From c23030733fe4cba578b14ad2c1d1292891202562 Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Thu, 19 Jan 2023 16:02:27 +0100
Subject: Add support for gemtext posts

---
 src/gmi/gemtext.go      | 73 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/gmi/gemtext_test.go | 51 ++++++++++++++++++++++++++++++++++
 src/gmi/gmi.go          |  2 ++
 3 files changed, 126 insertions(+)
 create mode 100644 src/gmi/gemtext.go
 create mode 100644 src/gmi/gemtext_test.go
 create mode 100644 src/gmi/gmi.go

(limited to 'src/gmi')

diff --git a/src/gmi/gemtext.go b/src/gmi/gemtext.go
new file mode 100644
index 0000000..a1136bd
--- /dev/null
+++ b/src/gmi/gemtext.go
@@ -0,0 +1,73 @@
+package gmi
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"path"
+	"regexp"
+	"strings"
+)
+
+func hasImgExt(p string) bool {
+	switch path.Ext(strings.ToLower(p)) {
+	case ".jpg", ".jpeg", ".png", ".gif", ".svg":
+		return true
+	default:
+		return false
+	}
+}
+
+// matches `=> dstURL [optional description]`
+var linkRegexp = regexp.MustCompile(`^=>\s+(\S+)\s*(.*?)\s*$`)
+
+// GemtextToMarkdown reads a gemtext formatted body from the Reader and writes
+// the markdown version of that body to the Writer.
+func GemtextToMarkdown(dst io.Writer, src io.Reader) error {
+
+	bufSrc := bufio.NewReader(src)
+
+	for {
+
+		line, err := bufSrc.ReadString('\n')
+		if err != nil && !errors.Is(err, io.EOF) {
+			return fmt.Errorf("reading: %w", err)
+		}
+
+		last := err == io.EOF
+
+		if match := linkRegexp.FindStringSubmatch(line); len(match) > 0 {
+
+			isImg := hasImgExt(match[1])
+
+			descr := match[2]
+
+			if descr != "" {
+				// ok
+			} else if isImg {
+				descr = "Image"
+			} else {
+				descr = "Link"
+			}
+
+			log.Printf("descr:%q", descr)
+
+			line = fmt.Sprintf("[%s](%s)\n", descr, match[1])
+
+			if isImg {
+				line = "!" + line
+			}
+		}
+
+		if _, err := dst.Write([]byte(line)); err != nil {
+			return fmt.Errorf("writing: %w", err)
+		}
+
+		if last {
+			return nil
+		}
+	}
+
+}
diff --git a/src/gmi/gemtext_test.go b/src/gmi/gemtext_test.go
new file mode 100644
index 0000000..23cb97f
--- /dev/null
+++ b/src/gmi/gemtext_test.go
@@ -0,0 +1,51 @@
+package gmi
+
+import (
+	"bytes"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGemtextToMarkdown(t *testing.T) {
+
+	tests := []struct {
+		in, exp string
+	}{
+		{
+			in:  "",
+			exp: "",
+		},
+		{
+			in:  "=> foo",
+			exp: "[Link](foo)\n",
+		},
+		{
+			in:  "what\n=> foo\n=> bar",
+			exp: "what\n[Link](foo)\n[Link](bar)\n",
+		},
+		{
+			in:  "=> foo description is here   ",
+			exp: "[description is here](foo)\n",
+		},
+		{
+			in:  "=> img.png",
+			exp: "![Image](img.png)\n",
+		},
+		{
+			in:  "=> img.png description is here   ",
+			exp: "![description is here](img.png)\n",
+		},
+	}
+
+	for i, test := range tests {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+
+			got := new(bytes.Buffer)
+			err := GemtextToMarkdown(got, bytes.NewBufferString(test.in))
+			assert.NoError(t, err)
+			assert.Equal(t, test.exp, got.String())
+		})
+	}
+}
diff --git a/src/gmi/gmi.go b/src/gmi/gmi.go
new file mode 100644
index 0000000..358d935
--- /dev/null
+++ b/src/gmi/gmi.go
@@ -0,0 +1,2 @@
+// Package gmi contains utilities for working with gemini and gemtext
+package gmi
-- 
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