use module files (#252)

* use module

* detect files to be restore automatically

* use esbuild

* drop ncc

* add comments

* refactor

src/common.ts

@@ -0,0 +1,72 @@
+import * as fs from "fs";
+import * as path from "path";
+
+import * as core from "@actions/core";
+
+/** state name of backup suffix */
+const STATE_BACKUP_SUFFIX = "backup-suffix";
+
+/**
+ * create backup suffix name
+ * @param dirName directory to back up
+ * @returns backup suffix
+ */
+export function createBackupSuffix(dirName: string): string {
+    if (!fs.existsSync(dirName)) {
+        // do nothing if directory does not exist
+        return "";
+    }
+
+    const backupSuffix = `.bak-${Date.now()}`;
+    core.saveState(STATE_BACKUP_SUFFIX, backupSuffix);
+    return backupSuffix;
+}
+
+/**
+ * get backup suffix name
+ * @returns backup suffix (if not, empty string)
+ */
+export function getBackupSuffix(): string {
+    return core.getState(STATE_BACKUP_SUFFIX);
+}
+
+/**
+ * get SSH directory
+ * @returns SSH directory name
+ */
+export function getSshDirectory(): string {
+    return path.resolve(getHomeDirectory(), ".ssh");
+}
+
+/**
+ * get home directory
+ * @returns home directory name
+ */
+function getHomeDirectory(): string {
+    const homeEnv = getHomeEnv();
+    const home = process.env[homeEnv];
+    if (home === undefined) {
+        throw Error(`${homeEnv} is not defined`);
+    }
+
+    if (home === "/github/home") {
+        // Docker container
+        return "/root";
+    }
+
+    return home;
+}
+
+/**
+ * get HOME environment name
+ * @returns HOME environment name
+ */
+function getHomeEnv(): string {
+    if (process.platform === "win32") {
+        // Windows
+        return "USERPROFILE";
+    }
+
+    // macOS / Linux
+    return "HOME";
+}