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// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

use super::{Brain, Error, KeyPair, KeyPairGenerator};
use parity_wordlist as wordlist;

/// Tries to find brain-seed keypair with address starting with given prefix.
pub struct BrainPrefix {
    prefix: Vec<u8>,
    iterations: usize,
    no_of_words: usize,
    last_phrase: String,
}

impl BrainPrefix {
    pub fn new(prefix: Vec<u8>, iterations: usize, no_of_words: usize) -> Self {
        BrainPrefix {
            prefix,
            iterations,
            no_of_words,
            last_phrase: String::new(),
        }
    }

    pub fn phrase(&self) -> &str { &self.last_phrase }
}

impl KeyPairGenerator for BrainPrefix {
    type Error = Error;

    fn generate(&mut self) -> Result<KeyPair, Error> {
        for _ in 0..self.iterations {
            let phrase = wordlist::random_phrase(self.no_of_words);
            let keypair = Brain::new(phrase.clone()).generate().unwrap();
            if keypair.address().as_ref().starts_with(&self.prefix) {
                self.last_phrase = phrase;
                return Ok(keypair);
            }
        }

        Err(Error::Custom("Could not find keypair".into()))
    }
}

#[cfg(test)]
mod tests {
    use crate::{BrainPrefix, KeyPairGenerator};

    #[test]
    fn prefix_generator() {
        let prefix = vec![0x10u8];
        let keypair = BrainPrefix::new(prefix.clone(), usize::max_value(), 12)
            .generate()
            .unwrap();
        assert!(keypair.address().as_bytes().starts_with(&prefix));
    }
}