lua: Bind after_message_stored and before_mail_accepted (#322)

Signed-off-by: James Hillyerd <james@hillyerd.com>

Signed-off-by: James Hillyerd <james@hillyerd.com>

pkg/extension/luahost/lua.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/inbucket/inbucket/pkg/config"
 	"github.com/inbucket/inbucket/pkg/extension"
+	"github.com/inbucket/inbucket/pkg/extension/event"
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
 	lua "github.com/yuin/gopher-lua"
@@ -54,6 +55,7 @@ func New(conf config.Lua, extHost *extension.Host) (*Host, error) {
 // The provided path is used in logging and error messages.
 func NewFromReader(extHost *extension.Host, r io.Reader, path string) (*Host, error) {
 	logContext := log.With().Str("module", "lua")
+	logger := logContext.Str("phase", "startup").Str("path", path).Logger()
 
 	// Pre-parse, and compile script.
 	chunk, err := parse.Parse(r, path)
@@ -69,6 +71,8 @@ func NewFromReader(extHost *extension.Host, r io.Reader, path string) (*Host, er
 	pool := newStatePool(proto)
 	h := &Host{extHost: extHost, pool: pool, logContext: logContext}
 	if ls, err := pool.getState(); err == nil {
+		h.wireFunctions(logger, ls)
+
 		// State creation works, put it back.
 		pool.putState(ls)
 	} else {
@@ -83,3 +87,107 @@ func NewFromReader(extHost *extension.Host, r io.Reader, path string) (*Host, er
 func (h *Host) CreateChannel(name string) chan lua.LValue {
 	return h.pool.createChannel(name)
 }
+
+const afterMessageStoredFnName string = "after_message_stored"
+const beforeMailAcceptedFnName string = "before_mail_accepted"
+
+// Detects global lua event listener functions and wires them up.
+func (h *Host) wireFunctions(logger zerolog.Logger, ls *lua.LState) {
+	detectFn := func(name string) bool {
+		lval := ls.GetGlobal(name)
+		switch lval.Type() {
+		case lua.LTFunction:
+			logger.Debug().Msgf("Detected %q function", name)
+			h.Functions = append(h.Functions, name)
+			return true
+		case lua.LTNil:
+			logger.Debug().Msgf("Did not detect %q function", name)
+		default:
+			logger.Fatal().Msgf("Found global named %q, but was a %v instead of a function",
+				name, lval.Type().String())
+		}
+
+		return false
+	}
+
+	events := h.extHost.Events
+	const listenerName string = "lua"
+
+	if detectFn(afterMessageStoredFnName) {
+		events.AfterMessageStored.AddListener(listenerName, h.handleAfterMessageStored)
+	}
+	if detectFn(beforeMailAcceptedFnName) {
+		events.BeforeMailAccepted.AddListener(listenerName, h.handleBeforeMailAccepted)
+	}
+}
+
+func (h *Host) handleAfterMessageStored(msg event.MessageMetadata) *extension.Void {
+	logger, ls, lfunc, ok := h.prepareFuncCall(afterMessageStoredFnName)
+	if !ok {
+		return nil
+	}
+	defer h.pool.putState(ls)
+
+	// Call lua function.
+	logger.Debug().Msgf("Calling Lua function with %+v", msg)
+	if err := ls.CallByParam(
+		lua.P{Fn: lfunc, NRet: 0, Protect: true},
+		wrapMessageMetadata(ls, &msg),
+	); err != nil {
+		logger.Error().Err(err).Msg("Failed to call Lua function")
+	}
+
+	return nil
+}
+
+func (h *Host) handleBeforeMailAccepted(addr event.AddressParts) *bool {
+	logger, ls, lfunc, ok := h.prepareFuncCall(beforeMailAcceptedFnName)
+	if !ok {
+		return nil
+	}
+	defer h.pool.putState(ls)
+
+	logger.Debug().Msgf("Calling Lua function with %+v", addr)
+	if err := ls.CallByParam(
+		lua.P{Fn: lfunc, NRet: 1, Protect: true},
+		lua.LString(addr.Local),
+		lua.LString(addr.Domain),
+	); err != nil {
+		logger.Error().Err(err).Msg("Failed to call Lua function")
+		return nil
+	}
+
+	lval := ls.Get(1)
+	ls.Pop(1)
+	logger.Debug().Msgf("Lua function returned %q (%v)", lval, lval.Type().String())
+
+	if lval.Type() == lua.LTNil {
+		return nil
+	}
+
+	result := true
+	if lua.LVIsFalse(lval) {
+		result = false
+	}
+
+	return &result
+}
+
+// Common preparation for calling Lua functions.
+func (h *Host) prepareFuncCall(funcName string) (logger zerolog.Logger, ls *lua.LState, lfunc lua.LValue, ok bool) {
+	logger = h.logContext.Str("event", funcName).Logger()
+
+	ls, err := h.pool.getState()
+	if err != nil {
+		logger.Error().Err(err).Msg("Failed to get Lua state instance from pool")
+		return logger, nil, nil, false
+	}
+
+	lfunc = ls.GetGlobal(funcName)
+	if lfunc.Type() != lua.LTFunction {
+		logger.Error().Msgf("global %q is no longer a function", funcName)
+		return logger, nil, nil, false
+	}
+
+	return logger, ls, lfunc, true
+}