// Copyright 2019 Stichting Organism
//
// 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.

//! Zei Errors
//! Errors related to proving and verifying proofs.

use failure::Fail;

/// Represents an error in Zei
#[derive(Eq, PartialEq, Debug, Fail, Clone)]
pub enum ZeiError {
    /// This error occurs when a proof failed to verify.
    #[fail(display = "Proof verification failed.")]
    VerificationError,
    /// This error occurs when transaction has too many outputs.
    #[fail(display = "Can't have more than 32 Outputs.")]
    OutputOverflowError,
    /// This error occurs when transaction not spending all the coins.
    #[fail(display = "Can't leave coins behind.")]
    CoinsLeftBehind,
    /// Bulletproofs Errors
    #[fail(display = "Internal error during proof creation: {}", _0)]
    ProofError(ProofError),
    #[fail(display = "Decryption failed.")]
    LockboxDecrypt
}


/// Represents an error in proof creation, verification, or parsing.
#[derive(Fail, Clone, Debug, Eq, PartialEq)]
pub enum ProofError {
    /// This error occurs when a proof failed to verify.
    #[fail(display = "Proof verification failed.")]
    VerificationError,
    /// This error occurs when the proof encoding is malformed.
    #[fail(display = "Proof data could not be parsed.")]
    FormatError,
    /// This error occurs during proving if the number of blinding
    /// factors does not match the number of values.
    #[fail(display = "Wrong number of blinding factors supplied.")]
    WrongNumBlindingFactors,
    /// This error occurs when attempting to create a proof with
    /// bitsize other than \\(8\\), \\(16\\), \\(32\\), or \\(64\\).
    #[fail(display = "Invalid bitsize, must have n = 8,16,32,64.")]
    InvalidBitsize,
    /// This error occurs when attempting to create an aggregated
    /// proof with non-power-of-two aggregation size.
    #[fail(display = "Invalid aggregation size, m must be a power of 2.")]
    InvalidAggregation,
    /// This error occurs when there are insufficient generators for the proof.
    #[fail(display = "Invalid generators size, too few generators for proof")]
    InvalidGeneratorsLength,
    /// This error results from an internal error during proving.
    ///
    /// The single-party prover is implemented by performing
    /// multiparty computation with ourselves.  However, because the
    /// MPC protocol is not exposed by the single-party API, we
    /// consider its errors to be internal errors.
    #[fail(display = "Internal error during proof creation: {}", _0)]
    ProvingError(MPCError)
}

impl From<ProofError> for ZeiError {
    fn from(e: ProofError) -> ZeiError {
        ZeiError::ProofError(e)
    }
}

impl From<MPCError> for ZeiError {
    fn from(e: MPCError) -> ZeiError {
        match e {
            MPCError::InvalidBitsize => ZeiError::from(ProofError::InvalidBitsize),
            MPCError::InvalidAggregation => ZeiError::from(ProofError::InvalidAggregation),
            MPCError::InvalidGeneratorsLength => ZeiError::from(ProofError::InvalidGeneratorsLength),
            _ => ZeiError::from(ProofError::ProvingError(e)),
        }
    }
}

impl From<MPCError> for ProofError {
    fn from(e: MPCError) -> ProofError {
        match e {
            MPCError::InvalidBitsize => ProofError::InvalidBitsize,
            MPCError::InvalidAggregation => ProofError::InvalidAggregation,
            MPCError::InvalidGeneratorsLength => ProofError::InvalidGeneratorsLength,
            _ => ProofError::ProvingError(e),
        }
    }
}

/// Represents an error during the multiparty computation protocol for
/// proof aggregation.
///
/// This is a separate type from the `ProofError` to allow a layered
/// API: although the MPC protocol is used internally for single-party
/// proving, its API should not expose the complexity of the MPC
/// protocol.
#[derive(Fail, Clone, Debug, Eq, PartialEq)]
pub enum MPCError {
    /// This error occurs when the dealer gives a zero challenge,
    /// which would annihilate the blinding factors.
    #[fail(display = "Dealer gave a malicious challenge value.")]
    MaliciousDealer,
    /// This error occurs when attempting to create a proof with
    /// bitsize other than \\(8\\), \\(16\\), \\(32\\), or \\(64\\).
    #[fail(display = "Invalid bitsize, must have n = 8,16,32,64")]
    InvalidBitsize,
    /// This error occurs when attempting to create an aggregated
    /// proof with non-power-of-two aggregation size.
    #[fail(display = "Invalid aggregation size, m must be a power of 2")]
    InvalidAggregation,
    /// This error occurs when there are insufficient generators for the proof.
    #[fail(display = "Invalid generators size, too few generators for proof")]
    InvalidGeneratorsLength,
    /// This error occurs when the dealer is given the wrong number of
    /// value commitments.
    #[fail(display = "Wrong number of value commitments")]
    WrongNumBitCommitments,
    /// This error occurs when the dealer is given the wrong number of
    /// polynomial commitments.
    #[fail(display = "Wrong number of value commitments")]
    WrongNumPolyCommitments,
    /// This error occurs when the dealer is given the wrong number of
    /// proof shares.
    #[fail(display = "Wrong number of proof shares")]
    WrongNumProofShares,
    /// This error occurs when one or more parties submit malformed
    /// proof shares.
    #[fail(display = "Malformed proof shares from parties {:?}", bad_shares)]
    MalformedProofShares {
        /// A vector with the indexes of the parties whose shares were malformed.
        bad_shares: Vec<usize>,
    },
}