From c2d40fe56e4f2546c781d366ce4198cba27a166e Mon Sep 17 00:00:00 2001
From: Elias Projahn <johrpan@gmail.com>
Date: Fri, 9 Oct 2020 12:22:02 +0200
Subject: [PATCH] Move database access to background thread

---
 src/backend.rs                     | 349 +++++++++++++++++++++++++++++
 src/dialogs/ensemble_editor.rs     |  27 ++-
 src/dialogs/instrument_editor.rs   |  27 ++-
 src/dialogs/instrument_selector.rs |  72 +++---
 src/dialogs/part_editor.rs         |  11 +-
 src/dialogs/person_editor.rs       |  27 ++-
 src/dialogs/person_selector.rs     |  71 +++---
 src/dialogs/work_editor.rs         |  35 +--
 src/main.rs                        |   1 +
 src/window.rs                      |  70 +++---
 10 files changed, 542 insertions(+), 148 deletions(-)
 create mode 100644 src/backend.rs

diff --git a/src/backend.rs b/src/backend.rs
new file mode 100644
index 0000000..2b14230
--- /dev/null
+++ b/src/backend.rs
@@ -0,0 +1,349 @@
+use super::database::*;
+use glib::Sender;
+
+enum BackendAction {
+    UpdatePerson(Person, Sender<Result<(), String>>),
+    GetPerson(i64, Sender<Option<Person>>),
+    DeletePerson(i64, Sender<Result<(), String>>),
+    GetPersons(Sender<Vec<Person>>),
+    UpdateInstrument(Instrument, Sender<Result<(), String>>),
+    GetInstrument(i64, Sender<Option<Instrument>>),
+    DeleteInstrument(i64, Sender<Result<(), String>>),
+    GetInstruments(Sender<Vec<Instrument>>),
+    UpdateWork(WorkInsertion, Sender<Result<(), String>>),
+    GetWorkDescriptions(i64, Sender<Vec<WorkDescription>>),
+    UpdateEnsemble(Ensemble, Sender<Result<(), String>>),
+    GetEnsemble(i64, Sender<Option<Ensemble>>),
+    DeleteEnsemble(i64, Sender<Result<(), String>>),
+    GetEnsembles(Sender<Vec<Ensemble>>),
+}
+
+use BackendAction::*;
+
+pub struct Backend {
+    action_sender: std::sync::mpsc::Sender<BackendAction>,
+}
+
+impl Backend {
+    pub fn new(url: &str) -> Self {
+        let url = url.to_string();
+
+        let (action_sender, action_receiver) = std::sync::mpsc::channel::<BackendAction>();
+
+        std::thread::spawn(move || {
+            let db = Database::new(&url);
+
+            for action in action_receiver {
+                match action {
+                    UpdatePerson(person, sender) => {
+                        db.update_person(person);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetPerson(id, sender) => {
+                        let person = db.get_person(id);
+                        sender
+                            .send(person)
+                            .expect("Failed to send result from database thread!");
+                    }
+                    DeletePerson(id, sender) => {
+                        db.delete_person(id);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetPersons(sender) => {
+                        let persons = db.get_persons();
+                        sender
+                            .send(persons)
+                            .expect("Failed to send result from database thread!");
+                    }
+                    UpdateInstrument(instrument, sender) => {
+                        db.update_instrument(instrument);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetInstrument(id, sender) => {
+                        let instrument = db.get_instrument(id);
+                        sender
+                            .send(instrument)
+                            .expect("Failed to send result from database thread!");
+                    }
+                    DeleteInstrument(id, sender) => {
+                        db.delete_instrument(id);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetInstruments(sender) => {
+                        let instruments = db.get_instruments();
+                        sender
+                            .send(instruments)
+                            .expect("Failed to send result from database thread!");
+                    }
+                    UpdateWork(work, sender) => {
+                        db.update_work(work);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetWorkDescriptions(id, sender) => {
+                        let works = db.get_work_descriptions(id);
+                        sender
+                            .send(works)
+                            .expect("Failed to send result from database thread!");
+                    }
+                    UpdateEnsemble(ensemble, sender) => {
+                        db.update_ensemble(ensemble);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetEnsemble(id, sender) => {
+                        let ensemble = db.get_ensemble(id);
+                        sender
+                            .send(ensemble)
+                            .expect("Failed to send result from database thread!");
+                    }
+                    DeleteEnsemble(id, sender) => {
+                        db.delete_ensemble(id);
+                        sender
+                            .send(Ok(()))
+                            .expect("Failed to send result from database thread!");
+                    }
+                    GetEnsembles(sender) => {
+                        let ensembles = db.get_ensembles();
+                        sender
+                            .send(ensembles)
+                            .expect("Failed to send result from database thread!");
+                    }
+                }
+            }
+        });
+
+        Backend {
+            action_sender: action_sender,
+        }
+    }
+
+    pub fn update_person<F: Fn(Result<(), String>) -> () + 'static>(
+        &self,
+        person: Person,
+        callback: F,
+    ) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(UpdatePerson(person, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_person<F: Fn(Option<Person>) -> () + 'static>(&self, id: i64, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Option<Person>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetPerson(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn delete_person<F: Fn(Result<(), String>) -> () + 'static>(&self, id: i64, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(DeletePerson(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_persons<F: Fn(Vec<Person>) -> () + 'static>(&self, callback: F) {
+        let (sender, receiver) = glib::MainContext::channel::<Vec<Person>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetPersons(sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn update_instrument<F: Fn(Result<(), String>) -> () + 'static>(
+        &self,
+        instrument: Instrument,
+        callback: F,
+    ) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(UpdateInstrument(instrument, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_instrument<F: Fn(Option<Instrument>) -> () + 'static>(&self, id: i64, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Option<Instrument>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetInstrument(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn delete_instrument<F: Fn(Result<(), String>) -> () + 'static>(
+        &self,
+        id: i64,
+        callback: F,
+    ) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(DeleteInstrument(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_instruments<F: Fn(Vec<Instrument>) -> () + 'static>(&self, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Vec<Instrument>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetInstruments(sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn update_work<F: Fn(Result<(), String>) -> () + 'static>(
+        &self,
+        work: WorkInsertion,
+        callback: F,
+    ) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(UpdateWork(work, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_work_descriptions<F: Fn(Vec<WorkDescription>) -> () + 'static>(
+        &self,
+        id: i64,
+        callback: F,
+    ) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Vec<WorkDescription>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetWorkDescriptions(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn update_ensemble<F: Fn(Result<(), String>) -> () + 'static>(
+        &self,
+        ensemble: Ensemble,
+        callback: F,
+    ) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(UpdateEnsemble(ensemble, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_ensemble<F: Fn(Option<Ensemble>) -> () + 'static>(&self, id: i64, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Option<Ensemble>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetEnsemble(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn delete_ensemble<F: Fn(Result<(), String>) -> () + 'static>(&self, id: i64, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Result<(), String>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(DeleteEnsemble(id, sender))
+            .expect("Failed to send action to database thread!");
+    }
+
+    pub fn get_ensembles<F: Fn(Vec<Ensemble>) -> () + 'static>(&self, callback: F) {
+        let (sender, receiver) =
+            glib::MainContext::channel::<Vec<Ensemble>>(glib::PRIORITY_DEFAULT);
+
+        receiver.attach(None, move |result| {
+            callback(result);
+            glib::Continue(true)
+        });
+
+        self.action_sender
+            .send(GetEnsembles(sender))
+            .expect("Failed to send action to database thread!");
+    }
+}
diff --git a/src/dialogs/ensemble_editor.rs b/src/dialogs/ensemble_editor.rs
index c17c48f..aef8f43 100644
--- a/src/dialogs/ensemble_editor.rs
+++ b/src/dialogs/ensemble_editor.rs
@@ -1,18 +1,26 @@
+use crate::backend::*;
 use crate::database::*;
 use glib::clone;
 use gtk::prelude::*;
 use gtk_macros::get_widget;
 use std::rc::Rc;
 
-pub struct EnsembleEditor {
+pub struct EnsembleEditor<F>
+where
+    F: Fn(Ensemble) -> () + 'static,
+{
     window: gtk::Window,
+    callback: F,
     id: i64,
     name_entry: gtk::Entry,
 }
 
-impl EnsembleEditor {
-    pub fn new<F: Fn(Ensemble) -> () + 'static, P: IsA<gtk::Window>>(
-        db: Rc<Database>,
+impl<F> EnsembleEditor<F>
+where
+    F: Fn(Ensemble) -> () + 'static,
+{
+    pub fn new<P: IsA<gtk::Window>>(
+        backend: Rc<Backend>,
         parent: &P,
         ensemble: Option<Ensemble>,
         callback: F,
@@ -34,8 +42,9 @@ impl EnsembleEditor {
         };
 
         let result = Rc::new(EnsembleEditor {
-            id: id,
             window: window,
+            callback: callback,
+            id: id,
             name_entry: name_entry,
         });
 
@@ -44,15 +53,15 @@ impl EnsembleEditor {
         }));
 
         save_button.connect_clicked(clone!(@strong result => move |_| {
-            result.window.close();
-
             let ensemble = Ensemble {
                 id: result.id,
                 name: result.name_entry.get_text().to_string(),
             };
 
-            db.update_ensemble(ensemble.clone());
-            callback(ensemble);
+            backend.update_ensemble(ensemble.clone(), clone!(@strong result => move |_| {
+                result.window.close();
+                (result.callback)(ensemble.clone());
+            }));
         }));
 
         result.window.set_transient_for(Some(parent));
diff --git a/src/dialogs/instrument_editor.rs b/src/dialogs/instrument_editor.rs
index b9e454b..1174351 100644
--- a/src/dialogs/instrument_editor.rs
+++ b/src/dialogs/instrument_editor.rs
@@ -1,18 +1,26 @@
+use crate::backend::*;
 use crate::database::*;
 use glib::clone;
 use gtk::prelude::*;
 use gtk_macros::get_widget;
 use std::rc::Rc;
 
-pub struct InstrumentEditor {
+pub struct InstrumentEditor<F>
+where
+    F: Fn(Instrument) -> () + 'static,
+{
     window: gtk::Window,
+    callback: F,
     id: i64,
     name_entry: gtk::Entry,
 }
 
-impl InstrumentEditor {
-    pub fn new<F: Fn(Instrument) -> () + 'static, P: IsA<gtk::Window>>(
-        db: Rc<Database>,
+impl<F> InstrumentEditor<F>
+where
+    F: Fn(Instrument) -> () + 'static,
+{
+    pub fn new<P: IsA<gtk::Window>>(
+        backend: Rc<Backend>,
         parent: &P,
         instrument: Option<Instrument>,
         callback: F,
@@ -34,8 +42,9 @@ impl InstrumentEditor {
         };
 
         let result = Rc::new(InstrumentEditor {
-            id: id,
             window: window,
+            callback: callback,
+            id: id,
             name_entry: name_entry,
         });
 
@@ -44,15 +53,15 @@ impl InstrumentEditor {
         }));
 
         save_button.connect_clicked(clone!(@strong result => move |_| {
-            result.window.close();
-
             let instrument = Instrument {
                 id: result.id,
                 name: result.name_entry.get_text().to_string(),
             };
 
-            db.update_instrument(instrument.clone());
-            callback(instrument);
+            backend.update_instrument(instrument.clone(), clone!(@strong result => move |_| {
+                result.window.close();
+                (result.callback)(instrument.clone());
+            }));
         }));
 
         result.window.set_transient_for(Some(parent));
diff --git a/src/dialogs/instrument_selector.rs b/src/dialogs/instrument_selector.rs
index 5023bb1..a94109a 100644
--- a/src/dialogs/instrument_selector.rs
+++ b/src/dialogs/instrument_selector.rs
@@ -1,11 +1,11 @@
 use super::selector_row::SelectorRow;
 use super::InstrumentEditor;
+use crate::backend::Backend;
 use crate::database::*;
 use gio::prelude::*;
 use glib::clone;
 use gtk::prelude::*;
 use gtk_macros::get_widget;
-use std::cell::RefCell;
 use std::convert::TryInto;
 use std::rc::Rc;
 
@@ -13,10 +13,9 @@ pub struct InstrumentSelector<F>
 where
     F: Fn(Instrument) -> () + 'static,
 {
-    db: Rc<Database>,
+    backend: Rc<Backend>,
     window: gtk::Window,
     callback: F,
-    instruments: RefCell<Vec<Instrument>>,
     list: gtk::ListBox,
     search_entry: gtk::SearchEntry,
 }
@@ -25,7 +24,7 @@ impl<F> InstrumentSelector<F>
 where
     F: Fn(Instrument) -> () + 'static,
 {
-    pub fn new<P: IsA<gtk::Window>>(db: Rc<Database>, parent: &P, callback: F) -> Rc<Self> {
+    pub fn new<P: IsA<gtk::Window>>(backend: Rc<Backend>, parent: &P, callback: F) -> Rc<Self> {
         let builder =
             gtk::Builder::from_resource("/de/johrpan/musicus_editor/ui/instrument_selector.ui");
 
@@ -34,47 +33,48 @@ where
         get_widget!(builder, gtk::SearchEntry, search_entry);
         get_widget!(builder, gtk::ListBox, list);
 
-        let instruments = db.get_instruments();
-
-        for (index, instrument) in instruments.iter().enumerate() {
-            let label = gtk::Label::new(Some(&instrument.name));
-            label.set_halign(gtk::Align::Start);
-            let row = SelectorRow::new(index.try_into().unwrap(), &label);
-            row.show_all();
-            list.insert(&row, -1);
-        }
-
         let result = Rc::new(InstrumentSelector {
-            db: db,
+            backend: backend,
             window: window,
             callback: callback,
-            instruments: RefCell::new(instruments),
             search_entry: search_entry,
             list: list,
         });
 
         result
-            .list
-            .connect_row_activated(clone!(@strong result => move |_, row| {
-                result.window.close();
-                let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
-                let index: usize = row.get_index().try_into().unwrap();
-                (result.callback)(result.instruments.borrow()[index].clone());
+            .backend
+            .get_instruments(clone!(@strong result => move |instruments| {
+                for (index, instrument) in instruments.iter().enumerate() {
+                    let label = gtk::Label::new(Some(&instrument.name));
+                    label.set_halign(gtk::Align::Start);
+                    let row = SelectorRow::new(index.try_into().unwrap(), &label);
+                    row.show_all();
+                    result.list.insert(&row, -1);
+                }
+
+                result
+                    .list
+                    .connect_row_activated(clone!(@strong result, @strong instruments => move |_, row| {
+                        result.window.close();
+                        let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
+                        let index: usize = row.get_index().try_into().unwrap();
+                        (result.callback)(instruments[index].clone());
+                    }));
+
+                result
+                    .list
+                    .set_filter_func(Some(Box::new(clone!(@strong result => move |row| {
+                        let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
+                        let index: usize = row.get_index().try_into().unwrap();
+                        let search = result.search_entry.get_text().to_string();
+
+                        search.is_empty() || instruments[index]
+                            .name
+                            .to_lowercase()
+                            .contains(&result.search_entry.get_text().to_string().to_lowercase())
+                    }))));
             }));
 
-        result
-            .list
-            .set_filter_func(Some(Box::new(clone!(@strong result => move |row| {
-                let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
-                let index: usize = row.get_index().try_into().unwrap();
-                let search = result.search_entry.get_text().to_string();
-
-                search.is_empty() || result.instruments.borrow()[index]
-                    .name
-                    .to_lowercase()
-                    .contains(&result.search_entry.get_text().to_string().to_lowercase())
-            }))));
-
         result
             .search_entry
             .connect_search_changed(clone!(@strong result => move |_| {
@@ -83,7 +83,7 @@ where
 
         add_button.connect_clicked(clone!(@strong result => move |_| {
             let editor = InstrumentEditor::new(
-                result.db.clone(),
+                result.backend.clone(),
                 &result.window,
                 None,
                 clone!(@strong result => move |instrument| {
diff --git a/src/dialogs/part_editor.rs b/src/dialogs/part_editor.rs
index a0b0c0a..350d456 100644
--- a/src/dialogs/part_editor.rs
+++ b/src/dialogs/part_editor.rs
@@ -1,5 +1,6 @@
 use super::selector_row::SelectorRow;
 use super::{InstrumentSelector, PersonSelector};
+use crate::backend::*;
 use crate::database::*;
 use glib::clone;
 use gtk::prelude::*;
@@ -9,7 +10,7 @@ use std::convert::TryInto;
 use std::rc::Rc;
 
 pub struct PartEditor {
-    db: Rc<Database>,
+    backend: Rc<Backend>,
     window: gtk::Window,
     title_entry: gtk::Entry,
     composer: RefCell<Option<Person>>,
@@ -20,7 +21,7 @@ pub struct PartEditor {
 
 impl PartEditor {
     pub fn new<F: Fn(WorkPartDescription) -> () + 'static, P: IsA<gtk::Window>>(
-        db: Rc<Database>,
+        backend: Rc<Backend>,
         parent: &P,
         part: Option<WorkPartDescription>,
         callback: F,
@@ -63,7 +64,7 @@ impl PartEditor {
         });
 
         let result = Rc::new(PartEditor {
-            db: db,
+            backend: backend,
             window: window,
             title_entry: title_entry,
             composer: composer,
@@ -86,7 +87,7 @@ impl PartEditor {
         }));
 
         composer_button.connect_clicked(clone!(@strong result => move |_| {
-            PersonSelector::new(result.db.clone(), &result.window, clone!(@strong result => move |person| {
+            PersonSelector::new(result.backend.clone(), &result.window, clone!(@strong result => move |person| {
                 result.composer.replace(Some(person.clone()));
                 result.composer_label.set_text(&person.name_fl());
             })).show();
@@ -98,7 +99,7 @@ impl PartEditor {
         }));
 
         add_instrument_button.connect_clicked(clone!(@strong result => move |_| {
-            InstrumentSelector::new(result.db.clone(), &result.window, clone!(@strong result => move |instrument| {
+            InstrumentSelector::new(result.backend.clone(), &result.window, clone!(@strong result => move |instrument| {
                 {
                     let mut instruments = result.instruments.borrow_mut();
                     instruments.push(instrument);
diff --git a/src/dialogs/person_editor.rs b/src/dialogs/person_editor.rs
index c48bd08..f47cb7a 100644
--- a/src/dialogs/person_editor.rs
+++ b/src/dialogs/person_editor.rs
@@ -1,19 +1,27 @@
+use crate::backend::Backend;
 use crate::database::*;
 use glib::clone;
 use gtk::prelude::*;
 use gtk_macros::get_widget;
 use std::rc::Rc;
 
-pub struct PersonEditor {
+pub struct PersonEditor<F>
+where
+    F: Fn(Person) -> () + 'static,
+{
     window: gtk::Window,
+    callback: F,
     id: i64,
     first_name_entry: gtk::Entry,
     last_name_entry: gtk::Entry,
 }
 
-impl PersonEditor {
-    pub fn new<F: Fn(Person) -> () + 'static, P: IsA<gtk::Window>>(
-        db: Rc<Database>,
+impl<F> PersonEditor<F>
+where
+    F: Fn(Person) -> () + 'static,
+{
+    pub fn new<P: IsA<gtk::Window>>(
+        backend: Rc<Backend>,
         parent: &P,
         person: Option<Person>,
         callback: F,
@@ -36,8 +44,9 @@ impl PersonEditor {
         };
 
         let result = Rc::new(PersonEditor {
-            id: id,
             window: window,
+            callback: callback,
+            id: id,
             first_name_entry: first_name_entry,
             last_name_entry: last_name_entry,
         });
@@ -47,16 +56,16 @@ impl PersonEditor {
         }));
 
         save_button.connect_clicked(clone!(@strong result => move |_| {
-            result.window.close();
-
             let person = Person {
                 id: result.id,
                 first_name: result.first_name_entry.get_text().to_string(),
                 last_name: result.last_name_entry.get_text().to_string(),
             };
 
-            db.update_person(person.clone());
-            callback(person);
+            backend.update_person(person.clone(), clone!(@strong result => move |_| {
+                result.window.close();
+                (result.callback)(person.clone());
+            }));
         }));
 
         result.window.set_transient_for(Some(parent));
diff --git a/src/dialogs/person_selector.rs b/src/dialogs/person_selector.rs
index 234fb36..c095139 100644
--- a/src/dialogs/person_selector.rs
+++ b/src/dialogs/person_selector.rs
@@ -1,11 +1,11 @@
 use super::selector_row::SelectorRow;
 use super::PersonEditor;
+use crate::backend::Backend;
 use crate::database::*;
 use gio::prelude::*;
 use glib::clone;
 use gtk::prelude::*;
 use gtk_macros::get_widget;
-use std::cell::RefCell;
 use std::convert::TryInto;
 use std::rc::Rc;
 
@@ -13,10 +13,9 @@ pub struct PersonSelector<F>
 where
     F: Fn(Person) -> () + 'static,
 {
-    db: Rc<Database>,
+    backend: Rc<Backend>,
     window: gtk::Window,
     callback: F,
-    persons: RefCell<Vec<Person>>,
     list: gtk::ListBox,
     search_entry: gtk::SearchEntry,
 }
@@ -25,7 +24,7 @@ impl<F> PersonSelector<F>
 where
     F: Fn(Person) -> () + 'static,
 {
-    pub fn new<P: IsA<gtk::Window>>(db: Rc<Database>, parent: &P, callback: F) -> Rc<Self> {
+    pub fn new<P: IsA<gtk::Window>>(backend: Rc<Backend>, parent: &P, callback: F) -> Rc<Self> {
         let builder =
             gtk::Builder::from_resource("/de/johrpan/musicus_editor/ui/person_selector.ui");
 
@@ -34,47 +33,47 @@ where
         get_widget!(builder, gtk::SearchEntry, search_entry);
         get_widget!(builder, gtk::ListBox, list);
 
-        let persons = db.get_persons();
-
-        for (index, person) in persons.iter().enumerate() {
-            let label = gtk::Label::new(Some(&person.name_lf()));
-            label.set_halign(gtk::Align::Start);
-            let row = SelectorRow::new(index.try_into().unwrap(), &label);
-            row.show_all();
-            list.insert(&row, -1);
-        }
-
         let result = Rc::new(PersonSelector {
-            db: db,
+            backend: backend,
             window: window,
             callback: callback,
-            persons: RefCell::new(persons),
             search_entry: search_entry,
             list: list,
         });
 
         result
-            .list
-            .connect_row_activated(clone!(@strong result => move |_, row| {
-                result.window.close();
-                let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
-                let index: usize = row.get_index().try_into().unwrap();
-                (result.callback)(result.persons.borrow()[index].clone());
+            .backend
+            .get_persons(clone!(@strong result => move |persons| {
+                for (index, person) in persons.iter().enumerate() {
+                    let label = gtk::Label::new(Some(&person.name_lf()));
+                    label.set_halign(gtk::Align::Start);
+                    let row = SelectorRow::new(index.try_into().unwrap(), &label);
+                    row.show_all();
+                    result.list.insert(&row, -1);
+                }
+
+                result
+                    .list
+                    .connect_row_activated(clone!(@strong result, @strong persons => move |_, row| {
+                        result.window.close();
+                        let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
+                        let index: usize = row.get_index().try_into().unwrap();
+                        (result.callback)(persons[index].clone());
+                    }));
+
+                result
+                    .list
+                    .set_filter_func(Some(Box::new(clone!(@strong result => move |row| {
+                        let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
+                        let index: usize = row.get_index().try_into().unwrap();
+                        let search = result.search_entry.get_text().to_string().to_lowercase();
+                        search.is_empty() || persons[index]
+                            .name_lf()
+                            .to_lowercase()
+                            .contains(&search)
+                    }))));
             }));
 
-        result
-            .list
-            .set_filter_func(Some(Box::new(clone!(@strong result => move |row| {
-                let row = row.get_child().unwrap().downcast::<SelectorRow>().unwrap();
-                let index: usize = row.get_index().try_into().unwrap();
-                let search = result.search_entry.get_text().to_string().to_lowercase();
-
-                search.is_empty() || result.persons.borrow()[index]
-                    .name_lf()
-                    .to_lowercase()
-                    .contains(&search)
-            }))));
-
         result
             .search_entry
             .connect_search_changed(clone!(@strong result => move |_| {
@@ -83,7 +82,7 @@ where
 
         add_button.connect_clicked(clone!(@strong result => move |_| {
             let editor = PersonEditor::new(
-                result.db.clone(),
+                result.backend.clone(),
                 &result.window,
                 None,
                 clone!(@strong result => move |person| {
diff --git a/src/dialogs/work_editor.rs b/src/dialogs/work_editor.rs
index da13924..a42253c 100644
--- a/src/dialogs/work_editor.rs
+++ b/src/dialogs/work_editor.rs
@@ -1,5 +1,6 @@
 use super::selector_row::SelectorRow;
 use super::{InstrumentSelector, PersonSelector, PartEditor, SectionEditor};
+use crate::backend::*;
 use crate::database::*;
 use glib::clone;
 use gtk::prelude::*;
@@ -49,9 +50,12 @@ impl PartOrSection {
     }
 }
 
-pub struct WorkEditor {
-    db: Rc<Database>,
+pub struct WorkEditor<F>
+where
+    F: Fn(WorkDescription) -> () + 'static, {
+    backend: Rc<Backend>,
     window: gtk::Window,
+    callback: F,
     save_button: gtk::Button,
     id: i64,
     title_entry: gtk::Entry,
@@ -63,9 +67,11 @@ pub struct WorkEditor {
     part_list: gtk::ListBox,
 }
 
-impl WorkEditor {
-    pub fn new<F: Fn(WorkDescription) -> () + 'static, P: IsA<gtk::Window>>(
-        db: Rc<Database>,
+impl<F> WorkEditor<F>
+where
+    F: Fn(WorkDescription) -> () + 'static, {
+    pub fn new<P: IsA<gtk::Window>>(
+        backend: Rc<Backend>,
         parent: &P,
         work: Option<WorkDescription>,
         callback: F,
@@ -134,8 +140,9 @@ impl WorkEditor {
         });
 
         let result = Rc::new(WorkEditor {
-            db: db,
+            backend: backend,
             window: window,
+            callback: callback,
             save_button: save_button,
             id: id,
             title_entry: title_entry,
@@ -152,8 +159,6 @@ impl WorkEditor {
         }));
 
         result.save_button.connect_clicked(clone!(@strong result => move |_| {
-            result.window.close();
-
             let mut section_count: i64 = 0;
             let mut parts: Vec<WorkPartDescription> = Vec::new();
             let mut sections: Vec<WorkSectionDescription> = Vec::new();
@@ -179,12 +184,14 @@ impl WorkEditor {
                 sections: sections,
             };
 
-            result.db.update_work(work.clone().into());
-            callback(work);
+            result.backend.update_work(work.clone().into(), clone!(@strong result => move |_| {
+                result.window.close();
+                (result.callback)(work.clone());
+            }));
         }));
 
         composer_button.connect_clicked(clone!(@strong result => move |_| {
-            PersonSelector::new(result.db.clone(), &result.window, clone!(@strong result => move |person| {
+            PersonSelector::new(result.backend.clone(), &result.window, clone!(@strong result => move |person| {
                 result.composer.replace(Some(person.clone()));
                 result.composer_label.set_text(&person.name_fl());
                 result.save_button.set_sensitive(true);
@@ -192,7 +199,7 @@ impl WorkEditor {
         }));
 
         add_instrument_button.connect_clicked(clone!(@strong result => move |_| {
-            InstrumentSelector::new(result.db.clone(), &result.window, clone!(@strong result => move |instrument| {
+            InstrumentSelector::new(result.backend.clone(), &result.window, clone!(@strong result => move |instrument| {
                 {
                     let mut instruments = result.instruments.borrow_mut();
                     instruments.push(instrument);
@@ -216,7 +223,7 @@ impl WorkEditor {
         }));
 
         add_part_button.connect_clicked(clone!(@strong result => move |_| {
-            PartEditor::new(result.db.clone(), &result.window, None, clone!(@strong result => move |part| {
+            PartEditor::new(result.backend.clone(), &result.window, None, clone!(@strong result => move |part| {
                 {
                     let mut structure = result.structure.borrow_mut();
                     structure.push(PartOrSection::part(part));
@@ -247,7 +254,7 @@ impl WorkEditor {
     
                     if pos.is_part() {
                         let editor =
-                            PartEditor::new(result.db.clone(), &result.window, Some(pos.unwrap_part()), clone!(@strong result => move |part| {
+                            PartEditor::new(result.backend.clone(), &result.window, Some(pos.unwrap_part()), clone!(@strong result => move |part| {
                                 result.structure.borrow_mut()[index] = PartOrSection::part(part);
                                 result.show_parts();
                             }));
diff --git a/src/main.rs b/src/main.rs
index 9684259..c0d2711 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,6 +11,7 @@ use glib::clone;
 use std::cell::RefCell;
 use std::rc::Rc;
 
+mod backend;
 mod database;
 mod dialogs;
 
diff --git a/src/window.rs b/src/window.rs
index 91b07e4..b993a36 100644
--- a/src/window.rs
+++ b/src/window.rs
@@ -1,3 +1,4 @@
+use super::backend::Backend;
 use super::database::*;
 use super::dialogs::*;
 use gio::prelude::*;
@@ -12,7 +13,7 @@ use std::rc::Rc;
 
 pub struct Window {
     window: libhandy::ApplicationWindow,
-    db: Rc<Database>,
+    backend: Rc<Backend>,
     leaflet: libhandy::Leaflet,
     persons: RefCell<Vec<Person>>,
     works: RefCell<Vec<WorkDescription>>,
@@ -46,14 +47,13 @@ impl Window {
         get_widget!(builder, gtk::Box, recording_box);
         get_widget!(builder, gtk::ListBox, recording_list);
 
-        let db = Rc::new(Database::new("test.sqlite"));
-        let persons = db.get_persons();
+        let backend = Backend::new("test.sqlite");
 
         let result = Rc::new(Window {
             window: window,
-            db: db,
+            backend: Rc::new(backend),
             leaflet: leaflet,
-            persons: RefCell::new(persons),
+            persons: RefCell::new(Vec::new()),
             works: RefCell::new(Vec::new()),
             recordings: RefCell::new(Vec::new()),
             sidebar_box: sidebar_box,
@@ -108,9 +108,11 @@ impl Window {
             result.window,
             "add-person",
             clone!(@strong result => move |_, _| {
-                PersonEditor::new(result.db.clone(), &result.window, None, clone!(@strong result => move |_| {
-                    result.persons.replace(result.db.get_persons());
-                    result.show_persons();
+                PersonEditor::new(result.backend.clone(), &result.window, None, clone!(@strong result => move |_| {
+                    result.backend.get_persons(clone!(@strong result => move |persons| {
+                        result.persons.replace(persons);
+                        result.show_persons();
+                    }));
                 })).show();
             })
         );
@@ -119,7 +121,7 @@ impl Window {
             result.window,
             "add-instrument",
             clone!(@strong result => move |_, _| {
-                InstrumentEditor::new(result.db.clone(), &result.window, None, |instrument| {
+                InstrumentEditor::new(result.backend.clone(), &result.window, None, |instrument| {
                     println!("{:?}", instrument);
                 }).show();
             })
@@ -129,9 +131,11 @@ impl Window {
             result.window,
             "add-work",
             clone!(@strong result => move |_, _| {
-                WorkEditor::new(result.db.clone(), &result.window, None, clone!(@strong result => move |_| {
-                    result.persons.replace(result.db.get_persons());
-                    result.show_persons();
+                WorkEditor::new(result.backend.clone(), &result.window, None, clone!(@strong result => move |_| {
+                    result.backend.get_persons(clone!(@strong result => move |persons| {
+                        result.persons.replace(persons);
+                        result.show_persons();
+                    }));
                 })).show();
             })
         );
@@ -140,7 +144,7 @@ impl Window {
             result.window,
             "add-ensemble",
             clone!(@strong result => move |_, _| {
-                EnsembleEditor::new(result.db.clone(), &result.window, None, |ensemble| {
+                EnsembleEditor::new(result.backend.clone(), &result.window, None, |ensemble| {
                     println!("{:?}", ensemble);
                 }).show();
             })
@@ -155,12 +159,15 @@ impl Window {
             "edit-person",
             Some(glib::VariantTy::new("x").unwrap()),
             clone!(@strong result => move |_, id| {
-                let person = result.db.get_person(id.unwrap().get().unwrap()).unwrap();
-                PersonEditor::new(result.db.clone(), &result.window, Some(person), clone!(@strong result => move |person| {
-                    result.persons.replace(result.db.get_persons());
-                    result.show_persons();
-                    result.show_person(person);
-                })).show();
+                result.backend.get_person(id.unwrap().get().unwrap(), clone!(@strong result => move |person| {
+                    let person = person.unwrap();
+                    PersonEditor::new(result.backend.clone(), &result.window, Some(person), clone!(@strong result => move |person| {
+                        result.backend.get_persons(clone!(@strong result => move |persons| {
+                            result.persons.replace(persons);
+                            result.show_persons();
+                        }));
+                    })).show();
+                }));
             })
         );
 
@@ -169,10 +176,13 @@ impl Window {
             "delete-person",
             Some(glib::VariantTy::new("x").unwrap()),
             clone!(@strong result => move |_, id| {
-                result.db.delete_person(id.unwrap().get().unwrap());
-                result.back();
-                result.persons.replace(result.db.get_persons());
-                result.show_persons();
+                result.backend.delete_person(id.unwrap().get().unwrap(), clone!(@strong result => move |_| {
+                    result.back();
+                    result.backend.get_persons(clone!(@strong result => move |persons| {
+                        result.persons.replace(persons);
+                        result.show_persons();
+                    }));
+                }));
             })
         );
 
@@ -218,13 +228,13 @@ impl Window {
 
         self.header_menu_button.set_menu_model(Some(&menu));
 
-        self.works.replace(self.db.get_work_descriptions(person.id));
-        self.show_works();
-
-        self.show_recordings();
-
-        self.stack.set_visible_child_name("person_screen");
-        self.leaflet.set_visible_child(&self.stack);
+        // let result = self.clone();
+        // self.backend.get_work_descriptions(person.id, |works| {
+        //     result.show_works();
+        //     result.show_recordings();
+        //     result.stack.set_visible_child_name("person_screen");
+        //     result.leaflet.set_visible_child(&result.stack);
+        // });
     }
 
     fn show_works(&self) {