Rewrite reference processing code in preparation for opening/closing from comment references (#8261)

* Add a markdown stripper for mentions and xrefs

* Improve comments

* Small code simplification

* Move reference code to modules/references

* Fix typo

* Make MarkdownStripper return [][]byte

* Implement preliminary keywords parsing

* Add FIXME comment

* Fix comment

* make fmt

* Fix permissions check

* Fix text assumptions

* Fix imports

* Fix lint, fmt

* Fix unused import

* Add missing export comment

* Bypass revive on implemented interface

* Move mdstripper into its own package

* Support alphanumeric patterns

* Refactor FindAllMentions

* Move mentions test to references

* Parse mentions from reference package

* Refactor code to implement renderizable references

* Fix typo

* Move patterns and tests to the references package

* Fix nil reference

* Preliminary rendering attempt of closing keywords

* Normalize names, comments, general tidy-up

* Add CSS style for action keywords

* Fix permission for admin and owner

* Fix golangci-lint

* Fix golangci-lint

1 files changed, 322 insertions, 0 deletions

diff --git a/modules/references/references.go b/modules/references/references.go
new file mode 100644
index 0000000000..9c74d0d081
--- /dev/null
+++ b/modules/references/references.go
@@ -0,0 +1,322 @@
+// Copyright 2019 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 references
+
+import (
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+
+	"code.gitea.io/gitea/modules/markup/mdstripper"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+var (
+	// validNamePattern performs only the most basic validation for user or repository names
+	// Repository name should contain only alphanumeric, dash ('-'), underscore ('_') and dot ('.') characters.
+	validNamePattern = regexp.MustCompile(`^[a-z0-9_.-]+$`)
+
+	// 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
+
+	// mentionPattern matches all mentions in the form of "@user"
+	mentionPattern = regexp.MustCompile(`(?:\s|^|\(|\[)(@[0-9a-zA-Z-_\.]+)(?:\s|$|\)|\])`)
+	// issueNumericPattern matches string that references to a numeric issue, e.g. #1287
+	issueNumericPattern = regexp.MustCompile(`(?:\s|^|\(|\[)(#[0-9]+)(?:\s|$|\)|\]|:|\.(\s|$))`)
+	// issueAlphanumericPattern matches string that references to an alphanumeric issue, e.g. ABC-1234
+	issueAlphanumericPattern = regexp.MustCompile(`(?:\s|^|\(|\[)([A-Z]{1,10}-[1-9][0-9]*)(?:\s|$|\)|\]|:|\.(\s|$))`)
+	// crossReferenceIssueNumericPattern matches string that references a numeric issue in a different repository
+	// e.g. gogits/gogs#12345
+	crossReferenceIssueNumericPattern = regexp.MustCompile(`(?:\s|^|\(|\[)([0-9a-zA-Z-_\.]+/[0-9a-zA-Z-_\.]+#[0-9]+)(?:\s|$|\)|\]|\.(\s|$))`)
+
+	// Same as GitHub. See
+	// https://help.github.com/articles/closing-issues-via-commit-messages
+	issueCloseKeywords  = []string{"close", "closes", "closed", "fix", "fixes", "fixed", "resolve", "resolves", "resolved"}
+	issueReopenKeywords = []string{"reopen", "reopens", "reopened"}
+
+	issueCloseKeywordsPat, issueReopenKeywordsPat *regexp.Regexp
+
+	giteaHostInit sync.Once
+	giteaHost     string
+)
+
+// XRefAction represents the kind of effect a cross reference has once is resolved
+type XRefAction int64
+
+const (
+	// XRefActionNone means the cross-reference is simply a comment
+	XRefActionNone XRefAction = iota // 0
+	// XRefActionCloses means the cross-reference should close an issue if it is resolved
+	XRefActionCloses // 1
+	// XRefActionReopens means the cross-reference should reopen an issue if it is resolved
+	XRefActionReopens // 2
+	// XRefActionNeutered means the cross-reference will no longer affect the source
+	XRefActionNeutered // 3
+)
+
+// IssueReference contains an unverified cross-reference to a local issue or pull request
+type IssueReference struct {
+	Index  int64
+	Owner  string
+	Name   string
+	Action XRefAction
+}
+
+// RenderizableReference contains an unverified cross-reference to with rendering information
+type RenderizableReference struct {
+	Issue          string
+	Owner          string
+	Name           string
+	RefLocation    *RefSpan
+	Action         XRefAction
+	ActionLocation *RefSpan
+}
+
+type rawReference struct {
+	index          int64
+	owner          string
+	name           string
+	action         XRefAction
+	issue          string
+	refLocation    *RefSpan
+	actionLocation *RefSpan
+}
+
+func rawToIssueReferenceList(reflist []*rawReference) []IssueReference {
+	refarr := make([]IssueReference, len(reflist))
+	for i, r := range reflist {
+		refarr[i] = IssueReference{
+			Index:  r.index,
+			Owner:  r.owner,
+			Name:   r.name,
+			Action: r.action,
+		}
+	}
+	return refarr
+}
+
+// RefSpan is the position where the reference was found within the parsed text
+type RefSpan struct {
+	Start int
+	End   int
+}
+
+func makeKeywordsPat(keywords []string) *regexp.Regexp {
+	return regexp.MustCompile(`(?i)(?:\s|^|\(|\[)(` + strings.Join(keywords, `|`) + `):? $`)
+}
+
+func init() {
+	issueCloseKeywordsPat = makeKeywordsPat(issueCloseKeywords)
+	issueReopenKeywordsPat = makeKeywordsPat(issueReopenKeywords)
+}
+
+// getGiteaHostName returns a normalized string with the local host name, with no scheme or port information
+func getGiteaHostName() string {
+	giteaHostInit.Do(func() {
+		if uapp, err := url.Parse(setting.AppURL); err == nil {
+			giteaHost = strings.ToLower(uapp.Host)
+		} else {
+			giteaHost = ""
+		}
+	})
+	return giteaHost
+}
+
+// FindAllMentionsMarkdown matches mention patterns in given content and
+// returns a list of found unvalidated user names **not including** the @ prefix.
+func FindAllMentionsMarkdown(content string) []string {
+	bcontent, _ := mdstripper.StripMarkdownBytes([]byte(content))
+	locations := FindAllMentionsBytes(bcontent)
+	mentions := make([]string, len(locations))
+	for i, val := range locations {
+		mentions[i] = string(bcontent[val.Start+1 : val.End])
+	}
+	return mentions
+}
+
+// FindAllMentionsBytes matches mention patterns in given content
+// and returns a list of locations for the unvalidated user names, including the @ prefix.
+func FindAllMentionsBytes(content []byte) []RefSpan {
+	mentions := mentionPattern.FindAllSubmatchIndex(content, -1)
+	ret := make([]RefSpan, len(mentions))
+	for i, val := range mentions {
+		ret[i] = RefSpan{Start: val[2], End: val[3]}
+	}
+	return ret
+}
+
+// FindFirstMentionBytes matches the first mention in then given content
+// and returns the location of the unvalidated user name, including the @ prefix.
+func FindFirstMentionBytes(content []byte) (bool, RefSpan) {
+	mention := mentionPattern.FindSubmatchIndex(content)
+	if mention == nil {
+		return false, RefSpan{}
+	}
+	return true, RefSpan{Start: mention[2], End: mention[3]}
+}
+
+// FindAllIssueReferencesMarkdown strips content from markdown markup
+// and returns a list of unvalidated references found in it.
+func FindAllIssueReferencesMarkdown(content string) []IssueReference {
+	return rawToIssueReferenceList(findAllIssueReferencesMarkdown(content))
+}
+
+func findAllIssueReferencesMarkdown(content string) []*rawReference {
+	bcontent, links := mdstripper.StripMarkdownBytes([]byte(content))
+	return findAllIssueReferencesBytes(bcontent, links)
+}
+
+// FindAllIssueReferences returns a list of unvalidated references found in a string.
+func FindAllIssueReferences(content string) []IssueReference {
+	return rawToIssueReferenceList(findAllIssueReferencesBytes([]byte(content), []string{}))
+}
+
+// FindRenderizableReferenceNumeric returns the first unvalidated reference found in a string.
+func FindRenderizableReferenceNumeric(content string) (bool, *RenderizableReference) {
+	match := issueNumericPattern.FindStringSubmatchIndex(content)
+	if match == nil {
+		if match = crossReferenceIssueNumericPattern.FindStringSubmatchIndex(content); match == nil {
+			return false, nil
+		}
+	}
+	r := getCrossReference([]byte(content), match[2], match[3], false)
+	if r == nil {
+		return false, nil
+	}
+
+	return true, &RenderizableReference{
+		Issue:          r.issue,
+		Owner:          r.owner,
+		Name:           r.name,
+		RefLocation:    r.refLocation,
+		Action:         r.action,
+		ActionLocation: r.actionLocation,
+	}
+}
+
+// FindRenderizableReferenceAlphanumeric returns the first alphanumeric unvalidated references found in a string.
+func FindRenderizableReferenceAlphanumeric(content string) (bool, *RenderizableReference) {
+	match := issueAlphanumericPattern.FindStringSubmatchIndex(content)
+	if match == nil {
+		return false, nil
+	}
+
+	action, location := findActionKeywords([]byte(content), match[2])
+
+	return true, &RenderizableReference{
+		Issue:          string(content[match[2]:match[3]]),
+		RefLocation:    &RefSpan{Start: match[2], End: match[3]},
+		Action:         action,
+		ActionLocation: location,
+	}
+}
+
+// FindAllIssueReferencesBytes returns a list of unvalidated references found in a byte slice.
+func findAllIssueReferencesBytes(content []byte, links []string) []*rawReference {
+
+	ret := make([]*rawReference, 0, 10)
+
+	matches := issueNumericPattern.FindAllSubmatchIndex(content, -1)
+	for _, match := range matches {
+		if ref := getCrossReference(content, match[2], match[3], false); ref != nil {
+			ret = append(ret, ref)
+		}
+	}
+
+	matches = crossReferenceIssueNumericPattern.FindAllSubmatchIndex(content, -1)
+	for _, match := range matches {
+		if ref := getCrossReference(content, match[2], match[3], false); ref != nil {
+			ret = append(ret, ref)
+		}
+	}
+
+	localhost := getGiteaHostName()
+	for _, link := range links {
+		if u, err := url.Parse(link); err == nil {
+			// Note: we're not attempting to match the URL scheme (http/https)
+			host := strings.ToLower(u.Host)
+			if host != "" && host != localhost {
+				continue
+			}
+			parts := strings.Split(u.EscapedPath(), "/")
+			// /user/repo/issues/3
+			if len(parts) != 5 || parts[0] != "" {
+				continue
+			}
+			if parts[3] != "issues" && parts[3] != "pulls" {
+				continue
+			}
+			// Note: closing/reopening keywords not supported with URLs
+			bytes := []byte(parts[1] + "/" + parts[2] + "#" + parts[4])
+			if ref := getCrossReference(bytes, 0, len(bytes), true); ref != nil {
+				ref.refLocation = nil
+				ret = append(ret, ref)
+			}
+		}
+	}
+
+	return ret
+}
+
+func getCrossReference(content []byte, start, end int, fromLink bool) *rawReference {
+	refid := string(content[start:end])
+	parts := strings.Split(refid, "#")
+	if len(parts) != 2 {
+		return nil
+	}
+	repo, issue := parts[0], parts[1]
+	index, err := strconv.ParseInt(issue, 10, 64)
+	if err != nil {
+		return nil
+	}
+	if repo == "" {
+		if fromLink {
+			// Markdown links must specify owner/repo
+			return nil
+		}
+		action, location := findActionKeywords(content, start)
+		return &rawReference{
+			index:          index,
+			action:         action,
+			issue:          issue,
+			refLocation:    &RefSpan{Start: start, End: end},
+			actionLocation: location,
+		}
+	}
+	parts = strings.Split(strings.ToLower(repo), "/")
+	if len(parts) != 2 {
+		return nil
+	}
+	owner, name := parts[0], parts[1]
+	if !validNamePattern.MatchString(owner) || !validNamePattern.MatchString(name) {
+		return nil
+	}
+	action, location := findActionKeywords(content, start)
+	return &rawReference{
+		index:          index,
+		owner:          owner,
+		name:           name,
+		action:         action,
+		issue:          issue,
+		refLocation:    &RefSpan{Start: start, End: end},
+		actionLocation: location,
+	}
+}
+
+func findActionKeywords(content []byte, start int) (XRefAction, *RefSpan) {
+	m := issueCloseKeywordsPat.FindSubmatchIndex(content[:start])
+	if m != nil {
+		return XRefActionCloses, &RefSpan{Start: m[2], End: m[3]}
+	}
+	m = issueReopenKeywordsPat.FindSubmatchIndex(content[:start])
+	if m != nil {
+		return XRefActionReopens, &RefSpan{Start: m[2], End: m[3]}
+	}
+	return XRefActionNone, nil
+}