//! Declare the [`FallbackState`] type, which is used to store a set of FallbackDir.

use crate::skew::SkewObservation;

use rand::seq::IteratorRandom;

use std::time::{Duration, Instant};

use tor_linkspec::HasRelayIds;

use super::{DirStatus, FallbackDir, FallbackDirBuilder};

use crate::fallback::default_fallbacks;

use crate::{ids::FallbackId, PickGuardError};

use tor_basic_utils::iter::{FilterCount, IteratorExt as _};

use tor_config::define_list_builder_helper;

/// A list of fallback directories.

///

/// Fallback directories (represented by [`FallbackDir`]) are used by Tor

/// clients when they don't already have enough other directory information to

/// contact the network.

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

pub struct FallbackList {

    /// The underlying fallbacks in this set.

    fallbacks: Vec<FallbackDir>,

}

impl<T: IntoIterator<Item = FallbackDir>> From<T> for FallbackList {

}

define_list_builder_helper! {

    // pub because tor-dirmgr needs it for NetworkConfig.fallback_caches

    pub struct FallbackListBuilder {

        pub(crate) fallbacks: [FallbackDirBuilder],

    }

    built: FallbackList = FallbackList { fallbacks };

    default = default_fallbacks();

}

impl FallbackList {

    /// Return the number of fallbacks in this list.

    /// Return true if there are no fallbacks in this list.

    /// Return a random member of this list.

}

/// A set of fallback directories, in usable form.

#[derive(Debug, Clone)]

pub(crate) struct FallbackState {

    /// The list of fallbacks in the set.

    ///

    /// We require that these are sorted and unique by (ED,RSA) keys.

    fallbacks: Vec<Entry>,

}

/// Wrapper type for FallbackDir converted into crate::Guard, and the status

/// information that we store about it.

///

/// Defines a sort order to ensure that we can look up fallback directories by

/// binary search on keys.

#[derive(Debug, Clone)]

pub(super) struct Entry {

    /// The inner fallback directory.

    fallback: FallbackDir,

    /// Whether the directory is currently usable, and if not, when we can retry

    /// it.

    status: DirStatus,

    /// The latest clock skew observation we have from this fallback directory

    /// (if any).

    clock_skew: Option<SkewObservation>,

}

/// Least amount of time we'll wait before retrying a fallback cache.

//

// TODO: we may want to make this configurable to a smaller value for chutney networks.

const FALLBACK_RETRY_FLOOR: Duration = Duration::from_secs(150);

impl From<FallbackDir> for Entry {

}

impl HasRelayIds for Entry {

}

impl From<&FallbackList> for FallbackState {

}

impl FallbackState {

    /// Return a random member of this FallbackSet that's usable at `now`.

    /// Return the next time at which any member of this set will become ready.

    ///

    /// Returns None if no elements are failing.

    /// Return a reference to the entry whose identity is `id`, if there is one.

        }

    /// Return a mutable reference to the entry whose identity is `id`, if there is one.

        }

    /// Return true if this set contains some entry with the given `id`.

    /// Record that a success has occurred for the fallback with the given

    /// identity.

    ///

    /// Be aware that for fallbacks, we only count a successful directory

    /// operation as a success: a circuit success is not enough.

    /// Record that a failure has occurred for the fallback with the given

    /// identity.

    /// Consume `other` and copy all of its fallback status entries into the corresponding entries for `self`.

        use itertools::EitherOrBoth::Both;

    /// Record that a given fallback has told us about clock skew.

    /// Return an iterator over all the clock skew observations we've made for fallback directories

}

#[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_duration_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

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

    use super::*;

    use rand::Rng;

    use tor_basic_utils::test_rng::testing_rng;

    /// Construct a `FallbackDir` with random identity keys and addresses.

    ///

    /// Since there are 416 bits of random id here, the risk of collision is

    /// negligible.

    fn rand_fb<R: Rng>(rng: &mut R) -> FallbackDir {

        let ed: [u8; 32] = rng.gen();

        let rsa: [u8; 20] = rng.gen();

        let ip: u32 = rng.gen();

        let mut bld = FallbackDir::builder();

        bld.ed_identity(ed.into())

            .rsa_identity(rsa.into())

            .orports()

            .push(std::net::SocketAddrV4::new(ip.into(), 9090).into());

        bld.build().unwrap()

    }

    #[test]

    fn construct_fallback_set() {

        use rand::seq::SliceRandom;

        use std::cmp::Ordering as O;

        // fabricate some fallbacks.

        let mut rng = testing_rng();

        let fbs = vec![

            rand_fb(&mut rng),

            rand_fb(&mut rng),

            rand_fb(&mut rng),

            rand_fb(&mut rng),

        ];

        let fb_other = rand_fb(&mut rng);

        let id_other = FallbackId::from_relay_ids(&fb_other);

        // basic case: construct a set

        let list: FallbackList = fbs.clone().into();

        assert!(!list.is_empty());

        assert_eq!(list.len(), 4);

        let mut set: FallbackState = (&list).into();

        // inspect the generated set

        assert_eq!(set.fallbacks.len(), 4);

        assert_eq!(

            set.fallbacks[0].cmp_by_relay_ids(&set.fallbacks[1]),

            O::Less

        );

        assert_eq!(

            set.fallbacks[1].cmp_by_relay_ids(&set.fallbacks[2]),

            O::Less

        );

        assert_eq!(

            set.fallbacks[2].cmp_by_relay_ids(&set.fallbacks[3]),

            O::Less

        );

        // use the constructed set a little.

        for fb in fbs.iter() {

            let id = FallbackId::from_relay_ids(fb);

            assert_eq!(set.get_mut(&id).unwrap().cmp_by_relay_ids(&id), O::Equal);

        }

        assert!(set.get_mut(&id_other).is_none());

        // Now try an input set with duplicates.

        let mut redundant_fbs = fbs.clone();

        redundant_fbs.extend(fbs.clone());

        redundant_fbs.extend(fbs[0..2].iter().map(Clone::clone));

        redundant_fbs[..].shuffle(&mut testing_rng());

        let list2 = redundant_fbs.into();

        assert_ne!(&list, &list2);

        let set2: FallbackState = (&list2).into();

        // It should have the same elements, in the same order.

        assert_eq!(set.fallbacks.len(), set2.fallbacks.len());

        assert!(set

            .fallbacks

            .iter()

            .zip(set2.fallbacks.iter())

            .all(|(ent1, ent2)| ent1.same_relay_ids(ent2)));

    }

    #[test]

    fn set_choose() {

        dbg!("X");

        let mut rng = testing_rng();

        let fbs = vec![

            rand_fb(&mut rng),

            rand_fb(&mut rng),

            rand_fb(&mut rng),

            rand_fb(&mut rng),

        ];

        let list: FallbackList = fbs.into();

        let mut set: FallbackState = (&list).into();

        let filter = crate::GuardFilter::unfiltered();

        let mut counts = [0_usize; 4];

        let now = Instant::now();

        dbg!("A");

        fn lookup_idx(set: &FallbackState, id: &impl HasRelayIds) -> Option<usize> {

            set.fallbacks

                .binary_search_by(|ent| ent.fallback.cmp_by_relay_ids(id))

                .ok()

        }

        // Basic case: everybody is up.

        for _ in 0..100 {

            let fb = set.choose(&mut rng, now, &filter).unwrap();

            let idx = lookup_idx(&set, fb).unwrap();

            counts[idx] += 1;

        }

        dbg!("B");

        assert!(counts.iter().all(|v| *v > 0));

        // Mark somebody down and make sure they don't get chosen.

        let ids: Vec<_> = set

            .fallbacks

            .iter()

            .map(|ent| FallbackId::from_relay_ids(&ent.fallback))

            .collect();

        set.note_failure(&ids[2], now);

        counts = [0; 4];

        for _ in 0..100 {

            let fb = set.choose(&mut rng, now, &filter).unwrap();

            let idx = lookup_idx(&set, fb).unwrap();

            counts[idx] += 1;

        }

        assert_eq!(counts.iter().filter(|v| **v > 0).count(), 3);

        assert_eq!(counts[2], 0);

        // Mark everybody down; make sure we get the right error.

        for id in ids.iter() {

            set.note_failure(id, now);

        }

        assert!(matches!(

            set.choose(&mut rng, now, &filter),

            Err(PickGuardError::AllFallbacksDown { .. })

        ));

        // Construct an empty set; make sure we get the right error.

        let empty_set = FallbackState::from(&FallbackList::from(vec![]));

        assert!(matches!(

            empty_set.choose(&mut rng, now, &filter),

            Err(PickGuardError::NoCandidatesAvailable)

        ));

        // TODO: test restrictions and filters once they're implemented.

    }

    #[test]

    fn test_status() {

        let mut rng = testing_rng();

        let fbs = vec![

            rand_fb(&mut rng),

            rand_fb(&mut rng),

            rand_fb(&mut rng),

            rand_fb(&mut rng),

        ];

        let list: FallbackList = fbs.clone().into();

        let mut set: FallbackState = (&list).into();

        let ids: Vec<_> = set

            .fallbacks

            .iter()

            .map(|ent| FallbackId::from_relay_ids(&ent.fallback))

            .collect();

        let now = Instant::now();

        // There's no "next retry time" when everybody's up.

        assert!(set.next_retry().is_none());

        // Mark somebody down; try accessors.

        set.note_failure(&ids[3], now);

        assert!(set.fallbacks[3].status.next_retriable().unwrap() > now);

        assert!(!set.fallbacks[3].status.usable_at(now));

        assert_eq!(set.next_retry(), set.fallbacks[3].status.next_retriable());

        // Mark somebody else down; try accessors.

        set.note_failure(&ids[0], now);

        assert!(set.fallbacks[0].status.next_retriable().unwrap() > now);

        assert!(!set.fallbacks[0].status.usable_at(now));

        assert_eq!(

            set.next_retry().unwrap(),

            std::cmp::min(

                set.fallbacks[0].status.next_retriable().unwrap(),

                set.fallbacks[3].status.next_retriable().unwrap()

            )

        );

        // Mark somebody as running; try accessors.

        set.note_success(&ids[0]);

        assert!(set.fallbacks[0].status.next_retriable().is_none());

        assert!(set.fallbacks[0].status.usable_at(now));

        // Make a new set with slightly different members; make sure that we can copy stuff successfully.

        let mut fbs2: Vec<_> = fbs

            .into_iter()

            // (Remove the fallback with id==ids[2])

            .filter(|fb| FallbackId::from_relay_ids(fb) != ids[2])

            .collect();

        // add 2 new ones.

        let fbs_new = vec![rand_fb(&mut rng), rand_fb(&mut rng), rand_fb(&mut rng)];

        fbs2.extend(fbs_new.clone());

        let mut set2 = FallbackState::from(&FallbackList::from(fbs2.clone()));

        set2.take_status_from(set); // consumes set.

        assert_eq!(set2.fallbacks.len(), 6); // Started with 4, added 3, removed 1.

        // Make sure that the status entries  are correctly copied.

        assert!(set2.get_mut(&ids[0]).unwrap().status.usable_at(now));

        assert!(set2.get_mut(&ids[1]).unwrap().status.usable_at(now));

        assert!(set2.get_mut(&ids[2]).is_none());

        assert!(!set2.get_mut(&ids[3]).unwrap().status.usable_at(now));

        // Make sure that the new fbs are there.

        for new_fb in fbs_new {

            assert!(set2

                .get_mut(&FallbackId::from_relay_ids(&new_fb))

                .unwrap()

                .status

                .usable_at(now));

        }

    }

}