//! Associated data that binds a ciphertext to its location (docs/02 "Envelope format").

use uuid::Uuid;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ObjectType {
    Keyset,
    VaultKey,
    VaultMeta,
    ItemKey,
    Item,
}

impl ObjectType {
    fn tag(self) -> &'static str {
        match self {
            ObjectType::Keyset => "keyset",
            ObjectType::VaultKey => "vault-key",
            ObjectType::VaultMeta => "vault-meta",
            ObjectType::ItemKey => "item-key",
            ObjectType::Item => "item",
        }
    }
}

pub struct Aad;

impl Aad {
    /// `"kestrove/v1/" || type || 0x00 || account || 0x00 || vault || 0x00 || item`.
    /// Absent ids are encoded as the nil UUID so the layout stays fixed.
    pub fn build(ty: ObjectType, account: Uuid, vault: Option<Uuid>, item: Option<Uuid>) -> Vec<u8> {
        let mut out = Vec::with_capacity(12 + 10 + 3 + 48);
        out.extend_from_slice(b"kestrove/v1/");
        out.extend_from_slice(ty.tag().as_bytes());
        for id in [account, vault.unwrap_or(Uuid::nil()), item.unwrap_or(Uuid::nil())] {
            out.push(0);
            out.extend_from_slice(id.as_bytes());
        }
        out
    }
}