audio_features.go

package spotify

import (
	"fmt"
	"strings"
)

// AudioFeatures contains various high-level acoustic attributes
// for a particular track.
type AudioFeatures struct {
	// Acousticness is a confidence measure from 0.0 to 1.0 of whether
	// the track is acoustic.  A value of 1.0 represents high confidence
	// that the track is acoustic.
	Acousticness float32 `json:"acousticness"`
	// An HTTP URL to access the full audio analysis of the track.
	// The URL is cryptographically signed and configured to expire
	// after roughly 10 minutes.  Do not store these URLs for later use.
	AnalysisURL string `json:"analysis_url"`
	// Danceability describes how suitable a track is for dancing based
	// on a combination of musical elements including tempo, rhythm stability,
	// beat strength, and overall regularity.  A value of 0.0 is least danceable
	// and 1.0 is most danceable.
	Danceability float32 `json:"danceability"`
	// The length of the track in milliseconds.
	Duration int `json:"duration_ms"`
	// Energy is a measure from 0.0 to 1.0 and represents a perceptual mesaure
	// of intensity and activity.  Typically, energetic tracks feel fast, loud,
	// and noisy.
	Energy float32 `json:"energy"`
	// The Spotify ID for the track.
	ID ID `json:"id"`
	// Predicts whether a track contains no vocals.  "Ooh" and "aah" sounds are
	// treated as instrumental in this context.  Rap or spoken words are clearly
	// "vocal".  The closer the Instrumentalness value is to 1.0, the greater
	// likelihood the track contains no vocal content.  Values above 0.5 are
	// intended to represent instrumental tracks, but confidence is higher as the
	// value approaches 1.0.
	Instrumentalness float32 `json:"instrumentalness"`
	// The key the track is in.  Integers map to pitches using standard Pitch Class notation
	// (https://en.wikipedia.org/wiki/Pitch_class).
	Key int `json:"key"`
	// Detects the presence of an audience in the recording.  Higher liveness
	// values represent an increased probability that the track was performed live.
	// A value above 0.8 provides strong likelihook that the track is live.
	Liveness float32 `json:"liveness"`
	// The overall loudness of a track in decibels (dB).  Loudness values are
	// averaged across the entire track and are useful for comparing the relative
	// loudness of tracks.  Typical values range between -60 and 0 dB.
	Loudness float32 `json:"loudness"`
	// Mode indicates the modality (major or minor) of a track.
	Mode int `json:"mode"`
	// Detects the presence of spoken words in a track.  The more exclusively
	// speech-like the recording, the closer to 1.0 the speechiness will be.
	// Values above 0.66 describe tracks that are probably made entirely of
	// spoken words.  Values between 0.33 and 0.66 describe tracks that may
	// contain both music and speech, including such cases as rap music.
	// Values below 0.33 most likely represent music and other non-speech-like tracks.
	Speechiness float32 `json:"speechiness"`
	// The overall estimated tempo of the track in beats per minute (BPM).
	Tempo float32 `json:"tempo"`
	// An estimated overall time signature of a track.  The time signature (meter)
	// is a notational convention to specify how many beats are in each bar (or measure).
	TimeSignature int `json:"time_signature"`
	// A link to the Web API endpoint providing full details of the track.
	TrackURL string `json:"track_href"`
	// The Spotify URI for the track.
	URI URI `json:"uri"`
	// A measure from 0.0 to 1.0 describing the musical positiveness conveyed
	// by a track.  Tracks with high valence sound more positive (e.g. happy,
	// cheerful, euphoric), while tracks with low valence sound more negative
	// (e.g. sad, depressed, angry).
	Valence float32 `json:"valence"`
}

// Key represents a pitch using Pitch Class notation.
type Key int

const (
	C Key = iota
	CSharp
	D
	DSharp
	E
	F
	FSharp
	G
	GSharp
	A
	ASharp
	B
	DFlat = CSharp
	EFlat = DSharp
	GFlat = FSharp
	AFlat = GSharp
	BFlat = ASharp
)

// Mode indicates the modality (major or minor) of a track.
type Mode int

const (
	Minor Mode = iota
	Major
)

// GetAudioFeatures queries the Spotify Web API for various
// high-level acoustic attributes of audio tracks.
// Objects are returned in the order requested.  If an object
// is not found, a nil value is returned in the appropriate position.
func (c *Client) GetAudioFeatures(ids ...ID) ([]*AudioFeatures, error) {
	url := fmt.Sprintf("%saudio-features?ids=%s", c.baseURL, strings.Join(toStringSlice(ids), ","))

	temp := struct {
		F []*AudioFeatures `json:"audio_features"`
	}{}

	err := c.get(url, &temp)
	if err != nil {
		return nil, err
	}

	return temp.F, nil
}