commit 25ad77318d92842b7e91c94e2d10da6ab95d2286
Author: Javier Guerra <javier.guerra@konghq.com>
Date:   Fri Nov 15 11:22:25 2019 -0500

    feat(*) initial commit
    
    msgpackrpc and plugin loader (copied from existing runtime)

diff --git a/pluginserver.go b/pluginserver.go
new file mode 100644
index 0000000..46df8f3
--- /dev/null
+++ b/pluginserver.go
@@ -0,0 +1,236 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"github.com/kong/go-pdk"
+	"github.com/ugorji/go/codec"
+	"log"
+	"net"
+	"net/rpc"
+	"path"
+	"plugin"
+	"reflect"
+	"strings"
+)
+
+var socket = flag.String("socket", "", "Socket to listen into")
+
+func runServer(listener net.Listener) {
+	var handle codec.MsgpackHandle
+
+	go func() {
+		for {
+			conn, err := listener.Accept()
+			if err != nil {
+				log.Printf("accept(): %s", err)
+				return
+			}
+			// rpcCodec := codec.GoRpc.ServerCodec(conn, &handle)
+			rpcCodec := codec.MsgpackSpecRpc.ServerCodec(conn, &handle)
+			rpc.ServeCodec(rpcCodec)
+		}
+	}()
+}
+
+func main() {
+	flag.Parse()
+
+	if *socket != "" {
+		listener, err := net.Listen("unix", *socket)
+		if err != nil {
+			log.Printf(`listen("%s"): %s`, socket, err)
+			return
+		}
+
+		rpc.RegisterName("plugin", &PluginServer{})
+
+		runServer(listener)
+	}
+}
+
+// --- pluginData  --- //
+type pluginData struct {
+	code        *plugin.Plugin
+	initialized bool
+	config      interface{}
+	handlers    map[string]func(kong *pdk.PDK)
+}
+
+type (
+	certificater interface{ Certificate(*pdk.PDK) }
+	rewriter     interface{ Rewrite(*pdk.PDK) }
+	accesser     interface{ Access(*pdk.PDK) }
+	headerFilter interface{ HeaderFilter(*pdk.PDK) }
+	bodyFilter   interface{ BodyFilter(*pdk.PDK) }
+	prereader    interface{ Preread(*pdk.PDK) }
+	logger       interface{ Log(*pdk.PDK) }
+)
+
+func (plug *pluginData) setHandlers() {
+	handlers := map[string]func(kong *pdk.PDK){}
+	config := plug.config
+
+	if h, ok := config.(certificater); ok { handlers["certificate"]   = h.Certificate  }
+	if h, ok := config.(rewriter)    ; ok { handlers["rewrite"]       = h.Rewrite      }
+	if h, ok := config.(accesser)    ; ok { handlers["access"]        = h.Access       }
+	if h, ok := config.(headerFilter); ok { handlers["header_filter"] = h.HeaderFilter }
+	if h, ok := config.(bodyFilter)  ; ok { handlers["body_filter"]   = h.BodyFilter   }
+	if h, ok := config.(prereader)   ; ok { handlers["preread"]       = h.Preread      }
+	if h, ok := config.(logger)      ; ok { handlers["log"]           = h.Log          }
+
+	plug.handlers = handlers
+}
+
+// --- PluginServer --- //
+type PluginServer struct {
+	pluginsDir string
+	plugins    map[string]pluginData
+}
+
+/// exported method
+func (s *PluginServer) SetPluginDir(dir string, reply *string) error {
+	s.pluginsDir = dir
+	*reply = "ok"
+	return nil
+}
+
+func (s PluginServer) loadPlugin(name string) (plug pluginData, err error) {
+	plug, ok := s.plugins[name]
+	if ok {
+		return
+	}
+
+	code, err := plugin.Open(path.Join(s.pluginsDir, name+".so"))
+	if err != nil {
+		err = fmt.Errorf("failed to open plugin %s: %w", name, err)
+		return
+	}
+
+	constructorSymbol, err := code.Lookup("New")
+	if err != nil {
+		err = fmt.Errorf("No constructor function on plugin %s: %w", name, err)
+		return
+	}
+	constructor, ok := constructorSymbol.(func() interface{})
+	if !ok {
+		err = fmt.Errorf("Wrong constructor signature on plugin %s: %w", name, err)
+		return
+	}
+
+	plug = pluginData{
+		code:   code,
+		config: constructor(),
+	}
+	plug.setHandlers()
+
+	s.plugins[name] = plug
+	return
+}
+
+func getSchemaType(t reflect.Type) (string, bool) {
+	//log.Printf("SCHEMA TYPE FOR T IS %s\n", t.String())
+	switch t.Kind() {
+	case reflect.String:
+		return `"string"`, true
+	case reflect.Bool:
+		return `"boolean"`, true
+	case reflect.Int, reflect.Int32:
+		return `"integer"`, true
+	case reflect.Uint, reflect.Uint32:
+		return `"integer","between":[0,2147483648]`, true
+	case reflect.Float32, reflect.Float64:
+		return `"number"`, true
+	case reflect.Array:
+		elemType, ok := getSchemaType(t.Elem())
+		if !ok {
+			break
+		}
+		return `"array","elements":{"type":` + elemType + `}`, true
+	case reflect.Map:
+		kType, ok := getSchemaType(t.Key())
+		vType, ok := getSchemaType(t.Elem())
+		if !ok {
+			break
+		}
+		return `"map","keys":{"type":` + kType + `},"values":{"type":` + vType + `}`, true
+	case reflect.Struct:
+		var out strings.Builder
+		out.WriteString(`"record","fields":[`)
+		n := t.NumField()
+		for i := 0; i < n; i++ {
+			field := t.Field(i)
+			typeDecl, ok := getSchemaType(field.Type)
+			if !ok {
+				// ignore unrepresentable types
+				continue
+			}
+			if i > 0 {
+				out.WriteString(`,`)
+			}
+			name := field.Tag.Get("json")
+			if name == "" {
+				name = strings.ToLower(field.Name)
+			}
+			out.WriteString(`{"`)
+			out.WriteString(name)
+			out.WriteString(`":{"type":`)
+			out.WriteString(typeDecl)
+			out.WriteString(`}}`)
+		}
+		out.WriteString(`]`)
+		return out.String(), true
+	}
+	return "", false
+}
+
+type PluginInfo struct {
+	name     string
+	phases   []string
+	version  string
+	priority int
+	schema   string
+}
+
+/// exported method
+func (s *PluginServer) GetPluginInfo(name string, info *PluginInfo) error {
+	info.name = name
+
+	plug, err := s.loadPlugin(name)
+	if err != nil {
+		return err
+	}
+
+	*info = PluginInfo{}
+
+	info.phases = make([]string, len(plug.handlers))
+	var i = 0
+	for name := range plug.handlers {
+		info.phases[i] = name
+		i++
+	}
+
+	v, _ := plug.code.Lookup("Version")
+	if v != nil {
+		info.version = v.(string)
+	}
+
+	prio, _ := plug.code.Lookup("Priority")
+	if prio != nil {
+		info.priority = prio.(int)
+	}
+
+	var out strings.Builder
+	out.WriteString(`{"name":"`)
+	out.WriteString(name)
+	out.WriteString(`","fields":[{"config":{"type":`)
+
+	st, _ := getSchemaType(reflect.TypeOf(plug.config).Elem())
+	out.WriteString(st)
+
+	out.WriteString(`}}]}`)
+
+	info.schema = out.String()
+
+	return nil
+}