refactor backend

src-tauri/src/utils.rs

@@ -0,0 +1,71 @@
+use std::{
+    env, fs,
+    path::{Path, PathBuf},
+};
+
+use base64::{engine::general_purpose::STANDARD, Engine as _};
+use serde_json::Value;
+
+pub fn local_app_data_dir() -> Option<PathBuf> {
+    env::var_os("LOCALAPPDATA").map(PathBuf::from).or_else(|| {
+        env::var_os("USERPROFILE")
+            .map(PathBuf::from)
+            .map(|path| path.join("AppData").join("Local"))
+    })
+}
+
+pub fn pick_latest_subdirectory(root: &Path) -> Option<PathBuf> {
+    let entries = fs::read_dir(root).ok()?;
+    let mut candidates = entries
+        .flatten()
+        .filter_map(|entry| {
+            let file_type = entry.file_type().ok()?;
+            if !file_type.is_dir() {
+                return None;
+            }
+            let metadata = entry.metadata().ok()?;
+            let modified = metadata.modified().ok();
+            Some((
+                modified,
+                entry.file_name().to_string_lossy().to_string(),
+                entry.path(),
+            ))
+        })
+        .collect::<Vec<_>>();
+
+    candidates.sort_by(|left, right| right.0.cmp(&left.0).then_with(|| right.1.cmp(&left.1)));
+    candidates.into_iter().next().map(|(_, _, path)| path)
+}
+
+pub fn load_image_as_data_url(path: &Path) -> Option<String> {
+    let bytes = fs::read(path).ok()?;
+    let extension = path
+        .extension()
+        .and_then(|value| value.to_str())
+        .map(|value| value.to_ascii_lowercase())?;
+    let mime_type = match extension.as_str() {
+        "png" => "image/png",
+        "jpg" | "jpeg" => "image/jpeg",
+        "webp" => "image/webp",
+        "gif" => "image/gif",
+        "svg" => "image/svg+xml",
+        _ => return None,
+    };
+
+    Some(format!(
+        "data:{mime_type};base64,{}",
+        STANDARD.encode(bytes)
+    ))
+}
+
+pub fn read_json_file(path: &Path) -> Option<Value> {
+    let content = fs::read_to_string(path).ok()?;
+    serde_json::from_str(&content).ok()
+}
+
+pub fn first_non_empty<'a>(values: impl IntoIterator<Item = Option<&'a str>>) -> Option<&'a str> {
+    values
+        .into_iter()
+        .flatten()
+        .find(|value| !value.trim().is_empty())
+}