Added a plugin repository, stabilized

go.mod

@@ -1,3 +1,5 @@
 module github.com/diamondburned/cchat
 
 go 1.14
+
+require github.com/pkg/errors v0.9.1

go.sum

@@ -0,0 +1,2 @@
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=

services/plugins/plugins.go

@@ -0,0 +1,63 @@
+// Package plugins provides a source for cchat services as Go plugins. This
+// package looks in UserConfigDir()/cchat/plugins/ by default.
+package plugins
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"plugin"
+
+	"github.com/diamondburned/cchat/services"
+	"github.com/pkg/errors"
+)
+
+var pluginPath string
+
+// SetPluginPath sets the plugin path before loading plugins. This only works
+// until LoadPlugins is called.
+func SetPluginPath(path string) {
+	pluginPath = path
+}
+
+// TryConfigPath returns a path to $cfgDir/suffix. cfgDir is from
+// os.UserConfigDir.
+func TryConfigPath(suffix ...string) (string, error) {
+	d, err := os.UserConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(append([]string{d}, suffix...)...), nil
+}
+
+func init() {
+	services.RegisterSource(loadPlugins)
+}
+
+func loadPlugins() (errs []error) {
+	if pluginPath == "" {
+		p, err := TryConfigPath("cchat", "plugins")
+		if err != nil {
+			errs = []error{errors.Wrap(err, "Failed to get config path")}
+			return
+		}
+		pluginPath = p
+	}
+
+	d, err := ioutil.ReadDir(pluginPath)
+	if err != nil {
+		errs = []error{errors.Wrap(err, "Failed to read plugin path")}
+		return
+	}
+
+	for _, f := range d {
+		// We only need the plugin to call its init() function.
+		_, err := plugin.Open(filepath.Join(pluginPath, f.Name()))
+		if err != nil {
+			errs = append(errs, errors.Wrap(err, "Failed to open plugin"))
+			continue
+		}
+	}
+
+	return
+}

services/services.go

@@ -0,0 +1,55 @@
+// Package services provides a global repository of cchat services. It also
+// supports additional sources.
+//
+// Registering services
+//
+// To register a service, it's best to call RegisterService() in the package's
+// init(). This allows for dash imports:
+//
+//    _ "git.sr.ht/~user/cchat-abc"
+//
+// Registering sources
+//
+// Sources are simply functions that manage other services. An example of this
+// would be the plugins package. Note that only packages that can error out on
+// load should do this. A package can call RegisterService() multiple times.
+//
+// For examples on using RegisterSource(), check the plugins package.
+package services
+
+import (
+	"sync"
+
+	"github.com/diamondburned/cchat"
+)
+
+var services []cchat.Service
+
+// RegisterService adds a service.
+func RegisterService(service ...cchat.Service) {
+	services = append(services, service...)
+}
+
+var sources []func() []error
+var sourceErrs []error
+var sourceOnce sync.Once
+
+// RegisterSource adds a service source. Services are expected to call
+// RegisterService() on source().
+func RegisterSource(source func() []error) {
+	sources = append(sources, source)
+}
+
+// Get returns all services. It will also fetch the plugins from all sources.
+// Future calls will not fetch the plugins again.
+func Get() ([]cchat.Service, []error) {
+	sourceOnce.Do(func() {
+		sourceErrs = []error{} // mark as non-nil
+		for _, src := range sources {
+			sourceErrs = append(sourceErrs, src()...)
+		}
+	})
+
+	// why are we here, just to suffer
+	return services, sourceErrs
+}