package sqlite

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"forge.cadoles.com/wpetit/hydra-webauthn/internal/storage"
	"github.com/go-webauthn/webauthn/webauthn"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"

	_ "embed"

	_ "modernc.org/sqlite"
)

type UserRepository struct {
	db                         *sql.DB
	sqliteBusyRetryMaxAttempts int
}

// Create implements storage.UserRepository.
func (r *UserRepository) CreateUser(ctx context.Context, username string, attributes map[string]any) (*storage.User, error) {
	user := storage.NewUser(username, attributes)

	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := `SELECT COUNT(id) FROM users WHERE username = $1`
		args := []any{
			user.Username,
		}

		row := tx.QueryRowContext(ctx, query, args...)

		var count int64
		if err := row.Scan(&count); err != nil {
			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		if count > 0 {
			return errors.WithStack(storage.ErrAlreadyExist)
		}

		query = `
		INSERT INTO users (id, username, attributes, created_at, updated_at)
		VALUES ($1, $2, $3, $4, $4)
		`

		rawAttributes, err := json.Marshal(user.Attributes)
		if err != nil {
			return errors.WithStack(err)
		}

		args = []any{
			user.ID,
			user.Username,
			rawAttributes,
			user.CreatedAt,
			user.UpdatedAt,
		}

		if _, err := tx.ExecContext(ctx, query, args...); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return user, nil
}

// DeleteUserByID implements storage.UserRepository.
func (*UserRepository) DeleteUserByID(ctx context.Context, username string) error {
	panic("unimplemented")
}

// FindUserByUsername implements storage.UserRepository.
func (r *UserRepository) FindUserByUsername(ctx context.Context, username string) (*storage.User, error) {
	user, err := r.findUserBy(ctx, "username", username)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return user, nil
}

// FindUserByID implements storage.UserRepository.
func (r *UserRepository) FindUserByID(ctx context.Context, userID string) (*storage.User, error) {
	user, err := r.findUserBy(ctx, "id", userID)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return user, nil
}

func (r *UserRepository) findUserBy(ctx context.Context, column string, value any) (*storage.User, error) {
	user := &storage.User{}
	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := fmt.Sprintf(`SELECT id, username, attributes, created_at, updated_at FROM users WHERE %s = $1`, column)
		args := []any{
			value,
		}

		var rawAttributes []byte

		row := tx.QueryRowContext(ctx, query, args...)
		if err := row.Scan(&user.ID, &user.Username, &rawAttributes, &user.CreatedAt, &user.UpdatedAt); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.WithStack(storage.ErrNotFound)
			}

			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		if err := json.Unmarshal(rawAttributes, &user.Attributes); err != nil {
			return errors.WithStack(err)
		}

		if user.Attributes == nil {
			user.Attributes = make(map[string]any)
		}

		query = `SELECT credential FROM user_credentials WHERE user_id = $1`
		args = []any{
			user.ID,
		}

		rows, err := tx.QueryContext(ctx, query, args...)
		if err != nil {
			return errors.WithStack(err)
		}

		defer func() {
			if err := rows.Close(); err != nil {
				logger.Error(ctx, "could not close rows", logger.E(errors.WithStack(err)))
			}
		}()

		user.Credentials = make([]webauthn.Credential, 0)

		for rows.Next() {
			var (
				rawCredential []byte
				credential    webauthn.Credential
			)

			if err := rows.Scan(&rawCredential); err != nil {
				return errors.WithStack(err)
			}

			if err := json.Unmarshal(rawCredential, &credential); err != nil {
				return errors.WithStack(err)
			}

			user.Credentials = append(user.Credentials, credential)
		}

		if err := rows.Err(); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return user, nil
}

// List implements storage.UserRepository.
func (r *UserRepository) ListUsers(ctx context.Context) ([]storage.UserHeader, error) {
	users := make([]storage.UserHeader, 0)

	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := `SELECT id, username, created_at, updated_at FROM users`

		rows, err := tx.QueryContext(ctx, query)
		if err != nil {
			return errors.WithStack(err)
		}

		defer func() {
			if err := rows.Close(); err != nil {
				logger.Error(ctx, "could not close rows", logger.E(errors.WithStack(err)))
			}
		}()

		for rows.Next() {
			user := storage.UserHeader{}
			if err := rows.Scan(&user.ID, &user.Username, &user.CreatedAt, &user.UpdatedAt); err != nil {
				return errors.WithStack(err)
			}

			users = append(users, user)
		}

		if err := rows.Err(); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return users, nil
}

// UpdateUsername implements storage.UserRepository.
func (r *UserRepository) UpdateUserUsername(ctx context.Context, userID string, username string) (*storage.User, error) {
	var user *storage.User

	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := `SELECT COUNT(id) FROM users WHERE id = $1`
		args := []any{
			userID,
		}

		row := tx.QueryRowContext(ctx, query, args...)

		var count int64
		if err := row.Scan(&count); err != nil {
			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		if count == 0 {
			return errors.WithStack(storage.ErrNotFound)
		}

		query = `
		UPDATE users SET username = $1, updated_at = $2 WHERE id = $3
		RETURNING id, username, attributes, created_at, updated_at
		`

		args = []any{
			username,
			time.Now(),
			userID,
		}

		var rawAttributes []byte

		user = &storage.User{}

		row = tx.QueryRowContext(ctx, query, args...)
		if err := row.Scan(&user.ID, &user.Username, &rawAttributes, &user.CreatedAt, &user.UpdatedAt); err != nil {
			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		if err := json.Unmarshal(rawAttributes, &user.Attributes); err != nil {
			return errors.WithStack(err)
		}

		if user.Attributes == nil {
			user.Attributes = make(map[string]any)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return user, nil
}

// Update implements storage.UserRepository.
func (r *UserRepository) UpdateUserAttributes(ctx context.Context, userID string, attributes map[string]any) (*storage.User, error) {
	var user *storage.User

	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := `SELECT COUNT(id) FROM users WHERE id = $1`
		args := []any{
			userID,
		}

		row := tx.QueryRowContext(ctx, query, args...)

		var count int64
		if err := row.Scan(&count); err != nil {
			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		if count == 0 {
			return errors.WithStack(storage.ErrNotFound)
		}

		query = `
		UPDATE users SET attributes = $1, updated_at = $2 WHERE id = $3
		RETURNING id, username, attributes, created_at, updated_at
		`

		rawAttributes, err := json.Marshal(attributes)
		if err != nil {
			return errors.WithStack(err)
		}

		args = []any{
			rawAttributes,
			time.Now(),
			userID,
		}

		user = &storage.User{}

		row = tx.QueryRowContext(ctx, query, args...)
		if err := row.Scan(&user.ID, &user.Username, &rawAttributes, &user.CreatedAt, &user.UpdatedAt); err != nil {
			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		if err := json.Unmarshal(rawAttributes, &user.Attributes); err != nil {
			return errors.WithStack(err)
		}

		if user.Attributes == nil {
			user.Attributes = make(map[string]any)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return user, nil
}

// AddCredential implements storage.UserRepository.
func (r *UserRepository) AddUserCredential(ctx context.Context, userID string, credential *webauthn.Credential) (string, error) {
	credentialID := storage.NewID()

	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		exists, err := r.userExists(ctx, tx, userID)
		if err != nil {
			return errors.WithStack(err)
		}

		if !exists {
			return errors.WithStack(storage.ErrNotFound)
		}

		query := `
		INSERT INTO user_credentials (id, user_id, credential, created_at) 
		VALUES ($1, $2, $3, $4)
		`

		rawCredential, err := json.Marshal(credential)
		if err != nil {
			return errors.WithStack(err)
		}

		args := []any{
			credentialID,
			userID,
			rawCredential,
			time.Now(),
		}

		if _, err := tx.ExecContext(ctx, query, args...); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return "", errors.WithStack(err)
	}

	return credentialID, nil
}

// RemoveCredential implements storage.UserRepository.
func (r *UserRepository) RemoveUserCredential(ctx context.Context, userID string, credentialID string) error {
	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		exists, err := r.userExists(ctx, tx, userID)
		if err != nil {
			return errors.WithStack(err)
		}

		if !exists {
			return errors.WithStack(storage.ErrNotFound)
		}

		query := `
		DELETE FROM user_credentials WHERE id = $1 AND user_id = $2 
		`

		args := []any{
			credentialID,
			userID,
		}

		if _, err := tx.ExecContext(ctx, query, args...); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return errors.WithStack(err)
	}

	return nil
}

// GenerateRegistrationLink implements storage.UserRepository.
func (r *UserRepository) GenerateRegistrationLink(ctx context.Context, userID string) (*storage.RegistrationLink, error) {
	registrationLink := storage.NewRegistrationLink(userID)

	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		exists, err := r.userExists(ctx, tx, userID)
		if err != nil {
			return errors.WithStack(err)
		}

		if !exists {
			return errors.WithStack(storage.ErrNotFound)
		}

		query := `DELETE FROM registration_links WHERE user_id = $1`
		args := []any{
			registrationLink.UserID,
		}

		if _, err := tx.ExecContext(ctx, query, args...); err != nil {
			return errors.WithStack(err)
		}

		query = `
		INSERT INTO registration_links (token, user_id, created_at)
		VALUES ($1, $2, $3)
		`

		args = []any{
			registrationLink.Token,
			registrationLink.UserID,
			registrationLink.CreatedAt,
		}

		if _, err := tx.ExecContext(ctx, query, args...); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return registrationLink, nil
}

// ClearRegistrationLink implements storage.UserRepository.
func (*UserRepository) ClearRegistrationLink(ctx context.Context, userID string) error {
	panic("unimplemented")
}

// GetRegistrationLink implements storage.UserRepository.
func (r *UserRepository) GetRegistrationLink(ctx context.Context, userID string) (*storage.RegistrationLink, error) {
	registrationLink := &storage.RegistrationLink{}
	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := `SELECT token, user_id, created_at FROM registration_links WHERE user_id = $1`
		args := []any{
			userID,
		}

		row := tx.QueryRowContext(ctx, query, args...)
		if err := row.Scan(&registrationLink.Token, &registrationLink.UserID, &registrationLink.CreatedAt); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.WithStack(storage.ErrNotFound)
			}

			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return registrationLink, nil
}

// GetRegistrationLinkByToken implements storage.UserRepository.
func (r *UserRepository) GetRegistrationLinkByToken(ctx context.Context, token string) (*storage.RegistrationLink, error) {
	registrationLink := &storage.RegistrationLink{}
	err := r.withTxRetry(ctx, func(tx *sql.Tx) error {
		query := `SELECT token, user_id, created_at FROM registration_links WHERE token = $1`
		args := []any{
			token,
		}

		row := tx.QueryRowContext(ctx, query, args...)
		if err := row.Scan(&registrationLink.Token, &registrationLink.UserID, &registrationLink.CreatedAt); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.WithStack(storage.ErrNotFound)
			}

			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return registrationLink, nil
}

func (r *UserRepository) userExists(ctx context.Context, tx *sql.Tx, userID string) (bool, error) {
	query := `SELECT COUNT(id) FROM users WHERE id = $1`
	args := []any{
		userID,
	}

	row := tx.QueryRowContext(ctx, query, args...)

	var count int64
	if err := row.Scan(&count); err != nil {
		return false, errors.WithStack(err)
	}

	if err := row.Err(); err != nil {
		return false, errors.WithStack(err)
	}

	return count >= 1, nil
}

func (r *UserRepository) withTxRetry(ctx context.Context, fn func(*sql.Tx) error) error {
	attempts := 0
	max := r.sqliteBusyRetryMaxAttempts

	ctx = logger.With(ctx, logger.F("max", max))

	var err error
	for {
		ctx = logger.With(ctx)

		if attempts >= max {
			logger.Debug(ctx, "transaction retrying failed", logger.F("attempts", attempts))

			return errors.Wrapf(err, "transaction failed after %d attempts", max)
		}

		err = r.withTx(ctx, fn)
		if err != nil {
			if !strings.Contains(err.Error(), "(5) (SQLITE_BUSY)") {
				return errors.WithStack(err)
			}

			err = errors.WithStack(err)

			logger.Warn(ctx, "database is busy", logger.E(err))

			wait := time.Duration(8<<(attempts+1)) * time.Millisecond

			logger.Debug(
				ctx, "database is busy, waiting before retrying transaction",
				logger.F("wait", wait.String()),
				logger.F("attempts", attempts),
			)

			timer := time.NewTimer(wait)
			select {
			case <-timer.C:
				attempts++
				continue

			case <-ctx.Done():
				if err := ctx.Err(); err != nil {
					return errors.WithStack(err)
				}

				return nil
			}
		}

		return nil
	}
}

func (r *UserRepository) withTx(ctx context.Context, fn func(*sql.Tx) error) error {
	tx, err := r.db.BeginTx(ctx, nil)
	if err != nil {
		return errors.WithStack(err)
	}

	defer func() {
		if err := tx.Rollback(); err != nil {
			if errors.Is(err, sql.ErrTxDone) {
				return
			}

			err = errors.WithStack(err)
			logger.Error(ctx, "could not rollback transaction", logger.CapturedE(err))
		}
	}()

	if err := fn(tx); err != nil {
		return errors.WithStack(err)
	}

	if err := tx.Commit(); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func NewUserRepository(dsn string) (*UserRepository, error) {
	db, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	if err := applyUserRepositoryMigration(db); err != nil {
		return nil, errors.Wrap(err, "could not migrate schema")
	}

	return &UserRepository{db, 5}, nil
}

var _ storage.UserRepository = &UserRepository{}

//go:embed user_repository.sql
var userRepositoryMigrationScript string

func applyUserRepositoryMigration(db *sql.DB) error {
	if err := db.Ping(); err != nil {
		return errors.WithStack(err)
	}

	if _, err := db.Exec(userRepositoryMigrationScript); err != nil {
		return errors.WithStack(err)
	}

	return nil
}