Here's an idea: Move backends to their own modules

Instead of having a bunch of things in "storage", let's have a
"filesystem" module, with its configuration and backend; let's have a
"joplin" module, with its configuration and backend; and so on.

src/config/config.rs

@@ -27,6 +27,7 @@ use serde_derive::Deserialize;
 use serde_derive::Serialize;
 
 use crate::config::errors::ConfigError;
+use crate::filesystem::config::FilesystemConfig;
 
 /// The last seen favourite
 #[derive(Serialize, Deserialize, Debug)]
@@ -39,6 +40,9 @@ struct Favourite {
 struct AccountConfig {
     favourite: Option<Favourite>,
     mastodon: Data,
+    filesystem: Option<FilesystemConfig>,
+    // joplin: Option<JoplinConfig>,
+    // org: Option<OrgConfig>,
 }
 
 /// The main configuration
@@ -75,6 +79,7 @@ impl Config {
         let account_data = AccountConfig {
             favourite: None,
             mastodon: configuration,
+            filesystem: None,
         };
         self.0.insert(name.into(), account_data);
     }

src/filesystem/config.rs

@@ -0,0 +1,27 @@
+/*
+   DOWNFAV - Download Favourites
+   Copyright (C) 2020  Julio Biason
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+use serde_derive::Deserialize;
+use serde_derive::Serialize;
+
+/// Configuration for the Filesystem backend
+#[derive(Serialize, Deserialize, Debug)]
+pub struct FilesystemConfig {
+    /// Path where files will be stored.
+    pub path: String,
+}

src/filesystem/mod.rs

@@ -0,0 +1,2 @@
+pub mod config;
+pub mod storage;

src/filesystem/storage.rs

@@ -47,7 +47,8 @@ impl Filesystem {
 
     /// Make sure the path structure exists for saving the data.
     fn create_dirs(&self, data: &Data) {
-        std::fs::create_dir_all(self.dir(data)).expect("Failed to create storage directory");
+        std::fs::create_dir_all(self.dir(data))
+            .expect("Failed to create storage directory");
     }
 
     /// Save the content in the directory.

src/main.rs

@@ -21,14 +21,15 @@ use std::io;
 use elefren::helpers::cli;
 use elefren::prelude::*;
 
+use crate::filesystem::storage::Filesystem;
 use crate::storage::data::Data;
-use crate::storage::filesystem::Filesystem;
 use crate::storage::joplin::Joplin;
 use crate::storage::org::Org;
 use crate::storage::storage::Storage;
 
 mod args;
 mod config;
+mod filesystem;
 mod storage;
 
 fn main() {
@@ -46,7 +47,7 @@ fn add_account(name: &str) {
     let mut config = config::config::Config::open().unwrap();
     let connection_info = connect_to_mastodon();
     config.add_account(name, connection_info);
-    config.save();
+    config.save().unwrap();
 }
 
 /// Retrieve favourites

src/storage/mod.rs

@@ -18,7 +18,6 @@
 
 pub mod attachment;
 pub mod data;
-pub mod filesystem;
 pub mod helpers;
 pub mod joplin;
 pub mod org;