Indicate when file has changed on disk

src/file_editor.rs

@@ -1,30 +1,77 @@
 use std::{
     cmp::Ordering,
     fmt::{self, Display},
+    fs::{self, File},
+    io::Write,
     ops::{Div as _, Sub as _},
     path::{Path, PathBuf},
     str::FromStr,
+    sync::mpsc,
 };
 
+use chrono::{DateTime, Local};
 use egui::{
-    Align, Button, DragAndDrop, Frame, Layout, ScrollArea, Ui, UiBuilder, Vec2, Widget as _, vec2,
+    Align, Button, Context, DragAndDrop, Frame, Layout, ScrollArea, Ui, UiBuilder, Vec2,
+    Widget as _, vec2,
 };
+use eyre::eyre;
+use notify::{EventKind, Watcher};
 
 use crate::{
+    app::Jobs,
     custom_code_block::{MdItem, iter_lines_and_code_blocks},
     handwriting::{self, Handwriting, HandwritingStyle},
     preferences::Preferences,
     text_editor::MdTextEdit,
+    util::{file_mtime, log_error},
 };
 
 #[derive(serde::Deserialize, serde::Serialize)]
 pub struct FileEditor {
     title: String,
-    pub path: Option<PathBuf>,
+
+    path: Option<PathBuf>,
     pub buffer: Vec<BufferItem>,
 
-    /// Whether the file has been edited since it was laste saved to disk.
-    pub is_dirty: bool,
+    pub file_mtime: Option<DateTime<Local>>,
+    pub buffer_mtime: DateTime<Local>,
+
+    // TODO: instantiate these on load
+    #[serde(skip)]
+    inner: Option<Inner>,
+
+    /// Whether the file has been edited since it was last saved to disk.
+    is_dirty: bool,
+}
+
+struct Inner {
+    file_events: mpsc::Receiver<FileEvent>,
+    file_events_tx: mpsc::Sender<FileEvent>,
+    _file_watcher: notify::RecommendedWatcher,
+}
+
+#[derive(Debug)]
+pub enum SaveStatus {
+    /// The contents of the buffer is the same as on disk.
+    Synced,
+
+    /// The contents exits only in memory and has never been saved to disk.
+    NoFile,
+
+    /// The buffer has been edited but not saved to disk.
+    FileOutdated,
+
+    /// The contents on disk has changes that are newer than the buffer.
+    BufferOutdated,
+
+    /// The contents on disk and in the buffer has diverged.
+    Desynced,
+}
+
+#[derive(Debug)]
+enum FileEvent {
+    NewFileMTime(DateTime<Local>),
+    NewBufferMTime(DateTime<Local>),
 }
 
 #[derive(serde::Deserialize, serde::Serialize)]
@@ -40,18 +87,24 @@ impl FileEditor {
             title: title.into(),
             path: None,
             buffer,
+            file_mtime: None,
+            buffer_mtime: Local::now(),
             is_dirty: false,
+            inner: None,
         }
     }
 
-    pub fn from_file(file_path: PathBuf, contents: &str) -> Self {
+    pub fn from_file(file_path: PathBuf, contents: &str, mtime: DateTime<Local>) -> Self {
         let file_title = file_path
             .file_name()
             .map(|name| name.to_string_lossy().to_string())
             .unwrap_or_else(|| String::from("untitled.md"));
+
         Self {
             title: file_title,
             path: Some(file_path),
+            file_mtime: Some(mtime),
+            buffer_mtime: mtime,
             ..FileEditor::from(contents)
         }
     }
@@ -64,7 +117,46 @@ impl FileEditor {
         self.path.as_deref()
     }
 
+    pub fn save_status(&self) -> SaveStatus {
+        let Some(file_mtime) = self.file_mtime else {
+            return SaveStatus::NoFile;
+        };
+
+        let buffer_is_newer = self.buffer_mtime > file_mtime;
+        let file_is_newer = self.buffer_mtime < file_mtime;
+
+        if buffer_is_newer || (file_is_newer && self.is_dirty) {
+            SaveStatus::Desynced
+        } else if file_is_newer {
+            SaveStatus::BufferOutdated
+        } else if self.is_dirty {
+            SaveStatus::FileOutdated
+        } else {
+            SaveStatus::Synced
+        }
+    }
+
     pub fn show(&mut self, ui: &mut Ui, preferences: &Preferences) {
+        if let Some(path) = &self.path
+            && self.inner.is_none()
+        {
+            self.inner = Some(spawn_file_watcher(path));
+        }
+
+        if let Some(inner) = &mut self.inner {
+            while let Ok(event) = inner.file_events.try_recv() {
+                match dbg!(event) {
+                    FileEvent::NewFileMTime(mtime) => {
+                        self.file_mtime = Some(mtime);
+                    }
+                    FileEvent::NewBufferMTime(mtime) => {
+                        self.buffer_mtime = mtime;
+                        self.file_mtime = Some(mtime);
+                    }
+                }
+            }
+        }
+
         ui.vertical_centered_justified(|ui| {
             ui.heading(&self.title);
 
@@ -243,6 +335,38 @@ impl FileEditor {
         self.title = title.to_string_lossy().to_string();
         self.path = Some(new_path);
     }
+
+    pub fn set_dirty(&mut self, value: bool) {
+        self.is_dirty = value;
+    }
+
+    pub fn save(&mut self, ctx: &Context, jobs: &mut Jobs) {
+        let Some(file_path) = self.path.clone() else {
+            log::info!("Can't save {}, no path set.", self.title);
+            return;
+        };
+
+        self.is_dirty = false;
+        let text = self.to_string();
+        let inner = self
+            .inner
+            .get_or_insert_with(|| spawn_file_watcher(&file_path));
+        let file_event_tx = inner.file_events_tx.clone();
+
+        jobs.start(ctx, move || {
+            log_error(eyre!("Failed to save file {file_path:?}"), || {
+                let mut file = fs::File::create(file_path)?;
+                file.write_all(text.as_bytes())?;
+                let mtime = file_mtime(&file)?;
+
+                let _ = file_event_tx.send(FileEvent::NewBufferMTime(mtime));
+
+                Ok(())
+            });
+
+            None
+        });
+    }
 }
 
 impl Display for BufferItem {
@@ -314,6 +438,40 @@ impl From<&str> for FileEditor {
     }
 }
 
+fn spawn_file_watcher(p: &Path) -> Inner {
+    let (tx, rx) = mpsc::channel();
+
+    let path = p.to_owned();
+    let events_tx = tx.clone();
+    let mut watcher = notify::recommended_watcher(move |event: notify::Result<notify::Event>| {
+        log_error(eyre!("watch {path:?} error"), || {
+            match event?.kind {
+                EventKind::Create(..) | EventKind::Modify(..) | EventKind::Remove(..) => {}
+
+                EventKind::Access(..) | EventKind::Any | EventKind::Other => return Ok(()),
+            }
+
+            let file = File::open(&path)?;
+            let mtime = file_mtime(&file)?;
+
+            let _ = events_tx.send(FileEvent::NewFileMTime(mtime.into()));
+
+            Ok(())
+        });
+    })
+    .unwrap();
+
+    if let Err(e) = watcher.watch(p, notify::RecursiveMode::NonRecursive) {
+        log::error!("Failed to watch {p:?}: {e}");
+    };
+
+    Inner {
+        file_events: rx,
+        file_events_tx: tx,
+        _file_watcher: watcher,
+    }
+}
+
 #[cfg(test)]
 mod test {