//! Manager-global identifiers, for things that need to be identified outside

//! the scope of a single RPC connection.

//!

//! We expect to use this code to identify `TorClient`s and similar objects that

//! can be passed as the target of a SOCKS request.  Since the SOCKS request is

//! not part of the RPC session, we need a way for it to refer to these objects.

use rand::RngExt;

use tor_bytes::Reader;

use tor_llcrypto::util::ct::CtByteArray;

use tor_rpcbase::{LookupError, ObjectId};

use zeroize::Zeroizing;

use crate::{connection::ConnectionId, objmap::GenIdx};

/// A [RpcMgr](crate::RpcMgr)-scoped identifier for an RPC object.

///

/// A `GlobalId` identifies an RPC object uniquely among all the objects visible

/// to any active session on an RpcMgr.

///

/// Its encoding is unforgeable.

#[derive(Clone, Debug, Eq, PartialEq)]

pub(crate) struct GlobalId {

    /// The RPC connection within whose object map `local_id` is visible.

    pub(crate) connection: ConnectionId,

    /// The identifier of the object within `connection`'s object map.

    pub(crate) local_id: GenIdx,

}

/// The number of bytes in our [`MacKey`].

///

/// (Our choice of algorithm allows any key length we want; 128 bits should be

/// secure enough.)

const MAC_KEY_LEN: usize = 16;

/// The number of bytes in a [`Mac`].

///

/// (Our choice of algorithm allows any MAC length we want; 128 bits should be

/// enough to make the results unforgeable.)

const MAC_LEN: usize = 16;

/// An key that we use to compute message authentication codes (MACs) for our

/// [`GlobalId`]s

///

/// We do not guarantee any particular MAC algorithm; we should be able to

/// change MAC algorithms without breaking any user code. Right now, we choose a

/// Kangaroo12-based construction in order to be reasonably fast.

#[derive(Clone)]

pub(crate) struct MacKey {

    /// The key itself.

    key: Zeroizing<[u8; MAC_KEY_LEN]>,

}

/// A message authentication code produced by [`MacKey::mac`].

type Mac = CtByteArray<MAC_LEN>;

impl MacKey {

    /// Construct a new random `MacKey`.

    /// Compute the AMC of a given input `inp`, and store the result into `out`.

    ///

    /// The current construction allows `out` to be any length.

        use tiny_keccak::{Hasher as _, Kmac};

}

impl GlobalId {

    /// The number of bytes used to encode a `GlobalId` in binary form.

    const ENCODED_LEN: usize = MAC_LEN + ConnectionId::LEN + GenIdx::BYTE_LEN;

    /// A prefix we use when encoding global IDs in base64.

    ///

    /// Since this isn't a valid base 64 character, we can't confuse it with

    /// a base64 string.

    const TAG_CHAR: char = '$';

    /// Create a new GlobalId from its parts.

    /// Encode this ID in an unforgeable string that we can later use to

    /// uniquely identify an RPC object.

    ///

    /// As with local IDs, this encoding is nondeterministic.

        use base64ct::{Base64Unpadded as B64, Encoding};

    /// As `encode`, but do not base64-encode the result.

    /// Try to decode and validate `s` as a [`GlobalId`].

    ///

    /// Returns `Ok(None)` if `s` is not tagged as an identifier for a `GlobalId`.

        use base64ct::{Base64Unpadded as B64, Encoding};

    /// As `try_decode`, but expect a byte slice rather than a base64-encoded string.

        // TODO RPC: Just use Reader here?

}

#[cfg(test)]

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use super::*;

    const GLOBAL_ID_B64_ENCODED_LEN: usize = (GlobalId::ENCODED_LEN * 8).div_ceil(6) + 1;

    #[test]

    fn roundtrip() {

        use slotmap_careful::KeyData;

        let mut rng = tor_basic_utils::test_rng::testing_rng();

        let conn1 = ConnectionId::from(*b"example1-------!");

        let genidx_s1 = GenIdx::from(KeyData::from_ffi(0x43_0000_0043));

        let gid1 = GlobalId {

            connection: conn1,

            local_id: genidx_s1,

        };

        let mac_key = MacKey::new(&mut rng);

        let enc1 = gid1.encode(&mac_key);

        let gid1_decoded = GlobalId::try_decode(&mac_key, &enc1).unwrap().unwrap();

        assert_eq!(gid1, gid1_decoded);

        assert!(enc1.as_ref().starts_with(GlobalId::TAG_CHAR));

        assert_eq!(enc1.as_ref().len(), GLOBAL_ID_B64_ENCODED_LEN);

    }

    #[test]

    fn not_a_global_id() {

        let mut rng = tor_basic_utils::test_rng::testing_rng();

        let mac_key = MacKey::new(&mut rng);

        let decoded = GlobalId::try_decode(&mac_key, &ObjectId::from("helloworld"));

        assert!(matches!(decoded, Ok(None)));

        let decoded = GlobalId::try_decode(&mac_key, &ObjectId::from("$helloworld"));

        assert!(matches!(decoded, Err(LookupError::NoObject(_))));

    }

    #[test]

    fn mac_works() {

        use slotmap_careful::KeyData;

        let mut rng = tor_basic_utils::test_rng::testing_rng();

        let conn1 = ConnectionId::from(*b"example1-------!");

        let conn2 = ConnectionId::from(*b"example2-------!");

        let genidx_s1 = GenIdx::from(KeyData::from_ffi(0x43_0000_0043));

        let genidx_s2 = GenIdx::from(KeyData::from_ffi(0x171_0000_0171));

        let gid1 = GlobalId {

            connection: conn1,

            local_id: genidx_s1,

        };

        let gid2 = GlobalId {

            connection: conn2,

            local_id: genidx_s2,

        };

        let mac_key = MacKey::new(&mut rng);

        let enc1 = gid1.encode_as_bytes(&mac_key, &mut rng);

        let enc2 = gid2.encode_as_bytes(&mac_key, &mut rng);

        // Make a 'combined' encoded gid with the mac from one and the info from

        // the other.

        let mut combined = Vec::from(&enc1[0..MAC_LEN]);

        combined.extend_from_slice(&enc2[MAC_LEN..]);

        let outcome = GlobalId::try_decode_from_bytes(&mac_key, &combined[..]);

        // Can't decode, because MAC was wrong.

        assert!(outcome.is_none());

    }

}