feat: add now playing endpoint and ui (#93)

* wip

* feat: add now playing

internal/memkv/memkv.go

@@ -0,0 +1,110 @@
+package memkv
+
+import (
+	"sync"
+	"time"
+)
+
+type item struct {
+	value     interface{}
+	expiresAt time.Time
+}
+
+type InMemoryStore struct {
+	data              map[string]item
+	defaultExpiration time.Duration
+	mu                sync.RWMutex
+	stopJanitor       chan struct{}
+}
+
+var Store *InMemoryStore
+
+func init() {
+	Store = NewStore(10 * time.Minute)
+}
+
+func NewStore(defaultExpiration time.Duration) *InMemoryStore {
+	s := &InMemoryStore{
+		data:              make(map[string]item),
+		defaultExpiration: defaultExpiration,
+		stopJanitor:       make(chan struct{}),
+	}
+
+	go s.janitor(1 * time.Minute)
+
+	return s
+}
+
+func (s *InMemoryStore) Set(key string, value interface{}, expiration ...time.Duration) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	exp := s.defaultExpiration
+	if len(expiration) > 0 {
+		exp = expiration[0]
+	}
+
+	var expiresAt time.Time
+	if exp > 0 {
+		expiresAt = time.Now().Add(exp)
+	}
+
+	s.data[key] = item{
+		value:     value,
+		expiresAt: expiresAt,
+	}
+}
+
+func (s *InMemoryStore) Get(key string) (interface{}, bool) {
+	s.mu.RLock()
+	it, found := s.data[key]
+	s.mu.RUnlock()
+
+	if !found {
+		return nil, false
+	}
+
+	if !it.expiresAt.IsZero() && time.Now().After(it.expiresAt) {
+		s.Delete(key)
+		return nil, false
+	}
+
+	return it.value, true
+}
+
+func (s *InMemoryStore) Delete(key string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	delete(s.data, key)
+}
+
+func (s *InMemoryStore) janitor(interval time.Duration) {
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			s.cleanup()
+		case <-s.stopJanitor:
+			return
+		}
+	}
+}
+
+func (s *InMemoryStore) cleanup() {
+	now := time.Now()
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	for k, it := range s.data {
+		if !it.expiresAt.IsZero() && now.After(it.expiresAt) {
+			delete(s.data, k)
+		}
+	}
+}
+
+func (s *InMemoryStore) Close() {
+	close(s.stopJanitor)
+}