Add basic support for plugins

6 files changed, 115 insertions, 1 deletions

diff --git a/README.md b/README.md
index 33288c8..82cb933 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,13 @@ Templates in `public/themes/<name>/*.html` override default templates in
 `public/*.html`. Assets in `public/themes/<name>/assets/*` are served by the
 HTTP server at `themes/<name>/assets/*`.
 
+## Plugins
+
+Lua plugins are supported. They can be dropped in `plugins/*.lua`.
+
+For now only a single hook is supported: `render(name, data)`. If defined, this
+Lua function will be called prior to rendering a template.
+
 ## License
 
 MIT
diff --git a/go.mod b/go.mod
index 6107fbe..229f677 100644
--- a/go.mod
+++ b/go.mod
@@ -12,7 +12,9 @@ require (
 	github.com/mattn/go-colorable v0.1.4 // indirect
 	github.com/mattn/go-isatty v0.0.10 // indirect
 	github.com/valyala/fasttemplate v1.1.0 // indirect
+	github.com/yuin/gopher-lua v0.0.0-20191128022950-c6266f4fe8d7
 	golang.org/x/crypto v0.0.0-20191202143827-86a70503ff7e // indirect
 	golang.org/x/net v0.0.0-20191126235420-ef20fe5d7933 // indirect
 	golang.org/x/sys v0.0.0-20191128015809-6d18c012aee9 // indirect
+	layeh.com/gopher-luar v1.0.7
 )
diff --git a/go.sum b/go.sum
index 46cc5b5..869a1ff 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,6 @@
+github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -50,6 +53,9 @@ github.com/valyala/fasttemplate v1.0.1 h1:tY9CJiPnMXf1ERmG2EyK7gNUd+c6RKGD0IfU8W
 github.com/valyala/fasttemplate v1.0.1/go.mod h1:UQGH1tvbgY+Nz5t2n7tXsz52dQxojPUpymEIMZ47gx8=
 github.com/valyala/fasttemplate v1.1.0 h1:RZqt0yGBsps8NGvLSGW804QQqCUYYLsaOjTVHy1Ocw4=
 github.com/valyala/fasttemplate v1.1.0/go.mod h1:UQGH1tvbgY+Nz5t2n7tXsz52dQxojPUpymEIMZ47gx8=
+github.com/yuin/gopher-lua v0.0.0-20190206043414-8bfc7677f583/go.mod h1:gqRgreBUhTSL0GeU64rtZ3Uq3wtjOa/TB2YfrtkCbVQ=
+github.com/yuin/gopher-lua v0.0.0-20191128022950-c6266f4fe8d7 h1:Y17pEjKgx2X0A69WQPGa8hx/Myzu+4NdUxlkZpbAYio=
+github.com/yuin/gopher-lua v0.0.0-20191128022950-c6266f4fe8d7/go.mod h1:gqRgreBUhTSL0GeU64rtZ3Uq3wtjOa/TB2YfrtkCbVQ=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4 h1:HuIa8hRrWRSrqYzx1qI49NNxhdi2PrY7gxVSq1JjLDc=
 golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
@@ -59,6 +65,7 @@ golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3 h1:0GoQqolDA55aaLxZyTzK/Y2eP
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20191126235420-ef20fe5d7933 h1:e6HwijUxhDe+hPNjZQQn9bA5PW3vNmnN64U2ZW759Lk=
 golang.org/x/net v0.0.0-20191126235420-ef20fe5d7933/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/sys v0.0.0-20190204203706-41f3e6584952/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -76,3 +83,5 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+layeh.com/gopher-luar v1.0.7 h1:53iv6CCkRs5wyofZ+qVXcyAYQOIG52s6pt4xkqZdq7k=
+layeh.com/gopher-luar v1.0.7/go.mod h1:TPnIVCZ2RJBndm7ohXyaqfhzjlZ+OA2SZR/YwL8tECk=
diff --git a/plugin.go b/plugin.go
new file mode 100644
index 0000000..b94c330
--- /dev/null
+++ b/plugin.go
@@ -0,0 +1,78 @@
+package koushin
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"github.com/labstack/echo/v4"
+	"github.com/yuin/gopher-lua"
+	"layeh.com/gopher-luar"
+)
+
+type Plugin interface {
+	Name() string
+	Render(name string, data interface{}) error
+	Close() error
+}
+
+type luaPlugin struct {
+	filename string
+	state    *lua.LState
+}
+
+func (p *luaPlugin) Name() string {
+	return p.filename
+}
+
+func (p *luaPlugin) Render(name string, data interface{}) error {
+	global := p.state.GetGlobal("render")
+	if global == nil {
+		return nil
+	}
+
+	if err := p.state.CallByParam(lua.P{
+		Fn:      global,
+		NRet:    0,
+		Protect: true,
+	}, lua.LString(name), luar.New(p.state, data)); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (p *luaPlugin) Close() error {
+	p.state.Close()
+	return nil
+}
+
+func loadLuaPlugin(filename string) (*luaPlugin, error) {
+	l := lua.NewState()
+	if err := l.DoFile(filename); err != nil {
+		return nil, err
+	}
+
+	return &luaPlugin{filename, l}, nil
+}
+
+func loadAllLuaPlugins(log echo.Logger) ([]Plugin, error) {
+	filenames, err := filepath.Glob("plugins/*.lua")
+	if err != nil {
+		return nil, fmt.Errorf("filepath.Glob failed: %v", err)
+	}
+
+	plugins := make([]Plugin, 0, len(filenames))
+	for _, filename := range filenames {
+		log.Printf("Loading Lua plugin '%v'", filename)
+		p, err := loadLuaPlugin(filename)
+		if err != nil {
+			for _, p := range plugins {
+				p.Close()
+			}
+			return nil, fmt.Errorf("failed to load Lua plugin '%v': %v", filename, err)
+		}
+		plugins = append(plugins, p)
+	}
+
+	return plugins, nil
+}
diff --git a/server.go b/server.go
index d8aeca7..0845628 100644
--- a/server.go
+++ b/server.go
@@ -28,6 +28,8 @@ type Server struct {
 		tls      bool
 		insecure bool
 	}
+
+	plugins []Plugin
 }
 
 func (s *Server) parseIMAPURL(imapURL string) error {
@@ -131,6 +133,11 @@ func New(e *echo.Echo, options *Options) error {
 		return fmt.Errorf("failed to load templates: %v", err)
 	}
 
+	s.plugins, err = loadAllLuaPlugins(e.Logger)
+	if err != nil {
+		return fmt.Errorf("failed to load plugins: %v", err)
+	}
+
 	e.HTTPErrorHandler = func(err error, c echo.Context) {
 		code := http.StatusInternalServerError
 		if he, ok := err.(*echo.HTTPError); ok {
@@ -145,6 +152,7 @@ func New(e *echo.Echo, options *Options) error {
 	e.Use(func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(ectx echo.Context) error {
 			ctx := &context{Context: ectx, server: s}
+			ctx.Set("context", ctx)
 
 			cookie, err := ctx.Cookie(cookieName)
 			if err == http.ErrNoCookie {
diff --git a/template.go b/template.go
index f12e2ec..a4c3ee0 100644
--- a/template.go
+++ b/template.go
@@ -1,6 +1,7 @@
 package koushin
 
 import (
+	"fmt"
 	"html/template"
 	"io"
 	"net/url"
@@ -13,7 +14,16 @@ type tmpl struct {
 	t *template.Template
 }
 
-func (t *tmpl) Render(w io.Writer, name string, data interface{}, c echo.Context) error {
+func (t *tmpl) Render(w io.Writer, name string, data interface{}, ectx echo.Context) error {
+	// ectx is the raw *echo.context, not our own *context
+	ctx := ectx.Get("context").(*context)
+
+	for _, plugin := range ctx.server.plugins {
+		if err := plugin.Render(name, data); err != nil {
+			return fmt.Errorf("failed to run plugin '%v': %v", plugin.Name(), err)
+		}
+	}
+
 	return t.t.ExecuteTemplate(w, name, data)
 }