From 58c81bfac52b8f83957e80ffa9eaf895bba68b3a Mon Sep 17 00:00:00 2001
From: Peter Stuifzand <peter@stuifzand.eu>
Date: Fri, 13 Aug 2021 08:34:31 +0200
Subject: [PATCH] Add title parsing

---
 link/parser.go | 116 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100644 link/parser.go

diff --git a/link/parser.go b/link/parser.go
new file mode 100644
index 0000000..36617e6
--- /dev/null
+++ b/link/parser.go
@@ -0,0 +1,116 @@
+package link
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"io"
+	"strings"
+)
+
+type Tree struct {
+	cur      rng
+	children []Tree
+}
+
+func (t Tree) text(inp string) string {
+	return inp[t.cur.start:t.cur.end]
+}
+
+type rng struct {
+	start, end int
+	typ        string
+}
+
+type Parser struct {
+	markers []int
+	ranges  []rng
+	stack   []Tree
+}
+
+func (p *Parser) pushMarker(start int) {
+	p.markers = append(p.markers, start)
+	p.stack = append(p.stack, Tree{})
+}
+
+func (p *Parser) popMarker(end int, typ string) {
+	start := p.markers[len(p.markers)-1]
+	p.markers = p.markers[:len(p.markers)-1]
+	cur := rng{start, end, typ}
+	top := p.stack[len(p.stack)-1]
+	top.cur = cur
+	p.stack = p.stack[:len(p.stack)-1]
+	p.stack[len(p.stack)-1].children = append(p.stack[len(p.stack)-1].children, top)
+	p.ranges = append(p.ranges, cur)
+}
+func (p *Parser) output() Tree {
+	return p.stack[0].children[0]
+}
+
+func ShowTree(input string, root Tree, indent int) {
+	if root.cur.start != root.cur.end {
+		fmt.Printf("%s + (%s, %d-%d) %q\n", strings.Repeat(" |", indent), root.cur.typ, root.cur.start, root.cur.end, input[root.cur.start:root.cur.end])
+	} else {
+		indent -= 1
+	}
+	for _, c := range root.children {
+		ShowTree(input, c, indent+1)
+	}
+}
+
+func formatTitle(w io.Writer, input string, root Tree, indent int) {
+	typ := root.cur.typ
+	text := input[root.cur.start:root.cur.end]
+	if typ == "text" {
+		w.Write([]byte(text))
+	}
+	if typ == "link" {
+		w.Write([]byte(fmt.Sprintf(`<a href="%s">`, root.children[1].text(input))))
+		w.Write([]byte(text))
+		w.Write([]byte(`</a>`))
+		return
+	}
+
+	for _, c := range root.children {
+		formatTitle(w, input, c, indent+1)
+	}
+}
+
+func FormatHtmlTitle(input string) template.HTML {
+	p := Parser{}
+	root := p.Parse(input)
+	sb := &bytes.Buffer{}
+	formatTitle(sb, input, root, 0)
+	return template.HTML(sb.String())
+}
+
+func (p *Parser) Parse(input string) Tree {
+	p.stack = append(p.stack, Tree{})
+
+	i := 0
+
+	p.pushMarker(i)
+	for i < len(input) {
+		p.pushMarker(i)
+		for i < len(input) && (input[i] != '[' && input[i] != ']') {
+			i++
+		}
+		p.popMarker(i, "text")
+		if i+2 <= len(input) && input[i:i+2] == "[[" {
+			p.pushMarker(i)
+			p.pushMarker(i)
+			i += 2
+			p.popMarker(i, "start link tag")
+			p.pushMarker(i)
+		} else if i+2 <= len(input) && input[i:i+2] == "]]" {
+			p.popMarker(i, "link text")
+			p.pushMarker(i)
+			i += 2
+			p.popMarker(i, "end link tag")
+			p.popMarker(i, "link")
+		}
+	}
+	p.popMarker(i, "full text")
+
+	return p.output()
+}