Implement settings persistence with save/load functions and tests

src/persistence.rs

@@ -0,0 +1,61 @@
+use crate::theme::Settings;
+use std::path::Path;
+
+const SETTINGS_FILE: &str = "settings.json";
+
+pub fn settings_dir() -> std::path::PathBuf {
+    if let Ok(exe) = std::env::current_exe() {
+        if let Some(dir) = exe.parent() {
+            return dir.to_path_buf();
+        }
+    }
+    std::path::PathBuf::from(".")
+}
+
+pub fn save_settings(dir: &Path, settings: &Settings) -> Result<(), String> {
+    let path = dir.join(SETTINGS_FILE);
+    let json = serde_json::to_string_pretty(settings)
+        .map_err(|e| format!("序列化设置失败: {}", e))?;
+    std::fs::write(&path, json)
+        .map_err(|e| format!("保存设置失败: {}", e))?;
+    Ok(())
+}
+
+pub fn load_settings(dir: &Path) -> Result<Settings, String> {
+    let path = dir.join(SETTINGS_FILE);
+    let json = std::fs::read_to_string(&path)
+        .map_err(|e| format!("读取设置失败: {}", e))?;
+    serde_json::from_str(&json)
+        .map_err(|e| format!("解析设置失败: {}", e))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::theme::{Settings, Theme};
+
+    #[test]
+    fn test_save_and_load_settings() {
+        let dir = std::env::temp_dir().join("epub-read-test");
+        let _ = std::fs::create_dir_all(&dir);
+
+        let mut s = Settings::default();
+        s.font_size = 24.0;
+        s.theme = Theme::Dark;
+        save_settings(&dir, &s).unwrap();
+
+        let loaded = load_settings(&dir).unwrap();
+        assert_eq!(loaded.font_size, 24.0);
+        assert_eq!(loaded.theme, Theme::Dark);
+
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn test_load_settings_nonexistent() {
+        let dir = std::env::temp_dir().join("epub-read-test-nonexistent");
+        let _ = std::fs::remove_dir_all(&dir);
+        let result = load_settings(&dir);
+        assert!(result.is_err());
+    }
+}