1 files changed, 83 insertions, 0 deletions
diff --git a/cache/src/key.rs b/cache/src/key.rs
new file mode 100644
index 0000000..d8ca510
--- /dev/null
+++ b/cache/src/key.rs
@@ -0,0 +1,83 @@
+/*
+    This file is part of jellything (https://codeberg.org/metamuffin/jellything)
+    which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
+    Copyright (C) 2025 metamuffin <metamuffin.org>
+*/
+use crate::{CACHE_GENERATION_BUCKET_COUNT, CONF};
+use anyhow::bail;
+use base64::{Engine, prelude::BASE64_URL_SAFE};
+use sha2::Sha256;
+use std::{
+    fmt::Display,
+    hash::{Hash, Hasher},
+    str::FromStr,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct CacheKey(pub [u8; 32]);
+
+impl CacheKey {
+    pub fn new(ty: CacheContentType, seed: impl Hash) -> Self {
+        use sha2::Digest;
+        struct ShaHasher(Sha256);
+        impl Hasher for ShaHasher {
+            fn finish(&self) -> u64 {
+                unreachable!()
+            }
+            fn write(&mut self, bytes: &[u8]) {
+                self.0.update(bytes);
+            }
+        }
+        let mut d = ShaHasher(sha2::Sha256::new());
+        d.0.update(CONF.secret.as_bytes());
+        seed.hash(&mut d);
+        let d = d.0.finalize();
+        let mut key: [u8; 32] = d.as_slice().try_into().unwrap();
+        key[0] = ty as u8;
+        Self(key)
+    }
+    pub fn new_json(seed: impl Hash) -> Self {
+        Self::new(CacheContentType::Json, seed)
+    }
+    pub fn new_image(seed: impl Hash) -> Self {
+        Self::new(CacheContentType::Image, seed)
+    }
+    pub fn content_type(&self) -> CacheContentType {
+        match self.0[0] {
+            1 => CacheContentType::Image,
+            2 => CacheContentType::Json,
+            _ => CacheContentType::Unknown,
+        }
+    }
+    pub(super) fn bucket(&self) -> usize {
+        (self.0[1] as usize
+            | ((self.0[2] as usize) << 8)
+            | ((self.0[3] as usize) << 16)
+            | ((self.0[4] as usize) << 24))
+            % CACHE_GENERATION_BUCKET_COUNT
+    }
+}
+
+impl Display for CacheKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&BASE64_URL_SAFE.encode(self.0))
+    }
+}
+impl FromStr for CacheKey {
+    type Err = anyhow::Error;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut out = [0; 32];
+        let size = BASE64_URL_SAFE.decode_slice(s, &mut out)?;
+        if size != out.len() {
+            bail!("cache key parse invalid size")
+        }
+        Ok(Self(out))
+    }
+}
+
+#[repr(u8)]
+pub enum CacheContentType {
+    Unknown = 0,
+    Image = 1,
+    Json = 2,
+}