From 77cecebe522d90de010713ffea3f7e5489d0c03d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lukas=20F=C3=BCrderer?= <l.fuerderer@gmail.com>
Date: Wed, 8 May 2019 16:34:55 +0200
Subject: [PATCH] Implement garbage collect on the server

---
 .../texture-sync-server/src/model/sha256.rs   | 32 +++++++-------
 .../src/persistency/mod.rs                    | 44 +++++++++++++++++--
 2 files changed, 57 insertions(+), 19 deletions(-)

diff --git a/server/texture-sync-server/src/model/sha256.rs b/server/texture-sync-server/src/model/sha256.rs
index cbb0181..0aed6ba 100644
--- a/server/texture-sync-server/src/model/sha256.rs
+++ b/server/texture-sync-server/src/model/sha256.rs
@@ -33,6 +33,20 @@ impl Sha256 {
 
         Sha256(hash_arr)
     }
+
+    pub fn from_hex(hex_str: &str) -> Option<Self> {
+        if hex_str.len() != 32 * 2 {
+            return None; // String has wrong length
+        }
+
+        let mut out = [0u8; 32];
+        for (i, byte) in out.iter_mut().enumerate() {
+            let string_index = i * 2;
+            *byte = u8::from_str_radix(&hex_str[string_index..=string_index + 1], 16).ok()?;
+        }
+
+        Some(Sha256(out))
+    }
 }
 
 fn as_hex<S>(hash: &[u8; 32], serializer: S) -> Result<S::Ok, S::Error>
@@ -48,22 +62,10 @@ where
 {
     use serde::de::Error;
 
-    fn hex2bytes(s: &str) -> Option<[u8; 32]> {
-        if s.len() != 32 * 2 {
-            return None; // String has wrong length
-        }
-
-        let mut out = [0u8; 32];
-        for (i, byte) in out.iter_mut().enumerate() {
-            let string_index = i * 2;
-            *byte = u8::from_str_radix(&s[string_index..=string_index + 1], 16).ok()?;
-        }
-
-        return Some(out);
-    }
-
     String::deserialize(deserializer).and_then(|string| {
-        hex2bytes(&string).ok_or_else(|| Error::custom("Invalid HEX String!".to_string()))
+        Ok(Sha256::from_hex(&string)
+            .ok_or_else(|| Error::custom("Invalid HEX String!".to_string()))?
+            .0)
     })
 }
 
diff --git a/server/texture-sync-server/src/persistency/mod.rs b/server/texture-sync-server/src/persistency/mod.rs
index 0fb4b4d..8339025 100644
--- a/server/texture-sync-server/src/persistency/mod.rs
+++ b/server/texture-sync-server/src/persistency/mod.rs
@@ -182,11 +182,47 @@ impl DataStore {
         self.textures.iter()
     }
 
-    pub fn garbage_collect(&mut self) -> io::Result<()> {
-        //unimplemented!()
+    pub fn extract_hash(filename: &std::ffi::OsStr) -> Option<Sha256> {
+        // directly return None for invalidly encoded file names
+        let str_name = filename.to_str()?;
+        let hash = Sha256::from_hex(str_name)?;
 
-        /// VERY TODO:
-        eprintln!("WARNING: We are sorry the GC isn't implemented yet :'( ");
+        // check back to ignore names with lowercase letters
+        if hash.as_hex_string() == str_name {
+            Some(hash)
+        } else {
+            None
+        }
+    }
+
+    pub fn garbage_collect(&mut self) -> io::Result<()> {
+        let texture_dir = std::fs::read_dir(self.texture_base_path())?;
+
+        let mut hashs_on_disk = HashSet::new();
+        for result_direntry in texture_dir {
+            let texture_path = result_direntry?.path();
+            let filename = match texture_path.file_name() {
+                Some(name) => name,
+                None => continue,
+            };
+            match Self::extract_hash(filename) {
+                Some(hash) => {
+                    hashs_on_disk.insert(hash);
+                }
+                None => (), // ignore other files
+            };
+        }
+
+        let mut unused_files = hashs_on_disk;
+        for texture in &self.textures {
+            unused_files.remove(&texture.texture_hash);
+        }
+
+        // remove what is still contained in the HashSet
+        for entry in unused_files {
+            let path = self.texture_file_path(&entry);
+            std::fs::remove_file(path)?;
+        }
         Ok(())
     }
 }