internal/related/related.go - oscar - Git at Google

 // Copyright 2024 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // Package related implements posting about related issues to GitHub.
 package related

 import (
 	"context"
 	"errors"
 	"fmt"
 	"log/slog"
 	"strings"
 	"time"

 	"golang.org/x/oscar/internal/docs"
 	"golang.org/x/oscar/internal/github"
 	"golang.org/x/oscar/internal/storage"
 	"golang.org/x/oscar/internal/storage/timed"
 	"rsc.io/ordered"
 )

 // A Poster posts to GitHub about related issues (and eventually other documents).
 type Poster struct {
 	slog        *slog.Logger
 	db          storage.DB
 	vdb         storage.VectorDB
 	github      *github.Client
 	docs        *docs.Corpus
 	projects    map[string]bool
 	watcher     *timed.Watcher[*github.Event]
 	name        string
 	timeLimit   time.Time
 	ignores     []func(*github.Issue) bool
 	maxResults  int
 	scoreCutoff float64
 	post        bool
 }

 // New creates and returns a new Poster. It logs to lg, stores state in db,
 // watches for new GitHub issues using gh, looks up related documents in vdb,
 // and reads the document content from docs.
 // For the purposes of storing its own state, it uses the given name.
 // Future calls to New with the same name will use the same state.
 //
 // Use the [Poster] methods to configure the posting parameters
 // (especially [Poster.EnableProject] and [Poster.EnablePosts])
 // before calling [Poster.Run].
 func New(lg *slog.Logger, db storage.DB, gh *github.Client, vdb storage.VectorDB, docs *docs.Corpus, name string) *Poster {
 	return &Poster{
 		slog:        lg,
 		db:          db,
 		vdb:         vdb,
 		github:      gh,
 		docs:        docs,
 		projects:    make(map[string]bool),
 		watcher:     gh.EventWatcher("related.Poster:" + name),
 		name:        name,
 		timeLimit:   time.Now().Add(-defaultTooOld),
 		maxResults:  defaultMaxResults,
 		scoreCutoff: defaultScoreCutoff,
 	}
 }

 // SetTimeLimit controls how old an issue can be for the Poster to post to it.
 // Issues created before time t will be skipped.
 // The default is not to post to issues that are more than 48 hours old
 // at the time of the call to [New].
 func (p *Poster) SetTimeLimit(t time.Time) {
 	p.timeLimit = t
 }

 const defaultTooOld = 48 * time.Hour

 // SetMaxResults sets the maximum number of related documents to
 // post to the issue.
 // The default is 10.
 func (p *Poster) SetMaxResults(max int) {
 	p.maxResults = max
 }

 const defaultMaxResults = 10

 // SetMinScore sets the minimum vector search score that a
 // [storage.VectorResult] must have to be considered a related document
 // The default is 0.82, which was determined empirically.
 func (p *Poster) SetMinScore(min float64) {
 	p.scoreCutoff = min
 }

 const defaultScoreCutoff = 0.82

 // SkipBodyContains configures the Poster to skip issues with a body containing
 // the given text.
 func (p *Poster) SkipBodyContains(text string) {
 	p.ignores = append(p.ignores, func(issue *github.Issue) bool {
 		return strings.Contains(issue.Body, text)
 	})
 }

 // SkipTitlePrefix configures the Poster to skip issues with a title starting
 // with the given prefix.
 func (p *Poster) SkipTitlePrefix(prefix string) {
 	p.ignores = append(p.ignores, func(issue *github.Issue) bool {
 		return strings.HasPrefix(issue.Title, prefix)
 	})
 }

 // SkipTitleSuffix configures the Poster to skip issues with a title starting
 // with the given suffix.
 func (p *Poster) SkipTitleSuffix(suffix string) {
 	p.ignores = append(p.ignores, func(issue *github.Issue) bool {
 		return strings.HasSuffix(issue.Title, suffix)
 	})
 }

 // EnableProject enables the Poster to post on issues in the given GitHub project (for example "golang/go").
 // See also [Poster.EnablePosts], which must also be called to post anything to GitHub.
 func (p *Poster) EnableProject(project string) {
 	p.projects[project] = true
 }

 // EnablePosts enables the Poster to post to GitHub.
 // If EnablePosts has not been called, [Poster.Run] logs what it would post but does not post the messages.
 // See also [Poster.EnableProject], which must also be called to set the projects being considered.
 func (p *Poster) EnablePosts() {
 	p.post = true
 }

 // deletePosted deletes all the “posted on this issue” notes.
 func (p *Poster) deletePosted() {
 	p.db.DeleteRange(ordered.Encode("triage.Posted"), ordered.Encode("triage.Posted", ordered.Inf))
 }

 // Run runs a single round of posting to GitHub.
 // It scans all open issues that have been created since the last call to [Poster.Run]
 // using a Poster with the same name (see [New]).
 // Run skips closed issues, and it also skips pull requests.
 //
 // For each issue that matches the configured posting constraints
 // (see [Poster.EnableProject], [Poster.SetTimeLimit], [Poster.IgnoreBodyContains], [Poster.IgnoreTitlePrefix], and [Poster.IgnoreTitleSuffix]),
 // Run computes an embedding of the issue body text (ignoring comments)
 // and looks in the vector database for other documents (currently only issues)
 // that are aligned closely enough with that body text
 // (see [Poster.SetMinScore]) and posts a limited number of matches
 // (see [Poster.SetMaxResults]).
 //
 // Run logs each post to the [slog.Logger] passed to [New].
 // If [Poster.EnablePosts] has been called, then [Run] also posts the comment to GitHub,
 // records in the database that it has posted to GitHub to make sure it never posts to that issue again,
 // and advances its GitHub issue watcher's incremental cursor to speed future calls to [Run].
 //
 // When [Poster.EnablePosts] has not been called, Run only logs the comments it would post.
 // Future calls to Run will reprocess the same issues and re-log the same comments.
 func (p *Poster) Run(ctx context.Context) error {
 	p.slog.Info("related.Poster start", "name", p.name, "post", p.post, "latest", p.watcher.Latest())
 	defer func() {
 		p.slog.Info("related.Poster end", "name", p.name, "latest", p.watcher.Latest())
 	}()

 	defer p.watcher.Flush()
 	for e := range p.watcher.Recent() {
 		advance, err := p.postIssue(ctx, e)
 		if err != nil {
 			p.slog.Error("related.Poster", "issue", e.Issue, "event", e, "error", err)
 			continue
 		}
 		if advance {
 			p.watcher.MarkOld(e.DBTime)
 			// Flush immediately to make sure we don't re-post if interrupted later in the loop.
 			p.watcher.Flush()
 			p.slog.Info("related.Poster advanced watcher", "latest", p.watcher.Latest(), "event", e)
 		} else {
 			p.slog.Info("related.Poster watcher not advanced", "latest", p.watcher.Latest(), "event", e)
 		}
 	}
 	return nil
 }

 // Post posts an issue comment for the given GitHub issue.
 //
 // It follows the same logic as [Poster.Run] for a single event, except
 // that it does not rely on or modify the Poster's GitHub issue watcher's
 // incremental cursor.
 // This means that [Poster.Post] can be called on any issue event without
 // affecting the starting point of future calls to [Poster.Run].
 //
 // It requires that there be a database and vector database entry for
 // the given issue.
 func (p *Poster) Post(ctx context.Context, project string, issue int64) error {
 	e := lookupIssueEvent(project, issue, p.github)
 	if e == nil {
 		return fmt.Errorf("related.Poster.Post(project=%s, issue=%d): %w", project, issue, errEventNotFound)
 	}
 	_, err := p.postIssue(ctx, e)
 	return err
 }

 var (
 	errEventNotFound          = errors.New("event not found in database")
 	errVectorSearchFailed     = errors.New("vector search failed")
 	errPostIssueCommentFailed = errors.New("post issue comment failed")
 )

 // lookupIssueEvent returns the first event for the "/issues" API with
 // the given ID in the database, or nil if not found.
 func lookupIssueEvent(project string, issue int64, gh *github.Client) *github.Event {
 	for event := range gh.Events(project, issue, issue) {
 		if event.API == "/issues" {
 			return event
 		}
 	}
 	return nil
 }

 // postIssue posts an issue for the event.
 // advance is true if the event should be considered to have been
 // handled by this or a previous run function, indicating
 // that the Poster's watcher can be advanced.
 // An issue is handled if
 //   - posting is enabled, AND
 //   - an issue was successfully posted, or no issue was needed
 //     because no related documents were found
 //
 // Skipped issues are not considered handled.
 func (p *Poster) postIssue(ctx context.Context, e *github.Event) (advance bool, _ error) {
 	if skip, reason := p.skip(e); skip {
 		p.slog.Info("related.Poster skip", "name", p.name, "project",
 			e.Project, "issue", e.Issue, "reason", reason, "event", e)
 		return false, nil
 	}

 	// Lock before checking if an issue was already posted for this event.
 	lock := string(postedKey(e))
 	p.db.Lock(lock)
 	defer p.db.Unlock(lock)

 	if p.posted(e) {
 		p.slog.Info("related.Poster already posted", "name", p.name, "project", e.Project, "issue", e.Issue, "event", e)
 		// If posting is enabled, we can advance the watcher because
 		// a comment has already been posted for this issue.
 		return p.post, nil
 	}

 	u := issueURL(e.Project, e.Issue)
 	p.slog.Debug("related.Poster consider", "url", u)
 	results, ok := p.search(u)
 	if !ok {
 		return false, fmt.Errorf("%w url=%s", errVectorSearchFailed, u)
 	}
 	if len(results) == 0 {
 		p.slog.Info("related.Poster found no related documents", "name", p.name, "project", e.Project, "issue", e.Issue, "event", e)
 		// If posting is enabled, an issue with no related documents
 		// should be considered handled, and not looked at again.
 		return p.post, nil
 	}
 	comment := p.comment(results)
 	p.slog.Info("related.Poster post", "name", p.name, "project", e.Project, "issue", e.Issue, "comment", comment)

 	if !p.post {
 		// Posting is disabled so we did not handle this issue.
 		return false, nil
 	}

 	issue := e.Typed.(*github.Issue)
 	if err := p.github.PostIssueComment(ctx, issue, &github.IssueCommentChanges{Body: comment}); err != nil {
 		return false, fmt.Errorf("%w issue=%d: %v", errPostIssueCommentFailed, issue.Number, err)
 	}

 	p.markPosted(e)
 	return true, nil
 }

 // issueURL returns the URL of the GitHub issue in the given project.
 func issueURL(project string, issue int64) string {
 	return fmt.Sprintf("https://github.com/%s/issues/%d", project, issue)
 }

 // search performs a vector search to find related issues for the given
 // issue URL. It removes any results that don't meet the cutoff in
 // p.scoreCutoff and trims the results list to a max length of p.maxResults.
 // It expects that there is already an entry for the url in the vector
 // database, and returns ok=false if there is no such entry.
 func (p *Poster) search(u string) (_ []storage.VectorResult, ok bool) {
 	vec, ok := p.vdb.Get(u)
 	if !ok {
 		return nil, false
 	}
 	results := p.vdb.Search(vec, p.maxResults+5)
 	if len(results) > 0 && results[0].ID == u {
 		results = results[1:]
 	}
 	for i, r := range results {
 		if r.Score < p.scoreCutoff {
 			results = results[:i]
 			break
 		}
 	}
 	if len(results) > p.maxResults {
 		results = results[:p.maxResults]
 	}
 	return results, true
 }

 // comment returns the comment to post to GitHub for the given related
 // issues.
 func (p *Poster) comment(results []storage.VectorResult) string {
 	var comment strings.Builder
 	fmt.Fprintf(&comment, "**Related Issues and Documentation**\n\n")
 	for _, r := range results {
 		title := r.ID
 		if d, ok := p.docs.Get(r.ID); ok {
 			title = d.Title
 		}
 		info := ""
 		if issue, err := p.github.LookupIssueURL(r.ID); err == nil {
 			info = fmt.Sprint(" #", issue.Number)
 			if issue.ClosedAt != "" {
 				info += " (closed)"
 			}
 		}
 		fmt.Fprintf(&comment, " - [%s%s](%s) <!-- score=%.5f -->\n", markdownEscape(title), info, r.ID, r.Score)
 	}
 	fmt.Fprintf(&comment, "\n<sub>(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in [this discussion](https://github.com/golang/go/discussions/67901).)</sub>\n")
 	return comment.String()
 }

 // skip reports whether the event should be skipped and why.
 func (p *Poster) skip(e *github.Event) (_ bool, reason string) {
 	if !p.projects[e.Project] {
 		return true, fmt.Sprintf("project %s not enabled for this Poster", e.Project)
 	}
 	if e.API != "/issues" {
 		return true, fmt.Sprintf("wrong API %s (expected %s)", e.API, "/issues")
 	}
 	issue := e.Typed.(*github.Issue)
 	if issue.State == "closed" {
 		return true, "issue is closed"
 	}
 	if issue.PullRequest != nil {
 		return true, "pull request"
 	}
 	tm, err := time.Parse(time.RFC3339, issue.CreatedAt)
 	if err != nil {
 		p.slog.Error("related.Poster parse createdat", "CreatedAt", issue.CreatedAt, "err", err)
 		return true, "could not parse createdat"
 	}
 	if tm.Before(p.timeLimit) {
 		return true, fmt.Sprintf("created=%s before time limit=%s", tm, p.timeLimit)
 	}
 	for i, ig := range p.ignores {
 		if ig(issue) {
 			return true, fmt.Sprintf("ignored by function ignores[%d]", i)
 		}
 	}
 	return false, ""
 }

 // posted reports whether the event has already been posted.
 func (p *Poster) posted(e *github.Event) bool {
 	_, ok := p.db.Get(postedKey(e))
 	return ok
 }

 // markPosted records that the event has been posted.
 func (p *Poster) markPosted(e *github.Event) {
 	p.db.Set(postedKey(e), nil)
 	p.db.Flush()
 }

 // postedKey returns the database key to use when marking an event as posted.
 func postedKey(e *github.Event) []byte {
 	// TODO: Perhaps this key should include p.name, but perhaps not.
 	// This makes sure we only ever post to each issue once.
 	return ordered.Encode("triage.Posted", e.Project, e.Issue)
 }

 // Latest returns the latest known DBTime marked old by the Poster's Watcher.
 func (p *Poster) Latest() timed.DBTime {
 	return p.watcher.Latest()
 }

 var markdownEscaper = strings.NewReplacer(
 	"_", `\_`,
 	"*", `\*`,
 	"`", "\\`",
 	"[", `\[`,
 	"]", `\]`,
 	"<", `\<`,
 	">", `\>`,
 	"&", `\&`,
 )

 func markdownEscape(s string) string {
 	return markdownEscaper.Replace(s)
 }
	// Copyright 2024 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// Package related implements posting about related issues to GitHub.
	package related

	import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"golang.org/x/oscar/internal/docs"
	"golang.org/x/oscar/internal/github"
	"golang.org/x/oscar/internal/storage"
	"golang.org/x/oscar/internal/storage/timed"
	"rsc.io/ordered"
	)

	// A Poster posts to GitHub about related issues (and eventually other documents).
	type Poster struct {
	slog *slog.Logger
	db storage.DB
	vdb storage.VectorDB
	github *github.Client
	docs *docs.Corpus
	projects map[string]bool
	watcher timed.Watcher[github.Event]
	name string
	timeLimit time.Time
	ignores []func(*github.Issue) bool
	maxResults int
	scoreCutoff float64
	post bool
	}

	// New creates and returns a new Poster. It logs to lg, stores state in db,
	// watches for new GitHub issues using gh, looks up related documents in vdb,
	// and reads the document content from docs.
	// For the purposes of storing its own state, it uses the given name.
	// Future calls to New with the same name will use the same state.
	//
	// Use the [Poster] methods to configure the posting parameters
	// (especially [Poster.EnableProject] and [Poster.EnablePosts])
	// before calling [Poster.Run].
	func New(lg slog.Logger, db storage.DB, gh github.Client, vdb storage.VectorDB, docs docs.Corpus, name string) Poster {
	return &Poster{
	slog: lg,
	db: db,
	vdb: vdb,
	github: gh,
	docs: docs,
	projects: make(map[string]bool),
	watcher: gh.EventWatcher("related.Poster:" + name),
	name: name,
	timeLimit: time.Now().Add(-defaultTooOld),
	maxResults: defaultMaxResults,
	scoreCutoff: defaultScoreCutoff,
	}
	}

	// SetTimeLimit controls how old an issue can be for the Poster to post to it.
	// Issues created before time t will be skipped.
	// The default is not to post to issues that are more than 48 hours old
	// at the time of the call to [New].
	func (p *Poster) SetTimeLimit(t time.Time) {
	p.timeLimit = t
	}

	const defaultTooOld = 48 * time.Hour

	// SetMaxResults sets the maximum number of related documents to
	// post to the issue.
	// The default is 10.
	func (p *Poster) SetMaxResults(max int) {
	p.maxResults = max
	}

	const defaultMaxResults = 10

	// SetMinScore sets the minimum vector search score that a
	// [storage.VectorResult] must have to be considered a related document
	// The default is 0.82, which was determined empirically.
	func (p *Poster) SetMinScore(min float64) {
	p.scoreCutoff = min
	}

	const defaultScoreCutoff = 0.82

	// SkipBodyContains configures the Poster to skip issues with a body containing
	// the given text.
	func (p *Poster) SkipBodyContains(text string) {
	p.ignores = append(p.ignores, func(issue *github.Issue) bool {
	return strings.Contains(issue.Body, text)
	})
	}

	// SkipTitlePrefix configures the Poster to skip issues with a title starting
	// with the given prefix.
	func (p *Poster) SkipTitlePrefix(prefix string) {
	p.ignores = append(p.ignores, func(issue *github.Issue) bool {
	return strings.HasPrefix(issue.Title, prefix)
	})
	}

	// SkipTitleSuffix configures the Poster to skip issues with a title starting
	// with the given suffix.
	func (p *Poster) SkipTitleSuffix(suffix string) {
	p.ignores = append(p.ignores, func(issue *github.Issue) bool {
	return strings.HasSuffix(issue.Title, suffix)
	})
	}

	// EnableProject enables the Poster to post on issues in the given GitHub project (for example "golang/go").
	// See also [Poster.EnablePosts], which must also be called to post anything to GitHub.
	func (p *Poster) EnableProject(project string) {
	p.projects[project] = true
	}

	// EnablePosts enables the Poster to post to GitHub.
	// If EnablePosts has not been called, [Poster.Run] logs what it would post but does not post the messages.
	// See also [Poster.EnableProject], which must also be called to set the projects being considered.
	func (p *Poster) EnablePosts() {
	p.post = true
	}

	// deletePosted deletes all the “posted on this issue” notes.
	func (p *Poster) deletePosted() {
	p.db.DeleteRange(ordered.Encode("triage.Posted"), ordered.Encode("triage.Posted", ordered.Inf))
	}

	// Run runs a single round of posting to GitHub.
	// It scans all open issues that have been created since the last call to [Poster.Run]
	// using a Poster with the same name (see [New]).
	// Run skips closed issues, and it also skips pull requests.
	//
	// For each issue that matches the configured posting constraints
	// (see [Poster.EnableProject], [Poster.SetTimeLimit], [Poster.IgnoreBodyContains], [Poster.IgnoreTitlePrefix], and [Poster.IgnoreTitleSuffix]),
	// Run computes an embedding of the issue body text (ignoring comments)
	// and looks in the vector database for other documents (currently only issues)
	// that are aligned closely enough with that body text
	// (see [Poster.SetMinScore]) and posts a limited number of matches
	// (see [Poster.SetMaxResults]).
	//
	// Run logs each post to the [slog.Logger] passed to [New].
	// If [Poster.EnablePosts] has been called, then [Run] also posts the comment to GitHub,
	// records in the database that it has posted to GitHub to make sure it never posts to that issue again,
	// and advances its GitHub issue watcher's incremental cursor to speed future calls to [Run].
	//
	// When [Poster.EnablePosts] has not been called, Run only logs the comments it would post.
	// Future calls to Run will reprocess the same issues and re-log the same comments.
	func (p *Poster) Run(ctx context.Context) error {
	p.slog.Info("related.Poster start", "name", p.name, "post", p.post, "latest", p.watcher.Latest())
	defer func() {
	p.slog.Info("related.Poster end", "name", p.name, "latest", p.watcher.Latest())
	}()

	defer p.watcher.Flush()
	for e := range p.watcher.Recent() {
	advance, err := p.postIssue(ctx, e)
	if err != nil {
	p.slog.Error("related.Poster", "issue", e.Issue, "event", e, "error", err)
	continue
	}
	if advance {
	p.watcher.MarkOld(e.DBTime)
	// Flush immediately to make sure we don't re-post if interrupted later in the loop.
	p.watcher.Flush()
	p.slog.Info("related.Poster advanced watcher", "latest", p.watcher.Latest(), "event", e)
	} else {
	p.slog.Info("related.Poster watcher not advanced", "latest", p.watcher.Latest(), "event", e)
	}
	}
	return nil
	}

	// Post posts an issue comment for the given GitHub issue.
	//
	// It follows the same logic as [Poster.Run] for a single event, except
	// that it does not rely on or modify the Poster's GitHub issue watcher's
	// incremental cursor.
	// This means that [Poster.Post] can be called on any issue event without
	// affecting the starting point of future calls to [Poster.Run].
	//
	// It requires that there be a database and vector database entry for
	// the given issue.
	func (p *Poster) Post(ctx context.Context, project string, issue int64) error {
	e := lookupIssueEvent(project, issue, p.github)
	if e == nil {
	return fmt.Errorf("related.Poster.Post(project=%s, issue=%d): %w", project, issue, errEventNotFound)
	}
	_, err := p.postIssue(ctx, e)
	return err
	}

	var (
	errEventNotFound = errors.New("event not found in database")
	errVectorSearchFailed = errors.New("vector search failed")
	errPostIssueCommentFailed = errors.New("post issue comment failed")
	)

	// lookupIssueEvent returns the first event for the "/issues" API with
	// the given ID in the database, or nil if not found.
	func lookupIssueEvent(project string, issue int64, gh github.Client) github.Event {
	for event := range gh.Events(project, issue, issue) {
	if event.API == "/issues" {
	return event
	}
	}
	return nil
	}

	// postIssue posts an issue for the event.
	// advance is true if the event should be considered to have been
	// handled by this or a previous run function, indicating
	// that the Poster's watcher can be advanced.
	// An issue is handled if
	// - posting is enabled, AND
	// - an issue was successfully posted, or no issue was needed
	// because no related documents were found
	//
	// Skipped issues are not considered handled.
	func (p Poster) postIssue(ctx context.Context, e github.Event) (advance bool, _ error) {
	if skip, reason := p.skip(e); skip {
	p.slog.Info("related.Poster skip", "name", p.name, "project",
	e.Project, "issue", e.Issue, "reason", reason, "event", e)
	return false, nil
	}

	// Lock before checking if an issue was already posted for this event.
	lock := string(postedKey(e))
	p.db.Lock(lock)
	defer p.db.Unlock(lock)

	if p.posted(e) {
	p.slog.Info("related.Poster already posted", "name", p.name, "project", e.Project, "issue", e.Issue, "event", e)
	// If posting is enabled, we can advance the watcher because
	// a comment has already been posted for this issue.
	return p.post, nil
	}

	u := issueURL(e.Project, e.Issue)
	p.slog.Debug("related.Poster consider", "url", u)
	results, ok := p.search(u)
	if !ok {
	return false, fmt.Errorf("%w url=%s", errVectorSearchFailed, u)
	}
	if len(results) == 0 {
	p.slog.Info("related.Poster found no related documents", "name", p.name, "project", e.Project, "issue", e.Issue, "event", e)
	// If posting is enabled, an issue with no related documents
	// should be considered handled, and not looked at again.
	return p.post, nil
	}
	comment := p.comment(results)
	p.slog.Info("related.Poster post", "name", p.name, "project", e.Project, "issue", e.Issue, "comment", comment)

	if !p.post {
	// Posting is disabled so we did not handle this issue.
	return false, nil
	}

	issue := e.Typed.(*github.Issue)
	if err := p.github.PostIssueComment(ctx, issue, &github.IssueCommentChanges{Body: comment}); err != nil {
	return false, fmt.Errorf("%w issue=%d: %v", errPostIssueCommentFailed, issue.Number, err)
	}

	p.markPosted(e)
	return true, nil
	}

	// issueURL returns the URL of the GitHub issue in the given project.
	func issueURL(project string, issue int64) string {
	return fmt.Sprintf("https://github.com/%s/issues/%d", project, issue)
	}

	// search performs a vector search to find related issues for the given
	// issue URL. It removes any results that don't meet the cutoff in
	// p.scoreCutoff and trims the results list to a max length of p.maxResults.
	// It expects that there is already an entry for the url in the vector
	// database, and returns ok=false if there is no such entry.
	func (p *Poster) search(u string) (_ []storage.VectorResult, ok bool) {
	vec, ok := p.vdb.Get(u)
	if !ok {
	return nil, false
	}
	results := p.vdb.Search(vec, p.maxResults+5)
	if len(results) > 0 && results[0].ID == u {
	results = results[1:]
	}
	for i, r := range results {
	if r.Score < p.scoreCutoff {
	results = results[:i]
	break
	}
	}
	if len(results) > p.maxResults {
	results = results[:p.maxResults]
	}
	return results, true
	}

	// comment returns the comment to post to GitHub for the given related
	// issues.
	func (p *Poster) comment(results []storage.VectorResult) string {
	var comment strings.Builder
	fmt.Fprintf(&comment, "Related Issues and Documentation\n\n")
	for _, r := range results {
	title := r.ID
	if d, ok := p.docs.Get(r.ID); ok {
	title = d.Title
	}
	info := ""
	if issue, err := p.github.LookupIssueURL(r.ID); err == nil {
	info = fmt.Sprint(" #", issue.Number)
	if issue.ClosedAt != "" {
	info += " (closed)"
	}
	}
	fmt.Fprintf(&comment, " - [%s%s](%s) <!-- score=%.5f -->\n", markdownEscape(title), info, r.ID, r.Score)
	}
	fmt.Fprintf(&comment, "\n<sub>(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in [this discussion](https://github.com/golang/go/discussions/67901).)</sub>\n")
	return comment.String()
	}

	// skip reports whether the event should be skipped and why.
	func (p Poster) skip(e github.Event) (_ bool, reason string) {
	if !p.projects[e.Project] {
	return true, fmt.Sprintf("project %s not enabled for this Poster", e.Project)
	}
	if e.API != "/issues" {
	return true, fmt.Sprintf("wrong API %s (expected %s)", e.API, "/issues")
	}
	issue := e.Typed.(*github.Issue)
	if issue.State == "closed" {
	return true, "issue is closed"
	}
	if issue.PullRequest != nil {
	return true, "pull request"
	}
	tm, err := time.Parse(time.RFC3339, issue.CreatedAt)
	if err != nil {
	p.slog.Error("related.Poster parse createdat", "CreatedAt", issue.CreatedAt, "err", err)
	return true, "could not parse createdat"
	}
	if tm.Before(p.timeLimit) {
	return true, fmt.Sprintf("created=%s before time limit=%s", tm, p.timeLimit)
	}
	for i, ig := range p.ignores {
	if ig(issue) {
	return true, fmt.Sprintf("ignored by function ignores[%d]", i)
	}
	}
	return false, ""
	}

	// posted reports whether the event has already been posted.
	func (p Poster) posted(e github.Event) bool {
	_, ok := p.db.Get(postedKey(e))
	return ok
	}

	// markPosted records that the event has been posted.
	func (p Poster) markPosted(e github.Event) {
	p.db.Set(postedKey(e), nil)
	p.db.Flush()
	}

	// postedKey returns the database key to use when marking an event as posted.
	func postedKey(e *github.Event) []byte {
	// TODO: Perhaps this key should include p.name, but perhaps not.
	// This makes sure we only ever post to each issue once.
	return ordered.Encode("triage.Posted", e.Project, e.Issue)
	}

	// Latest returns the latest known DBTime marked old by the Poster's Watcher.
	func (p *Poster) Latest() timed.DBTime {
	return p.watcher.Latest()
	}

	var markdownEscaper = strings.NewReplacer(
	"_", `\_`,
	"", `\`,
	"`", "\\`",
	"[", `\[`,
	"]", `\]`,
	"<", `\<`,
	">", `\>`,
	"&", `\&`,
	)

	func markdownEscape(s string) string {
	return markdownEscaper.Replace(s)
	}