#ifndef COMMON_CONTAINERS_GRID_H
#define COMMON_CONTAINERS_GRID_H

#include "Common/Basics.h"

#include <utility> //For std::move()
#include <stdexcept> //For std::out_of_range exception.

class cPoint;
class cRect;

namespace Common {

template<class Type> class GridIterator;

/*
    A resizable 2D array container, that resizes without harming the relative location of the elements held
    by the container, and supports negative indices, like a 2D Cartesian grid.
*/
template<typename Type>
class Grid
{
public:
    typedef GridIterator<Type> iterator;
    
public:
    Grid() : memory(nullptr), boundsOffset(0)
    {   }
    
    //Construct and call Resize().
    Grid(const cRect &newBounds, const Type &value = Type()) : memory(nullptr)
    {
        this->Resize(newBounds, value);
    }
    
    ~Grid()
    {
        //Clear the grid, calling the destructors on any constructed elements.
        this->Clear();
        
        //Deallocate any reserved memory.
        this->deallocate(this->memory);
    }
    
    //================================================================
    
    //Erases the grid, resetting the bounds to (0,0,0,0).
    //Does not free the reserved capacity. Call Conserve() afterward to do that.
    void Clear()
    {
        this->Resize(cRect(0,0,0,0));
    }
    
    //Resets the grid to (0,0,0,0) and releases the reserved memory as well.
    //This is the same as calling Clear() followed by Conserve().
    void Reset()
    {
        this->Clear();
        this->Conserve();
    }
    
    //================================================================
    
    //Returns true if the width *or* the height (or both) of the grid is 0, *even* if its position is *not* at (0,0).
    bool IsEmpty() const
    {
        return this->bounds.IsEmpty();
    }
    
    //True if the grid is 0 by 0 *and* its position is at (0,0). 
    bool IsNull() const
    {
        return this->bounds.IsNull();
    }
    
    //================================================================
    
    //Resizes the grid to 'newBounds', constructing the new elements with 'value' (or the default constructor if 'value' is not set).
    //If Grid doesn't have enough capacity, it'll reallocate storage and move the elements to new memory addresses.
    //Throws std::bad_alloc if the allocation failed, and throws any exceptions thrown by element constructors.
    void Resize(const cRect &newBounds, const Type &value = Type())
    {
        this->ensureCapacity(newBounds, true);
        this->constructAdditions(this->bounds, newBounds, value);
        
        this->bounds = newBounds;
        this->boundsOffset = this->capacity.Index(this->bounds.position);
    }

    const cRect &GetBounds() const
    {
        return this->bounds;
    }
    
    //================================================================
    
    //Reserves 'newCapacity' amount of memory, without actually resizing the grid. This will reallocate the memory and move the elements to new addresses.
    //Reserve() will not allow the grid to shrink smaller than the capacity currently is reserved to.
    //Throws std::bad_alloc if the allocation failed, and throws any exceptions thrown by element constructors.
    void Reserve(const cRect &newCapacity)
    {
        this->ensureCapacity(newCapacity, false);
    }
    
    //Releases all capacity that is no longer needed. This will reallocate the memory and move the elements to new addresses.
    void Conserve()
    {
        this->reallocateMemory(this->bounds);
    }
    
    //Returns the amount of memory held in reserve for future resizing.
    const cRect &GetCapacity() const
    {
        return this->capacity;
    }
    
    //================================================================
    
    //Resizes the grid. Negative values shrink the grid.
    void Expand(int amount)
    {
        this->Expand(amount, amount, amount, amount);
    }
    
    void Expand(int horizontal, int vertical)
    {
        this->Expand(horizontal, horizontal, vertical, vertical);
    }
    
    void Expand(int left, int right, int top, int bottom)
    {
        cRect newBounds = this->bounds;
        newBounds.Pad(left, right, top, bottom);
        
        this->Resize(newBounds);
    }
    
    //Resizes the grid. Negative values enlarge the grid.
    void Shrink(int amount)
    {
        this->Shrink(amount, amount, amount, amount);
    }
    
    void Shrink(int horizontal, int vertical)
    {
        this->Shrink(horizontal, horizontal, vertical, vertical);
    }
    
    void Shrink(int left, int right, int top, int bottom)
    {
        cRect newBounds = this->bounds;
        newBounds.Pad(-left, -right, -top, -bottom);
        
        this->Resize(newBounds);
    }
    
    //================================================================
    
    //Throws std::out_of_range if out of range.
    Type &At(const cPoint &pos)
    {
        if(!this->bounds.Contains(pos))
        {
            std::string message = std::string("Grid::At() - 'pos' is not within range.\n")
                                + "\t'pos' = " + pos.ToString()
                                + "\n\t'bounds' = " + this->bounds.ToString();
            
            throw std::out_of_range(message);
        }
        
        return (*this)[pos];
    }

    //Doesn't check for range.
    Type &operator[](const cPoint &pos)
    {
        //Convert the point to a index into the memory.
        size_t index = this->capacity.Index(pos);
        
        return this->memory[index];
    }

    //Doesn't check for range. Index-based lookup for iteration (from index '0' to "this->bounds: (width * height)").
    Type &AtIndex(unsigned index)
    {
        cPoint pos = this->bounds.FromIndex(index);
        int newIndex = this->capacity.Index(std::move(pos));
        
        return this->memory[newIndex];
    }
    
    //================================================================
    
    iterator begin()
    { return iterator(*this, 0); }
    
    iterator end()
    { return iterator(*this, this->bounds.Area()); }
    
    //================================================================
    
private:
    //Constructs all the new elements between oldBounds and newBounds setting them to 'value'.
    //If 'newBounds' is smaller than 'oldBounds', deconstructs the old elements.
    void constructAdditions(const cRect &oldBounds, const cRect &newBounds, const Type &value = Type())
    {
        //The largest extent of both rects.
        cRect totalArea = cRect::Encompassing(oldBounds, newBounds);
        //The overlapping portion of both rects (if any).
        cRect reducedArea = cRect::Intersection(oldBounds, newBounds);
        
        size_t constructed = 0, destructed = 0, preserved = 0, ignored = 0;
        
        for(cPoint point : totalArea)
        {
            if(reducedArea.Contains(point))
            {
                //Do nothing - this area is already constructed.
                preserved++;
            }
            else if(newBounds.Contains(point))
            {
                //Needs to be constructed.
                this->construct((*this)[point], value);
                
                constructed++;
            }
            else if(oldBounds.Contains(point))
            {
                //Needs to be destructed.
                this->destruct((*this)[point]);
                
                destructed++;
            }
            else
            {
                //Do nothing - this area is already destructed.
                
                ignored++;
            }
        }
    }
    
    //================================================================
    
    //Construct a single element.
    void construct(Type &element, const Type &value = Type())
    {
        new (&element) Type(value); //Call constructor.
    } 
    
    //Constructs an element with move semantics.
    void moveConstruct(Type &element, Type &&value)
    {
        new (&element) Type(value); //Call move constructor.
    }

    //Destruct a single element.
    void destruct(Type &element)
    {
        element.~Type(); //Call destructor.
    }
    
    //================================================================
    
    //Ensures *at least* enough room for 'bounds'.
    //If 'addExtra' is true, includes even more capacity for future growth.
    void ensureCapacity(const cRect &bounds, bool addExtra)
    {
        //Check whether we have enough capacity to resize.
        if(!this->capacity.Contains(bounds))
        {
            cRect desiredCapacity = bounds;
            
            if(addExtra)
            {
                //If we're bothering to grow in size, we might as well reserve a little extra for future growth.
                int quarterWidth = (bounds.size.width / 4) + 1;
                int quarterHeight = (bounds.size.height / 4) + 1;
                
                desiredCapacity.Pad(quarterWidth, quarterWidth, quarterHeight, quarterHeight);
            }
            
            //Allocate and move the elements.
            this->reallocateMemory(desiredCapacity);
        }
    }    
    
    //================================================================
    
    //This allocates enough memory for 'capacity', without constructing any elements.
    Type *allocate(const cRect &capacity)
    {
        //Allocate the new memory.
        size_t numElements = capacity.size.Area();
        size_t numBytes = (sizeof(Type) * numElements);
        void *data = ::operator new(numBytes);
        
        return static_cast<Type*>(data);
    }
    
    //This deallocates 'memory', without calling any destructors.
    void deallocate(Type *data)
    {
        ::operator delete(data);
    }
    
    //================================================================
    
    //Reallocates the memory and migrates the elements over using moveElements().
    //Throws std::bad_alloc if the allocation failed, and throws any exceptions thrown by element constructors.
    void reallocateMemory(const cRect &newCapacity)
    {
        if(!this->memory)
        {
            //If we don't have any memory, just allocate some and don't worry about moving any elements.
           this->memory = this->allocate(newCapacity);
        }
        else if(newCapacity.IsEmpty())
        {
            //Free all the memory.
            this->deallocate(this->memory);
            
            this->memory = nullptr;
        }
        else
        {
            //Allocate the new memory.
            Type *newMemory = this->allocate(newCapacity);
            
            //A few extra variables for readability.
            Type *oldMemory = this->memory;
            const cRect &oldCapacity = this->capacity;
            
            //Move the elements.
            this->moveElements(oldMemory, oldCapacity, newMemory, newCapacity, this->bounds);
            
            //Delete the old memory.
            this->deallocate(oldMemory);
            oldMemory = nullptr;
            
            //And store the new pointer.
            this->memory = newMemory;
        }
        
        //Record the new capacity.
        this->capacity = newCapacity;
    }
    
    //Called by 'reallocateMemory' only.
    void moveElements(Type *oldMemory, const cRect &oldCapacity, Type *newMemory,
                      const cRect &newCapacity, const cRect &bounds)
    {
        //Insanity preservation.
        //Assert that our elements are actually within the capacity of both the new and old blocks of memory.
        BOOST_ASSERT(oldCapacity.Contains(bounds));
        BOOST_ASSERT(newCapacity.Contains(bounds));
        
        //Assert that neither block of memory's size is empty (they have to have a positive non-zero width and height).
        BOOST_ASSERT(!oldCapacity.IsEmpty());
        BOOST_ASSERT(!newCapacity.IsEmpty());
        
        //Assert that neither pointer to the allocated memory is empty.
        BOOST_ASSERT(oldMemory != nullptr);
        BOOST_ASSERT(newMemory != nullptr);
        
        //The length of each 'row' of the grid's capacity in memory.
        size_t oldStride = oldCapacity.size.width;
        size_t newStride = newCapacity.size.width;
        
        //The initial offset of the actual bounds from the memory capacity.
        size_t oldOffset = oldCapacity.Index(bounds.position);
        size_t newOffset = newCapacity.Index(bounds.position);
        
        //The number of rows and columns of actual elements we need to move.
        size_t rows = bounds.size.height;
        size_t columns = bounds.size.width;
        
        for(size_t row = 0; row < rows; row++)
        {
            for(size_t column = 0; column < columns; column++)
            {
                size_t oldIndex = (row * oldStride) + column;
                oldIndex += oldOffset;
                
                size_t newIndex = (row * newStride) + column;
                newIndex += newOffset;
                
                //Construct the new location, and move the element.
                this->moveConstruct(newMemory[newIndex], std::move(oldMemory[oldIndex]));
                
                //Destruct old location.
                this->destruct(oldMemory[oldIndex]);
            }
        }
    }

    //================================================================
    
private:
    Type *memory;
    unsigned int boundsOffset; //The offset of 'bounds' within 'capacity'. Only used for AtIndex, for faster iteration.
    
    cRect bounds; //Current grid boundries.
    cRect capacity; //Currently allocated memory capacity, garunteed to be at least 'bounds' and maybe larger.
};

///////////////////////////////////////////////////////////////////////////////////////////////////////////////
//XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX//
///////////////////////////////////////////////////////////////////////////////////////////////////////////////

//A random-access iterator for iterating over each element of a Common::Grid.
template <typename Type>
class GridIterator
{
public: 
    GridIterator(Common::Grid<Type> &grid, unsigned index) : grid(grid), index(index)
    {
        this->maxIndex = this->grid.GetBounds().Area();
    }
    
    //================================================================
    
    //De-reference.
    Type &operator*()
    {
        return this->grid.AtIndex(this->index);
    }
    
    Type &operator->()
    {
        return (operator*());
    }
    
    //================================================================
    
    //Comparison.
    bool operator==(const GridIterator &other) const
    {
        return (&this->grid == &other.grid) && (this->index == other.index);
    }
    
    bool operator!=(const GridIterator &other) const
    {
        return !operator==(other);
    }
    
    //================================================================
    
    //Increment/decrement.
    GridIterator &operator++()
    {
        this->index++;
        Limit(this->index, this->maxIndex);
        return *this;
    }
    
    GridIterator operator++(int)
    {
        GridIterator temp(*this);
        ++(*this);
        return temp;
    }
    
    GridIterator &operator--()
    {
        this->index--;
        return *this;
    }
    
    GridIterator operator--(int)
    {
        GridIterator temp(*this);
        --(*this);
        return temp;
    }
    
    //================================================================

    //Random access.
    GridIterator operator+(int n)
    {
        GridIterator temp(*this);
        temp.index += n;
        return temp;
    }
    
    GridIterator &operator+=(int n)
    {
        this->index += n;
        Limit(this->index, this->maxIndex);
        return *this;
    }
    
    GridIterator operator-(int n)
    {
        GridIterator temp(*this);
        temp.index -= n;
        return temp;
    }
    
    GridIterator &operator-=(int n)
    {
        this->index -= n;
        return *this;
    }
    
    //================================================================
    
private:
    Common::Grid<Type> &grid;
    unsigned index; //The current index.
    unsigned maxIndex; //The maximum value (and the result returned by 'std::end()'.
};

//================================================================

} //End of namespace.

#endif // COMMON_CONTAINERS_GRID_H