[/
    Copyright (c) 2023-2025 Ivica Siladic, Bruno Iljazovic, Korina Simicevic
    Distributed under the Boost Software License, Version 1.0.
    (See accompanying file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
]

[section:pubcomp_props PUBCOMP properties]
The last field in the Variable header of __PUBCOMP__ packet is a set of Properties.
A set contains a Property Length followed by the Properties.
A Property consists of an Identifier and a value.

This class extends [reflink2 prop__properties prop::properties], which provides common functionalities for all property classes.
Below is a list of possible __PUBCOMP__ Properties, along with descriptions of their usage:

[table:pubcomp_props PUBCOMP properties
    [[Identifier] [Value type] [Description]]
    [[reason_string] [`std::string`] [A UTF-8 Encoded String representing the reason associated with this response.]]
    [[user_property] [`std::vector<std::pair<std::string, std::string>>`] [Name, value pair (__UTF8_STRING_PAIR__) defining User Property. There can be multiple pairs in one packet. 
        This property may be used to provide additional diagnostic or other information. ]]
]

[h4 Usage]
After obtaining an instance of `boost::mqtt5::pubcomp_props`, the subscript operator can be used to access a Property.

The Identifiers listed in the table above are available within the `boost::mqtt5::prop` namespace for Property access.

[note When accessing a property value, the subscript operator will return a `std::optional` of the value type for all properties,
except for `boost::mqtt5::prop::user_property`, where it will return an instance of `std::vector<std::pair<std::string, std::string>>`.]

[h4 Example]

The following example shows how to set a Property value:

[!c++]
    boost::mqtt5::pubcomp_props props;
    props[boost::mqtt5::prop::reason_string] = "Some reason...";
    props[boost::mqtt5::prop::user_property].emplace_back("name", "value");

The following example shows how to retrieve a Property value:

[!c++]
    std::optional<std::string> reason_string = props[boost::mqtt5::prop::reason_string];
    if (reason_string.has_value())
        // reason string property was previously set
    else
        // reason string property was not set
    
    std::vector<std::pair<std::string, std::string>>& user_props = props[boost::mqtt5::prop::user_property];
    if (!user_props.empty())
        // user property was previously set
    else
        // user property was not set

[endsect]
