Rename KERI CESR Files With Content-Disposition Header

Hey everyone! Today, we're diving into a neat little trick that can significantly improve how we handle KERI CESR (Composable Event Streaming Representation) files within the context of DID-webs-resolver and Hyperledger. Specifically, we're going to talk about using the Content-Disposition HTTP header to give us more control over file naming. Let's break it down!

The Current Scenario: keri.cesr

Currently, when you make an HTTP request to fetch a KERI CESR file from a path like {did_path}/{aid}/keri.cesr, the server typically returns the file with the name keri.cesr. While this works, it's not always ideal. Sometimes, you might want to rename the file to something more descriptive, like the AID (Identifier Authority Delegation) itself. This is where the Content-Disposition header comes to the rescue.

Why Rename to AID?

You might be wondering, "Why bother renaming the file?" Well, there are a couple of compelling reasons:

• Clarity and Organization: Using the AID as the filename ({AID}.cesr) makes it immediately clear what the file contains. This is especially helpful when you're dealing with multiple KERI files. Imagine a directory filled with keri.cesr files – it would be a nightmare to figure out which one corresponds to which identifier! By using the AID, you instantly know which identifier the file represents.
• Automation and Scripting: When you're automating processes or writing scripts to handle KERI files, having a predictable and unique filename like {AID}.cesr simplifies things immensely. You can easily construct file paths and perform operations without having to parse the file contents to extract the AID.

The Content-Disposition Header: Our Hero

The Content-Disposition HTTP header is a powerful tool that tells the browser (or any HTTP client) how to handle the response. It can instruct the client to display the content inline or, more importantly for our case, to treat it as an attachment and suggest a filename. This is exactly what we need!

By adding the following header to the HTTP response:

Content-Disposition: attachment; filename="EABkKWjtwdBjdKANYlcNijmH8Ub5HNur8rNW4r1ibQDaJ.cesr"

We're telling the client: "Hey, this is an attachment, and you should suggest saving it as EABkKWjtwdBjdKANYlcNijmH8Ub5HNur8r1ibQDaJ.cesr." This gives us the flexibility to return the file with the desired name, making our lives much easier.

Diving Deeper: Content-Disposition Explained

The Content-Disposition HTTP header is a crucial element in web communication, dictating how the recipient's browser or application should handle the received data. It's like a set of instructions attached to the content, guiding its presentation and storage. When dealing with KERI CESR files, the Content-Disposition header becomes particularly valuable, offering a streamlined approach to file management and organization.

Anatomy of the Header

The Content-Disposition header follows a specific structure: Content-Disposition: <disposition-type>; <parameter>=<value>. Let's break down each component:

• Disposition Type: This indicates the primary action the client should take. The two main types are:
  • inline: This suggests that the content should be displayed within the browser or application itself. Think of it as opening a PDF directly in your browser window.
  • attachment: This instructs the client to treat the content as a downloadable file. The browser will typically prompt the user to save the file.
• Parameters: These provide additional details about the disposition. The most relevant parameter for our discussion is:
  • filename: This suggests a filename for the downloaded file. It's a recommendation, not a mandate, as the client might allow the user to choose a different name.

The Power of attachment; filename

The combination of attachment and filename is what empowers us to rename KERI CESR files. By setting Content-Disposition: attachment; filename="{AID}.cesr", we're essentially telling the client: "This is a file you should download, and we recommend you save it as the AID with the .cesr extension." This simple directive has a profound impact on usability and workflow.

Benefits of Using Content-Disposition for KERI Files

• Enhanced User Experience: Instead of dealing with generic keri.cesr filenames, users get files named after their corresponding AIDs. This makes it much easier to identify and manage KERI files, especially in scenarios with multiple identifiers.
• Simplified Automation: When automating processes involving KERI files, having predictable filenames is a huge win. Scripts can easily locate and process files based on their AID, eliminating the need for complex parsing or renaming steps.
• Improved Organization: Consistent and descriptive filenames contribute to a cleaner and more organized file system. This is crucial for maintainability and collaboration, especially in projects involving numerous KERI identities.
• Compliance and Standards: Using Content-Disposition to suggest filenames aligns with best practices for web development and content delivery. It's a standards-compliant way to enhance the user experience and ensure interoperability.

Real-World Examples

Imagine a scenario where you're managing a distributed identity system with hundreds of KERI identifiers. Without the Content-Disposition header, you'd end up with a folder full of keri.cesr files, each requiring manual inspection to determine its corresponding AID. This is a recipe for confusion and errors.

With the Content-Disposition header in place, each file is automatically named after its AID, making it trivial to locate and manage specific identities. This saves time, reduces the risk of mistakes, and significantly improves overall efficiency.

Practical Implementation: How to Use the Header

So, how do we actually implement this? The good news is that it's relatively straightforward. The key is to configure your server (or the application generating the HTTP response) to include the Content-Disposition header when serving KERI CESR files.

Server-Side Configuration

The specific steps will vary depending on your server software (e.g., Apache, Nginx, Node.js), but the general principle remains the same: you need to modify the HTTP response headers.

Here's a conceptual example using a hypothetical server-side framework:

// When handling a request for a KERI CESR file
response.setHeader("Content-Disposition", "attachment; filename=\