Adding unpack as cli command and exposing via index.ts for typescript usage. (#5)

src/cli/unpack.ts

@@ -0,0 +1,61 @@
+import { unzipSync } from "fflate";
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "fs";
+import { join, resolve } from "path";
+
+import { extractSignatureBlock } from "../node/sign.js";
+import { getLogger } from "../shared/log.js";
+
+interface UnpackOptions {
+  dxtPath: string;
+  outputDir?: string;
+  silent?: boolean;
+}
+
+export async function unpackExtension({
+  dxtPath,
+  outputDir,
+  silent,
+}: UnpackOptions): Promise<boolean> {
+  const logger = getLogger({ silent });
+  const resolvedDxtPath = resolve(dxtPath);
+
+  if (!existsSync(resolvedDxtPath)) {
+    logger.error(`ERROR: DXT file not found: ${dxtPath}`);
+    return false;
+  }
+
+  const finalOutputDir = outputDir ? resolve(outputDir) : process.cwd();
+
+  if (!existsSync(finalOutputDir)) {
+    mkdirSync(finalOutputDir, { recursive: true });
+  }
+
+  try {
+    const fileContent = readFileSync(resolvedDxtPath);
+    const { originalContent } = extractSignatureBlock(fileContent);
+
+    const decompressed = unzipSync(originalContent);
+
+    for (const relativePath in decompressed) {
+      if (Object.prototype.hasOwnProperty.call(decompressed, relativePath)) {
+        const data = decompressed[relativePath];
+        const fullPath = join(finalOutputDir, relativePath);
+        const dir = join(fullPath, "..");
+        if (!existsSync(dir)) {
+          mkdirSync(dir, { recursive: true });
+        }
+        writeFileSync(fullPath, data);
+      }
+    }
+
+    logger.log(`Extension unpacked successfully to ${finalOutputDir}`);
+    return true;
+  } catch (error) {
+    if (error instanceof Error) {
+      logger.error(`ERROR: Failed to unpack extension: ${error.message}`);
+    } else {
+      logger.error("ERROR: An unknown error occurred during unpacking.");
+    }
+    return false;
+  }
+}