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// The MIT License (MIT)
//
// Copyright (c) 2017 Doublify Technologies
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

extern crate time;

use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};

use time::Timespec;

/// Block of the chain.
#[derive(Debug)]
pub struct Block {
  revision: u64,
  payload: Vec<u8>,
  digest: u64,
  previous_digest: u64,
  timestamp: Timespec,
}

impl Block {
  pub fn new(revision: u64, payload: Vec<u8>, previous_digest: u64) -> Block {
    let timestamp = time::get_time();

    let digest = compute_digest(&payload);

    Block {
      revision: revision,
      payload: payload,
      digest: digest,
      previous_digest: previous_digest,
      timestamp: timestamp,
    }
  }

  /// Returns true if the given block has trusty digest.
  pub fn has_trusty_digest(&self) -> bool {
    self.digest == compute_digest(&self.payload)
  }

  /// Build the next block of the chain.
  pub fn next(&self, payload: Vec<u8>) -> Block {
    let next_revision = self.revision + 1;

    let digest = compute_digest(&payload);

    let previous_digest = self.digest;

    let timestamp = time::get_time();

    Block {
      revision: next_revision,
      payload: payload,
      digest: digest,
      previous_digest: previous_digest,
      timestamp: timestamp,
    }
  }
}

fn compute_digest<T: Hash>(state: &T) -> u64 {
  let mut sip = DefaultHasher::default();

  state.hash(&mut sip);

  sip.finish()
}


#[test]
fn new() {
  let block = Block::new(0, vec![0, 1, 2, 3], 0);

  println!("{:?}", block);
  println!("{:?}", block.next(vec![0, 0]));
}