echo: add some template functions

3 files changed, 114 insertions, 0 deletions

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))
+}