URL shortener and file dump for hashru.link https://hashru.link
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package rushlink
//go:generate go-bindata -pkg $GOPACKAGE -prefix assets/ assets/...
import (
"bytes"
"fmt"
html "html/template"
"io"
"log"
"net/http"
"path/filepath"
"regexp"
"runtime/debug"
"sort"
"strconv"
"strings"
text "text/template"
"time"
"github.com/pkg/errors"
)
const defaultScheme = "http"
// Plain text templates
var textBaseTemplate *text.Template = text.Must(text.New("").Parse(string(MustAsset("templates/txt/base.txt.tmpl"))))
var htmlBaseTemplate *html.Template = html.Must(html.New("").Parse(string(MustAsset("templates/html/base.html.tmpl"))))
// Template collections
var textTemplates = make(map[string]*text.Template, 0)
var htmlTemplates = make(map[string]*html.Template, 0)
// Used by resolveResponseContentType
var acceptHeaderMediaRangeRegex = regexp.MustCompile(`^\s*([^()<>@,;:\\"/\[\]?.=]+)/([^()<>@,;:\\"/\[\]?.=]+)\s*$`)
var acceptHeaderAcceptParamsRegex = regexp.MustCompile(`^\s*(\w+)=([A-Za-z0-9.-]+)\s*$`)
var acceptHeaderWeight = regexp.MustCompile(`^\s*q=0(?:\.([0-9]{0,3}))|1(?:\.0{0,3})\s*$`)
// HTML templates
func init() {
for _, tmplPath := range AssetNames() {
if mustMatch("templates/txt/*.txt.tmpl", tmplPath) {
base := text.Must(textBaseTemplate.Clone())
tmpl, err := base.Parse(string(MustAsset(tmplPath)))
if err != nil {
panic(errors.Wrapf(err, "parsing %v", tmplPath))
}
tmplName := strings.TrimSuffix(filepath.Base(tmplPath), ".txt.tmpl")
textTemplates[tmplName] = tmpl
continue
}
if mustMatch("templates/html/*.html.tmpl", tmplPath) {
base := html.Must(htmlBaseTemplate.Clone())
tmpl, err := base.Parse(string(MustAsset(tmplPath)))
if err != nil {
panic(errors.Wrapf(err, "parsing %v", tmplPath))
}
tmplName := strings.TrimSuffix(filepath.Base(tmplPath), ".html.tmpl")
htmlTemplates[tmplName] = tmpl
continue
}
}
// Sanity check. Both maps should not be empty
if len(textTemplates) == 0 || len(htmlTemplates) == 0 {
panic("template loading failed")
}
}
func mustMatch(pattern, name string) bool {
m, err := filepath.Match(pattern, name)
if err != nil {
panic("%v error in call to mustMatch")
}
return m
}
func parseFail(tmplName string, err error) {
panic(errors.Wrapf(err, "parsing of %v failed", tmplName))
}
func mapExtend(m map[string]interface{}, key string, value interface{}) {
if m[key] != nil {
return
}
m[key] = value
}
func (rl *rushlink) renderStatic(w http.ResponseWriter, r *http.Request, path string) {
var modTime time.Time
if info, err := AssetInfo(path); err == nil {
modTime = info.ModTime()
}
contents, err := Asset(path)
if err != nil {
rl.renderError(w, r, http.StatusNotFound, err.Error())
return
}
http.ServeContent(w, r, path, modTime, bytes.NewReader(contents))
}
func (rl *rushlink) render(w http.ResponseWriter, r *http.Request, status int, tmplName string, data map[string]interface{}) {
contentType, err := resolveResponseContentType(r, []string{"text/plain", "text/html"})
if err != nil {
w.WriteHeader(http.StatusNotAcceptable)
fmt.Fprintf(w, "error parsing Accept header: %v\n", err)
return
}
// Add the request to the template data
mapExtend(data, "RootURL", rl.resolveRootURL(r))
mapExtend(data, "Request", r)
switch contentType {
case "text/plain":
w.Header().Set("Content-Type", "text/plain")
tmpl := textTemplates[tmplName]
if tmpl == nil {
err = fmt.Errorf("'%v' not in textTemplates", tmplName)
break
}
if status != 0 {
w.WriteHeader(status)
}
if r.Method != "HEAD" {
err = tmpl.Execute(w, data)
}
case "text/html":
w.Header().Set("Content-Type", "text/html")
tmpl := htmlTemplates[tmplName]
if tmpl == nil {
err = fmt.Errorf("'%v' not in htmlTemplates", tmplName)
break
}
// Construct a (lazy) plain-text view for inclusion in <pre>
data["Pre"] = func() string {
tmpl := textTemplates[tmplName]
if tmpl == nil {
panic(fmt.Errorf("'%v' not in textTemplates", tmplName))
}
var buf bytes.Buffer
if err := tmpl.Execute(&buf, data); err != nil {
panic(err)
}
return buf.String()
}
if status != 0 {
w.WriteHeader(status)
}
if r.Method != "HEAD" {
err = tmpl.Execute(w, data)
}
default:
// Fall back to plain text without template
w.WriteHeader(http.StatusNotAcceptable)
io.WriteString(w, "could not resolve an acceptable content-type\n")
}
if err != nil {
panic(err)
}
}
func (rl *rushlink) renderError(w http.ResponseWriter, r *http.Request, status int, msg string) {
rl.render(w, r, status, "error", map[string]interface{}{"Message": msg})
}
func (rl *rushlink) renderInternalServerError(w http.ResponseWriter, r *http.Request, err interface{}) {
msg := fmt.Sprintf("internal server error: %v", err)
rl.renderError(w, r, http.StatusInternalServerError, msg)
}
// resolveRootURL constructs the `scheme://host` part of rushlinks public API.
//
// If the `--root_url` flag is set, it will return that URL.
// Otherwise, this function will return 'https://{Host}', where `{Host}` is
// the value provided by the client in the HTTP `Host` header. This value may
// be invalid, but it is impossible to handle this error (because we *cannot*
// know the real host).
func (rl *rushlink) resolveRootURL(r *http.Request) string {
rlHost := rl.RootURL()
if rlHost != nil {
// Root URL overridden by command line arguments
return rlHost.String()
}
// Guess scheme
scheme := defaultScheme
forwardedScheme := r.Header.Get("X-Forwarded-Proto")
switch forwardedScheme {
case "http":
scheme = "http"
break
case "https":
scheme = "https"
break
}
// Guess host
host := r.Host
if forwardedHost := r.Header.Get("X-Forwarded-Host"); forwardedHost != "" {
host = forwardedHost
}
return scheme + "://" + host
}
// Try to resolve the preferred content-type for the response to this request.
//
// This is done by reading from the `types` argument. If one of them matches
// the preferences supplied by the client in their Accept header, we will
// return that one. We will take the clients preferences into account.
//
// Iff no match could be found, this function will return an empty string, and
// the caller should probably respond with a 406 Not Acceptable status code.
// Iff the Accept header was invalid, we will return an error. In this case,
// the situation calls for a 400 Bad Request.
func resolveResponseContentType(r *http.Request, types []string) (string, error) {
// Ref: https://tools.ietf.org/html/rfc7231#section-5.3.2
if len(types) == 0 {
return "", nil
}
acceptHeader := strings.TrimSpace(r.Header.Get("Accept"))
if acceptHeader == "" {
return types[0], nil
}
type AcceptValue struct {
Type string
Subtype string
Weight int
}
avStrings := strings.Split(acceptHeader, ",")
avs := make([]AcceptValue, len(avStrings))
for i, avString := range avStrings {
av := AcceptValue{Weight: 1000}
choiceParts := strings.Split(avString, ";")
mediaRange := acceptHeaderMediaRangeRegex.FindStringSubmatch(choiceParts[0])
if mediaRange == nil {
return "", fmt.Errorf("bad media-range ('%v')", choiceParts[0])
}
av.Type = mediaRange[1]
av.Subtype = mediaRange[2]
// Go through the rest to see if there is a q=... parameter
for choiceParts = choiceParts[1:]; len(choiceParts) > 0; choiceParts = choiceParts[1:] {
// Try to parse the weight param
weight := acceptHeaderWeight.FindStringSubmatch(choiceParts[0])
if weight != nil {
if weight[1] == "" {
av.Weight = 0
} else {
var err error
av.Weight, err = strconv.Atoi((weight[1] + "000")[:3])
if err != nil {
log.Println("error: unreachable statement")
debug.PrintStack()
av.Weight = 1000 // Reset to default value
}
}
break
}
// Check if this parameter is still invalid in any case
acceptParams := acceptHeaderAcceptParamsRegex.FindStringSubmatchIndex(choiceParts[0])
if acceptParams == nil {
return "", fmt.Errorf("bad accept-params ('%v')", choiceParts[0])
}
}
avs[i] = av
}
sort.SliceStable(avs, func(i, j int) bool {
if avs[i].Weight > avs[j].Weight {
return true
}
if avs[i].Type != "*" && avs[j].Type == "*" {
return true
}
if avs[i].Subtype != "*" && avs[j].Subtype == "*" {
return true
}
return false
})
avArgs := make([]AcceptValue, len(types))
for i, fulltype := range types {
split := strings.Split(fulltype, "/")
if len(split) == 1 {
avArgs[i] = AcceptValue{Type: split[0]}
} else {
avArgs[i] = AcceptValue{Type: split[0], Subtype: split[1]}
}
}
for _, av := range avs {
for j, avArg := range avArgs {
if !(av.Type == avArg.Type || av.Type == "*" || avArg.Type == "*") {
continue
}
if !(av.Subtype == avArg.Subtype || av.Subtype == "*" || avArg.Subtype == "*") {
continue
}
return types[j], nil
}
}
return "", nil
}