make discovery easier

discovery/discovery.go

@@ -0,0 +1,47 @@
+package discovery
+
+import (
+	"net/url"
+	"os"
+)
+
+var Default = NewService()
+
+type Provider interface {
+	Discover(serviceUrn string) (*url.URL, error)
+}
+
+type Service struct {
+	token     string
+	providers []Provider
+}
+
+func (s *Service) Discover(serviceUrn string) (*url.URL, error) {
+	for idx := range s.providers {
+		provider := s.providers[idx]
+		u, err := provider.Discover(serviceUrn)
+		if err == nil {
+			return u, nil
+		}
+	}
+
+	return nil, os.ErrNotExist
+}
+
+func (s *Service) WithToken(token string) *Service {
+	s.token = token
+	return s
+}
+
+func (s *Service) WithProvider(provider Provider) *Service {
+	s.providers = append(s.providers, provider)
+	return s
+}
+
+func NewService() *Service {
+	return &Service{
+		providers: []Provider{
+			NewLocalDiscovery(),
+		},
+	}
+}

discovery/discovery.json

@@ -0,0 +1,3 @@
+{
+   "test.service": "http://user:password@localhost:8888/test/path"
+}

discovery/discovery_test.go

@@ -0,0 +1,23 @@
+package discovery
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDiscovery(t *testing.T) {
+	discovery := NewService()
+
+	url, err := discovery.Discover("unknown.service")
+	assert.Error(t, err)
+	assert.Nil(t, url)
+
+	url, err = discovery.Discover("test.service")
+	assert.NoError(t, err)
+	require.NotNil(t, url)
+	assert.Equal(t, "localhost", url.Hostname())
+	assert.Equal(t, "8888", url.Port())
+	assert.Equal(t, "/test/path", url.Path)
+}

discovery/file.go

@@ -0,0 +1,58 @@
+package discovery
+
+import (
+	"net/url"
+	"os"
+	"path"
+
+	"git.twelvetwelve.org/library/core/json"
+)
+
+type LocalDiscovery struct {
+}
+
+func lookup(kv map[string]string, serviceUrn string) *url.URL {
+	rawURL, ok := kv[serviceUrn]
+	if !ok {
+		return nil
+	}
+
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		return nil
+	}
+	return u
+}
+
+func lookupFrom(path string, serviceUrn string) *url.URL {
+	services := make(map[string]string)
+	err := json.ReadFromFile(path, &services)
+	if err != nil {
+		return nil
+	}
+	return lookup(services, serviceUrn)
+}
+
+func (ld *LocalDiscovery) Discover(serviceUrn string) (*url.URL, error) {
+	if url := lookupFrom("discovery.json", serviceUrn); url != nil {
+		return url, nil
+	}
+
+	home, err := os.UserHomeDir()
+	if err != nil {
+		homeConf := path.Join(home, ".config", "discovery.json")
+		if url := lookupFrom(homeConf, serviceUrn); url != nil {
+			return url, nil
+		}
+	}
+
+	if url := lookupFrom("/etc/discovery/discovery.json", serviceUrn); url != nil {
+		return url, nil
+	}
+
+	return nil, os.ErrNotExist
+}
+
+func NewLocalDiscovery() *LocalDiscovery {
+	return &LocalDiscovery{}
+}