#include "config.h"

#include "gskglshaderbuilderprivate.h"

#include "gskdebugprivate.h"

#include <gdk/gdk.h>
#include <epoxy/gl.h>

void
gsk_gl_shader_builder_init (GskGLShaderBuilder *self,
                            const char         *vs_preamble_resource_path,
                            const char         *fs_preamble_resource_path)
{
  memset (self, 0, sizeof (*self));

  self->vs_preamble = g_resources_lookup_data (vs_preamble_resource_path, 0, NULL);
  self->fs_preamble = g_resources_lookup_data (fs_preamble_resource_path, 0, NULL);

  g_assert (self->vs_preamble);
  g_assert (self->fs_preamble);
}

void
gsk_gl_shader_builder_finish (GskGLShaderBuilder *self)
{
  g_bytes_unref (self->vs_preamble);
  g_bytes_unref (self->fs_preamble);
}

void
gsk_gl_shader_builder_set_glsl_version (GskGLShaderBuilder *self,
                                        int                 version)
{
  self->version = version;
}

static gboolean
check_shader_error (int     shader_id,
                    GError **error)
{
  int status;
  int log_len;
  char *buffer;
  int code_len;
  char *code;

  glGetShaderiv (shader_id, GL_COMPILE_STATUS, &status);

  if (G_LIKELY (status == GL_TRUE))
    return TRUE;

  glGetShaderiv (shader_id, GL_INFO_LOG_LENGTH, &log_len);
  buffer = g_malloc0 (log_len + 1);
  glGetShaderInfoLog (shader_id, log_len, NULL, buffer);

  glGetShaderiv (shader_id, GL_SHADER_SOURCE_LENGTH, &code_len);
  code = g_malloc0 (code_len + 1);
  glGetShaderSource (shader_id, code_len, NULL, code);

  g_set_error (error, GDK_GL_ERROR, GDK_GL_ERROR_COMPILATION_FAILED,
               "Compilation failure in shader.\nError message: %s\n\nSource code:\n%s\n\n",
               buffer,
               code);

  g_free (buffer);
  g_free (code);

  return FALSE;
}

int
gsk_gl_shader_builder_create_program (GskGLShaderBuilder  *self,
                                      const char          *resource_path,
                                      GError             **error)
{

  GBytes *source_bytes = g_resources_lookup_data (resource_path, 0, NULL);
  char version_buffer[64];
  const char *source;
  const char *vertex_shader_start;
  const char *fragment_shader_start;
  int vertex_id;
  int fragment_id;
  int program_id = -1;
  int status;

  g_assert (source_bytes);

  source = g_bytes_get_data (source_bytes, NULL);
  vertex_shader_start = strstr (source, "VERTEX_SHADER");
  fragment_shader_start = strstr (source, "FRAGMENT_SHADER");

  g_assert (vertex_shader_start);
  g_assert (fragment_shader_start);

  /* They both start at the next newline */
  vertex_shader_start = strstr (vertex_shader_start, "\n");
  fragment_shader_start = strstr (fragment_shader_start, "\n");

  g_snprintf (version_buffer, sizeof (version_buffer),
              "#version %d\n", self->version);

  vertex_id = glCreateShader (GL_VERTEX_SHADER);
  glShaderSource (vertex_id, 7,
                  (const char *[]) {
                    version_buffer,
                    self->debugging ? "#define GSK_DEBUG 1\n" : "",
                    self->legacy ? "#define GSK_LEGACY 1\n" : "",
                    self->gl3 ? "#define GSK_GL3 1\n" : "",
                    self->gles ? "#define GSK_GLES 1\n" : "",
                    g_bytes_get_data (self->vs_preamble, NULL),
                    vertex_shader_start
                  },
                  (int[]) {
                    -1,
                    -1,
                    -1,
                    -1,
                    -1,
                    -1,
                    fragment_shader_start - vertex_shader_start
                  });
  glCompileShader (vertex_id);

  if (!check_shader_error (vertex_id, error))
    {
      glDeleteShader (vertex_id);
      goto out;
    }

  fragment_id = glCreateShader (GL_FRAGMENT_SHADER);
  glShaderSource (fragment_id, 7,
                  (const char *[]) {
                    version_buffer,
                    self->debugging ? "#define GSK_DEBUG 1\n" : "",
                    self->legacy ? "#define GSK_LEGACY 1\n" : "",
                    self->gl3 ? "#define GSK_GL3 1\n" : "",
                    self->gles ? "#define GSK_GLES 1\n" : "",
                    g_bytes_get_data (self->fs_preamble, NULL),
                    fragment_shader_start
                  },
                  (int[]) {
                    -1,
                    -1,
                    -1,
                    -1,
                    -1,
                    -1,
                    -1,
                  });
  glCompileShader (fragment_id);

  if (!check_shader_error (fragment_id, error))
    {
      glDeleteShader (fragment_id);
      goto out;
    }

  program_id = glCreateProgram ();
  glAttachShader (program_id, vertex_id);
  glAttachShader (program_id, fragment_id);
  glLinkProgram (program_id);

  glGetProgramiv (program_id, GL_LINK_STATUS, &status);
  if (status == GL_FALSE)
    {
      char *buffer = NULL;
      int log_len = 0;

      glGetProgramiv (program_id, GL_INFO_LOG_LENGTH, &log_len);

      buffer = g_malloc0 (log_len + 1);
      glGetProgramInfoLog (program_id, log_len, NULL, buffer);

      g_warning ("Linking failure in shader:\n%s", buffer);
      g_set_error (error, GDK_GL_ERROR, GDK_GL_ERROR_LINK_FAILED,
                   "Linking failure in shader: %s", buffer);

      g_free (buffer);

      glDeleteProgram (program_id);

      goto out;
    }

  glDetachShader (program_id, vertex_id);
  glDeleteShader (vertex_id);

  glDetachShader (program_id, fragment_id);
  glDeleteShader (fragment_id);

out:
  g_bytes_unref (source_bytes);

  return program_id;
}