Initial QSfera import

Server/pkg/markdown/markdown.go

@@ -0,0 +1,149 @@
+// Package markdown allows reading and editing Markdown files
+package markdown
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"strings"
+)
+
+// Heading represents a markdown Heading
+type Heading struct {
+	Level   int    // the level of the heading. 1 means it's the H1
+	Content string // the text of the heading
+	Header  string // the heading itself
+}
+
+// MD represents a markdown file
+type MD struct {
+	Headings []Heading
+}
+
+// Bytes returns the markdown as []bytes, ignoring errors
+func (md MD) Bytes() []byte {
+	var b bytes.Buffer
+	_, _ = md.WriteContent(&b)
+	return b.Bytes()
+}
+
+// String returns the markdown as string, ignoring errors
+func (md MD) String() string {
+	var b strings.Builder
+	_, _ = md.WriteContent(&b)
+	return b.String()
+}
+
+// TocBytes returns the table of contents as []byte, ignoring errors
+func (md MD) TocBytes() []byte {
+	var b bytes.Buffer
+	_, _ = md.WriteToc(&b)
+	return b.Bytes()
+}
+
+// TocString returns the table of contents as string, ignoring errors
+func (md MD) TocString() string {
+	var b strings.Builder
+	_, _ = md.WriteToc(&b)
+	return b.String()
+}
+
+// WriteContent writes the MDs content to the given writer
+func (md MD) WriteContent(w io.Writer) (int64, error) {
+	written := int64(0)
+	write := func(s string) error {
+		n, err := w.Write([]byte(s))
+		written += int64(n)
+		return err
+	}
+	for _, h := range md.Headings {
+		if err := write(strings.Repeat("#", h.Level) + " " + h.Header + "\n"); err != nil {
+			return written, err
+		}
+		if len(h.Content) > 0 {
+			if err := write(h.Content); err != nil {
+				return written, err
+			}
+		}
+	}
+	return written, nil
+}
+
+// WriteToc writes the table of contents to the given writer
+func (md MD) WriteToc(w io.Writer) (int64, error) {
+	var written int64
+	for _, h := range md.Headings {
+		if h.Level == 1 {
+			// main title not in toc
+			continue
+		}
+		link := fmt.Sprintf("#%s", toAnchor(h.Header))
+		s := fmt.Sprintf("%s* [%s](%s)\n", strings.Repeat("  ", h.Level-2), h.Header, link)
+		n, err := w.Write([]byte(s))
+		if err != nil {
+			return written, err
+		}
+		written += int64(n)
+	}
+	return written, nil
+}
+
+// NewMD parses a new Markdown
+func NewMD(b []byte) MD {
+	var (
+		md      MD
+		heading Heading
+		content strings.Builder
+	)
+	sendHeading := func() {
+		if heading.Header != "" {
+			heading.Content = content.String()
+			md.Headings = append(md.Headings, heading)
+			content = strings.Builder{}
+		}
+	}
+	parts := strings.Split("\n"+string(b), "\n#")
+	numparts := len(parts) - 1
+	for i, p := range parts {
+		if i == 0 {
+			// omit part before first heading
+			continue
+		}
+
+		all := strings.SplitN(p, "\n", 2)
+		if len(all) != 2 {
+			continue
+		}
+
+		head, con := all[0], all[1]
+		// readd lost "#"
+		heading = headingFromString("#" + head)
+		_, _ = content.WriteString(con)
+		// readd lost "\n" - omit for last part
+		if i < numparts {
+			_, _ = content.WriteString("\n")
+		}
+		// add heading
+		sendHeading()
+	}
+	return md
+}
+
+func headingFromString(s string) Heading {
+	i := strings.LastIndex(s, "#")
+	levs, con := s[:i+1], s[i+1:]
+	return Heading{
+		Level:  len(levs),
+		Header: strings.TrimPrefix(con, " "),
+	}
+}
+
+func toAnchor(header string) string {
+	// Remove everything except letters, numbers, and spaces
+	reg := regexp.MustCompile(`[^a-zA-Z0-9 ]+`)
+	anchor := reg.ReplaceAllString(header, "")
+	// Replace spaces with hyphens and convert to lowercase
+	anchor = strings.ReplaceAll(anchor, " ", "-")
+	return strings.ToLower(anchor)
+}