psychologylib/enums/
operation.rs

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use serde::Deserialize;
use serde::Serialize;
use strum_macros::Display;
use strum_macros::EnumString;
#[cfg(feature = "diesel")]
use {
    diesel::backend::Backend,
    diesel::deserialize::FromSql,
    diesel::pg::Pg,
    diesel::serialize::{IsNull, Output, ToSql},
    diesel::types::Varchar,
    diesel::{deserialize, not_none, serialize},
    diesel::{AsExpression, FromSqlRow},
    std::io::Write,
};

#[derive(Debug, Display, EnumString, PartialEq, Clone, Serialize, Deserialize)]
#[cfg_attr(feature = "diesel", derive(AsExpression, FromSqlRow))]
#[cfg_attr(feature = "diesel", sql_type = "Varchar")]
pub enum Operation {
    Minus,
    Plus,
    Multiplication,
}

#[cfg(feature = "diesel")]
impl ToSql<Varchar, Pg> for Operation {
    fn to_sql<W: Write>(&self, out: &mut Output<W, Pg>) -> serialize::Result {
        match *self {
            Operation::Minus => out.write_all(b"Minus")?,
            Operation::Plus => out.write_all(b"Plus")?,
            Operation::Multiplication => out.write_all(b"Multiplication")?,
        }
        Ok(IsNull::No)
    }
}

#[cfg(feature = "diesel")]
impl FromSql<Varchar, Pg> for Operation {
    fn from_sql(bytes: Option<&<Pg as Backend>::RawValue>) -> deserialize::Result<Self> {
        match not_none!(bytes) {
            b"Minus" => Ok(Operation::Minus),
            b"Plus" => Ok(Operation::Plus),
            b"Multiplication" => Ok(Operation::Multiplication),
            _ => Err("Unrecognized enum variant".into()),
        }
    }
}