#include "WordDrillModel.h"
#include "../dictionary/Card.h"
#include "../dictionary/CardPack.h"
#include "StudySettings.h"

#include <stdlib.h>
#include <time.h>

WordDrillModel::WordDrillModel( CardPack* aCardPack ):
    IStudyModel( aCardPack ), m_historyCurPackStart(0)
    {
    curCardNum = NoCardIndex;
    srand( time(NULL) );
    connect( aCardPack, SIGNAL(cardsGenerated()), SLOT(updateStudyState()) );

    generateFreshPack();
    pickNextCard();
    }

/** Get current card.
  * If the current card doesn't exist any more, find the next valid card.
  */

Card* WordDrillModel::getCurCard() const
    {
    if( m_cardHistory.isEmpty() || curCardNum < 0 )   // No cards in the pack
        return NULL;
    if( curCardNum >= m_cardHistory.size() )
        return NULL;
    QString cardName = m_cardHistory.at(curCardNum);
    return cardPack->getCard( cardName );
    }

void WordDrillModel::updateStudyState()
    {
    generateFreshPack();
    cleanHistoryFromRemovedCards();
    if( getCurCard() )
        emit curCardUpdated();
    else
        pickNextCard();
    }

void WordDrillModel::generateFreshPack()
    {
    m_freshPack = cardPack->getCardQuestions();
    // Remove already reviewed cards
    if( m_historyCurPackStart >= m_cardHistory.size() )
        return;
    foreach( QString reviewedCard, m_cardHistory.mid( m_historyCurPackStart ) )
        m_freshPack.removeAll( reviewedCard );
    }

void WordDrillModel::cleanHistoryFromRemovedCards()
    {
    if( m_cardHistory.isEmpty() )
        return;
    bool cardsRemoved = false;
    QMutableStringListIterator it( m_cardHistory );
    int i = 0;
    while( it.hasNext() )
        {
        QString cardName = it.next();
        if( !cardPack->containsQuestion( cardName ) )
            {
            it.remove();
            cardsRemoved = true;
            if( i < curCardNum )
                curCardNum--;
            }
        i++;
        }
    if( cardsRemoved )
        {
        if( curCardNum >= m_cardHistory.size() )
            curCardNum = m_cardHistory.size() - 1;
        emit nextCardSelected();
        }
    }


/** Picks a random card. Removes the selected card from the fresh pack and adds it to the history.
 * Thus, the new card is the last entry in the history.
 * This function guarantees that the new card's question will be different from the previous one, unless there is no choice.
 *
 * Updates #m_curCardNum.
 */
void WordDrillModel::pickNextCard()
    {
    QString selectedCardName;
    const Card* selectedCard = NULL;
    do
        {
        if( m_freshPack.isEmpty() )  // No fresh cards
            {
            m_historyCurPackStart = m_cardHistory.size(); // Refers beyond the history pack
            generateFreshPack();
            if( m_freshPack.isEmpty() )  // Still no any cards available - no useful cards in the dictionary or it's empty
                {
                curCardNum = NoCardIndex;
                emit nextCardSelected();
                return;
                }
            }
        if( m_freshPack.size() == 1 )    // Only 1 fresh card, no choice
            selectedCardName = m_freshPack.takeFirst();
        else
            {
            int selectedCardNum;
            if( StudySettings::inst()->showRandomly )
                selectedCardNum = rand() % m_freshPack.size();
            else
                selectedCardNum = 0;
            if( !m_cardHistory.isEmpty() )
                while( m_freshPack[ selectedCardNum ] == m_cardHistory.last() ) // The new question must be different from the current one
                    {
                    selectedCardNum++;
                    selectedCardNum %= m_freshPack.size();
                    }
            selectedCardName = m_freshPack.takeAt( selectedCardNum );
            }
        selectedCard = cardPack->getCard( selectedCardName );
        }
    while( !selectedCard );
    m_cardHistory << selectedCardName;
    curCardNum = m_cardHistory.size() - 1;
    emit nextCardSelected();
    }

/** Go back along the history line.
 * @return true, if the transition was successful
 */
bool WordDrillModel::goBack()
    {
    if( !canGoBack() )
        return false;
    curCardNum--;
    emit nextCardSelected();
    return true;
    }

/** Go forward along the history line.
 * @return true, if the transition was successful
 */
bool WordDrillModel::goForward()
    {
    if( !canGoForward() )
        return false;
    curCardNum++;
    emit nextCardSelected();
    return true;
    }

bool WordDrillModel::canGoBack()
    {
    return curCardNum > 0;
    }

bool WordDrillModel::canGoForward()
    {
    return curCardNum < m_cardHistory.size() - 1;
    }