renderer.nim

import private/gl

import util, maths, shapes#, shader

# const
#   DefVertSrc = slurp("private/shader/default.vert")
#   DefFragSrc = slurp("private/shader/default.frag")

const VertexSize = sizeof(Vertex)
const DefMaxVertices = 50_000

type
  BufferBit* {.pure.} = enum
    Color = GL_COLOR_BUFFER_BIT.BufferBit
    Depth = GL_DEPTH_BUFFER_BIT.BufferBit
    Stencil = GL_STENCIL_BUFFER_BIT.BufferBit

# var default_shader: Shader
var batch: tuple[vao, vbo: GLuint, size: uint, index: uint]

var clear_color: Vec4f
var clear_mask: BufferBit = ColorBufferBit or DepthBufferBit

proc r_init*()
proc r_destroy*()
proc r_batch_max_vert_count*(count: uint) = batch.size = count * VertexSize.uint

proc r_init() = 
  if batch.size == 0: batch.size = DefMaxVertices * VertexSize

  # default_shader = create_shader(DefVertSrc, DefFragSrc)

  glGenVertexArrays(1, addr batch.vao)
  glBindVertexArray(batch.vao)
  glGenBuffers(1, addr batch.vbo)
  glBindBuffer(GL_ARRAY_BUFFER, batch.vbo)
  glBufferData(GL_ARRAY_BUFFER, GLsizeiptr(batch.size), nil, GL_DYNAMIC_DRAW)
  glVertexAttribPointer(0, 3, cGL_FLOAT, false, GLsizei(VertexSize), cast[pointer](offsetof(Vertex, pos)))
  glVertexAttribPointer(1, 3, cGL_FLOAT, false, GLsizei(VertexSize), cast[pointer](offsetof(Vertex, norm)))
  glVertexAttribPointer(2, 2, cGL_FLOAT, false, GLsizei(VertexSize), cast[pointer](offsetof(Vertex, uv)))
  glEnableVertexAttribArray(0)
  glEnableVertexAttribArray(1)
  glEnableVertexAttribArray(2)
  glBindVertexArray(0)
  glBindBuffer(GL_ARRAY_BUFFER, 0)
  
proc r_destroy() =
  # delete_shader(default_shader)
  glDeleteVertexArrays(1, addr batch.vao)
  glDeleteBuffers(1, addr batch.vbo)

proc clear_bits_set*(mask: BufferBit) = clear_mask = mask

proc clear_color_set*(color: Vec4f) = 
  clear_color = color
  glClearColor(clear_color.r, clear_color.g, clear_color.b, clear_color.a)

proc clear*() =
  glClear(@clear_mask)

proc clear*(color: Vec4f) =
  clear_color_set(color)
  glClear(@clear_mask)

proc draw_circle*(pos: Vec3f, radius: float, color: Vec4f)
# proc draw_circle(pos: Vec2f, radius: float, color: Vec4f)
# proc draw_circle(x, y: float, radius: float, color: Vec4f)

proc draw_circle(pos: Vec3f, radius: float, color: Vec4f) = 
  let vertices = gen_circle(radius, 32)
  glBindBuffer(GL_ARRAY_BUFFER, batch.vbo)
  # glBufferSubData(GL_ARRAY_BUFFER, batch.index.int * VertexSize, len(vertices) * VertexSize, unsafeAddr(vertices[0]))
  batch.index += len(vertices).uint

proc r_flush*() =
  # use(default_shader)
  glBindVertexArray(batch.vao)
  glDrawArrays(GL_TRIANGLES, 0, GLsizei(batch.index))
  batch.index = 0