service.go

package gittp

import (
	"bytes"
	"compress/gzip"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path"
	"strconv"
	"strings"
	"time"
)

type serviceHandler struct {
	w    http.ResponseWriter
	r    *http.Request
	dir  string
	file string
}

func (h *serviceHandler) setHeaderNoCache() {
	h.w.Header().Set("Expires", "Fri, 01 Jan 1980 00:00:00 GMT")
	h.w.Header().Set("Pragma", "no-cache")
	h.w.Header().Set("Cache-Control", "no-cache, max-age=0, must-revalidate")
}

func (h *serviceHandler) setHeaderCacheForever() {
	now := time.Now().Unix()
	expires := now + 31536000
	h.w.Header().Set("Date", fmt.Sprintf("%d", now))
	h.w.Header().Set("Expires", fmt.Sprintf("%d", expires))
	h.w.Header().Set("Cache-Control", "public, max-age=31536000")
}

func (h *serviceHandler) sendFile(contentType string) {
	reqFile := path.Join(h.dir, h.file)
	fi, err := os.Stat(reqFile)
	if os.IsNotExist(err) {
		h.w.WriteHeader(http.StatusNotFound)
		return
	}

	h.w.Header().Set("Content-Type", contentType)
	h.w.Header().Set("Content-Length", fmt.Sprintf("%d", fi.Size()))
	h.w.Header().Set("Last-Modified", fi.ModTime().Format(http.TimeFormat))
	http.ServeFile(h.w, h.r, reqFile)
}

func serviceRPC(h serviceHandler, service string) {
	defer h.r.Body.Close()

	if h.r.Header.Get("Content-Type") != fmt.Sprintf("application/x-git-%s-request", service) {
		h.w.WriteHeader(http.StatusUnauthorized)
		return
	}
	h.w.Header().Set("Content-Type", fmt.Sprintf("application/x-git-%s-result", service))

	var (
		reqBody = h.r.Body
		err     error
	)

	// Handle GZIP
	if h.r.Header.Get("Content-Encoding") == "gzip" {
		reqBody, err = gzip.NewReader(reqBody)
		if err != nil {
			h.w.WriteHeader(http.StatusInternalServerError)
			return
		}
	}

	var stderr bytes.Buffer
	cmd := exec.Command("git", service, "--stateless-rpc", h.dir)

	cmd.Dir = h.dir
	cmd.Stdout = h.w
	cmd.Stderr = &stderr
	cmd.Stdin = reqBody
	if err = cmd.Run(); err != nil {
		h.w.WriteHeader(http.StatusInternalServerError)
		return
	}
}

func serviceUploadPack(h serviceHandler) {
	serviceRPC(h, "upload-pack")
}

func serviceReceivePack(h serviceHandler) {
	serviceRPC(h, "receive-pack")
}

func getServiceType(r *http.Request) string {
	serviceType := r.FormValue("service")
	if !strings.HasPrefix(serviceType, "git-") {
		return ""
	}
	return strings.TrimPrefix(serviceType, "git-")
}

// FIXME: use process module
func gitCommand(dir string, args ...string) []byte {
	cmd := exec.Command("git", args...)
	cmd.Dir = dir
	out, _ := cmd.Output()

	return out
}

func updateServerInfo(dir string) []byte {
	return gitCommand(dir, "update-server-info")
}

func packetWrite(str string) []byte {
	s := strconv.FormatInt(int64(len(str)+4), 16)
	if len(s)%4 != 0 {
		s = strings.Repeat("0", 4-len(s)%4) + s
	}
	return []byte(s + str)
}

func getInfoRefs(h serviceHandler) {
	h.setHeaderNoCache()
	service := getServiceType(h.r)
	if service != "upload-pack" && service != "receive-pack" {
		updateServerInfo(h.dir)
		h.sendFile("text/plain; charset=utf-8")
		return
	}

	refs := gitCommand(h.dir, service, "--stateless-rpc", "--advertise-refs", ".")
	h.w.Header().Set("Content-Type", fmt.Sprintf("application/x-git-%s-advertisement", service))
	h.w.WriteHeader(http.StatusOK)
	h.w.Write(packetWrite("# service=git-" + service + "\n"))
	h.w.Write([]byte("0000"))
	h.w.Write(refs)
}

func getTextFile(h serviceHandler) {
	h.setHeaderNoCache()
	h.sendFile("text/plain")
}

func getInfoPacks(h serviceHandler) {
	h.setHeaderCacheForever()
	h.sendFile("text/plain; charset=utf-8")
}

func getLooseObject(h serviceHandler) {
	h.setHeaderCacheForever()
	h.sendFile("application/x-git-loose-object")
}

func getPackFile(h serviceHandler) {
	h.setHeaderCacheForever()
	h.sendFile("application/x-git-packed-objects")
}

func getIdxFile(h serviceHandler) {
	h.setHeaderCacheForever()
	h.sendFile("application/x-git-packed-objects-toc")
}