Extract Lua infrastructure into a plugin

2 files changed, 193 insertions, 0 deletions

diff --git a/plugins/lua/lua.go b/plugins/lua/lua.go
new file mode 100644
index 0000000..bbc5c39
--- /dev/null
+++ b/plugins/lua/lua.go
@@ -0,0 +1,184 @@
+package koushinlua
+
+import (
+	"fmt"
+	"html/template"
+	"path/filepath"
+
+	"github.com/labstack/echo/v4"
+	"github.com/yuin/gopher-lua"
+	"layeh.com/gopher-luar"
+	"git.sr.ht/~emersion/koushin"
+)
+
+type luaRoute struct {
+	method string
+	path   string
+	f      *lua.LFunction
+}
+
+type luaPlugin struct {
+	filename        string
+	state           *lua.LState
+	renderCallbacks map[string]*lua.LFunction
+	filters         template.FuncMap
+	routes          []luaRoute
+}
+
+func (p *luaPlugin) Name() string {
+	return p.filename
+}
+
+func (p *luaPlugin) onRender(l *lua.LState) int {
+	name := l.CheckString(1)
+	f := l.CheckFunction(2)
+	p.renderCallbacks[name] = f
+	return 0
+}
+
+func (p *luaPlugin) setFilter(l *lua.LState) int {
+	name := l.CheckString(1)
+	f := l.CheckFunction(2)
+	p.filters[name] = func(args ...interface{}) string {
+		luaArgs := make([]lua.LValue, len(args))
+		for i, v := range args {
+			luaArgs[i] = luar.New(l, v)
+		}
+
+		err := l.CallByParam(lua.P{
+			Fn:      f,
+			NRet:    1,
+			Protect: true,
+		}, luaArgs...)
+		if err != nil {
+			panic(err) // TODO: better error handling?
+		}
+
+		ret := l.CheckString(-1)
+		l.Pop(1)
+		return ret
+	}
+	return 0
+}
+
+func (p *luaPlugin) setRoute(l *lua.LState) int {
+	method := l.CheckString(1)
+	path := l.CheckString(2)
+	f := l.CheckFunction(3)
+	p.routes = append(p.routes, luaRoute{method, path, f})
+	return 0
+}
+
+func (p *luaPlugin) inject(name string, data koushin.RenderData) error {
+	f, ok := p.renderCallbacks[name]
+	if !ok {
+		return nil
+	}
+
+	err := p.state.CallByParam(lua.P{
+		Fn:      f,
+		NRet:    0,
+		Protect: true,
+	}, luar.New(p.state, data))
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (p *luaPlugin) Inject(ctx *koushin.Context, name string, data koushin.RenderData) error {
+	if err := p.inject("*", data); err != nil {
+		return err
+	}
+	return p.inject(name, data)
+}
+
+func (p *luaPlugin) LoadTemplate(t *template.Template) error {
+	t.Funcs(p.filters)
+
+	paths, err := filepath.Glob(filepath.Dir(p.filename) + "/public/*.html")
+	if err != nil {
+		return err
+	}
+	if len(paths) > 0 {
+		if _, err := t.ParseFiles(paths...); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (p *luaPlugin) SetRoutes(group *echo.Group) {
+	for _, r := range p.routes {
+		group.Match([]string{r.method}, r.path, func(ctx echo.Context) error {
+			err := p.state.CallByParam(lua.P{
+				Fn:      r.f,
+				NRet:    0,
+				Protect: true,
+			}, luar.New(p.state, ctx))
+			if err != nil {
+				return fmt.Errorf("Lua plugin error: %v", err)
+			}
+
+			return nil
+		})
+	}
+
+	_, name := filepath.Split(filepath.Dir(p.filename))
+	group.Static("/plugins/"+name+"/assets", filepath.Dir(p.filename)+"/public/assets")
+}
+
+func (p *luaPlugin) Close() error {
+	p.state.Close()
+	return nil
+}
+
+func loadLuaPlugin(filename string) (*luaPlugin, error) {
+	l := lua.NewState()
+	p := &luaPlugin{
+		filename:        filename,
+		state:           l,
+		renderCallbacks: make(map[string]*lua.LFunction),
+		filters:         make(template.FuncMap),
+	}
+
+	mt := l.NewTypeMetatable("koushin")
+	l.SetGlobal("koushin", mt)
+	l.SetField(mt, "on_render", l.NewFunction(p.onRender))
+	l.SetField(mt, "set_filter", l.NewFunction(p.setFilter))
+	l.SetField(mt, "set_route", l.NewFunction(p.setRoute))
+
+	if err := l.DoFile(filename); err != nil {
+		l.Close()
+		return nil, err
+	}
+
+	return p, nil
+}
+
+func loadAllLuaPlugins(s *koushin.Server) ([]koushin.Plugin, error) {
+	log := s.Logger()
+
+	filenames, err := filepath.Glob(koushin.PluginDir + "/*/main.lua")
+	if err != nil {
+		return nil, fmt.Errorf("filepath.Glob failed: %v", err)
+	}
+
+	plugins := make([]koushin.Plugin, 0, len(filenames))
+	for _, filename := range filenames {
+		log.Printf("Loading Lua plugin %q", filename)
+
+		p, err := loadLuaPlugin(filename)
+		if err != nil {
+			for _, p := range plugins {
+				p.Close()
+			}
+			return nil, fmt.Errorf("failed to load Lua plugin %q: %v", filename, err)
+		}
+		plugins = append(plugins, p)
+	}
+
+	return plugins, nil
+}
diff --git a/plugins/lua/plugin.go b/plugins/lua/plugin.go
new file mode 100644
index 0000000..dbfee6d
--- /dev/null
+++ b/plugins/lua/plugin.go
@@ -0,0 +1,9 @@
+package koushinlua
+
+import (
+	"git.sr.ht/~emersion/koushin"
+)
+
+func init() {
+	koushin.RegisterPluginLoader(loadAllLuaPlugins)
+}