Iterate over files in random order - swift

Question

I am working on an educational script in swift. The aim is to facilitate collaboration between peers in a university level class on statistics. Each student is required to make suggestions (anonymously) to one of their colleagues' work. The script I have been writing works so that all markdown files in the directory are anonymized (ie, author and email yaml keys are removed) and new files with the contents are created and renamed with an email address.
So far I was able to remove author: and email: yaml keys from each file and I was also able to rename the files in the directory. However, I am struggling to create a way of randomizing files and emails. The point is that the original file should be passed on to another student, but without the last one knowing the author. The receiving student should be decided randomly. This randomization is what I am struggling with.
The MWE
It is a linux project and the easiest way I found to create a MWE was to write the script using the excellent John Sundell's marathon script structure. Below is the code:
import Yaml // marathon: https://github.com/behrang/YamlSwift.git
import Files // marathon:https://github.com/JohnSundell/Files.git
import Foundation
var email: String = ""
var document: String = ""
for file in Folder.current.files {
guard file.extension == "md" else {
continue
}
let content = try file.readAsString()
let pattern = "(?s)(?<=---).*(?=---)"
if let range = content.range(of: pattern, options: .regularExpression) {
let text = String(content[range])
let value = try! Yaml.load(text)
email = value["email"].string!
let author = value["author"].string!
let emailline = "email: " + email
let authorline = "author: " + author
document = content.replacingOccurrences(of: "\n\(emailline)", with: "")
document = content.replacingOccurrences(of: "\n\(authorline)", with: "")
}
// Creating new file with name from email and copying contents into it
//let folder = try Folder()
let file = try Folder.current.createFile(named: email)
try file.write(string: document)
}
An example md file:
---
# Metadata
title: hum
author: jecatatu
email: email#gmail.com
---
This is more text outside the yaml block
email: zwe#gmail.com
A second file:
# Metadata
title: My essay
author: brauser
email: brauser#gmail.com
---
Extra text
A third file:
# Metadata
title: My third essay
author: bestuser
email: bestuser#gmail.com
---
Extra text
Question
To start off, I don't need code. But code is welcome. Note that one can run the above example (provided you have marathon installed) with:
marathon run lf-araujo/collab
I guess I can solve this problem by iterating over the files in the directory in a random order. How can do that? My first thought was to create a dict with emails and filenames, and scramble these two.

Answer 1

What you need is a deterministic way of assigning one reviewer to one peer. You can achieve that by creating a two maps of (random -> article). Sort them by the random key and match the articles by index. An example in pseudo code:
/* Note that you may want to be sure that random keys are unique */
map reviewers = [random_integer(): article_one,
random_integer(): article_two,
...]
map articles = [random_integer(): article_one,
random_integer(): article_two,
...]
sort reviewers by key
sort articles by key
for (index in 0..length(reviewers)) {
assign_reviewer(author_from: reviewers[index], to: articles[index])
}