lua: Init with config and pool (#321)

* lua: Intial impl with config and pool

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

pkg/extension/luahost/lua.go

@@ -0,0 +1,85 @@
+package luahost
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/inbucket/inbucket/pkg/config"
+	"github.com/inbucket/inbucket/pkg/extension"
+	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
+	lua "github.com/yuin/gopher-lua"
+	"github.com/yuin/gopher-lua/parse"
+)
+
+// Host of Lua extensions.
+type Host struct {
+	Functions  []string // Functions detected in lua script.
+	extHost    *extension.Host
+	pool       *statePool
+	logContext zerolog.Context
+}
+
+// New constructs a new Lua Host, pre-compiling the source.
+func New(conf config.Lua, extHost *extension.Host) (*Host, error) {
+	scriptPath := conf.Path
+	if scriptPath == "" {
+		return nil, nil
+	}
+
+	logContext := log.With().Str("module", "lua")
+	logger := logContext.Str("phase", "startup").Str("path", scriptPath).Logger()
+
+	// Pre-load, parse, and compile script.
+	if fi, err := os.Stat(scriptPath); err != nil {
+		logger.Info().Msg("Script file not found")
+		return nil, nil
+	} else if fi.IsDir() {
+		return nil, fmt.Errorf("Lua script %v is a directory", scriptPath)
+	}
+
+	logger.Info().Msg("Loading script")
+	file, err := os.Open(scriptPath)
+	defer file.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	return NewFromReader(extHost, bufio.NewReader(file), scriptPath)
+}
+
+// NewFromReader constructs a new Lua Host, loading Lua source from the provided reader.
+// 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")
+
+	// Pre-parse, and compile script.
+	chunk, err := parse.Parse(r, path)
+	if err != nil {
+		return nil, err
+	}
+	proto, err := lua.Compile(chunk, path)
+	if err != nil {
+		return nil, err
+	}
+
+	// Build the pool and confirm LState is retrievable.
+	pool := newStatePool(proto)
+	h := &Host{extHost: extHost, pool: pool, logContext: logContext}
+	if ls, err := pool.getState(); err == nil {
+		// State creation works, put it back.
+		pool.putState(ls)
+	} else {
+		return nil, err
+	}
+
+	return h, nil
+}
+
+// CreateChannel creates a channel and places it into the named global variable
+// in newly created LStates.
+func (h *Host) CreateChannel(name string) chan lua.LValue {
+	return h.pool.createChannel(name)
+}