1//
  2// Copyright (c) 2019 Ted Unangst <tedu@tedunangst.com>
  3//
  4// Permission to use, copy, modify, and distribute this software for any
  5// purpose with or without fee is hereby granted, provided that the above
  6// copyright notice and this permission notice appear in all copies.
  7//
  8// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 14// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15
 16package main
 17
 18import (
 19	"fmt"
 20	"regexp"
 21	"strings"
 22
 23	"golang.org/x/net/html"
 24	"humungus.tedunangst.com/r/webs/synlight"
 25)
 26
 27var re_bolder = regexp.MustCompile(`(^|\W)\*\*([\w\s,.!?':_-]+)\*\*($|\W)`)
 28var re_italicer = regexp.MustCompile(`(^|\W)\*([\w\s,.!?':_-]+)\*($|\W)`)
 29var re_bigcoder = regexp.MustCompile("```(.*)\n?((?s:.*?))\n?```\n?")
 30var re_coder = regexp.MustCompile("`([^`]*)`")
 31var re_quoter = regexp.MustCompile(`(?m:^&gt; (.*)\n?)`)
 32var re_link = regexp.MustCompile(`.?.?https?://[^\s"]+[\w/)!]`)
 33var re_zerolink = regexp.MustCompile(`\[([^]]*)\]\(([^)]*\)?)\)`)
 34
 35var lighter = synlight.New(synlight.Options{Format: synlight.HTML})
 36
 37func markitzero(s string) string {
 38	// prepare the string
 39	s = strings.TrimSpace(s)
 40	s = strings.Replace(s, "\r", "", -1)
 41
 42	// save away the code blocks so we don't mess them up further
 43	var bigcodes, lilcodes []string
 44	s = re_bigcoder.ReplaceAllStringFunc(s, func(code string) string {
 45		bigcodes = append(bigcodes, code)
 46		return "``````"
 47	})
 48	s = re_coder.ReplaceAllStringFunc(s, func(code string) string {
 49		lilcodes = append(lilcodes, code)
 50		return "`x`"
 51	})
 52
 53	// fewer side effects than html.EscapeString
 54	buf := make([]byte, 0, len(s))
 55	for _, c := range []byte(s) {
 56		switch c {
 57		case '&':
 58			buf = append(buf, []byte("&amp;")...)
 59		case '<':
 60			buf = append(buf, []byte("&lt;")...)
 61		case '>':
 62			buf = append(buf, []byte("&gt;")...)
 63		default:
 64			buf = append(buf, c)
 65		}
 66	}
 67	s = string(buf)
 68
 69	// mark it zero
 70	s = re_bolder.ReplaceAllString(s, "$1<b>$2</b>$3")
 71	s = re_italicer.ReplaceAllString(s, "$1<i>$2</i>$3")
 72	s = re_quoter.ReplaceAllString(s, "<blockquote>$1</blockquote><p>")
 73	s = re_link.ReplaceAllStringFunc(s, linkreplacer)
 74	s = re_zerolink.ReplaceAllString(s, `<a class="mention u-url" href="$2">$1</a>`)
 75
 76	// now restore the code blocks
 77	s = re_coder.ReplaceAllStringFunc(s, func(string) string {
 78		code := lilcodes[0]
 79		lilcodes = lilcodes[1:]
 80		code = html.EscapeString(code)
 81		return code
 82	})
 83	s = re_bigcoder.ReplaceAllStringFunc(s, func(string) string {
 84		code := bigcodes[0]
 85		bigcodes = bigcodes[1:]
 86		m := re_bigcoder.FindStringSubmatch(code)
 87		return "<pre><code>" + lighter.HighlightString(m[2], m[1]) + "</code></pre><p>"
 88	})
 89	s = re_coder.ReplaceAllString(s, "<code>$1</code>")
 90
 91	// some final fixups
 92	s = strings.Replace(s, "\n", "<br>", -1)
 93	s = strings.Replace(s, "<br><blockquote>", "<blockquote>", -1)
 94	s = strings.Replace(s, "<br><pre>", "<pre>", -1)
 95	s = strings.Replace(s, "<p><br>", "<p>", -1)
 96	return s
 97}
 98
 99func linkreplacer(url string) string {
100	if url[0:2] == "](" {
101		return url
102	}
103	prefix := ""
104	for !strings.HasPrefix(url, "http") {
105		prefix += url[0:1]
106		url = url[1:]
107	}
108	addparen := false
109	adddot := false
110	if strings.HasSuffix(url, ")") && strings.IndexByte(url, '(') == -1 {
111		url = url[:len(url)-1]
112		addparen = true
113	}
114	if strings.HasSuffix(url, ".") {
115		url = url[:len(url)-1]
116		adddot = true
117	}
118	url = fmt.Sprintf(`<a class="mention u-url" href="%s">%s</a>`, url, url)
119	if adddot {
120		url += "."
121	}
122	if addparen {
123		url += ")"
124	}
125	return prefix + url
126}