browser/platform/service/distribution_builder.go

package service

import (
	"archive/tar"
	"bufio"
	"bytes"
	"context"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"browser.local/platform/domain"
)

// DistributionBuilder executes a distribution build inside a platform-owned
// container. Builds are a platform responsibility: they must not depend on a
// machine-side run endpoint being registered and online, and the component auth
// key must never leave the platform.
type DistributionBuilder interface {
	// Readiness reports whether the platform builder can execute a build. The
	// reason must name the platform builder rather than a run endpoint
	// capability, so an operator is not sent looking at the wrong subsystem.
	Readiness() (bool, string)
	// Build assembles the package described by input and returns its bytes.
	Build(input domain.DistributionBuildInput) ([]byte, error)
}

type DistributionBuildProgress struct {
	Percent int
	Message string
}

type distributionBuilderWithProgress interface {
	BuildWithProgress(input domain.DistributionBuildInput, progress func(DistributionBuildProgress)) ([]byte, error)
}

// DockerDistributionBuilderConfig configures a container-per-build builder.
type DockerDistributionBuilderConfig struct {
	DockerBinary        string
	Image               string
	SourceDir           string
	SourceRepositoryURL string
	SourceRevision      string
	WorkspaceDir        string
	CacheDir            string
	Timeout             time.Duration
	PlatformURL         string
	CommandRunner       func(ctx context.Context, name string, args ...string) ([]byte, error)
	CommandStream       func(ctx context.Context, name string, args []string, onLine func(string)) ([]byte, error)
	GitCommandRunner    func(ctx context.Context, name string, args ...string) ([]byte, error)
}

// DockerDistributionBuilder runs each build in a container from a pinned image,
// with the run source mounted read-only and a per-job output directory mounted
// writable.
type DockerDistributionBuilder struct {
	config   DockerDistributionBuilderConfig
	sourceMu sync.Mutex
}

func NewDockerDistributionBuilder(config DockerDistributionBuilderConfig) *DockerDistributionBuilder {
	customRunner := config.CommandRunner != nil
	if strings.TrimSpace(config.DockerBinary) == "" {
		config.DockerBinary = "docker"
	}
	if config.Timeout <= 0 {
		config.Timeout = 30 * time.Minute
	}
	if config.CommandRunner == nil {
		config.CommandRunner = runCommandCombined
	}
	if config.GitCommandRunner == nil {
		config.GitCommandRunner = runCommandCombined
	}
	if config.CommandStream == nil && !customRunner {
		config.CommandStream = runCommandStreamCombined
	}
	return &DockerDistributionBuilder{config: config}
}

func runCommandCombined(ctx context.Context, name string, args ...string) ([]byte, error) {
	return exec.CommandContext(ctx, name, args...).CombinedOutput()
}

func runCommandStreamCombined(ctx context.Context, name string, args []string, onLine func(string)) ([]byte, error) {
	cmd := exec.CommandContext(ctx, name, args...)
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	stderr, err := cmd.StderrPipe()
	if err != nil {
		return nil, err
	}
	if err := cmd.Start(); err != nil {
		return nil, err
	}

	var mu sync.Mutex
	var output bytes.Buffer
	var wg sync.WaitGroup
	capture := func(reader io.Reader) {
		defer wg.Done()
		scanner := bufio.NewScanner(reader)
		scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
		for scanner.Scan() {
			line := scanner.Text()
			mu.Lock()
			output.WriteString(line)
			output.WriteByte('\n')
			mu.Unlock()
			if onLine != nil {
				onLine(line)
			}
		}
	}
	wg.Add(2)
	go capture(stdout)
	go capture(stderr)
	err = cmd.Wait()
	wg.Wait()
	return output.Bytes(), err
}

func (builder *DockerDistributionBuilder) Readiness() (bool, string) {
	if strings.TrimSpace(builder.config.Image) == "" {
		return false, "platform builder image is not configured"
	}
	if !pinnedBuilderImage(builder.config.Image) {
		return false, "platform builder image must be pinned to an explicit version or digest"
	}
	source := strings.TrimSpace(builder.config.SourceDir)
	if source == "" {
		return false, "platform builder run source directory is not configured"
	}
	source, err := filepath.Abs(strings.TrimSpace(builder.config.SourceDir))
	if err != nil {
		return false, "platform builder run source directory is invalid"
	}
	if _, err := os.Stat(source); err != nil && !errors.Is(err, os.ErrNotExist) {
		return false, "platform builder run source directory is not accessible"
	}
	if strings.TrimSpace(builder.config.SourceRepositoryURL) == "" {
		if _, err := os.Stat(filepath.Join(source, "go.mod")); err != nil {
			return false, "platform builder run source repository is not configured"
		}
	}
	if strings.TrimSpace(builder.config.WorkspaceDir) == "" {
		return false, "platform builder workspace directory is not configured"
	}
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if _, err := builder.config.CommandRunner(ctx, builder.config.DockerBinary, "version", "--format", "{{.Server.Version}}"); err != nil {
		return false, "platform builder container runtime is unavailable"
	}
	if _, err := builder.config.CommandRunner(ctx, builder.config.DockerBinary, "image", "inspect", builder.config.Image); err != nil {
		return false, "platform builder image is unavailable"
	}
	return true, ""
}

// pinnedBuilderImage rejects floating references. An unpinned builder image
// silently changes what the platform ships.
func pinnedBuilderImage(image string) bool {
	image = strings.TrimSpace(image)
	if name, digest, found := strings.Cut(image, "@sha256:"); found {
		if strings.TrimSpace(name) == "" || len(digest) != 64 {
			return false
		}
		_, err := hex.DecodeString(digest)
		return err == nil
	}
	reference := image
	if slash := strings.LastIndex(image, "/"); slash >= 0 {
		reference = image[slash+1:]
	}
	_, tag, found := strings.Cut(reference, ":")
	if !found {
		return false
	}
	tag = strings.TrimSpace(tag)
	return tag != "" && tag != "latest"
}

func (builder *DockerDistributionBuilder) Build(input domain.DistributionBuildInput) ([]byte, error) {
	return builder.BuildWithProgress(input, nil)
}

func (builder *DockerDistributionBuilder) BuildWithProgress(input domain.DistributionBuildInput, progress func(DistributionBuildProgress)) ([]byte, error) {
	if ready, reason := builder.Readiness(); !ready {
		return nil, validationError(reason)
	}
	reportBuilderProgress(progress, 8, "env_check: platform builder readiness verified")
	sourceDir, err := filepath.Abs(strings.TrimSpace(builder.config.SourceDir))
	if err != nil {
		return nil, validationError("platform builder run source directory is invalid")
	}
	workspaceDir, err := filepath.Abs(strings.TrimSpace(builder.config.WorkspaceDir))
	if err != nil {
		return nil, validationError("platform builder workspace directory is invalid")
	}
	ctx, cancel := context.WithTimeout(context.Background(), builder.config.Timeout)
	defer cancel()
	if input.ComponentKind == domain.DistributionComponentRun {
		// Keep a shared checkout stable while Docker reads it. The checkout is
		// refreshed and exported below for this build, rather than captured when
		// the platform process starts.
		builder.sourceMu.Lock()
		defer builder.sourceMu.Unlock()
	}
	cacheDir, err := builder.cacheDir(workspaceDir)
	if err != nil {
		return nil, validationError("platform builder cache directory is invalid")
	}
	// Workspaces stay isolated per plugin and per job as required by
	// run-build-download-flow.
	jobDir := filepath.Join(workspaceDir, sanitizeIDPart(input.PluginID), sanitizeIDPart(input.JobID))
	if err := os.RemoveAll(jobDir); err != nil {
		return nil, err
	}
	outputDir := filepath.Join(jobDir, "output")
	inputDir := filepath.Join(jobDir, "input")
	buildDir := filepath.Join(jobDir, "build")
	sourceMountDir := filepath.Join(jobDir, "source")
	goBuildCacheDir := filepath.Join(cacheDir, "go-build")
	goModCacheDir := filepath.Join(cacheDir, "go-mod")
	for _, directory := range []string{outputDir, inputDir, buildDir, sourceMountDir, goBuildCacheDir, goModCacheDir} {
		if err := os.MkdirAll(directory, 0o700); err != nil {
			return nil, err
		}
	}
	defer func() { _ = os.RemoveAll(jobDir) }()
	reportBuilderProgress(progress, 14, "env_check: platform builder workspace prepared")
	if input.ComponentKind == domain.DistributionComponentRun {
		preparedSourceDir, err := builder.prepareRunSource(ctx, sourceDir, sourceMountDir, input, progress)
		if err != nil {
			return nil, err
		}
		sourceMountDir = preparedSourceDir
	}

	// The auth key reaches the container through a per-job input file, never
	// through a job-channel response to a machine-side endpoint or a container
	// command-line argument.
	if strings.TrimSpace(input.AuthKey) == "" {
		return nil, validationError("distribution build input is missing a component auth key")
	}
	if err := os.WriteFile(filepath.Join(inputDir, "auth-key"), []byte(input.AuthKey), 0o600); err != nil {
		return nil, err
	}
	seedPayload := []byte("[]")
	if strings.TrimSpace(input.WorkspaceSeed) != "" {
		decoded, err := base64.StdEncoding.DecodeString(input.WorkspaceSeed)
		if err != nil {
			return nil, validationError("distribution build input has an invalid workspace seed")
		}
		seedPayload = decoded
	}
	if err := os.WriteFile(filepath.Join(inputDir, "workspace-seed.json"), seedPayload, 0o600); err != nil {
		return nil, err
	}
	lifecyclePlanPayload := []byte("{}")
	if input.AutonomousLifecycle != nil {
		encoded, err := json.Marshal(input.AutonomousLifecycle)
		if err != nil {
			return nil, validationError("distribution build input has an invalid autonomous lifecycle plan")
		}
		lifecyclePlanPayload = encoded
	}
	if err := os.WriteFile(filepath.Join(inputDir, "autonomous-lifecycle-plan.json"), lifecyclePlanPayload, 0o600); err != nil {
		return nil, err
	}
	if err := os.WriteFile(filepath.Join(inputDir, "build.sh"), []byte(distributionBuildScript), 0o500); err != nil {
		return nil, err
	}

	outputName := strings.TrimSpace(input.OutputFilename)
	if outputName == "" || filepath.Base(outputName) != outputName {
		return nil, validationError("distribution build input has an invalid output filename")
	}
	args := builder.containerArgs(input, sourceMountDir, inputDir, buildDir, outputDir, goBuildCacheDir, goModCacheDir, outputName)
	reportBuilderProgress(progress, 18, "git_sync: platform builder container starting")
	output, err := builder.runBuildCommand(ctx, args, progress)
	if err != nil {
		if errors.Is(ctx.Err(), context.DeadlineExceeded) {
			return nil, validationError("platform builder timed out while building the distribution")
		}
		return nil, validationError("platform builder failed: " + safeBuilderFailureWithCommandError(output, err, input.AuthKey, builder.config.SourceDir, sourceDir, jobDir))
	}
	reportBuilderProgress(progress, 92, "package_finalize: reading platform builder output")
	binary, err := os.ReadFile(filepath.Join(outputDir, outputName))
	if err != nil {
		return nil, validationError("platform builder did not produce a distribution executable")
	}
	if len(binary) == 0 {
		return nil, validationError("platform builder produced an empty distribution executable")
	}
	return binary, nil
}

// prepareRunSource implements the source phase of a Jenkins-style build. A
// configured checkout is created when absent, fetched on every build, and
// exported at FETCH_HEAD into the per-job workspace. The archive keeps local
// uncommitted files and the checkout's .git directory out of the executable.
func (builder *DockerDistributionBuilder) prepareRunSource(ctx context.Context, sourceDir, destination string, input domain.DistributionBuildInput, progress func(DistributionBuildProgress)) (string, error) {
	repository := strings.TrimSpace(input.RepositoryURL)
	if repository == "" {
		repository = strings.TrimSpace(builder.config.SourceRepositoryURL)
	}
	revision := strings.TrimSpace(input.SourceRevision)
	if revision == "" {
		revision = strings.TrimSpace(builder.config.SourceRevision)
	}
	if revision == "" {
		revision = "main"
	}

	if _, err := os.Stat(filepath.Join(sourceDir, ".git")); errors.Is(err, os.ErrNotExist) {
		if repository == "" {
			if _, sourceErr := os.Stat(filepath.Join(sourceDir, "go.mod")); sourceErr != nil {
				return "", validationError("platform builder has no Run source checkout or repository")
			}
			return sourceDir, nil
		}
		if err := os.MkdirAll(filepath.Dir(sourceDir), 0o700); err != nil {
			return "", validationError("platform builder could not create the Run source parent")
		}
		reportBuilderProgress(progress, 20, "git_sync: creating Run source checkout")
		if _, err := builder.config.GitCommandRunner(ctx, "git", "clone", "--no-checkout", repository, sourceDir); err != nil {
			return "", validationError("platform builder could not clone the Run source")
		}
	} else if err != nil {
		return "", validationError("platform builder could not inspect the Run source checkout")
	}

	reportBuilderProgress(progress, 26, "git_sync: fetching Run source revision")
	if _, err := builder.config.GitCommandRunner(ctx, "git", "-C", sourceDir, "fetch", "--depth", "1", "origin", revision); err != nil {
		return "", validationError("platform builder could not update the Run source revision")
	}
	archivePayload, err := builder.config.GitCommandRunner(ctx, "git", "-C", sourceDir, "archive", "--format=tar", "FETCH_HEAD")
	if err != nil {
		return "", validationError("platform builder could not export the Run source revision")
	}
	if err := extractRunSourceArchive(archivePayload, destination); err != nil {
		return "", validationError("platform builder could not prepare the Run source workspace")
	}
	reportBuilderProgress(progress, 34, "git_sync: Run source revision prepared")
	return destination, nil
}

func extractRunSourceArchive(payload []byte, destination string) error {
	reader := tar.NewReader(bytes.NewReader(payload))
	for {
		header, err := reader.Next()
		if errors.Is(err, io.EOF) {
			return nil
		}
		if err != nil {
			return err
		}
		name := filepath.Clean(filepath.FromSlash(header.Name))
		if name == "." || filepath.IsAbs(name) || name == ".." || strings.HasPrefix(name, ".."+string(os.PathSeparator)) {
			return errors.New("Run source archive contains an unsafe path")
		}
		target := filepath.Join(destination, name)
		if header.FileInfo().IsDir() {
			if err := os.MkdirAll(target, header.FileInfo().Mode().Perm()); err != nil {
				return err
			}
			continue
		}
		if !header.FileInfo().Mode().IsRegular() {
			return errors.New("Run source archive contains an unsupported file")
		}
		if err := os.MkdirAll(filepath.Dir(target), 0o700); err != nil {
			return err
		}
		file, err := os.OpenFile(target, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, header.FileInfo().Mode().Perm())
		if err != nil {
			return err
		}
		_, copyErr := io.Copy(file, reader)
		closeErr := file.Close()
		if copyErr != nil {
			return copyErr
		}
		if closeErr != nil {
			return closeErr
		}
	}
}

func (builder *DockerDistributionBuilder) cacheDir(workspaceDir string) (string, error) {
	configured := strings.TrimSpace(builder.config.CacheDir)
	if configured == "" {
		configured = filepath.Join(workspaceDir, "_cache")
	}
	return filepath.Abs(configured)
}

func (builder *DockerDistributionBuilder) runBuildCommand(ctx context.Context, args []string, progress func(DistributionBuildProgress)) ([]byte, error) {
	if builder.config.CommandStream == nil {
		return builder.config.CommandRunner(ctx, builder.config.DockerBinary, args...)
	}
	return builder.config.CommandStream(ctx, builder.config.DockerBinary, args, func(line string) {
		parsed, ok := parseBuilderProgressLine(line)
		if ok {
			reportBuilderProgress(progress, parsed.Percent, parsed.Message)
		}
	})
}

const builderProgressMarker = "__platform_builder_progress__|"

func parseBuilderProgressLine(line string) (DistributionBuildProgress, bool) {
	line = strings.TrimSpace(line)
	if !strings.HasPrefix(line, builderProgressMarker) {
		return DistributionBuildProgress{}, false
	}
	rest := strings.TrimPrefix(line, builderProgressMarker)
	parts := strings.SplitN(rest, "|", 2)
	if len(parts) != 2 {
		return DistributionBuildProgress{}, false
	}
	percent, err := strconv.Atoi(strings.TrimSpace(parts[0]))
	if err != nil {
		return DistributionBuildProgress{}, false
	}
	message := strings.TrimSpace(parts[1])
	if message == "" {
		return DistributionBuildProgress{}, false
	}
	if percent < 1 {
		percent = 1
	}
	if percent > 99 {
		percent = 99
	}
	return DistributionBuildProgress{Percent: percent, Message: message}, true
}

func reportBuilderProgress(progress func(DistributionBuildProgress), percent int, message string) {
	if progress == nil {
		return
	}
	if percent < 1 {
		percent = 1
	}
	if percent > 99 {
		percent = 99
	}
	progress(DistributionBuildProgress{Percent: percent, Message: message})
}

const distributionBuildScript = `#!/bin/sh
set -eu

progress() {
  printf '__platform_builder_progress__|%s|%s\n' "$1" "$2"
}

auth_key="$(cat /workspace/input/auth-key)"
if [ "$COMPONENT_KIND" = "run" ]; then
  progress 24 'git_sync: preparing run source snapshot'
  rm -rf /workspace/build/run-source
  mkdir -p /workspace/build/run-source
  find /workspace/source -mindepth 1 -maxdepth 1 ! -name pax_global_header -exec cp -R {} /workspace/build/run-source/ \;
  run_command_dir="$(find /workspace/build/run-source -type d -path '*/cmd/run' -print -quit)"
  run_module_dir="${run_command_dir%/cmd/run}"
  if [ -z "$run_command_dir" ] || [ ! -f "$run_module_dir/go.mod" ]; then
    printf 'Run source snapshot must contain a Go module with cmd/run\n' >&2
    exit 2
  fi
  progress 34 'env_check: injecting run build metadata'
  seed_b64="$(base64 /workspace/input/workspace-seed.json | tr -d '\n')"
  mkdir -p "$run_module_dir/config"
  cat > "$run_module_dir/config/workspace_seed_generated.go" <<EOF
package config

func init() { BuildWorkspaceSeed = "$seed_b64" }
EOF
  cd "$run_module_dir"
  ldflags="-s -w"
  ldflags="$ldflags -X browser.local/run/config.BuildMode=worker"
  ldflags="$ldflags -X browser.local/run/config.BuildPlatformURL=$PLATFORM_URL"
  ldflags="$ldflags -X browser.local/run/config.BuildRunEndpointID=$RUN_ENDPOINT_ID"
  ldflags="$ldflags -X browser.local/run/config.BuildDisplayName=Run-$SERVER_INSTANCE_ID"
  ldflags="$ldflags -X browser.local/run/config.BuildRegistrationToken=$auth_key"
  ldflags="$ldflags -X browser.local/run/config.BuildServerInstanceID=$SERVER_INSTANCE_ID"
  ldflags="$ldflags -X browser.local/run/config.BuildPluginID=$PLUGIN_ID"
  ldflags="$ldflags -X browser.local/run/config.BuildComponentKind=$COMPONENT_KIND"
  ldflags="$ldflags -X browser.local/run/config.BuildComponentKey=$PROFILE_KEY"
  ldflags="$ldflags -X browser.local/run/config.BuildKeyGeneration=$KEY_GENERATION"
  ldflags="$ldflags -X browser.local/run/config.BuildVersion=$TARGET_RELEASE"
  progress 48 'build_compile: downloading Go modules'
  go mod download
  progress 72 'build_compile: compiling run target executable'
  go build -trimpath -ldflags "$ldflags" -o "/workspace/output/$OUTPUT_FILENAME" ./cmd/run
  progress 88 'package_finalize: run executable written'
  exit 0
fi

printf 'unsupported component kind\n' >&2
exit 2
`

func (builder *DockerDistributionBuilder) containerArgs(input domain.DistributionBuildInput, sourceDir string, inputDir string, buildDir string, outputDir string, goBuildCacheDir string, goModCacheDir string, outputName string) []string {
	platformURL := strings.TrimSpace(input.PlatformURL)
	if platformURL == "" {
		platformURL = strings.TrimSpace(builder.config.PlatformURL)
	}
	return []string{
		"run", "--rm",
		"--pull", "never",
		"--read-only",
		"--tmpfs", "/tmp:rw,nosuid,size=2147483648",
		"-v", sourceDir + ":/workspace/source:ro",
		"-v", inputDir + ":/workspace/input:ro",
		"-v", buildDir + ":/workspace/build",
		"-v", outputDir + ":/workspace/output",
		"-v", goBuildCacheDir + ":/workspace/cache/go-build",
		"-v", goModCacheDir + ":/workspace/cache/go-mod",
		"-e", "CGO_ENABLED=0",
		"-e", "GOOS=" + input.TargetOS,
		"-e", "GOARCH=" + input.TargetArch,
		"-e", "GOCACHE=/workspace/cache/go-build",
		"-e", "GOMODCACHE=/workspace/cache/go-mod",
		"-e", "COMPONENT_KIND=" + string(input.ComponentKind),
		"-e", "SERVER_INSTANCE_ID=" + input.ServerInstanceID,
		"-e", "PLUGIN_ID=" + input.PluginID,
		"-e", "RUN_ENDPOINT_ID=" + input.RunEndpointID,
		"-e", "PROFILE_KEY=" + input.ProfileKey,
		"-e", "TARGET_RELEASE=" + input.TargetRelease,
		"-e", "KEY_GENERATION=" + fmt.Sprint(input.KeyGeneration),
		"-e", "PLATFORM_URL=" + platformURL,
		"-e", "REPOSITORY_URL=" + input.RepositoryURL,
		"-e", "SOURCE_REVISION=" + input.SourceRevision,
		"-e", "OUTPUT_FILENAME=" + outputName,
		builder.config.Image,
		"/workspace/input/build.sh",
	}
}

// safeBuilderFailure keeps host paths and secret values out of reported build
// failures.
func safeBuilderFailure(output []byte, sensitiveValues ...string) string {
	text := strings.TrimSpace(string(output))
	for _, sensitive := range sensitiveValues {
		if strings.TrimSpace(sensitive) != "" {
			text = strings.ReplaceAll(text, sensitive, "[redacted]")
		}
	}
	if text == "" {
		return "build command reported no diagnostic output"
	}
	lines := strings.Split(text, "\n")
	kept := make([]string, 0, len(lines))
	for index := len(lines) - 1; index >= 0 && len(kept) < 3; index-- {
		line := strings.TrimSpace(lines[index])
		if line == "" || strings.HasPrefix(line, builderProgressMarker) || strings.Contains(line, "/workspace/input") || strings.Contains(line, "auth-key") {
			continue
		}
		line = redactBuilderHostPaths(line)
		kept = append([]string{line}, kept...)
	}
	if len(kept) == 0 {
		return "build command reported no shareable diagnostic output"
	}
	joined := strings.Join(kept, "; ")
	if len(joined) > 400 {
		joined = joined[:400]
	}
	return joined
}

func safeBuilderFailureWithCommandError(output []byte, commandErr error, sensitiveValues ...string) string {
	message := safeBuilderFailure(output, sensitiveValues...)
	if commandErr == nil || !strings.HasPrefix(message, "build command reported no ") {
		return message
	}
	return safeBuilderFailure([]byte(commandErr.Error()), sensitiveValues...)
}

func redactBuilderHostPaths(line string) string {
	fields := strings.Fields(line)
	for index, field := range fields {
		trimmed := strings.TrimLeft(field, "(\"'[")
		if strings.HasPrefix(trimmed, "/") && !strings.HasPrefix(trimmed, "/workspace/") {
			fields[index] = "[redacted-path]"
		}
	}
	return strings.Join(fields, " ")
}

func builderJobFailureMessage(err error, sensitiveValues ...string) string {
	if err == nil {
		return "platform builder failed"
	}
	message := safeBuilderFailure([]byte(err.Error()), sensitiveValues...)
	if message == "" {
		return "platform builder failed"
	}
	if len(message) > 400 {
		message = message[:400]
	}
	return message
}