// Copyright 2018 The Grin Developers
//
// 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.

//! Core types

pub mod block;
pub mod committed;
pub mod compact_block;
pub mod hash;
pub mod id;
pub mod merkle_proof;
pub mod pmmr;
pub mod target;
pub mod transaction;
pub mod verifier_cache;

use consensus::GRIN_BASE;
#[allow(dead_code)]
use rand::{thread_rng, Rng};
use std::{fmt, iter};

use util::secp::pedersen::Commitment;

pub use self::block::*;
pub use self::committed::Committed;
pub use self::compact_block::*;
pub use self::id::ShortId;
pub use self::transaction::*;
use core::hash::Hashed;
use global;
use ser::{self, Readable, Reader, Writeable, Writer};

/// A Cuckoo Cycle proof of work, consisting of the shift to get the graph
/// size (i.e. 31 for Cuckoo31 with a 2^31 or 1<<31 graph size) and the nonces
/// of the graph solution. While being expressed as u64 for simplicity, each
/// nonce is strictly less than half the cycle size (i.e. <2^30 for Cuckoo 31).
///
/// The hash of the `Proof` is the hash of its packed nonces when serializing
/// them at their exact bit size. The resulting bit sequence is padded to be
/// byte-aligned.
///
#[derive(Clone, PartialOrd, PartialEq)]
pub struct Proof {
	/// Power of 2 used for the size of the cuckoo graph
	pub cuckoo_sizeshift: u8,
	/// The nonces
	pub nonces: Vec<u64>,
}

impl fmt::Debug for Proof {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		write!(f, "Cuckoo{}(", self.cuckoo_sizeshift)?;
		for (i, val) in self.nonces[..].iter().enumerate() {
			write!(f, "{:x}", val)?;
			if i < self.nonces.len() - 1 {
				write!(f, " ")?;
			}
		}
		write!(f, ")")
	}
}

impl Eq for Proof {}

impl Proof {
	/// Builds a proof with provided nonces at default sizeshift
	pub fn new(mut in_nonces: Vec<u64>) -> Proof {
		in_nonces.sort();
		Proof {
			cuckoo_sizeshift: global::min_sizeshift(),
			nonces: in_nonces,
		}
	}

	/// Builds a proof with all bytes zeroed out
	pub fn zero(proof_size: usize) -> Proof {
		Proof {
			cuckoo_sizeshift: global::min_sizeshift(),
			nonces: vec![0; proof_size],
		}
	}

	/// Builds a proof with random POW data,
	/// needed so that tests that ignore POW
	/// don't fail due to duplicate hashes
	pub fn random(proof_size: usize) -> Proof {
		let sizeshift = global::min_sizeshift();
		let nonce_mask = (1 << (sizeshift - 1)) - 1;
		let mut rng = thread_rng();
		// force the random num to be within sizeshift bits
		let mut v: Vec<u64> = iter::repeat(())
			.map(|()| (rng.gen::<u32>() & nonce_mask) as u64)
			.take(proof_size)
			.collect();
		v.sort();
		Proof {
			cuckoo_sizeshift: global::min_sizeshift(),
			nonces: v,
		}
	}

	/// Converts the proof to a proof-of-work Target so they can be compared.
	/// Hashes the Cuckoo Proof data.
	pub fn to_difficulty(&self) -> target::Difficulty {
		target::Difficulty::from_hash_and_shift(&self.hash(), self.cuckoo_sizeshift)
	}

	/// Returns the proof size
	pub fn proof_size(&self) -> usize {
		self.nonces.len()
	}
}

impl Readable for Proof {
	fn read(reader: &mut Reader) -> Result<Proof, ser::Error> {
		let cuckoo_sizeshift = reader.read_u8()?;
		if cuckoo_sizeshift == 0 || cuckoo_sizeshift > 64 {
			return Err(ser::Error::CorruptedData);
		}

		let mut nonces = Vec::with_capacity(global::proofsize());
		let nonce_bits = cuckoo_sizeshift as usize - 1;
		let bytes_len = BitVec::bytes_len(nonce_bits * global::proofsize());
		let bits = reader.read_fixed_bytes(bytes_len)?;
		let bitvec = BitVec { bits };
		for n in 0..global::proofsize() {
			let mut nonce = 0;
			for bit in 0..nonce_bits {
				if bitvec.bit_at(n * nonce_bits + (bit as usize)) {
					nonce |= 1 << bit;
				}
			}
			nonces.push(nonce);
		}
		Ok(Proof {
			cuckoo_sizeshift,
			nonces,
		})
	}
}

impl Writeable for Proof {
	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ser::Error> {
		if writer.serialization_mode() != ser::SerializationMode::Hash {
			writer.write_u8(self.cuckoo_sizeshift)?;
		}

		let nonce_bits = self.cuckoo_sizeshift as usize - 1;
		let mut bitvec = BitVec::new(nonce_bits * global::proofsize());
		for (n, nonce) in self.nonces.iter().enumerate() {
			for bit in 0..nonce_bits {
				if nonce & (1 << bit) != 0 {
					bitvec.set_bit_at(n * nonce_bits + (bit as usize))
				}
			}
		}
		writer.write_fixed_bytes(&bitvec.bits)?;
		Ok(())
	}
}

// TODO this could likely be optimized by writing whole bytes (or even words)
// in the `BitVec` at once, dealing with the truncation, instead of bits by bits
struct BitVec {
	bits: Vec<u8>,
}

impl BitVec {
	/// Number of bytes required to store the provided number of bits
	fn bytes_len(bits_len: usize) -> usize {
		(bits_len + 7) / 8
	}

	fn new(bits_len: usize) -> BitVec {
		BitVec {
			bits: vec![0; BitVec::bytes_len(bits_len)],
		}
	}

	fn set_bit_at(&mut self, pos: usize) {
		self.bits[pos / 8] |= 1 << (pos % 8) as u8;
	}

	fn bit_at(&self, pos: usize) -> bool {
		self.bits[pos / 8] & (1 << (pos % 8) as u8) != 0
	}
}

/// Common errors
#[derive(Fail, Debug)]
pub enum Error {
	/// Human readable represenation of amount is invalid
	#[fail(display = "Amount string was invalid")]
	InvalidAmountString,
}

/// Common method for parsing an amount from human-readable, and converting
/// to internally-compatible u64

pub fn amount_from_hr_string(amount: &str) -> Result<u64, Error> {
	// no i18n yet, make sure we use '.' as the separator
	if amount.find(',').is_some() {
		return Err(Error::InvalidAmountString);
	}
	let (grins, ngrins) = match amount.find('.') {
		None => (parse_grins(amount)?, 0),
		Some(pos) => {
			let (gs, tail) = amount.split_at(pos);
			(parse_grins(gs)?, parse_ngrins(&tail[1..])?)
		}
	};
	Ok(grins * GRIN_BASE + ngrins)
}

fn parse_grins(amount: &str) -> Result<u64, Error> {
	if amount == "" {
		Ok(0)
	} else {
		amount
			.parse::<u64>()
			.map_err(|_| Error::InvalidAmountString)
	}
}

lazy_static! {
	static ref WIDTH: usize = (GRIN_BASE as f64).log(10.0) as usize + 1;
}

fn parse_ngrins(amount: &str) -> Result<u64, Error> {
	let amount = if amount.len() > *WIDTH {
		&amount[..*WIDTH]
	} else {
		amount
	};
	format!("{:0<width$}", amount, width = WIDTH)
		.parse::<u64>()
		.map_err(|_| Error::InvalidAmountString)
}

/// Common method for converting an amount to a human-readable string

pub fn amount_to_hr_string(amount: u64, truncate: bool) -> String {
	let amount = (amount as f64 / GRIN_BASE as f64) as f64;
	let hr = format!("{:.*}", WIDTH, amount);
	if truncate {
		let nzeros = hr.chars().rev().take_while(|x| x == &'0').count();
		if nzeros < *WIDTH {
			return hr.trim_right_matches('0').to_string();
		} else {
			return format!("{}0", hr.trim_right_matches('0'));
		}
	}
	hr
}

#[cfg(test)]
mod test {
	use super::*;

	#[test]
	pub fn test_amount_from_hr() {
		assert!(50123456789 == amount_from_hr_string("50.123456789").unwrap());
		assert!(50123456789 == amount_from_hr_string("50.1234567899").unwrap());
		assert!(50 == amount_from_hr_string(".000000050").unwrap());
		assert!(1 == amount_from_hr_string(".000000001").unwrap());
		assert!(0 == amount_from_hr_string(".0000000009").unwrap());
		assert!(500_000_000_000 == amount_from_hr_string("500").unwrap());
		assert!(
			5_000_000_000_000_000_000 == amount_from_hr_string("5000000000.00000000000").unwrap()
		);
		assert!(66_600_000_000 == amount_from_hr_string("66.6").unwrap());
		assert!(66_000_000_000 == amount_from_hr_string("66.").unwrap());
	}

	#[test]
	pub fn test_amount_to_hr() {
		assert!("50.123456789" == amount_to_hr_string(50123456789, false));
		assert!("50.123456789" == amount_to_hr_string(50123456789, true));
		assert!("0.000000050" == amount_to_hr_string(50, false));
		assert!("0.00000005" == amount_to_hr_string(50, true));
		assert!("0.000000001" == amount_to_hr_string(1, false));
		assert!("0.000000001" == amount_to_hr_string(1, true));
		assert!("500.000000000" == amount_to_hr_string(500_000_000_000, false));
		assert!("500.0" == amount_to_hr_string(500_000_000_000, true));
		assert!("5000000000.000000000" == amount_to_hr_string(5_000_000_000_000_000_000, false));
		assert!("5000000000.0" == amount_to_hr_string(5_000_000_000_000_000_000, true));
		assert!("66.6" == amount_to_hr_string(66600000000, true));
	}

}
