// Copyright 2017 int08h LLC
//
// 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.

//!
//! An implementation of the [Roughtime](https://roughtime.googlesource.com/roughtime)
//! secure time synchronization protocol.
//!
//! Roughtime aims to achieve rough time synchronisation in a secure way that doesn't 
//! depend on any particular time server, and in such a way that, if a time server does 
//! misbehave, clients end up with cryptographic proof of it. 
//!
//! # Protocol
//!
//! Roughtime messages are represetned by [`RtMessage`](struct.RtMessage.html) which 
//! implements the mapping of Roughtime `u32` [`tags`](enum.Tag.html) to byte-strings.
//!
//! # Client
//!
//! A Roughtime client can be found in `src/bin/client.rs`. To run the client:
//!
//! ```bash
//! $ cargo run --release --bin client roughtime.int08h.com 2002
//! ```
//!
//! Consult the client's `--help` output for all runtime options.
//!
//! # Server
//!
//! A Roughtime server implementation is in `src/bin/server.rs`. The server is 
//! configured via a yaml file:
//!
//! ```yaml
//! interface: 127.0.0.1
//! port: 8686
//! seed: f61075c988feb9cb700a4a6a3291bfbc9cab11b9c9eca8c802468eb38a43d7d3
//! batch_size: 64
//! ```
//!
//! Where:
//!
//!   * **interface** - IP address or interface name for listening to client requests
//!   * **port** - UDP port to listen to requests
//!   * **seed** - A 32-byte hexadecimal value used as the seed to generate the 
//!                server's long-term key pair. **This is a secret value**, treat it
//!                with care.
//!   * **batch_size** - The number of requests to process in one batch. All nonces
//!                      in a batch are used to build a Merkle tree, the root of which
//!                      is signed.
//!
//! To run the server:
//!
//! ```bash
//! $ cargo run --release --bin server /path/to/config.file
//! ```
//!

extern crate byteorder;

mod error;
mod tag;
mod message;

pub mod sign;
pub mod merkle;

pub use error::Error;
pub use tag::Tag;
pub use message::RtMessage;

/// Version of Roughenough
pub const VERSION: &str = "1.0.0";

//  Constants and magic numbers of the Roughtime protocol

/// Minimum size (in bytes) of a client request
pub const MIN_REQUEST_LENGTH: u32 = 1024;

/// Minimum size (in bytes) of seeds used to derive private keys
pub const MIN_SEED_LENGTH: u32 = 32;

/// Size (in bytes) of an Ed25519 public key
pub const PUBKEY_LENGTH: u32 = 32;

/// Size (in bytes) of the client's nonce
pub const NONCE_LENGTH: u32 = 64;

/// Size (in bytes) of an Ed25519 signature
pub const SIGNATURE_LENGTH: u32 = 64;

/// Size (in bytes) of a SHA-512 hash
pub const HASH_LENGTH: u32 = 64;

/// Size (in bytes) of server's timestamp value
pub const TIMESTAMP_LENGTH: u32 = 8;

/// Size (in bytes) of server's time uncertainty value
pub const RADIUS_LENGTH: u32 = 4;

/// Prefixed to the server's certificate before generating or verifying certificate's signature
pub const CERTIFICATE_CONTEXT: &str = "RoughTime v1 delegation signature--\x00";

/// Prefixed to the server's response before generating or verifying the server's signature
pub const SIGNED_RESPONSE_CONTEXT: &str = "RoughTime v1 response signature\x00";

/// Value prepended to leaves prior to hashing
pub const TREE_LEAF_TWEAK: &[u8] = &[0x00];

/// Value prepended to nodes prior to hashing
pub const TREE_NODE_TWEAK: &[u8] = &[0x01];