#include "SDL_video.h"
#include <unistd.h>
#define STB_IMAGE_IMPLEMENTATION
#include "../util/stb_image.h"

#include "gl.h"
#include "gl_2d_font.h"
#include "../util.h"

I32 SAMPLER_INDICES[255];
const I32 GL_WINDOW_MIN_W = 800;
const I32 GL_WINDOW_MIN_H = 600;
const I32 GL_WINDOW_ASPECT_W = 4;
const I32 GL_WINDOW_ASPECT_H = 3;

GL_DATA* gl_inst;

GL_DATA* gl_instance() {
  return gl_inst;
}

static void gl_apply_canvas_size( GL_DATA* gl, I32 width, I32 height );
static void gl_handle_window_size_change( GL_DATA* gl, I32 width, I32 height );
static void gl_update_screen_ratio_uniforms( GL_DATA* gl, I32 width, I32 height );

static void gl_query_canvas_size( GL_DATA* gl, I32* width, I32* height ) {
  I32 w = 0;
  I32 h = 0;
  if( gl && gl->window ) {
    SDL_GL_GetDrawableSize( gl->window, &w, &h );
    if( w <= 0 || h <= 0 )
      SDL_GetWindowSize( gl->window, &w, &h );
  }

  if( width ) *width = max( 1, w );
  if( height ) *height = max( 1, h );
}

static void gl_constrain_window_size( I32* width, I32* height ) {
  if( !width || !height )
    return;

  I32 in_w = max( GL_WINDOW_MIN_W, *width );
  I32 in_h = max( GL_WINDOW_MIN_H, *height );

  I32 keep_w_h = (I32)( ( (I64)in_w * GL_WINDOW_ASPECT_H + GL_WINDOW_ASPECT_W / 2 ) / GL_WINDOW_ASPECT_W );
  keep_w_h = max( GL_WINDOW_MIN_H, keep_w_h );

  I32 keep_h_w = (I32)( ( (I64)in_h * GL_WINDOW_ASPECT_W + GL_WINDOW_ASPECT_H / 2 ) / GL_WINDOW_ASPECT_H );
  keep_h_w = max( GL_WINDOW_MIN_W, keep_h_w );

  I32 d_keep_w = abs( keep_w_h - in_h );
  I32 d_keep_h = abs( keep_h_w - in_w );

  if( d_keep_w <= d_keep_h ) {
    *width = in_w;
    *height = keep_w_h;
  } else {
    *width = keep_h_w;
    *height = in_h;
  }
}

static void gl_handle_window_size_change( GL_DATA* gl, I32 width, I32 height ) {
  if( !gl || !gl->window )
    return;

  I32 target_w = width;
  I32 target_h = height;
  if( target_w <= 0 || target_h <= 0 )
    SDL_GetWindowSize( gl->window, &target_w, &target_h );

  gl_constrain_window_size( &target_w, &target_h );

  I32 wnd_w, wnd_h;
  SDL_GetWindowSize( gl->window, &wnd_w, &wnd_h );
  if( ( target_w != wnd_w || target_h != wnd_h ) && !gl->window_constraint_active ) {
    gl->window_constraint_active = 1;
    SDL_SetWindowSize( gl->window, target_w, target_h );
    gl->window_constraint_active = 0;
  }

  I32 draw_w, draw_h;
  gl_query_canvas_size( gl, &draw_w, &draw_h );
  gl_apply_canvas_size( gl, draw_w, draw_h );
}

static I32 SDLCALL gl_event_filter( void* userdata, SDL_Event* e ) {
  GL_DATA* gl = (GL_DATA*)userdata;
  if( !gl || !e )
    return 1;

  if( e->type == SDL_WINDOWEVENT ) {
    if( e->window.event == SDL_WINDOWEVENT_SIZE_CHANGED
     || e->window.event == SDL_WINDOWEVENT_RESIZED ) {
      gl_handle_window_size_change( gl, e->window.data1, e->window.data2 );

      if( gl->resize_repaint_cb && !gl->resize_repaint_active ) {
        gl->resize_repaint_active = 1;
        gl->resize_repaint_cb( gl->resize_repaint_userdata );
        gl->resize_repaint_active = 0;
      }
    }
  }

  return 1;
}

static void gl_apply_canvas_size( GL_DATA* gl, I32 width, I32 height ) {
  width = max( 1, width );
  height = max( 1, height );

  gl->canvas_size[0] = width;
  gl->canvas_size[1] = height;
  if( canvas ) {
    canvas[0] = width;
    canvas[1] = height;
  }

  gl->clip_start = { 0.f, 0.f };
  gl->clip_dim = { (F32)width, (F32)height };

  gl_update_screen_ratio_uniforms( gl, width, height );

  glViewport( 0, 0, width, height );
  glUseProgram( 0 );
}

static void gl_update_screen_ratio_uniforms( GL_DATA* gl, I32 width, I32 height ) {
  F32 screen_ratio[] = {
    2.f / (F32)max( 1, width ),
    2.f / (F32)max( 1, height ),
    1.f,
    1.f
  };

  gl->programs.each( fn( GL_SHADER_PROGRAM** it ) {
    glUseProgram( (*it)->id );
    I32 ratio_location = glGetUniformLocation( (*it)->id, "g_screenratio" );
    glUniform4fv( ratio_location, 1, &screen_ratio[0] );
  } );
}

GL_DATA* gl_create( I32* _canvas ) {
  if( gl_inst ) {
    dlog( "gl_create() : fatal: gl instance already exists\n" );
    abort();
  }

  if( !font_mutex.align )
    thread_mutex_init( &font_mutex );

  SDL_SetHint( SDL_HINT_WINDOWS_ENABLE_MESSAGELOOP, "1" );
  SDL_SetHint( SDL_HINT_WINDOWS_DPI_SCALING, "0" );
  SDL_SetHint( SDL_HINT_VIDEO_HIGHDPI_DISABLED, "1" );

  if( !!SDL_Init( SDL_INIT_VIDEO | SDL_VIDEO_OPENGL ) ) {
    dlog( "gl_create() could not init SDL: %s\n", SDL_GetError() );
    return 0;
  }

  SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE );
  SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 3 );
  SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 2 );
  SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
  SDL_GL_SetAttribute( SDL_GL_ACCELERATED_VISUAL, 1 );
  SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 24 );
  SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 );
  SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 );
  SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 );
  SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 );

  I32 start_w = _canvas[0];
  I32 start_h = _canvas[1];
  gl_constrain_window_size( &start_w, &start_h );

  GL_DATA* gl = new GL_DATA;
  gl->window = SDL_CreateWindow(
    "game",
    SDL_WINDOWPOS_CENTERED,
    SDL_WINDOWPOS_CENTERED,
    start_w,
    start_h,
    SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE
  );

  if( !gl->window ) {
    dlog( "gl_init() could not create window: %s\n", SDL_GetError() );
    delete gl;
    return 0;
  }

  SDL_SetWindowMinimumSize( gl->window, GL_WINDOW_MIN_W, GL_WINDOW_MIN_H );

  gl->ctx = SDL_GL_CreateContext( gl->window );
  if( !gl->ctx ) {
    dlog( "gl_init() could not create context: %s\n", SDL_GetError() );
    SDL_DestroyWindow( gl->window );
    delete gl;
    return 0;
  }

  SDL_GL_SetSwapInterval(0);
  SDL_GL_MakeCurrent( gl->window, gl->ctx );

  GLenum glewError = glewInit();
  if( glewError != GLEW_OK ) {
    dlog( "gl_create() : Failed to initialize GLEW: %s\n", glewGetErrorString(glewError) );
    SDL_GL_DeleteContext( gl->ctx );
    SDL_DestroyWindow( gl->window );
    delete gl;
    return 0;
  }

  while( glGetError() != GL_NO_ERROR ); // clear errors
                                        //
  glGetIntegerv( GL_MAX_TEXTURE_IMAGE_UNITS, &gl->shader_texture_limit );
  if( gl->shader_texture_limit > 255 )
    gl->shader_texture_limit = 255;
  for( U32 i = 0; i < 255; ++i )
    SAMPLER_INDICES[i] = i;

  gl->programs.clear();
  gl_handle_window_size_change( gl, start_w, start_h );
  SDL_SetEventFilter( gl_event_filter, gl );

  gl_inst = gl;
  return gl;
}

void gl_gen_buffers( GL_DATA* gl ) {
  glGenVertexArrays( 1, &gl->vao );
  glBindVertexArray( gl->vao );

  glGenBuffers( 1, &gl->vbuffer );
  glBindBuffer( GL_ARRAY_BUFFER, gl->vbuffer );
  glBufferData( GL_ARRAY_BUFFER, 8192, 0, GL_STATIC_DRAW );
  glBindBuffer( GL_ARRAY_BUFFER, 0 );
}

void gl_destroy( GL_DATA *gl ) {
  SDL_SetEventFilter( 0, 0 );

  gl->programs.each( fn( GL_SHADER_PROGRAM** it ) { gl_program_destroy( gl, *it ); } );
  gl->fonts.each( fn( GL_FONT** it ) { gl_font_destroy( gl, *it ); } );
  gl->textures.each( fn( GL_TEX2D** it )  { gl_texture_destroy( gl, *it ); } );

  if( gl->ctx )
    SDL_GL_DeleteContext( gl->ctx );
  if( gl->window )
    SDL_DestroyWindow( gl->window );

  free( gl );
}

void gl_update_window( GL_DATA* gl, I32* size ) {
  if( !gl->window )
    return;

  I32 width = size ? size[0] : 0;
  I32 height = size ? size[1] : 0;
  gl_constrain_window_size( &width, &height );
  SDL_SetWindowSize( gl->window, width, height );
  // this giga breaks on linux, is it needed?
  // SDL_SetWindowPosition( gl->window, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED );
  gl_handle_window_size_change( gl, width, height );
}

void gl_sync_window_size( GL_DATA* gl ) {
  if( !gl || !gl->window )
    return;

  SDL_PumpEvents();
  I32 w, h;
  SDL_GetWindowSize( gl->window, &w, &h );
  gl_handle_window_size_change( gl, w, h );
}

void gl_set_resize_repaint_callback( GL_DATA* gl, GL_RESIZE_REPAINT_CB cb, void* userdata ) {
  if( !gl )
    return;

  gl->resize_repaint_cb = cb;
  gl->resize_repaint_userdata = userdata;
}

STAT gl_shader_compile( GL_DATA* gl, GL_SHADER_DEF* shader ) {
  static char* log_buf = 0;
  if( !log_buf )
    log_buf = (char*)malloc( 8192 );

  I32 res;
  shader->id = glCreateShader( (GLenum)shader->type );
  glShaderSource( shader->id, 1, &shader->code, 0 );
  glCompileShader( shader->id );
  glGetShaderiv( shader->id, GL_COMPILE_STATUS, &res );

  if( !res ) {
    glGetShaderInfoLog( shader->id, 8192, 0, log_buf );
    dlog( "gl_shader_compile() : error compiling shader %s. log: \n%s\n%s", shader->name, log_buf, shader->code );

    glDeleteShader( shader->id );
    return STAT_ERR;
  }

  shader->compiled = 1;
  return STAT_OK;
}

void gl_shader_destroy( GL_DATA* gl, GL_SHADER_DEF* shader ) {
  if( shader->code )
    free( (void*)shader->code );
}

GL_SHADER_PROGRAM* gl_program_create( GL_DATA* gl, const char* name, U32 size ) {
  GL_SHADER_PROGRAM* program = (GL_SHADER_PROGRAM*)malloc( size );
  char        shader_string[256];
  char*       shader_code;

  sprintf( shader_string, "../assets/shaders/%s.vsh", name );
  shader_code = (char*)file_read( shader_string );
  if( !shader_code ) {
    dlog( "gl_program_create() : could not read shader file %s\n", shader_string );
    return 0;
  }

  program->vsh.name = name;
  program->vsh.type = GL_VERTEX_SHADER;
  program->vsh.code = shader_code;

  sprintf( shader_string, "../assets/shaders/%s.fsh", name );
  shader_code = (char*)file_read( shader_string );
  if( !shader_code ) {
    dlog( "gl_program_create() : could not read shader file %s\n", shader_string );
    return 0;
  }

  program->fsh.name = name;
  program->fsh.type = GL_FRAGMENT_SHADER;
  program->fsh.code = shader_code;

  program->name = name;
  program->gl = gl;

  gl->programs.push( program );
  return program;
}

STAT gl_program_compile( GL_DATA* gl, GL_SHADER_PROGRAM* program ) {
  static char* log_buf = 0;
  if( !log_buf )
    log_buf = (char*)malloc( 8192 );

  program->id = glCreateProgram();
  if( !OK( gl_shader_compile( gl, &program->fsh ) )
   || !OK( gl_shader_compile( gl, &program->vsh ) ) )
    return STAT_ERR;

  glAttachShader( program->id, program->fsh.id );
  glAttachShader( program->id, program->vsh.id );

  I32 status;
  glLinkProgram( program->id );
  glGetProgramiv( program->id, GL_LINK_STATUS, &status );
  if( !status ) {
    glGetProgramInfoLog( program->id, 8192, 0, log_buf );
    dlog( "gl_program_compile() : error compiling program %s. log: \n%s\n",
      program->name,
      log_buf
    );

    return STAT_ERR;
  }

  glGenBuffers( 1, &program->vbuffer );
  return STAT_OK;
}

void gl_program_destroy( GL_DATA* gl, GL_SHADER_PROGRAM* program ) {
  if( program->fsh.compiled )
    gl_shader_destroy( gl, &program->fsh );
  if( program->vsh.compiled )
    gl_shader_destroy( gl, &program->vsh );

  I32 idx = gl->programs.idx_of( program );
  if( idx != -1 )
    gl->programs.erase( idx );
}

GL_TEX2D* gl_texture_from_file( GL_DATA* gl, const char* name ) {
  char filename[256];
  sprintf( filename, "../assets/%s", name );

  I32 w, h, n;
  U8* data = stbi_load( filename, &w, &h, &n, STBI_rgb_alpha );
  if( !data ) {
    dlog( "gl_texture_create() : could not load image %s\n", filename );
    return 0;
  }

  GL_TEX2D* tex = gl_texture_create( gl, filename );
  glBindTexture( GL_TEXTURE_2D, tex->id );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

  glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, data );
  glGenerateMipmap( GL_TEXTURE_2D );
  glBindTexture( GL_TEXTURE_2D, 0 );

  tex->width = w;
  tex->height = h;

  stbi_image_free( data );

  return tex;
}

GL_TEX2D* gl_texture_from_bitmap( GL_DATA* gl, const char* name, U8* bitmap, U32 w, U32 h ) {
  GL_TEX2D* tex = gl_texture_create( gl, name );
  glBindTexture( GL_TEXTURE_2D, tex->id );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

  glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, bitmap );
  glGenerateMipmap( GL_TEXTURE_2D );
  glBindTexture( GL_TEXTURE_2D, 0 );

  tex->width = w;
  tex->height = h;

  return tex;
}

GL_TEX2D* gl_texture_create( GL_DATA* gl, const char* name ) {
  GL_TEX2D* tex = (GL_TEX2D*)malloc( sizeof(GL_TEX2D) );
  strcpy( tex->name, name );
  glGenTextures( 1, &tex->id );

  gl->textures.push( tex );
  return tex;
}

void gl_texture_destroy( GL_DATA* gl, GL_TEX2D* tex ) {
  glDeleteTextures( 1, &tex->id );
  I32 idx = gl->textures.idx_of( tex );
  if( idx != -1 )
    gl->textures.erase( idx );

  free( tex );
}

STAT gl_beginframe( GL_DATA* gl ) {
  glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  gl->last_tick = u_tick();
  return STAT_OK;
}

STAT gl_poll_events( GL_DATA* gl ) {
  SDL_Event e;
  while( SDL_PollEvent( &e ) ) {
    input_on_event( &e );

    switch( e.type ) {
      case SDL_QUIT:
        return STAT_BREAK;
      case SDL_WINDOWEVENT: {
        if( e.window.event == SDL_WINDOWEVENT_SIZE_CHANGED
         || e.window.event == SDL_WINDOWEVENT_RESIZED ) {
          gl_handle_window_size_change( gl, e.window.data1, e.window.data2 );
        }
      } break;
      case SDL_KEYDOWN:
        return e.key.keysym.sym == SDLK_ESCAPE ? STAT_BREAK : STAT_OK;
    default: break;
    }
  }

  return STAT_OK;
}

STAT gl_endframe( GL_DATA* gl ) {
  SDL_GL_SwapWindow( gl->window );

  // 1000 fps max be real
  while( true ) {
    U64 diff = u_tick() - gl->last_tick;
    if( diff < 10 )
      usleep( 10 );
    else break;
  }

  gl->frametime = (F32)(u_tick() - gl->last_tick) / 10000.0f;
  gl->fps = 1.0f / gl->frametime;

  input_frame_end();
  return STAT_OK;
}

void gl_set_clip( GL_DATA* gl, VEC2 start, VEC2 dim ) {
  gl->clip_start = start;
  gl->clip_dim = dim;

  glEnable( GL_SCISSOR_TEST );
  glScissor( start.x, gl->canvas_size[1] - (I32)(dim.y + start.y), dim.x, dim.y );
}

void gl_get_clip( GL_DATA* gl, VEC2* start, VEC2* dim ) {
  *start = gl->clip_start;
  *dim = gl->clip_dim;
}

void gl_reset_clip( GL_DATA* gl ) {
  glDisable( GL_SCISSOR_TEST );
  gl->clip_start = {};
  gl->clip_dim = { (F32)gl->canvas_size[0], (F32)gl->canvas_size[1] };
}

void gl_set_viewport( GL_DATA* gl, VEC2 start, VEC2 dim ) {
  I32 vpy = (I32)gl->canvas_size[1] - start.y - dim.y;
  glViewport( (I32)start.x, vpy, (I32)dim.x, (I32)dim.y );
  gl_update_screen_ratio_uniforms( gl, (I32)dim.x, (I32)dim.y );

  gl->viewport_start = start;
  gl->viewport_dim = dim;
}

void gl_get_viewport( GL_DATA* gl, VEC2* start, VEC2* dim ) {
  *start = gl->viewport_start;
  *dim = gl->viewport_dim;
}