Add "copyFile" function, to copy files within the same bucket

Author: nihey

README.md

@@ -67,6 +67,12 @@ client.deletePaths(paths);
 
 - **paths** : Array of relative paths in DO spaces to delete
 
+### Copy file within DO Spaces
+
+```js
+client.copyFile(sourcePath, destinationPath);
+```
+
 ### Download file
 
 ```js

src/index.js

@@ -47,6 +47,20 @@ class SpacesClient {
     return url.replace(/digitaloceanspaces/, 'cdn.digitaloceanspaces');
   }
 
+  async isFilePublic(filePath) {
+    const acl = await this.s3client.getObjectAcl({
+      Bucket: this.bucket,
+      Key: filePath,
+    }).promise();
+
+    const isPublic = acl.Grants.some(({ Grantee, Permission }) => {
+      const isAllUsers = Grantee.URI && Grantee.URI.match(/AllUsers/);
+      const isRead = Permission === 'READ';
+      return isAllUsers && isRead;
+    });
+    return isPublic;
+  }
+
   async uploadFile(
     uploadFilePath,
     destinationPath,
@@ -121,6 +135,20 @@ class SpacesClient {
     return this.deleteObjects(objects);
   }
 
+  async copyFile(
+    sourcePath,
+    destinationPath,
+  ) {
+    const isSourcePublic = await this.isFilePublic(sourcePath);
+
+    return this.s3client.copyObject({
+      Bucket: this.bucket,
+      CopySource: `/${this.bucket}/${sourcePath}`,
+      Key: destinationPath,
+      ACL: isSourcePublic ? 'public-read' : 'private',
+    }).promise();
+  }
+
   async downloadFile(
     filePathToRead,
     filePathToSave,