// Copyright 2015-2017 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity 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 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.  If not, see <http://www.gnu.org/licenses/>.

use std::fmt;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
use serde::de::{Error, Visitor};
use ethcore::client::BlockId;

/// Represents rpc api block number param.
#[derive(Debug, PartialEq, Clone, Hash, Eq)]
pub enum BlockNumber {
	/// Number
	Num(u64),
	/// Latest block
	Latest,
	/// Earliest block (genesis)
	Earliest,
	/// Pending block (being mined)
	Pending,
}

impl Default for BlockNumber {
	fn default() -> Self {
		BlockNumber::Latest
	}
}

impl Deserialize for BlockNumber {
	fn deserialize<D>(deserializer: D) -> Result<BlockNumber, D::Error> where D: Deserializer {
		deserializer.deserialize(BlockNumberVisitor)
	}
}

impl BlockNumber {
	/// Convert block number to min block target.
	pub fn to_min_block_num(&self) -> Option<u64> {
		match *self {
			BlockNumber::Num(ref x) => Some(*x),
			_ => None,
		}
	}
}

impl Serialize for BlockNumber {
	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer {
		match *self {
			BlockNumber::Num(ref x) => serializer.serialize_str(&format!("0x{:x}", x)),
			BlockNumber::Latest => serializer.serialize_str("latest"),
			BlockNumber::Earliest => serializer.serialize_str("earliest"),
			BlockNumber::Pending => serializer.serialize_str("pending"),
		}
	}
}

struct BlockNumberVisitor;

impl Visitor for BlockNumberVisitor {
	type Value = BlockNumber;

	fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
		write!(formatter, "a block number or 'latest', 'earliest' or 'pending'")
	}

	fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> where E: Error {
		match value {
			"latest" => Ok(BlockNumber::Latest),
			"earliest" => Ok(BlockNumber::Earliest),
			"pending" => Ok(BlockNumber::Pending),
			_ if value.starts_with("0x") => u64::from_str_radix(&value[2..], 16).map(BlockNumber::Num).map_err(|_| Error::custom("invalid block number")),
			_ => value.parse::<u64>().map(BlockNumber::Num).map_err(|_| Error::custom("invalid block number"))
		}
	}

	fn visit_string<E>(self, value: String) -> Result<Self::Value, E> where E: Error {
		self.visit_str(value.as_ref())
	}
}

impl Into<BlockId> for BlockNumber {
	fn into(self) -> BlockId {
		match self {
			BlockNumber::Num(n) => BlockId::Number(n),
			BlockNumber::Earliest => BlockId::Earliest,
			BlockNumber::Latest => BlockId::Latest,
			BlockNumber::Pending => BlockId::Pending,
		}
	}
}

#[cfg(test)]
mod tests {
	use ethcore::client::BlockId;
	use super::*;
	use serde_json;

	#[test]
	fn block_number_deserialization() {
		let s = r#"["0xa", "10", "latest", "earliest", "pending"]"#;
		let deserialized: Vec<BlockNumber> = serde_json::from_str(s).unwrap();
		assert_eq!(deserialized, vec![BlockNumber::Num(10), BlockNumber::Num(10), BlockNumber::Latest, BlockNumber::Earliest, BlockNumber::Pending])
	}

	#[test]
	fn block_number_into() {
		assert_eq!(BlockId::Number(100), BlockNumber::Num(100).into());
		assert_eq!(BlockId::Earliest, BlockNumber::Earliest.into());
		assert_eq!(BlockId::Latest, BlockNumber::Latest.into());
		assert_eq!(BlockId::Pending, BlockNumber::Pending.into());
	}
}

