feat: add image fetching

src/server/caches/mime.rs

@@ -0,0 +1,68 @@
+//! Mime mmagic analogous to [`magic::Cookie`] BUT [`Sync`]
+
+// I don't think I can do better with thread exclusive `libmagic`
+
+use std::cell::OnceCell;
+
+use magic::{Cookie, cookie};
+
+#[derive(Debug, thiserror::Error)]
+pub enum NewCookieError {
+    #[error(transparent)]
+    MimeCookieOpen(#[from] magic::cookie::OpenError),
+    #[error(transparent)]
+    MimeDBLoad(#[from] magic::cookie::LoadError<magic::cookie::Open>),
+    // #[error(transparent)]
+    // MimeDBPath(#[from] magic::cookie::InvalidDatabasePathError),
+}
+
+pub struct Mime {
+    magic_dbs: magic::cookie::DatabasePaths,
+}
+
+impl Mime {
+    thread_local! {
+        static COOKIE_CELL: OnceCell<Cookie<cookie::Load>> = const { OnceCell::new() };
+    }
+
+    fn use_cookie<F, T>(&self, f: F) -> Result<T, NewCookieError>
+    where
+        F: FnOnce(&Cookie<cookie::Load>) -> T,
+    {
+        Self::COOKIE_CELL.with(|cookie| {
+            let may_cookie = cookie.get_or_try_init::<_, NewCookieError>(move || {
+                let cookie = magic::Cookie::open(magic::cookie::Flags::MIME)?;
+                Ok(cookie.load(&self.magic_dbs)?)
+            });
+
+            match may_cookie {
+                Ok(c) => Ok(f(c)),
+                Err(e) => Err(e),
+            }
+        })
+    }
+
+    #[must_use]
+    pub const fn new(magic_dbs: magic::cookie::DatabasePaths) -> Self {
+        Self { magic_dbs }
+    }
+
+    /// Cookie initialization is delayed, so each call might be the creation of the cookie if its
+    /// the first use of the cookie in this thread.
+    ///
+    /// # Errors
+    ///
+    /// First layer error fails if new cookie creation failed. Second layer error represents if the
+    /// mime search was successful.
+    pub fn buffer(
+        &self,
+        buffer: &[u8],
+    ) -> Result<Result<String, magic::cookie::Error>, NewCookieError> {
+        self.use_cookie(|c| c.buffer(buffer))
+    }
+}
+
+// fn __ace(c: Mime) {
+//     fn __ace_inner(c: impl Sync + Send) {}
+//     __ace_inner(c);
+// }