path: root/gopherproxy.go

package gopherproxy

import (
	"bytes"
	"crypto/md5"
	"fmt"
	"html"
	"html/template"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"regexp"
	"strings"

	"github.com/temoto/robotstxt"

	"github.com/prologic/go-gopher"

	"github.com/gobuffalo/packr/v2"

	"github.com/davidbyttow/govips/pkg/vips"
)

type Item struct {
	Link template.URL
	Type string
	Text string
}

type AssetList struct {
	Style  string
	JS     string
	FontW  string
	FontW2 string
}

func renderDirectory(w http.ResponseWriter, tpl *template.Template, assetList AssetList, uri string, hostport string, d gopher.Directory) error {
	var title string

	out := make([]Item, len(d.Items))

	for i, x := range d.Items {
		if x.Type == gopher.INFO && x.Selector == "TITLE" {
			title = x.Description
			continue
		}

		tr := Item{
			Text: x.Description,
			Type: x.Type.String(),
		}

		if x.Type == gopher.INFO {
			out[i] = tr
			continue
		}

		if strings.HasPrefix(x.Selector, "URL:") {
			tr.Link = template.URL(x.Selector[4:])
		} else {
			var hostport string
			if x.Port == 70 {
				hostport = x.Host
			} else {
				hostport = fmt.Sprintf("%s:%d", x.Host, x.Port)
			}
			path := url.PathEscape(x.Selector)
			path = strings.Replace(path, "%2F", "/", -1)
			tr.Link = template.URL(
				fmt.Sprintf(
					"/%s/%s%s",
					hostport,
					string(byte(x.Type)),
					path,
				),
			)
		}

		out[i] = tr
	}

	if title == "" {
		title = hostport
	}

	return tpl.Execute(w, struct {
		Title         string
		URI           string
		Assets        AssetList
		Lines         []Item
		RawText       string
		Error         bool
	}{title, fmt.Sprintf("%s/%s", hostport, uri), assetList, out, "", false})
}

// GopherHandler returns a Handler that proxies requests
// to the specified Gopher server as denoated by the first argument
// to the request path and renders the content using the provided template.
// The optional robots parameters points to a robotstxt.RobotsData struct
// to test user agents against a configurable robotst.txt file.
func GopherHandler(tpl *template.Template, robotsdata *robotstxt.RobotsData, assetList AssetList, robotsdebug bool, uri string) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		agent := req.UserAgent()
		path := strings.TrimPrefix(req.URL.Path, "/")

		if robotsdata != nil && robotsdebug && !robotsdata.TestAgent(path, agent) {
			log.Printf("UserAgent %s ignored robots.txt", agent)
		}

		parts := strings.Split(path, "/")
		hostport := parts[0]

		if len(hostport) == 0 {
			http.Redirect(w, req, "/"+uri, http.StatusFound)
			return
		}

		var qs string

		if req.URL.RawQuery != "" {
			qs = fmt.Sprintf("?%s", url.QueryEscape(req.URL.RawQuery))
		}

		uri, err := url.QueryUnescape(strings.Join(parts[1:], "/"))
		if err != nil {
			tpl.Execute(w, struct {
				Title         string
				URI           string
				Assets        AssetList
				RawText       string
				Lines         []Item
				Error         bool
			}{uri, fmt.Sprintf("%s/%s", hostport, uri), assetList, fmt.Sprintf("Error: %s", err), nil, true})
			return
		}

		res, err := gopher.Get(
			fmt.Sprintf(
				"gopher://%s/%s%s",
				hostport,
				uri,
				qs,
			),
		)

		if err != nil {
			tpl.Execute(w, struct {
				Title         string
				URI           string
				Assets        AssetList
				RawText       string
				Lines         []Item
				Error         bool
			}{uri, fmt.Sprintf("%s/%s", hostport, uri), assetList, fmt.Sprintf("Error: %s", err), nil, true})
			return
		}

		if res.Body != nil {
			if len(parts) < 2 {
				io.Copy(w, res.Body)
			} else if parts[1] == "0" { //strings.HasSuffix(uri, ".txt") || strings.HasSuffix(uri, ".md") {
				// handle .txt files
				buf := new(bytes.Buffer)
				buf.ReadFrom(res.Body)
				tpl.Execute(w, struct {
					Title         string
					URI           string
					Assets        AssetList
					RawText       string
					Lines         []Item
					Error         bool
				}{uri, fmt.Sprintf("%s/%s", hostport, uri), assetList, buf.String(), nil, false})
			} else if parts[1] == "T" {
				_, _, err = vips.NewTransform().
					Load(res.Body).
					ResizeStrategy(vips.ResizeStrategyAuto).
					ResizeWidth(160).
					Quality(75).
					Output(w).
					Apply()
			} else {
				io.Copy(w, res.Body)
			}
		} else {
			if err := renderDirectory(w, tpl, assetList, uri, hostport, res.Dir); err != nil {
				tpl.Execute(w, struct {
					Title         string
					URI           string
					Assets        AssetList
					RawText       string
					Lines         []Item
					Error         bool
				}{uri, fmt.Sprintf("%s/%s", hostport, uri), assetList, fmt.Sprintf("Error: %s", err), nil, true})
				return
			}
		}
	}
}

// RobotsTxtHandler returns the contents of the robots.txt file
// if configured and valid.
func RobotsTxtHandler(robotstxtdata []byte) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		if robotstxtdata == nil {
			http.Error(w, "Not Found", http.StatusNotFound)
			return
		}

		w.Header().Set("Content-Type", "text/plain")
		w.Write(robotstxtdata)
	}
}

func FaviconHandler(favicondata []byte) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		if favicondata == nil {
			http.Error(w, "Not Found", http.StatusNotFound)
			return
		}

		w.Header().Set("Content-Type", "image/vnd.microsoft.icon")
		w.Header().Set("Cache-Control", "max-age=2592000")
		w.Write(favicondata)
	}
}

func StyleHandler(styledata []byte) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		w.Header().Set("Content-Type", "text/css")
		w.Header().Set("Cache-Control", "max-age=2592000")
		w.Write(styledata)
	}
}

func JavaScriptHandler(jsdata []byte) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		w.Header().Set("Content-Type", "text/javascript")
		w.Header().Set("Cache-Control", "max-age=2592000")
		w.Write(jsdata)
	}
}

func FontHandler(woff2 bool, fontdata []byte) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		if fontdata == nil {
			http.Error(w, "Not Found", http.StatusNotFound)
			return
		}

		if woff2 {
			w.Header().Set("Content-Type", "font/woff2")
		} else {
			w.Header().Set("Content-Type", "font/woff")
		}
		w.Header().Set("Cache-Control", "max-age=2592000")

		w.Write(fontdata)
	}
}

// ListenAndServe creates a listening HTTP server bound to
// the interface specified by bind and sets up a Gopher to HTTP
// proxy proxying requests as requested and by default will prozy
// to a Gopher server address specified by uri if no servers is
// specified by the request. The robots argument is a pointer to
// a robotstxt.RobotsData struct for testing user agents against
// a configurable robots.txt file.
func ListenAndServe(bind, robotsfile string, robotsdebug bool, vipsconcurrency int, uri string) error {
	var (
		tpl        *template.Template
		robotsdata *robotstxt.RobotsData
	)

	robotstxtdata, err := ioutil.ReadFile(robotsfile)
	if err != nil {
		log.Printf("error reading robots.txt: %s", err)
		robotstxtdata = nil
	} else {
		robotsdata, err = robotstxt.FromBytes(robotstxtdata)
		if err != nil {
			log.Printf("error reading robots.txt: %s", err)
			robotstxtdata = nil
		}
	}

	box := packr.New("assets", "./assets")

	fontdataw, err := box.Find("iosevka-term-ss03-regular.woff")
	if err != nil {
		fontdataw = []byte{}
	}
	fontwAsset := fmt.Sprintf("/iosevka-term-ss03-regular-%x.woff", md5.Sum(fontdataw))

	fontdataw2, err := box.Find("iosevka-term-ss03-regular.woff2")
	if err != nil {
		fontdataw2 = []byte{}
	}
	fontw2Asset := fmt.Sprintf("/iosevka-term-ss03-regular-%x.woff2", md5.Sum(fontdataw2))

	styledata, err := box.Find("style.css")
	if err != nil {
		styledata = []byte{}
	}
	styleAsset := fmt.Sprintf("/style-%x.css", md5.Sum(styledata))

	jsdata, err := box.Find("main.js")
	if err != nil {
		jsdata = []byte{}
	}
	jsAsset := fmt.Sprintf("/main-%x.js", md5.Sum(jsdata))

	favicondata, err := box.Find("favicon.ico")
	if err != nil {
		favicondata = []byte{}
	}

	tpldata, err := ioutil.ReadFile(".template")
	if err == nil {
		tpltext = string(tpldata)
	}

	funcMap := template.FuncMap{
		"safeHtml": func(s string) template.HTML {
			return template.HTML(s)
		},
		"safeCss": func(s string) template.CSS {
			return template.CSS(s)
		},
		"safeJs": func(s string) template.JS {
			return template.JS(s)
		},
		"HTMLEscape": func(s string) string {
			return html.EscapeString(s)
		},
		"split": strings.Split,
		"last": func(s []string) string {
			return s[len(s)-1]
		},
		"pop": func(s []string) []string {
			return s[:len(s)-1]
		},
		"replace": func(pattern, output string, input interface{}) string {
			var re = regexp.MustCompile(pattern)
			var inputStr = fmt.Sprintf("%v", input)
			return re.ReplaceAllString(inputStr, output)
		},
	}

	tpl, err = template.New("gophermenu").Funcs(funcMap).Parse(tpltext)
	if err != nil {
		log.Fatal(err)
	}

	vips.Startup(&vips.Config{
		ConcurrencyLevel: vipsconcurrency,
	})

	http.HandleFunc("/", GopherHandler(tpl, robotsdata, AssetList{styleAsset, jsAsset, fontwAsset, fontw2Asset}, robotsdebug, uri))
	http.HandleFunc("/robots.txt", RobotsTxtHandler(robotstxtdata))
	http.HandleFunc("/favicon.ico", FaviconHandler(favicondata))
	http.HandleFunc(styleAsset, StyleHandler(styledata))
	http.HandleFunc(jsAsset, JavaScriptHandler(jsdata))
	http.HandleFunc(fontwAsset, FontHandler(false, fontdataw))
	http.HandleFunc(fontw2Asset, FontHandler(true, fontdataw2))
	//http.Handle("/assets/", http.StripPrefix("/assets/", http.FileServer(http.Dir("assets/"))))

	return http.ListenAndServe(bind, nil)
}