wxWidgets/interface/wx/webrequest.h

/////////////////////////////////////////////////////////////////////////////
// Name:        webrequest.h
// Created:     2018-10-14
// Copyright:   (c) 2018 wxWidgets development team
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

/**
    @class wxWebRequest

    This class allows for simple HTTP requests using the operating systems
    components as implementation.

    The latest features of the operating system will be used if available
    (e.g. HTTP/2, TLS 1.3).
    System-wide configuration like proxy and SSL certificates will be used
    when possible.

    Instances of wxWebRequest are created by using
    wxWebSession::CreateRequest().

    The requests are handled asynchronously and event handlers are used to
    communicate the request status. The response data may be stored in
    memory, to a file or processed directly, see SetStorage() for details.

    Example usage:

    @code
        // Create the request object
        wxObjectDataPtr<wxWebRequest> request(
            wxWebSession::GetDefault().CreateRequest("https://www.wxwidgets.org/downloads/logos/blocks.png"));

        // Bind state event
        request->Bind(wxEVT_WEBREQUEST_STATE, [](wxWebRequestEvent& evt) {
            switch (evt.GetState())
            {
                // Request completed
                case wxWebRequest::State_Completed:
                {
                    wxImage logoImage(*evt->GetResponse()->GetStream());
                    if (logoImage.IsOK())
                        wxLogInfo("Image loaded");
                    break;
                }
                // Request failed
                case wxWebRequest::State_Failed:
                    wxLogError("Could not load logo: %s", evt.GetErrorDescription());
                    break;
            }

        });

        // Start the request
        request->Start();
    @endcode

    @section descriptions Implementation Descriptions

    The following APIs are used per platform, additional documentation
    about supported features may be found in their documentation

    Available features by implementation and minimum version:
    <table>
    <tr><th>Operating System</th><th>API</th><th>HTTPS</th><th>HTTP/2</th></tr>
    <tr>
        <td>Windows</td>
        <td>
            <a target=_new href="https://docs.microsoft.com/en-us/windows/desktop/WinHttp/about-winhttp">WinHTTP</a>
        </td>
        <td>Yes</td>
        <td>Windows 10 1607</td>
    </tr>
    <tr>
        <td>macOS</td>
        <td>
            <a target=_new href="https://developer.apple.com/documentation/foundation/urlsession">NSURLSession</a>
        </td>
        <td>macOS 10.9</td>
        <td>macOS 10.11</td>
    </tr>
    <tr>
        <td>iOS</td>
        <td>
            <a target=_new href="https://developer.apple.com/documentation/foundation/urlsession">NSURLSession</a>
        </td>
        <td>iOS 7.0</td>
        <td>iOS 9.0</td>
    </tr>
    <tr>
        <td>Linux</td>
        <td>
            <a target=_new href="https://curl.haxx.se/libcurl/">libcurl</a>
        </td>
        <td>Yes</td>
        <td>7.47.0</td>
    </tr>
    </table>

    @beginEventEmissionTable{wxWebRequestEvent}
    @event{wxEVT_WEBREQUEST_STATE(id, func)}
        The request state changed.
    @event{wxEVT_WEBREQUEST_DATA(id, func)}
        A new block of data has been downloaded.
    @event{wxEVT_WEBREQUEST_DOWNLOAD_PROGRESS(id, func)}
        This event periodically reports the download progress while the request
        is active.
    @event{wxEVT_WEBREQUEST_UPLOAD_PROGRESS(id, func)}
        This event periodically reports the upload progress while the request
        is active.
    @endEventTable

    @since 3.1.2

    @library{wxnet}
    @category{net}

    @see wxWebResponse, wxWebSession
*/
class wxWebRequest: public wxEvtHandler, public wxRefCounter
{
public:
    /**
        Possible request states returned by GetState().
    */
    enum State
    {
        /// The request has just been created and Start() has not been called
        State_Idle,

        /// The request has been started and is transferring data
        State_Active,

        /**
            The server denied the request because of insufficient
            user credentials. When credentials are provided with
            SetCredentials() the request will be retried with the supplied
            user credentials.
        */
        State_Unauthorized,

        /**
            A proxy denied the request because of insufficient
            user credentials. When credentials are provided with
            SetCredentials() the request will be retried with the supplied
            user credentials.
        */
        State_UnauthorizedProxy,

        /// The request completed successfully and all data has been received.
        State_Completed,

        /// The request failed
        State_Failed,

        /// The request has been cancelled before completion by calling Cancel()
        State_Cancelled
    };

    /**
        Possible storage types. Set by SetStorage().
    */
    enum Storage
    {
        /// All data is collected in memory until the request is complete
        Storage_Memory,

        /// The data is written to a file on disk
        Storage_File,

        /**
            The data is not stored by the request and is only available
            via events.
        */
        Storage_None
    };

    /// Possible credential targets used by SetCredentials().
    enum CredentialTarget
    {
        /// Set credentials to be sent to the server.
        CredentialTarget_Server,

        /// Set credentials to be sent to a proxy.
        CredentialTarget_Proxy
    }

    /**
        Sets a request header which will be sent to the server by this request.

        The header will be added if it hasn't been set before or replaced
        otherwise.

        @param name
            Name of the header
        @param value
            String value of the header. An empty string will remove the header.
    */
    void SetHeader(const wxString& name, const wxString& value);

    /**
        Set <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html">common</a>
        or expanded HTTP method.

        The default method is GET unless request data is provided in which
        case POST is the default.

        @param method
            HTTP method name, e.g. "GET".
    */
    void SetMethod(const wxString& method);

    /**
        Set the text to be posted to the server.

        After a successful call to this method, the request will use HTTP @c
        POST instead of the default @c GET when it's executed.

        @param text
            The text data to post.
        @param contentType
            The value of HTTP "Content-Type" header, e.g. "text/html;
            charset=UTF-8".
        @param conv
            Conversion used when sending the text to the server
    */
    void SetData(const wxString& text, const wxString& contentType,
        const wxMBConv& conv = wxConvUTF8);

    /**
        Set the binary data to be posted to the server.

        The next request will be a HTTP @c POST instead of the default HTTP
        @c GET and the given @a dataStream will be posted as the body of
        this request.

        @param dataStream
            The data in this stream will be posted as the request body
        @param contentType
            The value of HTTP "Content-Type" header, e.g.
            "application/octet-stream".
        @param dataSize
            Amount of data which is sent to the server. If set to
            @c wxInvalidOffset all stream data is sent.

    */
    void SetData(wxSharedPtr<wxInputStream> dataStream,
        const wxString& contentType, wxFileOffset dataSize = wxInvalidOffset);

    /**
        Sets the credentials to be sent to the server or proxy when
        authentification is requested.

        @param user
            User name
        @param password
            Password
        @param target
            Specify the credentials for the server @c CredentialTarget_Server
            or the proxy @c CredentialTarget_Proxy.
    */
    void SetCredentials(const wxString& user, const wxString& password,
        CredentialTarget target);

    /**
        Instructs the request to ignore server error status codes.

        Per default, server side errors (status code 400-599) will enter
        the State_Failed state just like network errors, but
        if the response is still required in such cases (e.g. to get more
        details from the response body), set this option to ignore all errors.
        If ignored, wxWebResponse::GetStatus() has to be checked
        from the State_Completed event handler.
    */
    void SetIgnoreServerErrorStatus(bool ignore);

    /**
        Sets how response data will be stored.

        The default storage method @c Storage_Memory collects all response data
        in memory until the request is completed. This is fine for most usage
        scenarios like API calls, loading images, etc. For larger downloads or
        if the response data will be used permanently @c Storage_File instructs
        the request to write the response to a temporary file. This temporary
        file may then be read or moved after the request is complete. The file
        will be downloaded to the system temp directory as returned by
        wxStandardPaths::GetTempDir(). To specify a different directory use
        wxWebSession::SetTempDir().

        Sometimes response data needs to be processed while its downloaded from
        the server. For example if the response is in a format that can be
        parsed piece by piece like XML, JSON or an archive format like ZIP.
        In these cases storing the data in memory or a file before being able
        to process it might not be ideal and @c Storage_None should be set.
        With this storage method the data is only available during the
        @c wxEVT_WEBREQUEST_DATA event calls as soon as it's received from the
        server.
    */
    void SetStorage(Storage storage);

    /**
        Send the request to the server asynchronously.

        Events will be triggered on success or failure.

        @see Cancel()
    */
    void Start();

    /**
        Cancel an active request.
    */
    void Cancel();

    /**
        Returns a response object after a successful request.

        Before sending a request or after a failed request this will return
        @c NULL.
    */
    wxWebResponse* GetResponse();

    /**
        Returns the id specified while creating this request.
    */
    int GetId() const;

    /**
        Returns the current state of the request.
    */
    State GetState() const { return m_state; }
};

/**
    A wxWebResponse allows access to the response sent by the server.

    @since 3.1.2

    @library{wxnet}
    @category{net}

    @see wxWebRequest
*/
class wxWebResponse
{
public:
    /**
        Returns the final URL.
        This URL might be different than the request URL when a redirection
        occurred.
    */
    wxString GetURL() const;

    /**
        Returns a header from the response or an empty string if the header
        could not be found.

        @param name Name of the header field
    */
    wxString GetHeader(const wxString& name) const;

    /**
        Returns the status code returned by the server.
    */
    int GetStatus() const;

    /**
        Returns the status text of the response.
    */
    wxString GetStatusText() const;

    /**
        Returns a stream which represents the response data sent by the server.
    */
    wxInputStream* GetStream();

    /**
        Returns all response data as a string.

        @param conv wxMBConv used to convert the response to a string.
                    If @c NULL, the conversion will be determined by
                    response headers. The default is UTF-8.
    */
    wxString AsString(wxMBConv* conv = NULL) const;
};

/**
    @class wxWebSession

    This class handles session-wide parameters and data used by wxWebRequest
    instances.

    Usually the default session available via wxWebSession::GetDefault()
    should be used. Additional instances might be useful if session separation
    is required. Instances <b>must not</b> be deleted before every active web
    request has finished.

    Every wxWebRequest sharing the same session object will use the same
    cookies. Additionally, an underlying network connection might be kept
    alive to achieve faster additional responses.

    @since 3.1.2

    @library{wxnet}
    @category{net}

    @see wxWebRequest
*/
class wxWebSession
{
public:
    /**
        Constructor for the session

        All requests created by a call to CreateRequest() will use this session
        for communication and to store cookies.
    */
    wxWebSession();

    /**
        Create a new request for the specified URL

        @param url
            The URL of the HTTP resource for this request
        @param id
            Optional id sent with events
    */
    wxWebRequest* CreateRequest(const wxString& url, int id = wxID_ANY);

    /**
        Sets a request header in every wxWebRequest created from this session
        after is has been set.

        A good example for a session-wide request header is the @c User-Agent
        header.

        @param name Name of the header
        @param value String value of the header
    */
    void SetHeader(const wxString& name, const wxString& value);

    /**
        Override the default temporary directory that may be used by the
        session implemention, when required.
    */
    void SetTempDir(const wxString& name);

    /**
        Returns the current temporary directory.

        @see SetTempDir()
    */
    const &wxString GetTempDir() const;

    /**
        Returns the default session
    */
    static wxWebSession& GetDefault();

    /**
        Creates a new wxWebSession object.

        @param backend
            The backend web session implementation to use.

        @return
            The created wxWebSession
    */
    static wxWebSession* New(const wxString& backend = wxWebSessionBackendDefault);

    /**
        Allows the registering of new backend for wxWebSession.

        backend can be used as an argument to New().

        @param backend The name for the new backend to be registered under
        @param factory A shared pointer to the factory which creates the appropriate backend.
    */
    static void RegisterFactory(const wxString& backend, wxSharedPtr<wxWebSessionFactory> factory);

    /**
        Allows to check if the specified backend is available at runtime.

        Usually the default backend should always be available, but e.g. macOS
        before 10.9 does not have the @c NSURLSession implementation available.
    */
    static bool IsBackendAvailable(const wxString& backend);
};

/**
    @class wxWebSessionFactory

    An abstract factory class for creation wxWebSession backends.

    Each implementation of wxWebSession should have its own factory.

    @since 3.1.2

    @library{wxnet}
    @category{net}

    @see wxWebSession
*/
class wxWebSessionFactory
{
public:
    /**
        Creates a new web session object
    */
    virtual wxWebSession* Create() = 0;
};

/**
    @class wxWebRequestEvent

    A web request event sent during or after server communication.

    @since 3.1.2

    @library{wxnet}
    @category{net}

    @see wxWebRequest
*/
class wxWebRequestEvent : public wxEvent
{
public:
    wxWebRequestEvent();
    wxWebRequestEvent(wxEventType type, int id, wxWebRequest::State state,
        wxWebResponse* response = NULL, const wxString& errorDesc = "");

    /**
        Return the current state of the request
    */
    wxWebRequest::State GetState() const;

    /**
        The response with the state set to @c State_Complete or @c NULL for other
        events.
    */
    wxWebResponse* GetResponse() const;

    /**
        A textual error description for a client side error
        in case of wxEVT_WEBREQUEST_FAILED
    */
    const wxString& GetErrorDescription() const;
};

wxEventType wxEVT_WEBREQUEST_STATE;
wxEventType wxEVT_WEBREQUEST_DATA;
wxEventType wxEVT_WEBREQUEST_DOWNLOAD_PROGRESS;
wxEventType wxEVT_WEBREQUEST_UPLOAD_PROGRESS;