// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

package cli

import (
	"context"
	"flag"
	"fmt"
	"os"
	"time"

	"github.com/peterbourgon/ff/v3/ffcli"
	"tailscale.com/ipn"
)

var switchCmd = &ffcli.Command{
	Name:      "switch",
	ShortHelp: "Switches to a different Tailscale account",
	FlagSet: func() *flag.FlagSet {
		fs := flag.NewFlagSet("switch", flag.ExitOnError)
		fs.BoolVar(&switchArgs.list, "list", false, "list available accounts")
		return fs
	}(),
	Exec: switchProfile,
	UsageFunc: func(*ffcli.Command) string {
		return `USAGE
  switch <name>
  switch --list

"tailscale switch" switches between logged in accounts.
This command is currently in alpha and may change in the future.`
	},
}

var switchArgs struct {
	list bool
}

func listProfiles(ctx context.Context) error {
	curP, all, err := localClient.ProfileStatus(ctx)
	if err != nil {
		return err
	}
	for _, prof := range all {
		if prof.ID == curP.ID {
			fmt.Printf("%s *\n", prof.Name)
		} else {
			fmt.Println(prof.Name)
		}
	}
	return nil
}

func switchProfile(ctx context.Context, args []string) error {
	if switchArgs.list {
		return listProfiles(ctx)
	}
	if len(args) != 1 {
		outln("usage: tailscale switch NAME")
		os.Exit(1)
	}
	cp, all, err := localClient.ProfileStatus(ctx)
	if err != nil {
		errf("Failed to switch to account: %v\n", err)
		os.Exit(1)
	}
	var profID ipn.ProfileID
	for _, p := range all {
		if p.Name == args[0] {
			profID = p.ID
			break
		}
	}
	if profID == "" {
		errf("No profile named %q\n", args[0])
		os.Exit(1)
	}
	if profID == cp.ID {
		printf("Already on account %q\n", args[0])
		os.Exit(0)
	}
	if err := localClient.SwitchProfile(ctx, profID); err != nil {
		errf("Failed to switch to account: %v\n", err)
		os.Exit(1)
	}
	printf("Switching to account %q\n", args[0])
	for {
		select {
		case <-ctx.Done():
			errf("Timed out waiting for switch to complete.")
			os.Exit(1)
		default:
		}
		st, err := localClient.StatusWithoutPeers(ctx)
		if err != nil {
			errf("Error getting status: %v", err)
			os.Exit(1)
		}
		switch st.BackendState {
		case "NoState", "Starting":
			// TODO(maisem): maybe add a way to subscribe to state changes to
			// LocalClient.
			time.Sleep(100 * time.Millisecond)
			continue
		case "NeedsLogin":
			outln("Logged out.")
			outln("To log in, run:")
			outln("  tailscale up")
			return nil
		case "Running":
			outln("Success.")
			return nil
		}
		// For all other states, use the default error message.
		if msg, ok := isRunningOrStarting(st); !ok {
			outln(msg)
			os.Exit(1)
		}
	}
}