17twenty/demo.tmpl.html

## demo.tmpl.html
<html>
  <head>
    <script src="https://unpkg.com/htmx.org@1.8.0"></script>
    <script src="https://cdn.tailwindcss.com"></script>
    <title>Template Fragment Example</title>
  </head>
  <body>

    <div hx-get="/notifications" hx-trigger="load" hx-swap="outerHTML"><!-- I GET REPLACED --></div>

    <h1>Template Fragment Example</h1>
    <p>
      This page demonstrates how to create and serve
      <a href="https://htmx.org/essays/template-fragments/"
        >template fragments</a
      >
      using the
      <a href="https://pkg.go.dev/text/template">built-in template package</a>
      in Go.
    </p>
    <p>
      This is accomplished by using the "block" action in the template, which
      lets you define and execute a sub-template in a single step.
    </p>
    <!-- Here's the fragment.  We can target it by executing the "buttonOnly" template. -->
    {{block "buttonOnly" .}}
    <button
      hx-get="/?counter={{.next}}&template=buttonOnly"
      hx-swap="outerHTML"
    >
      This Button Has Been Clicked {{.counter}} Times
    </button>
    {{end}}
  </body>
</html>

## flash.go
package main

import (
	"bytes"
	"encoding/base64"
	"encoding/gob"
	"log"
	"net/http"
	"time"
)

type Flash struct {
	Type    string // Warning | Success | Info
	Title   string
	Content string
}

func init() {
	gob.Register(&Flash{})
}

func SetFlash(w http.ResponseWriter, flashType string, title string, content string) {

	// Initialize a buffer to hold the gob data.
	var buf bytes.Buffer
	f := Flash{
		Type:    flashType,
		Title:   title,
		Content: content,
	}

	err := gob.NewEncoder(&buf).Encode(&f)
	if err != nil {
		log.Println(err)
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	enc := base64.URLEncoding.EncodeToString(buf.Bytes())

	c := &http.Cookie{Name: "flash", Value: enc}
	http.SetCookie(w, c)
}

func GetFlash(w http.ResponseWriter, r *http.Request) (Flash, error) {
	var f Flash
	c, err := r.Cookie("flash")
	if err != nil {
		switch err {
		case http.ErrNoCookie:
			return f, nil
		default:
			return f, err
		}
	}

	// No point worrying about bad data. Just move on past.
	uDec, _ := base64.URLEncoding.DecodeString(c.Value)

	if err := gob.NewDecoder(bytes.NewReader(uDec)).Decode(&f); err != nil {
		log.Println(err)
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return Flash{}, err
	}

	// "Delete" by setting expired cookie
	http.SetCookie(w, &http.Cookie{Name: "flash", MaxAge: -1, Expires: time.Unix(1, 0)})
	return f, nil
}

## flash.tmpl.html
<div
  class="fixed top-0 z-10 flex w-full flex-col items-center justify-center space-y-2"
>
  {{ if eq .Type "Warning" }}
  <div
    class="border-l-8 border-orange-500 bg-orange-100 p-4 text-sm text-orange-700 shadow-lg"
    role="alert"
    style="cursor: pointer"
    onclick="this.remove()"
  >
    <p class="font-bold">{{ .Title }}</p>
    <p>{{ .Content }}</p>
  </div>
  {{end}} {{ if eq .Type "Success" }}
  <div
    class="border-l-8 border-green-500 bg-green-100 p-4 text-sm text-green-600 shadow-lg"
    role="alert"
    style="cursor: pointer"
    onclick="this.remove()"
  >
    <p class="font-bold">{{ .Title }}</p>
    <p>{{ .Content }}</p>
  </div>
  {{end}} {{ if eq .Type "Info" }}
  <div
    class="border-l-8 border-blue-500 bg-blue-100 p-4 text-sm text-blue-600 shadow-lg"
    role="alert"
    style="cursor: pointer"
    onclick="this.remove()"
  >
    <p class="font-bold">{{ .Title }}</p>
    <p>{{ .Content }}</p>
  </div>
  {{end}}
</div>

## main.go
...

	// Flash demo
	unprotectedRouter.HandleFunc("/notifications", func(w http.ResponseWriter, r *http.Request) {
		var tpl = template.Must(template.ParseFiles("templates/flash.tmpl.html"))
		f, err := GetFlash(w, r)

		if err != nil {
			log.Println("Error received", err)
		}
		tpl.Execute(w, f)
	})

	unprotectedRouter.HandleFunc("/test", func(w http.ResponseWriter, r *http.Request) {
		var tpl = template.Must(template.ParseFiles("templates/login.tmpl.html"))
		SetFlash(w, "Warning", "This is a warning", "This is the contents - i was set via Flash()")
		tpl.Execute(w, nil)
	})

	unprotectedRouter.HandleFunc("/test1", func(w http.ResponseWriter, r *http.Request) {
		var tpl = template.Must(template.ParseFiles("templates/demo.tmpl.html"))
		tpl.Execute(w, nil)
	})
...
	<html>
	<head>
	<script src="https://unpkg.com/htmx.org@1.8.0"></script>
	<script src="https://cdn.tailwindcss.com"></script>
	<title>Template Fragment Example</title>
	</head>
	<body>

	<div hx-get="/notifications" hx-trigger="load" hx-swap="outerHTML"><!-- I GET REPLACED --></div>

	<h1>Template Fragment Example</h1>
	<p>
	This page demonstrates how to create and serve
	<a href="https://htmx.org/essays/template-fragments/"
	>template fragments</a
	>
	using the
	<a href="https://pkg.go.dev/text/template">built-in template package</a>
	in Go.
	</p>
	<p>
	This is accomplished by using the "block" action in the template, which
	lets you define and execute a sub-template in a single step.
	</p>
	<!-- Here's the fragment. We can target it by executing the "buttonOnly" template. -->
	{{block "buttonOnly" .}}
	<button
	hx-get="/?counter={{.next}}&template=buttonOnly"
	hx-swap="outerHTML"
	>
	This Button Has Been Clicked {{.counter}} Times
	</button>
	{{end}}
	</body>
	</html>
	package main

	import (
	"bytes"
	"encoding/base64"
	"encoding/gob"
	"log"
	"net/http"
	"time"
	)

	type Flash struct {
	Type string // Warning \| Success \| Info
	Title string
	Content string
	}

	func init() {
	gob.Register(&Flash{})
	}

	func SetFlash(w http.ResponseWriter, flashType string, title string, content string) {

	// Initialize a buffer to hold the gob data.
	var buf bytes.Buffer
	f := Flash{
	Type: flashType,
	Title: title,
	Content: content,
	}

	err := gob.NewEncoder(&buf).Encode(&f)
	if err != nil {
	log.Println(err)
	http.Error(w, "Internal Server Error", http.StatusInternalServerError)
	return
	}

	enc := base64.URLEncoding.EncodeToString(buf.Bytes())

	c := &http.Cookie{Name: "flash", Value: enc}
	http.SetCookie(w, c)
	}

	func GetFlash(w http.ResponseWriter, r *http.Request) (Flash, error) {
	var f Flash
	c, err := r.Cookie("flash")
	if err != nil {
	switch err {
	case http.ErrNoCookie:
	return f, nil
	default:
	return f, err
	}
	}

	// No point worrying about bad data. Just move on past.
	uDec, _ := base64.URLEncoding.DecodeString(c.Value)

	if err := gob.NewDecoder(bytes.NewReader(uDec)).Decode(&f); err != nil {
	log.Println(err)
	http.Error(w, "Internal Server Error", http.StatusInternalServerError)
	return Flash{}, err
	}

	// "Delete" by setting expired cookie
	http.SetCookie(w, &http.Cookie{Name: "flash", MaxAge: -1, Expires: time.Unix(1, 0)})
	return f, nil
	}
	<div
	class="fixed top-0 z-10 flex w-full flex-col items-center justify-center space-y-2"
	>
	{{ if eq .Type "Warning" }}
	<div
	class="border-l-8 border-orange-500 bg-orange-100 p-4 text-sm text-orange-700 shadow-lg"
	role="alert"
	style="cursor: pointer"
	onclick="this.remove()"
	>
	<p class="font-bold">{{ .Title }}</p>
	<p>{{ .Content }}</p>
	</div>
	{{end}} {{ if eq .Type "Success" }}
	<div
	class="border-l-8 border-green-500 bg-green-100 p-4 text-sm text-green-600 shadow-lg"
	role="alert"
	style="cursor: pointer"
	onclick="this.remove()"
	>
	<p class="font-bold">{{ .Title }}</p>
	<p>{{ .Content }}</p>
	</div>
	{{end}} {{ if eq .Type "Info" }}
	<div
	class="border-l-8 border-blue-500 bg-blue-100 p-4 text-sm text-blue-600 shadow-lg"
	role="alert"
	style="cursor: pointer"
	onclick="this.remove()"
	>
	<p class="font-bold">{{ .Title }}</p>
	<p>{{ .Content }}</p>
	</div>
	{{end}}
	</div>
	...

	// Flash demo
	unprotectedRouter.HandleFunc("/notifications", func(w http.ResponseWriter, r *http.Request) {
	var tpl = template.Must(template.ParseFiles("templates/flash.tmpl.html"))
	f, err := GetFlash(w, r)

	if err != nil {
	log.Println("Error received", err)
	}
	tpl.Execute(w, f)
	})

	unprotectedRouter.HandleFunc("/test", func(w http.ResponseWriter, r *http.Request) {
	var tpl = template.Must(template.ParseFiles("templates/login.tmpl.html"))
	SetFlash(w, "Warning", "This is a warning", "This is the contents - i was set via Flash()")
	tpl.Execute(w, nil)
	})

	unprotectedRouter.HandleFunc("/test1", func(w http.ResponseWriter, r *http.Request) {
	var tpl = template.Must(template.ParseFiles("templates/demo.tmpl.html"))
	tpl.Execute(w, nil)
	})
	...