Add command for agent install (#695)

Author: mcncl

cmd/agent/install.go

@@ -0,0 +1,158 @@
+package agent
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"github.com/alecthomas/kong"
+	"github.com/buildkite/cli/v3/internal/cli"
+	"github.com/buildkite/cli/v3/pkg/cmd/factory"
+
+	bkAgent "github.com/buildkite/cli/v3/internal/agent"
+)
+
+var (
+	userArch = runtime.GOARCH
+	userOS   = runtime.GOOS
+)
+
+// InstallCmd allows users to define which agent version they want to install
+// We will take care of OS/arch in the command itself
+type InstallCmd struct {
+	Version    string `help:"Specify an agent version to install" default:"latest"`
+	Dest       string `help:"Destination directory for the binary" type:"path"`
+	Cluster    string `help:"Cluster UUID to create the agent token on (default: the \"Default\" cluster)" optional:""`
+	NoToken    bool   `help:"Skip creating an agent token and config file" name:"no-token"`
+	ConfigPath string `help:"Path to write the agent config file" type:"path"`
+}
+
+func (i *InstallCmd) Help() string {
+	return `Install the buildkite-agent binary locally.
+
+By default, this also creates an agent token on the Default cluster and writes
+a minimal config file so the agent is ready to start.
+
+Examples:
+  # Install the latest version of the agent
+  $ bk agent install
+
+  # Install a specific version
+  $ bk agent install --version "3.112.0"
+
+  # Install to a custom location
+  $ bk agent install --dest ~/.local/bin
+
+  # Install without creating a token/config
+  $ bk agent install --no-token
+`
+}
+
+func (i *InstallCmd) Run(kongCtx *kong.Context, globals cli.GlobalFlags) error {
+	dest := i.Dest
+	if dest == "" {
+		dest = bkAgent.DefaultBinDir(userOS)
+	}
+
+	// Check for existing installations in PATH
+	if existing := bkAgent.FindExisting(userOS); existing != nil {
+		destBinary := filepath.Join(dest, bkAgent.BinaryName(userOS))
+		if existing.Path != destBinary {
+			fmt.Printf("Warning: existing buildkite-agent found at %s", existing.Path)
+			if existing.Version != "" {
+				fmt.Printf(" (%s)", existing.Version)
+			}
+			fmt.Println()
+			fmt.Printf("  The new install at %s may be shadowed in your PATH.\n", destBinary)
+			fmt.Println()
+		}
+	}
+
+	if err := os.MkdirAll(dest, 0o755); err != nil {
+		return fmt.Errorf("creating destination directory: %w", err)
+	}
+
+	version := i.Version
+	if version == "latest" {
+		resolved, err := bkAgent.ResolveLatestVersion()
+		if err != nil {
+			return fmt.Errorf("resolving latest version: %w", err)
+		}
+		version = resolved
+	}
+
+	version = strings.TrimPrefix(version, "v")
+
+	downloadURL := bkAgent.BuildDownloadURL(version, userOS, userArch)
+	fmt.Printf("Downloading buildkite-agent v%s for %s/%s...\n", version, userOS, userArch)
+
+	tmpFile, err := bkAgent.DownloadToTemp(downloadURL)
+	if err != nil {
+		return fmt.Errorf("downloading agent: %w", err)
+	}
+	defer os.Remove(tmpFile)
+
+	// Verify the download checksum
+	fmt.Println("Verifying checksum...")
+	sumsURL := bkAgent.BuildSHA256SumsURL(version)
+	archiveFilename := filepath.Base(downloadURL)
+	expectedHash, err := bkAgent.FetchExpectedSHA256(sumsURL, archiveFilename)
+	if err != nil {
+		return fmt.Errorf("fetching checksum: %w", err)
+	}
+	if err := bkAgent.VerifySHA256(tmpFile, expectedHash); err != nil {
+		return fmt.Errorf("checksum verification failed: %w", err)
+	}
+
+	if err := bkAgent.ExtractBinary(tmpFile, dest, userOS); err != nil {
+		return fmt.Errorf("extracting agent: %w", err)
+	}
+
+	binaryName := bkAgent.BinaryName(userOS)
+	fmt.Printf("Installed buildkite-agent to %s\n", filepath.Join(dest, binaryName))
+
+	if !i.NoToken {
+		if err := i.createTokenAndConfig(globals); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (i *InstallCmd) createTokenAndConfig(globals cli.GlobalFlags) error {
+	f, err := factory.New(factory.WithDebug(globals.EnableDebug()))
+	if err != nil {
+		return fmt.Errorf("initializing API client: %w", err)
+	}
+
+	ctx := context.Background()
+	org := f.Config.OrganizationSlug()
+
+	clusterID, err := bkAgent.FindCluster(ctx, f, org, i.Cluster)
+	if err != nil {
+		return fmt.Errorf("finding default cluster: %w", err)
+	}
+
+	fmt.Println("Creating agent token...")
+	token, err := bkAgent.CreateAgentToken(ctx, f, org, clusterID, "Token created by bk agent install")
+	if err != nil {
+		return fmt.Errorf("creating agent token: %w", err)
+	}
+
+	configPath := i.ConfigPath
+	if configPath == "" {
+		configPath = bkAgent.DefaultConfigPath(userOS)
+	}
+
+	buildPath := bkAgent.DefaultBuildPath(userOS)
+	if err := bkAgent.WriteAgentConfig(configPath, token, buildPath); err != nil {
+		return fmt.Errorf("writing agent config: %w", err)
+	}
+
+	fmt.Printf("Agent config written to %s\n", configPath)
+	return nil
+}