Add Gravatar support.

src/routes/users/get_default_avatar.rs

@@ -0,0 +1,29 @@
+use rocket::response::NamedFile;
+use std::path::Path;
+
+use crate::database::Ref;
+
+#[get("/<target>/default_avatar")]
+pub async fn req(target: Ref) -> Option<NamedFile> {
+    match target.id.chars().nth(25).unwrap() {
+        '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' => {
+            NamedFile::open(Path::new("assets/user_red.png")).await.ok()
+        }
+        '8' | '9' | 'A' | 'C' | 'B' | 'D' | 'E' | 'F' => {
+            NamedFile::open(Path::new("assets/user_green.png"))
+                .await
+                .ok()
+        }
+        'G' | 'H' | 'J' | 'K' | 'M' | 'N' | 'P' | 'Q' => {
+            NamedFile::open(Path::new("assets/user_blue.png"))
+                .await
+                .ok()
+        }
+        'R' | 'S' | 'T' | 'V' | 'W' | 'X' | 'Y' | 'Z' => {
+            NamedFile::open(Path::new("assets/user_yellow.png"))
+                .await
+                .ok()
+        }
+        _ => unreachable!(),
+    }
+}