// Copyright (C) 2013  Internet Systems Consortium, Inc. ("ISC")
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

#include <util/hooks/callout_handle.h>
#include <util/hooks/callout_manager.h>

#include <algorithm>
#include <functional>
#include <utility>

using namespace std;
using namespace isc::util;

namespace isc {
namespace util {

// Register a callout for a particular library.

void
CalloutManager::registerCallout(int libindex, const std::string& name,
                                CalloutPtr callout) {
    // Get the index associated with this hook (validating the name in the
    // process).
    int hook_index = hooks_->getIndex(name);

    // Iterate through the callout vector for the hook from start to end,
    // looking for the first entry where the library index is greater than
    // the present index.
    for (CalloutVector::iterator i = hook_vector_[hook_index].begin();
         i != hook_vector_[hook_index].end(); ++i) {
        if (i->first > libindex) {
            // Found an element whose library number is greater than ours,
            // so insert the new element ahead of this one.
            hook_vector_[hook_index].insert(i,
                                            std::make_pair(libindex, callout));
            return;
        }
    }

    // Reach the end of the vector, so no element in the (possibly empty)
    // set of callouts with a library index greater that the one related to
    // this callout, insert at the end.
    hook_vector_[hook_index].push_back(std::make_pair(libindex, callout));
}

// Check if callouts are present for a given hook index.

bool
CalloutManager::calloutsPresent(int hook_index) const {
    // Validate the hook index.
    checkHookIndex(hook_index);

    // Valid, so are there any callouts associated with that hook?
    return (!hook_vector_[hook_index].empty());
}

// Call all the callouts for a given hook.

int
CalloutManager::callCallouts(int hook_index, CalloutHandle& callout_handle) {
    // Validate the hook index.
    checkHookIndex(hook_index);

    // Clear the "skip" flag so we don't carry state from a previous
    // call.
    callout_handle.setSkip(false);

    // Call all the callouts, stopping if the "skip" flag is set or if a
    // non-zero status is returned.
    int status = 0;
    for (CalloutVector::const_iterator i = hook_vector_[hook_index].begin();
         i != hook_vector_[hook_index].end() && (status == 0); ++i) {
        status = (*i->second)(callout_handle);
    }

    return (status);
}

// Deregister a callout registered by a library on a particular hook.

bool
CalloutManager::deregisterCallout(int library_index, const std::string& name,
                                  CalloutPtr callout) {

    // Get the index associated with this hook (validating the name in the
    // process).
    int hook_index = hooks_->getIndex(name);

    /// Construct a CalloutEntry matching the specified library and the callout
    /// we want to remove.
    CalloutEntry target(library_index, callout);

    /// To decide if any entries were removed, we'll record the initial size
    /// of the callout vector for the hook, and compare it with the size after
    /// the removal.
    size_t initial_size = hook_vector_[hook_index].size();

    // The next bit is standard STL (see "Item 33" in "Effective STL" by
    // Scott Meyers).
    //
    // remove_if reorders the hook vector so that all items not matching
    // the predicate are at the start of the vector and returns a pointer
    // to the next element. (In this case, the predicate is that the item
    // is equal to the value of the passed callout.)  The erase() call
    // removes everything from that element to the end of the vector, i.e.
    // all the matching elements.
    hook_vector_[hook_index].erase(remove_if(hook_vector_[hook_index].begin(),
                                             hook_vector_[hook_index].end(),
                                             bind1st(equal_to<CalloutEntry>(),
                                                     target)),
                                   hook_vector_[hook_index].end());

    // Return an indication of whether anything was removed.
    return (initial_size != hook_vector_[hook_index].size());
}

// Deregister all callouts on a given hook.

bool
CalloutManager::deregisterAllCallouts(int library_index,
                                      const std::string& name) {

    // Get the index associated with this hook (validating the name in the
    // process).
    int hook_index = hooks_->getIndex(name);

    /// Construct a CalloutEntry matching the specified library we want to
    /// remove (the callout pointer is NULL as we are not checking that).
    CalloutEntry target(library_index, NULL);

    /// To decide if any entries were removed, we'll record the initial size
    /// of the callout vector for the hook, and compare it with the size after
    /// the removal.
    size_t initial_size = hook_vector_[hook_index].size();

    // Remove all callouts matching this library.
    hook_vector_[hook_index].erase(remove_if(hook_vector_[hook_index].begin(),
                                             hook_vector_[hook_index].end(),
                                             bind1st(CalloutLibraryEqual(),
                                                     target)),
                                   hook_vector_[hook_index].end());

    // Return an indication of whether anything was removed.
    return (initial_size != hook_vector_[hook_index].size());
}

// CalloutManager methods.

// Return pointer to the current library handle.

boost::shared_ptr<LibraryHandle>
CalloutManager::createHandle() {
    // Index is equal to the size of the current collection of handles
    // (guarantees that every handle has a unique index, and that index
    // is a pointer to the handle in the collection of handles.)
    boost::shared_ptr<LibraryHandle> handle(new LibraryHandle(handles_.size(),
                                                              this));

    // Add to the current collection of handles.
    handles_.push_back(handle);

    return (handle);
}

} // namespace util
} // namespace isc