Add link metadata fetching package

vendor/github.com/golang-commonmark/markdown/linkify/email.go

@@ -0,0 +1,93 @@
+// Copyright 2015 The Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package linkify
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+func findEmailStart(s string, start int) (_ int, _ bool) {
+	end := start
+	allowDot := false
+	for end >= 0 {
+		b := s[end]
+		switch {
+		case emailcs[b]:
+			allowDot = true
+		case b == '.':
+			if !allowDot {
+				return
+			}
+			allowDot = false
+		default:
+			if end == start {
+				return
+			}
+			if s[end+1] == '.' {
+				return
+			}
+			r, _ := utf8.DecodeLastRuneInString(s[:end+1])
+			if r == utf8.RuneError {
+				return
+			}
+			if !unicode.IsSpace(r) {
+				return
+			}
+			return end + 1, true
+		}
+		end--
+	}
+	if end < start && s[end+1] == '.' {
+		return
+	}
+	return end + 1, true
+}
+
+func findEmailEnd(s string, start int) (_ int, _ bool) {
+	end := start
+	allowDot := false
+loop:
+	for end < len(s) {
+		b := s[end]
+		switch {
+		case emailcs[b]:
+			allowDot = true
+		case b == '.':
+			if !allowDot {
+				return
+			}
+			allowDot = false
+		case b == '@':
+			break loop
+		default:
+			return
+		}
+		end++
+	}
+	if end >= len(s)-5 {
+		return
+	}
+	if end > start && s[end-1] == '.' {
+		return
+	}
+
+	var dot int
+	var ok bool
+	end, dot, ok = findHostnameEnd(s, end+1)
+	if !ok || dot == -1 {
+		return
+	}
+
+	if dot+5 <= len(s) && s[dot+1:dot+5] == "xn--" {
+		return end, true
+	}
+
+	if length := match(s[dot+1:]); dot+length+1 != end {
+		return
+	}
+
+	return end, true
+}