// Copyright 2017 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package markup

import (
	"bytes"
	"fmt"
	"net/url"
	"path"
	"path/filepath"
	"regexp"
	"strings"

	"code.gitea.io/gitea/modules/base"
	"code.gitea.io/gitea/modules/emoji"
	"code.gitea.io/gitea/modules/git"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/markup/common"
	"code.gitea.io/gitea/modules/references"
	"code.gitea.io/gitea/modules/setting"
	"code.gitea.io/gitea/modules/util"

	"github.com/unknwon/com"
	"golang.org/x/net/html"
	"golang.org/x/net/html/atom"
	"mvdan.cc/xurls/v2"
)

// Issue name styles
const (
	IssueNameStyleNumeric      = "numeric"
	IssueNameStyleAlphanumeric = "alphanumeric"
)

var (
	// NOTE: All below regex matching do not perform any extra validation.
	// Thus a link is produced even if the linked entity does not exist.
	// While fast, this is also incorrect and lead to false positives.
	// TODO: fix invalid linking issue

	// sha1CurrentPattern matches string that represents a commit SHA, e.g. d8a994ef243349f321568f9e36d5c3f444b99cae
	// Although SHA1 hashes are 40 chars long, the regex matches the hash from 7 to 40 chars in length
	// so that abbreviated hash links can be used as well. This matches git and github useability.
	sha1CurrentPattern = regexp.MustCompile(`(?:\s|^|\(|\[)([0-9a-f]{7,40})(?:\s|$|\)|\]|[.,](\s|$))`)

	// shortLinkPattern matches short but difficult to parse [[name|link|arg=test]] syntax
	shortLinkPattern = regexp.MustCompile(`\[\[(.*?)\]\](\w*)`)

	// anySHA1Pattern allows to split url containing SHA into parts
	anySHA1Pattern = regexp.MustCompile(`https?://(?:\S+/){4}([0-9a-f]{40})(/[^#\s]+)?(#\S+)?`)

	validLinksPattern = regexp.MustCompile(`^[a-z][\w-]+://`)

	// While this email regex is definitely not perfect and I'm sure you can come up
	// with edge cases, it is still accepted by the CommonMark specification, as
	// well as the HTML5 spec:
	//   http://spec.commonmark.org/0.28/#email-address
	//   https://html.spec.whatwg.org/multipage/input.html#e-mail-state-(type%3Demail)
	emailRegex = regexp.MustCompile("(?:\\s|^|\\(|\\[)([a-zA-Z0-9.!#$%&'*+\\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9]{2,}(?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+)(?:\\s|$|\\)|\\]|\\.(\\s|$))")

	// blackfriday extensions create IDs like fn:user-content-footnote
	blackfridayExtRegex = regexp.MustCompile(`[^:]*:user-content-`)

	// EmojiShortCodeRegex find emoji by alias like :smile:
	EmojiShortCodeRegex = regexp.MustCompile(`\:[\w\+\-]+\:{1}`)
)

// CSS class for action keywords (e.g. "closes: #1")
const keywordClass = "issue-keyword"

// regexp for full links to issues/pulls
var issueFullPattern *regexp.Regexp

// IsLink reports whether link fits valid format.
func IsLink(link []byte) bool {
	return isLink(link)
}

// isLink reports whether link fits valid format.
func isLink(link []byte) bool {
	return validLinksPattern.Match(link)
}

func isLinkStr(link string) bool {
	return validLinksPattern.MatchString(link)
}

// FIXME: This function is not concurrent safe
func getIssueFullPattern() *regexp.Regexp {
	if issueFullPattern == nil {
		issueFullPattern = regexp.MustCompile(regexp.QuoteMeta(setting.AppURL) +
			`\w+/\w+/(?:issues|pulls)/((?:\w{1,10}-)?[1-9][0-9]*)([\?|#]\S+.(\S+)?)?\b`)
	}
	return issueFullPattern
}

// CustomLinkURLSchemes allows for additional schemes to be detected when parsing links within text
func CustomLinkURLSchemes(schemes []string) {
	schemes = append(schemes, "http", "https")
	withAuth := make([]string, 0, len(schemes))
	validScheme := regexp.MustCompile(`^[a-z]+$`)
	for _, s := range schemes {
		if !validScheme.MatchString(s) {
			continue
		}
		without := false
		for _, sna := range xurls.SchemesNoAuthority {
			if s == sna {
				without = true
				break
			}
		}
		if without {
			s += ":"
		} else {
			s += "://"
		}
		withAuth = append(withAuth, s)
	}
	common.LinkRegex, _ = xurls.StrictMatchingScheme(strings.Join(withAuth, "|"))
}

// IsSameDomain checks if given url string has the same hostname as current Gitea instance
func IsSameDomain(s string) bool {
	if strings.HasPrefix(s, "/") {
		return true
	}
	if uapp, err := url.Parse(setting.AppURL); err == nil {
		if u, err := url.Parse(s); err == nil {
			return u.Host == uapp.Host
		}
		return false
	}
	return false
}

type postProcessError struct {
	context string
	err     error
}

func (p *postProcessError) Error() string {
	return "PostProcess: " + p.context + ", " + p.err.Error()
}

type processor func(ctx *postProcessCtx, node *html.Node)

var defaultProcessors = []processor{
	fullIssuePatternProcessor,
	fullSha1PatternProcessor,
	shortLinkProcessor,
	linkProcessor,
	mentionProcessor,
	issueIndexPatternProcessor,
	sha1CurrentPatternProcessor,
	emailAddressProcessor,
	emojiProcessor,
	emojiShortCodeProcessor,
}

type postProcessCtx struct {
	metas          map[string]string
	urlPrefix      string
	isWikiMarkdown bool

	// processors used by this context.
	procs []processor
}

// PostProcess does the final required transformations to the passed raw HTML
// data, and ensures its validity. Transformations include: replacing links and
// emails with HTML links, parsing shortlinks in the format of [[Link]], like
// MediaWiki, linking issues in the format #ID, and mentions in the format
// @user, and others.
func PostProcess(
	rawHTML []byte,
	urlPrefix string,
	metas map[string]string,
	isWikiMarkdown bool,
) ([]byte, error) {
	// create the context from the parameters
	ctx := &postProcessCtx{
		metas:          metas,
		urlPrefix:      urlPrefix,
		isWikiMarkdown: isWikiMarkdown,
		procs:          defaultProcessors,
	}
	return ctx.postProcess(rawHTML)
}

var commitMessageProcessors = []processor{
	fullIssuePatternProcessor,
	fullSha1PatternProcessor,
	linkProcessor,
	mentionProcessor,
	issueIndexPatternProcessor,
	sha1CurrentPatternProcessor,
	emailAddressProcessor,
	emojiProcessor,
	emojiShortCodeProcessor,
}

// RenderCommitMessage will use the same logic as PostProcess, but will disable
// the shortLinkProcessor and will add a defaultLinkProcessor if defaultLink is
// set, which changes every text node into a link to the passed default link.
func RenderCommitMessage(
	rawHTML []byte,
	urlPrefix, defaultLink string,
	metas map[string]string,
) ([]byte, error) {
	ctx := &postProcessCtx{
		metas:     metas,
		urlPrefix: urlPrefix,
		procs:     commitMessageProcessors,
	}
	if defaultLink != "" {
		// we don't have to fear data races, because being
		// commitMessageProcessors of fixed len and cap, every time we append
		// something to it the slice is realloc+copied, so append always
		// generates the slice ex-novo.
		ctx.procs = append(ctx.procs, genDefaultLinkProcessor(defaultLink))
	}
	return ctx.postProcess(rawHTML)
}

var commitMessageSubjectProcessors = []processor{
	fullIssuePatternProcessor,
	fullSha1PatternProcessor,
	linkProcessor,
	mentionProcessor,
	issueIndexPatternProcessor,
	sha1CurrentPatternProcessor,
	emojiShortCodeProcessor,
	emojiProcessor,
}

var emojiProcessors = []processor{
	emojiShortCodeProcessor,
	emojiProcessor,
}

// RenderCommitMessageSubject will use the same logic as PostProcess and
// RenderCommitMessage, but will disable the shortLinkProcessor and
// emailAddressProcessor, will add a defaultLinkProcessor if defaultLink is set,
// which changes every text node into a link to the passed default link.
func RenderCommitMessageSubject(
	rawHTML []byte,
	urlPrefix, defaultLink string,
	metas map[string]string,
) ([]byte, error) {
	ctx := &postProcessCtx{
		metas:     metas,
		urlPrefix: urlPrefix,
		procs:     commitMessageSubjectProcessors,
	}
	if defaultLink != "" {
		// we don't have to fear data races, because being
		// commitMessageSubjectProcessors of fixed len and cap, every time we
		// append something to it the slice is realloc+copied, so append always
		// generates the slice ex-novo.
		ctx.procs = append(ctx.procs, genDefaultLinkProcessor(defaultLink))
	}
	return ctx.postProcess(rawHTML)
}

// RenderIssueTitle to process title on individual issue/pull page
func RenderIssueTitle(
	rawHTML []byte,
	urlPrefix string,
	metas map[string]string,
) ([]byte, error) {
	ctx := &postProcessCtx{
		metas:     metas,
		urlPrefix: urlPrefix,
		procs: []processor{
			issueIndexPatternProcessor,
			sha1CurrentPatternProcessor,
			emojiShortCodeProcessor,
			emojiProcessor,
		},
	}
	return ctx.postProcess(rawHTML)
}

// RenderDescriptionHTML will use similar logic as PostProcess, but will
// use a single special linkProcessor.
func RenderDescriptionHTML(
	rawHTML []byte,
	urlPrefix string,
	metas map[string]string,
) ([]byte, error) {
	ctx := &postProcessCtx{
		metas:     metas,
		urlPrefix: urlPrefix,
		procs: []processor{
			descriptionLinkProcessor,
			emojiShortCodeProcessor,
			emojiProcessor,
		},
	}
	return ctx.postProcess(rawHTML)
}

// RenderEmoji for when we want to just process emoji and shortcodes
// in various places it isn't already run through the normal markdown procesor
func RenderEmoji(
	rawHTML []byte,
) ([]byte, error) {
	ctx := &postProcessCtx{
		procs: emojiProcessors,
	}
	return ctx.postProcess(rawHTML)
}

var tagCleaner = regexp.MustCompile(`<((?:/?\w+/\w+)|(?:/[\w ]+/)|(/?[hH][tT][mM][lL]\b)|(/?[hH][eE][aA][dD]\b))`)
var nulCleaner = strings.NewReplacer("\000", "")

func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
	if ctx.procs == nil {
		ctx.procs = defaultProcessors
	}

	// give a generous extra 50 bytes
	res := bytes.NewBuffer(make([]byte, 0, len(rawHTML)+50))
	// prepend "<html><body>"
	_, _ = res.WriteString("<html><body>")

	// Strip out nuls - they're always invalid
	_, _ = res.Write(tagCleaner.ReplaceAll([]byte(nulCleaner.Replace(string(rawHTML))), []byte("&lt;$1")))

	// close the tags
	_, _ = res.WriteString("</body></html>")

	// parse the HTML
	nodes, err := html.ParseFragment(res, nil)
	if err != nil {
		return nil, &postProcessError{"invalid HTML", err}
	}

	for _, node := range nodes {
		ctx.visitNode(node, true)
	}

	newNodes := make([]*html.Node, 0, len(nodes))

	for _, node := range nodes {
		if node.Data == "html" {
			node = node.FirstChild
			for node != nil && node.Data != "body" {
				node = node.NextSibling
			}
		}
		if node == nil {
			continue
		}
		if node.Data == "body" {
			child := node.FirstChild
			for child != nil {
				newNodes = append(newNodes, child)
				child = child.NextSibling
			}
		} else {
			newNodes = append(newNodes, node)
		}
	}

	nodes = newNodes

	// Create buffer in which the data will be placed again. We know that the
	// length will be at least that of res; to spare a few alloc+copy, we
	// reuse res, resetting its length to 0.
	res.Reset()
	// Render everything to buf.
	for _, node := range nodes {
		err = html.Render(res, node)
		if err != nil {
			return nil, &postProcessError{"error rendering processed HTML", err}
		}
	}

	// Everything done successfully, return parsed data.
	return res.Bytes(), nil
}

func (ctx *postProcessCtx) visitNode(node *html.Node, visitText bool) {
	// Add user-content- to IDs if they don't already have them
	for idx, attr := range node.Attr {
		if attr.Key == "id" && !(strings.HasPrefix(attr.Val, "user-content-") || blackfridayExtRegex.MatchString(attr.Val)) {
			node.Attr[idx].Val = "user-content-" + attr.Val
		}

		if attr.Key == "class" && attr.Val == "emoji" {
			visitText = false
		}
	}

	// We ignore code, pre and already generated links.
	switch node.Type {
	case html.TextNode:
		if visitText {
			ctx.textNode(node)
		}
	case html.ElementNode:
		if node.Data == "img" {
			for _, attr := range node.Attr {
				if attr.Key != "src" {
					continue
				}
				if len(attr.Val) > 0 && !isLinkStr(attr.Val) && !strings.HasPrefix(attr.Val, "data:image/") {
					prefix := ctx.urlPrefix
					if ctx.isWikiMarkdown {
						prefix = util.URLJoin(prefix, "wiki", "raw")
					}
					prefix = strings.Replace(prefix, "/src/", "/media/", 1)

					attr.Val = util.URLJoin(prefix, attr.Val)
				}
			}
		} else if node.Data == "a" {
			visitText = false
		} else if node.Data == "code" || node.Data == "pre" {
			return
		} else if node.Data == "i" {
			for _, attr := range node.Attr {
				if attr.Key != "class" {
					continue
				}
				classes := strings.Split(attr.Val, " ")
				for i, class := range classes {
					if class == "icon" {
						classes[0], classes[i] = classes[i], classes[0]
						attr.Val = strings.Join(classes, " ")

						// Remove all children of icons
						child := node.FirstChild
						for child != nil {
							node.RemoveChild(child)
							child = node.FirstChild
						}
						break
					}
				}
			}
		}
		for n := node.FirstChild; n != nil; n = n.NextSibling {
			ctx.visitNode(n, visitText)
		}
	}
	// ignore everything else
}

// textNode runs the passed node through various processors, in order to handle
// all kinds of special links handled by the post-processing.
func (ctx *postProcessCtx) textNode(node *html.Node) {
	for _, processor := range ctx.procs {
		processor(ctx, node)
	}
}

// createKeyword() renders a highlighted version of an action keyword
func createKeyword(content string) *html.Node {
	span := &html.Node{
		Type: html.ElementNode,
		Data: atom.Span.String(),
		Attr: []html.Attribute{},
	}
	span.Attr = append(span.Attr, html.Attribute{Key: "class", Val: keywordClass})

	text := &html.Node{
		Type: html.TextNode,
		Data: content,
	}
	span.AppendChild(text)

	return span
}

func createEmoji(content, class, name string) *html.Node {
	span := &html.Node{
		Type: html.ElementNode,
		Data: atom.Span.String(),
		Attr: []html.Attribute{},
	}
	if class != "" {
		span.Attr = append(span.Attr, html.Attribute{Key: "class", Val: class})
	}
	if name != "" {
		span.Attr = append(span.Attr, html.Attribute{Key: "aria-label", Val: name})
	}

	text := &html.Node{
		Type: html.TextNode,
		Data: content,
	}

	span.AppendChild(text)
	return span
}

func createCustomEmoji(alias, class string) *html.Node {

	span := &html.Node{
		Type: html.ElementNode,
		Data: atom.Span.String(),
		Attr: []html.Attribute{},
	}
	if class != "" {
		span.Attr = append(span.Attr, html.Attribute{Key: "class", Val: class})
		span.Attr = append(span.Attr, html.Attribute{Key: "aria-label", Val: alias})
	}

	img := &html.Node{
		Type:     html.ElementNode,
		DataAtom: atom.Img,
		Data:     "img",
		Attr:     []html.Attribute{},
	}
	if class != "" {
		img.Attr = append(img.Attr, html.Attribute{Key: "alt", Val: fmt.Sprintf(`:%s:`, alias)})
		img.Attr = append(img.Attr, html.Attribute{Key: "src", Val: fmt.Sprintf(`%s/img/emoji/%s.png`, setting.StaticURLPrefix, alias)})
	}

	span.AppendChild(img)
	return span
}

func createLink(href, content, class string) *html.Node {
	a := &html.Node{
		Type: html.ElementNode,
		Data: atom.A.String(),
		Attr: []html.Attribute{{Key: "href", Val: href}},
	}

	if class != "" {
		a.Attr = append(a.Attr, html.Attribute{Key: "class", Val: class})
	}

	text := &html.Node{
		Type: html.TextNode,
		Data: content,
	}

	a.AppendChild(text)
	return a
}

func createCodeLink(href, content, class string) *html.Node {
	a := &html.Node{
		Type: html.ElementNode,
		Data: atom.A.String(),
		Attr: []html.Attribute{{Key: "href", Val: href}},
	}

	if class != "" {
		a.Attr = append(a.Attr, html.Attribute{Key: "class", Val: class})
	}

	text := &html.Node{
		Type: html.TextNode,
		Data: content,
	}

	code := &html.Node{
		Type: html.ElementNode,
		Data: atom.Code.String(),
		Attr: []html.Attribute{{Key: "class", Val: "nohighlight"}},
	}

	code.AppendChild(text)
	a.AppendChild(code)
	return a
}

// replaceContent takes text node, and in its content it replaces a section of
// it with the specified newNode.
func replaceContent(node *html.Node, i, j int, newNode *html.Node) {
	replaceContentList(node, i, j, []*html.Node{newNode})
}

// replaceContentList takes text node, and in its content it replaces a section of
// it with the specified newNodes. An example to visualize how this can work can
// be found here: https://play.golang.org/p/5zP8NnHZ03s
func replaceContentList(node *html.Node, i, j int, newNodes []*html.Node) {
	// get the data before and after the match
	before := node.Data[:i]
	after := node.Data[j:]

	// Replace in the current node the text, so that it is only what it is
	// supposed to have.
	node.Data = before

	// Get the current next sibling, before which we place the replaced data,
	// and after that we place the new text node.
	nextSibling := node.NextSibling
	for _, n := range newNodes {
		node.Parent.InsertBefore(n, nextSibling)
	}
	if after != "" {
		node.Parent.InsertBefore(&html.Node{
			Type: html.TextNode,
			Data: after,
		}, nextSibling)
	}
}

func mentionProcessor(ctx *postProcessCtx, node *html.Node) {
	start := 0
	next := node.NextSibling
	for node != nil && node != next && start < len(node.Data) {
		// We replace only the first mention; other mentions will be addressed later
		found, loc := references.FindFirstMentionBytes([]byte(node.Data[start:]))
		if !found {
			return
		}
		loc.Start += start
		loc.End += start
		mention := node.Data[loc.Start:loc.End]
		var teams string
		teams, ok := ctx.metas["teams"]
		// FIXME: util.URLJoin may not be necessary here:
		// - setting.AppURL is defined to have a terminal '/' so unless mention[1:]
		// is an AppSubURL link we can probably fallback to concatenation.
		// team mention should follow @orgName/teamName style
		if ok && strings.Contains(mention, "/") {
			mentionOrgAndTeam := strings.Split(mention, "/")
			if mentionOrgAndTeam[0][1:] == ctx.metas["org"] && strings.Contains(teams, ","+strings.ToLower(mentionOrgAndTeam[1])+",") {
				replaceContent(node, loc.Start, loc.End, createLink(util.URLJoin(setting.AppURL, "org", ctx.metas["org"], "teams", mentionOrgAndTeam[1]), mention, "mention"))
				node = node.NextSibling.NextSibling
				start = 0
				continue
			}
			start = loc.End
			continue
		}
		replaceContent(node, loc.Start, loc.End, createLink(util.URLJoin(setting.AppURL, mention[1:]), mention, "mention"))
		node = node.NextSibling.NextSibling
		start = 0
	}
}

func shortLinkProcessor(ctx *postProcessCtx, node *html.Node) {
	shortLinkProcessorFull(ctx, node, false)
}

func shortLinkProcessorFull(ctx *postProcessCtx, node *html.Node, noLink bool) {
	next := node.NextSibling
	for node != nil && node != next {
		m := shortLinkPattern.FindStringSubmatchIndex(node.Data)
		if m == nil {
			return
		}

		content := node.Data[m[2]:m[3]]
		tail := node.Data[m[4]:m[5]]
		props := make(map[string]string)

		// MediaWiki uses [[link|text]], while GitHub uses [[text|link]]
		// It makes page handling terrible, but we prefer GitHub syntax
		// And fall back to MediaWiki only when it is obvious from the look
		// Of text and link contents
		sl := strings.Split(content, "|")
		for _, v := range sl {
			if equalPos := strings.IndexByte(v, '='); equalPos == -1 {
				// There is no equal in this argument; this is a mandatory arg
				if props["name"] == "" {
					if isLinkStr(v) {
						// If we clearly see it is a link, we save it so

						// But first we need to ensure, that if both mandatory args provided
						// look like links, we stick to GitHub syntax
						if props["link"] != "" {
							props["name"] = props["link"]
						}

						props["link"] = strings.TrimSpace(v)
					} else {
						props["name"] = v
					}
				} else {
					props["link"] = strings.TrimSpace(v)
				}
			} else {
				// There is an equal; optional argument.

				sep := strings.IndexByte(v, '=')
				key, val := v[:sep], html.UnescapeString(v[sep+1:])

				// When parsing HTML, x/net/html will change all quotes which are
				// not used for syntax into UTF-8 quotes. So checking val[0] won't
				// be enough, since that only checks a single byte.
				if len(val) > 1 {
					if (strings.HasPrefix(val, "“") && strings.HasSuffix(val, "”")) ||
						(strings.HasPrefix(val, "‘") && strings.HasSuffix(val, "’")) {
						const lenQuote = len("‘")
						val = val[lenQuote : len(val)-lenQuote]
					} else if (strings.HasPrefix(val, "\"") && strings.HasSuffix(val, "\"")) ||
						(strings.HasPrefix(val, "'") && strings.HasSuffix(val, "'")) {
						val = val[1 : len(val)-1]
					} else if strings.HasPrefix(val, "'") && strings.HasSuffix(val, "’") {
						const lenQuote = len("‘")
						val = val[1 : len(val)-lenQuote]
					}
				}
				props[key] = val
			}
		}

		var name, link string
		if props["link"] != "" {
			link = props["link"]
		} else if props["name"] != "" {
			link = props["name"]
		}
		if props["title"] != "" {
			name = props["title"]
		} else if props["name"] != "" {
			name = props["name"]
		} else {
			name = link
		}

		name += tail
		image := false
		switch ext := filepath.Ext(link); ext {
		// fast path: empty string, ignore
		case "":
			// leave image as false
		case ".jpg", ".jpeg", ".png", ".tif", ".tiff", ".webp", ".gif", ".bmp", ".ico", ".svg":
			image = true
		}

		childNode := &html.Node{}
		linkNode := &html.Node{
			FirstChild: childNode,
			LastChild:  childNode,
			Type:       html.ElementNode,
			Data:       "a",
			DataAtom:   atom.A,
		}
		childNode.Parent = linkNode
		absoluteLink := isLinkStr(link)
		if !absoluteLink {
			if image {
				link = strings.ReplaceAll(link, " ", "+")
			} else {
				link = strings.ReplaceAll(link, " ", "-")
			}
			if !strings.Contains(link, "/") {
				link = url.PathEscape(link)
			}
		}
		urlPrefix := ctx.urlPrefix
		if image {
			if !absoluteLink {
				if IsSameDomain(urlPrefix) {
					urlPrefix = strings.Replace(urlPrefix, "/src/", "/raw/", 1)
				}
				if ctx.isWikiMarkdown {
					link = util.URLJoin("wiki", "raw", link)
				}
				link = util.URLJoin(urlPrefix, link)
			}
			title := props["title"]
			if title == "" {
				title = props["alt"]
			}
			if title == "" {
				title = path.Base(name)
			}
			alt := props["alt"]
			if alt == "" {
				alt = name
			}

			// make the childNode an image - if we can, we also place the alt
			childNode.Type = html.ElementNode
			childNode.Data = "img"
			childNode.DataAtom = atom.Img
			childNode.Attr = []html.Attribute{
				{Key: "src", Val: link},
				{Key: "title", Val: title},
				{Key: "alt", Val: alt},
			}
			if alt == "" {
				childNode.Attr = childNode.Attr[:2]
			}
		} else {
			if !absoluteLink {
				if ctx.isWikiMarkdown {
					link = util.URLJoin("wiki", link)
				}
				link = util.URLJoin(urlPrefix, link)
			}
			childNode.Type = html.TextNode
			childNode.Data = name
		}
		if noLink {
			linkNode = childNode
		} else {
			linkNode.Attr = []html.Attribute{{Key: "href", Val: link}}
		}
		replaceContent(node, m[0], m[1], linkNode)
		node = node.NextSibling.NextSibling
	}
}

func fullIssuePatternProcessor(ctx *postProcessCtx, node *html.Node) {
	if ctx.metas == nil {
		return
	}
	next := node.NextSibling
	for node != nil && node != next {
		m := getIssueFullPattern().FindStringSubmatchIndex(node.Data)
		if m == nil {
			return
		}
		link := node.Data[m[0]:m[1]]
		id := "#" + node.Data[m[2]:m[3]]

		// extract repo and org name from matched link like
		// http://localhost:3000/gituser/myrepo/issues/1
		linkParts := strings.Split(path.Clean(link), "/")
		matchOrg := linkParts[len(linkParts)-4]
		matchRepo := linkParts[len(linkParts)-3]

		if matchOrg == ctx.metas["user"] && matchRepo == ctx.metas["repo"] {
			// TODO if m[4]:m[5] is not nil, then link is to a comment,
			// and we should indicate that in the text somehow
			replaceContent(node, m[0], m[1], createLink(link, id, "ref-issue"))
		} else {
			orgRepoID := matchOrg + "/" + matchRepo + id
			replaceContent(node, m[0], m[1], createLink(link, orgRepoID, "ref-issue"))
		}
		node = node.NextSibling.NextSibling
	}
}

func issueIndexPatternProcessor(ctx *postProcessCtx, node *html.Node) {
	if ctx.metas == nil {
		return
	}
	var (
		found bool
		ref   *references.RenderizableReference
	)

	next := node.NextSibling
	for node != nil && node != next {
		_, exttrack := ctx.metas["format"]
		alphanum := ctx.metas["style"] == IssueNameStyleAlphanumeric

		// Repos with external issue trackers might still need to reference local PRs
		// We need to concern with the first one that shows up in the text, whichever it is
		found, ref = references.FindRenderizableReferenceNumeric(node.Data, exttrack && alphanum)
		if exttrack && alphanum {
			if found2, ref2 := references.FindRenderizableReferenceAlphanumeric(node.Data); found2 {
				if !found || ref2.RefLocation.Start < ref.RefLocation.Start {
					found = true
					ref = ref2
				}
			}
		}
		if !found {
			return
		}

		var link *html.Node
		reftext := node.Data[ref.RefLocation.Start:ref.RefLocation.End]
		if exttrack && !ref.IsPull {
			ctx.metas["index"] = ref.Issue
			link = createLink(com.Expand(ctx.metas["format"], ctx.metas), reftext, "ref-issue")
		} else {
			// Path determines the type of link that will be rendered. It's unknown at this point whether
			// the linked item is actually a PR or an issue. Luckily it's of no real consequence because
			// Gitea will redirect on click as appropriate.
			path := "issues"
			if ref.IsPull {
				path = "pulls"
			}
			if ref.Owner == "" {
				link = createLink(util.URLJoin(setting.AppURL, ctx.metas["user"], ctx.metas["repo"], path, ref.Issue), reftext, "ref-issue")
			} else {
				link = createLink(util.URLJoin(setting.AppURL, ref.Owner, ref.Name, path, ref.Issue), reftext, "ref-issue")
			}
		}

		if ref.Action == references.XRefActionNone {
			replaceContent(node, ref.RefLocation.Start, ref.RefLocation.End, link)
			node = node.NextSibling.NextSibling
			continue
		}

		// Decorate action keywords if actionable
		var keyword *html.Node
		if references.IsXrefActionable(ref, exttrack, alphanum) {
			keyword = createKeyword(node.Data[ref.ActionLocation.Start:ref.ActionLocation.End])
		} else {
			keyword = &html.Node{
				Type: html.TextNode,
				Data: node.Data[ref.ActionLocation.Start:ref.ActionLocation.End],
			}
		}
		spaces := &html.Node{
			Type: html.TextNode,
			Data: node.Data[ref.ActionLocation.End:ref.RefLocation.Start],
		}
		replaceContentList(node, ref.ActionLocation.Start, ref.RefLocation.End, []*html.Node{keyword, spaces, link})
		node = node.NextSibling.NextSibling.NextSibling.NextSibling
	}
}

// fullSha1PatternProcessor renders SHA containing URLs
func fullSha1PatternProcessor(ctx *postProcessCtx, node *html.Node) {
	if ctx.metas == nil {
		return
	}

	next := node.NextSibling
	for node != nil && node != next {
		m := anySHA1Pattern.FindStringSubmatchIndex(node.Data)
		if m == nil {
			return
		}

		urlFull := node.Data[m[0]:m[1]]
		text := base.ShortSha(node.Data[m[2]:m[3]])

		// 3rd capture group matches a optional path
		subpath := ""
		if m[5] > 0 {
			subpath = node.Data[m[4]:m[5]]
		}

		// 4th capture group matches a optional url hash
		hash := ""
		if m[7] > 0 {
			hash = node.Data[m[6]:m[7]][1:]
		}

		start := m[0]
		end := m[1]

		// If url ends in '.', it's very likely that it is not part of the
		// actual url but used to finish a sentence.
		if strings.HasSuffix(urlFull, ".") {
			end--
			urlFull = urlFull[:len(urlFull)-1]
			if hash != "" {
				hash = hash[:len(hash)-1]
			} else if subpath != "" {
				subpath = subpath[:len(subpath)-1]
			}
		}

		if subpath != "" {
			text += subpath
		}

		if hash != "" {
			text += " (" + hash + ")"
		}

		replaceContent(node, start, end, createCodeLink(urlFull, text, "commit"))
		node = node.NextSibling.NextSibling
	}
}

// emojiShortCodeProcessor for rendering text like :smile: into emoji
func emojiShortCodeProcessor(ctx *postProcessCtx, node *html.Node) {
	start := 0
	next := node.NextSibling
	for node != nil && node != next && start < len(node.Data) {
		m := EmojiShortCodeRegex.FindStringSubmatchIndex(node.Data[start:])
		if m == nil {
			return
		}
		m[0] += start
		m[1] += start

		start = m[1]

		alias := node.Data[m[0]:m[1]]
		alias = strings.ReplaceAll(alias, ":", "")
		converted := emoji.FromAlias(alias)
		if converted == nil {
			// check if this is a custom reaction
			s := strings.Join(setting.UI.Reactions, " ") + "gitea"
			if strings.Contains(s, alias) {
				replaceContent(node, m[0], m[1], createCustomEmoji(alias, "emoji"))
				node = node.NextSibling.NextSibling
				start = 0
				continue
			}
			continue
		}

		replaceContent(node, m[0], m[1], createEmoji(converted.Emoji, "emoji", converted.Description))
		node = node.NextSibling.NextSibling
		start = 0
	}
}

// emoji processor to match emoji and add emoji class
func emojiProcessor(ctx *postProcessCtx, node *html.Node) {
	start := 0
	next := node.NextSibling
	for node != nil && node != next && start < len(node.Data) {
		m := emoji.FindEmojiSubmatchIndex(node.Data[start:])
		if m == nil {
			return
		}
		m[0] += start
		m[1] += start

		codepoint := node.Data[m[0]:m[1]]
		start = m[1]
		val := emoji.FromCode(codepoint)
		if val != nil {
			replaceContent(node, m[0], m[1], createEmoji(codepoint, "emoji", val.Description))
			node = node.NextSibling.NextSibling
			start = 0
		}
	}
}

// sha1CurrentPatternProcessor renders SHA1 strings to corresponding links that
// are assumed to be in the same repository.
func sha1CurrentPatternProcessor(ctx *postProcessCtx, node *html.Node) {
	if ctx.metas == nil || ctx.metas["user"] == "" || ctx.metas["repo"] == "" || ctx.metas["repoPath"] == "" {
		return
	}

	start := 0
	next := node.NextSibling
	for node != nil && node != next && start < len(node.Data) {
		m := sha1CurrentPattern.FindStringSubmatchIndex(node.Data[start:])
		if m == nil {
			return
		}
		m[2] += start
		m[3] += start

		hash := node.Data[m[2]:m[3]]
		// The regex does not lie, it matches the hash pattern.
		// However, a regex cannot know if a hash actually exists or not.
		// We could assume that a SHA1 hash should probably contain alphas AND numerics
		// but that is not always the case.
		// Although unlikely, deadbeef and 1234567 are valid short forms of SHA1 hash
		// as used by git and github for linking and thus we have to do similar.
		// Because of this, we check to make sure that a matched hash is actually
		// a commit in the repository before making it a link.
		if _, err := git.NewCommand("rev-parse", "--verify", hash).RunInDirBytes(ctx.metas["repoPath"]); err != nil {
			if !strings.Contains(err.Error(), "fatal: Needed a single revision") {
				log.Debug("sha1CurrentPatternProcessor git rev-parse: %v", err)
			}
			start = m[3]
			continue
		}

		replaceContent(node, m[2], m[3],
			createCodeLink(util.URLJoin(setting.AppURL, ctx.metas["user"], ctx.metas["repo"], "commit", hash), base.ShortSha(hash), "commit"))
		start = 0
		node = node.NextSibling.NextSibling
	}
}

// emailAddressProcessor replaces raw email addresses with a mailto: link.
func emailAddressProcessor(ctx *postProcessCtx, node *html.Node) {
	next := node.NextSibling
	for node != nil && node != next {
		m := emailRegex.FindStringSubmatchIndex(node.Data)
		if m == nil {
			return
		}

		mail := node.Data[m[2]:m[3]]
		replaceContent(node, m[2], m[3], createLink("mailto:"+mail, mail, "mailto"))
		node = node.NextSibling.NextSibling
	}
}

// linkProcessor creates links for any HTTP or HTTPS URL not captured by
// markdown.
func linkProcessor(ctx *postProcessCtx, node *html.Node) {
	next := node.NextSibling
	for node != nil && node != next {
		m := common.LinkRegex.FindStringIndex(node.Data)
		if m == nil {
			return
		}
		uri := node.Data[m[0]:m[1]]
		replaceContent(node, m[0], m[1], createLink(uri, uri, "link"))
		node = node.NextSibling.NextSibling
	}
}

func genDefaultLinkProcessor(defaultLink string) processor {
	return func(ctx *postProcessCtx, node *html.Node) {
		ch := &html.Node{
			Parent: node,
			Type:   html.TextNode,
			Data:   node.Data,
		}

		node.Type = html.ElementNode
		node.Data = "a"
		node.DataAtom = atom.A
		node.Attr = []html.Attribute{
			{Key: "href", Val: defaultLink},
			{Key: "class", Val: "default-link"},
		}
		node.FirstChild, node.LastChild = ch, ch
	}
}

// descriptionLinkProcessor creates links for DescriptionHTML
func descriptionLinkProcessor(ctx *postProcessCtx, node *html.Node) {
	next := node.NextSibling
	for node != nil && node != next {
		m := common.LinkRegex.FindStringIndex(node.Data)
		if m == nil {
			return
		}

		uri := node.Data[m[0]:m[1]]
		replaceContent(node, m[0], m[1], createDescriptionLink(uri, uri))
		node = node.NextSibling.NextSibling
	}
}

func createDescriptionLink(href, content string) *html.Node {
	textNode := &html.Node{
		Type: html.TextNode,
		Data: content,
	}
	linkNode := &html.Node{
		FirstChild: textNode,
		LastChild:  textNode,
		Type:       html.ElementNode,
		Data:       "a",
		DataAtom:   atom.A,
		Attr: []html.Attribute{
			{Key: "href", Val: href},
			{Key: "target", Val: "_blank"},
			{Key: "rel", Val: "noopener noreferrer"},
		},
	}
	textNode.Parent = linkNode
	return linkNode
}