Slight refactor; add creds cache worker

* Split the main function into a couple of more functions
* Add credentials, entity, pool and scaleset cache
* add credentials worker that updates the cache

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

cache/tools_cache.go

@@ -0,0 +1,64 @@
+package cache
+
+import (
+	"sync"
+	"time"
+
+	commonParams "github.com/cloudbase/garm-provider-common/params"
+	"github.com/cloudbase/garm/params"
+)
+
+var githubToolsCache *GithubToolsCache
+
+func init() {
+	ghToolsCache := &GithubToolsCache{
+		entities: make(map[string]GithubEntityTools),
+	}
+	githubToolsCache = ghToolsCache
+}
+
+type GithubEntityTools struct {
+	updatedAt time.Time
+	entity    params.GithubEntity
+	tools     []commonParams.RunnerApplicationDownload
+}
+
+type GithubToolsCache struct {
+	mux sync.Mutex
+	// entity IDs are UUID4s. It is highly unlikely they will collide (🤞).
+	entities map[string]GithubEntityTools
+}
+
+func (g *GithubToolsCache) Get(entity params.GithubEntity) ([]commonParams.RunnerApplicationDownload, bool) {
+	g.mux.Lock()
+	defer g.mux.Unlock()
+
+	if cache, ok := g.entities[entity.String()]; ok {
+		if time.Since(cache.updatedAt) > 1*time.Hour {
+			// Stale cache, remove it.
+			delete(g.entities, entity.String())
+			return nil, false
+		}
+		return cache.tools, true
+	}
+	return nil, false
+}
+
+func (g *GithubToolsCache) Set(entity params.GithubEntity, tools []commonParams.RunnerApplicationDownload) {
+	g.mux.Lock()
+	defer g.mux.Unlock()
+
+	g.entities[entity.String()] = GithubEntityTools{
+		updatedAt: time.Now(),
+		entity:    entity,
+		tools:     tools,
+	}
+}
+
+func SetGithubToolsCache(entity params.GithubEntity, tools []commonParams.RunnerApplicationDownload) {
+	githubToolsCache.Set(entity, tools)
+}
+
+func GetGithubToolsCache(entity params.GithubEntity) ([]commonParams.RunnerApplicationDownload, bool) {
+	return githubToolsCache.Get(entity)
+}