// Copyright 2021 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 relui

import (
	"archive/tar"
	"archive/zip"
	"bytes"
	"compress/flate"
	"compress/gzip"
	"context"
	"crypto/sha256"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"math/rand"
	"net/http"
	"path"
	"sort"
	"strings"
	"sync"
	"time"

	"cloud.google.com/go/storage"
	"github.com/google/go-cmp/cmp"
	"golang.org/x/build/buildlet"
	"golang.org/x/build/dashboard"
	"golang.org/x/build/internal/gcsfs"
	"golang.org/x/build/internal/releasetargets"
	"golang.org/x/build/internal/relui/db"
	"golang.org/x/build/internal/relui/sign"
	"golang.org/x/build/internal/task"
	"golang.org/x/build/internal/workflow"
	wf "golang.org/x/build/internal/workflow"
	"golang.org/x/net/context/ctxhttp"
)

// DefinitionHolder holds workflow definitions.
type DefinitionHolder struct {
	mu          sync.Mutex
	definitions map[string]*wf.Definition
}

// NewDefinitionHolder creates a new DefinitionHolder,
// initialized with a sample "echo" wf.
func NewDefinitionHolder() *DefinitionHolder {
	return &DefinitionHolder{definitions: map[string]*wf.Definition{
		"echo": newEchoWorkflow(),
	}}
}

// Definition returns the initialized wf.Definition registered
// for a given name.
func (h *DefinitionHolder) Definition(name string) *wf.Definition {
	h.mu.Lock()
	defer h.mu.Unlock()
	return h.definitions[name]
}

// RegisterDefinition registers a definition with a name.
// If a definition with the same name already exists, RegisterDefinition panics.
func (h *DefinitionHolder) RegisterDefinition(name string, d *wf.Definition) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if _, exist := h.definitions[name]; exist {
		panic("relui: multiple registrations for " + name)
	}
	h.definitions[name] = d
}

// Definitions returns the names of all registered definitions.
func (h *DefinitionHolder) Definitions() map[string]*wf.Definition {
	h.mu.Lock()
	defer h.mu.Unlock()
	defs := make(map[string]*wf.Definition)
	for k, v := range h.definitions {
		defs[k] = v
	}
	return defs
}

// Release parameter definitions.
var (
	targetDateParam = wf.ParamDef[task.Date]{
		Name: "Target Release Date",
		ParamType: wf.ParamType[task.Date]{
			HTMLElement:   "input",
			HTMLInputType: "date",
		},
		Doc: `Target Release Date is the date on which the release is scheduled.

It must be three to seven days after the pre-announcement as documented in the security policy.`,
	}
	securityPreAnnParam = wf.ParamDef[string]{
		Name: "Security Content",
		ParamType: workflow.ParamType[string]{
			HTMLElement: "select",
			HTMLSelectOptions: []string{
				"the standard library",
				"the toolchain",
				"the standard library and the toolchain",
			},
		},
		Doc: `Security Content is the security content to be included in the release pre-announcement.

It must not reveal details beyond what's allowed by the security policy.`,
	}
	securityPreAnnCVEsParam = wf.ParamDef[[]string]{
		Name:      "PRIVATE-track CVEs",
		ParamType: wf.SliceShort,
		Example:   "CVE-2023-XXXX",
		Doc:       "List of CVEs for PRIVATE track fixes contained in the release to be included in the pre-announcement.",
	}

	securitySummaryParameter = wf.ParamDef[string]{
		Name: "Security Summary (optional)",
		Doc: `Security Summary is an optional sentence describing security fixes included in this release.

It shows up in the release tweet.

The empty string means there are no security fixes to highlight.

Past examples:
• "Includes a security fix for crypto/tls (CVE-2021-34558)."
• "Includes a security fix for the Wasm port (CVE-2021-38297)."
• "Includes security fixes for encoding/pem (CVE-2022-24675), crypto/elliptic (CVE-2022-28327), crypto/x509 (CVE-2022-27536)."`,
	}

	securityFixesParameter = wf.ParamDef[[]string]{
		Name:      "Security Fixes (optional)",
		ParamType: wf.SliceLong,
		Doc: `Security Fixes is a list of descriptions, one for each distinct security fix included in this release, in Markdown format.

It shows up in the announcement mail.

The empty list means there are no security fixes included.

Past examples:
• "encoding/pem: fix stack overflow in Decode

   A large (more than 5 MB) PEM input can cause a stack overflow in Decode,
   leading the program to crash.

   Thanks to Juho Nurminen of Mattermost who reported the error.

   This is CVE-2022-24675 and Go issue https://go.dev/issue/51853."
• "crypto/elliptic: tolerate all oversized scalars in generic P-256

   A crafted scalar input longer than 32 bytes can cause P256().ScalarMult
   or P256().ScalarBaseMult to panic. Indirect uses through crypto/ecdsa and
   crypto/tls are unaffected. amd64, arm64, ppc64le, and s390x are unaffected.

   This was discovered thanks to a Project Wycheproof test vector.

   This is CVE-2022-28327 and Go issue https://go.dev/issue/52075."`,
		Example: `encoding/pem: fix stack overflow in Decode

A large (more than 5 MB) PEM input can cause a stack overflow in Decode,
leading the program to crash.

Thanks to Juho Nurminen of Mattermost who reported the error.

This is CVE-2022-24675 and Go issue https://go.dev/issue/51853.`,
	}

	releaseCoordinators = wf.ParamDef[[]string]{
		Name:      "Release Coordinator Usernames (optional)",
		ParamType: wf.SliceShort,
		Doc: `Release Coordinator Usernames is an optional list of the coordinators of the release.

Their first names will be included at the end of the release announcement, and CLs will be mailed to them.`,
		Example: "heschi",
		Check:   task.CheckCoordinators,
	}
)

// newEchoWorkflow returns a runnable wf.Definition for
// development.
func newEchoWorkflow() *wf.Definition {
	wd := wf.New()
	wf.Output(wd, "greeting", wf.Task1(wd, "greeting", echo, wf.Param(wd, wf.ParamDef[string]{Name: "greeting"})))
	wf.Output(wd, "farewell", wf.Task1(wd, "farewell", echo, wf.Param(wd, wf.ParamDef[string]{Name: "farewell"})))
	return wd
}

func echo(ctx *wf.TaskContext, arg string) (string, error) {
	ctx.Printf("echo(%v, %q)", ctx, arg)
	return arg, nil
}

func checkTaskApproved(ctx *wf.TaskContext, p db.PGDBTX) (bool, error) {
	q := db.New(p)
	t, err := q.Task(ctx, db.TaskParams{
		Name:       ctx.TaskName,
		WorkflowID: ctx.WorkflowID,
	})
	if !t.ReadyForApproval {
		_, err := q.UpdateTaskReadyForApproval(ctx, db.UpdateTaskReadyForApprovalParams{
			ReadyForApproval: true,
			Name:             ctx.TaskName,
			WorkflowID:       ctx.WorkflowID,
		})
		if err != nil {
			return false, err
		}
	}
	return t.ApprovedAt.Valid, err
}

// ApproveActionDep returns a function for defining approval Actions.
//
// ApproveActionDep takes a single *pgxpool.Pool argument, which is
// used to query the database to determine if a task has been marked
// approved.
//
// ApproveActionDep marks the task as requiring approval in the
// database once the task is started. This can be used to show an
// "approve" control in the UI.
//
//	waitAction := wf.ActionN(wd, "Wait for Approval", ApproveActionDep(db), wf.After(someDependency))
func ApproveActionDep(p db.PGDBTX) func(*wf.TaskContext) error {
	return func(ctx *wf.TaskContext) error {
		_, err := task.AwaitCondition(ctx, 5*time.Second, func() (int, bool, error) {
			done, err := checkTaskApproved(ctx, p)
			return 0, done, err
		})
		return err
	}
}

// RegisterReleaseWorkflows registers workflows for issuing Go releases.
func RegisterReleaseWorkflows(ctx context.Context, h *DefinitionHolder, build *BuildReleaseTasks, milestone *task.MilestoneTasks, version *task.VersionTasks, comm task.CommunicationTasks) error {
	// Register prod release workflows.
	if err := registerProdReleaseWorkflows(ctx, h, build, milestone, version, comm); err != nil {
		return err
	}

	// Register pre-announcement workflows.
	currentMajor, _, err := version.GetCurrentMajor(ctx)
	if err != nil {
		return err
	}
	releases := []struct {
		kinds []task.ReleaseKind
		name  string
	}{
		{[]task.ReleaseKind{task.KindCurrentMinor, task.KindPrevMinor}, fmt.Sprintf("next minor release for Go 1.%d and 1.%d", currentMajor, currentMajor-1)},
		{[]task.ReleaseKind{task.KindCurrentMinor}, fmt.Sprintf("next minor release for Go 1.%d", currentMajor)},
		{[]task.ReleaseKind{task.KindPrevMinor}, fmt.Sprintf("next minor release for Go 1.%d", currentMajor-1)},
	}
	for _, r := range releases {
		wd := wf.New()

		versions := wf.Task1(wd, "Get next versions", version.GetNextVersions, wf.Const(r.kinds))
		targetDate := wf.Param(wd, targetDateParam)
		securityContent := wf.Param(wd, securityPreAnnParam)
		cves := wf.Param(wd, securityPreAnnCVEsParam)
		coordinators := wf.Param(wd, releaseCoordinators)

		sentMail := wf.Task5(wd, "mail-pre-announcement", comm.PreAnnounceRelease, versions, targetDate, securityContent, cves, coordinators)
		wf.Output(wd, "Pre-announcement URL", wf.Task1(wd, "await-pre-announcement", comm.AwaitAnnounceMail, sentMail))

		h.RegisterDefinition("pre-announce "+r.name, wd)
	}

	// Register workflows for miscellaneous tasks that happen as part of the Go release cycle.
	{
		// Register a "ping early-in-cycle issues" workflow.
		wd := wf.New()
		openTreeURL := wf.Param(wd, wf.ParamDef[string]{
			Name:    "Open Tree URL",
			Doc:     `Open Tree URL is the URL of an announcement that the tree is open for general Go 1.x development.`,
			Example: "https://groups.google.com/g/golang-dev/c/09IwUs7cxXA/m/c2jyIhECBQAJ",
			Check: func(openTreeURL string) error {
				if !strings.HasPrefix(openTreeURL, "https://groups.google.com/g/golang-dev/c/") {
					return fmt.Errorf("openTreeURL value %q doesn't begin with the usual prefix, so please double-check that the URL is correct", openTreeURL)
				}
				return nil
			},
		})
		devVer := wf.Task0(wd, "Get development version", version.GetDevelVersion)
		pinged := wf.Task2(wd, "Ping early-in-cycle issues", milestone.PingEarlyIssues, devVer, openTreeURL)
		wf.Output(wd, "pinged", pinged)
		h.RegisterDefinition("ping early-in-cycle issues in development milestone", wd)
	}
	{
		// Register an "unwait wait-release CLs" workflow.
		wd := wf.New()
		unwaited := wf.Task0(wd, "Unwait wait-release CLs", version.UnwaitWaitReleaseCLs)
		wf.Output(wd, "unwaited", unwaited)
		h.RegisterDefinition("unwait wait-release CLs", wd)
	}

	// Register dry-run release workflows.
	registerBuildTestSignOnlyWorkflow(h, version, build, currentMajor+1, task.KindBeta)

	return nil
}

func registerProdReleaseWorkflows(ctx context.Context, h *DefinitionHolder, build *BuildReleaseTasks, milestone *task.MilestoneTasks, version *task.VersionTasks, comm task.CommunicationTasks) error {
	currentMajor, majorReleaseTime, err := version.GetCurrentMajor(ctx)
	if err != nil {
		return err
	}
	type release struct {
		kind   task.ReleaseKind
		major  int
		suffix string
	}
	releases := []release{
		{task.KindMajor, currentMajor + 1, "final"},
		{task.KindRC, currentMajor + 1, "next RC"},
		{task.KindBeta, currentMajor + 1, "next beta"},
		{task.KindCurrentMinor, currentMajor, "next minor"},
		{task.KindPrevMinor, currentMajor - 1, "next minor"},
	}
	if time.Since(majorReleaseTime) < 7*24*time.Hour {
		releases = append(releases, release{task.KindMajor, currentMajor, "final"})
	}
	for _, r := range releases {
		wd := wf.New()

		coordinators := wf.Param(wd, releaseCoordinators)

		published := addSingleReleaseWorkflow(build, milestone, version, wd, r.major, r.kind, coordinators)

		securitySummary := wf.Const("")
		securityFixes := wf.Slice[string]()
		if r.kind == task.KindCurrentMinor || r.kind == task.KindPrevMinor {
			securitySummary = wf.Param(wd, securitySummaryParameter)
			securityFixes = wf.Param(wd, securityFixesParameter)
		}
		addCommTasks(wd, build, comm, r.kind, wf.Slice(published), securitySummary, securityFixes, coordinators)

		h.RegisterDefinition(fmt.Sprintf("Go 1.%d %s", r.major, r.suffix), wd)
	}

	wd, err := createMinorReleaseWorkflow(build, milestone, version, comm, currentMajor-1, currentMajor)
	if err != nil {
		return err
	}
	h.RegisterDefinition(fmt.Sprintf("Minor releases for Go 1.%d and 1.%d", currentMajor-1, currentMajor), wd)

	return nil
}

func registerBuildTestSignOnlyWorkflow(h *DefinitionHolder, version *task.VersionTasks, build *BuildReleaseTasks, major int, kind task.ReleaseKind) {
	wd := wf.New()

	nextVersion := wf.Task1(wd, "Get next version", version.GetNextVersion, wf.Const(kind))
	branch := fmt.Sprintf("release-branch.go1.%d", major)
	if kind == task.KindBeta {
		branch = "master"
	}
	branchVal := wf.Const(branch)
	distpackVal := wf.Const(enableDistpack(major))
	timestamp := wf.Task0(wd, "Timestamp release", now)
	versionFile := wf.Task3(wd, "Generate VERSION file", version.GenerateVersionFile, distpackVal, nextVersion, timestamp)
	wf.Output(wd, "VERSION file", versionFile)
	source := wf.Task4(wd, "Build source archive", build.buildSource, distpackVal, branchVal, wf.Const(""), versionFile)
	artifacts, mods := build.addBuildTasks(wd, major, nextVersion, timestamp, source)
	wf.Output(wd, "Artifacts", artifacts)
	wf.Output(wd, "Modules", mods)

	h.RegisterDefinition(fmt.Sprintf("dry-run (build, test, and sign only): Go 1.%d next beta", major), wd)
}

func createMinorReleaseWorkflow(build *BuildReleaseTasks, milestone *task.MilestoneTasks, version *task.VersionTasks, comm task.CommunicationTasks, prevMajor, currentMajor int) (*wf.Definition, error) {
	wd := wf.New()

	coordinators := wf.Param(wd, releaseCoordinators)
	currPublished := addSingleReleaseWorkflow(build, milestone, version, wd.Sub(fmt.Sprintf("Go 1.%d", currentMajor)), currentMajor, task.KindCurrentMinor, coordinators)
	prevPublished := addSingleReleaseWorkflow(build, milestone, version, wd.Sub(fmt.Sprintf("Go 1.%d", prevMajor)), prevMajor, task.KindPrevMinor, coordinators)

	securitySummary := wf.Param(wd, securitySummaryParameter)
	securityFixes := wf.Param(wd, securityFixesParameter)
	addCommTasks(wd, build, comm, task.KindCurrentMinor, wf.Slice(currPublished, prevPublished), securitySummary, securityFixes, coordinators)

	return wd, nil
}

func addCommTasks(
	wd *wf.Definition, build *BuildReleaseTasks, comm task.CommunicationTasks,
	kind task.ReleaseKind, published wf.Value[[]task.Published], securitySummary wf.Value[string], securityFixes, coordinators wf.Value[[]string],
) {
	okayToAnnounceAndTweet := wf.Action0(wd, "Wait to Announce", build.ApproveAction, wf.After(published))

	// Announce that a new Go release has been published.
	sentMail := wf.Task4(wd, "mail-announcement", comm.AnnounceRelease, wf.Const(kind), published, securityFixes, coordinators, wf.After(okayToAnnounceAndTweet))
	announcementURL := wf.Task1(wd, "await-announcement", comm.AwaitAnnounceMail, sentMail)
	tweetURL := wf.Task4(wd, "post-tweet", comm.TweetRelease, wf.Const(kind), published, securitySummary, announcementURL, wf.After(okayToAnnounceAndTweet))

	wf.Output(wd, "Announcement URL", announcementURL)
	wf.Output(wd, "Tweet URL", tweetURL)
}

func enableDistpack(major int) bool {
	return major > 20
}

func now(_ context.Context) (time.Time, error) {
	return time.Now().UTC().Round(time.Second), nil
}

func addSingleReleaseWorkflow(
	build *BuildReleaseTasks, milestone *task.MilestoneTasks, version *task.VersionTasks,
	wd *wf.Definition, major int, kind task.ReleaseKind, coordinators wf.Value[[]string],
) wf.Value[task.Published] {
	kindVal := wf.Const(kind)
	branch := fmt.Sprintf("release-branch.go1.%d", major)
	if kind == task.KindBeta {
		branch = "master"
	}
	branchVal := wf.Const(branch)
	distpackVal := wf.Const(enableDistpack(major))
	startingHead := wf.Task1(wd, "Read starting branch head", version.ReadBranchHead, branchVal)

	// Select version, check milestones.
	nextVersion := wf.Task1(wd, "Get next version", version.GetNextVersion, kindVal)
	timestamp := wf.Task0(wd, "Timestamp release", now)
	versionFile := wf.Task3(wd, "Generate VERSION file", version.GenerateVersionFile, distpackVal, nextVersion, timestamp)
	wf.Output(wd, "VERSION file", versionFile)
	milestones := wf.Task2(wd, "Pick milestones", milestone.FetchMilestones, nextVersion, kindVal)
	checked := wf.Action3(wd, "Check blocking issues", milestone.CheckBlockers, milestones, nextVersion, kindVal)

	securityRef := wf.Param(wd, wf.ParamDef[string]{Name: "Ref from the private repository to build from (optional)"})
	source := wf.Task4(wd, "Build source archive", build.buildSource, distpackVal, startingHead, securityRef, versionFile, wf.After(checked))

	// Build, test, and sign release.
	signedAndTestedArtifacts, modules := build.addBuildTasks(wd, major, nextVersion, timestamp, source)
	okayToTagAndPublish := wf.Action0(wd, "Wait for Release Coordinator Approval", build.ApproveAction, wf.After(signedAndTestedArtifacts))

	dlcl := wf.Task5(wd, "Mail DL CL", version.MailDLCL, wf.Const(major), kindVal, nextVersion, coordinators, wf.Const(false), wf.After(okayToTagAndPublish))
	dlclCommit := wf.Task2(wd, "Wait for DL CL submission", version.AwaitCL, dlcl, wf.Const(""))
	wf.Output(wd, "Download CL submitted", dlclCommit)

	// Tag version and upload to CDN/website.
	// If we're releasing a beta from master, tagging is easy; we just tag the
	// commit we started from. Otherwise, we're going to submit a VERSION CL,
	// and we need to make sure that that CL is submitted on top of the same
	// state we built from. For security releases that state may not have
	// been public when we started, but it should be now.
	tagCommit := startingHead
	if branch != "master" {
		publishingHead := wf.Task4(wd, "Check branch state matches source archive", build.checkSourceMatch, distpackVal, branchVal, versionFile, source, wf.After(okayToTagAndPublish))
		versionCL := wf.Task4(wd, "Mail version CL", version.CreateAutoSubmitVersionCL, branchVal, nextVersion, coordinators, versionFile, wf.After(publishingHead))
		tagCommit = wf.Task2(wd, "Wait for version CL submission", version.AwaitCL, versionCL, publishingHead)
	}
	tagged := wf.Action2(wd, "Tag version", version.TagRelease, nextVersion, tagCommit, wf.After(okayToTagAndPublish))
	uploaded := wf.Action1(wd, "Upload artifacts to CDN", build.uploadArtifacts, signedAndTestedArtifacts, wf.After(tagged))
	uploadedMods := wf.Action2(wd, "Upload modules to CDN", build.uploadModules, nextVersion, modules, wf.After(tagged))
	availableOnProxy := wf.Action2(wd, "Wait for modules on proxy.golang.org", build.awaitProxy, nextVersion, modules, wf.After(uploadedMods))
	pushed := wf.Action3(wd, "Push issues", milestone.PushIssues, milestones, nextVersion, kindVal, wf.After(tagged))
	published := wf.Task2(wd, "Publish to website", build.publishArtifacts, nextVersion, signedAndTestedArtifacts, wf.After(uploaded, availableOnProxy, pushed))
	if kind == task.KindMajor {
		goimportsCL := wf.Task2(wd, fmt.Sprintf("Mail goimports CL for 1.%d", major), version.CreateUpdateStdlibIndexCL, coordinators, nextVersion, wf.After(published))
		goimportsCommit := wf.Task2(wd, "Wait for goimports CL submission", version.AwaitCL, goimportsCL, wf.Const(""))
		wf.Output(wd, "goimports CL submitted", goimportsCommit)
	}

	dockerBuild := wf.Task1(wd, "Start Google Docker build", build.runGoogleDockerBuild, nextVersion, wf.After(uploaded))
	dockerResult := wf.Task1(wd, "Await Google Docker build", build.awaitCloudBuild, dockerBuild)
	wf.Output(wd, "Google Docker image status", dockerResult)

	wf.Output(wd, "Published to website", published)
	return published
}

type moduleArtifact struct {
	// The target for this module.
	Target *releasetargets.Target
	// The contents of the mod and info files.
	Mod, Info string
	// The scratch path of the zip within the scratch directory.
	ZipScratch string // scratch path
}

// addBuildTasks registers tasks to build, test, and sign the release onto wd.
// It returns the output from the last task, a slice of signed and tested artifacts.
func (tasks *BuildReleaseTasks) addBuildTasks(wd *wf.Definition, major int, version wf.Value[string], timestamp wf.Value[time.Time], source wf.Value[artifact]) (wf.Value[[]artifact], wf.Value[[]moduleArtifact]) {
	targets := releasetargets.TargetsForGo1Point(major)
	skipTests := wf.Param(wd, wf.ParamDef[[]string]{Name: "Targets to skip testing (or 'all') (optional)", ParamType: wf.SliceShort})

	artifacts := []wf.Value[artifact]{source}
	var mods []wf.Value[moduleArtifact]
	var blockers []wf.Dependency

	// Build, test and sign binary artifacts for all targets.
	for _, target := range targets {
		wd := wd.Sub(target.Name)

		// Build release artifacts for the platform. For 1.21+, use distpacks.
		// For windows, produce both a tgz and zip -- we need tgzs to run
		// tests, even though we'll eventually publish the zips.
		var tar, zip wf.Value[artifact]
		var mod wf.Value[moduleArtifact]
		if enableDistpack(major) {
			distpack := wf.Task3(wd, "Build distpack", tasks.buildDistpack, wf.Const("linux-amd64"), wf.Const(target), source)
			reproducer := wf.Task3(wd, "Reproduce distpack on Windows", tasks.buildDistpack, wf.Const("windows-amd64-2016"), wf.Const(target), source)
			match := wf.Action2(wd, "Check distpacks match", tasks.checkDistpacksMatch, distpack, reproducer)
			blockers = append(blockers, match)
			if target.GOOS == "windows" {
				zip = wf.Task1(wd, "Get binary from distpack", tasks.binaryArchiveFromDistpack, distpack)
				tar = wf.Task1(wd, "Convert zip to .tgz", tasks.convertZipToTGZ, zip)
			} else {
				tar = wf.Task1(wd, "Get binary from distpack", tasks.binaryArchiveFromDistpack, distpack)
			}
			mod = wf.Task1(wd, "Get module files from distpack", tasks.modFilesFromDistpack, distpack)
		} else {
			tar = wf.Task2(wd, "Build binary archive", tasks.buildBinary, wf.Const(target), source)
			if target.GOOS == "windows" {
				zip = wf.Task1(wd, "Convert to .zip", tasks.convertTGZToZip, tar)
			}
			mod = wf.Task3(wd, "Convert binary archive to modules", tasks.modFilesFromBinary, version, timestamp, tar)
		}

		// Create installers and perform platform-specific signing where
		// applicable. For macOS, produce updated tgz and module zips that
		// include the signed binaries.
		switch target.GOOS {
		case "darwin":
			pkg := wf.Task2(wd, "Build PKG installer", tasks.buildDarwinPKG, version, tar)
			signedPKG := wf.Task2(wd, "Sign PKG installer", tasks.signArtifact, pkg, wf.Const(sign.BuildMacOS))
			signedTGZ := wf.Task1(wd, "Convert PKG to .tgz", tasks.convertPKGToTGZ, signedPKG)
			mergedTGZ := wf.Task2(wd, "Merge signed files into .tgz", tasks.mergeSignedToTGZ, tar, signedTGZ)
			mod = wf.Task4(wd, "Merge signed files into module zip", tasks.mergeSignedToModule, version, timestamp, mod, signedTGZ)
			artifacts = append(artifacts, signedPKG, mergedTGZ)
		case "windows":
			msi := wf.Task1(wd, "Build MSI installer", tasks.buildWindowsMSI, tar)
			signedMSI := wf.Task2(wd, "Sign MSI installer", tasks.signArtifact, msi, wf.Const(sign.BuildWindows))
			artifacts = append(artifacts, signedMSI, zip)
		default:
			artifacts = append(artifacts, tar)
		}
		mods = append(mods, mod)
		if target.BuildOnly {
			continue
		}
		short := wf.Action3(wd, "Run short tests", tasks.runTests, wf.Const(dashboard.Builders[target.Builder]), skipTests, tar)
		blockers = append(blockers, short)
		if target.LongTestBuilder != "" {
			long := wf.Action3(wd, "Run long tests", tasks.runTests, wf.Const(dashboard.Builders[target.LongTestBuilder]), skipTests, tar)
			blockers = append(blockers, long)
		}
	}
	signedArtifacts := wf.Task1(wd, "Compute GPG signature for artifacts", tasks.computeGPG, wf.Slice(artifacts...))

	// Run advisory trybots.
	var advisoryResults []wf.Value[tryBotResult]
	for _, bc := range advisoryTryBots(major) {
		result := wf.Task3(wd, "Run advisory TryBot "+bc.Name, tasks.runAdvisoryTryBot, wf.Const(bc), skipTests, source)
		advisoryResults = append(advisoryResults, result)
	}
	tryBotsApproved := wf.Action1(wd, "Wait for advisory TryBots", tasks.checkAdvisoryTrybots, wf.Slice(advisoryResults...))
	blockers = append(blockers, tryBotsApproved)

	signedAndTested := wf.Task2(wd, "Wait for signing and tests", func(ctx *wf.TaskContext, artifacts []artifact, version string) ([]artifact, error) {
		// Note: Note this needs to happen somewhere, doesn't matter where. Maybe move it to a nicer place later.
		for i, a := range artifacts {
			if a.Target != nil {
				artifacts[i].Filename = version + "." + a.Target.Name + "." + a.Suffix
			} else {
				artifacts[i].Filename = version + "." + a.Suffix
			}
		}

		return artifacts, nil
	}, signedArtifacts, version, wf.After(blockers...), wf.After(wf.Slice(mods...)))
	return signedAndTested, wf.Slice(mods...)
}

func advisoryTryBots(major int) []*dashboard.BuildConfig {
	usedBuilders := map[string]bool{}
	for _, t := range releasetargets.TargetsForGo1Point(major) {
		usedBuilders[t.Builder] = true
		usedBuilders[t.LongTestBuilder] = true
	}

	var extras []*dashboard.BuildConfig
	for name, bc := range dashboard.Builders {
		if !usedBuilders[name] &&
			bc.BuildsRepoPostSubmit("go", fmt.Sprintf("release-branch.go1.%d", major), "") &&
			bc.HostConfig().IsGoogle() &&
			len(bc.KnownIssues) == 0 {
			extras = append(extras, bc)
		}
	}
	return extras
}

// BuildReleaseTasks serves as an adapter to the various build tasks in the task package.
type BuildReleaseTasks struct {
	GerritClient             task.GerritClient
	GerritHTTPClient         *http.Client
	GerritURL                string
	PrivateGerritURL         string
	GCSClient                *storage.Client
	ScratchURL, ServingURL   string // ScratchURL is a gs:// or file:// URL, no trailing slash. E.g., "gs://golang-release-staging/relui-scratch".
	DownloadURL              string
	ProxyPrefix              string // ProxyPrefix is the prefix at which module files are published, e.g. https://proxy.golang.org/golang.org/toolchain/@v
	PublishFile              func(task.WebsiteFile) error
	CreateBuildlet           func(context.Context, string) (buildlet.RemoteClient, error)
	SignService              sign.Service
	GoogleDockerBuildProject string
	GoogleDockerBuildTrigger string
	CloudBuildClient         task.CloudBuildClient
	ApproveAction            func(*wf.TaskContext) error
}

func (b *BuildReleaseTasks) buildSource(ctx *wf.TaskContext, distpack bool, revision, securityRevision, versionFile string) (artifact, error) {
	url := b.GerritURL
	rev := revision
	if securityRevision != "" {
		url = b.PrivateGerritURL
		rev = securityRevision
	}
	if distpack {
		return b.runBuildStep(ctx, nil, dashboard.Builders["linux-amd64"], artifact{}, "src.tar.gz", func(bs *task.BuildletStep, _ io.Reader, w io.Writer) error {
			return bs.BuildSourceDistpack(ctx, b.GerritHTTPClient, url, rev, versionFile, w)
		})
	}
	return b.runBuildStep(ctx, nil, nil, artifact{}, "src.tar.gz", func(_ *task.BuildletStep, _ io.Reader, w io.Writer) error {
		return task.WriteSourceArchive(ctx, b.GerritHTTPClient, url, rev, versionFile, w)
	})
}

func (b *BuildReleaseTasks) checkSourceMatch(ctx *wf.TaskContext, distpack bool, branch, versionFile string, source artifact) (head string, _ error) {
	head, err := b.GerritClient.ReadBranchHead(ctx, "go", branch)
	if err != nil {
		return "", err
	}
	branchArchive, err := b.buildSource(ctx, distpack, head, "", versionFile)
	if err != nil {
		return "", err
	}
	diff, err := b.diffArtifacts(ctx, branchArchive, source)
	if err != nil {
		return "", err
	}
	if diff != "" {
		return "", fmt.Errorf("branch state doesn't match source archive (-branch, +archive):\n%v", diff)
	}
	return head, nil
}

func (b *BuildReleaseTasks) diffArtifacts(ctx *wf.TaskContext, a1, a2 artifact) (string, error) {
	h1, err := b.hashArtifact(ctx, a1)
	if err != nil {
		return "", fmt.Errorf("hashing first tarball: %v", err)
	}
	h2, err := b.hashArtifact(ctx, a2)
	if err != nil {
		return "", fmt.Errorf("hashing second tarball: %v", err)
	}
	return cmp.Diff(h1, h2), nil
}

func (b *BuildReleaseTasks) hashArtifact(ctx *wf.TaskContext, a artifact) (map[string]string, error) {
	var hashes map[string]string
	_, err := b.runBuildStep(ctx, nil, nil, a, "", func(_ *task.BuildletStep, r io.Reader, _ io.Writer) error {
		var err error
		hashes, err = tarballHashes(r)
		return err
	})
	return hashes, err
}

func tarballHashes(r io.Reader) (map[string]string, error) {
	gzr, err := gzip.NewReader(r)
	if err != nil {
		return nil, err
	}
	defer gzr.Close()
	tr := tar.NewReader(gzr)
	hashes := map[string]string{}
	for {
		header, err := tr.Next()
		if err == io.EOF {
			break
		} else if err != nil {
			return nil, fmt.Errorf("reading tar header: %v", err)
		}
		h := sha256.New()
		if _, err := io.CopyN(h, tr, header.Size); err != nil {
			return nil, fmt.Errorf("reading file %q: %v", header.Name, err)
		}
		hashes[header.Name] = fmt.Sprintf("%X", h.Sum(nil))
	}
	return hashes, nil
}

func (b *BuildReleaseTasks) buildDistpack(ctx *wf.TaskContext, builder string, target *releasetargets.Target, source artifact) (artifact, error) {
	bc := dashboard.Builders[builder]
	return b.runBuildStep(ctx, target, bc, source, "tar.gz", func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
		return bs.BuildDistpack(ctx, r, w)
	})
}

func (b *BuildReleaseTasks) checkDistpacksMatch(ctx *wf.TaskContext, linux, windows artifact) error {
	diff, err := b.diffArtifacts(ctx, linux, windows)
	if err != nil {
		return err
	}
	if diff != "" {
		return fmt.Errorf("distpacks don't match (-linux, +windows): %v", diff)
	}
	return nil
}

func (b *BuildReleaseTasks) binaryArchiveFromDistpack(ctx *wf.TaskContext, distpack artifact) (artifact, error) {
	// This must not match the module files, which currently start with v0.0.1.
	glob := fmt.Sprintf("go*%v-%v.*", distpack.Target.GOOS, distpack.Target.GOARCH)
	suffix := "tar.gz"
	if distpack.Target.GOOS == "windows" {
		suffix = "zip"
	}
	return b.runBuildStep(ctx, distpack.Target, nil, distpack, suffix, func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
		return task.ExtractFile(r, w, glob)
	})
}

func (b *BuildReleaseTasks) modFilesFromDistpack(ctx *wf.TaskContext, distpack artifact) (moduleArtifact, error) {
	result := moduleArtifact{Target: distpack.Target}
	artifact, err := b.runBuildStep(ctx, nil, nil, distpack, "mod.zip", func(_ *task.BuildletStep, r io.Reader, w io.Writer) error {
		zr, err := gzip.NewReader(r)
		if err != nil {
			return err
		}
		tr := tar.NewReader(zr)
		foundZip := false
		for {
			h, err := tr.Next()
			if err == io.EOF {
				return io.ErrUnexpectedEOF
			} else if err != nil {
				return err
			}
			if h.FileInfo().IsDir() || !strings.HasPrefix(h.Name, "v0.0.1") {
				continue
			}

			switch {
			case strings.HasSuffix(h.Name, ".zip"):
				if _, err := io.Copy(w, tr); err != nil {
					return err
				}
				foundZip = true
			case strings.HasSuffix(h.Name, ".info"):
				buf := &bytes.Buffer{}
				if _, err := io.Copy(buf, tr); err != nil {
					return err
				}
				result.Info = buf.String()
			case strings.HasSuffix(h.Name, ".mod"):
				buf := &bytes.Buffer{}
				if _, err := io.Copy(buf, tr); err != nil {
					return err
				}
				result.Mod = buf.String()
			}

			if foundZip && result.Mod != "" && result.Info != "" {
				return nil
			}
		}
	})
	if err != nil {
		return moduleArtifact{}, err
	}
	result.ZipScratch = artifact.ScratchPath
	return result, nil
}

func (b *BuildReleaseTasks) modFilesFromBinary(ctx *wf.TaskContext, version string, t time.Time, tar artifact) (moduleArtifact, error) {
	result := moduleArtifact{Target: tar.Target}
	a, err := b.runBuildStep(ctx, nil, nil, tar, "mod.zip", func(_ *task.BuildletStep, r io.Reader, w io.Writer) error {
		ctx.DisableWatchdog() // The zipping process can be time consuming and is unlikely to hang.
		var err error
		result.Mod, result.Info, err = task.TarToModFiles(tar.Target, version, t, r, w)
		return err
	})
	if err != nil {
		return moduleArtifact{}, err
	}
	result.ZipScratch = a.ScratchPath
	return result, nil
}

func (b *BuildReleaseTasks) mergeSignedToTGZ(ctx *wf.TaskContext, unsigned, signed artifact) (artifact, error) {
	return b.runBuildStep(ctx, unsigned.Target, nil, signed, "tar.gz", func(_ *task.BuildletStep, signed io.Reader, w io.Writer) error {
		signedBinaries, err := loadBinaries(ctx, signed)

		// Copy files from the tgz, overwriting with binaries from the signed tar.
		scratchFS, err := gcsfs.FromURL(ctx, b.GCSClient, b.ScratchURL)
		if err != nil {
			return err
		}
		ur, err := scratchFS.Open(unsigned.ScratchPath)
		if err != nil {
			return err
		}
		defer ur.Close()
		uzr, err := gzip.NewReader(ur)
		if err != nil {
			return err
		}
		defer uzr.Close()

		utr := tar.NewReader(uzr)

		zw, err := gzip.NewWriterLevel(w, gzip.BestCompression)
		if err != nil {
			return err
		}
		tw := tar.NewWriter(zw)

		for {
			th, err := utr.Next()
			if err == io.EOF {
				break
			} else if err != nil {
				return err
			}

			hdr := *th
			src := io.NopCloser(utr)
			if signed, ok := signedBinaries[th.Name]; ok {
				src = io.NopCloser(bytes.NewReader(signed))
				hdr.Size = int64(len(signed))
			}

			if err := tw.WriteHeader(&hdr); err != nil {
				return err
			}
			if _, err := io.Copy(tw, src); err != nil {
				return err
			}
		}

		if err := tw.Close(); err != nil {
			return err
		}
		return zw.Close()
	})
}

func (b *BuildReleaseTasks) mergeSignedToModule(ctx *wf.TaskContext, version string, timestamp time.Time, mod moduleArtifact, signed artifact) (moduleArtifact, error) {
	a, err := b.runBuildStep(ctx, nil, nil, signed, "signedmod.zip", func(_ *task.BuildletStep, signed io.Reader, w io.Writer) error {
		signedBinaries, err := loadBinaries(ctx, signed)

		// Copy files from the module zip, overwriting with binaries from the signed tar.
		scratchFS, err := gcsfs.FromURL(ctx, b.GCSClient, b.ScratchURL)
		if err != nil {
			return err
		}
		mr, err := scratchFS.Open(mod.ZipScratch)
		if err != nil {
			return err
		}
		defer mr.Close()
		mbytes, err := io.ReadAll(mr)
		if err != nil {
			return err
		}
		mzr, err := zip.NewReader(bytes.NewReader(mbytes), int64(len(mbytes)))
		if err != nil {
			return err
		}

		prefix := task.ToolchainZipPrefix(mod.Target, version) + "/"
		mzw := zip.NewWriter(w)
		mzw.RegisterCompressor(zip.Deflate, func(out io.Writer) (io.WriteCloser, error) {
			return flate.NewWriter(out, flate.BestCompression)
		})
		for _, f := range mzr.File {
			var in io.ReadCloser
			suffix, ok := cutPrefix(f.Name, prefix)
			if !ok {
				continue
			}
			if contents, ok := signedBinaries["go/"+suffix]; ok {
				in = io.NopCloser(bytes.NewReader(contents))
			} else {
				in, err = f.Open()
				if err != nil {
					return err
				}
			}

			hdr := f.FileHeader
			out, err := mzw.CreateHeader(&hdr)
			if err != nil {
				return err
			}
			if _, err := io.Copy(out, in); err != nil {
				return err
			}
		}
		return mzw.Close()
	})
	if err != nil {
		return moduleArtifact{}, err
	}
	mod.ZipScratch = a.ScratchPath
	return mod, nil
}

// loadBinaries reads binaries that we expect to have been signed by the
// macOS signing process from tgz.
func loadBinaries(ctx *wf.TaskContext, tgz io.Reader) (map[string][]byte, error) {
	zr, err := gzip.NewReader(tgz)
	if err != nil {
		return nil, err
	}
	defer zr.Close()
	tr := tar.NewReader(zr)

	binaries := map[string][]byte{}
	for {
		th, err := tr.Next()
		if err == io.EOF {
			break
		} else if err != nil {
			return nil, err
		}
		if !strings.HasPrefix(th.Name, "go/bin/") && !strings.HasPrefix(th.Name, "go/pkg/tool/") {
			continue
		}
		if th.Typeflag != tar.TypeReg || th.Mode&0100 == 0 {
			continue
		}
		contents, err := io.ReadAll(tr)
		if err != nil {
			return nil, err
		}
		binaries[th.Name] = contents
	}
	return binaries, nil
}

func (b *BuildReleaseTasks) buildBinary(ctx *wf.TaskContext, target *releasetargets.Target, source artifact) (artifact, error) {
	bc := dashboard.Builders[target.Builder]
	return b.runBuildStep(ctx, target, bc, source, "tar.gz", func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
		return bs.BuildBinary(ctx, r, w)
	})
}

func (b *BuildReleaseTasks) buildDarwinPKG(ctx *wf.TaskContext, version string, binary artifact) (artifact, error) {
	bc := dashboard.Builders[binary.Target.Builder]
	return b.runBuildStep(ctx, binary.Target, bc, binary, "pkg", func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
		return bs.BuildDarwinPKG(ctx, r, version, w)
	})
}
func (b *BuildReleaseTasks) convertPKGToTGZ(ctx *wf.TaskContext, pkg artifact) (tgz artifact, _ error) {
	bc := dashboard.Builders[pkg.Target.Builder]
	return b.runBuildStep(ctx, pkg.Target, bc, pkg, "tar.gz", func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
		return bs.ConvertPKGToTGZ(ctx, r, w)
	})
}

func (b *BuildReleaseTasks) buildWindowsMSI(ctx *wf.TaskContext, binary artifact) (artifact, error) {
	bc := dashboard.Builders[binary.Target.Builder]
	return b.runBuildStep(ctx, binary.Target, bc, binary, "msi", func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
		return bs.BuildWindowsMSI(ctx, r, w)
	})
}

func (b *BuildReleaseTasks) convertTGZToZip(ctx *wf.TaskContext, binary artifact) (artifact, error) {
	return b.runBuildStep(ctx, binary.Target, nil, binary, "zip", func(_ *task.BuildletStep, r io.Reader, w io.Writer) error {
		return task.ConvertTGZToZIP(r, w)
	})
}

func (b *BuildReleaseTasks) convertZipToTGZ(ctx *wf.TaskContext, binary artifact) (artifact, error) {
	return b.runBuildStep(ctx, binary.Target, nil, binary, "tar.gz", func(_ *task.BuildletStep, r io.Reader, w io.Writer) error {
		// Reading the whole file isn't ideal, but we need a ReaderAt, and
		// don't have access to the lower-level file (which would support
		// seeking) here.
		content, err := io.ReadAll(r)
		if err != nil {
			return err
		}
		return task.ConvertZIPToTGZ(bytes.NewReader(content), int64(len(content)), w)
	})
}

// computeGPG performs GPG signing on artifacts, and sets their GPGSignature field.
func (b *BuildReleaseTasks) computeGPG(ctx *wf.TaskContext, artifacts []artifact) ([]artifact, error) {
	// doGPG reports whether to do GPG signature computation for artifact a.
	doGPG := func(a artifact) bool {
		return a.Suffix == "src.tar.gz" || a.Suffix == "tar.gz"
	}

	// Start a signing job on all artifacts that want to do GPG signing and await its results.
	var in []string
	for _, a := range artifacts {
		if !doGPG(a) {
			continue
		}

		in = append(in, b.ScratchURL+"/"+a.ScratchPath)
	}
	out, err := b.signArtifacts(ctx, sign.BuildGPG, in)
	if err != nil {
		return nil, err
	} else if len(out) != len(in) {
		return nil, fmt.Errorf("got %d outputs, want %d .asc signatures", len(out), len(in))
	}
	// All done, we have our GPG signatures.
	// Put them in a base name → scratch path map.
	var signatures = make(map[string]string)
	for _, o := range out {
		scratchPath, ok := cutPrefix(o, b.ScratchURL+"/")
		if !ok {
			return nil, fmt.Errorf("got signed URL %q outside of scratch space %q, which is unsupported", o, b.ScratchURL+"/")
		}
		signatures[path.Base(o)] = scratchPath
	}

	// Set the artifacts' GPGSignature field.
	scratchFS, err := gcsfs.FromURL(ctx, b.GCSClient, b.ScratchURL)
	if err != nil {
		return nil, err
	}
	for i, a := range artifacts {
		if !doGPG(a) {
			continue
		}

		sigPath, ok := signatures[path.Base(a.ScratchPath)+".asc"]
		if !ok {
			return nil, fmt.Errorf("no GPG signature for %q", path.Base(a.ScratchPath))
		}
		sig, err := fs.ReadFile(scratchFS, sigPath)
		if err != nil {
			return nil, err
		}
		artifacts[i].GPGSignature = string(sig)
	}

	return artifacts, nil
}

// signArtifact signs a single artifact of specified type.
func (b *BuildReleaseTasks) signArtifact(ctx *wf.TaskContext, a artifact, bt sign.BuildType) (signed artifact, _ error) {
	// Sign the unsigned artifact located at ScratchPath, and
	// update ScratchPath to point to the new signed artifact.
	signedURL, err := b.signArtifacts(ctx, bt, []string{b.ScratchURL + "/" + a.ScratchPath})
	if err != nil {
		return artifact{}, err
	} else if len(signedURL) != 1 {
		return artifact{}, fmt.Errorf("got %d outputs, want 1 signed artifact", len(signedURL))
	}
	var ok bool
	a.ScratchPath, ok = cutPrefix(signedURL[0], b.ScratchURL+"/")
	if !ok {
		return artifact{}, fmt.Errorf("got signed URL %q outside of scratch space %q, which is unsupported", signedURL[0], b.ScratchURL+"/")
	}
	scratchFS, err := gcsfs.FromURL(ctx, b.GCSClient, b.ScratchURL)
	if err != nil {
		return artifact{}, err
	}

	// Update the Size and SHA256 fields.
	f, err := scratchFS.Open(a.ScratchPath)
	if err != nil {
		return artifact{}, err
	}
	var hash = sha256.New()
	n, err := io.Copy(hash, f)
	if err != nil {
		f.Close()
		return artifact{}, err
	}
	err = f.Close()
	if err != nil {
		return artifact{}, err
	}
	a.Size = int(n)
	a.SHA256 = fmt.Sprintf("%x", string(hash.Sum([]byte(nil))))

	return a, nil
}

// signArtifacts starts signing on the artifacts provided via the gs:// URL inputs,
// waits for signing to complete, and returns the gs:// URLs of the signed outputs.
func (b *BuildReleaseTasks) signArtifacts(ctx *wf.TaskContext, bt sign.BuildType, inURLs []string) (outURLs []string, _ error) {
	jobID, err := b.SignService.SignArtifact(ctx, bt, inURLs)
	if err != nil {
		return nil, err
	}
	outURLs, jobError := task.AwaitCondition(ctx, time.Minute, func() (out []string, done bool, _ error) {
		statusContext, cancel := context.WithTimeout(ctx, time.Minute)
		defer cancel()
		t := time.Now()
		status, desc, out, err := b.SignService.ArtifactSigningStatus(statusContext, jobID)
		if err != nil {
			ctx.Printf("ArtifactSigningStatus ran into a retryable communication error after %v: %v\n", time.Since(t), err)
			return nil, false, nil
		}
		switch status {
		case sign.StatusCompleted:
			return out, true, nil // All done.
		case sign.StatusFailed:
			if desc != "" {
				return nil, true, fmt.Errorf("signing attempt failed: %s", desc)
			}
			return nil, true, fmt.Errorf("signing attempt failed")
		default:
			if desc != "" {
				ctx.Printf("still waiting: %s\n", desc)
			}
			return nil, false, nil // Still waiting.
		}
	})
	if jobError != nil {
		// If ctx is canceled, also cancel the signing request.
		if ctx.Err() != nil {
			cancelContext, cancel := context.WithTimeout(context.Background(), time.Minute)
			defer cancel()
			t := time.Now()
			err := b.SignService.CancelSigning(cancelContext, jobID)
			if err != nil {
				ctx.Printf("CancelSigning error after %v: %v\n", time.Since(t), err)
			}
		}

		return nil, jobError
	}
	return outURLs, nil
}

func (b *BuildReleaseTasks) runTests(ctx *wf.TaskContext, build *dashboard.BuildConfig, skipTests []string, binary artifact) error {
	for _, skip := range skipTests {
		if skip == "all" || binary.Target.Name == skip {
			ctx.Printf("Skipping test")
			return nil
		}
	}
	_, err := b.runBuildStep(ctx, binary.Target, build, binary, "", func(bs *task.BuildletStep, r io.Reader, _ io.Writer) error {
		return bs.TestTarget(ctx, r)
	})
	return err
}

type tryBotResult struct {
	Name   string
	Passed bool
}

func (b *BuildReleaseTasks) runAdvisoryTryBot(ctx *wf.TaskContext, bc *dashboard.BuildConfig, skipTests []string, source artifact) (tryBotResult, error) {
	for _, skip := range skipTests {
		if skip == "all" || bc.Name == skip {
			ctx.Printf("Skipping test")
			return tryBotResult{bc.Name, true}, nil
		}
	}
	passed := false
	for attempt := 1; attempt <= workflow.MaxRetries && !passed; attempt++ {
		ctx.Printf("======== Trybot Attempt %d of %d ========\n", attempt, workflow.MaxRetries)
		_, err := b.runBuildStep(ctx, nil, bc, source, "", func(bs *task.BuildletStep, r io.Reader, w io.Writer) error {
			var err error
			passed, err = bs.RunTryBot(ctx, r)
			return err
		})
		if err != nil {
			ctx.Printf("Trybot Attempt failed: %v\n", err)
		}
	}
	if errors.Is(ctx.Context.Err(), context.Canceled) {
		ctx.Printf("Advisory TryBot timed out or was canceled\n")
		return tryBotResult{bc.Name, passed}, nil
	}
	if !passed {
		ctx.Printf("Advisory TryBot failed. Check the logs and approve this task if it's okay:\n")
		return tryBotResult{bc.Name, passed}, b.ApproveAction(ctx)
	}
	return tryBotResult{bc.Name, passed}, nil
}

func (b *BuildReleaseTasks) checkAdvisoryTrybots(ctx *wf.TaskContext, results []tryBotResult) error {
	var fails []string
	for _, r := range results {
		if !r.Passed {
			fails = append(fails, r.Name)
		}
	}
	if len(fails) != 0 {
		sort.Strings(fails)
		ctx.Printf("Some advisory TryBots failed and their failures have been approved:\n%v", strings.Join(fails, "\n"))
		return nil
	}
	return nil
}

// runBuildStep is a convenience function that manages resources a build step might need.
// If a build config is specified, a BuildletStep will be passed to f. The target and build config
// need not match.
// If input with a scratch file is specified, its content will be opened and passed as a Reader to f.
// If outputSuffix is specified, a unique filename will be generated based off
// it (and the target name, if any), the file will be opened and passed as a
// Writer to f, and an artifact representing it will be returned as the result.
func (b *BuildReleaseTasks) runBuildStep(
	ctx *wf.TaskContext,
	target *releasetargets.Target,
	build *dashboard.BuildConfig,
	input artifact,
	outputSuffix string,
	f func(*task.BuildletStep, io.Reader, io.Writer) error,
) (artifact, error) {
	var step *task.BuildletStep
	if build != nil {
		ctx.Printf("Creating buildlet %v.", build.Name)
		client, err := b.CreateBuildlet(ctx, build.Name)
		if err != nil {
			return artifact{}, err
		}
		defer client.Close()
		w := &task.LogWriter{Logger: ctx}
		go w.Run(ctx)
		step = &task.BuildletStep{
			Target:      target,
			Buildlet:    client,
			BuildConfig: build,
			LogWriter:   w,
		}
		ctx.Printf("Buildlet ready.")
	}

	scratchFS, err := gcsfs.FromURL(ctx, b.GCSClient, b.ScratchURL)
	if err != nil {
		return artifact{}, err
	}
	var in io.ReadCloser
	if input.ScratchPath != "" {
		in, err = scratchFS.Open(input.ScratchPath)
		if err != nil {
			return artifact{}, err
		}
		defer in.Close()
	}
	var out io.WriteCloser
	var scratchPath string
	hash := sha256.New()
	size := &sizeWriter{}
	var multiOut io.Writer
	if outputSuffix != "" {
		scratchName := outputSuffix
		if target != nil {
			scratchName = target.Name + "." + outputSuffix
		}
		scratchPath = fmt.Sprintf("%v/%v-%v", ctx.WorkflowID.String(), rand.Int63(), scratchName)
		out, err = gcsfs.Create(scratchFS, scratchPath)
		if err != nil {
			return artifact{}, err
		}
		defer out.Close()
		multiOut = io.MultiWriter(out, hash, size)
	}
	// Hide in's Close method from the task, which may assert it to Closer.
	nopIn := io.NopCloser(in)
	if err := f(step, nopIn, multiOut); err != nil {
		return artifact{}, err
	}
	if step != nil {
		if err := step.Buildlet.Close(); err != nil {
			return artifact{}, err
		}
	}
	if in != nil {
		if err := in.Close(); err != nil {
			return artifact{}, err
		}
	}
	if out != nil {
		if err := out.Close(); err != nil {
			return artifact{}, err
		}
	}
	return artifact{
		Target:      target,
		ScratchPath: scratchPath,
		Suffix:      outputSuffix,
		SHA256:      fmt.Sprintf("%x", string(hash.Sum([]byte(nil)))),
		Size:        size.size,
	}, nil
}

// An artifact represents a file as it moves through the release process. Most
// files will appear on go.dev/dl eventually.
type artifact struct {
	// The target platform of this artifact, or nil for source.
	Target *releasetargets.Target
	// The scratch path of this artifact within the scratch directory.
	// <workflow-id>/<random-number>-<filename>
	ScratchPath string
	// The contents of the GPG signature for this artifact (.asc file).
	GPGSignature string
	// The filename suffix of the artifact, e.g. "tar.gz" or "src.tar.gz",
	// combined with the version and Target name to produce Filename.
	Suffix string
	// The final Filename of this artifact as it will be downloaded.
	Filename string
	SHA256   string
	Size     int
}

type sizeWriter struct {
	size int
}

func (w *sizeWriter) Write(p []byte) (n int, err error) {
	w.size += len(p)
	return len(p), nil
}

func (tasks *BuildReleaseTasks) uploadArtifacts(ctx *wf.TaskContext, artifacts []artifact) error {
	scratchFS, err := gcsfs.FromURL(ctx, tasks.GCSClient, tasks.ScratchURL)
	if err != nil {
		return err
	}
	servingFS, err := gcsfs.FromURL(ctx, tasks.GCSClient, tasks.ServingURL)
	if err != nil {
		return err
	}

	want := map[string]bool{} // URLs we're waiting on becoming available.
	for _, a := range artifacts {
		if err := uploadFile(scratchFS, servingFS, a.ScratchPath, a.Filename); err != nil {
			return err
		}
		want[tasks.DownloadURL+"/"+a.Filename] = true

		if err := gcsfs.WriteFile(servingFS, a.Filename+".sha256", []byte(a.SHA256)); err != nil {
			return err
		}
		want[tasks.DownloadURL+"/"+a.Filename+".sha256"] = true

		if a.GPGSignature != "" {
			if err := gcsfs.WriteFile(servingFS, a.Filename+".asc", []byte(a.GPGSignature)); err != nil {
				return err
			}
			want[tasks.DownloadURL+"/"+a.Filename+".asc"] = true
		}
	}
	_, err = task.AwaitCondition(ctx, 30*time.Second, checkFiles(ctx, want))
	return err
}

func (tasks *BuildReleaseTasks) uploadModules(ctx *wf.TaskContext, version string, modules []moduleArtifact) error {
	scratchFS, err := gcsfs.FromURL(ctx, tasks.GCSClient, tasks.ScratchURL)
	if err != nil {
		return err
	}
	servingFS, err := gcsfs.FromURL(ctx, tasks.GCSClient, tasks.ServingURL)
	if err != nil {
		return err
	}
	want := map[string]bool{} // URLs we're waiting on becoming available.
	for _, mod := range modules {
		base := task.ToolchainModuleVersion(mod.Target, version)
		if err := uploadFile(scratchFS, servingFS, mod.ZipScratch, fmt.Sprintf(base+".zip")); err != nil {
			return err
		}
		if err := gcsfs.WriteFile(servingFS, base+".info", []byte(mod.Info)); err != nil {
			return err
		}
		if err := gcsfs.WriteFile(servingFS, base+".mod", []byte(mod.Mod)); err != nil {
			return err
		}
		for _, ext := range []string{".zip", ".info", ".mod"} {
			want[tasks.DownloadURL+"/"+base+ext] = true
		}
	}
	_, err = task.AwaitCondition(ctx, 30*time.Second, checkFiles(ctx, want))
	return err
}

func (tasks *BuildReleaseTasks) awaitProxy(ctx *wf.TaskContext, version string, modules []moduleArtifact) error {
	want := map[string]bool{}
	for _, mod := range modules {
		url := fmt.Sprintf("%v/%v.info", tasks.ProxyPrefix, task.ToolchainModuleVersion(mod.Target, version))
		want[url] = true
	}
	_, err := task.AwaitCondition(ctx, 30*time.Second, checkFiles(ctx, want))
	return err
}

func checkFiles(ctx context.Context, want map[string]bool) func() (int, bool, error) {
	found := map[string]bool{}
	return func() (int, bool, error) {
		for url := range want {
			ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
			defer cancel()
			resp, err := ctxhttp.Head(ctx, http.DefaultClient, url)
			if err == context.DeadlineExceeded {
				cancel()
				continue
			}
			if err != nil {
				return 0, false, err
			}
			resp.Body.Close()
			cancel()
			if resp.StatusCode == http.StatusOK {
				found[url] = true
			}
		}
		return 0, len(want) == len(found), nil
	}
}

// uploadFile copies a file from scratchFS to servingFS.
func uploadFile(scratchFS, servingFS fs.FS, scratch, filename string) error {
	in, err := scratchFS.Open(scratch)
	if err != nil {
		return err
	}
	defer in.Close()

	out, err := gcsfs.Create(servingFS, filename)
	if err != nil {
		return err
	}
	defer out.Close()
	if _, err := io.Copy(out, in); err != nil {
		return err
	}
	if err := out.Close(); err != nil {
		return err
	}
	return nil
}

// publishArtifacts publishes artifacts for version (typically so they appear at https://go.dev/dl/).
// It returns the Go version and files that have been successfully published.
func (tasks *BuildReleaseTasks) publishArtifacts(ctx *wf.TaskContext, version string, artifacts []artifact) (task.Published, error) {
	// Each release artifact corresponds to a single website file.
	var files = make([]task.WebsiteFile, len(artifacts))
	for i, a := range artifacts {
		// Define website file metadata.
		f := task.WebsiteFile{
			Filename:       a.Filename,
			Version:        version,
			ChecksumSHA256: a.SHA256,
			Size:           int64(a.Size),
		}
		if a.Target != nil {
			f.OS = a.Target.GOOS
			f.Arch = a.Target.GOARCH
			if a.Target.GOARCH == "arm" {
				f.Arch = "armv6l"
			}
		}
		switch a.Suffix {
		case "src.tar.gz":
			f.Kind = "source"
		case "tar.gz", "zip":
			f.Kind = "archive"
		case "msi", "pkg":
			f.Kind = "installer"
		}

		// Publish it.
		if err := tasks.PublishFile(f); err != nil {
			return task.Published{}, err
		}
		ctx.Printf("Published %q.", f.Filename)
		files[i] = f
	}
	ctx.Printf("Published all %d files for %s.", len(files), version)
	return task.Published{Version: version, Files: files}, nil
}

func (b *BuildReleaseTasks) runGoogleDockerBuild(ctx context.Context, version string) (string, error) {
	// Because we want to publish versions without the leading "go", it's easiest to strip it here.
	v := strings.TrimPrefix(version, "go")
	return b.CloudBuildClient.RunBuildTrigger(ctx, b.GoogleDockerBuildProject, b.GoogleDockerBuildTrigger, map[string]string{"_GO_VERSION": v})
}

func (b *BuildReleaseTasks) awaitCloudBuild(ctx *wf.TaskContext, id string) (string, error) {
	detail, err := task.AwaitCondition(ctx, 30*time.Second, func() (string, bool, error) {
		return b.CloudBuildClient.Completed(ctx, b.GoogleDockerBuildProject, id)
	})
	return detail, err
}

// cutPrefix returns s without the provided leading prefix string
// and reports whether it found the prefix.
// If s doesn't start with prefix, cutPrefix returns s, false.
// If prefix is the empty string, cutPrefix returns s, true.
// TODO: After Go 1.21 is out, delete in favor of strings.CutPrefix.
func cutPrefix(s, prefix string) (after string, found bool) {
	if !strings.HasPrefix(s, prefix) {
		return s, false
	}
	return s[len(prefix):], true
}