theme: persist across app close

Signed-off-by: kernelkind <kernelkind@gmail.com>

crates/notedeck_columns/src/theme_handler.rs

@@ -0,0 +1,76 @@
+use egui::ThemePreference;
+use tracing::{error, info};
+
+use crate::storage::{write_file, DataPath, DataPathType, Directory};
+
+pub struct ThemeHandler {
+    directory: Directory,
+    fallback_theme: ThemePreference,
+}
+
+const THEME_FILE: &str = "theme.txt";
+
+impl ThemeHandler {
+    pub fn new(path: &DataPath) -> Self {
+        let directory = Directory::new(path.path(DataPathType::Setting));
+        let fallback_theme = ThemePreference::Light;
+        Self {
+            directory,
+            fallback_theme,
+        }
+    }
+
+    pub fn load(&self) -> ThemePreference {
+        match self.directory.get_file(THEME_FILE.to_owned()) {
+            Ok(contents) => match deserialize_theme(contents) {
+                Some(theme) => theme,
+                None => {
+                    error!(
+                        "Could not deserialize theme. Using fallback {:?} instead",
+                        self.fallback_theme
+                    );
+                    self.fallback_theme
+                }
+            },
+            Err(e) => {
+                error!(
+                    "Could not read {} file: {:?}\nUsing fallback {:?} instead",
+                    THEME_FILE, e, self.fallback_theme
+                );
+                self.fallback_theme
+            }
+        }
+    }
+
+    pub fn save(&self, theme: ThemePreference) {
+        match write_file(
+            &self.directory.file_path,
+            THEME_FILE.to_owned(),
+            &theme_to_serialized(&theme),
+        ) {
+            Ok(_) => info!(
+                "Successfully saved {:?} theme change to {}",
+                theme, THEME_FILE
+            ),
+            Err(_) => error!("Could not save {:?} theme change to {}", theme, THEME_FILE),
+        }
+    }
+}
+
+fn theme_to_serialized(theme: &ThemePreference) -> String {
+    match theme {
+        ThemePreference::Dark => "dark",
+        ThemePreference::Light => "light",
+        ThemePreference::System => "system",
+    }
+    .to_owned()
+}
+
+fn deserialize_theme(serialized_theme: String) -> Option<ThemePreference> {
+    match serialized_theme.as_str() {
+        "dark" => Some(ThemePreference::Dark),
+        "light" => Some(ThemePreference::Light),
+        "system" => Some(ThemePreference::System),
+        _ => None,
+    }
+}