refactor: backup non-cosmic gtk css files

cosmic-theme/src/output/gtk4_output.rs

@@ -2,8 +2,9 @@ use crate::{composite::over, steps::steps, Component, Theme};
 use palette::{rgb::Rgba, Darken, IntoColor, Lighten, Srgba};
 use std::{
     fs::{self, File},
-    io::Write,
+    io::{self, Write},
     num::NonZeroUsize,
+    path::Path,
 };
 
 use super::{to_rgba, OutputError};
@@ -77,7 +78,7 @@ impl Theme {
         inverted_bg_divider.alpha = 0.5;
         let scrollbar_outline = to_rgba(inverted_bg_divider);
 
-        let mut css = format! {r#"
+        let mut css = format! {r#"/* GENERATED BY COSMIC */
 @define-color window_bg_color {window_bg};
 @define-color window_fg_color {window_fg};
 
@@ -169,6 +170,10 @@ impl Theme {
     }
 
     /// Apply gtk color variable settings
+    ///
+    /// # Errors
+    ///
+    /// Returns an `OutputError` if there is an error applying the CSS file.
     pub fn apply_gtk(is_dark: bool) -> Result<(), OutputError> {
         let Some(config_dir) = dirs::config_dir() else {
             return Err(OutputError::MissingConfigDir);
@@ -180,31 +185,22 @@ impl Theme {
         fs::create_dir_all(&gtk4).map_err(OutputError::Io)?;
         fs::create_dir_all(&gtk3).map_err(OutputError::Io)?;
 
-        let cosmic_css = gtk4
-            .join("cosmic")
-            .join(if is_dark { "dark.css" } else { "light.css" });
+        let cosmic_css_dir = gtk4.join("cosmic");
+        let cosmic_css =
+            cosmic_css_dir
+                .clone()
+                .join(if is_dark { "dark.css" } else { "light.css" });
 
         let gtk4_dest = gtk4.join("gtk.css");
         let gtk3_dest = gtk3.join("gtk.css");
 
         #[cfg(target_family = "unix")]
         for gtk_dest in [&gtk4_dest, &gtk3_dest] {
-            use std::fs::metadata;
             use std::os::unix::fs::symlink;
-
-            let mut gtk_dest_bak = gtk_dest.clone();
-            gtk_dest_bak.set_extension("css.bak");
+            Self::backup_non_cosmic_css(gtk_dest, &cosmic_css_dir).map_err(OutputError::Io)?;
 
             if gtk_dest.exists() {
-                if metadata(&gtk_dest)
-                    .map_err(OutputError::Io)?
-                    .file_type()
-                    .is_symlink()
-                {
-                    fs::remove_file(&gtk_dest).map_err(OutputError::Io)?;
-                } else {
-                    fs::rename(&gtk_dest, gtk_dest_bak).map_err(OutputError::Io)?;
-                }
+                fs::remove_file(gtk_dest).map_err(OutputError::Io)?;
             }
 
             symlink(&cosmic_css, gtk_dest).map_err(OutputError::Io)?;
@@ -213,6 +209,10 @@ impl Theme {
     }
 
     /// Reset the applied gtk css
+    ///
+    /// # Errors
+    ///
+    /// Returns an `OutputError` if there is an error resetting the CSS file.
     pub fn reset_gtk() -> Result<(), OutputError> {
         let Some(config_dir) = dirs::config_dir() else {
             return Err(OutputError::MissingConfigDir);
@@ -221,11 +221,47 @@ impl Theme {
         let gtk4 = config_dir.join("gtk-4.0");
         let gtk3 = config_dir.join("gtk-3.0");
         let gtk4_dest = gtk4.join("gtk.css");
+        let cosmic_css = gtk4.join("cosmic");
         let gtk3_dest = gtk3.join("gtk.css");
 
-        let res = fs::remove_file(gtk3_dest);
-        fs::remove_file(gtk4_dest).map_err(OutputError::Io)?;
-        Ok(res.map_err(OutputError::Io)?)
+        let res = Self::reset_cosmic_css(&gtk3_dest, &cosmic_css).map_err(OutputError::Io);
+        Self::reset_cosmic_css(&gtk4_dest, &cosmic_css).map_err(OutputError::Io)?;
+        res
+    }
+
+    fn backup_non_cosmic_css(path: &Path, cosmic_css: &Path) -> io::Result<()> {
+        if !Self::is_cosmic_css(path, cosmic_css)?.unwrap_or(true) {
+            let backup_path = path.with_extension("css.bak");
+            fs::rename(path, &backup_path)?;
+        }
+        Ok(())
+    }
+
+    fn reset_cosmic_css(path: &Path, cosmic_css: &Path) -> io::Result<()> {
+        if Self::is_cosmic_css(path, cosmic_css)?.unwrap_or_default() {
+            fs::remove_file(path)?;
+        }
+        Ok(())
+    }
+
+    fn is_cosmic_css(path: &Path, cosmic_css: &Path) -> io::Result<Option<bool>> {
+        if !path.exists() {
+            return Ok(None);
+        }
+
+        if let Ok(metadata) = fs::symlink_metadata(path) {
+            if metadata.file_type().is_symlink() {
+                if let Ok(actual_cosmic_css) = fs::read_link(path) {
+                    let canonical_target = fs::canonicalize(&actual_cosmic_css)?;
+                    let canonical_base = fs::canonicalize(cosmic_css)?;
+                    return Ok(Some(
+                        canonical_target == canonical_base
+                            || canonical_target.starts_with(&canonical_base),
+                    ));
+                }
+            }
+        }
+        Ok(Some(false))
     }
 }