package cli

import (
	"errors"
	"fmt"
	"log"
	"log/slog"
	"os"
	"path/filepath"
	"strings"

	"filippo.io/age"
	"git.eeqj.de/sneak/secret/internal/secret"
	"git.eeqj.de/sneak/secret/internal/vault"
	"git.eeqj.de/sneak/secret/pkg/agehd"
	"github.com/awnumar/memguard"
	"github.com/spf13/cobra"
	"github.com/tyler-smith/go-bip39"
)

// errPassphraseMismatch is returned when passphrase confirmation fails
var errPassphraseMismatch = errors.New("passphrases do not match")

// NewInitCmd creates the init command
func NewInitCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "init",
		Short: "Initialize the secrets manager",
		Long: `Create the necessary directory structure for storing ` +
			`secrets and generate encryption keys.`,
		RunE: RunInit,
	}
}

// RunInit is the exported function that handles the init command
func RunInit(cmd *cobra.Command, _ []string) error {
	cli, err := NewCLIInstance()
	if err != nil {
		log.Fatalf("failed to initialize CLI: %v", err)
	}

	return cli.Init(cmd)
}

// promptMnemonic reads the mnemonic from the environment or interactively.
// The returned cleanup function must be deferred by the caller.
func promptMnemonic() (string, func(), error) {
	if envMnemonic := os.Getenv(secret.EnvMnemonic); envMnemonic != "" {
		secret.Debug("Using mnemonic from environment variable")

		return envMnemonic, func() {}, nil
	}

	secret.Debug("Prompting user for mnemonic phrase")

	// Read mnemonic securely without echo
	mnemonicBuffer, err := secret.ReadPassphrase("Enter your BIP39 mnemonic phrase: ")
	if err != nil {
		secret.Debug("Failed to read mnemonic from stdin", "error", err)

		return "", nil, fmt.Errorf("failed to read mnemonic: %w", err)
	}

	fmt.Fprintln(os.Stderr) // Add newline after hidden input

	return mnemonicBuffer.String(), mnemonicBuffer.Destroy, nil
}

// setupDefaultVault creates the default vault and derives its long-term
// identity from the mnemonic
func (cli *Instance) setupDefaultVault(
	stateDir, mnemonicStr string,
) (*vault.Vault, *age.X25519Identity, error) {
	// Create the default vault - it will handle key derivation internally
	secret.Debug("Creating default vault")

	vlt, err := vault.CreateVault(cli.fs, cli.stateDir, "default")
	if err != nil {
		secret.Debug("Failed to create default vault", "error", err)

		return nil, nil, fmt.Errorf("failed to create default vault: %w", err)
	}

	// Get the vault metadata to retrieve the derivation index
	vaultDir := filepath.Join(stateDir, "vaults.d", "default")

	metadata, err := vault.LoadVaultMetadata(cli.fs, vaultDir)
	if err != nil {
		secret.Debug("Failed to load vault metadata", "error", err)

		return nil, nil, fmt.Errorf("failed to load vault metadata: %w", err)
	}

	// Derive the long-term key using the same index that CreateVault used
	ltIdentity, err := agehd.DeriveIdentity(mnemonicStr, metadata.DerivationIndex)
	if err != nil {
		secret.Debug("Failed to derive long-term key", "error", err)

		return nil, nil, fmt.Errorf(
			"failed to derive long-term key from mnemonic: %w", err)
	}

	return vlt, ltIdentity, nil
}

// Init initializes the secret manager
func (cli *Instance) Init(cmd *cobra.Command) error {
	secret.Debug("Starting secret manager initialization")

	// Create state directory
	stateDir := cli.GetStateDir()
	secret.DebugWith("Creating state directory", slog.String("path", stateDir))

	err := cli.fs.MkdirAll(stateDir, secret.DirPerms)
	if err != nil {
		secret.Debug("Failed to create state directory", "error", err)

		return fmt.Errorf("failed to create state directory: %w", err)
	}

	if cmd != nil {
		cmd.Printf("Initialized secrets manager at: %s\n", stateDir)
	}

	// Prompt for mnemonic
	mnemonicStr, cleanupMnemonic, err := promptMnemonic()
	if err != nil {
		return err
	}
	defer cleanupMnemonic()

	if mnemonicStr == "" {
		secret.Debug("Empty mnemonic provided")

		return errMnemonicEmpty
	}

	// Validate the mnemonic using BIP39
	secret.DebugWith("Validating BIP39 mnemonic",
		slog.Int("word_count", len(strings.Fields(mnemonicStr))))

	if !bip39.IsMnemonicValid(mnemonicStr) {
		secret.Debug("Invalid BIP39 mnemonic provided")

		return fmt.Errorf(
			"%w\nRun 'secret generate mnemonic' to create a valid mnemonic",
			errInvalidMnemonicPhrase)
	}

	// Set mnemonic in environment for CreateVault to use
	restoreMnemonicEnv := setMnemonicEnv(mnemonicStr)
	defer restoreMnemonicEnv()

	// Create the default vault and derive its long-term key
	vlt, ltIdentity, err := cli.setupDefaultVault(stateDir, mnemonicStr)
	if err != nil {
		return err
	}

	ltPubKey := ltIdentity.Recipient().String()

	// Unlock the vault with the derived long-term key
	vlt.Unlock(ltIdentity)

	// Prompt for passphrase for unlocker
	passphraseBuffer, err := resolvePassphrase()
	if err != nil {
		return err
	}
	defer passphraseBuffer.Destroy()

	// Create passphrase-protected unlocker
	secret.Debug("Creating passphrase-protected unlocker")

	passphraseUnlocker, err := vlt.CreatePassphraseUnlocker(passphraseBuffer)
	if err != nil {
		secret.Debug("Failed to create unlocker", "error", err)

		return fmt.Errorf("failed to create unlocker: %w", err)
	}

	// Note: CreatePassphraseUnlocker already encrypts and writes the long-term
	// private key to longterm.age, so no need to do it again here.

	if cmd != nil {
		cmd.Printf("\nDefault vault created and configured\n")
		cmd.Printf("Long-term public key: %s\n", ltPubKey)
		cmd.Printf("Unlocker ID: %s\n", passphraseUnlocker.GetID())
		cmd.Println("\nYour secret manager is ready to use!")
		cmd.Println("Note: When using SB_SECRET_MNEMONIC environment variable,")
		cmd.Println("unlockers are not required for secret operations.")
	}

	return nil
}

// readSecurePassphrase reads a passphrase securely from the terminal without echoing
// This version adds confirmation (read twice) for creating new unlockers
// Returns a LockedBuffer containing the passphrase
func readSecurePassphrase(prompt string) (*memguard.LockedBuffer, error) {
	// Get the first passphrase
	passphraseBuffer1, err := secret.ReadPassphrase(prompt)
	if err != nil {
		return nil, err
	}

	// Read confirmation passphrase
	passphraseBuffer2, err := secret.ReadPassphrase("Confirm passphrase: ")
	if err != nil {
		passphraseBuffer1.Destroy()

		return nil, fmt.Errorf("failed to read passphrase confirmation: %w", err)
	}

	// Compare passphrases
	if passphraseBuffer1.String() != passphraseBuffer2.String() {
		passphraseBuffer1.Destroy()
		passphraseBuffer2.Destroy()

		return nil, errPassphraseMismatch
	}

	// Clean up the second buffer, we'll return the first
	passphraseBuffer2.Destroy()

	// Return the first buffer (caller is responsible for destroying it)
	return passphraseBuffer1, nil
}