// Fill out your copyright notice in the Description page of Project Settings.


#include "AdventureMap.h"
#include "HexTile.h"
#include "AdventureCameraPawn.h"
#include "AdventureCharacter.h"
#include "Kismet/GameplayStatics.h"
#include "Algo/Reverse.h"

// Sets default values
AAdventureMap::AAdventureMap()
{
}

// Called when the game starts or when spawned
void AAdventureMap::BeginPlay()
{
	Super::BeginPlay();
	UWorld* World = GetWorld();
	if (IsValid(BaseTileClass)) 
	{ 
		MakeGrid();
	}
}

// Called once on Begin Play
void AAdventureMap::MakeGrid() 
{	
	UWorld* World = GetWorld();
	FVector NextHexAt = FVector();
	float HexWidth = sqrt(3) * TileSize;
	int QOffset = 0;

	for (int r = 1; r <= GridSize; r++) 
	{
		float XOffset = 0.f;

		if (r % 2 != 0)
		{
			if (r > 1)
			{
				QOffset--;
			}
		}
		else { XOffset = HexWidth / 2; }

		for (int q = 1; q <= GridSize; q++)
		{
			NextHexAt.X = XOffset + (HexWidth * q);
			NextHexAt.Y = TileSize * 1.5f * r;
			NextHexAt.Z = 0.f;

			FTransform SpawnTransform = FTransform(NextHexAt);
			AHexTile* Tile = World->SpawnActor<AHexTile>(BaseTileClass, SpawnTransform);

			Tile->Q = q - 1 + QOffset;
			Tile->R = r - 1;

			Grid.Add(Tile);
		}
	}

	for (auto& tile : Grid)
	{
		tile->Index = GridIndex(tile->Q, tile->R);
	}

	bHexGridReady = true;
}

// Every Hex Tile's index within the Grid Array can be derived from its Q and R coordinates
int32 AAdventureMap::GridIndex(int32 qAxial, int32 rAxial)
{
	/*
	*	The Q axis is (i.e. columns are) oriented diagonally.
	*	The Hex Grid has a rough square shape, hence the Q coordinates must be offset by -1 every other row.
	*/
	int32 column = qAxial + FMath::FloorToInt(rAxial / 2);
	return (rAxial * GridSize) + column;
}

AHexTile* AAdventureMap::RandomHex()
{
	int32 RandHex = GridIndex(FMath::RandRange(0, GridSize-1), FMath::RandRange(0, GridSize-1));
	return Grid[RandHex];
}

TArray<AHexTile*> AAdventureMap::Neighbors(AHexTile* OfHex)
{
	TArray<AHexTile*> Neighbors;
	int32 I;

	I = GridIndex(OfHex->Q + 1	, OfHex->R + 0	);
	if (Grid.IsValidIndex(I) && OfHex->Distance(Grid[I]) == 1) { Neighbors.Add(Grid[I]); }

	I = GridIndex(OfHex->Q + 1	, OfHex->R - 1	);
	if (Grid.IsValidIndex(I) && OfHex->Distance(Grid[I]) == 1) { Neighbors.Add(Grid[I]); }

	I = GridIndex(OfHex->Q + 0	, OfHex->R - 1	);
	if (Grid.IsValidIndex(I) && OfHex->Distance(Grid[I]) == 1) { Neighbors.Add(Grid[I]); }

	I = GridIndex(OfHex->Q - 1	, OfHex->R + 0	);
	if (Grid.IsValidIndex(I) && OfHex->Distance(Grid[I]) == 1) { Neighbors.Add(Grid[I]); }

	I = GridIndex(OfHex->Q - 1	, OfHex->R + 1	);
	if (Grid.IsValidIndex(I) && OfHex->Distance(Grid[I]) == 1) { Neighbors.Add(Grid[I]); }

	I = GridIndex(OfHex->Q + 0	, OfHex->R + 1	);
	if (Grid.IsValidIndex(I) && OfHex->Distance(Grid[I]) == 1) { Neighbors.Add(Grid[I]); }

	return Neighbors;
}

// Be aware that the respective character will become relevant to this function at some point
TArray<AHexTile*> AAdventureMap::FindPathAStar(AHexTile* Start, AHexTile* Goal)
{
	TArray<AHexTile*> Priorities;
	Priorities.Init(Start, 1);

	Goal->CameFrom = Start;

	// Editing Hex->CameFrom pointers, i.e. chaining Hexes
	while (Priorities.IsValidIndex(0))
	{	
		AHexTile* Current = Priorities[0];
		Priorities.RemoveAt(0);
		if (*Current == *Goal) { break; }

		// Expanding the Frontier
		for (AHexTile* Next : Neighbors(Current))
		{
			int32 NewCost = Current->CostSoFar + Next->MoveCost;
			if (!Priorities.Contains(Next) || NewCost < Next->CostSoFar)
			{
				Next->CostSoFar = NewCost;
				int32 NewPrio = NewCost + Next->Distance(Goal);

				// Adjust the Priority Queue
				if (Priorities.Contains(Next)) { Priorities.Remove(Next); }
				for (AHexTile* Hex : Priorities)
				{
					int32 OldPrio = Hex->CostSoFar + Hex->Distance(Goal);
					int32 Index;
					Priorities.Find(Hex, Index);

					if (OldPrio > NewPrio)
					{						
						Priorities.Insert(Next, Index);
						Next->CameFrom = Current;
						break;
					}
					if (Index == Priorities.Num() - 1 && OldPrio <= NewPrio)
					{
						Priorities.Emplace(Next);
						Next->CameFrom = Current;
					}
				}
			}
		}
	}

	TArray<AHexTile*> Path;
	AHexTile* Hex = Goal;
	while (*Hex != *Start)
	{
		Path.Emplace(Hex);
		Hex = Hex->CameFrom;
	}

	Algo::Reverse(Path);
	return Path; // currently always length of 1
}