/////////////////////////////////////////////////////////////////////////////
// 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 system's
    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 in an event handler function of some window (i.e. @c this in
    the example below is a wxWindow pointer):

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

        if ( !request.IsOk() ) {
            // This is not expected, but handle the error somehow.
        }

        // Bind state event
        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 successfully downloaded");

                    ... do something with it ...

                    break;
                }
                // Request failed
                case wxWebRequest::State_Failed:
                    wxLogError("Could not load logo: %s", evt.GetErrorDescription());
                    break;
            }

        });

        // Start the request
        request.Start();
    @endcode

    @section apple_http macOS and iOS App Transport Security

    Starting with macOS 10.11 and iOS 9 an application cannot create insecure
    connections (this includes HTTP and unverified HTTPS). You have to include
    additional fields in your Info.plist to enable such connections.
    For further details see the documentation on NSAppTransportSecurity
    <a target=_new href="https://developer.apple.com/documentation/bundleresources/information_property_list/nsapptransportsecurity">here</a>

    @section descriptions Implementation Descriptions

    The following APIs are used per platform, additional details
    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.
    @endEventTable

    @since 3.1.5

    @library{wxnet}
    @category{net}

    @see wxWebResponse, wxWebSession
*/
class wxWebRequest
{
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 is currently unauthorized.

            Calling GetAuthChallenge() returns a challenge object with further
            details and calling SetCredentials() on this object will retry the
            request using these credentials.
        */
        State_Unauthorized,

        /**
            The request is about to start.

            An event notifying about the switch to this state is generated when
            Start() is called (unless an error occurs, in which case the state
            becomes State_Failed instead). Handling this event allows to do
            something right before the asynchronous request actually starts.
         */
        State_Active,

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

            The HTTP status code returned by wxWebResponse::GetStatus() will be
            in 100-399 range, and typically 200.
         */
        State_Completed,

        /**
            The request failed.

            This can happen either because the request couldn't be performed at
            all (e.g. a connection error) or if the server returned an HTTP
            error. In the former case wxWebResponse::GetStatus() returns 0,
            while in the latter it returns a value in 400-599 range.
         */
        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.

            It can be later retrieved using wxWebResponse::AsString() or
            wxWebResponse::GetStream().
         */
        Storage_Memory,

        /**
            The data is written to a file on disk as it is received.

            This file can be later read from using wxWebResponse::GetStream()
            or otherwise processed using wxWebRequestEvent::GetDataFile().
         */
        Storage_File,

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

            Data can be retrieved using wxWebRequestEvent::GetDataBuffer() and
            wxWebRequestEvent::GetDataSize() methods from wxEVT_WEBREQUEST_DATA
            handler.
        */
        Storage_None
    };

    /**
        Default constructor creates an invalid object.

        Initialize it by assigning wxWebSession::CreateRequest() to it before
        using it.

        @see IsOk()
    */
    wxWebRequest();

    /**
        Check if the object is valid.

        If the object is invalid, it must be assigned a valid request before
        any other methods can be used (with the exception of GetNativeHandle()).
    */
    bool IsOk() const;

    /**
        Return the native handle corresponding to this request object.

        @c wxWebRequestHandle is an opaque type containing a value of the
        following type according to the backend being used:

        - For WinHTTP backend, this is @c HINTERNET request handle.
        - For CURL backend, this is a @c CURL struct pointer.
        - For macOS backend, this is @c NSURLSessionTask object pointer.

        Note that this function returns a valid value only after the request is
        started successfully using Start(). Notably, it is guaranteed to return
        a valid value when handling wxWebRequestEvent corresponding to the
        switch to @c State_Active.

        @see wxWebSession::GetNativeHandle()
     */
    wxWebRequestHandle GetNativeHandle() const;

    /**
        Send the request to the server asynchronously.

        Events will be triggered on success or failure.

        The current state must be @c State_Idle, already started requests can't
        be started again.

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

    /**
        Cancel an active request.

        Note that cancelling is asynchronous, so the application needs to wait
        until the request state becomes @c State_Cancelled to know when the
        request was really cancelled.

        Request must be active when Cancel() is called, i.e. the current state
        can't be @c State_Idle. However, because it can be difficult to avoid
        doing it in some circumstances, Cancel() may be called multiple times
        and only a single wxWebRequestEvent will be sent even in this case.
    */
    void Cancel();

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

        Before sending a request or after a failed request this will return
        an invalid response object, i.e. such that wxWebResponse::IsOk()
        returns @NULL.
    */
    wxWebResponse GetResponse() const;

    /**
        Returns the current authentication challenge object while the request
        is in @c State_Unauthorized.
    */
    wxWebAuthChallenge GetAuthChallenge() const;

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

    /** @name Request options
        Methods that set options before starting the request
    */
    ///@{
    /**
        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.

        Example of use:
        @code
        std::unique_ptr<wxInputStream> stream(new wxFileInputStream("some_file.dat"));
        if ( !stream->IsOk() ) {
            // Handle error (due to e.g. file not found) here.
            ...
            return;
        }
        request.SetData(stream.release(), "application/octet-stream")
        @endcode

        @param dataStream
            The data in this stream will be posted as the request body. The
            pointer may be @NULL, which will result in sending 0 bytes of data,
            but if not empty, should be valid, i.e. wxInputStream::IsOk() must
            return @true. This object takes ownership of the passed in pointer
            and will delete it, i.e. the pointer must be heap-allocated.
        @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.

        @return @false if @a dataStream is not-empty but invalid or if @a
            dataSize is not specified and the attempt to determine stream size
            failed; @true in all the other cases.
    */
    bool SetData(wxInputStream* dataStream,
        const wxString& contentType, wxFileOffset dataSize = wxInvalidOffset);

    /**
        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);

    /**
        Disable SSL certificate verification.

        This can be used to connect to self signed servers or other invalid
        SSL connections. Disabling verification makes the communication
        insecure.
    */
    void DisablePeerVerify(bool disable = true);

    /**
        Returns if peer verification has been disabled.

        @see DisablePeerVerify()
    */
    bool IsPeerVerifyDisabled() const;
    ///@}

    /** @name Progress methods
        Methods that describe the requests progress
    */
    ///@{
    /**
        Returns the current state of the request.
    */
    State GetState() const;

    /**
        Returns the number of bytes sent to the server.

        This value grows monotonically from 0 to GetBytesExpectedToSend().
     */
    wxFileOffset GetBytesSent() const;

    /**
        Returns the total number of bytes expected to be sent to the server.

        This value stays unchanged throughout the request duration.
     */
    wxFileOffset GetBytesExpectedToSend() const;

    /**
        Returns the number of bytes received from the server.

        This value grows monotonically from 0 to GetBytesExpectedToReceive()
        (unless it is unknown).
     */
    wxFileOffset GetBytesReceived() const;

    /**
        Returns the number of bytes expected to be received from the server.

        This value is based on the @c Content-Length header, if none is found
        it will return -1.

        @see wxWebResponse::GetContentLength()
    */
    wxFileOffset GetBytesExpectedToReceive() const;
    ///@}
};

/**
    Authentication challenge information available via
    wxWebRequest::GetAuthChallenge().

    Use SetCredentials() to provide user credentials, e.g.
    @code
        if ( request.GetState() == wxWebRequest::State_Unauthorized )
        {
            wxWebCredentials cred("me", wxSecretValue("s3krit"));
            request.GetAuthChallenge().SetCredentials(cred);
        }
    @endcode
*/
class wxWebAuthChallenge
{
public:
    enum Source
    {
        /// The server requested authentication
        Source_Server,

        /// A proxy requested authentication
        Source_Proxy
    };

    /**
        Returns which source requested credentials with this challenge.
    */
    Source GetSource() const;

    /**
        Used to provide user credentials to the authentication challenge.

        @see wxWebCredentials
    */
    void SetCredentials(const wxWebCredentials& cred);
};

/**
    Simple class containing the username and password to use for authenticating.

    @since 3.1.5

    @library{wxnet}
    @category{net}

    @see wxWebAuthChallenge
 */
class wxWebCredentials
{
public:
    /**
        Create the new credentials object.

        Note that the password is a wxSecretValue object, to construct it from
        a string you need to explicitly use wxSecretValue ctor.
     */
    wxWebCredentials(const wxString& user = wxString(),
                     const wxSecretValue& password = wxSecretValue());

    /// Return the user.
    const wxString& GetUser() const;

    /**
        Return the password.

        @see wxSecretString
     */
    const wxSecretValue& GetPassword() const;
};

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

    @since 3.1.5

    @library{wxnet}
    @category{net}

    @see wxWebRequest
*/
class wxWebResponse
{
public:
    /**
        Default constructor creates an invalid object.

        Initialize it by assigning wxWebRequest::GetResponse() to it before
        using it.

        @see IsOk()
    */
    wxWebResponse();

    /**
        Check if the object is valid.

        No other methods can be used if this function returns @false.
    */
    bool IsOk() const;

    /**
        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;

    /**
        Get the length of returned data if available.

        Returns the value specified in the @c Content-Length: response header
        of @c -1 if not available.
     */
    wxFileOffset GetContentLength() const;

    /**
        Returns the MIME type of the response (if available).
    */
    wxString GetMimeType() 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 a suggested filename for the response data.
    */
    wxString GetSuggestedFileName() const;

    /**
        Returns the full path of the file to which data is being saved.

        This is only valid when storage mode is @c Storage_File.
     */
    wxString GetDataFile() const;

    /**
        Returns all response data as a string.

        This is mostly useful for debugging or diagnostics.
    */
    wxString AsString() const;
};

/**
    @class wxWebSession

    Session allows creating wxWebRequest objects used for the actual HTTP
    requests.

    It also 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 3.1.5

    @library{wxnet}
    @category{net}

    @see wxWebRequest
*/
class wxWebSession
{
public:
    /**
        Create a new request for the specified URL.

        The specified objects will be notified via wxWebRequestEvent objects
        when the request state changes, e.g. when it is completed. It must be
        specified and its lifetime must be long enough to last until the
        request is completed. In particular, if the handler is a top-level
        window, the request must be cancelled before the window can be closed
        and destroyed.

        @param handler
            The handler object to notify, must be non-@NULL.
        @param url
            The URL of the HTTP resource for this request
        @param id
            Optional id sent with events
        @return
            The new request object, use wxWebRequest::IsOk() to check if its
            creation has succeeded.
    */
    wxWebRequest
    CreateRequest(wxEvtHandler* handler, const wxString& url, int id = wxID_ANY);

    /**
        Retrieve the version information about the implementation library used
        by this session.
    */
    virtual wxVersionInfo GetLibraryVersionInfo();

    /**
        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.

        Calling this function with the same header name again replaces the
        previously used value.

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

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

    /**
        Returns the current temporary directory.

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

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

    /**
        Creates a new wxWebSession object.

        @a backend may be specified explicitly by using of the predefined @c
        wxWebSessionBackendWinHTTP, @c wxWebSessionBackendURLSession or @c
        wxWebSessionBackendCURL constants to select the corresponding backend
        or left empty to select the default backend. The default depends on
        the current platform: WinHTTP-based implementation is used under MSW,
        NSURLSession-based one under macOS and libcurl-based otherwise.

        Further, if @c WXWEBREQUEST_BACKEND environment variable is defined, it
        overrides the default backend selection, allowing to force the use of
        libcurl-based implementation by default under MSW or macOS platforms,
        for example.

        Use IsOpened() to check if the session creation succeeded.

        @param backend
            The backend web session implementation to use or empty to use the
            default implementation as described above.

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

    /**
        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);

    /**
        Return the native handle corresponding to this session object.

        @c wxWebSessionHandle is an opaque type containing a value of the
        following type according to the backend being used:

        - For WinHTTP backend, this is @c HINTERNET session handle.
        - For CURL backend, this is a @c CURLM struct pointer.
        - For macOS backend, this is @c NSURLSession object pointer.

        @see wxWebRequest::GetNativeHandle()
     */
    wxWebSessionHandle GetNativeHandle() const;

    /**
        Return true if the session was successfully opened and can be used.
    */
    bool IsOpened() const;

    /**
        Close the session.

        This frees any resources associated with the session and puts it in an
        invalid state. Another session object can be assigned to it later to
        allow using this object again.
     */
    void Close();
};

/**
    @class wxWebRequestEvent

    A web request event sent during or after server communication.

    @since 3.1.5

    @library{wxnet}
    @category{net,events}

    @see wxWebRequest
*/
class wxWebRequestEvent : public wxEvent
{
public:
    /**
        Return the current state of the request
    */
    wxWebRequest::State GetState() const;

    /**
        Returns a reference to the @c wxWebRequest object which initiated this event.

        @since 3.1.6
    */
    const wxWebRequest& GetRequest() const;

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

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

    /**
        Returns the full path of a temporary file containing the response data
        when the state is @c State_Completed and storage is @c Storage_File.

        The file will be removed after the event handlers are called. You can
        move the file to a location of your choice if you want to process the
        contents outside the event handler.
    */
    const wxString& GetDataFile() const;

    /**
        Only for @c wxEVT_WEBREQUEST_DATA events. The buffer is only valid
        inside the event handler.
    */
    ///@{
    const void* GetDataBuffer() const;

    size_t GetDataSize() const;
    ///@}
};

wxEventType wxEVT_WEBREQUEST_STATE;
wxEventType wxEVT_WEBREQUEST_DATA;