From e2cba15ed2ec1681cc455d66a7bb2053cc204f23 Mon Sep 17 00:00:00 2001
From: Benjamin Lee <benjamin@computer.surgery>
Date: Sat, 14 Sep 2024 20:11:29 -0700
Subject: [PATCH] factor out helper for parsing media keys

Leaving this private in `database::key_value::media` because the way
the metadata is encoded in media keys is a mess. I want to fix that in
the future, and want to limit the number of things that rely on it for
now.
---
 src/database/key_value/media.rs | 115 ++++++++++++++++++++++----------
 1 file changed, 78 insertions(+), 37 deletions(-)

diff --git a/src/database/key_value/media.rs b/src/database/key_value/media.rs
index 314cd0a9..1748b360 100644
--- a/src/database/key_value/media.rs
+++ b/src/database/key_value/media.rs
@@ -9,6 +9,82 @@ use crate::{
     utils, Error, Result,
 };
 
+struct MediaFileKeyParts {
+    mxc: OwnedMxcUri,
+    width: u32,
+    height: u32,
+    meta: FileMeta,
+}
+
+impl TryFrom<&MediaFileKey> for MediaFileKeyParts {
+    type Error = Error;
+
+    fn try_from(key: &MediaFileKey) -> Result<MediaFileKeyParts> {
+        let mut parts = key.as_bytes().split(|&b| b == 0xFF);
+
+        let mxc_bytes = parts
+            .next()
+            .ok_or_else(|| Error::bad_database("Media ID in db is invalid."))?;
+        let mxc = utils::string_from_bytes(mxc_bytes)
+            .map_err(|_| {
+                Error::bad_database("Media MXC URI in db is invalid unicode.")
+            })?
+            .into();
+
+        let thumbnail_size_bytes = parts
+            .next()
+            .ok_or_else(|| Error::bad_database("Media ID in db is invalid."))?;
+        let thumbnail_size_bytes: &[u8; 8] =
+            thumbnail_size_bytes.try_into().map_err(|_| {
+                Error::bad_database("Media ID thumbnail size in db is invalid")
+            })?;
+        let width = u32::from_be_bytes(
+            thumbnail_size_bytes[..4].try_into().expect("should be 4 bytes"),
+        );
+        let height = u32::from_be_bytes(
+            thumbnail_size_bytes[4..].try_into().expect("should be 4 bytes"),
+        );
+
+        let content_type = parts
+            .next()
+            .map(|bytes| {
+                utils::string_from_bytes(bytes).map_err(|_| {
+                    Error::bad_database(
+                        "Content type in mediaid_file is invalid unicode.",
+                    )
+                })
+            })
+            .transpose()?;
+
+        let content_disposition_bytes = parts
+            .next()
+            .ok_or_else(|| Error::bad_database("Media ID in db is invalid."))?;
+
+        let content_disposition = if content_disposition_bytes.is_empty() {
+            None
+        } else {
+            Some(utils::string_from_bytes(content_disposition_bytes).map_err(
+                |_| {
+                    Error::bad_database(
+                        "Content Disposition in mediaid_file is invalid \
+                         unicode.",
+                    )
+                },
+            )?)
+        };
+
+        Ok(MediaFileKeyParts {
+            mxc,
+            width,
+            height,
+            meta: FileMeta {
+                content_disposition,
+                content_type,
+            },
+        })
+    }
+}
+
 impl service::media::Data for KeyValueDatabase {
     fn create_file_metadata(
         &self,
@@ -61,42 +137,7 @@ impl service::media::Data for KeyValueDatabase {
             )?;
 
         let key = MediaFileKey::new(key);
-
-        let mut parts = key.as_bytes().rsplit(|&b| b == 0xFF);
-
-        let content_type = parts
-            .next()
-            .map(|bytes| {
-                utils::string_from_bytes(bytes).map_err(|_| {
-                    Error::bad_database(
-                        "Content type in mediaid_file is invalid unicode.",
-                    )
-                })
-            })
-            .transpose()?;
-
-        let content_disposition_bytes = parts
-            .next()
-            .ok_or_else(|| Error::bad_database("Media ID in db is invalid."))?;
-
-        let content_disposition = if content_disposition_bytes.is_empty() {
-            None
-        } else {
-            Some(utils::string_from_bytes(content_disposition_bytes).map_err(
-                |_| {
-                    Error::bad_database(
-                        "Content Disposition in mediaid_file is invalid \
-                         unicode.",
-                    )
-                },
-            )?)
-        };
-        Ok((
-            FileMeta {
-                content_disposition,
-                content_type,
-            },
-            key,
-        ))
+        let parts = MediaFileKeyParts::try_from(&key)?;
+        Ok((parts.meta, key))
     }
 }