refactor: move defaulting logic to config package (#1731)

As we add more commands this defaulting will need to take place for more
of them. In order to better facilitate this I upstreamed some of this
logic we we can just rely on the config being defaulted by the time it
reaching the command execution code.

Updates: #1009

Author: codyoss

internal/cli/cli.go

@@ -110,7 +110,7 @@ func (c *Command) Init() *Command {
 	c.Flags.Usage = func() {
 		c.usage(c.Flags.Output())
 	}
-	c.Config = config.New()
+	c.Config = config.New(c.Name())
 	return c
 }
 

internal/config/config.go

@@ -18,10 +18,13 @@ package config
 import (
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/user"
+	"path/filepath"
 	"regexp"
 	"strings"
+	"time"
 )
 
 const (
@@ -48,6 +51,16 @@ const (
 	LibrarianDir = ".librarian"
 	// ReleaseInitRequest is a JSON file that describes which library to release.
 	ReleaseInitRequest = "release-init-request.json"
+
+	pipelineStateFile = "state.yaml"
+	versionCmdName    = "version"
+)
+
+// are variables so it can be replaced during testing.
+var (
+	now         = time.Now
+	tempDir     = os.TempDir
+	currentUser = user.Current
 )
 
 var (
@@ -201,22 +214,26 @@ type Config struct {
 	//
 	// WorkRoot is used by all librarian commands.
 	WorkRoot string
+
+	// commandName is the name of the command being executed.
+	//
+	// commandName is populated automatically after flag parsing. No user setup is
+	// expected.
+	commandName string
 }
 
 // New returns a new Config populated with environment variables.
-func New() *Config {
+func New(cmdName string) *Config {
 	return &Config{
+		commandName: cmdName,
 		GitHubToken: os.Getenv("LIBRARIAN_GITHUB_TOKEN"),
 	}
 }
 
-// currentUser is a variable, so it can be replaced during testing.
-var currentUser = user.Current
-
-// SetupUser performs late initialization of user-specific configuration,
+// setupUser performs late initialization of user-specific configuration,
 // determining the current user. This is in a separate method as it
 // can fail, and is called after flag parsing.
-func (c *Config) SetupUser() error {
+func (c *Config) setupUser() error {
 	user, err := currentUser()
 	if err != nil {
 		return fmt.Errorf("failed to get current user: %w", err)
@@ -226,6 +243,55 @@ func (c *Config) SetupUser() error {
 	return nil
 }
 
+func (c *Config) createWorkRoot() error {
+	if c.commandName == versionCmdName {
+		return nil
+	}
+	if c.WorkRoot != "" {
+		slog.Info("Using specified working directory", "dir", c.WorkRoot)
+		return nil
+	}
+	t := now()
+	path := filepath.Join(tempDir(), fmt.Sprintf("librarian-%s", formatTimestamp(t)))
+
+	_, err := os.Stat(path)
+	switch {
+	case os.IsNotExist(err):
+		if err := os.Mkdir(path, 0755); err != nil {
+			return fmt.Errorf("unable to create temporary working directory '%s': %w", path, err)
+		}
+	case err == nil:
+		return fmt.Errorf("temporary working directory already exists: %s", path)
+	default:
+		return fmt.Errorf("unable to check directory '%s': %w", path, err)
+	}
+
+	slog.Info("Temporary working directory", "dir", path)
+	c.WorkRoot = path
+	return nil
+}
+
+func (c *Config) deriveRepo() error {
+	if c.commandName == versionCmdName {
+		return nil
+	}
+	if c.Repo != "" {
+		slog.Debug("repo value provided by user", "repo", c.Repo)
+		return nil
+	}
+	wd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("getting working directory: %w", err)
+	}
+	stateFile := filepath.Join(wd, LibrarianDir, pipelineStateFile)
+	if _, err := os.Stat(stateFile); err != nil {
+		return fmt.Errorf("repo flag not specified and no state file found in current working directory: %w", err)
+	}
+	slog.Info("repo not specified, using current working directory as repo root", "path", wd)
+	c.Repo = wd
+	return nil
+}
+
 // IsValid ensures the values contained in a Config are valid.
 func (c *Config) IsValid() (bool, error) {
 	if c.Push && c.GitHubToken == "" {
@@ -247,9 +313,27 @@ func (c *Config) IsValid() (bool, error) {
 		return false, err
 	}
 
+	if c.commandName != versionCmdName && c.Repo == "" {
+		return false, errors.New("language repository not specified or detected")
+	}
+
 	return true, nil
 }
 
+// SetDefaults initializes values not set directly by the user.
+func (c *Config) SetDefaults() error {
+	if err := c.setupUser(); err != nil {
+		return err
+	}
+	if err := c.createWorkRoot(); err != nil {
+		return err
+	}
+	if err := c.deriveRepo(); err != nil {
+		return err
+	}
+	return nil
+}
+
 func validateHostMount(hostMount, defaultValue string) (bool, error) {
 	if hostMount == defaultValue {
 		return true, nil
@@ -262,3 +346,8 @@ func validateHostMount(hostMount, defaultValue string) (bool, error) {
 
 	return true, nil
 }
+
+func formatTimestamp(t time.Time) string {
+	const yyyyMMddHHmmss = "20060102T150405Z" // Expected format by time library
+	return t.Format(yyyyMMddHHmmss)
+}