fix urls in custom email/announcements

Uses a nasty algorithm found in stripmd.go to change all occurrences
of '[linktext](link)' to just 'link' before passing to a decent markdown
stripper.

email.go

@@ -18,7 +18,6 @@ import (
 	jEmail "github.com/jordan-wright/email"
 	"github.com/knz/strtime"
 	"github.com/mailgun/mailgun-go/v4"
-	stripmd "github.com/writeas/go-strip-markdown"
 )
 
 // implements email sending, right now via smtp or mailgun.
@@ -260,7 +259,7 @@ func (emailer *Emailer) constructTemplate(subject, md string, app *appContext) (
 	email := &Email{subject: subject}
 	renderer := html.NewRenderer(html.RendererOptions{Flags: html.Smartypants})
 	html := markdown.ToHTML([]byte(md), nil, renderer)
-	text := strings.TrimPrefix(strings.TrimSuffix(stripmd.Strip(md), "</p>"), "<p>")
+	text := stripMarkdown(md)
 	message := app.config.Section("email").Key("message").String()
 	var err error
 	email.html, email.text, err = emailer.construct(app, "template_email", "email_", map[string]interface{}{

stripmd.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"strings"
+
+	stripmd "github.com/writeas/go-strip-markdown"
+)
+
+func stripMarkdown(md string) string {
+	// Search for markdown-formatted urls, and replace them with just the url, then use a library to strip any traces of markdown. You'll need some eyebleach after this.
+	foundOpenSquare := false
+	openSquare := -1
+	openBracket := -1
+	closeBracket := -1
+	openSquares := []int{}
+	closeBrackets := []int{}
+	links := []string{}
+	foundOpen := false
+	for i, c := range md {
+		if !foundOpenSquare && !foundOpen && c != '[' && c != ']' {
+			continue
+		}
+		if c == '[' {
+			foundOpenSquare = true
+			openSquare = i
+		} else if c == ']' {
+			if md[i+1] == '(' {
+				foundOpenSquare = false
+				foundOpen = true
+				openBracket = i + 1
+				continue
+			}
+		} else if c == ')' {
+			closeBracket = i
+			openSquares = append(openSquares, openSquare)
+			closeBrackets = append(closeBrackets, closeBracket)
+			links = append(links, md[openBracket+1:closeBracket])
+			openBracket = -1
+			closeBracket = -1
+			openSquare = -1
+			foundOpenSquare = false
+			foundOpen = false
+		}
+	}
+	fullLinks := make([]string, len(openSquares))
+	for i := range openSquares {
+		fullLinks[i] = md[openSquares[i] : closeBrackets[i]+1]
+	}
+	for i, _ := range openSquares {
+		md = strings.Replace(md, fullLinks[i], links[i], 1)
+	}
+	return strings.TrimPrefix(strings.TrimSuffix(stripmd.Strip(md), "</p>"), "<p>")
+}