rushlink/views.go

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package rushlink
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//go:generate go-bindata -pkg $GOPACKAGE -prefix assets/ assets/...
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import (
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"bytes"
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"fmt"
html "html/template"
"io"
"log"
"net/http"
"path/filepath"
"regexp"
"runtime/debug"
"sort"
"strconv"
"strings"
text "text/template"
"github.com/pkg/errors"
)
// Plain text templates
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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"))))
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// Template collections
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var textTemplates = make(map[string]*text.Template, 0)
var htmlTemplates = make(map[string]*html.Template, 0)
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// Used by resolveResponseContentType
var acceptHeaderMediaRangeRegex = regexp.MustCompile(`^\s*([^()<>@,;:\\"/\[\]?.=]+)/([^()<>@,;:\\"/\[\]?.=]+)\s*$`)
var acceptHeaderAcceptParamsRegex = regexp.MustCompile(`^\s*(\w+)=([A-Za-z0-9.-]+)\s*$`)
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var acceptHeaderWeight = regexp.MustCompile(`^\s*q=0(?:\.([0-9]{0,3}))|1(?:\.0{0,3})\s*$`)
// HTML templates
func init() {
for _, tmplPath := range AssetNames() {
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if mustMatch("templates/txt/*.txt.tmpl", tmplPath) {
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base := text.Must(textBaseTemplate.Clone())
tmpl, err := base.Parse(string(MustAsset(tmplPath)))
if err != nil {
panic(errors.Wrapf(err, "parsing %v", tmplPath))
}
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tmplName := strings.TrimSuffix(filepath.Base(tmplPath), ".txt.tmpl")
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textTemplates[tmplName] = tmpl
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continue
}
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if mustMatch("templates/html/*.html.tmpl", tmplPath) {
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base := html.Must(htmlBaseTemplate.Clone())
tmpl, err := base.Parse(string(MustAsset(tmplPath)))
if err != nil {
panic(errors.Wrapf(err, "parsing %v", tmplPath))
}
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tmplName := strings.TrimSuffix(filepath.Base(tmplPath), ".html.tmpl")
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htmlTemplates[tmplName] = tmpl
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continue
}
}
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// Sanity check. Both maps should not be empty
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if len(textTemplates) == 0 || len(htmlTemplates) == 0 {
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panic("template loading failed")
}
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}
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) {
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panic(errors.Wrapf(err, "parsing of %v failed", tmplName))
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}
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func render(w http.ResponseWriter, r *http.Request, tmplName string, data map[string]interface{}) {
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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)
}
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// Add the request to the template data
data["Request"] = r
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switch contentType {
case "text/plain":
w.Header().Set("Content-Type", "text/plain")
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tmpl := textTemplates[tmplName]
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if tmpl == nil {
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err = fmt.Errorf("'%v' not in textTemplates", tmplName)
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break
}
err = tmpl.Execute(w, data)
case "text/html":
w.Header().Set("Content-Type", "text/html")
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tmpl := htmlTemplates[tmplName]
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if tmpl == nil {
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err = fmt.Errorf("'%v' not in htmlTemplates", tmplName)
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break
}
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// Construct a (lazy) plain-text view for inclusion in <pre>
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data["Pre"] = func() string {
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tmpl := textTemplates[tmplName]
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if tmpl == nil {
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panic(fmt.Errorf("'%v' not in textTemplates", tmplName))
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}
var buf bytes.Buffer
if err := tmpl.Execute(&buf, data); err != nil {
panic(err)
}
return buf.String()
}
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err = tmpl.Execute(w, data)
default:
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// Fall back to plain text without template
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w.WriteHeader(http.StatusNotAcceptable)
io.WriteString(w, "could not resolve an acceptable content-type\n")
}
if err != nil {
panic(err)
}
}
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func renderError(w http.ResponseWriter, r *http.Request, status int, msg string) {
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w.WriteHeader(status)
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render(w, r, "error", map[string]interface{}{"Message": msg})
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}
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func renderInternalServerError(w http.ResponseWriter, r *http.Request, err interface{}) {
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msg := fmt.Sprintf("internal server error: %v", err)
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renderError(w, r, http.StatusInternalServerError, msg)
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}
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// 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 := 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
}