web3 0.3.0

Ethereum JSON-RPC client.
Documentation 
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use serde::de::{Deserialize,Deserializer,Error};
use serde::ser::{Serialize,Serializer};
use types::U256;


/// Information about current blockchain syncing operations.
#[derive(Debug,Clone,PartialEq,Serialize,Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct SyncInfo {
    /// The block at which import began.
    pub starting_block: U256,

    /// The highest currently synced block.
    pub current_block: U256,
    
    /// The estimated highest block.
    pub highest_block: U256
}


/// The current state of blockchain syncing operations.
#[derive(Debug,Clone,PartialEq)]
pub enum SyncState {
    /// Blockchain is syncing.
    Syncing(SyncInfo),

    /// Blockchain is not syncing.
    NotSyncing
}


// The `eth_syncing` method returns either `false` or an instance of the sync info object.
// This doesn't play particularly well with the features exposed by `serde_derive`,
// so we use the custom impls below to ensure proper behavior.

impl<'de> Deserialize<'de> for SyncState {

    fn deserialize<D>(deserializer: D) -> Result<Self,D::Error> where D: Deserializer<'de> {
        let either: Either<SyncInfo,bool> = Deserialize::deserialize(deserializer)?;
        match either {
            Either::A(info) => Ok(SyncState::Syncing(info)),
            Either::B(boolian) => {
                if !boolian {
                    Ok(SyncState::NotSyncing)
                } else {
                    Err(D::Error::custom("expected object or `false`, got `true`"))
                }
            }
        }
    }
}


impl Serialize for SyncState {

    fn serialize<S>(&self, serializer: S) -> Result<S::Ok,S::Error> where S: Serializer {
        match *self {
            SyncState::Syncing(ref info) => info.serialize(serializer),
            SyncState::NotSyncing => false.serialize(serializer)
        }
    }
}


/// implementation detail for sync state deserialization
#[derive(Debug,Serialize,Deserialize)]
#[serde(untagged)]
enum Either<A,B> {
    A(A),
    B(B)
}