#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <glad/gl.h>

#include <daw/types.h>
#include <daw/logging.h>

#include <daw/rendering.h>
#include <daw/daw.h>

extern Instance* GLOBAL_PLATFORM;

const char* ShaderType_str[] = {
  [Shader_Error] = "Shader_Error",
  [Shader_Program] = "Shader_Program",
  [Shader_Vertex] = "Shader_Vertex",
  [Shader_Tessellation] = "Shader_Tessellation",
  [Shader_Geometry] = "Shader_Geometry",
  [Shader_Fragment] = "Shader_Fragment",
  [Shader_Compute] = "Shader_Compute",
};

Shader compile_shader(const char* source, const ShaderType shader_type) {
  const GladGLContext* gl = GLOBAL_PLATFORM->window->context;

  i32 Result = GL_FALSE;
  i32 infolog_len;

  GLenum shadertype = GL_INVALID_ENUM;

  switch (shader_type) {
    case Shader_Vertex:
      shadertype = GL_VERTEX_SHADER;
      break;
    case Shader_Fragment:
      shadertype = GL_FRAGMENT_SHADER;
      break;
    default:
      UNIMPLEMENTED;
      break;
  }

  u32 shaderID = gl->CreateShader(shadertype);
  LOG("CREATED SHADER ID %d", shaderID);

  char const* src_ptr = source;
  gl->ShaderSource(shaderID, 1, &src_ptr , NULL);
  gl->CompileShader(shaderID);

  // Check shader
  gl->GetShaderiv(shaderID, GL_COMPILE_STATUS, &Result);
  gl->GetShaderiv(shaderID, GL_INFO_LOG_LENGTH, &infolog_len);
  if (infolog_len > 0) {
    char* msg = calloc((usize)infolog_len + 1, sizeof(char));
    gl->GetShaderInfoLog(shaderID, infolog_len, NULL, msg);
    ERROR("Failed to compile shader: " TERM_COLOR_YELLOW "%s" TERM_COLOR_RESET, msg);
    free(msg);
  }

  return (Shader){.program = shaderID, .type = shader_type};
}

Shader compile_shader_f(const char* file_path, const ShaderType shader_type) {
  Shader s;

  char* source = NULL;
  FILE* file = NULL;

  if (file_path == NULL) {
    WARN("Empty path to shader");
    return (Shader){.program = 0, .type = Shader_Error};
  }

  file = fopen(file_path, "r");

  if(file != NULL) {
    const usize size = f_get_sz(file);

    source = calloc((usize)size + 1, sizeof(char));

    // Assume the whole file is successfully read
    fread(source, sizeof(char), (usize)size, file);

    fclose(file);
  } else {
    ERROR("Cannot open \"" TERM_COLOR_YELLOW "%s" TERM_COLOR_RESET"\".", file_path);
    return (Shader){.program = 0, .type = Shader_Error};
  }

  // Compile shader
  INFO("Compiling shader \"" TERM_COLOR_YELLOW "%s" TERM_COLOR_RESET"\".", file_path);

  s = compile_shader(source, shader_type);

  free(source);

  return s;
}


// http://www.opengl-tutorial.org/beginners-tutorials/tutorial-2-the-first-triangle/
u32 load_shaders(
    const GladGLContext* gl,
    const char* vertex_file_path,
    const char* fragment_file_path) {

  i32 Result = GL_FALSE;
  i32 infolog_len;

  // Create the shaders
  const Shader vertexShader = compile_shader_f(vertex_file_path, Shader_Vertex);
  const Shader fragmentShader = compile_shader_f(fragment_file_path, Shader_Fragment);

  // Link the program
  INFO("Linking program");
  u32 ProgramID = gl->CreateProgram();

  if (vertex_file_path != NULL) gl->AttachShader(ProgramID, vertexShader.program);
  if (fragment_file_path != NULL) gl->AttachShader(ProgramID, fragmentShader.program);

  gl->LinkProgram(ProgramID);

  // Check the program
  gl->GetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
  gl->GetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &infolog_len);
  if ( infolog_len > 0 ){
    char* msg = calloc((usize)infolog_len  + 1, sizeof(char));
    gl->GetShaderInfoLog(ProgramID, infolog_len, NULL, msg);
    ERROR("Compiling shader: " TERM_COLOR_YELLOW "%s" TERM_COLOR_RESET, msg);
    free(msg);
  }

  gl->DetachShader(ProgramID, vertexShader.program);
  gl->DetachShader(ProgramID, fragmentShader.program);

  //gl->DeleteShader(vertexShader.program);
  //gl->DeleteShader(fragmentShader.program);

  return ProgramID;
}

/* Returns a shader program */
Shader compose_shader(Shader *shaders, usize shaders_len) {
  const GladGLContext* gl = GLOBAL_PLATFORM->window->context;
  i32 Result = GL_FALSE;

  if (shaders_len == 0) {
    ERROR("No shaders provided!");
    return (Shader){.program = 0, .type = Shader_Error};
  }

  u32 prog = gl->CreateProgram();

  if (prog == 0) {
    ERROR("Failed to create program!");
    return (Shader){.program = 0, .type = Shader_Error};
  }

  for (usize i = 0; i < shaders_len; i++) {
    gl->AttachShader(prog, shaders[i].program);
    INFO("Attaching shader %d to %d", shaders[i].program, prog);
  }

  gl->LinkProgram(prog);

  // Check the program
  gl->GetProgramiv(prog, GL_LINK_STATUS, &Result);
  if (Result != GL_TRUE) {
    // Get the size of the log
    i32 log_len = 0;
    i32 msg_len = 0;
    gl->GetProgramiv(prog, GL_INFO_LOG_LENGTH, &log_len);
    char* msg = calloc((usize)log_len + 1, sizeof(char));

    // Copy the log message(s)
    gl->GetProgramInfoLog(prog, log_len, &msg_len, msg);

    ERROR("(Compose) Compiling shader:\n" TERM_COLOR_YELLOW "%s" TERM_COLOR_RESET "\n", msg);
    free(msg);
  }

  for (usize i = 0; i < shaders_len; i++) {
    gl->DetachShader(prog, shaders[i].program);
  }

  return (Shader){.program = prog, .type = Shader_Program};
}

/* Free up resources associated with `shader` */
void shaders_delete(Shader* shader, usize shader_len) {
  const GladGLContext* gl = GLOBAL_PLATFORM->window->context;

  for (usize i = 0; i < shader_len; i++) {
    gl->DeleteShader(shader[i].program);
  }
}

GLenum ShaderBuffer_get_gl_access(u64 flags) {
  const ShaderBufferFlag access = ShaderBuffer_get_access_type(flags);

  switch(flags & 7) { // Stored in the first 3 bits
    case ShaderBuffer_AccessFrequency_stream:
      switch(access) {
        case ShaderBuffer_AccessType_draw: return GL_STREAM_DRAW;
        case ShaderBuffer_AccessType_read: return GL_STREAM_READ;
        case ShaderBuffer_AccessType_copy: return GL_STREAM_COPY;
        default: return GL_STREAM_DRAW;
      }
    case ShaderBuffer_AccessFrequency_static:
      switch(access) {
        case ShaderBuffer_AccessType_draw: return GL_STATIC_DRAW;
        case ShaderBuffer_AccessType_read: return GL_STATIC_READ;
        case ShaderBuffer_AccessType_copy: return GL_STATIC_COPY;
        default: return GL_STATIC_DRAW;
      }
    case ShaderBuffer_AccessFrequency_dynamic:
      switch(access) {
        case ShaderBuffer_AccessType_draw: return GL_DYNAMIC_DRAW;
        case ShaderBuffer_AccessType_read: return GL_DYNAMIC_READ;
        case ShaderBuffer_AccessType_copy: return GL_DYNAMIC_COPY;
        default: return GL_DYNAMIC_DRAW;
      }
    default: return GL_STATIC_DRAW;
  }
}

RenderObject RenderObject_new(
    Shader* shader,
    u32 texture,
    ShaderBuffer *restrict buffers, usize num_buffers) {

  GladGLContext *gl = GLOBAL_PLATFORM->window->context;
  RenderObject o;

  gl->CreateVertexArrays(1, &(o.vao));
  gl->BindVertexArray(o.vao);

  /* For each buffer in the shader, */
  /* The shader should be generalied, */
  for (usize i = 0; i < num_buffers; i++) {
    const usize sz = buffers[i].size_elem * buffers[i].count;

    gl->CreateBuffers(1, &(buffers[i].buffername));
    gl->NamedBufferData(buffers[i].buffername, (isize)sz, buffers[i].data, ShaderBuffer_get_gl_accesstype(buffers[i].buffertype));
  }

  o.shader = *shader;
  o.texture = texture;
  o.texture_len = 1;
  o.buffer = buffers;
  o.buffer_len = num_buffers;
  o.mvp = gl->GetUniformLocation(o.shader.program, "MVP");
  o.model_position = gl->GetUniformLocation(o.shader.program, "modelPosition");

  // It is very much a non-issue if we don't find the model view projection in
  // the shader. In fact, it is removed from a shader program if it is not used.
  // TODO: Add common uniforms, should be a list of strings (uniform name) &
  // their locations (i32), such as
  // * mouse coords,
  // * time,
  // * delta time,
  // * modelviewprojection,
  // * window size.
  // These should be added to the RenderObject, if found.

  // if (o.mvp == -1) {
  //  WARN("Unable to find \"MVP\" input in shader program");
  //}

  gl->BindVertexArray(0);


  return o;
}

ShaderType guess_shadertype_from_filename(const char *restrict fname) {
  const usize path_len = strlen(fname);

  if (path_len <= 4) {
    ERROR("Unable to determine shader type from suffix! (%s)", fname);
    return Shader_Error;
  }

  if (!strncmp(".vert", &fname[path_len - 5], 5)) { return Shader_Vertex; }
  if (!strncmp(".frag", &fname[path_len - 5], 5)) { return Shader_Fragment; }

  return Shader_Error;
}