From 86639f865a9a38ced67eb9d80b915436e0819a77 Mon Sep 17 00:00:00 2001
From: Mike Crute <mike@crute.us>
Date: Wed, 18 Oct 2023 12:43:51 -0700
Subject: echo: add some template functions

---
 echo/tplfuncs/embed_csp.go   | 75 ++++++++++++++++++++++++++++++++++++++++++++
 echo/tplfuncs/humanize.go    | 23 ++++++++++++++
 echo/tplfuncs/picture_tag.go | 16 ++++++++++
 3 files changed, 114 insertions(+)
 create mode 100644 echo/tplfuncs/embed_csp.go
 create mode 100644 echo/tplfuncs/humanize.go
 create mode 100644 echo/tplfuncs/picture_tag.go

diff --git a/echo/tplfuncs/embed_csp.go b/echo/tplfuncs/embed_csp.go
new file mode 100644
index 0000000..44930c4
--- /dev/null
+++ b/echo/tplfuncs/embed_csp.go
@@ -0,0 +1,75 @@
+package tplfuncs
+
+import (
+	"fmt"
+	"html/template"
+	"io"
+	"io/fs"
+	"path"
+
+	"code.crute.us/mcrute/golib/echo/middleware"
+
+	"github.com/labstack/echo/v4"
+)
+
+type TemplateEmbeder struct {
+	templateStore fs.FS
+}
+
+func (t *TemplateEmbeder) ConfigureTemplateStore(store fs.FS) {
+	t.templateStore = store
+}
+
+func (t *TemplateEmbeder) Embed(filename string) ([]byte, error) {
+	if t.templateStore == nil {
+		return nil, fmt.Errorf("EmbedWithCSP: has not been setup with template store")
+	}
+
+	fd, err := t.templateStore.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer fd.Close()
+
+	fc, err := io.ReadAll(fd)
+	if err != nil {
+		return nil, err
+	}
+
+	return fc, nil
+}
+
+func (t *TemplateEmbeder) EmbedHTML(filename string) (any, error) {
+	d, err := t.Embed(filename)
+	return template.HTML(d), err
+}
+
+func (t *TemplateEmbeder) embedWithCSP(filename string, c echo.Context) ([]byte, error) {
+	fc, err := t.Embed(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	csp := &middleware.ContentSecurityPolicyConfig{}
+	switch path.Ext(filename) {
+	case ".js", ".json":
+		csp.ScriptSrc = []middleware.CSPDirective{
+			middleware.CSPSha256FromBytes(fc),
+		}
+	case ".css":
+		csp.StyleSrc = []middleware.CSPDirective{
+			middleware.CSPSha256FromBytes(fc),
+		}
+	default:
+		return nil, fmt.Errorf("EmbedWithCSP: file %s can not be embedded", filename)
+	}
+
+	middleware.ExtendCSP(c, csp)
+
+	return fc, nil
+}
+
+func (t *TemplateEmbeder) EmbedJSWithCSP(filename string, c echo.Context) (any, error) {
+	d, err := t.embedWithCSP(filename, c)
+	return template.JS(d), err
+}
diff --git a/echo/tplfuncs/humanize.go b/echo/tplfuncs/humanize.go
new file mode 100644
index 0000000..4fc47a3
--- /dev/null
+++ b/echo/tplfuncs/humanize.go
@@ -0,0 +1,23 @@
+package tplfuncs
+
+import (
+	"fmt"
+	"strings"
+)
+
+// JoinEnglish renders a list of strings with commas between them and if
+// there are three or more words will include the word "and" before the
+// final word.
+func JoinEnglish(words []string) string {
+	switch len(words) {
+	case 0:
+		return ""
+	case 1:
+		return words[0]
+	case 2:
+		return fmt.Sprintf("%s and %s", words[0], words[1])
+	default:
+		base := strings.Join(words[:len(words)-1], ", ")
+		return fmt.Sprintf("%s, and %s", base, words[len(words)-1])
+	}
+}
diff --git a/echo/tplfuncs/picture_tag.go b/echo/tplfuncs/picture_tag.go
new file mode 100644
index 0000000..ddec4aa
--- /dev/null
+++ b/echo/tplfuncs/picture_tag.go
@@ -0,0 +1,16 @@
+package tplfuncs
+
+import (
+	"fmt"
+	"html/template"
+)
+
+// RenderPictureTag renders a picture tag with a webp and jpeg source
+// and alt text.
+func RenderPictureTag(img, alt string) template.HTML {
+	return template.HTML(fmt.Sprintf(`<picture>
+	<source srcset="%s.webp" type="image/webp" />
+	<source srcset="%s.jpg" type="image/jpeg" />
+	<img src="%s.jpg" alt="%s" loading="lazy" />
+</picture>`, img, img, img, alt))
+}
-- 
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