add conduit compat mode

This makes it possible to deploy Grapevine while using a database
originally created by Conduit, including leaving the admin bot user's
localpart the same as before.

nix/modules/default/default.nix

@@ -45,6 +45,13 @@ in
             '';
             default = "::1";
           };
+          global.conduit_compat = lib.mkOption {
+            type = types.bool;
+            description = ''
+              Whether to operate as a drop-in replacement for Conduit.
+            '';
+            default = false;
+          };
           global.database_path = lib.mkOption {
             type = types.nonEmptyStr;
             readOnly = true;
@@ -54,7 +61,9 @@ in
               Note that this is read-only because this module makes use of
               systemd's `StateDirectory` option.
             '';
-            default = "/var/lib/grapevine";
+            default = if cfg.settings.global.conduit_compat
+              then "/var/lib/matrix-conduit"
+              else "/var/lib/grapevine";
           };
           global.port = lib.mkOption {
             type = types.port;
@@ -104,12 +113,16 @@ in
         RestrictNamespaces = true;
         RestrictRealtime = true;
         StartLimitBurst = 5;
-        StateDirectory = "grapevine";
+        StateDirectory = if cfg.settings.global.conduit_compat
+          then "matrix-conduit"
+          else "grapevine";
         StateDirectoryMode = "0700";
         SystemCallArchitectures = "native";
         SystemCallFilter = [ "@system-service" "~@privileged" ];
         UMask = "077";
-        User = "grapevine";
+        User = if cfg.settings.global.conduit_compat
+          then "conduit"
+          else "grapevine";
       };
     };
   };

src/config.rs

@@ -16,6 +16,8 @@ use self::proxy::ProxyConfig;
 #[allow(clippy::struct_excessive_bools)]
 #[derive(Clone, Debug, Deserialize)]
 pub(crate) struct Config {
+    #[serde(default = "false_fn")]
+    pub(crate) conduit_compat: bool,
     #[serde(default = "default_address")]
     pub(crate) address: IpAddr,
     #[serde(default = "default_port")]

src/database.rs

@@ -176,7 +176,16 @@ impl KeyValueDatabase {
     fn check_db_setup(config: &Config) -> Result<()> {
         let path = Path::new(&config.database_path);
 
-        let sqlite_exists = path.join("grapevine.db").exists();
+        let sqlite_exists = path
+            .join(format!(
+                "{}.db",
+                if config.conduit_compat {
+                    "conduit"
+                } else {
+                    "grapevine"
+                }
+            ))
+            .exists();
         let rocksdb_exists = path.join("IDENTITY").exists();
 
         let mut count = 0;
@@ -401,9 +410,15 @@ impl KeyValueDatabase {
         // Matrix resource ownership is based on the server name; changing it
         // requires recreating the database from scratch.
         if services().users.count()? > 0 {
-            let grapevine_user =
+            let grapevine_user = UserId::parse_with_server_name(
-                UserId::parse_with_server_name("grapevine", services().globals.server_name())
+                if services().globals.config.conduit_compat {
-                    .expect("@grapevine:server_name is valid");
+                    "conduit"
+                } else {
+                    "grapevine"
+                },
+                services().globals.server_name(),
+            )
+            .expect("admin bot username should be valid");
 
             if !services().users.exists(&grapevine_user)? {
                 error!(

src/database/abstraction/sqlite.rs

@@ -97,7 +97,14 @@ impl Engine {
 
 impl KeyValueDatabaseEngine for Arc<Engine> {
     fn open(config: &Config) -> Result<Self> {
-        let path = Path::new(&config.database_path).join("grapevine.db");
+        let path = Path::new(&config.database_path).join(format!(
+            "{}.db",
+            if config.conduit_compat {
+                "conduit"
+            } else {
+                "grapevine"
+            }
+        ));
 
         // calculates cache-size per permanent connection
         // 1. convert MB to KiB

src/service/admin.rs

@@ -212,9 +212,16 @@ impl Service {
         // TODO: Use futures when we have long admin commands
         //let mut futures = FuturesUnordered::new();
 
-        let grapevine_user =
+        let grapevine_user = UserId::parse(format!(
-            UserId::parse(format!("@grapevine:{}", services().globals.server_name()))
+            "@{}:{}",
-                .expect("@grapevine:server_name is valid");
+            if services().globals.config.conduit_compat {
+                "conduit"
+            } else {
+                "grapevine"
+            },
+            services().globals.server_name()
+        ))
+        .expect("admin bot username should be valid");
 
         if let Ok(Some(grapevine_room)) = services().admin.get_admin_room() {
             loop {
@@ -568,7 +575,11 @@ impl Service {
                 if !services().users.exists(&user_id)?
                     || user_id
                         == UserId::parse_with_server_name(
-                            "grapevine",
+                            if services().globals.config.conduit_compat {
+                                "conduit"
+                            } else {
+                                "grapevine"
+                            },
                             services().globals.server_name(),
                         )
                         .expect("grapevine user exists")
@@ -866,9 +877,15 @@ impl Service {
     // Utility to turn clap's `--help` text to HTML.
     fn usage_to_html(text: &str, server_name: &ServerName) -> String {
         // Replace `@grapevine:servername:-subcmdname` with `@grapevine:servername: subcmdname`
+        let localpart = if services().globals.config.conduit_compat {
+            "conduit"
+        } else {
+            "grapevine"
+        };
+
         let text = text.replace(
-            &format!("@grapevine:{server_name}:-"),
+            &format!("@{localpart}:{server_name}:-"),
-            &format!("@grapevine:{server_name}: "),
+            &format!("@{localpart}:{server_name}: "),
         );
 
         // For the grapevine admin room, subcommands become main commands
@@ -952,9 +969,16 @@ impl Service {
         let state_lock = mutex_state.lock().await;
 
         // Create a user for the server
-        let grapevine_user =
+        let grapevine_user = UserId::parse(format!(
-            UserId::parse_with_server_name("grapevine", services().globals.server_name())
+            "@{}:{}",
-                .expect("@grapevine:server_name is valid");
+            if services().globals.config.conduit_compat {
+                "conduit"
+            } else {
+                "grapevine"
+            },
+            services().globals.server_name()
+        ))
+        .expect("admin bot username should be valid");
 
         services().users.create(&grapevine_user, None)?;
 
@@ -1218,9 +1242,15 @@ impl Service {
             let state_lock = mutex_state.lock().await;
 
             // Use the server user to grant the new admin's power level
-            let grapevine_user =
+            let grapevine_user = UserId::parse_with_server_name(
-                UserId::parse_with_server_name("grapevine", services().globals.server_name())
+                if services().globals.config.conduit_compat {
-                    .expect("@grapevine:server_name is valid");
+                    "conduit"
+                } else {
+                    "grapevine"
+                },
+                services().globals.server_name(),
+            )
+            .expect("admin bot username should be valid");
 
             // Invite and join the real user
             services()

src/service/rooms/timeline.rs

@@ -483,7 +483,15 @@ impl Service {
                         .search
                         .index_pdu(shortroomid, &pdu_id, &body)?;
 
-                    let server_user = format!("@grapevine:{}", services().globals.server_name());
+                    let server_user = format!(
+                        "@{}:{}",
+                        if services().globals.config.conduit_compat {
+                            "conduit"
+                        } else {
+                            "grapevine"
+                        },
+                        services().globals.server_name()
+                    );
 
                     let to_grapevine = body.starts_with(&format!("{server_user}: "))
                         || body.starts_with(&format!("{server_user} "))
@@ -822,7 +830,14 @@ impl Service {
                             .filter(|v| v.starts_with('@'))
                             .unwrap_or(sender.as_str());
                         let server_name = services().globals.server_name();
-                        let server_user = format!("@grapevine:{server_name}");
+                        let server_user = format!(
+                            "@{}:{server_name}",
+                            if services().globals.config.conduit_compat {
+                                "conduit"
+                            } else {
+                                "grapevine"
+                            },
+                        );
                         let content = serde_json::from_str::<ExtractMembership>(pdu.content.get())
                             .map_err(|_| Error::bad_database("Invalid content in pdu."))?;