From 7cf9c53f8a0f4413345e7ffe7853006df07316c3 Mon Sep 17 00:00:00 2001
From: Maxim Lebedev <git@toby3d.me>
Date: Fri, 10 Nov 2023 02:14:15 +0600
Subject: [PATCH] :sparkles: Created markdownify transform template util

---
 go.mod                                       |  4 +
 go.sum                                       |  5 ++
 internal/templateutil/transform/transform.go | 82 ++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 internal/templateutil/transform/transform.go

diff --git a/go.mod b/go.mod
index bb8cfd4..851aa9c 100644
--- a/go.mod
+++ b/go.mod
@@ -10,6 +10,10 @@ require (
 
 require github.com/google/go-cmp v0.6.0
 
+require github.com/yuin/goldmark v1.6.0
+
+require github.com/yuin/goldmark-emoji v1.0.2
+
 require (
 	github.com/BurntSushi/toml v0.3.1 // indirect
 	gopkg.in/yaml.v2 v2.3.0 // indirect
diff --git a/go.sum b/go.sum
index e42b668..1b9e005 100644
--- a/go.sum
+++ b/go.sum
@@ -17,6 +17,11 @@ github.com/valyala/fasthttp v1.30.0/go.mod h1:2rsYD01CKFrjjsvFxx75KlEUNpWNBY9JWD
 github.com/valyala/quicktemplate v1.7.0 h1:LUPTJmlVcb46OOUY3IeD9DojFpAVbsG+5WFTcjMJzCM=
 github.com/valyala/quicktemplate v1.7.0/go.mod h1:sqKJnoaOF88V07vkO+9FL8fb9uZg/VPSJnLYn+LmLk8=
 github.com/valyala/tcplisten v1.0.0/go.mod h1:T0xQ8SeCZGxckz9qRXTfG43PvQ/mcWh7FwZEA7Ioqkc=
+github.com/yuin/goldmark v1.3.7/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
+github.com/yuin/goldmark v1.6.0 h1:boZcn2GTjpsynOsC0iJHnBWa4Bi0qzfJjthwauItG68=
+github.com/yuin/goldmark v1.6.0/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+github.com/yuin/goldmark-emoji v1.0.2 h1:c/RgTShNgHTtc6xdz2KKI74jJr6rWi7FPgnP9GAsO5s=
+github.com/yuin/goldmark-emoji v1.0.2/go.mod h1:RhP/RWpexdp+KHs7ghKnifRoIs/Bq4nDS7tRbCkOwKY=
 golang.org/x/crypto v0.0.0-20210513164829-c07d793c2f9a/go.mod h1:P+XmwS30IXTQdn5tA2iutPOUgjI07+tq3H3K9MVA1s8=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.0.0-20210510120150-4163338589ed/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
diff --git a/internal/templateutil/transform/transform.go b/internal/templateutil/transform/transform.go
new file mode 100644
index 0000000..f3bfa53
--- /dev/null
+++ b/internal/templateutil/transform/transform.go
@@ -0,0 +1,82 @@
+package transform
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"html/template"
+	"reflect"
+
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark-emoji"
+	"github.com/yuin/goldmark/extension"
+	"github.com/yuin/goldmark/parser"
+	renderer "github.com/yuin/goldmark/renderer/html"
+)
+
+type Namespace struct {
+	markdown goldmark.Markdown
+}
+
+var ErrMarkdownify error = errors.New("unsupported input type for Markdownify")
+
+func New() *Namespace {
+	md := goldmark.New(
+		// goldmark.WithParser(),
+		// goldmark.WithRenderer(),
+		goldmark.WithParserOptions(
+			parser.WithAutoHeadingID(),
+			parser.WithAttribute(),
+		),
+		goldmark.WithRendererOptions(
+			renderer.WithUnsafe(),
+		),
+		goldmark.WithExtensions(
+			extension.Table,
+			extension.Strikethrough,
+			extension.Linkify,
+			extension.TaskList,
+			extension.DefinitionList,
+			extension.Footnote,
+			extension.NewTypographer(
+				extension.WithTypographicSubstitutions(extension.TypographicSubstitutions{
+					extension.LeftDoubleQuote:  []byte(`„`),
+					extension.LeftAngleQuote:   []byte(`«`),
+					extension.RightDoubleQuote: []byte(`“`),
+					extension.RightAngleQuote:  []byte(`»`),
+				}),
+			),
+			emoji.Emoji,
+		),
+	)
+
+	return &Namespace{
+		markdown: md,
+	}
+}
+
+func (ns *Namespace) Markdownify(v reflect.Value) (template.HTML, error) {
+	var err error
+
+	buf := bytes.NewBuffer(nil)
+
+	switch v.Kind() {
+	default:
+		return "", ErrMarkdownify
+	case reflect.Slice:
+		switch v.Type().Elem().Kind() {
+		default:
+			return "", ErrMarkdownify
+		case reflect.Uint8:
+			err = ns.markdown.Convert(v.Bytes(), buf)
+		}
+	case reflect.String:
+		err = ns.markdown.Convert(v.Bytes(), buf)
+	}
+
+	if err != nil {
+		return "", fmt.Errorf("cannot convert input into markdown: %w", err)
+	}
+
+	return template.HTML(buf.String()), nil
+}