refactor(*) split for readability

Split event and instance handling code into their own modules.

instance.go

@@ -0,0 +1,141 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/kong/go-pdk"
+)
+
+// --- instanceData --- //
+type instanceData struct {
+	id          int
+	plugin      *pluginData
+	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 getHandlers(config interface{}) map[string]func(kong *pdk.PDK) {
+	handlers := map[string]func(kong *pdk.PDK){}
+
+	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          }
+
+	return handlers
+}
+
+// Configuration data for a new plugin instance.
+type PluginConfig struct {
+	Name   string // plugin name
+	Config []byte // configuration data, as a JSON string
+}
+
+// Current state of a plugin instance.  TODO: add some statistics
+type InstanceStatus struct {
+	Name   string      // plugin name
+	Id     int         // instance id
+	Config interface{} // configuration data, decoded
+}
+
+// StartInstance starts a plugin instance, as requred by configuration data.  More than
+// one instance can be started for a single plugin.  If the configuration changes,
+// a new instance should be started and the old one closed.
+//
+// RPC exported method
+func (s *PluginServer) StartInstance(config PluginConfig, status *InstanceStatus) error {
+	plug, err := s.loadPlugin(config.Name)
+	if err != nil {
+		return err
+	}
+
+	instanceConfig := plug.constructor()
+
+	if err := json.Unmarshal(config.Config, instanceConfig); err != nil {
+		return fmt.Errorf("Decoding config: %w", err)
+	}
+
+	instance := instanceData{
+		plugin:   plug,
+		config:   instanceConfig,
+		handlers: getHandlers(instanceConfig),
+	}
+
+	s.lock.Lock()
+	instance.id = s.nextInstanceId
+	s.nextInstanceId++
+	s.instances[instance.id] = &instance
+	s.lock.Unlock()
+
+	*status = InstanceStatus{
+		Name:   config.Name,
+		Id:     instance.id,
+		Config: instance.config,
+	}
+
+	return nil
+}
+
+// InstanceStatus returns a given resource's status (the same given when started)
+//
+// RPC exported method
+func (s PluginServer) InstanceStatus(id int, status *InstanceStatus) error {
+	s.lock.RLock()
+	instance, ok := s.instances[id]
+	s.lock.RUnlock()
+	if !ok {
+		return fmt.Errorf("No plugin instance %d", id)
+	}
+
+	*status = InstanceStatus{
+		Name:   instance.plugin.name,
+		Id:     instance.id,
+		Config: instance.config,
+	}
+
+	return nil
+}
+
+// CloseInstance is used when an instance shouldn't be used anymore.
+// Doesn't kill any running event but the instance is no longer accesible,
+// so it's not possible to start a new event with it and will be garbage
+// collected after the last reference event finishes.
+// Returns the status just before closing.
+//
+// RPC exported method
+func (s PluginServer) CloseInstance(id int, status *InstanceStatus) error {
+	s.lock.RLock()
+	instance, ok := s.instances[id]
+	s.lock.RUnlock()
+	if !ok {
+		return fmt.Errorf("No plugin instance %d", id)
+	}
+
+	*status = InstanceStatus{
+		Name:   instance.plugin.name,
+		Id:     instance.id,
+		Config: instance.config,
+	}
+
+	// kill?
+
+	s.lock.Lock()
+	delete(s.instances, id)
+	s.lock.Unlock()
+
+	return nil
+}