package auth

import (
	"database/sql"
	"fmt"
	"time"

	"github.com/go-webauthn/webauthn/protocol"
	"github.com/go-webauthn/webauthn/webauthn"
)

// WebAuthnUser implements the webauthn.User interface.
type WebAuthnUser struct {
	ID          int64
	Username    string
	Credentials []webauthn.Credential
}

func (u *WebAuthnUser) WebAuthnID() []byte {
	return []byte(fmt.Sprintf("%d", u.ID))
}

func (u *WebAuthnUser) WebAuthnName() string {
	return u.Username
}

func (u *WebAuthnUser) WebAuthnDisplayName() string {
	return u.Username
}

func (u *WebAuthnUser) WebAuthnCredentials() []webauthn.Credential {
	return u.Credentials
}

// NewWebAuthn creates a configured WebAuthn instance.
func NewWebAuthn(rpDisplayName, rpID string, rpOrigins []string) (*webauthn.WebAuthn, error) {
	return webauthn.New(&webauthn.Config{
		RPDisplayName: rpDisplayName,
		RPID:          rpID,
		RPOrigins:     rpOrigins,
		AuthenticatorSelection: protocol.AuthenticatorSelection{
			AuthenticatorAttachment: protocol.CrossPlatform,
			UserVerification:        protocol.VerificationPreferred,
		},
	})
}

// LoadWebAuthnUser loads a user with their WebAuthn credentials.
func LoadWebAuthnUser(database *sql.DB, userID int64) (*WebAuthnUser, error) {
	var username string
	err := database.QueryRow("SELECT username FROM users WHERE id = ?", userID).Scan(&username)
	if err != nil {
		return nil, fmt.Errorf("user not found: %w", err)
	}

	rows, err := database.Query(
		"SELECT credential_id, public_key, sign_count FROM webauthn_credentials WHERE user_id = ?",
		userID,
	)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()

	var creds []webauthn.Credential
	for rows.Next() {
		var cred webauthn.Credential
		var signCount uint32
		if err := rows.Scan(&cred.ID, &cred.PublicKey, &signCount); err != nil {
			continue
		}
		cred.Authenticator.SignCount = signCount
		creds = append(creds, cred)
	}

	return &WebAuthnUser{
		ID:          userID,
		Username:    username,
		Credentials: creds,
	}, nil
}

// StoreWebAuthnCredential saves a new credential for a user.
func StoreWebAuthnCredential(database *sql.DB, userID int64, name string, cred *webauthn.Credential) error {
	_, err := database.Exec(
		"INSERT INTO webauthn_credentials (user_id, credential_id, public_key, name, sign_count, created_at) VALUES (?, ?, ?, ?, ?, ?)",
		userID, cred.ID, cred.PublicKey, name, cred.Authenticator.SignCount, time.Now().UnixMilli(),
	)
	return err
}

// UpdateWebAuthnSignCount updates the signature counter after authentication.
func UpdateWebAuthnSignCount(database *sql.DB, credentialID []byte, signCount uint32) error {
	_, err := database.Exec(
		"UPDATE webauthn_credentials SET sign_count = ? WHERE credential_id = ?",
		signCount, credentialID,
	)
	return err
}

// ListWebAuthnCredentials returns all credentials for a user.
func ListWebAuthnCredentials(database *sql.DB, userID int64) ([]WebAuthnCredentialInfo, error) {
	rows, err := database.Query(
		"SELECT id, name, created_at FROM webauthn_credentials WHERE user_id = ? ORDER BY created_at",
		userID,
	)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()

	var creds []WebAuthnCredentialInfo
	for rows.Next() {
		var c WebAuthnCredentialInfo
		var createdAt int64
		if err := rows.Scan(&c.ID, &c.Name, &createdAt); err != nil {
			continue
		}
		c.CreatedAt = time.UnixMilli(createdAt)
		creds = append(creds, c)
	}
	return creds, nil
}

type WebAuthnCredentialInfo struct {
	ID        int64
	Name      string
	CreatedAt time.Time
}

// DeleteWebAuthnCredential removes a credential.
func DeleteWebAuthnCredential(database *sql.DB, credID int64, userID int64) error {
	_, err := database.Exec(
		"DELETE FROM webauthn_credentials WHERE id = ? AND user_id = ?",
		credID, userID,
	)
	return err
}

// FindUserByCredentialID looks up which user owns a credential.
func FindUserByCredentialID(database *sql.DB, credentialID []byte) (int64, error) {
	var userID int64
	err := database.QueryRow(
		"SELECT user_id FROM webauthn_credentials WHERE credential_id = ?",
		credentialID,
	).Scan(&userID)
	if err != nil {
		return 0, fmt.Errorf("credential not found: %w", err)
	}
	return userID, nil
}