#include <windows.h>
#include <direct.h>
#include <glad/glad.h>
#include <GLFW/glfw3.h>

#define STB_TRUETYPE_IMPLEMENTATION
#include "stb_truetype.h"
#include <math.h> 
#include <stdio.h>
#include <stdint.h>

typedef  uint8_t  u8;
typedef  uint16_t u16;
typedef  uint32_t u32;
typedef  uint64_t u64;

typedef  int8_t   i8;
typedef  int16_t  i16;
typedef  int32_t  i32;
typedef  int64_t  i64;

typedef  u8       b8;
typedef  u16      b16;
typedef  u32      b32;

typedef  float    f32;
typedef  double   f64;

#include "math.h"

#define WIN_WIDTH 1280.0f
#define WIN_HEIGHT 1024.0f
#define internal static

/**
 * Font rendering todos:
 * - Look into font-packing, what is that? why is it needed?
 * - Look into generating a single bitmap and then extracting characters from the 
 *   bitmap as needed
 * - SDF font rendering
 * */
internal i64 GlobalPerfCountFrequency;

i8 PlatformDebugReadFile(char *FileName, void *FileBuffer, u32 MaxSize, LPDWORD BytesRead)
{
  // @todo: refactor function, check for closehandle error codes
  HANDLE FileHandle = CreateFileA(FileName, GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
  if (FileHandle != INVALID_HANDLE_VALUE)
  {
    if (ReadFile(FileHandle, FileBuffer, MaxSize, BytesRead, NULL) != 0)
    {
      CloseHandle(FileHandle);
      return 1;
    }
    else
    {
      // @todo: logging
      CloseHandle(FileHandle);
      return -2;
    }
  }
  else
  {
    // @todo: logging
    return -1;
  }
}

void PlatformCopyMemory(void *NewMem, void *OldMem, size_t CopySize)
{
  CopyMemory(NewMem, OldMem, CopySize);
}

void PlatformZeroMemory(void *Ptr, size_t Size)
{
  ZeroMemory(Ptr, Size);
}

void framebuffer_size_callback(GLFWwindow *window, i32 width, i32 height)
{
    glViewport(0, 0, width, height);
}

inline LARGE_INTEGER
Win32GetWallClock(void)
{
    LARGE_INTEGER Result;
    QueryPerformanceCounter(&Result);
    
    return Result;
}

inline f32
Win32GetSecondsElapsed(LARGE_INTEGER Start, LARGE_INTEGER End)
{
    f32 Result = (f32)(End.QuadPart - Start.QuadPart)/(f32)GlobalPerfCountFrequency;
    return(Result);
}


#include "amr_memory.c"
#include "gl_graphics.cpp"
#include "game_main.h"

typedef struct amr_glyph_info {
  u32 charset_start_index;
  u32 charset_end_index;
} amr_glyph_info;

u32 amr_GetGlyphIdFromCodepoint(amr_glyph_info glyph, u32 *GlyphIndexArray, u32 Codepoint)
{
  u32 glyph_id = *(GlyphIndexArray + (Codepoint - glyph.charset_start_index));
  return glyph_id;
}

int main()
{
    // ==================== PROGRAM STATE INITIALISATION =====================
    LARGE_INTEGER PerfCountFrequencyResult;
    QueryPerformanceFrequency(&PerfCountFrequencyResult);
    GlobalPerfCountFrequency = PerfCountFrequencyResult.QuadPart;
    
    // Note(talha): Set Windows scheduler granularity to 1ms
    // so that our sleep can be more granular
    UINT DesiredSchedulerMS = 1;
    b8 SleepIsGranular = (timeBeginPeriod(DesiredSchedulerMS) == TIMERR_NOERROR);
    
    // TODO(talha): how to use a library to query this
    i32 MonitorRefreshHz = 60;
    i32 GameUpdateHz = MonitorRefreshHz;
    f32 TargetSecondsPerFrame = 1.0f / (f32)GameUpdateHz;

    GameState State = {0};
    State.Input.LastMouseX = WIN_WIDTH/2.0f;
    State.Input.LastMouseY = WIN_HEIGHT/2.0f;
    State.WinDimsPx.x = WIN_WIDTH;
    State.WinDimsPx.y = WIN_HEIGHT;
    
    // ================= GLFW WINDOW INITIALISATION ==========================
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    
    GLFWwindow *Window = glfwCreateWindow((i32)State.WinDimsPx.x, (i32)State.WinDimsPx.y, "LearnOpenGL", NULL, NULL);
    if (Window == NULL)
    {
        // todo(talha): add error logging for failed to create glfw window
        glfwTerminate();
        printf("ERROR: Failed to create a glfw window\n");
        return -1;
    }
    
    glfwMakeContextCurrent(Window);
    
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        // todo(talha): error logging - failed to initialize glad
        printf("ERROR: Failed to initialise glad\n");
        return -1;
    }

    glViewport(0, 0, (GLsizei)State.WinDimsPx.x, (GLsizei)State.WinDimsPx.y);
    glfwSetFramebufferSizeCallback(Window, framebuffer_size_callback);
    //glfwSetInputMode(Window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    glfwSetCursorPos(Window, State.Input.LastMouseX, State.Input.LastMouseY);
    
    LARGE_INTEGER LastCounter = Win32GetWallClock();
    u64 LastCycleCount = __rdtsc();

    size_t PermanentStorageSize = MB((u64)500);
    void *PermanentStorage = VirtualAlloc(NULL, PermanentStorageSize, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
    if (PermanentStorage == NULL)
    {
      printf("ERROR: Failed to allocate game memory\n");
      return -1;
    }
    State.Memory.PermanentStorage = PermanentStorage;
    State.Memory.PermanentStorageSize = PermanentStorageSize;

    amr_ArenaInit(&State.Memory.Arena, State.Memory.PermanentStorage, State.Memory.PermanentStorageSize);

    // ======================= SHADER PROGRAM LOADING ========
    DWORD BytesRead = 0;
    u32 max_fsz = MB((u64)5);
    u8 *vs_file = (u8 *)amr_ArenaAlloc(&State.Memory.Arena, max_fsz);
    if (PlatformDebugReadFile("./code/shaders/text.vs.glsl", vs_file, max_fsz, &BytesRead) != 1)
    {
      printf("ERROR: failed to open text vertex shader");
      return -1;
    }

    u8 *fs_file = (u8 *)amr_ArenaAlloc(&State.Memory.Arena, max_fsz);
    if (PlatformDebugReadFile("./code/shaders/text.fs.glsl", fs_file, max_fsz, &BytesRead) != 1)
    {
      printf("ERROR: failed to open text vertex shader");
      return -1;
    }

    u32 vs = CreateVertexShader((char *)vs_file);
    u32 fs = CreateFragmentShader((char *)fs_file);
    u32 sp = CreateShaderProgram(vs, fs);

    amr_ArenaFreeAll(&State.Memory.Arena);

    // =================== FONT RENDERING ===================
    u32 font_fz = MB(2);
    u8 *ArialBuffer = (u8 *)amr_ArenaAlloc(&State.Memory.Arena, font_fz);

    // @todo: change to PlatformDebugFileRead
    fread(ArialBuffer, 1, font_fz, fopen("c:/windows/fonts/arial.ttf", "rb"));

    stbtt_fontinfo font_info;
    if (!stbtt_InitFont(&font_info, ArialBuffer, 0))
    {
      printf("ERROR: failed to read arial font");
      assert(1 == 0);
    }

    // get a SF (scale factor)
    f32 SF = stbtt_ScaleForPixelHeight(&font_info, 32.0f);

    // get vertical metrics
    i32 f_ascent, f_descent, f_line_gap;
    stbtt_GetFontVMetrics(&font_info, &f_ascent, &f_descent, &f_line_gap);

    // ========================= GLYPH AND FONT INFO STORAGE ================
    amr_glyph_info latin_basic = {32, 126};
    u32 glyph_count = latin_basic.charset_end_index - latin_basic.charset_start_index;
    u32 *GlyphIndexArray = (u32 *)amr_ArenaAlloc(&State.Memory.Arena, sizeof(glyph_count) * glyph_count);
    u32 *glyph_array_iter = GlyphIndexArray;
    for (u32 i = 0; i < glyph_count; i++)
    {
      *glyph_array_iter = stbtt_FindGlyphIndex(&font_info, latin_basic.charset_start_index + i);
       glyph_array_iter++;
    }

    const char *text = "Hello this is a\npiece of test text \nor and more on a newline.";
    u8 char_sz = 61;

    u32 fd_sz = sizeof(debug_font_details)*char_sz;

    debug_font_details *fd_arr = (debug_font_details *)amr_ArenaAlloc(&State.Memory.Arena, fd_sz);
    debug_font_details *_fi = fd_arr;

    f32 lx = 0.0f, max_lx = 0.0f;
    i32 baseline = (i32)roundf(f_ascent * SF);
    // convert str to font
    for (i32 i = 0; i < char_sz; ++i)
    {
      _fi->lx = lx;
      _fi->baseline = baseline;

      if (text[i] == '\n')
      {
        // if new line, move baseline down
        baseline += (i32)roundf((f_ascent - f_descent + f_line_gap) * SF);
        lx = 0;
        ++_fi;
        continue;
      }

      stbtt_GetGlyphHMetrics(&font_info, amr_GetGlyphIdFromCodepoint(latin_basic, GlyphIndexArray, text[i]), &_fi->advance, &_fi->lsb);
      stbtt_GetGlyphBitmapBox(&font_info, amr_GetGlyphIdFromCodepoint(latin_basic, GlyphIndexArray, text[i]), SF, SF, &_fi->x0, &_fi->y0, &_fi->x1, &_fi->y1);

      _fi->ly = (f32)(_fi->baseline + _fi->y0);
      lx += (_fi->advance * SF);
      
      i32 kern;
      if (i < char_sz - 1 && text[i+1] != '\n')
      {
        kern = stbtt_GetGlyphKernAdvance(&font_info, amr_GetGlyphIdFromCodepoint(latin_basic, GlyphIndexArray, text[i]), amr_GetGlyphIdFromCodepoint(latin_basic, GlyphIndexArray, text[i+1]));
        lx += roundf(kern * SF);
      }

      if (lx > max_lx)
      {
          max_lx = lx;
      }
      ++_fi;
    }

    // make all the glyphs into bitmaps. 
    _fi = fd_arr;
    u32 bitmap_width_from_text_info = (u32)max_lx;
    u32 bitmap_height_from_text_info = (u32)(baseline - roundf(SF * f_descent));
    
    i32 bmp_sz = sizeof(u8)*bitmap_width_from_text_info*bitmap_height_from_text_info;
    u8 *Bitmap = (u8 *)amr_ArenaAlloc(&State.Memory.Arena, bmp_sz);

    _fi = fd_arr;
    for (int i=0; i<char_sz; i++)
    {
      if (text[i] == '\n') {
        ++_fi;
        continue;
      }
      _fi->byte_offset = (i32)(_fi->lx + roundf(_fi->lsb * SF) + (_fi->ly * bitmap_width_from_text_info)) ;
      // store image data in bitmap
      stbtt_MakeGlyphBitmap(&font_info, Bitmap + _fi->byte_offset, _fi->x1 - _fi->x0, _fi->y1 - _fi->y0, bitmap_width_from_text_info, SF, SF, amr_GetGlyphIdFromCodepoint(latin_basic, GlyphIndexArray, text[i]));
      _fi++;
    }

    // ---------- prepare bitmap texture and buffer objects -----------
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    f32 bmp_vertices[] = {
          // positions          // texture coords
         1.0f,  1.0f, 0.0f,     1.0f, 1.0f,// top right
         1.0f, -1.0f, 0.0f,     1.0f, 0.0f,// bottom right
        -1.0f, -1.0f, 0.0f,     0.0f, 0.0f,// bottom left
        -1.0f,  1.0f, 0.0f,     0.0f, 1.0f // top left 
    };
    u32 bmp_vsz = sizeof(bmp_vertices);

    u32 bmp_indices[] = {
      0, 1, 3,
      1, 2, 3
    };
    u32 bmp_isz = sizeof(bmp_indices);

    BufferO bo = CreateRectangleTextured(bmp_vertices, bmp_vsz, bmp_indices, bmp_isz, ATTR_TEX);
    Texture2D _tex = {0};
    {
      _tex.width = bitmap_width_from_text_info;
      _tex.height = bitmap_height_from_text_info;
      _tex.data = Bitmap;

      glBindVertexArray(bo.VAO);
      glGenTextures(1, &bo.TexO);
      glBindTexture(GL_TEXTURE_2D, bo.TexO);
      // defining texture wrapping options
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
      glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, _tex.width, _tex.height, 0, GL_RED, GL_UNSIGNED_BYTE, _tex.data);
      glBindVertexArray(0);
    }

    // =============== CAMERA SETUP ==================

    State.Camera.Pos = {0};
    State.Camera.Front = {0};
    State.Camera.Front.z = -1.0f;
    State.Camera.Up = {0};
    State.Camera.Up.y = 1.0f;
    State.Camera.MoveSpeed = 0.1f;
    State.Input.Sensitivity = 0.1f;

    // ======= SCREEN POSITIONING AND OBJECT SCALING SETUP ========

    // recalculated each time resolution changes
    // store in state
    Vec2 pixel_span; 
    pixel_span.x = State.WinDimsPx.x*2.0f/State.WinDimsPx.y;
    pixel_span.y = State.WinDimsPx.y*2.0f/State.WinDimsPx.x;

    Vec2 pixel_ratio;
    pixel_ratio.x = pixel_span.x/State.WinDimsPx.x;
    pixel_ratio.y = pixel_span.y/State.WinDimsPx.y;

    State.px_ratio = pixel_ratio;

    Vec2 win_dims;
    win_dims = State.px_ratio * State.WinDimsPx;

    // calculate screen mid point in view pixels and world position
    // @note: calculated each time player moves
    Vec2 ScreenMidCoords = {State.Camera.Pos.x, State.Camera.Pos.y};
    Vec2 ScreenMidPx = State.WinDimsPx/2.0f;
    // calculate corner points of the field:
    // tl -> top left
    // br -> bot right
    State.ScreenCoords.tl = ScreenMidCoords - ScreenMidPx;
    State.ScreenCoords.br = ScreenMidCoords + ScreenMidPx;

    // ====================== TEXT POSITIONING AND SCALING ======
    Vec2 text_dims = {((f32)bitmap_width_from_text_info)/2.0f, ((f32)bitmap_height_from_text_info)/2.0f};
    Vec2 text_scaled_dims = State.px_ratio * text_dims;
    Vec2 text_scaled_mid = text_scaled_dims/2.0f; 
    
    Vec2 text_pos = {0.0f, 0.0f};
    Vec2 text_offset = {text_dims.x/2.0f, (f32)fd_arr->baseline};
    text_pos = text_offset + text_pos;
    Vec2 text_scaled_pos = State.px_ratio*(State.ScreenCoords.tl + text_pos) + text_scaled_mid;
    

    // ===================== TEXTURE BINDING ===================
    glUseProgram(sp);
    glBindVertexArray(bo.VAO);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, bo.TexO);
    LoadUniformInt(sp, "tex", 0);
    LoadUniformVec3(sp, "TextColor", InitVec3(1.0f, 1.0f, 1.0f));

    while (!glfwWindowShouldClose(Window)) {
        LARGE_INTEGER WorkCounter = Win32GetWallClock();
        f32 WorkSecondsElapsed = Win32GetSecondsElapsed(LastCounter, WorkCounter);
        
        f32 SecondsElapsedForFrame = WorkSecondsElapsed;
        // @note: this caps the framerate
        // also prevents, for now, incorrect speeds based on timings
        // @todo: fix framerate capping and speed timings being affected by framerate
        if(SecondsElapsedForFrame < TargetSecondsPerFrame){
            while(SecondsElapsedForFrame < TargetSecondsPerFrame)
            {
                if (SleepIsGranular)
                {
                    DWORD SleepMS = (DWORD)(1000.0f * (TargetSecondsPerFrame - SecondsElapsedForFrame));
                    if (SleepMS > 0) 
                    {
                        Sleep(SleepMS);
                    }
                }
                SecondsElapsedForFrame = Win32GetSecondsElapsed(LastCounter, 
                                                                Win32GetWallClock());
            }
        }
        else
        {
            // TODO(talha): Missed frame rate
            // TODO(talha): Logging
        }

        glfwPollEvents();
        // HandleInputs
        if (glfwGetKey(Window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        {
            glfwSetWindowShouldClose(Window, 1);
        }
        if (glfwGetKey(Window, GLFW_KEY_W) == GLFW_PRESS)
        {
          State.Camera.Pos = State.Camera.Pos + (State.Camera.Front * State.Camera.MoveSpeed);
        }
        if (glfwGetKey(Window, GLFW_KEY_S) == GLFW_PRESS)
        {
          State.Camera.Pos = State.Camera.Pos + ((State.Camera.Front * State.Camera.MoveSpeed) * -1.0f);
        }
        if (glfwGetKey(Window, GLFW_KEY_A) == GLFW_PRESS)
        {
          Vec3 HorizontalVec = (UnitVec3(CrossProductVec3(State.Camera.Front, State.Camera.Up)) * State.Camera.MoveSpeed);
          State.Camera.Pos = (State.Camera.Pos + (HorizontalVec * -1.0f));
        }
        if (glfwGetKey(Window, GLFW_KEY_D) == GLFW_PRESS)
        {
          Vec3 HorizontalVec = (UnitVec3(CrossProductVec3(State.Camera.Front, State.Camera.Up)) * State.Camera.MoveSpeed);
          State.Camera.Pos = State.Camera.Pos + HorizontalVec;
        }

        Mat4 LookAt = CreateLookAtMat4(State.Camera.Pos, State.Camera.Pos + State.Camera.Front, State.Camera.Up);
        Mat4 View = LookAt;
        // projection matrix
        // far value is the max z-index value. Will be useful for layering textures
        Mat4 Projection = CreateOrthographicWithRatio(WIN_WIDTH, WIN_HEIGHT, -5.0f, 5.0f); 
        
        const f32 view[16] = {View.x0, View.x1, View.x2, View.x3,
            View.y0, View.y1, View.y2, View.y3,
            View.z0, View.z1, View.z2, View.z3,
            View.w0, View.w1, View.w2, View.w3};
        const f32 projection[16] = {Projection.x0, Projection.x1, Projection.x2, Projection.x3,
            Projection.y0, Projection.y1, Projection.y2, Projection.y3,
            Projection.z0, Projection.z1, Projection.z2, Projection.z3,
            Projection.w0, Projection.w1, Projection.w2, Projection.w3};
        LoadUniformMat4(sp, "View", view);
        LoadUniformMat4(sp, "Projection", projection);

        glEnable(GL_DEPTH_TEST);
        // glEnable(GL_BLEND);
        // glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);


        // ============== DRAW WOOD CONTAINER ===============
        Mat4 Model = IdentityMat();

#if 0
        Mat4 Scale1 = CreateScaleMat(InitVec4(container_dims.x, container_dims.y, 1.0f, 0));
        Model = Mul_Mat4Mat4(Scale1, Model);
        Mat4 Tx1 = CreateTranslationMat(InitVec4(container_pos.x, container_pos.y, -1.0f, 0));
        Model = Mul_Mat4Mat4(Tx1, Model);

        const f32 container_model[16] = {Model.x0, Model.x1, Model.x2, Model.x3,
              Model.y0, Model.y1, Model.y2, Model.y3,
              Model.z0, Model.z1, Model.z2, Model.z3,
              Model.w0, Model.w1, Model.w2, Model.w3};
        LoadUniformMat4(sp, "Model", container_model);
        DrawRectangleTextured(bo.VAO, Textures[0]);

        // ============ DRAW FIELD ======================
        Model = IdentityMat();

        Mat4 Scale2 = CreateScaleMat(InitVec4(field_dims.x, field_dims.y, 1.0f, 0));
        Mat4 Tx = CreateTranslationMat(InitVec4(0, 0, -2.0f, 0));
        Model = Mul_Mat4Mat4(Scale2, Model);
        Model = Mul_Mat4Mat4(Tx, Model);

        const f32 field_model[16] = {Model.x0, Model.x1, Model.x2, Model.x3,
              Model.y0, Model.y1, Model.y2, Model.y3,
              Model.z0, Model.z1, Model.z2, Model.z3,
              Model.w0, Model.w1, Model.w2, Model.w3};
        LoadUniformMat4(sp, "Model", field_model);
        DrawRectangleTextured(bo.VAO, Textures[1]);
#endif

        // =============== DRAW TEXT BITMAP RENDERING ===============
        {
          Model = IdentityMat();
          Mat4 Scale = CreateScaleMat(InitVec4(text_scaled_dims.x, text_scaled_dims.y, 1, 0));
          Model = Mul_Mat4Mat4(Scale, Model);
          Mat4 Tx = CreateTranslationMat(InitVec4(text_scaled_pos.x, text_scaled_pos.y, 0, 0));
          Model = Mul_Mat4Mat4(Tx, Model);

          const f32 text_model[16] = {Model.x0, Model.x1, Model.x2, Model.x3,
                Model.y0, Model.y1, Model.y2, Model.y3,
                Model.z0, Model.z1, Model.z2, Model.z3,
                Model.w0, Model.w1, Model.w2, Model.w3};
          LoadUniformMat4(sp, "Model", text_model);
          DrawRectangleTextured(bo.VAO, bo.TexO);
        }


        glfwSwapBuffers(Window);
        // TODO(talha): should these be cleared
        LastCounter = Win32GetWallClock();
        LastCycleCount = __rdtsc();
    };

    VirtualFree(PermanentStorage, 0, MEM_RELEASE);
    glfwTerminate();
    return 0;
}