episode-id.js

// This is an algorithm, which creates an ID for a podcast episode.
// It is based on the  the podcast's title, episode's title, the episode number,
// the date of the episode and the episode's mp3 file name.
//
// All fields can change over time, but the ID should remain the same.
// Think of it more like a user agent string than a unique ID: it is "unique
// enough" for identifying episodes in most cases.
//
// It's used to identify episodes in the database.

// The algorithm is as follows:
// 1. Get the podcast's title, the episode title, the episode number, the date of the episode, 
//    and the episode's mp3 file name.
// 2. Remove all non-alphanumeric characters
// 3. Remove all leading and trailing whitespace
// 4. Concatenate the fields. Separate the fields with a single `:` character.
// 5. Convert the concatenated string to lowercase.

// The resulting string is the ID of the episode.
// Example:
// Episode title: "Episode 1: The Beginning"
// Podcast title: "The Podcast"
// Episode number: "1"
// Date of the episode: "2018-01-01"
// Episode's mp3 file name: "episode-1.mp3"
// Resulting ID: "thepodcast:episode1thebeginning:1:2018-01-01:episode1.mp3"


// Cleanup function that removes all non-alphanumeric characters and leading and trailing whitespace.
const cleanup = (string) => {
    // Remove all non-alphanumeric characters
    const alphanumeric = string.replace(/[^a-zA-Z0-9]/g, '');

    // Remove all leading and trailing whitespace
    const alphanumericTrimmed = alphanumeric.trim();

    // Convert the string to lowercase.
    const lowercase = alphanumericTrimmed.toLowerCase();

    // Return the resulting string.
    return lowercase;
}

// The function that creates the ID.
const id = (podcastTitle, episodeTitle, episodeNumber, episodeDate, episodeMp3FileName) => {
    // Cleanup all fields
    const cleanedPodcastTitle = cleanup(podcastTitle);
    const cleanedEpisodeTitle = cleanup(episodeTitle);
    const cleanedEpisodeNumber = cleanup(episodeNumber);
    const cleanedEpisodeDate = cleanup(episodeDate);
    const cleanedEpisodeMp3FileName = cleanup(episodeMp3FileName);

    // Concatenate the fields. Separate the fields with a single `:` character.
    const concatenated = cleanedPodcastTitle + ':' + cleanedEpisodeTitle + ':' + cleanedEpisodeNumber + ':' + cleanedEpisodeDate + ':' + cleanedEpisodeMp3FileName;

    // Return the resulting string.
    return concatenated;
}