Adjust middleware to modify responses

2 files changed, 73 insertions, 13 deletions

diff --git a/src/middleware/find_mailboxes_compatibility.rs b/src/middleware/find_mailboxes_compatibility.rs
index 6a9b341..a1ddda2 100644
--- a/src/middleware/find_mailboxes_compatibility.rs
+++ b/src/middleware/find_mailboxes_compatibility.rs
@@ -1,16 +1,68 @@
 use log::debug;
 
-/// `MailDrop` can't find folders to sync because it sends FIND MAILBOXES /*
+use super::Middleware;
+
+/// `MailDrop` can't find folders to sync because it implements IMAPv3 and
+/// sends FIND MAILBOXES /*, which does not exist in IMAPv4.
 /// which is not understood by modern servers. It instead replaces it with
 /// a LIST command.
-pub fn middleware(input: &[u8]) -> Vec<u8> {
-    let command = String::from_utf8_lossy(input);
-    if command.contains("FIND MAILBOXES /*") {
-        if let Some(tag) = command.split("FIND MAILBOXES /*").next() {
-            let replacement = format!("{} LIST \"\" \"*\"\r\n", tag.trim());
-            debug!("### {replacement}");
-            return replacement.into_bytes();
+pub struct FindMailboxesCompatibility {
+    tags: Vec<String>,
+}
+
+impl FindMailboxesCompatibility {
+    pub fn new() -> Self {
+        FindMailboxesCompatibility { tags: vec![] }
+    }
+}
+
+impl Middleware for FindMailboxesCompatibility {
+    fn client_message(&mut self, input: &[u8]) -> Vec<u8> {
+        let command = String::from_utf8_lossy(input);
+        if command.contains("FIND MAILBOXES /*") {
+            if let Some(tag) = command.split("FIND MAILBOXES /*").next() {
+                // We'll need to convert the LIST to a FIND
+                self.tags.push(tag.to_string());
+                let replacement = format!("{} LIST \"\" \"*\"\r\n", tag.trim());
+                debug!("### {replacement}");
+                return replacement.into_bytes();
+            }
+        }
+        input.to_vec()
+    }
+
+    fn server_message(&mut self, input: &[u8]) -> Vec<u8> {
+        let command = String::from_utf8_lossy(input);
+        let contains_ok_completed = self
+            .tags
+            .iter()
+            .any(|tag| command.contains(&format!("{} OK Completed", tag)));
+
+        // We want to only modify responses that were a result of a MAILBOX call.
+        if !contains_ok_completed {
+            return input.to_vec();
         }
+
+        let lines: Vec<String> = command
+            .lines()
+            .filter_map(|line| {
+                // The IMAPv3 spec specifically says INBOX is excluded from MAILBOX
+                if line.starts_with("* LIST") && line.trim_end().ends_with("\"/\" INBOX") {
+                    return None;
+                }
+
+                // Transform IMAPv4 "* LIST" lines to IMAPv3 "* MAILBOX"
+                if line.starts_with("* LIST") {
+                    if let Some(last_slash_pos) = line.rfind('/') {
+                        let mailbox_name = line[(last_slash_pos + 1)..].trim();
+                        return Some(format!("* MAILBOX {}\r", mailbox_name));
+                    }
+                }
+
+                return Some(line.to_string());
+            })
+            .collect();
+
+        return lines.join("\n").into_bytes();
     }
-    input.to_vec()
 }
diff --git a/src/middleware/mod.rs b/src/middleware/mod.rs
index da7e64a..b9685bf 100644
--- a/src/middleware/mod.rs
+++ b/src/middleware/mod.rs
@@ -1,8 +1,16 @@
 mod find_mailboxes_compatibility;
 
-use find_mailboxes_compatibility::middleware as find_mailboxes_compatibility_middleware;
+use find_mailboxes_compatibility::FindMailboxesCompatibility;
 
-type Middleware = fn(&[u8]) -> Vec<u8>;
+use std::sync::{Arc, Mutex};
 
-pub const CLIENT_MIDDLEWARE: [Middleware; 1] = [find_mailboxes_compatibility_middleware];
-pub const SERVER_MIDDLEWARE: [Middleware; 0] = [];
+pub trait Middleware: Sync + Send {
+    fn client_message(&mut self, input: &[u8]) -> Vec<u8>;
+    fn server_message(&mut self, input: &[u8]) -> Vec<u8>;
+}
+
+pub fn get_middleware() -> Arc<Mutex<Vec<Box<dyn Middleware>>>> {
+    Arc::new(Mutex::new(vec![
+        Box::new(FindMailboxesCompatibility::new()),
+    ]))
+}