feat: support creating and calling custom functions with hashicorp/go-plugin

plugin-gosdk/build.go

@@ -0,0 +1,55 @@
+package plugin
+
+import (
+	"fmt"
+
+	hclog "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/go-plugin"
+)
+
+// Here is a real implementation of funcCaller
+type functionPlugin struct {
+	logger    hclog.Logger
+	functions map[string]func(args ...interface{}) (interface{}, error)
+}
+
+func (p *functionPlugin) GetNames() ([]string, error) {
+	var names []string
+	for name := range p.functions {
+		names = append(names, name)
+	}
+	return names, nil
+}
+
+func (p *functionPlugin) Call(funcName string, args ...interface{}) (interface{}, error) {
+	p.logger.Info("Call function", "funcName", funcName, "args", args)
+
+	f, ok := p.functions[funcName]
+	if !ok {
+		return nil, fmt.Errorf("function %s not found", funcName)
+	}
+
+	return f(args...)
+}
+
+var functions = make(map[string]func(args ...interface{}) (interface{}, error))
+
+func Register(funcName string, fn func(args ...interface{}) (interface{}, error)) {
+	functions[funcName] = fn
+}
+
+func Serve() {
+	funcPlugin := &functionPlugin{
+		logger:    logger,
+		functions: functions,
+	}
+	// pluginMap is the map of plugins we can dispense.
+	var pluginMap = map[string]plugin.Plugin{
+		Name: &hashicorpPlugin{Impl: funcPlugin},
+	}
+
+	plugin.Serve(&plugin.ServeConfig{
+		HandshakeConfig: handshakeConfig,
+		Plugins:         pluginMap,
+	})
+}