//! IDs used for data objects and models.
//!
//! UUID is always unique; the numeric ID used as a fallback
//! is auto-incrementing, but some values may be skipped.
//!
//! It is better to treat both ID implementations as opaque.

#[cfg(feature = "uuid-ids")]
mod impl_uuid {
    /// Common identifier type
    #[allow(non_camel_case_types)]
    pub type ID = uuid::Uuid;

    pub fn next_id() -> ID {
        uuid::Uuid::new_v4()
    }

    pub fn zero_id() -> ID {
        uuid::Uuid::nil()
    }
}

#[cfg(not(feature = "uuid-ids"))]
mod impl_u64 {
    /// Common identifier type
    #[allow(non_camel_case_types)]
    pub type ID = u64;

    lazy_static::lazy_static! {
        static ref COUNTER: parking_lot::Mutex<u64> = parking_lot::Mutex::new(0);
    }

    pub fn next_id() -> ID {
        let mut m = COUNTER.lock();
        let v = *m;
        *m += 1;
        v
    }

    pub fn zero_id() -> ID {
        0
    }
}

#[cfg(feature = "uuid-ids")]
pub use impl_uuid::{ID, next_id, zero_id};
#[cfg(not(feature = "uuid-ids"))]
pub use impl_u64::{ID, next_id, zero_id};

/// Something that has ID
pub trait HaveId {
    fn get_id(&self) -> ID;
}