feat: integrate Pi backend and Pi Web

pi-web/lib/file-upload.ts

@@ -0,0 +1,59 @@
+import fs from "fs";
+import path from "path";
+
+export const UPLOAD_CONFLICT_STRATEGIES = ["error", "overwrite", "skip"] as const;
+export type UploadConflictStrategy = typeof UPLOAD_CONFLICT_STRATEGIES[number];
+
+const UPLOAD_CONFLICT_STRATEGY_SET = new Set<string>(UPLOAD_CONFLICT_STRATEGIES);
+
+export interface UploadTargetInspection {
+  conflicts: string[];
+  nonReplaceable: string[];
+}
+
+export function parseUploadConflictStrategy(value: string | null): UploadConflictStrategy | null {
+  const candidate = value ?? "error";
+  return UPLOAD_CONFLICT_STRATEGY_SET.has(candidate)
+    ? candidate as UploadConflictStrategy
+    : null;
+}
+
+export function validateUploadFileNames(fileNames: string[]): string | null {
+  if (fileNames.length === 0) return "No files selected";
+
+  const seen = new Set<string>();
+  for (const fileName of fileNames) {
+    if (!fileName || fileName === "." || fileName === ".." || fileName.includes("\0")) {
+      return `Invalid file name: ${fileName || "(empty)"}`;
+    }
+    if (fileName.includes("/") || fileName.includes("\\") || path.basename(fileName) !== fileName) {
+      return `File names must not contain a path: ${fileName}`;
+    }
+    if (seen.has(fileName)) return `Duplicate file name in upload: ${fileName}`;
+    seen.add(fileName);
+  }
+
+  return null;
+}
+
+export function inspectUploadTargets(directory: string, fileNames: string[]): UploadTargetInspection {
+  const conflicts: string[] = [];
+  const nonReplaceable: string[] = [];
+
+  for (const fileName of fileNames) {
+    const destination = path.join(directory, fileName);
+    let stat: fs.Stats;
+    try {
+      stat = fs.lstatSync(destination);
+    } catch (error) {
+      const code = (error as NodeJS.ErrnoException).code;
+      if (code === "ENOENT") continue;
+      throw error;
+    }
+
+    conflicts.push(fileName);
+    if (!stat.isFile() || stat.isSymbolicLink()) nonReplaceable.push(fileName);
+  }
+
+  return { conflicts, nonReplaceable };
+}