#include "geometry.h"

#include "buffer.h"
#include "constants.h"

#include <gfx_assert.h>

#include <math/vec2.h>
#include <math/vec3.h>

/// Determines whether a view is populated.
///
/// Note that views are allowed to have no data, in which case a buffer of the
/// specified size is created.
#define view_is_populated(BUFFER_VIEW) (BUFFER_VIEW.size_bytes > 0)

static GLenum primitive_type_to_gl(PrimitiveType type) {
  switch (type) {
  case Triangles:
    return GL_TRIANGLES;
  case TriangleFan:
    return GL_TRIANGLE_FAN;
  case TriangleStrip:
    return GL_TRIANGLE_STRIP;
  }
  FAIL("primitive_type_to_gl(): missing case");
  return GL_INVALID_ENUM;
}

/// Create a typed buffer for the buffer view if the view does not already point
/// to a buffer.
void init_view_buffer(
    GfxCore* gfxcore, BufferView* view, BufferType buffer_type,
    BufferUsage buffer_usage) {
  if (!view->buffer) {
    view->buffer = gfx_make_buffer(
        gfxcore,
        &(BufferDesc){
            .usage      = buffer_usage,
            .type       = buffer_type,
            .data.data  = view->data,
            .data.count = view->size_bytes /
                          gfx_get_buffer_type_size_bytes(buffer_type)});
  }
  assert(view->size_bytes <= view->buffer->size_bytes);
}

/// Configure the buffer in teh VAO.
static void configure_buffer(
    GfxCore* gfxcore, const GeometryDesc* desc, BufferView* view,
    size_t num_components, size_t component_size_bytes, GLenum component_type,
    GLboolean normalized, GLuint channel) {
  assert(gfxcore);
  assert(desc);
  assert(view);
  assert(view->buffer);
  assert(
      desc->num_verts <=
      view->size_bytes / (num_components * component_size_bytes));
  assert(view->size_bytes <= view->buffer->size_bytes);

  glBindBuffer(GL_ARRAY_BUFFER, view->buffer->vbo);
  glEnableVertexAttribArray(channel);
  if ((component_type == GL_FLOAT) || normalized) {
    glVertexAttribPointer(
        channel, num_components, component_type, normalized, view->stride_bytes,
        (const void*)view->offset_bytes);
  } else {
    assert(!normalized);
    assert(
        (component_type == GL_BYTE) || (component_type == GL_UNSIGNED_BYTE) ||
        (component_type == GL_SHORT) || (component_type == GL_UNSIGNED_SHORT) ||
        (component_type == GL_INT) || component_type == GL_UNSIGNED_INT);
    glVertexAttribIPointer(
        channel, num_components, component_type, view->stride_bytes,
        (const void*)view->offset_bytes);
  }
  glBindBuffer(GL_ARRAY_BUFFER, 0);
}

static bool configure_vertex_attributes(GfxCore* gfxcore, GeometryDesc* desc) {
  assert(gfxcore);
  assert(desc);

  if (view_is_populated(desc->positions3d)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->positions3d, Buffer3d, desc->buffer_usage);
    if (!desc->positions3d.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->positions3d, 3, sizeof(float),
        GL_FLOAT, GL_FALSE, GFX_POSITION_CHANNEL);
  } else if (view_is_populated(desc->positions2d)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->positions2d, Buffer2d, desc->buffer_usage);
    if (!desc->positions2d.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->positions2d, 2, sizeof(float),
        GL_FLOAT, GL_FALSE, GFX_POSITION_CHANNEL);
  }
  if (view_is_populated(desc->normals)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->normals, Buffer3d, desc->buffer_usage);
    if (!desc->normals.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->normals, 3, sizeof(float), GL_FLOAT,
        GL_FALSE, GFX_NORMAL_CHANNEL);
  }
  if (view_is_populated(desc->tangents)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->tangents, Buffer4d, desc->buffer_usage);
    if (!desc->tangents.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->tangents, 4, sizeof(float), GL_FLOAT,
        GL_FALSE, GFX_TANGENT_CHANNEL);
  }
  if (view_is_populated(desc->texcoords)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->texcoords, Buffer2d, desc->buffer_usage);
    if (!desc->texcoords.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->texcoords, 2, sizeof(float),
        GL_FLOAT, GL_FALSE, GFX_TEXCOORDS_CHANNEL);
  }
  if (view_is_populated(desc->joints.u8)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->joints.u8, BufferU8, desc->buffer_usage);
    if (!desc->joints.u8.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->joints.u8, 4, sizeof(uint8_t),
        GL_UNSIGNED_BYTE, GL_FALSE, GFX_JOINTS_CHANNEL);
  } else if (view_is_populated(desc->joints.u16)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->joints.u16, BufferU16, desc->buffer_usage);
    if (!desc->joints.u16.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->joints.u16, 4, sizeof(uint16_t),
        GL_UNSIGNED_SHORT, GL_FALSE, GFX_JOINTS_CHANNEL);
  }

  // If weights are given as unsigned integers, then they are normalized
  // when read by the shader.
  if (view_is_populated(desc->weights.u8)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->weights.u8, BufferU8, desc->buffer_usage);
    if (!desc->weights.u8.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->weights.u8, 4, sizeof(uint8_t),
        GL_UNSIGNED_BYTE, GL_TRUE, GFX_WEIGHTS_CHANNEL);
  } else if (view_is_populated(desc->weights.u16)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->weights.u16, BufferU16,
        desc->buffer_usage);
    if (!desc->weights.u16.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->weights.u16, 4, sizeof(uint16_t),
        GL_UNSIGNED_SHORT, GL_TRUE, GFX_WEIGHTS_CHANNEL);
  } else if (view_is_populated(desc->weights.floats)) {
    init_view_buffer(
        gfxcore, (BufferView*)&desc->weights.floats, BufferFloat,
        desc->buffer_usage);
    if (!desc->weights.floats.buffer) {
      return false;
    }
    configure_buffer(
        gfxcore, desc, (BufferView*)&desc->weights.floats, 4, sizeof(float),
        GL_FLOAT, GL_FALSE, GFX_WEIGHTS_CHANNEL);
  }

  return true;
}

static bool configure_indices(GfxCore* gfxcore, GeometryDesc* desc) {
  assert(gfxcore);
  assert(desc);

  if (view_is_populated(desc->indices8)) {
    assert(desc->num_indices > 0);
    assert(
        desc->num_indices <= desc->indices8.size_bytes / sizeof(VertexIndex8));
    init_view_buffer(
        gfxcore, (BufferView*)&desc->indices8, BufferU8, desc->buffer_usage);
    if (!desc->indices8.buffer) {
      return false;
    }
  } else if (view_is_populated(desc->indices16)) {
    assert(desc->num_indices > 0);
    assert(
        desc->num_indices <=
        desc->indices16.size_bytes / sizeof(VertexIndex16));
    init_view_buffer(
        gfxcore, (BufferView*)&desc->indices16, BufferU16, desc->buffer_usage);
    if (!desc->indices16.buffer) {
      return false;
    }
  }

  return true;
}

bool gfx_init_geometry(
    Geometry* geometry, GfxCore* gfxcore, const GeometryDesc* input_desc) {
  assert(geometry);
  assert(gfxcore);
  assert(input_desc);
  assert(
      view_is_populated(input_desc->positions3d) ||
      view_is_populated(input_desc->positions2d));
  assert(input_desc->num_verts > 0);

  geometry->mode      = primitive_type_to_gl(input_desc->type);
  geometry->desc      = *input_desc;
  geometry->num_verts = input_desc->num_verts;
  geometry->gfxcore   = gfxcore;

  // The geometry's copy of the descriptor is manipulated below. Create a
  // shorter name for it.
  GeometryDesc* desc = &geometry->desc;

  glGenVertexArrays(1, &geometry->vao);
  glBindVertexArray(geometry->vao);
  if (!configure_vertex_attributes(gfxcore, desc)) {
    goto cleanup;
  }
  if (!configure_indices(gfxcore, desc)) {
    goto cleanup;
  }
  glBindVertexArray(0);
  ASSERT_GL;

  return true;

cleanup:
  gfx_del_geometry(geometry);
  return 0;
}

void gfx_del_geometry(Geometry* geometry) {
  assert(geometry);
  if (geometry->vao) {
    glDeleteVertexArrays(1, &geometry->vao);
    geometry->vao = 0;
  }
}

void gfx_update_geometry(Geometry* geometry, const GeometryDesc* desc) {
  assert(geometry);
  assert(desc);
  // New geometry size cannot exceed original size.
  assert(desc->positions3d.size_bytes <= geometry->desc.positions3d.size_bytes);
  assert(desc->positions2d.size_bytes <= geometry->desc.positions2d.size_bytes);
  assert(desc->normals.size_bytes <= geometry->desc.normals.size_bytes);
  assert(desc->tangents.size_bytes <= geometry->desc.tangents.size_bytes);
  assert(desc->texcoords.size_bytes <= geometry->desc.texcoords.size_bytes);
  assert(desc->joints.u8.size_bytes <= geometry->desc.joints.u8.size_bytes);
  assert(desc->joints.u16.size_bytes <= geometry->desc.joints.u16.size_bytes);
  assert(desc->weights.u8.size_bytes <= geometry->desc.weights.u8.size_bytes);
  assert(desc->weights.u16.size_bytes <= geometry->desc.weights.u16.size_bytes);
  assert(
      desc->weights.floats.size_bytes <=
      geometry->desc.weights.floats.size_bytes);

  if (desc->positions3d.data) {
    // The geometry must already have an underlying GPU buffer.
    assert(geometry->desc.positions3d.buffer);
    gfx_update_buffer(
        geometry->desc.positions3d.buffer,
        &(BufferDataDesc){
            .vec3s = desc->positions3d.data,
            .count = desc->positions3d.size_bytes / sizeof(vec3)});
  }
  // TODO: more
  else {
    FAIL("TODO: gfx_update_geometry() - handle other buffer types");
  }

  if (desc->num_verts != 0) {
    geometry->num_verts = desc->num_verts;
  }
}

void gfx_render_geometry(const Geometry* geometry) {
  assert(geometry);
  assert(geometry->vao);

  const GeometryDesc* desc = &geometry->desc;
  glBindVertexArray(geometry->vao);

  if (desc->indices8.buffer) {
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, desc->indices8.buffer->vbo);
    glDrawElements(
        geometry->mode, desc->num_indices, GL_UNSIGNED_BYTE,
        (const void*)desc->indices8.offset_bytes);
  } else if (desc->indices16.buffer) {
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, desc->indices16.buffer->vbo);
    glDrawElements(
        geometry->mode, desc->num_indices, GL_UNSIGNED_SHORT,
        (const void*)desc->indices16.offset_bytes);
  } else {
    glDrawArrays(geometry->mode, 0, geometry->num_verts);
  }

  glBindVertexArray(0);
}

aabb3 gfx_get_geometry_aabb(const Geometry* geometry) {
  assert(geometry);
  return geometry->desc.aabb;
}