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

#[derive(Debug, PartialEq, Eq)]
pub enum Flag {
    IgnoreCase,
}

struct FlagVisitor;
impl<'de> Visitor<'de> for FlagVisitor {
    type Value = Flag;

    fn expecting(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "a string containing at least 10 bytes")
    }

    fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        Ok(s.parse::<Flag>().unwrap())
    }
}

impl<'de> Deserialize<'de> for Flag {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        deserializer.deserialize_str(FlagVisitor)
    }
}

impl str::FromStr for Flag {
    type Err = ();
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "ignore case" => Ok(Flag::IgnoreCase),
            _ => Err(()),
        }
    }
}