/*
 * Copyright (C) 1996-2017 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

/* DEBUG: section 93    eCAP Interface */

#include "squid.h"
#include "adaptation/ecap/Config.h"
#include "adaptation/ecap/Host.h"
#include "adaptation/ecap/ServiceRep.h"
#include "adaptation/ecap/XactionRep.h"
#include "AsyncEngine.h"
#include "base/TextException.h"
#include "Debug.h"
#include "EventLoop.h"

#include <libecap/adapter/service.h>
#include <libecap/common/options.h>
#include <libecap/common/name.h>
#include <libecap/common/named_values.h>
#include <limits>
#include <map>

/// libecap::adapter::services indexed by their URI
typedef std::map<std::string, Adaptation::Ecap::ServiceRep::AdapterService> AdapterServices;
/// all loaded services
static AdapterServices TheServices;
/// configured services producing async transactions
static AdapterServices AsyncServices;

namespace Adaptation
{
namespace Ecap
{

/// wraps Adaptation::Ecap::ServiceConfig to allow eCAP visitors
class ConfigRep: public libecap::Options
{
public:
    typedef Adaptation::Ecap::ServiceConfig Master;
    typedef libecap::Name Name;
    typedef libecap::Area Area;

    ConfigRep(const Master &aMaster);

    // libecap::Options API
    virtual const libecap::Area option(const libecap::Name &name) const;
    virtual void visitEachOption(libecap::NamedValueVisitor &visitor) const;

    const Master &master; ///< the configuration being wrapped
};

/// manages async eCAP transactions
class Engine: public AsyncEngine
{
public:
    /* AsyncEngine API */
    virtual int checkEvents(int timeout);

private:
    void kickAsyncServices(timeval &timeout);
};

} // namespace Ecap
} // namespace Adaptation

Adaptation::Ecap::ConfigRep::ConfigRep(const Master &aMaster): master(aMaster)
{
}

const libecap::Area
Adaptation::Ecap::ConfigRep::option(const libecap::Name &name) const
{
    // we may supply the params we know about, but only when names have host ID
    if (name == metaBypassable)
        return Area(master.bypass ? "1" : "0", 1);

    // TODO: We could build a by-name index, but is it worth it? Good adapters
    // should use visitEachOption() instead, to check for name typos/errors.
    typedef Master::Extensions::const_iterator MECI;
    for (MECI i = master.extensions.begin(); i != master.extensions.end(); ++i) {
        if (name == i->first)
            return Area(i->second.data(), i->second.size());
    }

    return Area();
}

void
Adaptation::Ecap::ConfigRep::visitEachOption(libecap::NamedValueVisitor &visitor) const
{
    // we may supply the params we know about too, but only if we set host ID
    visitor.visit(metaBypassable, Area(master.bypass ? "1" : "0", 1));

    // visit adapter-specific options (i.e., those not recognized by Squid)
    typedef Master::Extensions::const_iterator MECI;
    for (MECI i = master.extensions.begin(); i != master.extensions.end(); ++i)
        visitor.visit(Name(i->first), Area::FromTempString(i->second));
}

/* Adaptation::Ecap::Engine */

int
Adaptation::Ecap::Engine::checkEvents(int)
{
    // Start with the default I/O loop timeout, convert from milliseconds.
    static const struct timeval maxTimeout = {
        EVENT_LOOP_TIMEOUT/1000, // seconds
        (EVENT_LOOP_TIMEOUT % 1000)*1000
    }; // microseconds
    struct timeval timeout = maxTimeout;

    kickAsyncServices(timeout);
    if (timeout.tv_sec == maxTimeout.tv_sec && timeout.tv_usec == maxTimeout.tv_usec)
        return EVENT_IDLE;

    debugs(93, 7, "timeout: " << timeout.tv_sec << "s+" << timeout.tv_usec << "us");

    // convert back to milliseconds, avoiding int overflows
    if (timeout.tv_sec >= std::numeric_limits<int>::max()/1000 - 1000)
        return std::numeric_limits<int>::max();
    else
        return timeout.tv_sec*1000 + timeout.tv_usec/1000;
}

/// resumes async transactions (if any) and returns true if they set a timeout
void
Adaptation::Ecap::Engine::kickAsyncServices(timeval &timeout)
{
    if (AsyncServices.empty())
        return;

    debugs(93, 3, "async services: " << AsyncServices.size());

    // Activate waiting async transactions, if any.
    typedef AdapterServices::iterator ASI;
    for (ASI s = AsyncServices.begin(); s != AsyncServices.end(); ++s) {
        assert(s->second);
        s->second->resume(); // may call Ecap::Xaction::resume()
    }

    // Give services a chance to decrease the default timeout.
    for (ASI s = AsyncServices.begin(); s != AsyncServices.end(); ++s) {
        s->second->suspend(timeout);
    }
}

/* Adaptation::Ecap::ServiceRep */

Adaptation::Ecap::ServiceRep::ServiceRep(const ServiceConfigPointer &cfg):
/*AsyncJob("Adaptation::Ecap::ServiceRep"),*/ Adaptation::Service(cfg),
    isDetached(false)
{
}

Adaptation::Ecap::ServiceRep::~ServiceRep()
{
}

void Adaptation::Ecap::ServiceRep::noteFailure()
{
    assert(false); // XXX: should this be ICAP-specific?
}

void
Adaptation::Ecap::ServiceRep::finalize()
{
    Adaptation::Service::finalize();
    theService = FindAdapterService(cfg().uri);
    if (theService) {
        try {
            tryConfigureAndStart();
            Must(up());
        } catch (const std::exception &e) { // standardized exceptions
            if (!handleFinalizeFailure(e.what()))
                throw; // rethrow for upper layers to handle
        } catch (...) { // all other exceptions
            if (!handleFinalizeFailure("unrecognized exception"))
                throw; // rethrow for upper layers to handle
        }
        return; // success or handled exception
    } else {
        debugs(93,DBG_IMPORTANT, "WARNING: configured ecap_service was not loaded: " << cfg().uri);
    }
}

/// attempts to configure and start eCAP service; the caller handles exceptions
void
Adaptation::Ecap::ServiceRep::tryConfigureAndStart()
{
    debugs(93,2, HERE << "configuring eCAP service: " << theService->uri());
    const ConfigRep cfgRep(dynamic_cast<const ServiceConfig&>(cfg()));
    theService->configure(cfgRep);

    debugs(93,DBG_IMPORTANT, "Starting eCAP service: " << theService->uri());
    theService->start();

    if (theService->makesAsyncXactions()) {
        AsyncServices[theService->uri()] = theService;
        debugs(93, 5, "asyncs: " << AsyncServices.size());
    }
}

/// handles failures while configuring or starting an eCAP service;
/// returns false if the error must be propagated to higher levels
bool
Adaptation::Ecap::ServiceRep::handleFinalizeFailure(const char *error)
{
    const bool salvage = cfg().bypass;
    const int level = salvage ? DBG_IMPORTANT :DBG_CRITICAL;
    const char *kind = salvage ? "optional" : "essential";
    debugs(93, level, "ERROR: failed to start " << kind << " eCAP service: " <<
           cfg().uri << ":\n" << error);

    if (!salvage)
        return false; // we cannot handle the problem; the caller may escalate

    // make up() false, preventing new adaptation requests and enabling bypass
    theService.reset();
    debugs(93, level, "WARNING: " << kind << " eCAP service is " <<
           "down after initialization failure: " << cfg().uri);

    return true; // tell the caller to ignore the problem because we handled it
}

bool Adaptation::Ecap::ServiceRep::probed() const
{
    return true; // we "probe" the adapter in finalize().
}

bool Adaptation::Ecap::ServiceRep::up() const
{
    return theService;
}

bool Adaptation::Ecap::ServiceRep::wantsUrl(const String &urlPath) const
{
    Must(up());
    return theService->wantsUrl(urlPath.termedBuf());
}

Adaptation::Initiate *
Adaptation::Ecap::ServiceRep::makeXactLauncher(HttpMsg *virgin,
        HttpRequest *cause, AccessLogEntry::Pointer &alp)
{
    Must(up());

    // register now because (a) we need EventLoop::Running and (b) we do not
    // want to add more main loop overheads unless an async service is used.
    static AsyncEngine *TheEngine = NULL;
    if (AsyncServices.size() && !TheEngine && EventLoop::Running) {
        TheEngine = new Engine;
        EventLoop::Running->registerEngine(TheEngine);
        debugs(93, 3, "asyncs: " << AsyncServices.size() << ' ' << TheEngine);
    }

    XactionRep *rep = new XactionRep(virgin, cause, alp, Pointer(this));
    XactionRep::AdapterXaction x(theService->makeXaction(rep));
    rep->master(x);
    return rep;
}

// returns a temporary string depicting service status, for debugging
const char *Adaptation::Ecap::ServiceRep::status() const
{
    // TODO: move generic stuff from eCAP and ICAP to Adaptation
    static MemBuf buf;

    buf.reset();
    buf.append("[", 1);

    if (up())
        buf.append("up", 2);
    else
        buf.append("down", 4);

    if (detached())
        buf.append(",detached", 9);

    buf.append("]", 1);
    buf.terminate();

    return buf.content();
}

void Adaptation::Ecap::ServiceRep::detach()
{
    isDetached = true;
}

bool Adaptation::Ecap::ServiceRep::detached() const
{
    return isDetached;
}

Adaptation::Ecap::ServiceRep::AdapterService
Adaptation::Ecap::FindAdapterService(const String& serviceUri)
{
    AdapterServices::const_iterator pos = TheServices.find(serviceUri.termedBuf());
    if (pos != TheServices.end()) {
        Must(pos->second);
        return pos->second;
    }
    return ServiceRep::AdapterService();
}

void
Adaptation::Ecap::RegisterAdapterService(const Adaptation::Ecap::ServiceRep::AdapterService& adapterService)
{
    TheServices[adapterService->uri()] = adapterService; // may update old one
    debugs(93, 3, "stored eCAP module service: " << adapterService->uri());
    // We do not update AsyncServices here in case they are not configured.
}

void
Adaptation::Ecap::UnregisterAdapterService(const String& serviceUri)
{
    if (TheServices.erase(serviceUri.termedBuf())) {
        debugs(93, 3, "unregistered eCAP module service: " << serviceUri);
        AsyncServices.erase(serviceUri.termedBuf()); // no-op for non-async
        return;
    }
    debugs(93, 3, "failed to unregister eCAP module service: " << serviceUri);
}

void
Adaptation::Ecap::CheckUnusedAdapterServices(const Adaptation::Services& cfgs)
{
    typedef AdapterServices::const_iterator ASCI;
    for (ASCI loaded = TheServices.begin(); loaded != TheServices.end();
            ++loaded) {
        bool found = false;
        for (Services::const_iterator cfged = cfgs.begin();
                cfged != cfgs.end() && !found; ++cfged) {
            found = (*cfged)->cfg().uri == loaded->second->uri().c_str();
        }
        if (!found)
            debugs(93, DBG_IMPORTANT, "Warning: loaded eCAP service has no matching " <<
                   "ecap_service config option: " << loaded->second->uri());
    }
}