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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
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 * The Original Code is mozilla.org code.
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 * Contributor(s):
 *   Darin Fisher <darin@meer.net>
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#include "nsISupports.idl"

interface nsICancelable;
interface nsIProtocolProxyCallback;
interface nsIProtocolProxyFilter;
interface nsIProxyInfo;
interface nsIChannel;
interface nsIURI;

/**
 * nsIProtocolProxyService provides methods to access information about
 * various network proxies.
 *
 * @status UNDER_REVIEW
 */
[scriptable, uuid(e38ab577-786e-4a7f-936b-7ae4c7d877b2)]
interface nsIProtocolProxyService : nsISupports
{
    /**
     * This flag may be passed to the resolve method to request that it fail
     * instead of block the calling thread.  Proxy Auto Config (PAC) may
     * perform a synchronous DNS query, which may not return immediately.  So,
     * calling resolve without this flag may result in locking up the calling
     * thread for a lengthy period of time.
     *
     * By passing this flag to resolve, one can failover to asyncResolve to
     * avoid locking up the calling thread if a PAC query is required.
     *
     * When this flag is passed to resolve, resolve may throw the exception
     * NS_BASE_STREAM_WOULD_BLOCK to indicate that it failed due to this flag
     * being present.
     */
    const unsigned long RESOLVE_NON_BLOCKING = 1;
    
    /**
     * This method returns a nsIProxyInfo instance that identifies a proxy to
     * be used for loading the given URI.  Otherwise, this method returns null
     * indicating that a direct connection should be used.
     *
     * @param aURI
     *        The URI to test.
     * @param aFlags
     *        A bit-wise OR of the RESOLVE_ flags defined above.  Pass 0 to
     *        specify the default behavior.
     *
     * NOTE: If this proxy is unavailable, getFailoverForProxy may be called
     * to determine the correct secondary proxy to be used.
     *
     * NOTE: If the protocol handler for the given URI supports
     * nsIProxiedProtocolHandler, then the nsIProxyInfo instance returned from
     * resolve may be passed to the newProxiedChannel method to create a
     * nsIChannel to the given URI that uses the specified proxy.
     *
     * NOTE: However, if the nsIProxyInfo type is "http", then it means that
     * the given URI should be loaded using the HTTP protocol handler, which
     * also supports nsIProxiedProtocolHandler.
     *
     * NOTE: If PAC is configured, and the PAC file has not yet been loaded,
     * then this method will return a nsIProxyInfo instance with a type of
     * "unknown" to indicate to the consumer that asyncResolve should be used
     * to wait for the PAC file to finish loading.  Otherwise, the consumer
     * may choose to treat the result as type "direct" if desired.
     *
     * @see nsIProxiedProtocolHandler::newProxiedChannel 
     */
    nsIProxyInfo resolve(in nsIURI aURI, in unsigned long aFlags);

    /**
     * This method is an asychronous version of the resolve method.  Unlike
     * resolve, this method is guaranteed not to block the calling thread
     * waiting for DNS queries to complete.  This method is intended as a
     * substitute for resolve when the result is not needed immediately.
     *
     * @param aURI
     *        The URI to test.
     * @param aFlags
     *        A bit-wise OR of the RESOLVE_ flags defined above.  Pass 0 to
     *        specify the default behavior.
     * @param aCallback
     *        The object to be notified when the result is available.
     *
     * @return An object that can be used to cancel the asychronous operation.
     */
    nsICancelable asyncResolve(in nsIURI aURI, in unsigned long aFlags,
                               in nsIProtocolProxyCallback aCallback);

    /**
     * This method may be called to construct a nsIProxyInfo instance from
     * the given parameters.  This method may be useful in conjunction with
     * nsISocketTransportService::createTransport for creating, for example,
     * a SOCKS connection.
     *
     * @param aType
     *        The proxy type.  This is a string value that identifies the proxy
     *        type.  Standard values include:
     *          "http"    - specifies a HTTP proxy
     *          "socks"   - specifies a SOCKS version 5 proxy
     *          "socks4"  - specifies a SOCKS version 4 proxy
     *          "direct"  - specifies a direct connection (useful for failover)
     *        The type name is case-insensitive.  Other string values may be
     *        possible.
     * @param aHost
     *        The proxy hostname or IP address.
     * @param aPort
     *        The proxy port.
     * @param aFlags
     *        Flags associated with this connection.  See nsIProxyInfo.idl
     *        for currently defined flags.
     * @param aFailoverTimeout
     *        Specifies the length of time (in seconds) to ignore this proxy if
     *        this proxy fails.  Pass PR_UINT32_MAX to specify the default
     *        timeout value, causing nsIProxyInfo::failoverTimeout to be
     *        assigned the default value.
     * @param aFailoverProxy
     *        Specifies the next proxy to try if this proxy fails.  This
     *        parameter may be null.
     */
    nsIProxyInfo newProxyInfo(in ACString aType, in AUTF8String aHost,
                              in long aPort, in unsigned long aFlags,
                              in unsigned long aFailoverTimeout,
                              in nsIProxyInfo aFailoverProxy);

    /**
     * If the proxy identified by aProxyInfo is unavailable for some reason,
     * this method may be called to access an alternate proxy that may be used
     * instead.  As a side-effect, this method may affect future result values
     * from resolve/asyncResolve as well as from getFailoverForProxy.
     *
     * @param aProxyInfo
     *        The proxy that was unavailable.
     * @param aURI
     *        The URI that was originally passed to resolve/asyncResolve.
     * @param aReason
     *        The error code corresponding to the proxy failure.  This value
     *        may be used to tune the delay before this proxy is used again.
     *
     * @throw NS_ERROR_NOT_AVAILABLE if there is no alternate proxy available.
     */
    nsIProxyInfo getFailoverForProxy(in nsIProxyInfo aProxyInfo,
                                     in nsIURI       aURI,
                                     in nsresult     aReason);

    /**
     * This method may be used to register a proxy filter instance.  Each proxy
     * filter is registered with an associated position that determines the
     * order in which the filters are applied (starting from position 0).  When
     * resolve/asyncResolve is called, it generates a list of proxies for the
     * given URI, and then it applies the proxy filters.  The filters have the
     * opportunity to modify the list of proxies.
     *
     * If two filters register for the same position, then the filters will be
     * visited in the order in which they were registered.
     *
     * If the filter is already registered, then its position will be updated.
     *
     * After filters have been run, any disabled or disallowed proxies will be
     * removed from the list.  A proxy is disabled if it had previously failed-
     * over to another proxy (see getFailoverForProxy).  A proxy is disallowed,
     * for example, if it is a HTTP proxy and the nsIProtocolHandler for the
     * queried URI does not permit proxying via HTTP.
     *
     * If a nsIProtocolHandler disallows all proxying, then filters will never
     * have a chance to intercept proxy requests for such URLs.
     *
     * @param aFilter
     *        The nsIProtocolProxyFilter instance to be registered.
     * @param aPosition
     *        The position of the filter.
     *
     * NOTE: It is possible to construct filters that compete with one another
     * in undesirable ways.  This API does not attempt to protect against such
     * problems.  It is recommended that any extensions that choose to call
     * this method make their position value configurable at runtime (perhaps
     * via the preferences service).
     */
    void registerFilter(in nsIProtocolProxyFilter aFilter,
                        in unsigned long aPosition);

    /**
     * This method may be used to unregister a proxy filter instance.  All
     * filters will be automatically unregistered at XPCOM shutdown.
     *
     * @param aFilter
     *        The nsIProtocolProxyFilter instance to be unregistered.
     */
    void unregisterFilter(in nsIProtocolProxyFilter aFilter);
};
