4 files changed, 97 insertions, 0 deletions
diff --git a/Cargo.toml b/Cargo.toml
index 66fe450..f04bf9c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,4 +18,7 @@ cursive           = "0.15"
 git = "https://github.com/matthiasbeyer/cursive_tree_view"
 branch = "update-deps"
 
+[dependencies.async-std]
+version          = "1.6"
+features         = ["unstable"]
 
diff --git a/src/mailcache.rs b/src/mailcache.rs
new file mode 100644
index 0000000..1bb8f6f
--- /dev/null
+++ b/src/mailcache.rs
@@ -0,0 +1,88 @@
+use std::path::PathBuf;
+use std::path::Path;
+use std::sync::Arc;
+use std::sync::RwLock;
+use anyhow::Result;
+use anyhow::Error;
+use async_std::sync::{Sender, Receiver};
+use async_std::sync::TryRecvError;
+use async_std::sync::channel;
+use async_std::task;
+
+use crate::mailstore::MailStore;
+
+struct Cache {
+    cache: Vec<MailStore>,
+    receiver: Receiver<Result<MailStore>>,
+}
+
+impl Cache {
+    fn find(&self, path: &Path) -> Option<&MailStore> {
+        self.cache.iter().find(|e| e.path() == path)
+    }
+
+    fn update(&mut self) -> Result<()> {
+        loop {
+            match self.receiver.try_recv() {
+                Ok(queued) => {
+                    self.cache.push(queued?);
+                }
+                Err(TryRecvError::Empty) => break,
+                Err(other) => {
+                    return Err(other).map_err(Error::from)
+                },
+            }
+        }
+
+        Ok(())
+    }
+}
+
+#[derive(Clone)]
+pub struct MailCache {
+    cache: Arc<RwLock<Cache>>,
+    sender: Sender<Result<MailStore>>,
+}
+
+impl MailCache {
+
+    pub fn new(buffer_cap: usize) -> Self {
+        let (s, r) = channel(buffer_cap);
+        MailCache {
+            cache: Arc::new(RwLock::new(Cache {
+                cache: Vec::new(),
+                receiver: r,
+            })),
+            sender: s
+        }
+    }
+
+    pub fn load_background(&self, path: PathBuf) {
+        let sender = self.sender.clone();
+        task::spawn(async move {
+            let mut ms = MailStore::from_path(path);
+            let r = ms.load().map(|_| ms);
+
+            sender.send(r).await
+        });
+    }
+
+    pub fn exec_on<F, T>(&self, path: &Path, f: F) -> Result<T>
+        where T: Sized,
+              F: FnOnce(Option<&MailStore>) -> Result<T>,
+    {
+        self.cache
+            .read()
+            .map_err(|_| anyhow!("RWLock possibly poisened"))
+            .and_then(|cache| f(cache.find(path)))
+    }
+
+    pub fn update_cache(&mut self) -> Result<()> {
+        self.cache
+            .write()
+            .map_err(|_| anyhow!("Possibly poisened RWLock"))
+            .and_then(|mut cache| cache.update())
+    }
+
+}
+
diff --git a/src/mailstore.rs b/src/mailstore.rs
index 3f1d299..cbb59fd 100644
--- a/src/mailstore.rs
+++ b/src/mailstore.rs
@@ -1,4 +1,5 @@
 use std::path::PathBuf;
+use std::path::Path;
 use anyhow::Error;
 use anyhow::Result;
 use maildir::Maildir;
@@ -33,6 +34,10 @@ impl MailStore {
     pub fn cur_mail(&self) -> &Vec<Mail> {
         &self.cur
     }
+
+    pub fn path(&self) -> &Path {
+        self.dir.path()
+    }
 }
 
 pub struct Mail {
diff --git a/src/main.rs b/src/main.rs
index 04f041d..232f834 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,6 +7,7 @@ use mailparse::MailHeaderMap;
 use mailparse::ParsedMail;
 
 mod mailstore;
+mod mailcache;
 mod sidebar;
 mod main_view;