8u>), nullified (Vec<u8>), roots (Vec<Vec<u8>>)
}

For generating secrets:

pub fn generate_secrets(
    prefix: Prefix,
    exponentiation: i8,
    width: usize,
    curve: Curve,
    rng: &mut OsRng,
) -> Result<Vec<u8>, OpStatusCode> {
    let secrets: Vec<u8> = match (curve, exponentiation, width) {
        ...
        (Prefix::Anchor, Curve::Bls381, 5, 4) => {
            let (secret_bytes, nullifier_bytes, ..) = setup_anchor_leaf_x5_4::<BlsFr, _>(ArkworksCurve::Bls381, rng);
            [secret_bytes, nullifier_bytes].concat()
        }
        (Prefix::Anchor, Curve::Bn254, 5, 4) => {
            let (secret_bytes, nullifier_bytes, ..) = setup_anchor_leaf_x5_4::<Bn254Fr, _>(ArkworksCurve::Bn254, rng);
            [secret_bytes, nullifier_bytes].concat()
        }
        ...
    };
    Ok(secrets)
}