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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

//! Data provider always serving the same struct.

use core::fmt;
use icu_provider::any::MaybeSendSync;
use icu_provider::prelude::*;
use yoke::trait_hack::YokeTraitHack;
use yoke::Yokeable;

/// A data provider that returns clones of a fixed type-erased payload.
///
/// [`FixedProvider`] implements [`AnyProvider`], so it can be used in
/// `*_with_any_provider` constructors across ICU4X.
/// # Examples
///
/// ```
/// use icu_provider::hello_world::*;
/// use icu_provider::prelude::*;
/// use icu_provider_adapters::fixed::FixedProvider;
/// use std::borrow::Cow;
/// use writeable::assert_writeable_eq;
///
/// let provider =
///     FixedProvider::<HelloWorldV1Marker>::from_static(&HelloWorldV1 {
///         message: Cow::Borrowed("custom hello world"),
///     });
///
/// // Check that it works:
/// let formatter = HelloWorldFormatter::try_new_with_any_provider(
///     &provider,
///     Default::default(),
/// )
/// .expect("marker matches");
/// assert_writeable_eq!(formatter.format(), "custom hello world");
///
/// # struct DummyMarker;
/// # impl DynamicDataMarker for DummyMarker {
/// #     type DataStruct = <HelloWorldV1Marker as DynamicDataMarker>::DataStruct;
/// # }
/// # impl DataMarker for DummyMarker {
/// #     const INFO: DataMarkerInfo = DataMarkerInfo::from_path(icu_provider::marker::data_marker_path!("dummy@1"));
/// # }
/// // Requests for invalid markers get MissingDataMarker
/// assert!(matches!(
///     provider.load_any(DummyMarker::INFO, Default::default()),
///     Err(DataError {
///         kind: DataErrorKind::MarkerNotFound,
///         ..
///     })
/// ))
/// ```
#[allow(clippy::exhaustive_structs)] // this type is stable
pub struct FixedProvider<M: DataMarker> {
    data: DataPayload<M>,
}

impl<M: DataMarker> FixedProvider<M> {
    /// Creates a `FixedProvider` with an owned (allocated) payload of the given data.
    pub fn from_owned(data: M::DataStruct) -> Self {
        Self::from_payload(DataPayload::from_owned(data))
    }

    /// Creates a `FixedProvider` with a statically borrowed payload of the given data.
    pub fn from_static(data: &'static M::DataStruct) -> Self {
        FixedProvider {
            data: DataPayload::from_static_ref(data),
        }
    }

    /// Creates a `FixedProvider` from an existing [`DataPayload`].
    pub fn from_payload(data: DataPayload<M>) -> Self {
        FixedProvider { data }
    }

    /// Creates a `FixedProvider` with the default (allocated) version of the data struct.
    pub fn new_default() -> Self
    where
        M::DataStruct: Default,
    {
        Self::from_owned(M::DataStruct::default())
    }
}

impl<M: DataMarker> AnyProvider for FixedProvider<M>
where
    for<'a> YokeTraitHack<<M::DataStruct as Yokeable<'a>>::Output>: Clone,
    M::DataStruct: MaybeSendSync,
{
    fn load_any(&self, marker: DataMarkerInfo, _: DataRequest) -> Result<AnyResponse, DataError> {
        marker.match_marker(M::INFO)?;
        Ok(AnyResponse {
            metadata: DataResponseMetadata::default(),
            payload: self.data.clone().wrap_into_any_payload(),
        })
    }
}

impl<M> DataProvider<M> for FixedProvider<M>
where
    M: DataMarker,
    for<'a> YokeTraitHack<<M::DataStruct as Yokeable<'a>>::Output>: Clone,
{
    fn load(&self, _: DataRequest) -> Result<DataResponse<M>, DataError> {
        Ok(DataResponse {
            metadata: Default::default(),
            payload: self.data.clone(),
        })
    }
}

impl<M> fmt::Debug for FixedProvider<M>
where
    M: DynamicDataMarker,
    M: DataMarker,
    for<'a> &'a <M::DataStruct as Yokeable<'a>>::Output: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.data.fmt(f)
    }
}