Provide inbucket object in Lua (#351)

* fix delve fortify thingy
* Expose inbucket.after.message_stored in lua
* Expose inbucket.after.message_deleted in lua
* Expose inbucket.before.mail_accepted in lua

pkg/extension/luahost/bind_inbucket.go

@@ -0,0 +1,218 @@
+package luahost
+
+import (
+	"errors"
+	"fmt"
+
+	lua "github.com/yuin/gopher-lua"
+)
+
+const (
+	inbucketName       = "inbucket"
+	inbucketBeforeName = "inbucket_before"
+	inbucketAfterName  = "inbucket_after"
+)
+
+// Inbucket is the primary Lua interface data structure.
+type Inbucket struct {
+	After  InbucketAfterFuncs
+	Before InbucketBeforeFuncs
+}
+
+// InbucketAfterFuncs holds references to Lua extension functions to be called async
+// after Inbucket handles an event.
+type InbucketAfterFuncs struct {
+	MessageDeleted *lua.LFunction
+	MessageStored  *lua.LFunction
+}
+
+// InbucketBeforeFuncs holds references to Lua extension functions to be called
+// before Inbucket handles an event.
+type InbucketBeforeFuncs struct {
+	MailAccepted *lua.LFunction
+}
+
+func registerInbucketTypes(ls *lua.LState) {
+	// inbucket type.
+	mt := ls.NewTypeMetatable(inbucketName)
+	ls.SetField(mt, "__index", ls.NewFunction(inbucketIndex))
+
+	// inbucket global var.
+	ud := wrapInbucket(ls, &Inbucket{})
+	ls.SetGlobal(inbucketName, ud)
+
+	// inbucket.after type.
+	mt = ls.NewTypeMetatable(inbucketAfterName)
+	ls.SetField(mt, "__index", ls.NewFunction(inbucketAfterIndex))
+	ls.SetField(mt, "__newindex", ls.NewFunction(inbucketAfterNewIndex))
+
+	// inbucket.before type.
+	mt = ls.NewTypeMetatable(inbucketBeforeName)
+	ls.SetField(mt, "__index", ls.NewFunction(inbucketBeforeIndex))
+	ls.SetField(mt, "__newindex", ls.NewFunction(inbucketBeforeNewIndex))
+}
+
+func wrapInbucket(ls *lua.LState, val *Inbucket) *lua.LUserData {
+	ud := ls.NewUserData()
+	ud.Value = val
+	ls.SetMetatable(ud, ls.GetTypeMetatable(inbucketName))
+
+	return ud
+}
+
+func wrapInbucketAfter(ls *lua.LState, val *InbucketAfterFuncs) *lua.LUserData {
+	ud := ls.NewUserData()
+	ud.Value = val
+	ls.SetMetatable(ud, ls.GetTypeMetatable(inbucketAfterName))
+
+	return ud
+}
+
+func wrapInbucketBefore(ls *lua.LState, val *InbucketBeforeFuncs) *lua.LUserData {
+	ud := ls.NewUserData()
+	ud.Value = val
+	ls.SetMetatable(ud, ls.GetTypeMetatable(inbucketBeforeName))
+
+	return ud
+}
+
+func getInbucket(ls *lua.LState) (*Inbucket, error) {
+	lv := ls.GetGlobal(inbucketName)
+	if lv == nil {
+		return nil, errors.New("inbucket object was nil")
+	}
+
+	ud, ok := lv.(*lua.LUserData)
+	if !ok {
+		return nil, fmt.Errorf("inbucket object was type %s instead of UserData", lv.Type())
+	}
+
+	val, ok := ud.Value.(*Inbucket)
+	if !ok {
+		return nil, fmt.Errorf("inbucket object (%v) could not be cast", ud.Value)
+	}
+
+	return val, nil
+}
+
+func checkInbucket(ls *lua.LState, pos int) *Inbucket {
+	ud := ls.CheckUserData(pos)
+	if val, ok := ud.Value.(*Inbucket); ok {
+		return val
+	}
+	ls.ArgError(1, inbucketName+" expected")
+	return nil
+}
+
+func checkInbucketAfter(ls *lua.LState, pos int) *InbucketAfterFuncs {
+	ud := ls.CheckUserData(pos)
+	if val, ok := ud.Value.(*InbucketAfterFuncs); ok {
+		return val
+	}
+	ls.ArgError(1, inbucketAfterName+" expected")
+	return nil
+}
+
+func checkInbucketBefore(ls *lua.LState, pos int) *InbucketBeforeFuncs {
+	ud := ls.CheckUserData(pos)
+	if val, ok := ud.Value.(*InbucketBeforeFuncs); ok {
+		return val
+	}
+	ls.ArgError(1, inbucketBeforeName+" expected")
+	return nil
+}
+
+// inbucket getter.
+func inbucketIndex(ls *lua.LState) int {
+	ib := checkInbucket(ls, 1)
+	field := ls.CheckString(2)
+
+	// Push the requested field's value onto the stack.
+	switch field {
+	case "after":
+		ls.Push(wrapInbucketAfter(ls, &ib.After))
+	case "before":
+		ls.Push(wrapInbucketBefore(ls, &ib.Before))
+	default:
+		// Unknown field.
+		ls.Push(lua.LNil)
+	}
+
+	return 1
+}
+
+// inbucket.after getter.
+func inbucketAfterIndex(ls *lua.LState) int {
+	after := checkInbucketAfter(ls, 1)
+	field := ls.CheckString(2)
+
+	// Push the requested field's value onto the stack.
+	switch field {
+	case "message_deleted":
+		ls.Push(funcOrNil(after.MessageDeleted))
+	case "message_stored":
+		ls.Push(funcOrNil(after.MessageStored))
+	default:
+		// Unknown field.
+		ls.Push(lua.LNil)
+	}
+
+	return 1
+}
+
+// inbucket.after setter.
+func inbucketAfterNewIndex(ls *lua.LState) int {
+	m := checkInbucketAfter(ls, 1)
+	index := ls.CheckString(2)
+
+	switch index {
+	case "message_deleted":
+		m.MessageDeleted = ls.CheckFunction(3)
+	case "message_stored":
+		m.MessageStored = ls.CheckFunction(3)
+	default:
+		ls.RaiseError("invalid inbucket.after index %q", index)
+	}
+
+	return 0
+}
+
+// inbucket.before getter.
+func inbucketBeforeIndex(ls *lua.LState) int {
+	before := checkInbucketBefore(ls, 1)
+	field := ls.CheckString(2)
+
+	// Push the requested field's value onto the stack.
+	switch field {
+	case "mail_accepted":
+		ls.Push(funcOrNil(before.MailAccepted))
+	default:
+		// Unknown field.
+		ls.Push(lua.LNil)
+	}
+
+	return 1
+}
+
+// inbucket.before setter.
+func inbucketBeforeNewIndex(ls *lua.LState) int {
+	m := checkInbucketBefore(ls, 1)
+	index := ls.CheckString(2)
+
+	switch index {
+	case "mail_accepted":
+		m.MailAccepted = ls.CheckFunction(3)
+	default:
+		ls.RaiseError("invalid inbucket.before index %q", index)
+	}
+
+	return 0
+}
+
+func funcOrNil(f *lua.LFunction) lua.LValue {
+	if f == nil {
+		return lua.LNil
+	}
+
+	return f
+}