feat(backend): add list_directory_children and read_file_content Rust commands

v2/src-tauri/src/lib.rs

@@ -448,6 +448,124 @@ fn project_agent_state_load(
     state.session_db.load_project_agent_state(&project_id)
 }
 
+// --- File browser commands (Files tab) ---
+
+#[derive(serde::Serialize)]
+struct DirEntry {
+    name: String,
+    path: String,
+    is_dir: bool,
+    size: u64,
+    /// File extension (lowercase, without dot), empty for dirs
+    ext: String,
+}
+
+#[tauri::command]
+fn list_directory_children(path: String) -> Result<Vec<DirEntry>, String> {
+    let dir = std::path::Path::new(&path);
+    if !dir.is_dir() {
+        return Err(format!("Not a directory: {path}"));
+    }
+    let mut entries = Vec::new();
+    let read_dir = std::fs::read_dir(dir).map_err(|e| format!("Failed to read directory: {e}"))?;
+    for entry in read_dir {
+        let entry = entry.map_err(|e| format!("Failed to read entry: {e}"))?;
+        let metadata = entry.metadata().map_err(|e| format!("Failed to read metadata: {e}"))?;
+        let name = entry.file_name().to_string_lossy().into_owned();
+        // Skip hidden files/dirs
+        if name.starts_with('.') {
+            continue;
+        }
+        let is_dir = metadata.is_dir();
+        let ext = if is_dir {
+            String::new()
+        } else {
+            std::path::Path::new(&name)
+                .extension()
+                .map(|e| e.to_string_lossy().to_lowercase())
+                .unwrap_or_default()
+        };
+        entries.push(DirEntry {
+            name,
+            path: entry.path().to_string_lossy().into_owned(),
+            is_dir,
+            size: metadata.len(),
+            ext,
+        });
+    }
+    // Sort: dirs first, then files, alphabetical within each group
+    entries.sort_by(|a, b| {
+        b.is_dir.cmp(&a.is_dir).then_with(|| a.name.to_lowercase().cmp(&b.name.to_lowercase()))
+    });
+    Ok(entries)
+}
+
+/// Content types for file viewer routing
+#[derive(serde::Serialize)]
+#[serde(tag = "type")]
+enum FileContent {
+    Text { content: String, lang: String },
+    Binary { message: String },
+    TooLarge { size: u64 },
+}
+
+#[tauri::command]
+fn read_file_content(path: String) -> Result<FileContent, String> {
+    let file_path = std::path::Path::new(&path);
+    if !file_path.is_file() {
+        return Err(format!("Not a file: {path}"));
+    }
+    let metadata = std::fs::metadata(&path).map_err(|e| format!("Failed to read metadata: {e}"))?;
+    let size = metadata.len();
+
+    // Gate: files over 10MB
+    if size > 10 * 1024 * 1024 {
+        return Ok(FileContent::TooLarge { size });
+    }
+
+    let ext = file_path
+        .extension()
+        .map(|e| e.to_string_lossy().to_lowercase())
+        .unwrap_or_default();
+
+    // Binary file types — return message, frontend handles display
+    let binary_exts = ["png", "jpg", "jpeg", "gif", "webp", "svg", "ico", "bmp",
+                       "pdf", "zip", "tar", "gz", "7z", "rar",
+                       "mp3", "mp4", "wav", "ogg", "webm", "avi",
+                       "woff", "woff2", "ttf", "otf", "eot",
+                       "exe", "dll", "so", "dylib", "wasm"];
+    if binary_exts.contains(&ext.as_str()) {
+        return Ok(FileContent::Binary { message: format!("Binary file ({ext}), {size} bytes") });
+    }
+
+    // Text files — read content with language hint
+    let content = std::fs::read_to_string(&path)
+        .map_err(|_| format!("Binary or non-UTF-8 file"))?;
+
+    let lang = match ext.as_str() {
+        "rs" => "rust",
+        "ts" | "tsx" => "typescript",
+        "js" | "jsx" | "mjs" | "cjs" => "javascript",
+        "py" => "python",
+        "svelte" => "svelte",
+        "html" | "htm" => "html",
+        "css" | "scss" | "less" => "css",
+        "json" => "json",
+        "toml" => "toml",
+        "yaml" | "yml" => "yaml",
+        "md" | "markdown" => "markdown",
+        "sh" | "bash" | "zsh" => "bash",
+        "sql" => "sql",
+        "xml" => "xml",
+        "csv" => "csv",
+        "dockerfile" => "dockerfile",
+        "lock" => "text",
+        _ => "text",
+    }.to_string();
+
+    Ok(FileContent::Text { content, lang })
+}
+
 // Directory picker: custom rfd command with parent window for modal behavior on Linux
 #[tauri::command]
 async fn pick_directory(window: tauri::Window) -> Result<Option<String>, String> {
@@ -623,6 +741,8 @@ pub fn run() {
             groups_load,
             groups_save,
             discover_markdown_files,
+            list_directory_children,
+            read_file_content,
             agent_messages_save,
             agent_messages_load,
             project_agent_state_save,