From 5d44766a45664f949bc9ae7f44cd38f2e411d0be Mon Sep 17 00:00:00 2001
From: Josh Megnauth <jo.sh@tutanota.com>
Date: Tue, 8 Oct 2024 01:30:04 -0400
Subject: [PATCH] feat: Short circuiting check for empty trash

`is_empty()` is a short circuiting function that checks if the trash is
empty on Freedesktop compatible systems and Windows.

The main purpose of `is_empty()` is to avoid evaluating the entire trash
context when the caller is only interested in whether the trash is empty
or not. This is especially useful for full trashes with many items.
---
 src/freedesktop.rs | 26 ++++++++++++++++++++++++++
 src/lib.rs         | 18 ++++++++++++++++++
 src/windows.rs     | 15 +++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/src/freedesktop.rs b/src/freedesktop.rs
index 9db12fa..625c8e4 100644
--- a/src/freedesktop.rs
+++ b/src/freedesktop.rs
@@ -197,6 +197,32 @@ pub fn list() -> Result<Vec<TrashItem>, Error> {
     Ok(result)
 }
 
+pub fn is_empty() -> Result<bool, Error> {
+    let trash_folders = trash_folders()?;
+
+    if trash_folders.is_empty() {
+        return Ok(true);
+    }
+
+    for folder in trash_folders {
+        // We're only concerned if the trash contains any files
+        // Therefore, we only need to check if the bin itself is empty
+        let bin = folder.join("files");
+        match bin.read_dir() {
+            Ok(mut entries) => {
+                if let Some(Ok(_)) = entries.next() {
+                    return Ok(false);
+                }
+            }
+            Err(e) => {
+                warn!("The trash files folder {:?} could not be read. Error was {:?}", bin, e);
+            }
+        }
+    }
+
+    Ok(true)
+}
+
 pub fn trash_folders() -> Result<HashSet<PathBuf>, Error> {
     let EvaluatedTrashFolders { trash_folders, home_error, .. } = eval_trash_folders()?;
 
diff --git a/src/lib.rs b/src/lib.rs
index cf624cc..0fd60b0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -374,6 +374,24 @@ pub mod os_limited {
         platform::list()
     }
 
+    /// Returns whether the trash is empty or has at least one item.
+    ///
+    /// Unlike calling [`list`], this function short circuits without evaluating every item.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use trash::os_limited::is_empty;
+    /// if is_empty().unwrap_or(true) {
+    ///     println!("Trash is empty");
+    /// } else {
+    ///     println!("Trash contains at least one item");
+    /// }
+    /// ```
+    pub fn is_empty() -> Result<bool, Error> {
+        platform::is_empty()
+    }
+
     /// Returns all valid trash bins on supported Unix platforms.
     ///
     /// Valid trash folders include the user's personal "home trash" as well as designated trash
diff --git a/src/windows.rs b/src/windows.rs
index 52aebaf..2d5e729 100644
--- a/src/windows.rs
+++ b/src/windows.rs
@@ -126,6 +126,21 @@ pub fn list() -> Result<Vec<TrashItem>, Error> {
     }
 }
 
+pub fn is_empty() -> Result<bool, Error> {
+    ensure_com_initialized();
+    unsafe {
+        let recycle_bin: IShellItem =
+            SHGetKnownFolderItem(&FOLDERID_RecycleBinFolder, KF_FLAG_DEFAULT, Handle::default())?;
+        let pesi: IEnumShellItems = recycle_bin.BindToHandler(None, &BHID_EnumItems)?;
+
+        let mut count = 0u32;
+        let mut items = [None];
+        pesi.Next(&mut items, Some(&mut count as *mut u32))?;
+
+        Ok(count == 0)
+    }
+}
+
 pub fn metadata(item: &TrashItem) -> Result<TrashItemMetadata, Error> {
     ensure_com_initialized();
     let id_as_wide = to_wide_path(&item.id);