Implement autosave (#851)

1. Pref to Save backup file when user saves manually. Backup
file has extension `.bak`
2. Pref to autosave file every N minutes. When autosaved,
backup files with extensions `.bk1` and `.bk2` are created.
`.bk2` is a copy of the old `.bk1`, and `.bk1` is a copy of the
old file, just before the new version is saved.
3. Note that although the user can force a manual save
even if they have made no edits, an autosave will not
happen if no edits are made.
4. Also, no autosave is done when the currently loaded
file has no name, i.e. has never been saved.
5. Default autosave time period is 5 minutes. User can
choose between 1 and 60 minutes.

Fixes #839

Author: windymilla

src/guiguts/application.py

@@ -476,6 +476,9 @@ def initialize_preferences(self) -> None:
         preferences.set_default(PrefKey.EBOOKMAKER_EPUB3, True)
         preferences.set_default(PrefKey.EBOOKMAKER_KINDLE, False)
         preferences.set_default(PrefKey.EBOOKMAKER_KF8, False)
+        preferences.set_default(PrefKey.BACKUPS_ENABLED, True)
+        preferences.set_default(PrefKey.AUTOSAVE_ENABLED, True)
+        preferences.set_default(PrefKey.AUTOSAVE_INTERVAL, 5)
 
         # Check all preferences have a default
         for pref_key in PrefKey:

src/guiguts/file.py

@@ -119,6 +119,7 @@ def __init__(
         self.page_details = PageDetails()
         self.project_dict = ProjectDict()
         self.mainwindow: Optional[MainWindow] = None
+        self.autosave_id = ""
 
     @property
     def filename(self) -> str:
@@ -276,28 +277,63 @@ def load_file(self, filename: str) -> None:
         self.project_dict.load(filename)
         # Load complete, so set filename (including side effects)
         self.filename = filename
+        self.reset_autosave()
         # After loading, may need to show image
         if preferences.get(PrefKey.AUTO_IMAGE):
             self.image_dir_check()
             self.auto_image_check()
 
-    def save_file(self) -> str:
+    def save_file(self, autosave: bool = False) -> str:
         """Save the current file.
 
+        Args:
+            autosave: True if method was called via autosave
+
         Returns:
-            Current filename or None if save is cancelled
+            Current filename or "" if save is cancelled
         """
-        if self.filename:
-            maintext().do_save(self.filename)
-            self.save_bin(self.filename)
-            return self.filename
-        return self.save_as_file()
+        # If there's no filename, need to do Save As, but if called
+        # via autosave, do nothing
+        if not self.filename:
+            return "" if autosave else self.save_as_file()
+        # If we have a filename, then need to do appropriate backups
+
+        def get_backup_names(ext: str) -> tuple[str, str]:
+            """Get backup names for filename and bin file."""
+            return f"{self.filename}{ext}", f"{bin_name(self.filename)}{ext}"
+
+        binfile_name = bin_name(self.filename)
+        if autosave:
+            # Don't autosave if nothing changed - just reschedule
+            if not maintext().is_modified():
+                self.reset_autosave()
+                return ""
+            backup2_file, backup2_bin = get_backup_names(".bk2")
+            backup1_file, backup1_bin = get_backup_names(".bk1")
+            if os.path.exists(backup1_file):
+                os.replace(backup1_file, backup2_file)
+            if os.path.exists(backup1_bin):
+                os.replace(backup1_bin, backup2_bin)
+            if os.path.exists(self.filename):
+                os.replace(self.filename, backup1_file)
+            if os.path.exists(binfile_name):
+                os.replace(binfile_name, backup1_bin)
+        elif preferences.get(PrefKey.BACKUPS_ENABLED):
+            backup_file, backup_bin = get_backup_names(".bak")
+            if os.path.exists(self.filename):
+                os.replace(self.filename, backup_file)
+            if os.path.exists(binfile_name):
+                os.replace(binfile_name, backup_bin)
+        maintext().do_save(self.filename)
+        self.save_bin(self.filename)
+        self.reset_autosave()
+        return self.filename
 
     def save_as_file(self) -> str:
         """Save current text as new file.
 
         Returns:
-            Chosen filename or None if save is cancelled
+            Chosen filename or "" if save is cancelled
         """
         # If no current extension, or ".txt" extension, set extension to ".html"
         # if it's an HTML file. Similarly for text files, otherwise leave alone.
@@ -384,6 +420,18 @@ def check_save(self) -> bool:
             return False
         return True
 
+    def reset_autosave(self) -> None:
+        """Clear any autosave timer, and start a fresh one if the
+        Preference is turned on."""
+        if self.autosave_id:
+            root().after_cancel(self.autosave_id)
+            self.autosave_id = ""
+        if preferences.get(PrefKey.AUTOSAVE_ENABLED):
+            self.autosave_id = root().after(
+                preferences.get(PrefKey.AUTOSAVE_INTERVAL) * 1000 * 60,
+                lambda: self.save_file(autosave=True),
+            )
+
     def load_bin(self, basename: str) -> bool:
         """Load bin file associated with current file.
 

src/guiguts/misc_dialogs.py

@@ -10,6 +10,7 @@
 
 import regex as re
 
+from guiguts.file import the_file
 from guiguts.maintext import maintext
 from guiguts.mainwindow import ScrolledReadOnlyText
 from guiguts.preferences import (
@@ -304,7 +305,6 @@ def add_label_spinbox(
             PrefKey.TEXT_LINE_SPACING,
             "Additional line spacing in text windows",
         )
-
         add_label_spinbox(
             advance_frame,
             1,
@@ -318,6 +318,33 @@ def add_label_spinbox(
             variable=PersistentBoolean(PrefKey.HIGHLIGHT_CURSOR_LINE),
         ).grid(column=0, row=2, sticky="NEW", pady=5)
 
+        backup_btn = ttk.Checkbutton(
+            advance_frame,
+            text="Keep Backup Before Saving",
+            variable=PersistentBoolean(PrefKey.BACKUPS_ENABLED),
+        )
+        backup_btn.grid(column=0, row=3, sticky="E", pady=(10, 0))
+        ToolTip(backup_btn, "Backup file will have '.bak' extension")
+        ttk.Checkbutton(
+            advance_frame,
+            text="Enable Auto Save Every",
+            variable=PersistentBoolean(PrefKey.AUTOSAVE_ENABLED),
+            command=the_file().reset_autosave,
+        ).grid(column=0, row=4, sticky="E")
+        spinbox = ttk.Spinbox(
+            advance_frame,
+            textvariable=PersistentInt(PrefKey.AUTOSAVE_INTERVAL),
+            from_=1,
+            to=60,
+            width=3,
+        )
+        spinbox.grid(column=1, row=4, sticky="EW", padx=5)
+        ToolTip(
+            spinbox,
+            "Autosave your file (with '.bk1', '.bk2' extensions) after this number of minutes",
+        )
+        ttk.Label(advance_frame, text="Minutes").grid(column=2, row=4, sticky="EW")
+
         notebook.bind(
             "<<NotebookTabChanged>>",
             lambda _: preferences.set(

src/guiguts/preferences.py

@@ -116,6 +116,9 @@ class PrefKey(StrEnum):
     EBOOKMAKER_EPUB3 = auto()
     EBOOKMAKER_KINDLE = auto()
     EBOOKMAKER_KF8 = auto()
+    BACKUPS_ENABLED = auto()
+    AUTOSAVE_ENABLED = auto()
+    AUTOSAVE_INTERVAL = auto()
 
 
 class Preferences: