feat: articles format option with markdown new default

internal/infrastructure/markdown/markdownRender.go

@@ -0,0 +1,213 @@
+package markdown
+
+import (
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+const (
+	blockSeparator = "\n\n"
+	hardBreak      = "\\\n"
+	bulletMarker   = "- "
+	codeFence      = "```"
+	alignOpen      = `<div style="text-align: `
+	alignOpenEnd   = `">`
+	alignClose     = "</div>"
+)
+
+var textEscaper = strings.NewReplacer(
+	"\\", "\\\\", "*", "\\*", "_", "\\_", "`", "\\`", "[", "\\[", "]", "\\]", "<", "\\<",
+)
+
+var (
+	numberedLineStart = regexp.MustCompile(`^(\d+)([.)])(\s|$)`)
+	markerLineStart   = regexp.MustCompile(`^(>|#{1,6}(\s|$)|[+-](\s|$|-)|=+\s*$)`)
+)
+
+var hrefEscaper = strings.NewReplacer(" ", "%20", "(", "%28", ")", "%29", "<", "%3C", ">", "%3E")
+
+func renderMarkdown(blocks []block) string {
+	return renderBlocks(blocks, blockSeparator)
+}
+
+func renderBlocks(blocks []block, separator string) string {
+	parts := make([]string, 0, len(blocks))
+	for _, b := range blocks {
+		if rendered := renderBlock(b); rendered != "" {
+			parts = append(parts, rendered)
+		}
+	}
+	return strings.Join(parts, separator)
+}
+
+func renderBlock(b block) string {
+	rendered := renderPlainBlock(b)
+	if b.align == "" || rendered == "" {
+		return rendered
+	}
+	return alignOpen + b.align + alignOpenEnd + blockSeparator + rendered + blockSeparator + alignClose
+}
+
+func renderPlainBlock(b block) string {
+	switch b.kind {
+	case kindHeading:
+		return strings.Repeat("#", b.level) + " " + renderInlines(b.inlines)
+	case kindParagraph:
+		return escapeLineStarts(renderInlines(b.inlines))
+	case kindList:
+		return renderList(b)
+	case kindBlockquote:
+		return prefixLines(renderBlocks(b.children, blockSeparator), "> ", ">")
+	case kindCode:
+		return renderCode(b)
+	case kindImage:
+		return "![" + escapeAlt(b.alt) + "](" + hrefEscaper.Replace(b.src) + ")"
+	}
+	return "---"
+}
+
+func escapeLineStarts(text string) string {
+	lines := strings.Split(text, "\n")
+	for index, line := range lines {
+		line = numberedLineStart.ReplaceAllString(line, `$1\$2$3`)
+		if markerLineStart.MatchString(line) {
+			line = `\` + line
+		}
+		lines[index] = line
+	}
+	return strings.Join(lines, "\n")
+}
+
+func renderCode(b block) string {
+	fence := codeFence
+	for strings.Contains(b.text, fence) {
+		fence += "`"
+	}
+	return fence + b.language + "\n" + b.text + "\n" + fence
+}
+
+func escapeAlt(alt string) string {
+	return strings.NewReplacer("[", "\\[", "]", "\\]", "\n", " ").Replace(alt)
+}
+
+func renderList(b block) string {
+	lines := make([]string, 0, len(b.items))
+	for index, item := range b.items {
+		marker := bulletMarker
+		if b.ordered {
+			marker = strconv.Itoa(index+1) + ". "
+		}
+		content := renderBlocks(item, itemSeparator(item))
+		lines = append(lines, marker+indentContinuation(content, len(marker)))
+	}
+	return strings.Join(lines, "\n")
+}
+
+func itemSeparator(item []block) string {
+	textBlocks := 0
+	for _, b := range item {
+		if b.kind != kindList {
+			textBlocks++
+		}
+	}
+	if textBlocks > 1 {
+		return blockSeparator
+	}
+	return "\n"
+}
+
+func indentContinuation(content string, width int) string {
+	indent := strings.Repeat(" ", width)
+	lines := strings.Split(content, "\n")
+	for index := 1; index < len(lines); index++ {
+		if lines[index] != "" {
+			lines[index] = indent + lines[index]
+		}
+	}
+	return strings.Join(lines, "\n")
+}
+
+func prefixLines(content, prefix, emptyPrefix string) string {
+	lines := strings.Split(content, "\n")
+	for index, line := range lines {
+		if line == "" {
+			lines[index] = emptyPrefix
+			continue
+		}
+		lines[index] = prefix + line
+	}
+	return strings.Join(lines, "\n")
+}
+
+func renderInlines(inlines []inline) string {
+	var builder strings.Builder
+	for _, item := range inlines {
+		builder.WriteString(renderInline(item))
+	}
+	return builder.String()
+}
+
+func renderInline(item inline) string {
+	isCode := hasMarkKind(item.marks, markCode)
+	lines := strings.Split(item.text, "\n")
+	for index, line := range lines {
+		lines[index] = wrapMarks(item.marks, line, isCode)
+	}
+	return strings.Join(lines, hardBreak)
+}
+
+func hasMarkKind(marks []mark, kind string) bool {
+	for _, m := range marks {
+		if m.kind == kind {
+			return true
+		}
+	}
+	return false
+}
+
+func wrapMarks(marks []mark, text string, isCode bool) string {
+	core := strings.TrimSpace(text)
+	if core == "" {
+		return text
+	}
+	start := strings.Index(text, core)
+	leading, trailing := text[:start], text[start+len(core):]
+	var wrapped string
+	if isCode {
+		wrapped = inlineCode(core)
+	} else {
+		wrapped = escapeText(core)
+	}
+	for index := len(marks) - 1; index >= 0; index-- {
+		wrapped = applyMark(marks[index], wrapped)
+	}
+	return leading + wrapped + trailing
+}
+
+func inlineCode(text string) string {
+	fence := "`"
+	for strings.Contains(text, fence) {
+		fence += "`"
+	}
+	if strings.HasPrefix(text, "`") || strings.HasSuffix(text, "`") {
+		return fence + " " + text + " " + fence
+	}
+	return fence + text + fence
+}
+
+func applyMark(m mark, text string) string {
+	switch m.kind {
+	case markBold:
+		return "**" + text + "**"
+	case markItalic:
+		return "*" + text + "*"
+	case markLink:
+		return "[" + text + "](" + hrefEscaper.Replace(m.href) + ")"
+	}
+	return text
+}
+
+func escapeText(text string) string {
+	return textEscaper.Replace(text)
+}