pub fn from_schema<S: Schema + ?Sized>() -> Result<Self, Error> {

        let mut schematic = Self {

            name: S::schema_name(),

            contained_collections: HashSet::new(),

            collections_by_type_id: HashMap::new(),

            collection_encryption_keys: HashMap::new(),

            views: HashMap::new(),

            views_by_name: HashMap::new(),

            views_by_collection: HashMap::new(),

            unique_views_by_collection: HashMap::new(),

        };

        S::define_collections(&mut schematic)?;

        Ok(schematic)

    }

    pub fn define_collection<C: Collection + 'static>(&mut self) -> Result<(), Error> {

        let name = C::collection_name();

        if self.contained_collections.contains(&name) {

            self.collections_by_type_id

                .insert(TypeId::of::<C>(), name.clone());

            if let Some(key) = C::encryption_key() {

                self.collection_encryption_keys.insert(name.clone(), key);

            }

            self.contained_collections.insert(name);

            C::define_views(self)

    }

    pub fn define_view<V: ViewSchema<View = V> + SerializedView + Clone + 'static>(

        &mut self,

        view: V,

    ) -> Result<(), Error> {

        self.define_view_with_schema(view.clone(), view)

    }

    pub fn define_view_with_schema<

        V: SerializedView + 'static,

        S: ViewSchema<View = V> + 'static,

    >(

        &mut self,

        view: V,

        schema: S,

    ) -> Result<(), Error> {

        let instance = ViewInstance { view, schema };

        let name = instance.view_name();

        let collection = instance.collection();

        let unique = instance.unique();

        self.views.insert(TypeId::of::<V>(), Box::new(instance));

        // TODO check for name collision

        self.views_by_name.insert(name, TypeId::of::<V>());

        if unique {

            let unique_views = self

                .unique_views_by_collection

                .entry(collection.clone())

                .or_insert_with(Vec::new);

            unique_views.push(TypeId::of::<V>());

        }

        let views = self

            .views_by_collection

            .entry(collection)

            .or_insert_with(Vec::new);

        views.push(TypeId::of::<V>());

        Ok(())

    }

    pub fn contains_collection_id(&self, collection: &CollectionName) -> bool {

        self.contained_collections.contains(collection)

    }

    pub fn view_by_name(&self, name: &ViewName) -> Option<&'_ dyn view::Serialized> {

        self.views_by_name

            .get(name)

            .and_then(|type_id| self.views.get(type_id))

            .map(AsRef::as_ref)

    }

    pub fn view<V: View + 'static>(&self) -> Option<&'_ dyn view::Serialized> {

        self.views.get(&TypeId::of::<V>()).map(AsRef::as_ref)

    }

    pub fn views(&self) -> impl Iterator<Item = &'_ dyn view::Serialized> {

        self.views.values().map(AsRef::as_ref)

    }

    pub fn views_in_collection(

        &self,

        collection: &CollectionName,

    ) -> Option<Vec<&'_ dyn view::Serialized>> {

        self.views_by_collection.get(collection).map(|view_ids| {

            view_ids

                .iter()

                .filter_map(|id| self.views.get(id).map(AsRef::as_ref))

                .collect()

        })

    }

    pub fn unique_views_in_collection(

        &self,

        collection: &CollectionName,

    ) -> Option<Vec<&'_ dyn view::Serialized>> {

        self.unique_views_by_collection

            .get(collection)

            .map(|view_ids| {

                view_ids

                    .iter()

                    .filter_map(|id| self.views.get(id).map(AsRef::as_ref))

                    .collect()

            })

    }

    pub fn encryption_key_for_collection(&self, collection: &CollectionName) -> Option<&KeyId> {

        self.collection_encryption_keys.get(collection)

    }

    pub fn collections(&self) -> Vec<CollectionName> {

        self.contained_collections.iter().cloned().collect()

    }

    fn collection(&self) -> CollectionName {

        <<V as View>::Collection as Collection>::collection_name()

    }

    fn unique(&self) -> bool {

        self.schema.unique()

    }

    fn version(&self) -> u64 {

        self.schema.version()

    }

    fn view_name(&self) -> ViewName {

        self.view.view_name()

    }

    fn map(&self, document: &BorrowedDocument<'_>) -> Result<Vec<map::Serialized>, view::Error> {

        let map = self.schema.map(document)?;

        map.into_iter()

            .map(|map| map.serialized::<V>())

            .collect::<Result<Vec<_>, view::Error>>()

    }

    fn reduce(&self, mappings: &[(&[u8], &[u8])], rereduce: bool) -> Result<Vec<u8>, view::Error> {

        let mappings = mappings

            .iter()

            .map(

                |(key, value)| match <V::Key as Key>::from_big_endian_bytes(key) {

                    Ok(key) => {

                        let value = V::deserialize(value)?;

                        Ok(MappedValue::new(key, value))

                },

            )

            .collect::<Result<Vec<_>, view::Error>>()?;

        let reduced_value = self.schema.reduce(&mappings, rereduce)?;

        V::serialize(&reduced_value).map_err(view::Error::from)

    }

#[test]

fn schema_tests() -> anyhow::Result<()> {

    let schema = Schematic::from_schema::<Basic>()?;

    assert_eq!(schema.collections_by_type_id.len(), 1);

    assert_eq!(

        schema.collections_by_type_id[&TypeId::of::<Basic>()],

        Basic::collection_name()

    );

    assert_eq!(schema.views.len(), 4);

    assert_eq!(

        schema.views[&TypeId::of::<BasicCount>()].view_name(),

        View::view_name(&BasicCount)

    );

    Ok(())

}