Self

pub fn EnumSet(comptime E: type) type {
    return struct {
        const Self = @This();

        /// The indexing rules for converting between keys and indices.
        pub const Indexer = EnumIndexer(E);
        /// The element type for this set.
        pub const Key = Indexer.Key;

        const BitSet = std.bit_set.Static(Indexer.count);

        /// The maximum number of items in this set.
        pub const len = Indexer.count;

        bits: BitSet = .empty,

        /// Initializes the set using a struct of bools
        pub fn init(init_values: EnumFieldStruct(E, bool, false)) Self {
            @setEvalBranchQuota(2 * @typeInfo(E).@"enum".field_names.len);
            var result: Self = .{};
            if (@typeInfo(E).@"enum".mode == .exhaustive) {
                inline for (0..Self.len) |i| {
                    const key = comptime Indexer.keyForIndex(i);
                    const tag = @tagName(key);
                    if (@field(init_values, tag)) {
                        result.bits.set(i);
                    }
                }
            } else {
                inline for (@typeInfo(E).@"enum".field_names) |field_name| {
                    const key = @field(E, field_name);
                    if (@field(init_values, field_name)) {
                        const i = comptime Indexer.indexOf(key);
                        result.bits.set(i);
                    }
                }
            }
            return result;
        }

        /// A set containing no keys.
        pub const empty: Self = .{ .bits = .empty };

        /// A set containing all possible keys.
        pub const full: Self = .{ .bits = .full };

        /// Returns a set containing multiple keys.
        pub fn initMany(keys: []const Key) Self {
            var set: Self = .empty;
            for (keys) |key| set.insert(key);
            return set;
        }

        /// Returns a set containing a single key.
        pub fn initOne(key: Key) Self {
            return initMany(&[_]Key{key});
        }

        /// Returns the number of keys in the set.
        pub fn count(self: Self) usize {
            return self.bits.count();
        }

        /// Checks if a key is in the set.
        pub fn contains(self: Self, key: Key) bool {
            return self.bits.isSet(Indexer.indexOf(key));
        }

        /// Puts a key in the set.
        pub fn insert(self: *Self, key: Key) void {
            self.bits.set(Indexer.indexOf(key));
        }

        /// Removes a key from the set.
        pub fn remove(self: *Self, key: Key) void {
            self.bits.unset(Indexer.indexOf(key));
        }

        /// Changes the presence of a key in the set to match the passed bool.
        pub fn setPresent(self: *Self, key: Key, present: bool) void {
            self.bits.setValue(Indexer.indexOf(key), present);
        }

        /// Toggles the presence of a key in the set.  If the key is in
        /// the set, removes it.  Otherwise adds it.
        pub fn toggle(self: *Self, key: Key) void {
            self.bits.toggle(Indexer.indexOf(key));
        }

        /// Toggles the presence of all keys in the passed set.
        pub fn toggleSet(self: *Self, other: Self) void {
            self.bits.toggleSet(other.bits);
        }

        /// Toggles all possible keys in the set.
        pub fn toggleAll(self: *Self) void {
            self.bits.toggleAll();
        }

        /// Adds all keys in the passed set to this set.
        pub fn setUnion(self: *Self, other: Self) void {
            self.bits.setUnion(other.bits);
        }

        /// Removes all keys which are not in the passed set.
        pub fn setIntersection(self: *Self, other: Self) void {
            self.bits.setIntersection(other.bits);
        }

        /// Returns true iff both sets have the same keys.
        pub fn eql(self: Self, other: Self) bool {
            return self.bits.eql(other.bits);
        }

        /// Returns true iff all the keys in this set are
        /// in the other set. The other set may have keys
        /// not found in this set.
        pub fn subsetOf(self: Self, other: Self) bool {
            return self.bits.subsetOf(other.bits);
        }

        /// Returns true iff this set contains all the keys
        /// in the other set. This set may have keys not
        /// found in the other set.
        pub fn supersetOf(self: Self, other: Self) bool {
            return self.bits.supersetOf(other.bits);
        }

        /// Returns a set with all the keys not in this set.
        pub fn complement(self: Self) Self {
            return .{ .bits = self.bits.complement() };
        }

        /// Returns a set with keys that are in either this
        /// set or the other set.
        pub fn unionWith(self: Self, other: Self) Self {
            return .{ .bits = self.bits.unionWith(other.bits) };
        }

        /// Returns a set with keys that are in both this
        /// set and the other set.
        pub fn intersectWith(self: Self, other: Self) Self {
            return .{ .bits = self.bits.intersectWith(other.bits) };
        }

        /// Returns a set with keys that are in either this
        /// set or the other set, but not both.
        pub fn xorWith(self: Self, other: Self) Self {
            return .{ .bits = self.bits.xorWith(other.bits) };
        }

        /// Returns a set with keys that are in this set
        /// except for keys in the other set.
        pub fn differenceWith(self: Self, other: Self) Self {
            return .{ .bits = self.bits.differenceWith(other.bits) };
        }

        /// Returns an iterator over this set, which iterates in
        /// index order.  Modifications to the set during iteration
        /// may or may not be observed by the iterator, but will
        /// not invalidate it.
        pub fn iterator(self: *const Self) Iterator {
            return .{ .inner = self.bits.iterator(.{}) };
        }

        pub const Iterator = struct {
            inner: BitSet.Iterator(.{}),

            pub fn next(self: *Iterator) ?Key {
                return if (self.inner.next()) |index|
                    Indexer.keyForIndex(index)
                else
                    null;
            }
        };
    };
}