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// Copyright 2019 Conflux Foundation. All rights reserved.
// Conflux is free software and distributed under GNU General Public License.
// See http://www.gnu.org/licenses/

use serde::{
    de::{Error, Visitor},
    Deserialize, Deserializer,
};
use std::fmt;

/// Represents usize.
#[derive(Debug, PartialEq)]
pub struct Index(usize);

impl Index {
    /// Convert to usize
    #[allow(dead_code)]
    pub fn value(&self) -> usize { self.0 }
}

impl<'a> Deserialize<'a> for Index {
    fn deserialize<D>(deserializer: D) -> Result<Index, D::Error>
    where D: Deserializer<'a> {
        deserializer.deserialize_any(IndexVisitor)
    }
}

struct IndexVisitor;

impl<'a> Visitor<'a> for IndexVisitor {
    type Value = Index;

    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        write!(formatter, "a hex-encoded or decimal index")
    }

    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
    where E: Error {
        match value {
            _ if value.starts_with("0x") => {
                usize::from_str_radix(&value[2..], 16)
                    .map(Index)
                    .map_err(|e| Error::custom(format!("Invalid index: {}", e)))
            }
            _ => value
                .parse::<usize>()
                .map(Index)
                .map_err(|e| Error::custom(format!("Invalid index: {}", e))),
        }
    }

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

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

    #[test]
    fn block_number_deserialization() {
        let s = r#"["0xa", "10"]"#;
        let deserialized: Vec<Index> = serde_json::from_str(s).unwrap();
        assert_eq!(deserialized, vec![Index(10), Index(10)]);
    }
}