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example_test.go
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example_test.go
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package thevent_test
import (
"context"
"fmt"
"sort"
"time"
)
import "github.com/dhui/thevent"
// Queue output due to how event handlers and children are stored
// See: https://github.com/dhui/thevent/issues/3
type printQueueType struct {
queue []string
}
func (q *printQueueType) Append(s string) {
q.queue = append(q.queue, s)
}
func (q *printQueueType) Clear() {
q.queue = []string{}
}
func (q *printQueueType) Print() {
for _, s := range q.queue {
fmt.Println(s)
}
}
func (q *printQueueType) Sort() {
sort.Strings(q.queue)
}
var printQueue = printQueueType{}
// Song and Playlist data structures and functions
type song struct {
Name string
Artist string
Duration time.Duration
}
type playlist struct {
Name string
Songs []song
}
type songPlaylist struct {
Song song
Playlist playlist
}
type playlistSwapSongs struct {
Playlist playlist
IdxA int
IdxB int
}
func newPlaylist(ctx context.Context, name string, songs ...song) (*playlist, error) {
p := playlist{Name: name, Songs: songs}
if err := playlistCreatedEvent.Dispatch(ctx, p); err != nil {
return nil, err
}
return &p, nil
}
func (p *playlist) queueSong(ctx context.Context, song song) error {
p.Songs = append(p.Songs, song)
return queuedSongEvent.Dispatch(ctx, songPlaylist{Song: song, Playlist: *p})
}
func (p *playlist) swapSongs(ctx context.Context, idxA, idxB int) error {
p.Songs[idxA], p.Songs[idxB] = p.Songs[idxB], p.Songs[idxA]
return swappedSongsEvent.Dispatch(ctx, playlistSwapSongs{Playlist: *p, IdxA: idxA, IdxB: idxB})
}
// Event Handlers
func playlistCreatedHandler(ctx context.Context, p playlist) error { // nolint: unparam
printQueue.Append(fmt.Sprintf("Created playlist %q with songs: %v", p.Name, p.Songs))
return nil
}
func queuedSongHandler(ctx context.Context, sp songPlaylist) error { // nolint: unparam
printQueue.Append(fmt.Sprintf("Queued song %q into playlist %q", sp.Song.Name, sp.Playlist.Name))
return nil
}
func swappedSongHandler(ctx context.Context, pss playlistSwapSongs) error { // nolint: unparam
printQueue.Append(fmt.Sprintf("Swapped songs %q and %q in playlist %q",
pss.Playlist.Songs[pss.IdxB].Name, pss.Playlist.Songs[pss.IdxA].Name, pss.Playlist.Name))
return nil
}
// Helpers
func mustD(d time.Duration, err error) time.Duration {
if err != nil {
panic(err)
}
return d
}
var (
// Parent event
playlistEvent = thevent.Must(thevent.New(playlist{}))
// Child events
playlistCreatedEvent = thevent.Must(playlistEvent.New(playlist{}, "", playlistCreatedHandler))
queuedSongEvent = thevent.Must(playlistEvent.New(songPlaylist{}, "Playlist", queuedSongHandler))
swappedSongsEvent = thevent.Must(playlistEvent.New(playlistSwapSongs{}, "Playlist", swappedSongHandler))
)
func Example() {
ctx := context.Background()
p, err := newPlaylist(ctx, "Best of Jimi")
if err != nil {
fmt.Println(err)
}
if err := p.queueSong(ctx, song{Name: "Purple Haze", Artist: "Jimi Hendrix",
Duration: mustD(time.ParseDuration("2m46s"))}); err != nil {
fmt.Println(err)
}
if err := p.queueSong(ctx, song{Name: "Foxy Lady", Artist: "Jimi Hendrix",
Duration: mustD(time.ParseDuration("3m19s"))}); err != nil {
fmt.Println(err)
}
if err := p.swapSongs(ctx, 0, 1); err != nil {
fmt.Println(err)
}
// Don't need to sort output since none of the dispatched events have multiple children or handlers
printQueue.Print()
printQueue.Clear()
playlistHandler := func(ctx context.Context, p playlist) error { // nolint: unparam
printQueue.Append(fmt.Sprintf("Top-level playlist event got playlist: %q", p.Name))
return nil
}
// Handlers may be added later
if err := playlistEvent.AddHandlers(playlistHandler); err != nil {
fmt.Println(err)
}
// Dispatching the parent event will also dispatch the children. In this case, doing so is nonsensical.
if err := playlistEvent.Dispatch(ctx, *p); err != nil {
fmt.Println(err)
}
// Sort output since the top-level event has multiple children
printQueue.Sort()
printQueue.Print()
// Output:
// Created playlist "Best of Jimi" with songs: []
// Queued song "Purple Haze" into playlist "Best of Jimi"
// Queued song "Foxy Lady" into playlist "Best of Jimi"
// Swapped songs "Purple Haze" and "Foxy Lady" in playlist "Best of Jimi"
// Created playlist "Best of Jimi" with songs: [{Foxy Lady Jimi Hendrix 3m19s} {Purple Haze Jimi Hendrix 2m46s}]
// Queued song "" into playlist "Best of Jimi"
// Swapped songs "Foxy Lady" and "Foxy Lady" in playlist "Best of Jimi"
// Top-level playlist event got playlist: "Best of Jimi"
}