package cli

import (
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"path/filepath"
	"slices"
	"strings"

	"github.com/awnumar/memguard"
	"github.com/spf13/afero"
	"github.com/spf13/cobra"
	"sneak.berlin/go/secret/internal/bip39"
	"sneak.berlin/go/secret/internal/secret"
	"sneak.berlin/go/secret/internal/vault"
)

// Sentinel errors for vault operations
var (
	errMnemonicEmpty         = errors.New("mnemonic cannot be empty")
	errInvalidMnemonicPhrase = errors.New("invalid BIP39 mnemonic phrase")
	errCannotRemoveLastVault = errors.New("cannot remove the last vault")
)

func newVaultCmd() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "vault",
		Short: "Manage vaults",
		Long:  `Create, list, and select vaults for organizing secrets.`,
	}

	cmd.AddCommand(newVaultListCmd())
	cmd.AddCommand(newVaultCreateCmd())
	cmd.AddCommand(newVaultSelectCmd())
	cmd.AddCommand(newVaultRemoveCmd())

	return cmd
}

func newVaultListCmd() *cobra.Command {
	cmd := &cobra.Command{
		Use:     cmdUseList,
		Aliases: []string{"ls"},
		Short:   "List available vaults",
		RunE: func(cmd *cobra.Command, _ []string) error {
			jsonOutput, _ := cmd.Flags().GetBool("json")

			cli, err := NewCLIInstance()
			if err != nil {
				return fmt.Errorf("failed to initialize CLI: %w", err)
			}

			return cli.ListVaults(cmd, jsonOutput)
		},
	}

	cmd.Flags().Bool("json", false, "Output in JSON format")

	return cmd
}

func newVaultCreateCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "create <name>",
		Short: "Create a new vault",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			cli, err := NewCLIInstance()
			if err != nil {
				return fmt.Errorf("failed to initialize CLI: %w", err)
			}

			destroySecrets := cli.readSecretEnv()
			defer destroySecrets()

			return cli.CreateVault(cmd, args[0])
		},
	}
}

func newVaultSelectCmd() *cobra.Command {
	cli, err := NewCLIInstance()
	if err != nil {
		log.Fatalf("failed to initialize CLI: %v", err)
	}

	return &cobra.Command{
		Use:               "select <name>",
		Short:             "Select a vault as current",
		Args:              cobra.ExactArgs(1),
		ValidArgsFunction: getVaultNamesCompletionFunc(cli.fs, cli.stateDir),
		RunE: func(cmd *cobra.Command, args []string) error {
			cli, err := NewCLIInstance()
			if err != nil {
				return fmt.Errorf("failed to initialize CLI: %w", err)
			}

			return cli.SelectVault(cmd, args[0])
		},
	}
}

func newVaultRemoveCmd() *cobra.Command {
	cli, err := NewCLIInstance()
	if err != nil {
		log.Fatalf("failed to initialize CLI: %v", err)
	}

	cmd := &cobra.Command{
		Use:     "remove <name>",
		Aliases: []string{"rm"},
		Short:   "Remove a vault",
		Long: `Remove a vault and all its secrets. Asks for ` +
			`confirmation first, naming how many secrets the vault ` +
			`holds; when stdin is not a terminal, fails unless --force ` +
			`is given. Will automatically switch to another vault if ` +
			`removing the currently selected one. The last vault ` +
			`cannot be removed.`,
		Args:              cobra.ExactArgs(1),
		ValidArgsFunction: getVaultNamesCompletionFunc(cli.fs, cli.stateDir),
		RunE: func(cmd *cobra.Command, args []string) error {
			force, _ := cmd.Flags().GetBool("force")

			cli, err := NewCLIInstance()
			if err != nil {
				return fmt.Errorf("failed to initialize CLI: %w", err)
			}

			return cli.RemoveVault(cmd, args[0], force)
		},
	}

	cmd.Flags().BoolP("force", "f", false,
		"Remove without asking for confirmation, even a vault that contains secrets")

	return cmd
}

// ListVaults lists all available vaults
func (cli *Instance) ListVaults(cmd *cobra.Command, jsonOutput bool) error {
	vaults, err := vault.ListVaults(cli.fs, cli.stateDir)
	if err != nil {
		return err
	}

	out := cmd.OutOrStdout()

	if jsonOutput { //nolint:nestif // Separate JSON and text output formatting logic
		// Get current vault name for context
		currentVault := ""

		currentVlt, err := vault.GetCurrentVault(cli.fs, cli.stateDir)
		if err == nil {
			currentVault = currentVlt.GetName()
		}

		result := map[string]any{
			"vaults":       vaults,
			"currentVault": currentVault,
		}

		jsonBytes, err := json.MarshalIndent(result, "", "  ")
		if err != nil {
			return err
		}

		_, _ = fmt.Fprintln(out, string(jsonBytes))
	} else {
		// Text output
		_, _ = fmt.Fprintln(out, "Available vaults:")

		if len(vaults) == 0 {
			_, _ = fmt.Fprintln(out, "  (none)")
		} else {
			// Try to get current vault for marking
			currentVault := ""

			currentVlt, err := vault.GetCurrentVault(cli.fs, cli.stateDir)
			if err == nil {
				currentVault = currentVlt.GetName()
			}

			for _, vaultName := range vaults {
				if vaultName == currentVault {
					_, _ = fmt.Fprintf(out, "  %s (current)\n", vaultName)
				} else {
					_, _ = fmt.Fprintf(out, "  %s\n", vaultName)
				}
			}
		}
	}

	return nil
}

// resolvePassphrase returns the unlock passphrase from the environment,
// cli.UnlockPassphrase, or prompts the user for it with confirmation. The
// returned cleanup function must be deferred by the caller.
func (cli *Instance) resolvePassphrase() (*memguard.LockedBuffer, func(), error) {
	if cli.UnlockPassphrase != nil {
		secret.Debug("Using unlock passphrase from environment variable")

		return cli.UnlockPassphrase, func() {}, nil
	}

	secret.Debug("Prompting user for unlock passphrase")

	// Use secure passphrase input with confirmation
	passphraseBuffer, err := readSecurePassphrase("Enter passphrase for unlocker: ")
	if err != nil {
		return nil, nil, err
	}

	return passphraseBuffer, passphraseBuffer.Destroy, nil
}

// CreateVault creates a new vault
func (cli *Instance) CreateVault(cmd *cobra.Command, name string) error {
	secret.Debug("Creating new vault", "name", name, "state_dir", cli.stateDir)

	release, err := vault.LockStateDir(cli.fs, cli.stateDir)
	if err != nil {
		return err
	}
	defer release()

	// Refuse an invalid name or an existing vault before asking for anything
	err = vault.CheckNewVaultName(cli.fs, cli.stateDir, name)
	if err != nil {
		return err
	}

	mnemonic, cleanupMnemonic, err := cli.promptMnemonic()
	if err != nil {
		return err
	}
	defer cleanupMnemonic()

	mnemonicStr := mnemonic.String()
	if mnemonicStr == "" {
		return errMnemonicEmpty
	}

	// Validate the mnemonic
	mnemonicWords := strings.Fields(mnemonicStr)
	secret.Debug("Validating BIP39 mnemonic", "word_count", len(mnemonicWords))

	if !bip39.IsMnemonicValid(mnemonicStr) {
		return errInvalidMnemonicPhrase
	}

	// Ask for the unlocker passphrase before creating the vault, so that
	// stopping at the prompt leaves no vault without an unlocker behind
	passphraseBuffer, cleanupPassphrase, err := cli.resolvePassphrase()
	if err != nil {
		return err
	}
	defer cleanupPassphrase()

	// Create the vault with its passphrase unlocker
	vlt, err := vault.CreateVault(cli.fs, cli.stateDir, name,
		mnemonic, passphraseBuffer)
	if err != nil {
		return err
	}

	ltIdentity, err := vlt.GetOrDeriveLongTermKey()
	if err != nil {
		return fmt.Errorf("failed to get long-term key: %w", err)
	}

	unlocker, err := vlt.GetCurrentUnlocker()
	if err != nil {
		return err
	}

	cmd.Printf("Created vault '%s'\n", vlt.GetName())
	cmd.Printf("Long-term public key: %s\n", ltIdentity.Recipient().String())
	cmd.Printf("Unlocker ID: %s\n", unlocker.GetID())

	return nil
}

// SelectVault selects a vault as the current one
func (cli *Instance) SelectVault(cmd *cobra.Command, name string) error {
	release, err := vault.LockStateDir(cli.fs, cli.stateDir)
	if err != nil {
		return err
	}
	defer release()

	err = vault.SelectVault(cli.fs, cli.stateDir, name)
	if err != nil {
		return err
	}

	cmd.Printf("Selected vault '%s' as current\n", name)

	return nil
}

// countVaultSecrets returns the number of secrets in the vault directory
func (cli *Instance) countVaultSecrets(vaultDir string) (int, error) {
	secretsDir := filepath.Join(vaultDir, "secrets.d")

	exists, err := afero.DirExists(cli.fs, secretsDir)
	if err != nil {
		return 0, fmt.Errorf("failed to check secrets directory %s: %w",
			secretsDir, err)
	}

	if !exists {
		return 0, nil
	}

	entries, err := afero.ReadDir(cli.fs, secretsDir)
	if err != nil {
		return 0, fmt.Errorf("failed to read secrets directory %s: %w",
			secretsDir, err)
	}

	return len(entries), nil
}

// switchAwayFromVault selects another vault as current before removal
func (cli *Instance) switchAwayFromVault(
	cmd *cobra.Command, vaults []string, name string,
) error {
	// Find another vault to switch to
	var newVault string

	for _, v := range vaults {
		if v != name {
			newVault = v

			break
		}
	}

	// Switch to the new vault
	err := vault.SelectVault(cli.fs, cli.stateDir, newVault)
	if err != nil {
		return fmt.Errorf("failed to switch to vault '%s': %w", newVault, err)
	}

	cmd.Printf("Switched current vault to '%s'\n", newVault)

	return nil
}

// RemoveVault removes a vault and all its secrets, after asking the user
// to confirm unless force is set.
func (cli *Instance) RemoveVault(cmd *cobra.Command, name string, force bool) error {
	err := vault.ValidateVaultName(name)
	if err != nil {
		return err
	}

	var found vaultToRemove

	release, err := cli.askThenLock(cmd, force, func() (string, error) {
		var err error

		found, err = cli.findVaultToRemove(name)

		return found.question, err
	})
	if err != nil {
		return err
	}
	defer release()

	// If removing current vault, switch to another vault first
	if found.isCurrent {
		err = cli.switchAwayFromVault(cmd, found.vaults, name)
		if err != nil {
			return err
		}
	}

	// Remove the vault directory
	err = secret.RemoveDirAtomic(cli.fs, found.dir)
	if err != nil {
		return fmt.Errorf("failed to remove vault directory: %w", err)
	}

	cmd.Printf("Removed vault '%s'\n", name)

	if found.secrets > 0 {
		cmd.Printf("Warning: Vault contained secrets that have been " +
			"permanently deleted\n")
	}

	return nil
}

// vaultToRemove is what removing a vault removes, as findVaultToRemove
// found it.
type vaultToRemove struct {
	// dir is the vault's directory, which holds all its secrets.
	dir     string
	secrets int
	// vaults lists every vault, this one included, and isCurrent is set
	// when this one is the current vault.
	vaults    []string
	isCurrent bool
	// question names what is removed, for the user to confirm.
	question string
}

// findVaultToRemove checks that the vault exists and is not the last one,
// and counts its secrets.
func (cli *Instance) findVaultToRemove(name string) (vaultToRemove, error) {
	vaults, err := vault.ListVaults(cli.fs, cli.stateDir)
	if err != nil {
		return vaultToRemove{}, fmt.Errorf("failed to list vaults: %w", err)
	}

	if !slices.Contains(vaults, name) {
		return vaultToRemove{},
			fmt.Errorf("vault '%s' %w", name, vault.ErrVaultNotFound)
	}

	if len(vaults) == 1 {
		return vaultToRemove{}, errCannotRemoveLastVault
	}

	currentVault, err := vault.GetCurrentVault(cli.fs, cli.stateDir)
	if err != nil {
		return vaultToRemove{},
			fmt.Errorf("failed to get current vault: %w", err)
	}

	vaultDir, err := vault.NewVault(cli.fs, cli.stateDir, name).GetDirectory()
	if err != nil {
		return vaultToRemove{},
			fmt.Errorf("failed to get vault directory: %w", err)
	}

	secrets, err := cli.countVaultSecrets(vaultDir)
	if err != nil {
		return vaultToRemove{}, err
	}

	return vaultToRemove{
		dir:       vaultDir,
		secrets:   secrets,
		vaults:    vaults,
		isCurrent: currentVault.GetName() == name,
		question: fmt.Sprintf(
			"Permanently remove vault '%s' and its %d secret(s)?",
			name, secrets),
	}, nil
}