// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

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

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

/// 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<'a> Deserialize<'a> for BlockNumber {
    fn deserialize<D>(deserializer: D) -> Result<BlockNumber, D::Error>
    where
        D: Deserializer<'a>,
    {
        deserializer.deserialize_any(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<'a> Visitor<'a> 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(|e| Error::custom(format!("Invalid block number: {}", e))),
            _ => Err(Error::custom(
                "Invalid block number: missing 0x prefix".to_string(),
            )),
        }
    }

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

/// Converts `BlockNumber` to `BlockId`, panics on `BlockNumber::Pending`
pub fn block_number_to_id(number: BlockNumber) -> BlockId {
    match number {
        BlockNumber::Num(num) => BlockId::Number(num),
        BlockNumber::Earliest => BlockId::Earliest,
        BlockNumber::Latest => BlockId::Latest,

        BlockNumber::Pending => panic!("`BlockNumber::Pending` should be handled manually"),
    }
}

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

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

    #[test]
    fn should_not_deserialize_decimal() {
        let s = r#""10""#;
        assert!(serde_json::from_str::<BlockNumber>(s).is_err());
    }

    #[test]
    fn normal_block_number_to_id() {
        assert_eq!(
            block_number_to_id(BlockNumber::Num(100)),
            BlockId::Number(100)
        );
        assert_eq!(block_number_to_id(BlockNumber::Earliest), BlockId::Earliest);
        assert_eq!(block_number_to_id(BlockNumber::Latest), BlockId::Latest);
    }

    #[test]
    #[should_panic]
    fn pending_block_number_to_id() {
        // Since this function is not allowed to be called in such way, panic should happen
        block_number_to_id(BlockNumber::Pending);
    }
}