// Bitcoin Hashes Library
// Written in 2018 by
//   Andrew Poelstra <apoelstra@wpsoftware.net>
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//

//! Rust hashes library.
//!
//! This is a simple, no-dependency library which implements the hash functions
//! needed by Bitcoin. These are SHA256, SHA256d, and RIPEMD160. As an ancillary
//! thing, it exposes hexadecimal serialization and deserialization, since these
//! are needed to display hashes anway.
//!

// Coding conventions
#![deny(non_upper_case_globals)]
#![deny(non_camel_case_types)]
#![deny(non_snake_case)]
#![deny(unused_mut)]
#![deny(missing_docs)]

// Experimental features we need
#![cfg_attr(docsrs, feature(doc_cfg))]

// In general, rust is absolutely horrid at supporting users doing things like,
// for example, compiling Rust code for real environments. Disable useless lints
// that don't do anything but annoy us and cant actually ever be resolved.
#![allow(bare_trait_objects)]
#![allow(ellipsis_inclusive_range_patterns)]

#![cfg_attr(all(not(test), not(feature = "std")), no_std)]
#![cfg_attr(all(test, feature = "unstable"), feature(test))]
#[cfg(all(test, feature = "unstable"))] extern crate test;

#[cfg(any(test, feature = "std"))] extern crate core;
#[cfg(feature = "core2")] extern crate core2;
#[cfg(feature = "alloc")] extern crate alloc;
#[cfg(all(not(feature = "alloc"), feature = "std"))] use std as alloc;
#[cfg(feature = "serde")] pub extern crate serde;
#[cfg(all(test,feature = "serde"))] extern crate serde_test;

#[doc(hidden)]
pub mod _export {
    /// A re-export of core::*
    pub mod _core {
        pub use core::*;
    }
}

#[cfg(feature = "schemars")] extern crate schemars;

#[macro_use] mod util;
#[macro_use] pub mod serde_macros;
#[cfg(any(feature = "std", feature = "core2"))] mod impls;
pub mod error;
pub mod hex;
pub mod hash160;
pub mod hmac;
pub mod ripemd160;
pub mod sha1;
pub mod sha256;
pub mod sha256d;
pub mod sha256t;
pub mod siphash24;
pub mod sha512;
pub mod cmp;

use core::{borrow, fmt, hash, ops};

pub use hmac::{Hmac, HmacEngine};
pub use error::Error;

/// A hashing engine which bytes can be serialized into.
pub trait HashEngine: Clone + Default {
    /// Byte array representing the internal state of the hash engine.
    type MidState;

    /// Outputs the midstate of the hash engine. This function should not be
    /// used directly unless you really know what you're doing.
    fn midstate(&self) -> Self::MidState;

    /// Length of the hash's internal block size, in bytes.
    const BLOCK_SIZE: usize;

    /// Add data to the hash engine.
    fn input(&mut self, data: &[u8]);

    /// Return the number of bytes already n_bytes_hashed(inputted).
    fn n_bytes_hashed(&self) -> usize;
}

/// Trait which applies to hashes of all types.
pub trait Hash: Copy + Clone + PartialEq + Eq + PartialOrd + Ord +
    hash::Hash + fmt::Debug + fmt::Display + fmt::LowerHex +
    ops::Index<ops::RangeFull, Output = [u8]> +
    ops::Index<ops::RangeFrom<usize>, Output = [u8]> +
    ops::Index<ops::RangeTo<usize>, Output = [u8]> +
    ops::Index<ops::Range<usize>, Output = [u8]> +
    ops::Index<usize, Output = u8> +
    borrow::Borrow<[u8]>
{
    /// A hashing engine which bytes can be serialized into. It is expected
    /// to implement the `io::Write` trait, and to never return errors under
    /// any conditions.
    type Engine: HashEngine;

    /// The byte array that represents the hash internally.
    type Inner: hex::FromHex;

    /// Constructs a new engine.
    fn engine() -> Self::Engine {
        Self::Engine::default()
    }

    /// Produces a hash from the current state of a given engine.
    fn from_engine(e: Self::Engine) -> Self;

    /// Length of the hash, in bytes.
    const LEN: usize;

    /// Copies a byte slice into a hash object.
    fn from_slice(sl: &[u8]) -> Result<Self, Error>;

    /// Hashes some bytes.
    fn hash(data: &[u8]) -> Self {
        let mut engine = Self::engine();
        engine.input(data);
        Self::from_engine(engine)
    }

    /// Flag indicating whether user-visible serializations of this hash
    /// should be backward. For some reason Satoshi decided this should be
    /// true for `Sha256dHash`, so here we are.
    const DISPLAY_BACKWARD: bool = false;

    /// Unwraps the hash and returns the underlying byte array.
    fn into_inner(self) -> Self::Inner;

    /// Unwraps the hash and returns a reference to the underlying byte array.
    fn as_inner(&self) -> &Self::Inner;

    /// Constructs a hash from the underlying byte array.
    fn from_inner(inner: Self::Inner) -> Self;

    /// Returns an all zero hash.
    ///
    /// An all zeros hash is a made up construct because there is not a known input that can create
    /// it, however it is used in various places in Bitcoin e.g., the Bitcoin genesis block's
    /// previous blockhash and the coinbase transaction's outpoint txid.
    fn all_zeros() -> Self;
}

#[cfg(test)]
mod tests {
    use crate::{Hash, sha256d};

    hash_newtype!(TestNewtype, sha256d::Hash, 32, doc="A test newtype");
    hash_newtype!(TestNewtype2, sha256d::Hash, 32, doc="A test newtype");

    #[test]
    fn convert_newtypes() {
        let h1 = TestNewtype::hash(&[]);
        let h2: TestNewtype2 = h1.as_hash().into();
        assert_eq!(&h1[..], &h2[..]);

        let h = sha256d::Hash::hash(&[]);
        let h2: TestNewtype = h.to_string().parse().unwrap();
        assert_eq!(h2.as_hash(), h);
    }
}