/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

#include <navmgr.hxx>
#include <wrtsh.hxx>
#include <sfx2/bindings.hxx>
#include <sfx2/viewfrm.hxx>
#include <vcl/svapp.hxx>
#include <cmdid.h>
#include <view.hxx>
#include <doc.hxx>
#include <unocrsr.hxx>

// This method positions the cursor to the position rPos.

void SwNavigationMgr::GotoSwPosition(const SwPosition &rPos) {

    // EnterStdMode() prevents the cursor to 'block' the current
    // shell when it should move from the image back to the normal shell
    m_rMyShell.EnterStdMode();
    m_rMyShell.StartAllAction();
    // cursor consists of two SwPositions: Point and Mark.
    // Such a pair is called a PaM. SwPaM is derived from SwRing.
    // The Ring contains the single regions of a multi-selection.
    SwPaM* pPaM = m_rMyShell.GetCursor();

    if(pPaM->HasMark())
        pPaM->DeleteMark();      // If there was a selection, get rid of it
    *pPaM->GetPoint() = rPos;    // Position Cursor

    m_rMyShell.EndAllAction();
}

// Ctor for the SwNavigationMgr class
// Sets the shell to the current shell
// and the index of the current position to 0

SwNavigationMgr::SwNavigationMgr(SwWrtShell & rShell)
    : m_nCurrent(0), m_rMyShell(rShell)
{
}

SwNavigationMgr::~SwNavigationMgr()
{
    SolarMutexGuard g;
    for (auto & it : m_entries)
    {
        EndListening(it->m_aNotifier);
    }
    m_entries.clear();
}

void SwNavigationMgr::Notify(SfxBroadcaster& rBC, const SfxHint& rHint)
{
    // our cursors may now spontaneously self-destruct: remove from
    // m_entries if that happens
    if (rHint.GetId() == SfxHintId::SwUnoCursorHint)
    {
        auto it = std::find_if(m_entries.begin(), m_entries.end(),
            [&rBC](const sw::UnoCursorPointer& rItem) { return !rItem || &rBC == &rItem->m_aNotifier; });
        if (it != m_entries.end())
        {
            EndListening(rBC);
            m_entries.erase(it);
        }
    }
}

// This method is used by the navigation shell - defined in sw/source/uibase/inc/navsh.hxx
// and implemented in sw/source/uibase/shells/navsh.cxx
// It is called when we want to check if the back button should be enabled or not.
// The back button should be enabled only if there are some entries in the navigation history

bool SwNavigationMgr::backEnabled() {
    return (m_nCurrent > 0);
}

// Similar to backEnabled() method.
// The forward button should be enabled if we ever clicked back
// Due to the implementation of the navigation class, this is when the
// current position within the navigation history entries in not the last one
// i.e. when the m_nCurrent index is not at the end of the m_entries vector

bool SwNavigationMgr::forwardEnabled() {
    return m_nCurrent+1 < m_entries.size();
}

// The goBack() method positions the cursor to the previous entry in the navigation history
// If there was no history to go forward to, it adds the current position of the cursor
// to the history so we could go forward to where we came from

void SwNavigationMgr::goBack()  {

    // Although the button should be disabled whenever the backEnabled() returns false,
    // the UI is sometimes not as responsive as we would like it to be :)
    // this check prevents segmentation faults and in this way the class is not relying on the UI

    if (!backEnabled())        return;

    /* Trying to get the current cursor */
    SwPaM* pPaM = m_rMyShell.GetCursor();
    if (!pPaM) {
        return;
    }
    // This flag will be used to manually refresh the buttons

    bool bForwardWasDisabled = !forwardEnabled();

    // If we're going backwards in our history, but the current location is not
    // in the history then we need to add *here* to it so that we can "go
    // forward" to here again.

    if (bForwardWasDisabled) {

        // the cursor consists of two SwPositions: Point and Mark.
        // We are adding the current Point to the navigation history
        // so we could later navigate forward to it

        // The addEntry() method returns true iff we should decrement
        // the index before navigating back

        if (addEntry(*pPaM->GetPoint()) ) {
            m_nCurrent--;
        }
    }
    m_nCurrent--;
    // Position cursor to appropriate navigation history entry
    GotoSwPosition(*m_entries[m_nCurrent]->GetPoint());
    // Refresh the buttons
    if (bForwardWasDisabled)
        m_rMyShell.GetView().GetViewFrame().GetBindings().Invalidate(FN_NAVIGATION_FORWARD);
    if (!backEnabled())
        m_rMyShell.GetView().GetViewFrame().GetBindings().Invalidate(FN_NAVIGATION_BACK);
}

// The goForward() method positions the cursor to the next entry in the navigation history

void SwNavigationMgr::goForward() {

    // Although the button should be disabled whenever the backForward() returns false,
    // the UI is sometimes not as responsive as we would like it to be :)
    // this check prevents segmentation faults and in this way the class is not relying on the UI

    if (!forwardEnabled())        return;

    // This flag will be used to manually refresh the buttons
    bool bBackWasDisabled = !backEnabled();
    // The current index is positioned at the current entry in the navigation history
    // We have to increment it to go to the next entry
    m_nCurrent++;
    GotoSwPosition(*m_entries[m_nCurrent]->GetPoint());
    // Refresh the buttons
    if (bBackWasDisabled)
        m_rMyShell.GetView().GetViewFrame().GetBindings().Invalidate(FN_NAVIGATION_BACK);
    if (!forwardEnabled())
        m_rMyShell.GetView().GetViewFrame().GetBindings().Invalidate(FN_NAVIGATION_FORWARD);
}

// This method adds the SwPosition rPos to the navigation history
// rPos is usually the current position of the cursor in the document

bool SwNavigationMgr::addEntry(const SwPosition& rPos) {

    // Flags that will be used for refreshing the buttons
    bool bBackWasDisabled = !backEnabled();
    bool bForwardWasEnabled = forwardEnabled();

    bool bRet = false; // return value of the function.
                       // Indicates whether the index should be decremented before
                       // jumping back or not
    // The navigation history has recency with temporal ordering enhancement,
    // as described on http://zing.ncsl.nist.gov/hfweb/proceedings/greenberg/
    // If any forward history exists, twist the tail of the
    // list from the current position to the end
    if (bForwardWasEnabled) {

        size_t number_ofm_entries = m_entries.size(); // To avoid calling m_entries.size() multiple times
        int curr = m_nCurrent; // Index from which we'll twist the tail.
        int n = (number_ofm_entries - curr) / 2; // Number of entries that will swap places
        for (int i = 0; i < n; i++) {
            std::swap(m_entries[curr + i], m_entries[number_ofm_entries -1 - i]);
        }

        if (*m_entries.back()->GetPoint() != rPos)
        {
            sw::UnoCursorPointer pCursor(m_rMyShell.GetDoc()->CreateUnoCursor(rPos));
            StartListening(pCursor->m_aNotifier);
            m_entries.push_back(pCursor);
        }
        bRet = true;
    }
    else {
        if ( (!m_entries.empty() && *m_entries.back()->GetPoint() != rPos) || m_entries.empty() ) {
            sw::UnoCursorPointer pCursor(m_rMyShell.GetDoc()->CreateUnoCursor(rPos));
            StartListening(pCursor->m_aNotifier);
            m_entries.push_back(pCursor);
            bRet = true;
        }
        if (m_entries.size() > 1 && *m_entries.back()->GetPoint() == rPos)
            bRet = true;
        if (m_entries.size() == 1 && *m_entries.back()->GetPoint() == rPos)
            bRet = false;
    }
    m_nCurrent = m_entries.size();

    // Refresh buttons
    if (bBackWasDisabled)
        m_rMyShell.GetView().GetViewFrame().GetBindings().Invalidate(FN_NAVIGATION_BACK);
    if (bForwardWasEnabled)
        m_rMyShell.GetView().GetViewFrame().GetBindings().Invalidate(FN_NAVIGATION_FORWARD);

    return bRet;
}

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