From d35534c0795caeda46e57fc515b74eba701110a2 Mon Sep 17 00:00:00 2001
From: Daniel Schadt <kingdread@gmx.de>
Date: Fri, 6 Dec 2019 18:00:04 +0100
Subject: initial commit

---
 src/cache.rs | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 src/cache.rs

(limited to 'src/cache.rs')

diff --git a/src/cache.rs b/src/cache.rs
new file mode 100644
index 0000000..f64b45a
--- /dev/null
+++ b/src/cache.rs
@@ -0,0 +1,78 @@
+//! Caching support to prevent hitting the API a lot.
+use std::fs::File;
+use std::io::prelude::*;
+use std::path::Path;
+
+use xdg::BaseDirectories;
+
+use super::APP_NAME;
+
+quick_error! {
+    #[derive(Debug)]
+    pub enum CacheError {
+        Io(err: std::io::Error) {
+            cause(err)
+            from()
+        }
+    }
+}
+
+/// A generic cache.
+pub trait Cache {
+    fn store(&mut self, path: &Path, data: &[u8]) -> Result<(), CacheError>;
+    fn get(&mut self, path: &Path) -> Result<Option<Vec<u8>>, CacheError>;
+}
+
+/// A cache that stores files in the XDG specified cache location.
+pub struct FileCache {
+    dirs: BaseDirectories,
+}
+
+impl FileCache {
+    /// Create a new file backed cache.
+    pub fn new() -> Self {
+        let dirs = BaseDirectories::with_prefix(APP_NAME).unwrap();
+        FileCache { dirs }
+    }
+}
+
+impl Cache for FileCache {
+    fn store(&mut self, path: &Path, data: &[u8]) -> Result<(), CacheError> {
+        let cache_path = self.dirs.place_cache_file(path).unwrap();
+        let mut f = File::create(cache_path)?;
+        f.write_all(data)?;
+        Ok(())
+    }
+
+    fn get(&mut self, path: &Path) -> Result<Option<Vec<u8>>, CacheError> {
+        let cache_path = self.dirs.find_cache_file(path);
+        match cache_path {
+            Some(p) => {
+                let mut f = File::open(p)?;
+                let mut buffer = Vec::new();
+                f.read_to_end(&mut buffer)?;
+                Ok(Some(buffer))
+            }
+            None => Ok(None),
+        }
+    }
+}
+
+/// A cache that does nothing.
+struct NoopCache;
+
+impl NoopCache {
+    pub fn new() -> Self {
+        NoopCache
+    }
+}
+
+impl Cache for NoopCache {
+    fn store(&mut self, _path: &Path, _data: &[u8]) -> Result<(), CacheError> {
+        Ok(())
+    }
+
+    fn get(&mut self, _path: &Path) -> Result<Option<Vec<u8>>, CacheError> {
+        Ok(None)
+    }
+}
-- 
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