reprogl

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package views
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import (
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	"crypto/sha256"
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	"encoding/base64"
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	"fmt"
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	"html/template"
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	"os"
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	"strconv"
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	"strings"
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	"xelbot.com/reprogl/container"
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)
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var fileHashes = make(map[string]string)
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func cdnBase() string {
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	return container.GetConfig().CDNBaseURL
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}
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func assetTag(file string) template.HTML {
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	var (
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		tmpl    string
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		result  string
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		subPath string
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		ext     string
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	)
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	result, ok := fileHashes[file]
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	if ok {
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		return template.HTML(result)
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	}
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	if strings.HasSuffix(file, ".css") {
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		tmpl = `<link rel="stylesheet" href="%s" integrity="%s" crossorigin="anonymous">`
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		subPath = file[:len(file)-3]
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		ext = ".css"
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	} else if strings.HasSuffix(file, ".js") {
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		tmpl = `<script src="%s" integrity="%s" crossorigin="anonymous"></script>`
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		subPath = file[:len(file)-2]
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		ext = ".js"
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	} else {
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		tmpl = `<unknown src="%s" integrity="%s"/>`
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		subPath = file
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		ext = ".?"
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	}
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	hash := subresourceIntegrity(file)
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	timeBasedPart := timeBased(file)
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	result = fmt.Sprintf(tmpl, cdnBase()+"/"+subPath+timeBasedPart+ext, hash)
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	if !container.IsDevMode() {
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		fileHashes[file] = result
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	}
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	return template.HTML(result)
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}
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func subresourceIntegrity(file string) string {
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	var n int
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	f, err := os.Open("./public/" + file)
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	if err != nil {
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		return ""
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	}
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	defer f.Close()
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	hash := sha256.New()
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	bytes := make([]byte, 1024)
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	for {
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		n, err = f.Read(bytes)
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		if err != nil {
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			break
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		}
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		hash.Write(bytes[:n])
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	}
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	return "sha256-" + base64.StdEncoding.EncodeToString(hash.Sum(nil))
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}
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func timeBased(file string) string {
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	fileInfo, err := os.Stat("./public/" + file)
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	if err != nil {
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		return "v999"
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	}
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	modificatedAt := fileInfo.ModTime()
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	return fmt.Sprintf(
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		"v%d%s%s%s%s",
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		modificatedAt.Year()%100,
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		zeroPad(modificatedAt.YearDay(), 3),
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		zeroPad(modificatedAt.Hour(), 2),
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		zeroPad(modificatedAt.Minute(), 2),
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		zeroPad(modificatedAt.Second(), 2),
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	)
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}
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func zeroPad(i, width int) string {
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	istring := strconv.Itoa(i)
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	return strings.Repeat("0", width-len(istring)) + istring
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}
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