// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// 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.

//! *BLS12-381* types and host functions.

use crate::utils;
use alloc::vec::Vec;
use ark_bls12_381_ext::CurveHooks;
use ark_ec::{pairing::Pairing, CurveConfig};
use sp_runtime_interface::runtime_interface;

/// First pairing group definitions.
pub mod g1 {
	pub use ark_bls12_381_ext::g1::{BETA, G1_GENERATOR_X, G1_GENERATOR_Y};
	/// Group configuration.
	pub type Config = ark_bls12_381_ext::g1::Config<super::HostHooks>;
	/// Short Weierstrass form point affine representation.
	pub type G1Affine = ark_bls12_381_ext::g1::G1Affine<super::HostHooks>;
	/// Short Weierstrass form point projective representation.
	pub type G1Projective = ark_bls12_381_ext::g1::G1Projective<super::HostHooks>;
}

/// Second pairing group definitions.
pub mod g2 {
	pub use ark_bls12_381_ext::g2::{
		G2_GENERATOR_X, G2_GENERATOR_X_C0, G2_GENERATOR_X_C1, G2_GENERATOR_Y, G2_GENERATOR_Y_C0,
		G2_GENERATOR_Y_C1,
	};
	/// Group configuration.
	pub type Config = ark_bls12_381_ext::g2::Config<super::HostHooks>;
	/// Short Weierstrass form point affine representation.
	pub type G2Affine = ark_bls12_381_ext::g2::G2Affine<super::HostHooks>;
	/// Short Weierstrass form point projective representation.
	pub type G2Projective = ark_bls12_381_ext::g2::G2Projective<super::HostHooks>;
}

pub use self::{
	g1::{Config as G1Config, G1Affine, G1Projective},
	g2::{Config as G2Config, G2Affine, G2Projective},
};

/// Curve hooks jumping into [`host_calls`] host functions.
#[derive(Copy, Clone)]
pub struct HostHooks;

/// Configuration for *BLS12-381* curve.
pub type Config = ark_bls12_381_ext::Config<HostHooks>;

/// *BLS12-381* definition.
///
/// A generic *BLS12* model specialized with *BLS12-381* configuration.
pub type Bls12_381 = ark_bls12_381_ext::Bls12_381<HostHooks>;

impl CurveHooks for HostHooks {
	fn bls12_381_multi_miller_loop(
		g1: impl Iterator<Item = <Bls12_381 as Pairing>::G1Prepared>,
		g2: impl Iterator<Item = <Bls12_381 as Pairing>::G2Prepared>,
	) -> Result<<Bls12_381 as Pairing>::TargetField, ()> {
		let g1 = utils::encode(g1.collect::<Vec<_>>());
		let g2 = utils::encode(g2.collect::<Vec<_>>());
		let res = host_calls::bls12_381_multi_miller_loop(g1, g2).unwrap_or_default();
		utils::decode(res)
	}

	fn bls12_381_final_exponentiation(
		target: <Bls12_381 as Pairing>::TargetField,
	) -> Result<<Bls12_381 as Pairing>::TargetField, ()> {
		let target = utils::encode(target);
		let res = host_calls::bls12_381_final_exponentiation(target).unwrap_or_default();
		utils::decode(res)
	}

	fn bls12_381_msm_g1(
		bases: &[G1Affine],
		scalars: &[<G1Config as CurveConfig>::ScalarField],
	) -> Result<G1Projective, ()> {
		let bases = utils::encode(bases);
		let scalars = utils::encode(scalars);
		let res = host_calls::bls12_381_msm_g1(bases, scalars).unwrap_or_default();
		utils::decode_proj_sw(res)
	}

	fn bls12_381_msm_g2(
		bases: &[G2Affine],
		scalars: &[<G2Config as CurveConfig>::ScalarField],
	) -> Result<G2Projective, ()> {
		let bases = utils::encode(bases);
		let scalars = utils::encode(scalars);
		let res = host_calls::bls12_381_msm_g2(bases, scalars).unwrap_or_default();
		utils::decode_proj_sw(res)
	}

	fn bls12_381_mul_projective_g1(
		base: &G1Projective,
		scalar: &[u64],
	) -> Result<G1Projective, ()> {
		let base = utils::encode_proj_sw(base);
		let scalar = utils::encode(scalar);
		let res = host_calls::bls12_381_mul_projective_g1(base, scalar).unwrap_or_default();
		utils::decode_proj_sw(res)
	}

	fn bls12_381_mul_projective_g2(
		base: &G2Projective,
		scalar: &[u64],
	) -> Result<G2Projective, ()> {
		let base = utils::encode_proj_sw(base);
		let scalar = utils::encode(scalar);
		let res = host_calls::bls12_381_mul_projective_g2(base, scalar).unwrap_or_default();
		utils::decode_proj_sw(res)
	}
}

/// Interfaces for working with *Arkworks* *BLS12-381* elliptic curve related types
/// from within the runtime.
///
/// All types are (de-)serialized through the wrapper types from the `ark-scale` trait,
/// with `ark_scale::{ArkScale, ArkScaleProjective}`.
///
/// `ArkScale`'s `Usage` generic parameter is expected to be set to "not-validated"
/// and "not-compressed".
#[runtime_interface]
pub trait HostCalls {
	/// Pairing multi Miller loop for *BLS12-381*.
	///
	/// - Receives encoded:
	///   - `a`: `ArkScale<Vec<G1Affine>>`.
	///   - `b`: `ArkScale<Vec<G2Affine>>`.
	/// - Returns encoded: `ArkScale<Bls12_381::TargetField>`.
	fn bls12_381_multi_miller_loop(a: Vec<u8>, b: Vec<u8>) -> Result<Vec<u8>, ()> {
		utils::multi_miller_loop::<ark_bls12_381::Bls12_381>(a, b)
	}

	/// Pairing final exponentiation for *BLS12-381*.
	///
	/// - Receives encoded: `ArkScale<<Bls12_377::TargetField>`.
	/// - Returns encoded: `ArkScale<<Bls12_377::TargetField>`
	fn bls12_381_final_exponentiation(f: Vec<u8>) -> Result<Vec<u8>, ()> {
		utils::final_exponentiation::<ark_bls12_381::Bls12_381>(f)
	}

	/// Multi scalar multiplication on *G1* for *BLS12-381*
	///
	/// - Receives encoded:
	///   - `bases`: `ArkScale<Vec<G1Affine>>`.
	///   - `scalars`: `ArkScale<Vec<G1Config::ScalarField>>`.
	/// - Returns encoded: `ArkScaleProjective<ark_bls12_381::G1Projective>`.
	fn bls12_381_msm_g1(bases: Vec<u8>, scalars: Vec<u8>) -> Result<Vec<u8>, ()> {
		utils::msm_sw::<ark_bls12_381::g1::Config>(bases, scalars)
	}

	/// Multi scalar multiplication on *G2* for *BLS12-381*
	///
	/// - Receives encoded:
	///   - `bases`: `ArkScale<Vec<G2Affine>>`.
	///   - `scalars`: `ArkScale<Vec<G2Config::ScalarField>>`.
	/// - Returns encoded: `ArkScaleProjective<G2Projective>`.
	fn bls12_381_msm_g2(bases: Vec<u8>, scalars: Vec<u8>) -> Result<Vec<u8>, ()> {
		utils::msm_sw::<ark_bls12_381::g2::Config>(bases, scalars)
	}

	/// Projective multiplication on *G1* for *BLS12-381*.
	///
	/// - Receives encoded:
	///   - `base`: `ArkScaleProjective<G1Projective>`.
	///   - `scalar`: `ArkScale<Vec<u64>>`.
	/// - Returns encoded: `ArkScaleProjective<G1Projective>`.
	fn bls12_381_mul_projective_g1(base: Vec<u8>, scalar: Vec<u8>) -> Result<Vec<u8>, ()> {
		utils::mul_projective_sw::<ark_bls12_381::g1::Config>(base, scalar)
	}

	/// Projective multiplication on *G2* for *BLS12-381*
	///
	/// - Receives encoded:
	///   - `base`: `ArkScaleProjective<G2Projective>`.
	///   - `scalar`: `ArkScale<Vec<u64>>`.
	/// - Returns encoded: `ArkScaleProjective<G2Projective>`.
	fn bls12_381_mul_projective_g2(base: Vec<u8>, scalar: Vec<u8>) -> Result<Vec<u8>, ()> {
		utils::mul_projective_sw::<ark_bls12_381::g2::Config>(base, scalar)
	}
}
