courseselectlib/enums/
prerequisite_type.rs

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

#[derive(Debug, PartialEq, Clone, Serialize, Deserialize)]
#[cfg_attr(
    feature = "diesel",
    derive(AsExpression, FromSqlRow),
    sql_type = "Varchar"
)]
pub enum PrerequisiteType {
    Course,
    Subject,
    Certificate,
    Other,
}

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

#[cfg(feature = "diesel")]
impl FromSql<Varchar, Pg> for PrerequisiteType {
    fn from_sql(bytes: Option<&<Pg as Backend>::RawValue>) -> deserialize::Result<Self> {
        match not_none!(bytes) {
            b"Course" => Ok(PrerequisiteType::Course),
            b"Subject" => Ok(PrerequisiteType::Subject),
            b"Certificate" => Ok(PrerequisiteType::Certificate),
            b"Other" => Ok(PrerequisiteType::Other),

            _ => Err("Unrecognized enum variant".into()),
        }
    }
}