zircon/system/ulib/cmdline/include/cmdline/status.h

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CMDLINE_STATUS_H_
#define CMDLINE_STATUS_H_

#include <string>

namespace cmdline {

// Return an object of this class from an otherwise void function to indicate
// if the function executed successfully, or in the case of an error, to
// provide an error message with additional detail. The message should be
// worded for consumption by end-users of an application, such as to print
// an error message from a command line tool, or perhaps a label field or
// dialog window in a UI.
class Status {
public:
    // Return |Status::Ok()| to indicate the function did not fail.
    // |Status| objects are copyable and assignable, so you can create a default
    // |Status| and later assign a |Status::Error(with_message)|.
    // For example:
    //
    //   Status status = Status::Ok();
    //   if (it_failed) {
    //     status = Status::Error("It didn't work.");
    //   }
    //   cleanup();
    //   return status;
    static Status Ok() {
        return Status();
    }

    // Return |Status::Error(error_message)| to indicate the function failed,
    // and provide a message explaining the error, suitable for an end user.
    static Status Error(const std::string& error_message) {
        return Status(
            error_message.size() > 0 ? error_message : "There was an error.");
    }

    // Returns |true| if constructed with a non-empty message, indicating the
    // outcome of the call was an error.
    bool has_error() const { return error_message_.size() > 0; }

    // Returns |true| if constructed with no arguments, or an empty string,
    // indicating the function completed successfully.
    bool ok() const { return error_message_.size() == 0; }

    // Returns an non-empty string if the outcome of the call was an error.
    std::string error_message() const {
        return error_message_;
    }

private:
    Status() = default;

    Status(const std::string& error_message)
        : error_message_(error_message) {}

    std::string error_message_;
};

} // namespace cmdline

#endif // CMDLINE_STATUS_H_