github__gh-stack/cmd/switch.go

package cmd

import (
	"fmt"

	"github.com/cli/go-gh/v2/pkg/prompter"
	"github.com/github/gh-stack/internal/config"
	"github.com/github/gh-stack/internal/git"
	"github.com/spf13/cobra"
)

func SwitchCmd(cfg *config.Config) *cobra.Command {
	return &cobra.Command{
		Use:   "switch",
		Short: "Interactively switch to another branch in the stack",
		Long: `Show an interactive picker listing all branches in the current stack
and switch to the selected one.

Branches are displayed from top (furthest from trunk) to bottom (closest to
trunk) with their position number. Use the arrow keys to navigate and Enter
to select.

To move one branch up or down without an interactive picker, use
'gh stack up' or 'gh stack down' instead.`,
		Example: `  # Open the branch picker for the current stack
  $ gh stack switch`,
		Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			return runSwitch(cfg)
		},
	}
}

func runSwitch(cfg *config.Config) error {
	result, err := loadStack(cfg, "")
	if err != nil {
		return ErrNotInStack
	}
	s := result.Stack

	if len(s.Branches) == 0 {
		cfg.Errorf("stack has no branches")
		return ErrNotInStack
	}

	if !cfg.IsInteractive() {
		cfg.Errorf("switch requires an interactive terminal")
		return ErrSilent
	}

	// Build options in reverse order (top of stack first) with 1-based numbering.
	n := len(s.Branches)
	options := make([]string, n)
	currentBranch := result.CurrentBranch
	var defaultOpt string
	for i := 0; i < n; i++ {
		branchIdx := n - 1 - i
		options[i] = fmt.Sprintf("%d. %s", branchIdx+1, s.Branches[branchIdx].Branch)
		if s.Branches[branchIdx].Branch == currentBranch {
			defaultOpt = options[i]
		}
	}

	var selectFn func(prompt, def string, opts []string) (int, error)
	if cfg.SelectFn != nil {
		selectFn = cfg.SelectFn
	} else {
		p := prompter.New(cfg.In, cfg.Out, cfg.Err)
		selectFn = func(prompt, def string, opts []string) (int, error) {
			return p.Select(prompt, def, opts)
		}
	}

	selected, err := selectFn("Select a branch in the stack to switch to:", defaultOpt, options)
	if err != nil {
		if isInterruptError(err) {
			clearSelectPrompt(cfg, len(options))
			printInterrupt(cfg)
			return errInterrupt
		}
		cfg.Errorf("failed to select branch: %v", err)
		return ErrSilent
	}

	if selected < 0 || selected >= n {
		cfg.Errorf("invalid selection")
		return ErrSilent
	}

	// Map selection back: index 0 in options = branch at n-1, etc.
	branchIdx := n - 1 - selected
	targetBranch := s.Branches[branchIdx].Branch
	if targetBranch == currentBranch {
		cfg.Infof("Already on %s", targetBranch)
		return nil
	}

	if err := git.CheckoutBranch(targetBranch); err != nil {
		cfg.Errorf("failed to checkout %s: %v", targetBranch, err)
		return ErrSilent
	}

	cfg.Successf("Switched to %s", targetBranch)
	return nil
}