Add a FileDataSource that fetches archive files from local disk (#34)

src/file_data.rs

@@ -0,0 +1,63 @@
+use std::fs::File;
+use std::path::{Path, PathBuf};
+
+use serde::Deserialize;
+
+use crate::data::{
+    DataSource, DataSourceInfo, EntryID, SlotMetaTile, SlotTile, SummaryTile, TileID,
+};
+use crate::http::schema::TileRequestRef;
+
+pub struct FileDataSource {
+    pub basedir: PathBuf,
+}
+
+impl FileDataSource {
+    pub fn new(basedir: impl AsRef<Path>) -> Self {
+        Self {
+            basedir: basedir.as_ref().to_owned(),
+        }
+    }
+
+    fn read_file<T>(&self, path: impl AsRef<Path>) -> T
+    where
+        T: for<'a> Deserialize<'a>,
+    {
+        let f = File::open(path).expect("opening file failed");
+        let f = zstd::Decoder::new(f).expect("zstd decompression failed");
+        ciborium::from_reader(f).expect("cbor decoding failed")
+    }
+}
+
+impl DataSource for FileDataSource {
+    fn fetch_info(&self) -> DataSourceInfo {
+        let path = self.basedir.join("info");
+        self.read_file::<DataSourceInfo>(&path)
+    }
+
+    fn fetch_summary_tile(&self, entry_id: &EntryID, tile_id: TileID, _full: bool) -> SummaryTile {
+        let req = TileRequestRef { entry_id, tile_id };
+        let mut path = self.basedir.join("summary_tile");
+        path.push(&req.to_slug());
+        self.read_file::<SummaryTile>(&path)
+    }
+
+    fn fetch_slot_tile(&self, entry_id: &EntryID, tile_id: TileID, _full: bool) -> SlotTile {
+        let req = TileRequestRef { entry_id, tile_id };
+        let mut path = self.basedir.join("slot_tile");
+        path.push(&req.to_slug());
+        self.read_file::<SlotTile>(&path)
+    }
+
+    fn fetch_slot_meta_tile(
+        &self,
+        entry_id: &EntryID,
+        tile_id: TileID,
+        _full: bool,
+    ) -> SlotMetaTile {
+        let req = TileRequestRef { entry_id, tile_id };
+        let mut path = self.basedir.join("slot_meta_tile");
+        path.push(&req.to_slug());
+        self.read_file::<SlotMetaTile>(&path)
+    }
+}

src/lib.rs

@@ -5,6 +5,8 @@ pub mod app;
 pub mod archive_data;
 pub mod data;
 pub mod deferred_data;
+#[cfg(not(target_arch = "wasm32"))]
+pub mod file_data;
 pub mod http;
 #[cfg(not(target_arch = "wasm32"))]
 pub mod parallel_data;