// 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 main

import (
	"bufio"
	"bytes"
	"embed"
	"errors"
	"flag"
	"fmt"
	"io/fs"
	"math/rand"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"runtime"
	"slices"
	"strconv"
	"strings"
	"time"

	"golang.org/x/benchmarks/sweet/common/fileutil"

	"github.com/BurntSushi/toml"
)

type BenchStat struct {
	Name                        string
	RealTime, UserTime, SysTime time.Duration
}

type Benchmark struct {
	Name       string   // Short name for benchmark/test
	Contact    string   // Contact not used, but may be present in description
	Repo       string   // Repo + subdir where test resides, used for "go get -t -d ..."
	Tests      string   // Tests to run (regex for -test.run= )
	Benchmarks string   // Benchmarks to run (regex for -test.bench= )
	GcEnv      []string // Environment variables supplied to 'go test -c' for building, getting
	BuildFlags []string // Flags for building test (e.g., -tags purego)
	RunWrapper []string // (Inner) Command and args to precede whatever the operation is; may fail in the sandbox.
	// e.g. benchmark may run as ConfigWrapper ConfigArg BenchWrapper BenchArg ActualBenchmark
	NotSandboxed bool     // True if this benchmark cannot or should not be run in a container.
	Disabled     bool     // True if this benchmark is temporarily disabled.
	RunDir       string   // Parent directory of testdata.
	ExtraFiles   []string // other directories expected for running tests/benchmarks
	BuildDir     string   // Location of go.mod for this benchmark; download here, go test -c here.
	Version      string   // To pin a benchmark at a version.
}

type Suite struct {
	Benchmark
}

type Todo struct {
	Benchmarks     []Benchmark
	Configurations []Configuration
	Suites         []Suite
}

var verbose counterFlag

var benchFile = "benchmarks-50.toml" // default list of benchmarks
var confFile = "configurations.toml" // default list of configurations
var suiteFile = "suites.toml"        // default list of suites
var container = ""
var N = 1 // benchmark repeat count
var R = 0 // randomized build/benchmark repeat count
var groupRuns = false
var list = false
var initialize = false
var test = false
var force = false
var requireSandbox = false
var getOnly = false
var runContainer = ""       // if nonempty, skip builds and use existing named container (or binaries if -U )
var wikiTable = false       // emit the tests in a form usable in a wiki table
var explicitAll counterFlag // Include "-a" on "go test -c" test build ; repeating flag causes multiple rebuilds, useful for build benchmarking.
var shuffle = 2             // Dimensionality of (build) shuffling; 0 = none, 1 = per-benchmark, configuration ordering, 2 = bench, config pairs, 3 = across repetitions.
var reportBuildTime = true
var experiment = false    // Don't reset go.mod, for testing purposes
var minGoVersion = "1.22" // This is the release the toolchain started caring about versions of Go that are too new.

//go:embed scripts/*
var scripts embed.FS

//go:embed configs/*
var configs embed.FS

var copyExes = []string{
	"foo", "memprofile", "cpuprofile", "tmpclr", "benchtime", "benchsize", "benchdwarf", "cronjob.sh", "cmpjob.sh", "cmpcl.sh", "cmpcl-phase.sh", "tweet-results",
}

var copyConfigs = []string{
	"benchmarks-all.toml", "benchmarks-50.toml", "benchmarks-gc.toml", "benchmarks-gcplus.toml", "benchmarks-trial.toml",
	"configurations-sample.toml", "configurations-gollvm.toml", "configurations-cronjob.toml", "configurations-cmpjob.toml",
	"configurations-pgo.toml", "configurations-random.toml", "suites.toml",
}

var defaultEnv []string

// DefaultEnv returns a fresh copy of defaultEnv
func DefaultEnv() []string {
	return append([]string{}, defaultEnv...)
}

type pair struct {
	b, c int
}
type triple struct {
	b, c, k int
}

// To disambiguate repeated test runs in the same directory.
var runstamp = strings.Replace(strings.Replace(time.Now().UTC().Format("2006-01-02T15:04:05"), "-", "", -1), ":", "", -1)

func cleanup(gopath string) {
	bin := path.Join(gopath, "bin")
	if verbose > 0 {
		fmt.Printf("rm -rf %s\n", bin)
	}
	os.RemoveAll(bin)
}

func main() {

	var benchmarksString, configurationsString, stampLog string

	flag.IntVar(&N, "N", N, "benchmark/test repeat count")
	flag.IntVar(&R, "R", R, "randomize binary layouts to reduce alignment artifacts (subsumes and is incompatible with -a, -N)")
	flag.BoolVar(&groupRuns, "G", groupRuns, "group runs by benchmark (give them similar platform noise)")

	flag.Var(&explicitAll, "a", "add '-a' flag to 'go test -c' to demand full recompile. Repeat or assign a value for repeat builds for benchmarking")
	flag.IntVar(&shuffle, "s", shuffle, "dimensionality of (build) shuffling (0-3), 0 = none, 1 = per-benchmark, configuration ordering, 2 = bench, config pairs, 3 = across repetitions.")

	flag.StringVar(&benchmarksString, "b", "", "comma-separated list of test/benchmark names (default is all)")
	flag.StringVar(&benchFile, "B", benchFile, "name of file containing benchmarks to run")

	flag.StringVar(&configurationsString, "c", "", "comma-separated list of test/benchmark configurations (default is all)")
	flag.StringVar(&confFile, "C", confFile, "name of file describing configurations")

	flag.BoolVar(&requireSandbox, "sandbox", requireSandbox, "require Docker sandbox to run tests/benchmarks (& exclude unsandboxable tests/benchmarks)")

	flag.BoolVar(&getOnly, "g", getOnly, "get tests/benchmarks and dependencies, do not build or run")
	flag.StringVar(&runContainer, "r", runContainer, "skip get and build, go directly to run, using specified container (any non-empty string will do for unsandboxed execution)")

	flag.StringVar(&stampLog, "L", stampLog, "name of log file to which runstamps are appended")

	flag.BoolVar(&list, "l", list, "list available benchmarks and configurations, then exit")
	flag.BoolVar(&force, "f", force, "force run past some of the consistency checks (gopath/{pkg,bin} in particular)")
	flag.BoolVar(&initialize, "I", initialize, "initialize a directory for running tests ((re)creates Dockerfile, (re)copies in benchmark and configuration files)")
	flag.BoolVar(&test, "T", test, "run tests instead of benchmarks")

	flag.BoolVar(&wikiTable, "W", wikiTable, "print benchmark info for a wiki table")
	flag.BoolVar(&experiment, "X", experiment, "for experimental changes to 3rd party software, do not reset build/*/go.mod")

	flag.BoolVar(&reportBuildTime, "report-build-time", reportBuildTime, "report build real/CPU time as benchmark results")

	flag.Var(&verbose, "v", "print commands and other information (more -v = print more details)")

	flag.StringVar(&minGoVersion, "m", minGoVersion, "minimum Go version across all toolchains used for benchmarking")

	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
		flag.PrintDefaults()
		fmt.Fprintf(os.Stderr,
			`
%s obtains the benchmarks/tests listed in %s and
compiles and runs them according to the flags and environment
variables supplied in %s.

Specifying "-a" will pass "-a" to test compilations, but normally this
should not be needed and only slows down builds; -a with a number that
is not 1 can be used for benchmarking builds of the tests themselves.
(Don't forget to specify "all=..." for GCFLAGS if you want those
applied to the entire build.)

Both of these files can be changed with the -B and -C flags; the full
suite of benchmarks in benchmarks-all.toml is somewhat time-consuming.
Suites.toml contains the known benchmarks, their versions, and certain
necessary build or run flags.

Running with the -l flag will list all the available tests and
benchmarks for the given benchmark and configuration files.

By default benchmarks are run, not tests.  -T runs tests instead.

To run tests or benchmnarks in a docker sandbox, specify -sandbox; if
the host OS is not linux this will exclude some benchmarks that cannot
be cross-compiled.

-R and -G help with timing noise studies; -R builds a binary for each
index (builds can be parameterised by BENT_I) and -G groups benchmark
runs together so that they experience most-similar platform noise
(i.e., at a nearby time).  -R > 0 will set each configurations blank
LdFlags to "-randlayout=0x${BENT_K}a${BENT_I}".  Bent supplies BENT_I,
setting BENT_K allows runs with different sets of random link orders

All the test binaries will appear in the subdirectory 'testbin', and
test (benchmark) output will appear in the subdirectory 'bench' with
the suffix '.stdout'.  The test output is grouped by configuration to
allow easy benchmark comparisons with benchstat.  Other benchmarking
results will also appear in 'bench'.
`, os.Args[0], benchFile,
			confFile)
	}

	flag.Parse()

	if R > 0 {
		if R > 1000000 {
			fmt.Println("R must be less than or equal to 1,000,000 (1e6)")
			os.Exit(1)
		}
		if explicitAll != 0 {
			fmt.Println("Warning: -R overrides -a, using -R value")
		}
		if N != 1 {
			fmt.Println("Warning: -R overrides -N, using -R value")
		}
		if explicitAll < 0 {
			// preserve the sign; this used to be a thing, it might be again
			explicitAll = -counterFlag(R)
		} else {
			explicitAll = counterFlag(R)
		}
		N = R
	}

	if N > 1000000 {
		fmt.Println("N must be less than or equal to 1,000,000 (1e6)")
		os.Exit(1)
	}

	if requireSandbox {
		_, errDocker := exec.LookPath("docker")
		if errDocker != nil {
			fmt.Println("Sandboxing benchmarks requires the docker command")
			os.Exit(1)
		}
	}

	// Make sure our filesystem is in good shape.
	if err := checkAndSetUpFileSystem(initialize); err != nil {
		fmt.Printf("%v", err)
		os.Exit(1)
	}

	var err error
	// Create any directories we need.
	dirs, err = createDirectories()
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	todo := &Todo{}
	blobB, err := os.ReadFile(benchFile)
	if err != nil {
		fmt.Printf("There was an error opening or reading file %s: %v\n", benchFile, err)
		os.Exit(1)
	}
	blobC, err := os.ReadFile(confFile)
	if err != nil {
		fmt.Printf("There was an error opening or reading file %s: %v\n", confFile, err)
		os.Exit(1)
	}
	blobS, err := os.ReadFile(suiteFile)
	if err != nil {
		fmt.Printf("There was an error opening or reading file %s: %v\n", suiteFile, err)
		os.Exit(1)
	}
	blob := append(blobB, blobC...)
	blob = append(blob, blobS...)
	err = toml.Unmarshal(blob, todo)
	if err != nil {
		fmt.Printf("There was an error unmarshalling %s: %v\n", string(blob), err)
		os.Exit(1)
	}

	// Copy defaults for benchmarks from suites.
	// (old code had these associated with the "benchmarks" files)
	suites := make(map[string]*Suite)

	for i, s := range todo.Suites {
		suites[s.Name] = &todo.Suites[i]
	}

	update := func(a *string, s string) {
		if *a == "" {
			*a = s
		}
	}

	updateFlags := func(a *[]string, s []string) {
		if *a == nil {
			*a = s
		}
	}

	for i := range todo.Benchmarks {
		b := &todo.Benchmarks[i]
		s := suites[b.Name]
		if s == nil {
			fmt.Printf("Benchmark %s appearing in %s is not listed in %s\n", b.Name, benchFile, suiteFile)
			os.Exit(1)
		}
		update(&b.Repo, s.Repo)
		update(&b.Version, s.Version)
		update(&b.Tests, s.Tests)
		update(&b.Benchmarks, s.Benchmarks)

		b.Disabled = s.Disabled || b.Disabled
		b.NotSandboxed = s.NotSandboxed || b.NotSandboxed

		updateFlags(&b.ExtraFiles, s.ExtraFiles)
		updateFlags(&b.BuildFlags, s.BuildFlags)
		updateFlags(&b.GcEnv, s.GcEnv)
	}

	var moreArgs []string
	if flag.NArg() > 0 {
		for i, arg := range flag.Args() {
			if i == 0 && (arg == "-" || arg == "--") {
				continue
			}
			moreArgs = append(moreArgs, arg)
		}
	}

	benchmarks := csToSet(benchmarksString)
	configurations := csToSet(configurationsString)

	if wikiTable {
		for _, bench := range todo.Benchmarks {
			s := bench.Benchmarks
			s = strings.Replace(s, "|", "\\|", -1)
			fmt.Printf(" | %s | | `%s` | `%s` | |\n", bench.Name, bench.Repo, s)
		}
		return
	}

	// Normalize configuration goroot names by ensuring they end in '/'
	// Process command-line-specified configurations.
	// Expand environment variables mentioned there.
	duplicates := make(map[string]bool)
	for i := range todo.Configurations {
		trial := &todo.Configurations[i]
		trial.Name = os.ExpandEnv(trial.Name)
		if duplicates[trial.Name] {
			fmt.Printf("Saw duplicate configuration %s at index %d\n", trial.Name, i)
			os.Exit(1)
		}
		duplicates[trial.Name] = true
		if configurations != nil {
			_, present := configurations[trial.Name]
			trial.Disabled = !present
			if present {
				configurations[trial.Name] = false
			}
		}
		if root := trial.Root; len(root) != 0 {
			// TODO(jfaller): I don't think we need this "/" anymore... investigate.
			trial.Root = os.ExpandEnv(root) + "/"
		}
		if len(trial.RunWrapper) > 0 {
			// Args will be expanded later with BENT_ environment variables injected.
			// TODO should it use concatenation of os env and configuration env?
			trial.RunWrapper[0] = os.ExpandEnv(trial.RunWrapper[0])
		}
		// TODO would anyone ever make these depend on BENT_I etc?
		trial.PgoGen = os.ExpandEnv(trial.PgoGen)
		trial.PgoUse = os.ExpandEnv(trial.PgoUse)
		if R > 0 && trial.LdFlags == "" {
			trial.LdFlags = "-randlayout=0x${BENT_K}a${BENT_I}"
		}
	}
	for b, v := range configurations {
		if v {
			fmt.Printf("Configuration %s listed after -c does not appear in %s\n", b, confFile)
			os.Exit(1)
		}
	}

	// Normalize benchmark names by removing any trailing '/'.
	// Normalize Test and Benchmark specs by replacing missing value with something that won't match anything.
	// Process command-line-specified benchmarks
	duplicates = make(map[string]bool)
	for i, bench := range todo.Benchmarks {

		if duplicates[bench.Name] {
			fmt.Printf("Saw duplicate benchmark %s at index %d\n", bench.Name, i)
			os.Exit(1)
		}
		duplicates[bench.Name] = true

		if benchmarks != nil {
			_, present := benchmarks[bench.Name]
			todo.Benchmarks[i].Disabled = !present
			if present {
				benchmarks[bench.Name] = false
			}
		}
		// Trim possible trailing slash, do not want
		if '/' == bench.Repo[len(bench.Repo)-1] {
			bench.Repo = bench.Repo[:len(bench.Repo)-1]
			todo.Benchmarks[i].Repo = bench.Repo
		}
		if "" == bench.Version {
			todo.Benchmarks[i].Version = "@latest"
		}
		if "" == bench.Tests || !test {
			if !test {
				todo.Benchmarks[i].Tests = "none"
			} else {
				todo.Benchmarks[i].Tests = "Test"
			}
		}
		if "" == bench.Benchmarks || test {
			if !test {
				todo.Benchmarks[i].Benchmarks = "Benchmark"
			} else {
				todo.Benchmarks[i].Benchmarks = "none"
			}
		}
		if !requireSandbox {
			todo.Benchmarks[i].NotSandboxed = true
		}
		if requireSandbox && todo.Benchmarks[i].NotSandboxed {
			if runtime.GOOS == "linux" {
				fmt.Printf("Removing sandbox for %s\n", bench.Name)
				todo.Benchmarks[i].NotSandboxed = false
			} else {
				fmt.Printf("Disabling %s because it requires sandbox\n", bench.Name)
				todo.Benchmarks[i].Disabled = true
			}
		}
	}
	for b, v := range benchmarks {
		if v {
			fmt.Printf("Benchmark %s listed after -b does not appear in %s\n", b, benchFile)
			os.Exit(1)
		}
	}

	// If more verbose, print the normalized configuration.
	if verbose > 1 {
		buf := new(bytes.Buffer)
		if err := toml.NewEncoder(buf).Encode(todo); err != nil {
			fmt.Printf("There was an error encoding %v: %v\n", todo, err)
			os.Exit(1)
		}
		fmt.Println(buf.String())
	}

	if list {
		fmt.Println("Benchmarks:")
		for _, x := range todo.Benchmarks {
			s := x.Name + " (repo=" + x.Repo + x.Version + ")"
			if x.Disabled {
				s += " (disabled)"
			}
			fmt.Printf("   %s\n", s)
		}
		fmt.Println("Configurations:")
		for _, x := range todo.Configurations {
			s := x.Name
			if x.Root != "" {
				s += " (goroot=" + x.Root + ")"
			}
			if x.Disabled {
				s += " (disabled)"
			}
			fmt.Printf("   %s\n", s)
		}
		return
	}

	if stampLog != "" {
		f, err := os.OpenFile(stampLog, os.O_WRONLY|os.O_APPEND|os.O_CREATE, os.ModePerm)
		if err != nil {
			fmt.Printf("There was an error opening %s for output, error %v\n", stampLog, err)
			os.Exit(2)
		}
		fmt.Fprintf(f, "%s\t%v\n", runstamp, os.Args)
		f.Close()
	}

	defaultEnv = inheritEnv(defaultEnv, "PATH")
	defaultEnv = inheritEnv(defaultEnv, "USER")
	defaultEnv = inheritEnv(defaultEnv, "HOME")
	defaultEnv = inheritEnv(defaultEnv, "SHELL")
	for _, e := range os.Environ() {
		if strings.HasPrefix(e, "GO") || strings.HasPrefix(e, "BENT") {
			defaultEnv = append(defaultEnv, e)
		}
	}
	defaultEnv = inheritEnv(defaultEnv, "http_proxy")
	defaultEnv = inheritEnv(defaultEnv, "https_proxy")
	defaultEnv = replaceEnv(defaultEnv, "GOPATH", dirs.gopath)
	defaultEnv = replaceEnv(defaultEnv, "GOOS", runtime.GOOS)
	defaultEnv = replaceEnv(defaultEnv, "GOARCH", runtime.GOARCH)
	defaultEnv = ifMissingAddEnv(defaultEnv, "GO111MODULE", "auto")

	envRoot := os.Getenv("ROOT")
	if envRoot == "" {
		envRoot = os.Getenv("PWD")
	}
	defaultEnv = append(defaultEnv, "ROOT="+envRoot)

	var needSandbox bool    // true if any benchmark needs a sandbox
	var needNotSandbox bool // true if any benchmark needs to be not sandboxed

	var getAndBuildFailures []string

	// Ignore the error -- TODO note the difference between exists already and other errors.

	for i, config := range todo.Configurations {
		if !config.Disabled { // Don't overwrite if something was disabled.
			s := config.thingBenchName("stdout")
			f, err := os.OpenFile(s, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.ModePerm)
			if err != nil {
				fmt.Printf("There was an error opening %s for output, error %v\n", s, err)
				os.Exit(2)
			}
			todo.Configurations[i].benchWriter = f
		}
	}

	// It is possible to request repeated builds for compiler/linker benchmarking.
	// Normal (non-negative build count) varies configuration most frequently,
	// then benchmark, then repeats the process N times (innerBuildCount = 1).
	// If build count is negative, the configuration varies least frequently,
	// and each benchmark is built buildCount (innerBuildCount) times before
	// moving on to the next. (This tends to focus intermittent benchmarking
	// noise on single configuration-benchmark combos.  This is the "old way".
	buildCount := int(explicitAll)
	if buildCount < 0 {
		buildCount = -buildCount
	}
	if buildCount == 0 {
		buildCount = 1
	}

	for i := range todo.Benchmarks {
		bench := &todo.Benchmarks[i]

		if bench.Disabled {
			continue
		}

		// Use a separate build directory and go.mod for each benchmark, otherwise there can be conflicts.
		// Initialize before building because this information tells where to run the test, also.
		bench.BuildDir = path.Join(dirs.build, bench.Name)
	}

	if runContainer == "" { // If not reusing binaries/container...
		if verbose == 0 {
			fmt.Print("Go getting")
		}

		// Obtain (go get -d -t -v bench.Repo) all benchmarks, once, populating src
		for i := range todo.Benchmarks {
			bench := &todo.Benchmarks[i]

			if bench.Disabled {
				continue
			}

			// Use a separate go.mod for each benchmark, otherwise there can be conflicts.
			if err := mkdirAsNeeded(bench.BuildDir); err != nil {
				fmt.Printf("Couldn't create build subdirectory %s, error=%v", bench.BuildDir, err)
				os.Exit(2)
			}

			getFiles := true

			goDotMod := path.Join(bench.BuildDir, "go.mod")
			if _, err := os.Stat(goDotMod); err == nil {
				if !experiment {
					os.Remove(goDotMod) // always want a fresh go.mod
				} else {
					getFiles = false
				}
			}
			if getFiles {
				goModPath := filepath.Join(bench.BuildDir, "go.mod")
				f, err := os.Create(goModPath)
				if err != nil {
					fmt.Printf("Error creating go.mod: %v", err)
					os.Exit(2)
				}
				goMod := fmt.Sprintf(goMod, minGoVersion)
				_, err = fmt.Fprintln(f, goMod)
				if err != nil {
					fmt.Printf("Error writing go.mod: %v", err)
					f.Close()
					os.Exit(2)
				}
				if err := f.Close(); err != nil {
					fmt.Printf("Error closing go.mod: %v", err)
					os.Exit(2)
				}
				if verbose > 0 {
					fmt.Printf("(cd %s; cat <<EOF > %s\n%s\nEOF)\n", bench.BuildDir, "go.mod", goMod)
				} else {
					fmt.Print(".")
				}

				cmd := exec.Command("go", "get", "-d", "-t", "-v", bench.Repo+bench.Version)
				cmd.Env = DefaultEnv()
				cmd.Dir = bench.BuildDir

				if !bench.NotSandboxed { // Do this so that OS-dependent dependencies are done correctly.
					cmd.Env = replaceEnv(cmd.Env, "GOOS", "linux")
				}
				cmd.Env = replaceEnvs(cmd.Env, sliceExpandEnv(bench.GcEnv, cmd.Env))
				if verbose > 0 {
					fmt.Println(asCommandLine(dirs.wd, cmd))
				} else {
					fmt.Print(".")
				}
				_, err = cmd.Output()
				if err != nil {
					ee := err.(*exec.ExitError)
					s := fmt.Sprintf("There was an error running 'go get', stderr = %s", ee.Stderr)
					fmt.Println(s + "DISABLING benchmark " + bench.Name)
					getAndBuildFailures = append(getAndBuildFailures, s+"("+bench.Name+")\n")
					todo.Benchmarks[i].Disabled = true
					continue
				}
			}

			needSandbox = !bench.NotSandboxed || needSandbox
			needNotSandbox = bench.NotSandboxed || needNotSandbox
		}
		if verbose == 0 {
			fmt.Println()
		}

		if getOnly {
			return
		}

		// Create build-related benchmark files
		for ci := range todo.Configurations {
			todo.Configurations[ci].createFilesForLater()
		}

		// Compile tests and move to ./testbin/Bench_Config.
		// If any test needs sandboxing, then one docker container will be created
		// (that contains all the tests).

		if verbose == 0 {
			fmt.Print("Building goroots")
		}

		// First for each configuration, get the compiler and library and install it in its own GOROOT.
		for ci, config := range todo.Configurations {
			if config.Disabled {
				continue
			}

			root := config.Root

			rootCopy := path.Join(dirs.goroots, config.Name)
			if verbose > 0 {
				fmt.Printf("rm -rf %s\n", rootCopy)
			}
			os.RemoveAll(rootCopy)
			config.rootCopy = rootCopy
			todo.Configurations[ci] = config

			docopy := func(from, to string) {
				fileutil.CopyDir(to, from, nil)
				if verbose > 0 || err != nil {
					fmt.Printf("rsync -a %s %s, error=%v\n", from, to, err)
				}
			}

			docopy(path.Join(root, "bin"), path.Join(rootCopy, "bin"))
			docopy(path.Join(root, "src"), path.Join(rootCopy, "src"))
			docopy(path.Join(root, "pkg"), path.Join(rootCopy, "pkg"))

			gocmd := config.goCommandCopy()

			buildLibrary := func(withAltOS bool) {
				if withAltOS && runtime.GOOS == "linux" {
					return // The alternate OS is linux
				}
				cmd := exec.Command(gocmd, "install", "-a")
				cmd.Env = DefaultEnv()
				if withAltOS {
					cmd.Env = replaceEnv(cmd.Env, "GOOS", "linux")
				}
				if rootCopy != "" {
					cmd.Env = replaceEnv(cmd.Env, "GOROOT", rootCopy)
				}
				cmd.Env = replaceEnvs(cmd.Env, sliceExpandEnv(config.GcEnv, cmd.Env))

				cmd.Args = append(cmd.Args, sliceExpandEnv(config.BuildFlags, cmd.Env)...)
				if config.GcFlags != "" {
					cmd.Args = append(cmd.Args, "-gcflags="+expandEnv(config.GcFlags, cmd.Env))
				}
				cmd.Args = append(cmd.Args, "std")

				s, _ := config.runBinary("", cmd, true)
				if s != "" {
					fmt.Println("Error running go install std, ", s)
					config.Disabled = true
				}
			}

			if needSandbox {
				buildLibrary(true)
			}
			if needNotSandbox {
				buildLibrary(false)
			}
			todo.Configurations[ci] = config
			if config.Disabled {
				continue
			}
		}

		if verbose == 0 {
			fmt.Print("\nCompiling")
		}

		switch shuffle {
		case 0: // N times, for each benchmark, for each configuration, build.
			for yyy := 0; yyy < buildCount; yyy++ {
				for bi, bench := range todo.Benchmarks {
					if bench.Disabled {
						continue
					}
					for ci, config := range todo.Configurations {
						if config.Disabled {
							continue
						}
						s := todo.Configurations[ci].compileOne(&todo.Benchmarks[bi], dirs.wd, yyy, R > 0)
						if s != "" {
							getAndBuildFailures = append(getAndBuildFailures, s)
						}
					}
				}
			}
		case 1: // N times, for each benchmark, shuffle configurations and build with
			permute := make([]int, len(todo.Configurations))
			for ci := range todo.Configurations {
				permute[ci] = ci
			}

			for yyy := 0; yyy < buildCount; yyy++ {
				for bi, bench := range todo.Benchmarks {
					if bench.Disabled {
						continue
					}

					rand.Shuffle(len(permute), func(i, j int) { permute[i], permute[j] = permute[j], permute[i] })

					for ci := range todo.Configurations {
						config := &todo.Configurations[permute[ci]]
						if config.Disabled {
							continue
						}
						s := config.compileOne(&todo.Benchmarks[bi], dirs.wd, yyy, R > 0)
						if s != "" {
							getAndBuildFailures = append(getAndBuildFailures, s)
						}
					}
				}
			}
		case 2: // N times, shuffle combination of benchmarks and configuration, build them all
			permute := make([]pair, len(todo.Configurations)*len(todo.Benchmarks))
			i := 0
			for bi := range todo.Benchmarks {
				for ci := range todo.Configurations {
					permute[i] = pair{b: bi, c: ci}
					i++
				}
			}

			for yyy := 0; yyy < buildCount; yyy++ {
				rand.Shuffle(len(permute), func(i, j int) { permute[i], permute[j] = permute[j], permute[i] })
				for _, p := range permute {
					bench := &todo.Benchmarks[p.b]
					config := &todo.Configurations[p.c]
					if bench.Disabled || config.Disabled {
						continue
					}
					s := config.compileOne(bench, dirs.wd, yyy, R > 0)
					if s != "" {
						getAndBuildFailures = append(getAndBuildFailures, s)
					}
				}
			}

		case 3: // Shuffle all the N copies of all the benchmark and configuration pairs, build them all.
			permute := make([]triple, buildCount*len(todo.Configurations)*len(todo.Benchmarks))
			i := 0
			for k := 0; k < buildCount; k++ {
				for bi := range todo.Benchmarks {
					for ci := range todo.Configurations {
						permute[i] = triple{b: bi, c: ci, k: k}
						i++
					}
				}
			}
			rand.Shuffle(len(permute), func(i, j int) { permute[i], permute[j] = permute[j], permute[i] })

			for _, p := range permute {
				bench := &todo.Benchmarks[p.b]
				config := &todo.Configurations[p.c]
				if bench.Disabled || config.Disabled {
					continue
				}
				s := config.compileOne(bench, dirs.wd, p.k, R > 0)
				if s != "" {
					getAndBuildFailures = append(getAndBuildFailures, s)
				}
			}
		}

		if verbose == 0 {
			fmt.Println()
		}

		// As needed, create the sandbox.
		if needSandbox {
			if verbose == 0 {
				fmt.Print("Making sandbox")
			}
			cmd := exec.Command("docker", "build", "-q", ".")
			if verbose > 0 {
				fmt.Println(asCommandLine(dirs.wd, cmd))
			}
			// capture standard output to get container name
			output, err := cmd.Output()
			if err != nil {
				ee := err.(*exec.ExitError)
				fmt.Printf("There was an error running 'docker build', stderr = %s\n", ee.Stderr)
				os.Exit(2)
				return
			}
			// Docker prints stuff AFTER the container, thanks, Docker.
			sc := bufio.NewScanner(bytes.NewReader(output))
			if !sc.Scan() {
				fmt.Printf("Could not scan line from '%s'\n", string(output))
				os.Exit(2)
				return
			}
			container = strings.TrimSpace(sc.Text())
			if verbose == 0 {
				fmt.Println()
			}
			fmt.Printf("Container for sandboxed bench/test runs is %s\n", container)
		}
	} else {
		container = runContainer
		if getOnly { // -r -g is a bit of a no-op, but that's what it implies.
			return
		}
	}

	// Initialize RunDir for benchmarks.
benchmarks_loop:
	for i := range todo.Benchmarks {
		bench := &todo.Benchmarks[i]
		if bench.Disabled {
			continue
		}
		// Obtain directory containing testdata, if any:
		// Capture output of "go list -f {{.Dir}} $PKG"

		cmd := exec.Command("go", "list", "-f", "{{.Dir}}", bench.Repo)
		cmd.Env = DefaultEnv()
		cmd.Dir = bench.BuildDir

		if verbose > 0 {
			fmt.Println(asCommandLine(dirs.wd, cmd))
		} else {
			fmt.Print(".")
		}
		out, err := cmd.Output()
		if err != nil {
			s := fmt.Sprintf(`could not go list -f {{.Dir}} %s, err=%v`, bench.Repo, err)
			fmt.Println(s + "\nDISABLING benchmark " + bench.Name)
			getAndBuildFailures = append(getAndBuildFailures, s+"("+bench.Name+")\n")
			todo.Benchmarks[i].Disabled = true
			continue
		} else if verbose > 0 {
			fmt.Printf("# Rundir=%s\n", string(out))
		}
		rundir := strings.TrimSpace(string(out))
		if !bench.NotSandboxed {
			// if sandboxed, strip cwd from prefix of rundir.
			rundir = rundir[len(dirs.wd):]
		}
		bench.RunDir = bench.BuildDir

		copy := func(subdir string, failIfMissing bool) bool {
			// as necessary, make a copy of subdir
			testdata := path.Join(rundir, subdir)
			if stat, err := os.Stat(testdata); err == nil {
				testdataCopy := path.Join(bench.RunDir, subdir)
				var err error
				var commandLine string
				os.RemoveAll(testdataCopy) // clean out what can be cleaned
				if stat.IsDir() {
					if verbose > 0 {
						fmt.Printf("mkdir -p %s\n", testdataCopy)
					}
					os.Mkdir(testdataCopy, fs.FileMode(0755))
					err = fileutil.CopyDir(testdataCopy, testdata, nil)
					if verbose > 0 || err != nil {
						commandLine = fmt.Sprintf("rsync -a %s/ %s", testdata, testdataCopy)
					}
				} else {
					err = fileutil.CopyFile(testdataCopy, testdata, nil, nil)
					if verbose > 0 || err != nil {
						commandLine = fmt.Sprintf("cp -p %s %s", testdata, testdataCopy)
					}
				}
				if verbose > 0 {
					fmt.Println(commandLine)
				}
				if err != nil {
					s := fmt.Sprintf(`could not %s, err=%v`, commandLine, err)
					fmt.Println(s + "\nDISABLING benchmark " + bench.Name)
					getAndBuildFailures = append(getAndBuildFailures, s+"("+bench.Name+")\n")
					todo.Benchmarks[i].Disabled = true
					return true
				}
				return false
			}
			if failIfMissing {
				s := fmt.Sprintf(`could not find file/directory %s to copy`, testdata)
				fmt.Println(s + "\nDISABLING benchmark " + bench.Name)
				getAndBuildFailures = append(getAndBuildFailures, s+"("+bench.Name+")\n")
				todo.Benchmarks[i].Disabled = true
			}
			return failIfMissing
		}
		for _, s := range bench.ExtraFiles {
			if copy(s, true) {
				continue benchmarks_loop
			}
		}
		copy("testdata", false)
	}

	var failures []string

	// If there's a bad error running one of the benchmarks, report what we've got, please.
	defer func(t *Todo) {
		for _, config := range todo.Configurations {
			if !config.Disabled { // Don't overwrite if something was disabled.
				config.benchWriter.Close()
			}
		}
		if needSandbox {
			// Print this a second time so it doesn't get missed.
			fmt.Printf("Container for sandboxed bench/test runs is %s\n", container)
		}
		if len(failures) > 0 {
			fmt.Println("FAILURES:")
			for _, f := range failures {
				fmt.Println(f)
			}
		}
		if len(getAndBuildFailures) > 0 {
			fmt.Println("Get and build failures:")
			for _, f := range getAndBuildFailures {
				fmt.Println(f)
			}
		}
	}(todo)

	maxrc := 0

	if verbose == 0 {
		// Terminate any "...." printed before so that benchmarking info will have a new line.
		fmt.Println()
	}

	var runs []*Run

	// N repetitions for each configurationm, run all the benchmarks.
	// TODO randomize the benchmarks and configurations, like for builds.
	for i := 0; i < N; i++ {
		// For each configuration, run all the benchmarks.
		for j := range todo.Configurations {
			c := &todo.Configurations[j]
			if c.Disabled {
				continue
			}

			for k := range todo.Benchmarks {
				b := &todo.Benchmarks[k]
				if b.Disabled {
					continue
				}

				runs = append(runs, &Run{c, b, i})
			}
		}
	}

	rand.Shuffle(len(runs), func(i, j int) { runs[i], runs[j] = runs[j], runs[i] })

	benchTogether := func(r, s *Run) int {
		if r.b.Name == s.b.Name {
			return r.i>>1 - s.i>>1 // small numbers will not overflow.
		}
		return strings.Compare(r.b.Name, s.b.Name)
	}

	nTogether := func(r, s *Run) int {
		return r.i - s.i // small numbers will not overflow.
	}

	less := nTogether

	if groupRuns {
		less = benchTogether
	}

	slices.SortStableFunc(runs, less)

	if verbose > 0 {
		for _, r := range runs {
			fmt.Println(r.String())
		}
	}

	for _, r := range runs {
		s, rc := benchOne(r.c, r.b, r.i, moreArgs)

		if s != "" {
			fmt.Println(s)
			failures = append(failures, s)
		}
		if rc > maxrc {
			maxrc = rc
		}
	}

	if maxrc > 0 {
		os.Exit(maxrc)
	}
}

type Run struct {
	c *Configuration
	b *Benchmark
	i int
}

func (r *Run) String() string {
	return r.c.Name + "-" + r.b.Name + "-" + strconv.FormatInt(int64(r.i), 10)
}

// benchOne runs a single benchmarks b in configuration c at iteration i, applying moreArgs to the run.
// it returns the output and the return code.
//
// if either the configuration or benchmark is disabled, return with empty output and no change (0)
// to the return code.
func benchOne(c *Configuration, b *Benchmark, i int, moreArgs []string) (s string, rc int) {
	if c.Disabled || b.Disabled {
		return
	}

	root := c.Root

	testBinaryName := c.benchName(b, i, R > 0)

	runEnv := []string{}
	runEnv = append(runEnv, "BENT_CONFIG="+c.Name)
	runEnv = append(runEnv, "BENT_BENCH="+b.Name)
	runEnv = append(runEnv, "BENT_I="+strconv.FormatInt(int64(i), 10))
	runEnv = append(runEnv, "BENT_BINARY="+testBinaryName)

	wrapperPrefix := "/"
	if b.NotSandboxed {
		wrapperPrefix = dirs.wd + "/"
	}
	wrapperFor := func(s []string) string {
		x := ""
		if len(s) > 0 {
			// If not an explicit path, then make it an explicit path
			x = s[0]
			if x[0] != '/' {
				x = wrapperPrefix + x
			}
		}
		return x
	}

	crw := c.RunWrapper
	if c.PgoGen != "" {
		// We want to generate pprof file for using pgo
		crw = append(crw, wrapperFor([]string{"cpuprofile"}))
	}

	configWrapper := wrapperFor(crw)
	benchWrapper := wrapperFor(b.RunWrapper)

	var wrappersAndBin []string

	if configWrapper != "" {
		wrappersAndBin = append(wrappersAndBin, configWrapper)
		wrappersAndBin = append(wrappersAndBin, crw[1:]...)
	}
	if benchWrapper != "" {
		wrappersAndBin = append(wrappersAndBin, benchWrapper)
		wrappersAndBin = append(wrappersAndBin, b.RunWrapper[1:]...)
	}

	if b.NotSandboxed {
		bin := path.Join(dirs.wd, dirs.testBinDir, testBinaryName)
		wrappersAndBin = append(wrappersAndBin, bin)

		cmd := exec.Command(wrappersAndBin[0], wrappersAndBin[1:]...)
		cmd.Args = append(cmd.Args, "-test.run="+b.Tests)
		cmd.Args = append(cmd.Args, "-test.bench="+b.Benchmarks)

		cmd.Dir = b.RunDir
		cmd.Env = DefaultEnv()
		if root != "" {
			cmd.Env = replaceEnv(cmd.Env, "GOROOT", root)
		}
		cmd.Env = append(cmd.Env, "BENT_DIR="+dirs.wd)
		cmd.Env = append(cmd.Env, "BENT_PROFILES="+path.Join(dirs.wd, c.thingBenchName("profiles")))
		if c.PgoGen != "" {
			// We want to generate pprof file for using pgo
			cmd.Env = append(cmd.Env, "BENT_PGO="+path.Join(dirs.wd, c.PgoGen))
		}

		cmd.Env = append(cmd.Env, runEnv...)
		cmd.Env = append(cmd.Env, sliceExpandEnv(c.RunEnv, cmd.Env)...)

		cmd.Args = append(cmd.Args, c.RunFlags...)
		cmd.Args = append(cmd.Args, moreArgs...)
		cmd.Args = sliceExpandEnv(cmd.Args, cmd.Env)

		c.say("\n") // force a newline, there may have been loggy-gunk before this.
		c.say("shortname: " + b.Name + "\n")
		c.say("toolchain: " + c.Name + "\n")
		s, rc = c.runBinary(dirs.wd, cmd, false)
	} else {
		// docker run --net=none -e GOROOT=... -w /src/github.com/minio/minio/cmd $D /testbin/cmd_Config.test -test.short -test.run=Nope -test.v -test.bench=Benchmark'(Get|Put|List)'
		// TODO(jfaller): I don't think we need either of these "/" below, investigate...

		// TODO this all very undertested right now.

		bin := "/" + path.Join(dirs.testBinDir, testBinaryName)
		wrappersAndBin = append(wrappersAndBin, bin)

		cmd := exec.Command("docker", "run", "--net=none", "-w", b.RunDir)

		for _, e := range runEnv {
			cmd.Args = append(cmd.Args, "-e", e)
		}

		cmd.Args = append(cmd.Args, "-e", "BENT_PROFILES="+path.Join(dirs.wd, c.thingBenchName("profiles")))

		if c.PgoGen != "" {
			// We want to generate pprof file for using pgo
			cmd.Args = append(cmd.Args, "-e", "BENT_PGO="+path.Join(dirs.wd, c.PgoGen))
		}

		cmd.Args = append(cmd.Args, container)
		cmd.Args = append(cmd.Args, wrappersAndBin...)
		cmd.Args = append(cmd.Args, "-test.run="+b.Tests)
		cmd.Args = append(cmd.Args, "-test.bench="+b.Benchmarks)

		cmd.Args = append(cmd.Args, c.RunFlags...)
		cmd.Args = append(cmd.Args, moreArgs...)
		cmd.Args = sliceExpandEnv(cmd.Args, runEnv)

		c.say("\n") // force a newline, there may have been loggy-gunk before this.
		c.say("shortname: " + b.Name + "\n")
		c.say("toolchain: " + c.Name + "\n")
		s, rc = c.runBinary(dirs.wd, cmd, false)
	}
	return s, rc
}

var goMod = `module build

go %s
`

func escape(s string) string {
	s = strings.Replace(s, "\\", "\\\\", -1)
	s = strings.Replace(s, "'", "\\'", -1)
	// Conservative guess at characters that will force quoting
	if strings.ContainsAny(s, "\\ ;#*&$~?!|[]()<>{}`") {
		s = " '" + s + "'"
	} else {
		s = " " + s
	}
	return s
}

// asCommandLine renders cmd as something that could be copy-and-pasted into a command line
func asCommandLine(cwd string, cmd *exec.Cmd) string {
	s := "("
	if cmd.Dir != "" && cmd.Dir != cwd {
		s += "cd" + escape(cmd.Dir) + ";"
	}
	for _, e := range cmd.Env {
		if !strings.HasPrefix(e, "PATH=") &&
			!strings.HasPrefix(e, "HOME=") &&
			!strings.HasPrefix(e, "USER=") &&
			!strings.HasPrefix(e, "SHELL=") {
			s += escape(e)
		}
	}
	for _, a := range cmd.Args {
		s += escape(a)
	}
	s += " )"
	return s
}

// checkAndSetUpFileSystem does a number of tasks to ensure that the tests will
// run properly.
//
// First, it makes sure we're not going to accidentally overwrite previous results.
// Then, it shouldInit is true, it:
//   - Creates a Dockerfile.
//   - Creates all the configuration files.
//   - Exits.
func checkAndSetUpFileSystem(shouldInit bool) error {
	// To avoid bad surprises, look for pkg and bin, if they exist, refuse to run
	_, derr := os.Stat("Dockerfile")
	_, perr := os.Stat(path.Join("gopath", "pkg"))

	if derr != nil && !shouldInit {
		// Missing Dockerfile
		return errors.New("Missing 'Dockerfile', please rerun with -I (initialize) flag if you intend to use this directory.\n")
	}

	if shuffle < 0 || shuffle > 3 {
		return fmt.Errorf("Shuffle value (-s) ought to be between 0 and 3, inclusive, instead is %d\n", shuffle)
	}

	// Initialize the directory, copying in default benchmarks and sample configurations, and creating a Dockerfile
	if shouldInit {
		if perr == nil {
			if !force {
				fmt.Printf("It looks like you've already initialized this directory, remove ./gopath/pkg if you want to reinit.\n")
				os.Exit(1)
			}
			fmt.Printf("Directory appears to already be initialized, but -f (force) so copying files anyway.\n")
		}
		for _, s := range copyExes {
			copyAsset(scripts, "scripts", s)
			os.Chmod(s, 0755)
		}
		for _, s := range copyConfigs {
			copyAsset(configs, "configs", s)
		}

		err := os.WriteFile("Dockerfile",
			[]byte(`
FROM ubuntu
ADD . /
`), 0664)
		if err != nil {
			return err
		}
		fmt.Printf("Created Dockerfile\n")
		os.Exit(0)
	}
	return nil
}

func copyAsset(fs embed.FS, dir, file string) {
	f, err := fs.Open(path.Join(dir, file))
	if err != nil {
		fmt.Printf("Error opening asset %s\n", file)
		os.Exit(1)
	}
	stat, err := f.Stat()
	if err != nil {
		fmt.Printf("Error reading stats %s\n", file)
		os.Exit(1)
	}
	bytes := make([]byte, stat.Size())
	if l, err := f.Read(bytes); err != nil || l != int(stat.Size()) {
		fmt.Printf("Error reading asset %s\n", file)
		os.Exit(1)
	}
	err = os.WriteFile(file, bytes, 0664)
	if err != nil {
		fmt.Printf("Error writing %s\n", file)
		os.Exit(1)
	}
	fmt.Printf("Copied asset %s to current directory\n", file)
}

type directories struct {
	wd, gopath, goroots, build, testBinDir, benchDir string
}

// createDirectories creates all the directories we need.
func createDirectories() (*directories, error) {
	cwd, err := os.Getwd()
	if err != nil {
		fmt.Printf("Could not get current working directory %v\n", err)
		os.Exit(1)
	}
	dirs := &directories{
		wd:         cwd,
		gopath:     path.Join(cwd, "gopath"),
		goroots:    path.Join(cwd, "goroots"),
		build:      path.Join(cwd, "build"),
		testBinDir: "testbin",
		benchDir:   "bench",
	}
	for _, d := range []string{dirs.gopath, dirs.goroots, dirs.build, path.Join(cwd, dirs.testBinDir), path.Join(cwd, dirs.benchDir)} {
		if err := mkdirAsNeeded(d); err != nil {
			return nil, fmt.Errorf("error creating %v: %v", d, err)
		}
	}
	return dirs, nil
}

// mkdirAsNeeded creates directory d with mode 0775 if it does not exist already.
func mkdirAsNeeded(d string) error {
	if err := os.Mkdir(d, 0775); err != nil && !errors.Is(err, fs.ErrExist) {
		return fmt.Errorf("error creating %v: %v", d, err)
	}
	return nil
}

// inheritEnv extracts ev from the os environment and
// returns env extended with that new environment variable.
// Does not check if ev already exists in env.
func inheritEnv(env []string, ev string) []string {
	evv := os.Getenv(ev)
	if evv != "" {
		env = append(env, ev+"="+evv)
	}
	return env
}

func getenv(env []string, ev string) string {
	evplus := ev + "="
	for _, v := range env {
		if strings.HasPrefix(v, evplus) {
			return v[len(evplus):]
		}
	}
	return ""
}

func expandEnv(s string, env []string) string {
	expand := func(s string) string {
		return getenv(env, s)
	}
	return os.Expand(s, expand)
}

func sliceExpandEnv(slice, env []string) []string {
	result := slice
	changed := false
	expand := func(s string) string {
		return getenv(env, s)
	}
	for j, s := range slice {
		v := os.Expand(s, expand)
		if !changed {
			if v == s {
				continue
			}
			changed = true
			result = append([]string{}, slice[0:j]...)
		}
		result = append(result, v)
	}
	return result
}

// replaceEnv returns a new environment derived from env
// by removing any existing definition of ev and adding ev=evv.
func replaceEnv(env []string, ev string, evv string) []string {
	evplus := ev + "="
	var newenv []string
	for _, v := range env {
		if !strings.HasPrefix(v, evplus) {
			newenv = append(newenv, v)
		}
	}
	newenv = append(newenv, evplus+evv)
	return newenv
}

// replaceEnvs returns a new environment derived from env
// by replacing or adding all modifiers in newevs.
func replaceEnvs(env, newevs []string) []string {
	for _, e := range newevs {
		var newenv []string
		eq := strings.IndexByte(e, '=')
		if eq == -1 {
			panic("Bad input to replaceEnvs, ought to be slice of e=v")
		}
		evplus := e[0 : eq+1]
		for _, v := range env {
			if !strings.HasPrefix(v, evplus) {
				newenv = append(newenv, v)
			}
		}
		env = append(newenv, e)
	}
	return env
}

// ifMissingAddEnv returns a new environment derived from env
// by adding ev=evv if env does not define env.
func ifMissingAddEnv(env []string, ev string, evv string) []string {
	evplus := ev + "="
	for _, v := range env {
		if strings.HasPrefix(v, evplus) {
			return env
		}
	}
	env = append(env, evplus+evv)
	return env
}

// csToSet converts a comma-separated string into the set of strings between the commas.
func csToSet(s string) map[string]bool {
	if s == "" {
		return nil
	}
	m := make(map[string]bool)
	ss := strings.Split(s, ",")
	for _, sss := range ss {
		m[sss] = true
	}
	return m
}

// counterFlag is a flag.Value that is like a flag.Bool and a flag.Int.
// If used as -name, it increments the counterFlag, but -name=x sets the counterFlag.
// Used for verbose flag -v and build-all flag -a
type counterFlag int

func (c *counterFlag) String() string {
	return fmt.Sprint(int(*c))
}

func (c *counterFlag) Set(s string) error {
	switch s {
	case "true":
		*c++
	case "false":
		*c = 0
	default:
		n, err := strconv.Atoi(s)
		if err != nil {
			return fmt.Errorf("invalid count %q", s)
		}
		*c = counterFlag(n)
	}
	return nil
}

func (c *counterFlag) IsBoolFlag() bool {
	return true
}