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463 lines
9.3 KiB
Go
463 lines
9.3 KiB
Go
// Copyright 2015 The Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package linkify provides a way to find links in plain text.
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package linkify
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import (
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"strings"
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"unicode/utf8"
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)
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// Link represents a link found in a string with a schema and a position in the string.
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type Link struct {
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Scheme string
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Start, End int
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}
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func max(a, b int) int {
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if a >= b {
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return a
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}
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return b
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}
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// Links returns links found in s.
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func Links(s string) (links []Link) {
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for i := 0; i < len(s)-2; i++ {
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switch s[i] {
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case '.': // IP address or domain name
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if i == 0 {
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continue // . at the start of a line
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}
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if length := match(s[i+1:]); length > 0 {
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pos := i + 1 + length
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switch s[pos-1] {
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case '.': // IP address
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if pos >= len(s) {
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continue // . at the end of line
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}
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if !digit(s[i-1]) {
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i = pos
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continue // . should be preceded by a digit
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}
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if !digit(s[pos]) {
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i = pos
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continue // . should be followed by a digit
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}
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// find the start of the IP address
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j := i - 2
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m := max(0, j-3)
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for j >= m && digit(s[j]) {
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j--
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}
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if i-2-j > 2 {
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i = pos + 1
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continue // at most 3 digits
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}
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start := 0
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if j >= 0 {
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r, rlen := utf8.DecodeLastRuneInString(s[:j+1])
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if !isPunctOrSpaceOrControl(r) {
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i = pos + 1
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continue
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}
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switch r {
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case '.', ':', '/', '\\', '-', '_':
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i = pos + 1
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continue
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}
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start = j + 2 - rlen
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}
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length, ok := skipIPv4(s[start:])
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if !ok {
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i = pos + 1
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continue
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}
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end := start + length
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if end == len(s) {
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links = append(links, Link{
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Scheme: "",
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Start: start,
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End: end,
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})
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return
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}
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r, _ := utf8.DecodeRuneInString(s[end:])
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if !isPunctOrSpaceOrControl(r) {
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continue
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}
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end = skipPort(s, end)
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end = skipPath(s, end)
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end = skipQuery(s, end)
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end = skipFragment(s, end)
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end = unskipPunct(s, end)
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if end < len(s) {
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r, _ = utf8.DecodeRuneInString(s[end:])
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if !isPunctOrSpaceOrControl(r) || r == '%' {
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continue
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}
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}
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links = append(links, Link{
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Scheme: "",
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Start: start,
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End: end,
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})
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i = end
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default: // domain name
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r, _ := utf8.DecodeLastRuneInString(s[:i])
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if isPunctOrSpaceOrControl(r) {
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continue
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}
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if pos == len(s) {
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start, ok := findHostnameStart(s, i)
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if !ok {
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continue
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}
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links = append(links, Link{
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Scheme: "",
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Start: start,
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End: pos,
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})
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return
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}
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if s[i+1:pos] != "xn--" {
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r, _ = utf8.DecodeRuneInString(s[pos:])
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if isLetterOrDigit(r) {
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continue // should not be followed by a letter or a digit
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}
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}
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end, dot, ok := findHostnameEnd(s, pos)
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if !ok {
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continue
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}
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dot = max(dot, i)
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if !(dot+5 <= len(s) && s[dot+1:dot+5] == "xn--") {
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if length := match(s[dot+1:]); dot+length+1 != end {
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continue
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}
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}
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start, ok := findHostnameStart(s, i)
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if !ok {
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continue
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}
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end = skipPort(s, end)
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end = skipPath(s, end)
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end = skipQuery(s, end)
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end = skipFragment(s, end)
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end = unskipPunct(s, end)
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if end < len(s) {
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r, _ = utf8.DecodeRuneInString(s[end:])
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if !isPunctOrSpaceOrControl(r) || r == '%' {
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continue // should be followed by punctuation or space
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}
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}
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links = append(links, Link{
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Scheme: "",
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Start: start,
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End: end,
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})
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i = end
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}
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}
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case '/': // schema-less link
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if s[i+1] != '/' {
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continue
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}
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if i > 0 {
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if s[i-1] == ':' {
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i++
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continue // should not be preceded by a colon
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}
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r, _ := utf8.DecodeLastRuneInString(s[:i])
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if !isPunctOrSpaceOrControl(r) {
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i++
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continue // should be preceded by punctuation or space
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}
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}
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r, _ := utf8.DecodeRuneInString(s[i+2:])
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if !isLetterOrDigit(r) {
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i++
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continue // should be followed by a letter or a digit
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}
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start := i
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end, dot, ok := findHostnameEnd(s, i+2)
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if !ok {
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continue
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}
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if s[i+2:end] != "localhost" {
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if dot == -1 {
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continue // no dot
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}
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if length, ok := skipIPv4(s[i+2:]); !ok || i+2+length != end {
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if length := match(s[dot+1:]); dot+length+1 != end {
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continue
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}
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}
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}
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end = skipPort(s, end)
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end = skipPath(s, end)
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end = skipQuery(s, end)
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end = skipFragment(s, end)
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end = unskipPunct(s, end)
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if end < len(s) {
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r, _ = utf8.DecodeRuneInString(s[end:])
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if !isPunctOrSpaceOrControl(r) || r == '%' {
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continue // should be followed by punctuation or space
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}
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}
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links = append(links, Link{
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Scheme: "//",
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Start: start,
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End: end,
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})
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i = end
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case ':': // http, https, ftp, mailto or localhost
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if i < 3 { // at least ftp:
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continue
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}
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if i >= 9 && s[i-1] == 't' && s[i-9:i] == "localhost" {
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j := i - 9
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if !digit(s[j+10]) {
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continue
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}
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if j > 0 {
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r, _ := utf8.DecodeLastRuneInString(s[:j])
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if !isPunctOrSpaceOrControl(r) {
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i++
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continue // should be preceded by punctuation or space
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}
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}
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start := j
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pos := j + 9
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end := skipPort(s, pos)
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if end == pos {
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continue // invalid port
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}
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end = skipPath(s, end)
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end = skipQuery(s, end)
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end = skipFragment(s, end)
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end = unskipPunct(s, end)
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if end < len(s) {
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r, _ := utf8.DecodeRuneInString(s[end:])
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if !isPunctOrSpaceOrControl(r) || r == '%' {
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i++
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continue // should be followed by punctuation or space
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}
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}
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links = append(links, Link{
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Scheme: "",
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Start: start,
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End: end,
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})
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i = end
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break
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}
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j := i - 1
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var start int
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var schema string
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switch byteToLower(s[j]) {
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case 'o': // mailto
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if j < 5 {
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continue // too short for mailto
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}
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if len(s)-j < 8 {
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continue // insufficient length after
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}
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if strings.ToLower(s[j-5:j+2]) != "mailto:" {
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continue
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}
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r, _ := utf8.DecodeLastRuneInString(s[:j-5])
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if isLetterOrDigit(r) {
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continue // should not be preceded by a letter or a digit
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}
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r, _ = utf8.DecodeRuneInString(s[j+2:])
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if !isAllowedInEmail(r) {
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continue // should be followed by a valid e-mail character
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}
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start = j - 5
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end, ok := findEmailEnd(s, j+2)
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if !ok {
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continue
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}
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links = append(links, Link{
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Scheme: "mailto:",
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Start: start,
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End: end,
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})
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i = end
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continue // continue processing
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case 'p': // http or ftp
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if len(s)-j < 8 {
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continue // insufficient length after
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}
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switch byteToLower(s[j-2]) {
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case 'f':
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if strings.ToLower(s[j-2:j+4]) != "ftp://" {
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continue
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}
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start = j - 2
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schema = "ftp:"
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case 't':
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if j < 3 {
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continue
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}
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if strings.ToLower(s[j-3:j+4]) != "http://" {
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continue
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}
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start = j - 3
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schema = "http:"
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default:
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continue
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}
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case 's': // https
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if j < 4 {
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continue // too short for https
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}
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if len(s)-j < 8 {
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continue // insufficient length after
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}
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start = j - 4
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if strings.ToLower(s[start:j+4]) != "https://" {
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continue
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}
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schema = "https:"
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default:
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continue
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}
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// http, https or ftp
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if start > 0 {
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r, _ := utf8.DecodeLastRuneInString(s[:start])
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if !isPunctOrSpaceOrControl(r) {
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continue // should be preceded by punctuation or space
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}
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}
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r, _ := utf8.DecodeRuneInString(s[j+4:])
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if isPunctOrSpaceOrControl(r) {
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continue
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}
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end, dot, ok := findHostnameEnd(s, j+4)
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if !ok {
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continue
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}
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if s[j+4:end] != "localhost" {
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if dot == -1 {
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continue // no dot
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}
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if length, ok := skipIPv4(s[j+4:]); !ok || j+4+length != end {
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if !(dot+5 <= len(s) && s[dot+1:dot+5] == "xn--") {
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if length := match(s[dot+1:]); dot+length+1 != end {
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continue
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}
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}
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}
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}
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end = skipPort(s, end)
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end = skipPath(s, end)
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end = skipQuery(s, end)
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end = skipFragment(s, end)
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end = unskipPunct(s, end)
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if end < len(s) {
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r, _ = utf8.DecodeRuneInString(s[end:])
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if !isPunctOrSpaceOrControl(r) || r == '%' {
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continue // should be followed by punctuation or space
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}
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}
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links = append(links, Link{
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Scheme: schema,
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Start: start,
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End: end,
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})
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i = end
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case '@': // schema-less e-mail
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if i == 0 {
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continue // @ at the start of a line
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}
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if len(s)-i < 5 {
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continue // insufficient length after
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}
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r, _ := utf8.DecodeLastRuneInString(s[:i])
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if !isAllowedInEmail(r) {
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continue // should be preceded by a valid e-mail character
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}
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r, _ = utf8.DecodeRuneInString(s[i+1:])
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if !isLetterOrDigit(r) {
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continue // should be followed by a letter or a digit
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}
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start, ok := findEmailStart(s, i-1)
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if !ok {
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continue
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}
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end, dot, ok := findHostnameEnd(s, i+1)
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if !ok {
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continue
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}
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if dot == -1 {
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continue // no dot
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}
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if !(dot+5 <= len(s) && s[dot+1:dot+5] == "xn--") {
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if length := match(s[dot+1:]); dot+length+1 != end {
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continue
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}
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}
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links = append(links, Link{
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Scheme: "mailto:",
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Start: start,
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End: end,
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})
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i = end
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}
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}
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return
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}
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