feat(markdown): support external link and image (without source)

1 files changed, 141 insertions, 0 deletions

diff --git a/mardown/ast_external.go b/mardown/ast_external.go
new file mode 100644
index 0000000..87fb880
--- /dev/null
+++ b/mardown/ast_external.go
@@ -0,0 +1,141 @@
+package mardown
+
+import (
+	"fmt"
+	"html/template"
+)
+
+type astLink struct {
+	content block
+	href    block
+}
+
+func (a *astLink) Eval() (template.HTML, error) {
+	content, err := a.content.Eval()
+	if err != nil {
+		return "", err
+	}
+	href, err := a.href.Eval()
+	if err != nil {
+		return "", err
+	}
+	return template.HTML(fmt.Sprintf(`<a href="%s">%s</a>`, href, content)), nil
+}
+
+type astImage struct {
+	alt    block
+	src    block
+	source *astParagraph
+}
+
+func (a *astImage) Eval() (template.HTML, error) {
+	alt, err := a.alt.Eval()
+	if err != nil {
+		return "", err
+	}
+	src, err := a.src.Eval()
+	if err != nil {
+		return "", err
+	}
+	if a.source == nil {
+		return template.HTML(fmt.Sprintf(`<figure><img alt="%s" src="%s"></figure>`, alt, src)), nil
+	}
+	source, err := a.source.Eval()
+	if err != nil {
+		return "", err
+	}
+	return template.HTML(fmt.Sprintf(`<figure><img alt="%s" src="%s"><figcaption>%s</figcaption></figure>`, alt, src, source)), nil
+}
+
+func external(lxs *lexers) (block, error) {
+	tp := lxs.Current().Value
+	if !lxs.Next() {
+		return astLiteral(tp), nil
+	}
+	lxs.Before() // because we call Next
+	var b block
+	var err error
+	switch tp {
+	case "![":
+		b, err = image(lxs)
+	case "[":
+		b, err = link(lxs)
+	default:
+		b = astLiteral(tp)
+	}
+	return b, err
+}
+
+func link(lxs *lexers) (block, error) {
+	lk := new(astLink)
+	start := lxs.current
+	content, href, _, ok := parseExternal(lxs, 1)
+	if !ok {
+		return reset(lxs, start), nil
+	}
+	lk.content = astLiteral(content)
+	lk.href = astLiteral(href)
+	return lk, nil
+}
+
+func image(lxs *lexers) (block, error) {
+	img := new(astImage)
+	start := lxs.current
+	alt, src, _, ok := parseExternal(lxs, 2)
+	if !ok {
+		return reset(lxs, start), nil
+	}
+	img.alt = astLiteral(alt)
+	img.src = astLiteral(src)
+	//img.source = astLiteral(source)
+	return img, nil
+}
+
+func parseExternal(lxs *lexers, maxBreak int) (string, string, string, bool) {
+	next := false
+	var s string
+	var first string
+	var end string
+	n := 0
+	for lxs.Next() && n < maxBreak {
+		switch lxs.Current().Type {
+		case lexerBreak:
+			n++
+		case lexerExternal:
+			if n > 0 && (first == "" || end == "") {
+				return "", "", "", false
+			}
+			n = 0
+			if !next {
+				if lxs.Current().Value != "](" || !lxs.Next() {
+					return "", "", "", false
+				}
+				lxs.Before() // because we called Next
+				first = s
+				s = ""
+				next = true
+			} else {
+				if lxs.Current().Value != ")" {
+					return "", "", "", false
+				}
+				if maxBreak == 1 {
+					return first, s, "", true
+				}
+				end = s
+				s = ""
+			}
+		default:
+			n = 0
+			s += lxs.Current().Value
+		}
+	}
+	if maxBreak == 1 {
+		return "", "", "", false
+	}
+	return first, end, s, true
+}
+
+func reset(lxs *lexers, start int) block {
+	lxs.current = start
+	return astLiteral(lxs.Current().Value)
+}