package command

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"sort"
	"strings"

	"github.com/hashicorp/vault/api"
	"github.com/hashicorp/vault/helper/kv-builder"
	"github.com/hashicorp/vault/helper/password"
	"github.com/hashicorp/vault/meta"
	"github.com/mitchellh/mapstructure"
	"github.com/ryanuber/columnize"
)

// AuthHandler is the interface that any auth handlers must implement
// to enable auth via the CLI.
type AuthHandler interface {
	Auth(*api.Client, map[string]string) (string, error)
	Help() string
}

// AuthCommand is a Command that handles authentication.
type AuthCommand struct {
	meta.Meta

	Handlers map[string]AuthHandler

	// The fields below can be overwritten for tests
	testStdin io.Reader
}

func (c *AuthCommand) Run(args []string) int {
	var method string
	var methods, methodHelp, noVerify bool
	flags := c.Meta.FlagSet("auth", meta.FlagSetDefault)
	flags.BoolVar(&methods, "methods", false, "")
	flags.BoolVar(&methodHelp, "method-help", false, "")
	flags.BoolVar(&noVerify, "no-verify", false, "")
	flags.StringVar(&method, "method", "", "method")
	flags.Usage = func() { c.Ui.Error(c.Help()) }
	if err := flags.Parse(args); err != nil {
		return 1
	}

	if methods {
		return c.listMethods()
	}

	args = flags.Args()

	tokenHelper, err := c.TokenHelper()
	if err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error initializing token helper: %s\n\n"+
				"Please verify that the token helper is available and properly\n"+
				"configured for your system. Please refer to the documentation\n"+
				"on token helpers for more information.",
			err))
		return 1
	}

	// token is where the final token will go
	handler := c.Handlers[method]

	// Read token from stdin if first arg is exactly "-"
	var stdin io.Reader = os.Stdin
	if c.testStdin != nil {
		stdin = c.testStdin
	}

	if len(args) > 0 && args[0] == "-" {
		stdinR := bufio.NewReader(stdin)
		args[0], err = stdinR.ReadString('\n')
		if err != nil && err != io.EOF {
			c.Ui.Error(fmt.Sprintf("Error reading from stdin: %s", err))
			return 1
		}
		args[0] = strings.TrimSpace(args[0])
	}

	if method == "" {
		token := ""
		if len(args) > 0 {
			token = args[0]
		}

		handler = &tokenAuthHandler{Token: token}
		args = nil
	}

	if handler == nil {
		methods := make([]string, 0, len(c.Handlers))
		for k := range c.Handlers {
			methods = append(methods, k)
		}
		sort.Strings(methods)

		c.Ui.Error(fmt.Sprintf(
			"Unknown authentication method: %s\n\n"+
				"Please use a supported authentication method. The list of supported\n"+
				"authentication methods is shown below. Note that this list may not\n"+
				"be exhaustive: Vault may support other auth methods. For auth methods\n"+
				"unsupported by the CLI, please use the HTTP API.\n\n"+
				"%s",
			method,
			strings.Join(methods, ", ")))
		return 1
	}

	if methodHelp {
		c.Ui.Output(handler.Help())
		return 0
	}

	// Warn if the VAULT_TOKEN environment variable is set, as that will take
	// precedence
	if os.Getenv("VAULT_TOKEN") != "" {
		c.Ui.Output("==> WARNING: VAULT_TOKEN environment variable set!\n")
		c.Ui.Output("  The environment variable takes precedence over the value")
		c.Ui.Output("  set by the auth command. Either update the value of the")
		c.Ui.Output("  environment variable or unset it to use the new token.\n")
	}

	var vars map[string]string
	if len(args) > 0 {
		builder := kvbuilder.Builder{Stdin: os.Stdin}
		if err := builder.Add(args...); err != nil {
			c.Ui.Error(err.Error())
			return 1
		}

		if err := mapstructure.Decode(builder.Map(), &vars); err != nil {
			c.Ui.Error(fmt.Sprintf("Error parsing options: %s", err))
			return 1
		}
	}

	// Build the client so we can auth
	client, err := c.Client()
	if err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error initializing client to auth: %s", err))
		return 1
	}

	// Authenticate
	token, err := handler.Auth(client, vars)
	if err != nil {
		c.Ui.Error(err.Error())
		return 1
	}

	// Cache the previous token so that it can be restored if authentication fails
	var previousToken string
	if previousToken, err = tokenHelper.Get(); err != nil {
		c.Ui.Error(fmt.Sprintf("Error caching the previous token: %s\n\n", err))
		return 1
	}

	// Store the token!
	if err := tokenHelper.Store(token); err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error storing token: %s\n\n"+
				"Authentication was not successful and did not persist.\n"+
				"Please reauthenticate, or fix the issue above if possible.",
			err))
		return 1
	}

	if noVerify {
		c.Ui.Output(fmt.Sprintf(
			"Authenticated - no token verification has been performed.",
		))

		return 0
	}

	// Build the client again so it can read the token we just wrote
	client, err = c.Client()
	if err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error initializing client to verify the token: %s", err))
		if err := tokenHelper.Store(previousToken); err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error restoring the previous token: %s\n\n"+
					"Please reauthenticate with a valid token.",
				err))
		}
		return 1
	}

	// Verify the token
	secret, err := client.Auth().Token().LookupSelf()
	if err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error validating token: %s", err))
		if err := tokenHelper.Store(previousToken); err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error restoring the previous token: %s\n\n"+
					"Please reauthenticate with a valid token.",
				err))
		}
		return 1
	}
	if secret == nil {
		c.Ui.Error(fmt.Sprintf("Error: Invalid token"))
		if err := tokenHelper.Store(previousToken); err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error restoring the previous token: %s\n\n"+
					"Please reauthenticate with a valid token.",
				err))
		}
		return 1
	}

	// Get the policies we have
	policiesRaw, ok := secret.Data["policies"]
	if !ok {
		policiesRaw = []string{"unknown"}
	}
	var policies []string
	for _, v := range policiesRaw.([]interface{}) {
		policies = append(policies, v.(string))
	}

	output := "Successfully authenticated!"
	output += fmt.Sprintf("\ntoken: %s", secret.Data["id"])
	output += fmt.Sprintf("\ntoken_duration: %d", int(secret.Data["ttl"].(float64)))
	if len(policies) > 0 {
		output += fmt.Sprintf("\ntoken_policies: [%s]", strings.Join(policies, ", "))
	}

	c.Ui.Output(output)

	return 0

}

func (c *AuthCommand) listMethods() int {
	client, err := c.Client()
	if err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error initializing client: %s", err))
		return 1
	}

	auth, err := client.Sys().ListAuth()
	if err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error reading auth table: %s", err))
		return 1
	}

	paths := make([]string, 0, len(auth))
	for path := range auth {
		paths = append(paths, path)
	}
	sort.Strings(paths)

	columns := []string{"Path | Type | Description"}
	for _, k := range paths {
		a := auth[k]
		columns = append(columns, fmt.Sprintf(
			"%s | %s | %s", k, a.Type, a.Description))
	}

	c.Ui.Output(columnize.SimpleFormat(columns))
	return 0
}

func (c *AuthCommand) Synopsis() string {
	return "Prints information about how to authenticate with Vault"
}

func (c *AuthCommand) Help() string {
	helpText := `
Usage: vault auth [options] [token or config...]

  Authenticate with Vault with the given token or via any supported
  authentication backend.

  If no -method is specified, then the token is expected. If it is not
  given on the command-line, it will be asked via user input. If the
  token is "-", it will be read from stdin.

  By specifying -method, alternate authentication methods can be used
  such as OAuth or TLS certificates. For these, additional values for
  configuration can be specified with "key=value" pairs just like
  "vault write". Specify the "-method-help" flag to get help for a specific
  method.

  If you've mounted a credential backend to a different path, such
  as mounting "github" to "github-private", the "method" flag should
  still be "github." Most credential providers support the "mount" option
  to specify the mount point. See the "-method-help" for more info.

General Options:

  ` + meta.GeneralOptionsUsage() + `

Auth Options:

  -method=name      Outputs help for the authentication method with the given
                    name for the remote server. If this authentication method
                    is not available, exit with code 1.

  -method-help      If set, the help for the selected method will be shown.

  -methods          List the available auth methods.

  -no-verify        Do not verify the token after creation; avoids a use count
                    decrement.

`
	return strings.TrimSpace(helpText)
}

// tokenAuthHandler handles retrieving the token from the command-line.
type tokenAuthHandler struct {
	Token string
}

func (h *tokenAuthHandler) Auth(*api.Client, map[string]string) (string, error) {
	token := h.Token
	if token == "" {
		var err error

		// No arguments given, read the token from user input
		fmt.Printf("Token (will be hidden): ")
		token, err = password.Read(os.Stdin)
		fmt.Printf("\n")
		if err != nil {
			return "", fmt.Errorf(
				"Error attempting to ask for token. The raw error message\n"+
					"is shown below, but the most common reason for this error is\n"+
					"that you attempted to pipe a value into auth. If you want to\n"+
					"pipe the token, please pass '-' as the token argument.\n\n"+
					"Raw error: %s", err)
		}
	}

	if token == "" {
		return "", fmt.Errorf(
			"A token must be passed to auth. Please view the help\n" +
				"for more information.")
	}

	return token, nil
}

func (h *tokenAuthHandler) Help() string {
	help := `
No method selected with the "-method" flag, so the "auth" command assumes
you'll be using raw token authentication. For this, specify the token to
authenticate as as the parameter to "vault auth". Example:

    vault auth 123456

The token used to authenticate must come from some other source. A root
token is created when Vault is first initialized. After that, subsequent
tokens are created via the API or command line interface (with the
"token"-prefixed commands).
`

	return strings.TrimSpace(help)
}