/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

struct UndoManager::ActionSet
{
    ActionSet (const String& transactionName)  : name (transactionName)
    {}

    bool perform() const
    {
        for (auto* a : actions)
            if (! a->perform())
                return false;

        return true;
    }

    bool undo() const
    {
        for (int i = actions.size(); --i >= 0;)
            if (! actions.getUnchecked(i)->undo())
                return false;

        return true;
    }

    int getTotalSize() const
    {
        int total = 0;

        for (auto* a : actions)
            total += a->getSizeInUnits();

        return total;
    }

    OwnedArray<UndoableAction> actions;
    String name;
    Time time { Time::getCurrentTime() };
};

//==============================================================================
UndoManager::UndoManager (int maxNumberOfUnitsToKeep, int minimumTransactions)
{
    setMaxNumberOfStoredUnits (maxNumberOfUnitsToKeep, minimumTransactions);
}

UndoManager::~UndoManager()
{
}

//==============================================================================
void UndoManager::clearUndoHistory()
{
    transactions.clear();
    totalUnitsStored = 0;
    nextIndex = 0;
    sendChangeMessage();
}

int UndoManager::getNumberOfUnitsTakenUpByStoredCommands() const
{
    return totalUnitsStored;
}

void UndoManager::setMaxNumberOfStoredUnits (int maxUnits, int minTransactions)
{
    maxNumUnitsToKeep          = jmax (1, maxUnits);
    minimumTransactionsToKeep  = jmax (1, minTransactions);
}

//==============================================================================
bool UndoManager::perform (UndoableAction* newAction, const String& actionName)
{
    if (perform (newAction))
    {
        if (actionName.isNotEmpty())
            setCurrentTransactionName (actionName);

        return true;
    }

    return false;
}

bool UndoManager::perform (UndoableAction* newAction)
{
    if (newAction != nullptr)
    {
        std::unique_ptr<UndoableAction> action (newAction);

        if (isPerformingUndoRedo())
        {
            jassertfalse;  // Don't call perform() recursively from the UndoableAction::perform()
                           // or undo() methods, or else these actions will be discarded!
            return false;
        }

        if (action->perform())
        {
            auto* actionSet = getCurrentSet();

            if (actionSet != nullptr && ! newTransaction)
            {
                if (auto* lastAction = actionSet->actions.getLast())
                {
                    if (auto coalescedAction = lastAction->createCoalescedAction (action.get()))
                    {
                        action.reset (coalescedAction);
                        totalUnitsStored -= lastAction->getSizeInUnits();
                        actionSet->actions.removeLast();
                    }
                }
            }
            else
            {
                actionSet = new ActionSet (newTransactionName);
                transactions.insert (nextIndex, actionSet);
                ++nextIndex;
            }

            totalUnitsStored += action->getSizeInUnits();
            actionSet->actions.add (std::move (action));
            newTransaction = false;

            moveFutureTransactionsToStash();
            dropOldTransactionsIfTooLarge();
            sendChangeMessage();
            return true;
        }
    }

    return false;
}

void UndoManager::moveFutureTransactionsToStash()
{
    if (nextIndex < transactions.size())
    {
        stashedFutureTransactions.clear();

        while (nextIndex < transactions.size())
        {
            auto* removed = transactions.removeAndReturn (nextIndex);
            stashedFutureTransactions.add (removed);
            totalUnitsStored -= removed->getTotalSize();
        }
    }
}

void UndoManager::restoreStashedFutureTransactions()
{
    while (nextIndex < transactions.size())
    {
        totalUnitsStored -= transactions.getUnchecked (nextIndex)->getTotalSize();
        transactions.remove (nextIndex);
    }

    for (auto* stashed : stashedFutureTransactions)
    {
        transactions.add (stashed);
        totalUnitsStored += stashed->getTotalSize();
    }

    stashedFutureTransactions.clearQuick (false);
}

void UndoManager::dropOldTransactionsIfTooLarge()
{
    while (nextIndex > 0
            && totalUnitsStored > maxNumUnitsToKeep
            && transactions.size() > minimumTransactionsToKeep)
    {
        totalUnitsStored -= transactions.getFirst()->getTotalSize();
        transactions.remove (0);
        --nextIndex;

        // if this fails, then some actions may not be returning
        // consistent results from their getSizeInUnits() method
        jassert (totalUnitsStored >= 0);
    }
}

void UndoManager::beginNewTransaction()
{
    beginNewTransaction ({});
}

void UndoManager::beginNewTransaction (const String& actionName)
{
    newTransaction = true;
    newTransactionName = actionName;
}

void UndoManager::setCurrentTransactionName (const String& newName)
{
    if (newTransaction)
        newTransactionName = newName;
    else if (auto* action = getCurrentSet())
        action->name = newName;
}

String UndoManager::getCurrentTransactionName() const
{
    if (auto* action = getCurrentSet())
        return action->name;

    return newTransactionName;
}

//==============================================================================
UndoManager::ActionSet* UndoManager::getCurrentSet() const     { return transactions[nextIndex - 1]; }
UndoManager::ActionSet* UndoManager::getNextSet() const        { return transactions[nextIndex]; }

bool UndoManager::isPerformingUndoRedo() const  { return isInsideUndoRedoCall; }

bool UndoManager::canUndo() const      { return getCurrentSet() != nullptr; }
bool UndoManager::canRedo() const      { return getNextSet()    != nullptr; }

bool UndoManager::undo()
{
    if (auto* s = getCurrentSet())
    {
        const ScopedValueSetter<bool> setter (isInsideUndoRedoCall, true);

        if (s->undo())
            --nextIndex;
        else
            clearUndoHistory();

        beginNewTransaction();
        sendChangeMessage();
        return true;
    }

    return false;
}

bool UndoManager::redo()
{
    if (auto* s = getNextSet())
    {
        const ScopedValueSetter<bool> setter (isInsideUndoRedoCall, true);

        if (s->perform())
            ++nextIndex;
        else
            clearUndoHistory();

        beginNewTransaction();
        sendChangeMessage();
        return true;
    }

    return false;
}

String UndoManager::getUndoDescription() const
{
    if (auto* s = getCurrentSet())
        return s->name;

    return {};
}

String UndoManager::getRedoDescription() const
{
    if (auto* s = getNextSet())
        return s->name;

    return {};
}

StringArray UndoManager::getUndoDescriptions() const
{
    StringArray descriptions;

    for (int i = nextIndex;;)
    {
        if (auto* t = transactions[--i])
            descriptions.add (t->name);
        else
            return descriptions;
    }
}

StringArray UndoManager::getRedoDescriptions() const
{
    StringArray descriptions;

    for (int i = nextIndex;;)
    {
        if (auto* t = transactions[i++])
            descriptions.add (t->name);
        else
            return descriptions;
    }
}

Time UndoManager::getTimeOfUndoTransaction() const
{
    if (auto* s = getCurrentSet())
        return s->time;

    return {};
}

Time UndoManager::getTimeOfRedoTransaction() const
{
    if (auto* s = getNextSet())
        return s->time;

    return Time::getCurrentTime();
}

bool UndoManager::undoCurrentTransactionOnly()
{
    if ((! newTransaction) && undo())
    {
        restoreStashedFutureTransactions();
        return true;
    }

    return false;
}

void UndoManager::getActionsInCurrentTransaction (Array<const UndoableAction*>& actionsFound) const
{
    if (! newTransaction)
        if (auto* s = getCurrentSet())
            for (auto* a : s->actions)
                actionsFound.add (a);
}

int UndoManager::getNumActionsInCurrentTransaction() const
{
    if (! newTransaction)
        if (auto* s = getCurrentSet())
            return s->actions.size();

    return 0;
}

} // namespace juce