music-brainz-go/mb.go

package mb

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"sort"
	"time"
)

const (
	apiURI               = "https://musicbrainz.org/ws/2"
	artistSearchEndpoint = "artist?query"
)

//MB holds the http client
type MB struct {
	Client http.Client
}

//Search holds the search returns
type Search struct {
	artist artistSearch
}

//NewMusicBrainz returns a new Search object
func NewMusicBrainz() MB {

	var mb MB
	timeout := time.Duration(10 * time.Second)

	mb.Client = http.Client{Timeout: timeout}
	return mb
}

//SearchForArtist return a list of artists using `query` as parameter if none found returns error
func (m MB) SearchForArtist(query string) (*Search, error) {
	var ret Search
	uri := fmt.Sprintf("%s/%s=%s", apiURI, artistSearchEndpoint, url.QueryEscape(query))

	req, err := http.NewRequest(
		"GET",
		uri,
		nil)

	req.Header.Set(
		"User-Agent",
		"Go Application Development: Create spotify playlist based on artist")
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	if err != nil {
		fmt.Printf("error creating request\n%v", err)
		return nil, err
	}

	resp, err := m.Client.Do(req)
	if err != nil {
		fmt.Printf("error opening request\n%v", err)
		return nil, err
	}
	defer resp.Body.Close()
	if err != nil {
		fmt.Printf("could not read body\n%v", err)
		return nil, err
	}
	err = json.NewDecoder(resp.Body).Decode(&ret.artist)
	if err != nil {
		fmt.Printf("could not decode body\n%v", err)
		return nil, err
	}

	if ret.artist.Count == 0 {
		return nil, fmt.Errorf("cound not found artist: %s", query)
	}

	return &ret, nil
}

//GetArtistName get the artist with the highest score on the search
func (s Search) GetArtistName() (string, error) {

	if len(s.artist.Artists) == 0 {
		return "", fmt.Errorf("could not find any artist")
	}
	return s.artist.Artists[0].Name, nil
}

//GetArtistTags returns the tags in order of relevance of the current artist
func (s Search) GetArtistTags() []Tags {
	var t []Tags
	for _, elem := range s.artist.Artists[0].Tags {
		if int(elem.Count) > 0 {
			t = append(t, elem)
		}
	}
	sort.Sort(ByInverseCount(t))
	return t
}

type artistSearch struct {
	Created time.Time `json:"created"`
	Count   int       `json:"count"`
	Offset  int       `json:"offset"`
	Artists []artists `json:"artists"`
}

type area struct {
	ID       string `json:"id"`
	Type     string `json:"type"`
	TypeID   string `json:"type-id"`
	Name     string `json:"name"`
	SortName string `json:"sort-name"`
	LifeSpan struct {
		Ended interface{} `json:"ended"`
	} `json:"life-span"`
}

type alias struct {
	SortName  string      `json:"sort-name"`
	TypeID    string      `json:"type-id,omitempty"`
	Name      string      `json:"name"`
	Locale    interface{} `json:"locale"`
	Type      string      `json:"type"`
	Primary   interface{} `json:"primary"`
	BeginDate interface{} `json:"begin-date"`
	EndDate   interface{} `json:"end-date"`
}

type artists struct {
	ID        string `json:"id"`
	Type      string `json:"type,omitempty"`
	TypeID    string `json:"type-id,omitempty"`
	Score     int    `json:"score"`
	Name      string `json:"name"`
	SortName  string `json:"sort-name"`
	Country   string `json:"country,omitempty"`
	Area      area   `json:"area,omitempty"`
	BeginArea struct {
		ID       string `json:"id"`
		Type     string `json:"type"`
		TypeID   string `json:"type-id"`
		Name     string `json:"name"`
		SortName string `json:"sort-name"`
		LifeSpan struct {
			Ended interface{} `json:"ended"`
		} `json:"life-span"`
	} `json:"begin-area,omitempty"`
	Isnis    []string `json:"isnis,omitempty"`
	LifeSpan struct {
		Begin string      `json:"begin"`
		Ended interface{} `json:"ended"`
	} `json:"life-span,omitempty"`
	Aliases        []alias `json:"aliases,omitempty"`
	Tags           []Tags  `json:"tags,omitempty"`
	Disambiguation string  `json:"disambiguation,omitempty"`
}

//Tags represent Artist tags (eg. Rock, Punk, Late 2000s)
type Tags struct {
	Count int    `json:"count"`
	Name  string `json:"name"`
}

//ByInverseCount return the tags in relevance order
type ByInverseCount []Tags

func (t ByInverseCount) Len() int           { return len(t) }
func (t ByInverseCount) Less(i, j int) bool { return t[i].Count >= t[j].Count }
func (t ByInverseCount) Swap(i, j int)      { t[i], t[j] = t[j], t[i] }