Computes and updates a five-stars ranking score on the MusicBrainz dataset

update-musicbrainz.rhai.rs

// This script can literally replace the whole changes I made on this Rust program to alterate
// my dataset to be able to compute scores. You can find the function by follozing this link:
// <https://github.com/Kerollmops/musicbrainz-artist-scoring/blob/901ea2d35707477880f328211c76945a15b2410b/src/main.rs>

// The file extension is .rhai.rs just to be able to highlight the code.
// You can run this Rhai script on the Rhai Playground:
// <https://rhai.rs/playground/stable>

// Here is the context and document Meilisearch provides.
// It's just the setup part of the script

let doc = #{
    artist_rating: 96,
    // artist_rating: (),
    artist_rating_count: 77,
    track_rating: 100
    // track_rating: ()
};

let context = #{
    best_score: 739200,
    smallest_top_score: 93960
};

// -- Actual script starts here... --

fn raw_rating() {
  try {
      this.artist_rating
    * this.artist_rating_count
    * (this.track_rating ?? 1)
  } catch {
      0
  }
}

/// smallest top score -> 4/5 stars
/// biggest score -> 5/5 stars
fn rating(smallest_top_score, best_score) {
    try {
        let smallest = smallest_top_score / 10;
        let smallest_float = smallest_top_score.to_float() / 10.0;

        let raw_rating_float = this.raw_rating.to_float();
        if this.raw_rating >= smallest {
            let remaining = best_score.to_float() - smallest_float / 5.0;
            let base = raw_rating_float - smallest_float;
            4.0 + base / remaining
        } else {
            raw_rating_float * 4.0 / smallest_float
        }
    } catch {
        ()
    }
}

doc.raw_rating = doc.raw_rating();
doc.new_rating = doc.rating(context.smallest_top_score, context.best_score);

// -- ...and ends here --

doc