#include "core.h"
#include "handmade.h"
#include "handmade_math.h"
#include "sdl_handmade.h"

#include "handmade_intrinsics.h"
#include "handmade_random.h"
#include "handmade_tile.h"
#include "handmade_tile.c"

#include <stdio.h>
#include <string.h> /* memset */

static void GameOutputSound(struct game_state *GameState,
                            struct game_sound_output_buffer *SoundBuffer,
                            int ToneHz)
{
    /*
    short ToneVolume, *SampleOut;
    int WavePeriod, SampleIndex;

    ToneVolume = 0;
    WavePeriod = SoundBuffer->SamplesPerSecond / ToneHz;

    SampleOut = SoundBuffer->Samples;

    for(SampleIndex = 0;
        SampleIndex < SoundBuffer->SampleCount;
        SampleIndex++)
    {
        float SineValue;
        short SampleValue;

        SineValue = sinf(GameState->tSine);
        SampleValue = (short)(SineValue * ToneVolume);
        *SampleOut++ = SampleValue;
        *SampleOut++ = SampleValue;

        GameState->tSine += 2.0f * (float)PI * 1.0f / (float)WavePeriod;
        if(GameState->tSine > 2.0f*(float)PI) {
            GameState->tSine -= 2.0f*(float)PI;
        }
    }
    */
}

static void ClearBackground(struct game_offscreen_buffer *Buffer)
{
    int Width = Buffer->Width;
    int Height = Buffer->Height;

    for(int X = 0; X < Width * Height; X++) {
        unsigned int *Pixel = &((unsigned int *)Buffer->Memory)[X];
        *Pixel = 0xFFFFFF;
    }
}

static void DrawRectangle(struct game_offscreen_buffer *Buffer,
                          struct v2 vMin, struct v2 vMax,
                          float R, float G, float B)
{
    int MinX = RoundFloatToInt(vMin.X);
    int MinY = RoundFloatToInt(vMin.Y);
    int MaxX = RoundFloatToInt(vMax.X);
    int MaxY = RoundFloatToInt(vMax.Y);

    int Width = Buffer->Width;
    int Height = Buffer->Height;

    if(MinX < 0)
        MinX = 0;
    if(MinY < 0)
        MinY = 0;

    if(MaxX > Width)
        MaxX = Width;
    if(MaxY > Height)
        MaxY = Height;

    /*unsigned int Color = (unsigned int)((RoundFloatToInt(R * 255.0f) << 16) |
                                        (RoundFloatToInt(G * 255.0f) <<  8) |
                                        (RoundFloatToInt(B * 255.0f) <<  0));*/
    unsigned int Color = (unsigned int)((RoundFloatToInt(255.0f) << 24)     |
                                        (RoundFloatToInt(R * 255.0f) << 16) |
                                        (RoundFloatToInt(G * 255.0f) <<  8) |
                                        (RoundFloatToInt(B * 255.0f) <<  0));

    unsigned char *Row = ((unsigned char *)Buffer->Memory +
        MinX*Buffer->BytesPerPixel + MinY*Buffer->Pitch);
    for(int Y = MinY; Y < MaxY; Y++) {
        unsigned int *Pixel = (unsigned int *)Row;
        for(int X = MinX; X < MaxX; X++) {
            *(unsigned int *)Pixel = Color;
            Pixel++;
        }
        Row += Buffer->Pitch;
    }
}

static void DrawBitmap(struct game_offscreen_buffer *Buffer,
                       struct loaded_bitmap *Bitmap,
                       float RelX, float RelY, int AlignX, int AlignY)
{
    RelX -= (float)AlignX;
    RelY -= (float)AlignY;

    int MinX = RoundFloatToInt(RelX);
    int MinY = RoundFloatToInt(RelY);
    int MaxX = RoundFloatToInt(RelX + (float)Bitmap->Width);
    int MaxY = RoundFloatToInt(RelY + (float)Bitmap->Height);

    int Width = Buffer->Width;
    int Height = Buffer->Height;

    int SourceOffsetX = 0;
    if(MinX < 0) {
        SourceOffsetX = -MinX;
        MinX = 0;
    }

    int SourceOffsetY = 0;
    if(MinY < 0) {
        SourceOffsetY = -MinY;
        MinY = 0;
    }

    if(MaxX > Width)
        MaxX = Width;
    if(MaxY > Height)
        MaxY = Height;

    unsigned int *SourceRow =
        Bitmap->Pixels + Bitmap->Width*(Bitmap->Height - 1);
    SourceRow += -Bitmap->Width*SourceOffsetY + SourceOffsetX;
    unsigned char *DestRow = ((unsigned char *)Buffer->Memory +
        MinX*Buffer->BytesPerPixel + MinY*Buffer->Pitch);
    for(int Y = MinY; Y < MaxY; Y++) {
        unsigned int *Dest = (unsigned int *)DestRow;
        unsigned int *Source = SourceRow;
        for(int X = MinX; X < MaxX; X++) {
            float SA = (float)((*Source >> 24) & 0xFF);
            float SR = (float)((*Source >> 16) & 0xFF);
            float SG = (float)((*Source >>  8) & 0xFF);
            float SB = (float)((*Source >>  0) & 0xFF);

            float DR = (float)((*Dest >> 16) & 0xFF);
            float DG = (float)((*Dest >>  8) & 0xFF);
            float DB = (float)((*Dest >>  0) & 0xFF);

            float A  = SA / 255.0f;

            // TODO: This should be replaced by premultiplied alpha.
            float R = (1.0f-A)*DR + A*SR;
            float G = (1.0f-A)*DG + A*SG;
            float B = (1.0f-A)*DB + A*SB;

            *Dest = (((unsigned int)RoundFloatToInt(SA) << 24) |
                      ((unsigned int)RoundFloatToInt(R) << 16) |
                      ((unsigned int)RoundFloatToInt(G) << 8)  |
                      ((unsigned int)RoundFloatToInt(B) << 0));

            Dest++;
            Source++;
        }
        DestRow += Buffer->Pitch;
        SourceRow -= Bitmap->Width;
    }
}

#pragma pack(push, 1)
struct bitmap_header {
    unsigned short FileType;
    unsigned int FileSize;
    unsigned short Reserved1;
    unsigned short Reserved2;
    unsigned int BitmapOffset;
    unsigned int Size;
    int Width;
    int Height;
    unsigned short Planes;
    unsigned short BitsPerPixel;
    unsigned int Compression;
    unsigned int SizeOfBitmap;
    int HorzResolution;
    int VertResolution;
    unsigned int ColorsUsed;
    unsigned int ColorsImportant;

    unsigned int RedMask;
    unsigned int GreenMask;
    unsigned int BlueMask;
};
#pragma pack(pop)

static struct loaded_bitmap DEBUGLoadBMP(struct thread_context *Thread,
    struct debug_read_file_result
        (*DEBUGPlatformReadEntireFile)(struct thread_context *Thread,
                                       const char *), char *FileName)
{
    struct loaded_bitmap Result;
    memset(&Result, 0, sizeof(Result));

    struct debug_read_file_result ReadResult =
        DEBUGPlatformReadEntireFile(Thread, FileName);
    if(ReadResult.ContentsSize > 0) {
        struct bitmap_header *Header =
            (struct bitmap_header *)ReadResult.Contents;

        unsigned int *Pixels =
            (unsigned int *)((unsigned char *)ReadResult.Contents +
                Header->BitmapOffset);
        Result.Pixels = Pixels;
        Result.Width  = Header->Width;
        Result.Height = Header->Height;

        ASSERT(Header->Compression == 3);

        // NOTE: The byte order in memory is determined by the Header.

        unsigned int RedMask   = Header->RedMask;
        unsigned int GreenMask = Header->GreenMask;
        unsigned int BlueMask  = Header->BlueMask;
        unsigned int AlphaMask = ~(RedMask | GreenMask | BlueMask);

        struct bit_scan_result RedShift   =
            FindLeastSignificantSetBit(RedMask);
        struct bit_scan_result GreenShift =
            FindLeastSignificantSetBit(GreenMask);
        struct bit_scan_result BlueShift  =
            FindLeastSignificantSetBit(BlueMask);
        struct bit_scan_result AlphaShift =
            FindLeastSignificantSetBit(AlphaMask);

        ASSERT(RedShift.Found);
        ASSERT(GreenShift.Found);
        ASSERT(BlueShift.Found);
        ASSERT(AlphaShift.Found);

        unsigned int *SourceDest = Pixels;
        for(int Y = 0; Y < Header->Height; Y++) {
            for(int X = 0; X < Header->Width; X++) {
                unsigned int C = *SourceDest;

                *SourceDest = ((((C >> AlphaShift.Index) & 0xFF) << 24) |
                               (((C >> RedShift.Index  ) & 0xFF) << 16) |
                               (((C >> GreenShift.Index) & 0xFF) <<  8) |
                               (((C >> BlueShift.Index ) & 0xFF) <<  0));
                SourceDest++;
            }
        }
    }

    return Result;
}

static struct entity *GetEntity(struct game_state *GameState,
                                unsigned int Index)
{
    struct entity *Entity = NULL;

    if((Index > 0) && (Index < ARRAY_SIZE(GameState->Entities))) {
        Entity = &GameState->Entities[Index];
    }

    return Entity;
}

static void InitializePlayer(struct entity *Entity)
{
    Entity->Exists = 1;
    Entity->P.AbsTileX = 2;
    Entity->P.AbsTileY = 3;
    Entity->P.Offset.X = 5.0f;
    Entity->P.Offset.Y = 5.0f;
    Entity->Height = 1.4f;
    Entity->Width = 0.75f * Entity->Height;
}

static unsigned int AddEntity(struct game_state *GameState)
{
    unsigned int EntityIndex = ++GameState->EntityCount;

    ASSERT(GameState->EntityCount < ARRAY_SIZE(GameState->Entities));
    struct entity *Entity = &GameState->Entities[EntityIndex];
    memset(Entity, 0, sizeof(struct entity));

    return EntityIndex;
}

static void MovePlayer(struct game_state *GameState,
                       struct entity *Entity, float dt, struct v2 ddPlayer)
{
    struct tile_map *TileMap = GameState->World->TileMap;

    if((ddPlayer.X != 0.0f) && (ddPlayer.Y != 0.0f))
        ddPlayer = V2Multiply(0.7071067811865475244f, ddPlayer);

    float PlayerSpeed = 10.0f;
    ddPlayer = V2Multiply(PlayerSpeed, ddPlayer);

    ddPlayer = V2Add(ddPlayer, V2Unary(V2Multiply(1.5f, Entity->dP)));

    struct tile_map_position OldPlayerP = Entity->P;
    struct tile_map_position NewPlayerP = OldPlayerP;
    struct v2 PlayerDelta = V2Add(V2Multiply(0.5f, V2Multiply(Square(dt),
                                                              ddPlayer)),
                                             V2Multiply(dt, Entity->dP));
    NewPlayerP.Offset = V2Add(PlayerDelta, NewPlayerP.Offset);
    Entity->dP = V2Add(V2Multiply(dt, ddPlayer), Entity->dP);
    NewPlayerP = RecannonicalizePosition(TileMap, NewPlayerP);

#if 1
    struct tile_map_position PlayerLeft;
    PlayerLeft = NewPlayerP;
    PlayerLeft.Offset.X -= 0.5f*Entity->Width;
    PlayerLeft = RecannonicalizePosition(TileMap, PlayerLeft);

    struct tile_map_position PlayerRight;
    PlayerRight = NewPlayerP;
    PlayerRight.Offset.X += 0.5f*Entity->Width;
    PlayerRight = RecannonicalizePosition(TileMap, PlayerRight);

    int Collided = 0;
    struct tile_map_position ColP;
    memset(&ColP, 0, sizeof(ColP));
    if(!IsTileMapPointEmpty(TileMap, NewPlayerP)) {
        ColP = NewPlayerP;
        Collided = 1;
    }
    if(!IsTileMapPointEmpty(TileMap, PlayerLeft)) {
        ColP = PlayerLeft;
        Collided = 1;
    }
    if(!IsTileMapPointEmpty(TileMap, PlayerRight)) {
        ColP = PlayerRight;
        Collided = 1;
    }

    if(Collided) {
        struct v2 r = { 0, 0 };
        if(ColP.AbsTileX < Entity->P.AbsTileX) {
            r = (struct v2){ 1, 0 };
        }
        if(ColP.AbsTileX > Entity->P.AbsTileX) {
            r = (struct v2){ -1, 0 };
        }
        if(ColP.AbsTileY < Entity->P.AbsTileY) {
            r = (struct v2){ 0, 1 };
        }
        if(ColP.AbsTileY > Entity->P.AbsTileY) {
            r = (struct v2){ 0, -1 };
        }

        Entity->dP = V2Subtract(Entity->dP,
                                V2Multiply(1*InnerProduct(Entity->dP, r), r));
    } else {
        Entity->P = NewPlayerP;
    }
#else
    unsigned int MinTileX = 0;
    unsigned int MinTileY = 0;
    unsigned int OnePastMaxTileX = 0;
    unsigned int OnePastMaxTileY = 0;
    unsigned int AbsTileZ = GameState->PlayerP.AbsTileZ;
    tile_map_position BestPlayerP = GameState->PlayerP;
    F32 BestDistance = LengthSq(PlayerDelta);
    for(unsigned int AbsTileY = MinTileY;
        AbsTileY != OnePastMaxTileY;
        AbsTileY++)
    {
        for(unsigned int AbsTileX = MinTileX;
            AbsTileX != OnePastMaxTileX;
            AbsTileX++)
        {
            tile_map_position TestTileP =
                CenteredTilePoint(AbsTileX, AbsTileY, AbsTileZ);
            unsigned int TileValue = GetTileValueByPos(TileMap, TestTileP);
            if(IsTileValueEmpty(TileValue)) {
                v2 MinCorner = V2Multiply(-0.5f,
                                          (v2){ TileMap->TileSideInMeters,
                                                TileMap->TileSideInMeters });
                v2 MaxCorner = V2Multiply(-0.5f,
                                          (v2){ TileMap->TileSideInMeters,
                                                TileMap->TileSideInMeters });

                tile_map_difference RelNewPlayerP =
                    SubtractInF32(TileMap, &TestTileP, &NewPlayerP);
                v2 TestP = ClosestPointInRectangle(MinCorner, MaxCorner,
                                                   RelNewPlayerP);
                if(...) {
                }
            }
        }
    }
#endif

    if(!AreOnSameTile(&OldPlayerP, &Entity->P)) {
        unsigned int NewTileValue = GetTileValueByPos(TileMap, Entity->P);

        if(NewTileValue == 3) {
            Entity->P.AbsTileZ++;
        } else if(NewTileValue == 4) {
            Entity->P.AbsTileZ--;
        }
    }

    if(AbsoluteValue(ddPlayer.X) > AbsoluteValue(ddPlayer.Y)) {
        if(ddPlayer.X > 0) {
            Entity->FacingDirection = 0;
        } else {
            Entity->FacingDirection = 2;
        }
    } else if(AbsoluteValue(ddPlayer.X) < AbsoluteValue(ddPlayer.Y)) {
        if(ddPlayer.Y > 0) {
            Entity->FacingDirection = 1;
        } else {
            Entity->FacingDirection = 3;
        }
    }
}

void UpdateAndRender(struct thread_context *Thread,
                     struct game_memory *Memory, struct game_input *Input,
                     struct game_offscreen_buffer *Buffer,
                     struct game_sound_output_buffer *SoundBuffer)
{
    ASSERT((&Input->Controllers[0].Terminator -
        &Input->Controllers[0].Buttons[0]) ==
            ARRAY_SIZE(Input->Controllers[0].Buttons));
    ASSERT(sizeof(struct game_state) <= Memory->PermanentStorageSize);

    struct game_state *GameState;

    GameState = (struct game_state *)Memory->PermanentStorage;
    if(!Memory->IsInitialized) {
        // NOTE: Reserve entity slot 0 for null entity
        AddEntity(GameState);

        GameState->rect_pos.X = 0.0f;
        GameState->rect_pos.Y = 0.0f;

        GameState->ProgramIcon.Width = 256;
        GameState->ProgramIcon.Height = 256;
        GameState->ProgramIcon.BytesPerPixel = 4;
        GameState->ProgramIcon.Pitch = GameState->ProgramIcon.BytesPerPixel *
            GameState->ProgramIcon.Width;
        GameState->ProgramIcon.Memory =
            malloc(GameState->ProgramIcon.BytesPerPixel *
                GameState->ProgramIcon.Width *
                    GameState->ProgramIcon.Height);
        memset(GameState->ProgramIcon.Memory, 0,
            GameState->ProgramIcon.BytesPerPixel *
                GameState->ProgramIcon.Width *
                    GameState->ProgramIcon.Height);

#if 0
        GameState->ProgramIconBMP = DEBUGLoadBMP(Thread,
            Memory->DEBUGPlatformReadEntireFile, "data/program_icon.bmp");
        DrawBitmap(&GameState->ProgramIcon, &GameState->ProgramIconBMP,
                   0.0f, 0.0f, 0, 0);
        Memory->SetProgramIcon(&GameState->ProgramIcon);
#endif

        GameState->Backdrop = DEBUGLoadBMP(Thread,
            Memory->DEBUGPlatformReadEntireFile, "data/test_background.bmp");

        struct hero_bitmaps *Bitmap;

        Bitmap = &GameState->HeroBitmaps[0];
        Bitmap->AlignX = 72;
        Bitmap->AlignY = 182;
        Bitmap->Head   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_right_head.bmp");
        Bitmap->Cape   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_right_cape.bmp");
        Bitmap->Torso  = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_right_torso.bmp");
        Bitmap++;

        Bitmap->AlignX = 72;
        Bitmap->AlignY = 182;
        Bitmap->Head   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_back_head.bmp");
        Bitmap->Cape   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_back_cape.bmp");
        Bitmap->Torso  = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_back_torso.bmp");
        Bitmap++;

        Bitmap->AlignX = 72;
        Bitmap->AlignY = 182;
        Bitmap->Head   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_left_head.bmp");
        Bitmap->Cape   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_left_cape.bmp");
        Bitmap->Torso  = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_left_torso.bmp");
        Bitmap++;

        Bitmap->AlignX = 72;
        Bitmap->AlignY = 182;
        Bitmap->Head   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_front_head.bmp");
        Bitmap->Cape   = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_front_cape.bmp");
        Bitmap->Torso  = DEBUGLoadBMP(Thread,
                                      Memory->DEBUGPlatformReadEntireFile,
                                      "data/test_hero_front_torso.bmp");

        GameState->CameraP.AbsTileX = 17 / 2;
        GameState->CameraP.AbsTileY = 9 / 2;

        InitializeArena(&GameState->WorldArena,
            Memory->PermanentStorageSize - sizeof(struct game_state),
            (unsigned char *)Memory->PermanentStorage +
                sizeof(struct game_state));

        GameState->World = PUSH_STRUCT(&GameState->WorldArena, struct world);
        struct world *World = GameState->World;
        World->TileMap = PUSH_STRUCT(&GameState->WorldArena, struct tile_map);

        struct tile_map *TileMap = World->TileMap;

        TileMap->ChunkShift = 4;
        TileMap->ChunkMask = (1 << TileMap->ChunkShift) - 1;
        TileMap->ChunkDim = (1 << TileMap->ChunkShift);

        TileMap->TileChunkCountX = 128;
        TileMap->TileChunkCountY = 128;
        TileMap->TileChunkCountZ =   2;

        TileMap->TileChunks = PUSH_ARRAY(&GameState->WorldArena,
            TileMap->TileChunkCountX * TileMap->TileChunkCountY *
                TileMap->TileChunkCountZ,
            struct tile_chunk);

        TileMap->TileSideInMeters = 1.4f;

        unsigned int RandomNumberIndex = 0;

        unsigned int TilesPerWidth = 17;
        unsigned int TilesPerHeight =  9;
        unsigned int ScreenX = 0;
        unsigned int ScreenY = 0;

        unsigned int AbsTileZ = 0;

        int DoorTop    = 0;
        int DoorBottom = 0;
        int DoorLeft   = 0;
        int DoorRight  = 0;
        int DoorUp     = 0;
        int DoorDown   = 0;
        for(unsigned int ScreenIndex = 0; ScreenIndex < 100; ScreenIndex++) {
            ASSERT(RandomNumberIndex < ARRAY_SIZE(RandomNumberTable));

            /* TODO: Random number generator. */
            unsigned int RandomChoice;
            if(DoorUp || DoorDown) {
                RandomChoice = RandomNumberTable[RandomNumberIndex++] % 2;
            } else {
                RandomChoice = RandomNumberTable[RandomNumberIndex++] % 3;
            }

            int CreatedZDoor = 0;

            if(RandomChoice == 2) {
                CreatedZDoor = 1;

                if(AbsTileZ == 0) {
                    DoorUp = 1;
                } else {
                    DoorDown = 1;
                }
            } else if(RandomChoice == 1) {
                DoorRight = 1;
            } else {
                DoorTop = 1;
            }

            for(unsigned int TileY = 0;
                TileY < TilesPerHeight;
                TileY++)
            {
                for(unsigned int TileX = 0;
                    TileX < TilesPerWidth;
                    TileX++)
                {
                    unsigned int AbsTileX = ScreenX * TilesPerWidth + TileX;
                    unsigned int AbsTileY = ScreenY * TilesPerHeight + TileY;

                    unsigned int TileValue = 1;
                    if(TileX == 0 &&
                       (!DoorLeft || (TileY != (TilesPerHeight/2))))
                    {
                        TileValue = 2;
                    }

                    if(TileX == (TilesPerWidth - 1) &&
                       (!DoorRight || (TileY != (TilesPerHeight/2))))
                    {
                        TileValue = 2;
                    }

                    if(TileY == 0 &&
                       (!DoorBottom || (TileX  != (TilesPerWidth/2))))
                    {
                        TileValue = 2;
                    }

                    if(TileY == (TilesPerHeight - 1) &&
                       (!DoorTop || (TileX != (TilesPerWidth/2))))
                    {
                        TileValue = 2;
                    }

                    if((TileX == 10) && (TileY == 6)) {
                        if(DoorUp) {
                            TileValue = 3;
                        }
                        if(DoorDown) {
                            TileValue = 4;
                        }
                    }

                    SetTileValue(&GameState->WorldArena, World->TileMap,
                                 AbsTileX, AbsTileY, AbsTileZ, TileValue);
                }
            }

            DoorLeft   = DoorRight;
            DoorBottom = DoorTop;

            if(CreatedZDoor) {
                DoorDown = !DoorDown;
                DoorUp   = !DoorUp;
            } else {
                DoorUp   = 0;
                DoorDown = 0;
            }

            DoorTop    = 0;
            DoorRight  = 0;

            if(RandomChoice == 2) {
                if(AbsTileZ == 0) {
                    AbsTileZ = 1;
                } else {
                    AbsTileZ = 0;
                }
            } else if(RandomChoice == 1) {
                ScreenX++;
            } else {
                ScreenY++;
            }
        }

        Memory->IsInitialized = 1;
    }

    struct world *World = GameState->World;
    struct tile_map *TileMap = World->TileMap;

    int TileSideInPixels = 60;
    float MetersToPixels =
        (float)TileSideInPixels / TileMap->TileSideInMeters;

    for(unsigned int ControllerIndex = 0;
        ControllerIndex < ARRAY_SIZE(Input->Controllers);
        ControllerIndex++)
    {
        struct game_controller_input *Controller =
            GetController(Input, ControllerIndex);
        struct entity *ControllingEntity =
            GetEntity(GameState,
                      GameState->PlayerIndexForController[ControllerIndex]);
        if(ControllingEntity) {
            struct v2 ddPlayer; /* accerlation */
            memset(&ddPlayer, 0, sizeof(ddPlayer));

            if(Controller->IsAnalog) {
                ddPlayer = (struct v2){ Controller->StickAverageX,
                                        Controller->StickAverageY };
            } else {

                if(Controller->MoveUp.EndedDown) {
                    GameState->rect_pos.Y -= 1.0f;

                    ddPlayer.Y = 1.0f;
                }
                if(Controller->MoveDown.EndedDown) {
                    GameState->rect_pos.Y += 1.0f;

                    ddPlayer.Y = -1.0f;
                }
                if(Controller->MoveLeft.EndedDown) {
                    GameState->rect_pos.X -= 1.0f;

                    ddPlayer.X = -1.0f;
                }
                if(Controller->MoveRight.EndedDown) {
                    GameState->rect_pos.X += 1.0f;

                    ddPlayer.X = 1.0f;
                }

            }

            MovePlayer(GameState, ControllingEntity, Input->dtForFrame,
                       ddPlayer);
        } else {
            if(Controller->Start.EndedDown) {
                unsigned int EntityIndex = AddEntity(GameState);
                ControllingEntity = GetEntity(GameState, EntityIndex);
                InitializePlayer(ControllingEntity);
                GameState->PlayerIndexForController[ControllerIndex] =
                    EntityIndex;
            }
        }
    }

    struct entity *CameraFollowingEntity =
        GetEntity(GameState, GameState->CameraFollowingEntityIndex);
    if(CameraFollowingEntity) {
        GameState->CameraP.AbsTileZ = CameraFollowingEntity->P.AbsTileZ;

        struct tile_map_difference Diff =
            SubtractInFloat(TileMap, &CameraFollowingEntity->P,
                            &GameState->CameraP);
        if(Diff.dXY.X > (9.0f*TileMap->TileSideInMeters)) {
            GameState->CameraP.AbsTileX += 17;
        }
        if(Diff.dXY.X < -(9.0f*TileMap->TileSideInMeters)) {
            GameState->CameraP.AbsTileX -= 17;
        }
        if(Diff.dXY.Y > (5.0f*TileMap->TileSideInMeters)) {
            GameState->CameraP.AbsTileY += 9;
        }
        if(Diff.dXY.Y < -(5.0f*TileMap->TileSideInMeters)) {
            GameState->CameraP.AbsTileY -= 9;
        }
    }

    /*DrawRectangle(Buffer, 0.0f, 0.0f,
                  (F32)Buffer->Width, (F32)Buffer->Height,
                  0.0f, 1.0f, 0.0f);*/

    DrawBitmap(Buffer, &GameState->Backdrop, 0.0f, 0.0f, 0, 0);

    float ScreenCenterX = 0.5f * (float)Buffer->Width;
    float ScreenCenterY = 0.5f * (float)Buffer->Height;

    for(int RelRow = -10; RelRow < 10; RelRow++) {
        for(int RelColumn = -20; RelColumn < 20; RelColumn++) {
            unsigned int Column = GameState->CameraP.AbsTileX + RelColumn;
            unsigned int Row    = GameState->CameraP.AbsTileY + RelRow;

            unsigned int TileID = GetTileValue(TileMap, Column, Row,
                                               GameState->CameraP.AbsTileZ);

            if(TileID > 1) {
                float Gray = 0.5f;
                if(TileID == 2) {
                    Gray = 1.0f;
                }

                if(TileID > 2) {
                    Gray = 0.25f;
                }

                if(Column == GameState->CameraP.AbsTileX &&
                   Row == GameState->CameraP.AbsTileY)
                {
                    Gray = 0.0f;
                }

                struct v2 TileSide = { 0.5f*(float)TileSideInPixels,
                                       0.5f*(float)TileSideInPixels };
                struct v2 Center = { ScreenCenterX -
                    MetersToPixels*GameState->CameraP.Offset.X +
                        (float)RelColumn*(float)TileSideInPixels,
                    ScreenCenterY + MetersToPixels * 
                        GameState->CameraP.Offset.Y -
                            (float)RelRow*(float)TileSideInPixels };
                struct v2 Min = V2Subtract(Center, TileSide);
                struct v2 Max = V2Add(Center, TileSide);
                DrawRectangle(Buffer, Min, Max, Gray, Gray, Gray);
            }
        }
    }

    struct entity *Entity = GameState->Entities;
    for(unsigned int EntityIndex = 0;
        EntityIndex < GameState->EntityCount;
        EntityIndex++, Entity++)
    {
        if(Entity->Exists) {
            struct tile_map_difference Diff =
                SubtractInFloat(TileMap, &Entity->P, &GameState->CameraP);

            float PlayerR = 1.0f;
            float PlayerG = 0.0f;
            float PlayerB = 0.0f;
            float PlayerGroundPointX =
                ScreenCenterX + MetersToPixels*Diff.dXY.X;
            float PlayerGroundPointY =
                ScreenCenterY - MetersToPixels*Diff.dXY.Y;
            struct v2 PlayerLeftTop =
                { PlayerGroundPointX - 0.5f * MetersToPixels*Entity->Width,
                  PlayerGroundPointY - MetersToPixels*Entity->Height };
            struct v2 PlayerWidthHeight = { Entity->Width, Entity->Height };
            DrawRectangle(Buffer, PlayerLeftTop,
                          V2Add(PlayerLeftTop, V2Multiply(MetersToPixels,
                                                          PlayerWidthHeight)),
                          PlayerR, PlayerG, PlayerB);

            struct hero_bitmaps *Bitmap =
                &GameState->HeroBitmaps[Entity->FacingDirection];
            DrawBitmap(Buffer, &Bitmap->Torso,
                       PlayerGroundPointX, PlayerGroundPointY,
                       Bitmap->AlignX, Bitmap->AlignY);
            DrawBitmap(Buffer, &Bitmap->Cape,
                       PlayerGroundPointX, PlayerGroundPointY,
                       Bitmap->AlignX, Bitmap->AlignY);
            DrawBitmap(Buffer, &Bitmap->Head,
                       PlayerGroundPointX, PlayerGroundPointY,
                       Bitmap->AlignX, Bitmap->AlignY);

            /* TODO: Remove this. */
            /*DrawRectangle(&GameState->ProgramIcon, GameState->rect_pos,
                (struct v2){ GameState->rect_pos.X + 20.0f,
                             GameState->rect_pos.Y + 20.0f },
                0.8f, 0.8f, 0.8f);*/
            /*Memory->SetProgramIcon(&GameState->ProgramIcon);*/
        }
    }

    GameOutputSound(GameState, SoundBuffer, 400);
}

/*
static void RenderWeirdGradient(game_offscreen_buffer *Buffer,
                                int XOffset, int YOffset)
{
    int Width, Height, Y;
    U8 *Row;

    Width = Buffer->Width;
    Height = Buffer->Height;

    Row = (U8 *)Buffer->Memory;
    for(Y = 0; Y < Height; Y++) {
        unsigned int *Pixel = (unsigned int *)Row;
        int X;

        Pixel = (unsigned int *)Row;
        for(X = 0; X < Width; X++) {
            U8 Blue, Green;

            Blue = (U8)(X + XOffset);
            Green = (U8)(Y + YOffset);

            *Pixel = (Green << 8) | Blue;
            Pixel++;
        }
        Row += Buffer->Pitch;
    }
}
*/