playlist_maker.go

package main

import (
	"fmt"
	"log"
	"time"

	"github.com/zmb3/spotify"
)

func makePlaylist(client *SpotifyClient, cfg *config, d *data) error {
	// So we're ready to potentially make, and append to a target playlist.
	currentUser, err := client.CurrentUser()
	if err != nil {
		return fmt.Errorf("failed to get the current user: %w", err)
	}

	sinceTime := time.Now().Add(-1 * cfg.duration)
	playlistSuffixFormat := "Jan _2, 2006"
	playlistTimeSuffix := fmt.Sprintf(
		"%s - %s",
		sinceTime.Format(playlistSuffixFormat),
		time.Now().Format(playlistSuffixFormat),
	)
	descriptionFormat := "Mon Jan _2, 3:04PM 2006"
	playlist, err := client.CreatePlaylistForUser(
		currentUser.ID,
		fmt.Sprintf("%s (%s)", cfg.playlistName, playlistTimeSuffix),
		fmt.Sprintf(
			"Generated by fangirl - releases from %v to %v.",
			sinceTime.Format(descriptionFormat),
			time.Now().Format(descriptionFormat),
		),
		false,
	)
	if err != nil {
		return fmt.Errorf("failed to create the playlist: %w", err)
	}

	for i, album := range d.albums {
		albumTracksPage, err := client.GetAlbumTracks(album.ID)
		if err != nil {
			return fmt.Errorf("failed to get album tracks: %w", err)
		}

		for {
			batch := make([]spotify.ID, 0, 100)
			for _, track := range albumTracksPage.Tracks {
				batch = append(batch, track.ID)
				if len(batch) == 100 {
					if _, err := client.AddTracksToPlaylist(playlist.ID, batch...); err != nil {
						return fmt.Errorf("failed to add tracks to the playlist: %w", err)
					}
					batch = batch[:0]
				}
			}

			if len(batch) != 0 {
				// If this happens, it means that we finished the batching loop above
				// and had some tracks leftover. So let's not forget to add this to the
				// playlist before we go to the next page of tracks.
				if _, err := client.AddTracksToPlaylist(playlist.ID, batch...); err != nil {
					return fmt.Errorf("failed to add tracks to the playlist: %w", err)
				}
			}

			if err := client.NextSimpleTrackPage(albumTracksPage); err == spotify.ErrNoMorePages {
				break
			} else if err != nil {
				return fmt.Errorf("failed to iterate to the next album track page: %w", err)
			}
		}

		percentageDone := 100 * (float64(i+1) / float64(len(d.albums)))
		log.Printf("\t(%f%% done) Importing into playlist", percentageDone)
	}

	return nil
}