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// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum 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.

// OpenEthereum 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 OpenEthereum.  If not, 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
    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)]);
    }
}