# ============================================================================
# gl.ludic — Gl.*: OpenGL for Ludic.
#
# The whole OpenGL 4.1 core API is available as Gl.<snake_name>(...) — every
# entry point of the platform gl3.h is bound in gl_api.ludic (generated), with
# every GL_* constant. float/double parameters take `fixed`; buffers are the raw
# `bytes`/`words` pointers Ludic already has, and pixel/vertex data is uploaded
# from them as-is. This file adds the small amount of glue the API needs to be
# usable from a game: a context on the window (or an offscreen one headless),
# the swap, a screenshot, shader/program helpers, and IEEE float helpers so a
# program can fill a vertex buffer with real floats from its Q16.16 math.
#
# Windowed: the NSOpenGLContext is attached to the existing LudicView (cocoa.ll)
# at the display's backing resolution. Headless: a CGL context with no drawable
# (gl.ll) and a framebuffer object that stands in for the screen, so the same
# program renders and screenshots byte-identically under the test harness.
# ============================================================================

import "gl_api.ludic"

# ---- native glue (cocoa.ll / gl.ll) -------------------------------------------
extern function win_gl_attach() -> int = "win_gl_attach"
extern function win_gl_resize(w: int, h: int) = "win_gl_resize"
extern function win_gl_swap() = "win_gl_swap"
extern function win_gl_scale() -> int = "win_gl_scale"
extern function win_gl_swap_interval(n: int) = "win_gl_swap_interval"
extern function win_gl_drawable(out: pointer) = "win_gl_drawable"
extern function win_gl_update() = "win_gl_update"
extern function win_gl_retina(on: int) = "win_gl_retina"
extern function win_toggle_fullscreen() = "win_toggle_fullscreen"
extern function cgl_offscreen() -> int = "cgl_offscreen"
# wall clock in microseconds — the only sub-second clock available to a Ludic program
extern function gl_now_us() -> long = "gl_now_us"
extern function fx_to_f32(fx: fixed) -> int = "fx_to_f32"
extern function f32_to_fx(bits: int) -> fixed = "f32_to_fx"
extern function mem_off(p: pointer, off: int) -> pointer = "mem_off"
extern function mem_get_i32(p: pointer, off: int) -> int = "mem_get_i32"
extern function mem_put_i32(p: pointer, off: int, v: int) = "mem_put_i32"
extern function mem_get_u16(p: pointer, off: int) -> int = "mem_get_u16"
extern function mem_put_u16(p: pointer, off: int, v: int) = "mem_put_u16"
extern function mem_get_u8(p: pointer, off: int) -> int = "mem_get_u8"
extern function mem_put_u8(p: pointer, off: int, v: int) = "mem_put_u8"
extern function mem_get_f32(p: pointer, i: int) -> fixed = "mem_get_f32"
extern function mem_put_f32(p: pointer, i: int, v: fixed) = "mem_put_f32"
extern function mem_get_f32_bits(p: pointer, i: int) -> int = "mem_get_f32_bits"
extern function mem_put_f32_bits(p: pointer, i: int, bits: int) = "mem_put_f32_bits"
extern function mem_copy(dst: pointer, src: pointer, n: int) = "mem_copy"
extern function mem_set(dst: pointer, v: int, n: int) = "mem_set"
# IEEE-754 single precision, carried as its bit pattern in an int
extern function f_add(a: int, b: int) -> int = "f_add"
extern function f_sub(a: int, b: int) -> int = "f_sub"
extern function f_mul(a: int, b: int) -> int = "f_mul"
extern function f_div(a: int, b: int) -> int = "f_div"
extern function f_neg(a: int) -> int = "f_neg"
extern function f_sqrt(a: int) -> int = "f_sqrt"
extern function f_abs(a: int) -> int = "f_abs"
extern function f_sin(a: int) -> int = "f_sin"
extern function f_cos(a: int) -> int = "f_cos"
extern function f_tan(a: int) -> int = "f_tan"
extern function f_atan2(a: int, b: int) -> int = "f_atan2"
extern function f_pow(a: int, b: int) -> int = "f_pow"
extern function f_exp(a: int) -> int = "f_exp"
extern function f_log(a: int) -> int = "f_log"
extern function f_floor(a: int) -> int = "f_floor"
extern function f_mod(a: int, b: int) -> int = "f_mod"
extern function f_ldexp(a: int, e: int) -> int = "f_ldexp"
extern function f_min(a: int, b: int) -> int = "f_min"
extern function f_max(a: int, b: int) -> int = "f_max"
extern function f_lt(a: int, b: int) -> int = "f_lt"
extern function f_from_int(a: int) -> int = "f_from_int"
extern function f_to_int(a: int) -> int = "f_to_int"

# ---- state --------------------------------------------------------------------
var gl_is_open: bool = false
var gl_w:       int  = 0          # drawable width, in pixels
var gl_h:       int  = 0
var gl_scale:   int  = 1          # backing pixels per window point
var gl_screen:  int  = 0          # the framebuffer that is "the screen" (an FBO headless)
var gl_ids:     words = null      # one-word scratch for glGen*/glGet*

function gl_scratch() -> words {
  if gl_ids == null { gl_ids = words(4) }
  return gl_ids
}

# Open a GL 4.1 core context on a w x h (points) window titled `title`; headless,
# an offscreen context with a w x h framebuffer standing in for the screen.
function gl_open(width: int, height: int, title: pointer) -> bool {
  if gl_is_open { return true }
  if is_windowed() {
    if win_gl_attach() == 0 {
      win_open(width, height, 1, title)               # a plain program: no window yet
      if win_gl_attach() == 0 { return false }
    }
    win_gl_resize(width, height)
    gl_scale = win_gl_scale()
    gl_w = width * gl_scale
    gl_h = height * gl_scale
    gl_screen = 0
  } else {
    if cgl_offscreen() == 0 { return false }
    gl_scale = 1
    gl_w = width
    gl_h = height
    gl_screen = gl_make_screen_fbo(width, height)
  }
  gl_bind_framebuffer(GL_FRAMEBUFFER, gl_screen)
  gl_viewport(0, 0, gl_w, gl_h)
  gl_is_open = true
  return true
}

function gl_make_screen_fbo(w: int, h: int) -> int {
  let ids = gl_scratch()
  gl_gen_framebuffers(1, ids)
  let fbo = ids[0]
  gl_bind_framebuffer(GL_FRAMEBUFFER, fbo)
  gl_gen_textures(1, ids)
  let tex = ids[0]
  gl_bind_texture(GL_TEXTURE_2D, tex)
  gl_tex_image2d(GL_TEXTURE_2D, 0, GL_RGBA8, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, null)
  gl_tex_parameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
  gl_tex_parameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
  gl_framebuffer_texture2d(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0)
  gl_gen_renderbuffers(1, ids)
  let rb = ids[0]
  gl_bind_renderbuffer(GL_RENDERBUFFER, rb)
  gl_renderbuffer_storage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, w, h)
  gl_framebuffer_renderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rb)
  return fbo
}

# Did the drawable change size (a window drag, full screen, a Retina switch)? Then
# gl_w / gl_h follow it and the caller rebuilds its screen-sized targets.
var gl_size_buf: words = null
function gl_resize_check() -> bool {
  if not is_windowed() or not gl_is_open { return false }
  if gl_size_buf == null { gl_size_buf = words(4) }
  win_gl_drawable(gl_size_buf)
  let w = gl_size_buf[0];  let h = gl_size_buf[1]
  if w <= 0 or h <= 0 { return false }
  if w == gl_w and h == gl_h { return false }
  win_gl_update()
  gl_w = w;  gl_h = h
  gl_scale = win_gl_scale()
  gl_viewport(0, 0, gl_w, gl_h)
  return true
}
function gl_set_window(w: int, h: int) -> void { if is_windowed() { win_gl_resize(w, h) } }
function gl_toggle_fullscreen() -> void { if is_windowed() { win_toggle_fullscreen() } }
function gl_set_retina(on: bool) -> void { if is_windowed() { var v = 0;  if on { v = 1 };  win_gl_retina(v) } }
# vsync on (1, the default) or off (0); headless has nothing to sync to
function gl_vsync(n: int) -> void { if is_windowed() { win_gl_swap_interval(n) } }
function gl_width() -> int { return gl_w }
function gl_height() -> int { return gl_h }
function gl_screen_fbo() -> int { return gl_screen }
function gl_pixel_scale() -> int { return gl_scale }

# Present the frame (vsync'd flushBuffer); headless, just finish the GPU work.
function gl_swap() -> void {
  if is_windowed() { win_gl_swap() }
  else { gl_finish() }
}

# Write what is on the screen framebuffer to a binary PPM (call before Gl.swap).
function gl_screenshot(path: pointer) -> bool {
  let w = gl_w
  let h = gl_h
  let f = file_open(path, "wb")
  if f == null { return false }
  let buf = bytes(w * h * 3)
  gl_bind_framebuffer(GL_READ_FRAMEBUFFER, gl_screen)
  gl_pixel_storei(GL_PACK_ALIGNMENT, 1)
  gl_read_pixels(0, 0, w, h, GL_RGB, GL_UNSIGNED_BYTE, buf)
  let hdr = `P6\n{w} {h}\n255\n`
  file_write(f, hdr, len(hdr))
  var y = h - 1
  while y >= 0 {
    file_write(f, mem_off(buf, y * w * 3), w * 3)
    y -= 1
  }
  file_close(f)
  free(buf)
  return true
}

# Print any pending GL error under a tag; returns the error code (0 = none).
function gl_check(tag: pointer) -> int {
  let e = gl_get_error()
  if e != 0 { print(`gl error {e} at {tag}`) }
  return e
}

# ---- shaders --------------------------------------------------------------------
var gl_log_buf: string = null

# Compile one shader stage from source; 0 (and the info log on stdout) on failure.
function gl_shader(kind: int, src: pointer) -> int {
  let id = gl_create_shader(kind)
  var srcs: pointers = bytes(8)
  srcs[0] = src
  gl_shader_source(id, 1, srcs, null)
  gl_compile_shader(id)
  let ids = gl_scratch()
  gl_get_shaderiv(id, GL_COMPILE_STATUS, ids)
  if ids[0] == 0 {
    if gl_log_buf == null { gl_log_buf = bytes(8192) }
    gl_get_shader_info_log(id, 8191, null, gl_log_buf)
    print("shader compile failed:")
    print(gl_log_buf)
    gl_delete_shader(id)
    return 0
  }
  return id
}

# Link a program from a vertex + fragment source pair; 0 on failure.
function gl_program(vs: pointer, fs: pointer) -> int {
  return gl_program5(vs, null, null, null, fs)
}

# Link a program from up to five stages (null = stage absent).
function gl_program5(vs: pointer, tcs: pointer, tes: pointer, gs: pointer, fs: pointer) -> int {
  let prog = gl_create_program()
  var ok = true
  if vs != null  { let s = gl_shader(GL_VERTEX_SHADER, vs);           if s == 0 { ok = false } else { gl_attach_shader(prog, s) } }
  if tcs != null { let s = gl_shader(GL_TESS_CONTROL_SHADER, tcs);    if s == 0 { ok = false } else { gl_attach_shader(prog, s) } }
  if tes != null { let s = gl_shader(GL_TESS_EVALUATION_SHADER, tes); if s == 0 { ok = false } else { gl_attach_shader(prog, s) } }
  if gs != null  { let s = gl_shader(GL_GEOMETRY_SHADER, gs);         if s == 0 { ok = false } else { gl_attach_shader(prog, s) } }
  if fs != null  { let s = gl_shader(GL_FRAGMENT_SHADER, fs);         if s == 0 { ok = false } else { gl_attach_shader(prog, s) } }
  if not ok { gl_delete_program(prog); return 0 }
  gl_link_program(prog)
  let ids = gl_scratch()
  gl_get_programiv(prog, GL_LINK_STATUS, ids)
  if ids[0] == 0 {
    if gl_log_buf == null { gl_log_buf = bytes(8192) }
    gl_get_program_info_log(prog, 8191, null, gl_log_buf)
    print("program link failed:")
    print(gl_log_buf)
    gl_delete_program(prog)
    return 0
  }
  return prog
}

function gl_uniform(prog: int, name: pointer) -> int { return gl_get_uniform_location(prog, name) }

# ---- buffers of floats ------------------------------------------------------------
# A float buffer is plain memory: n IEEE floats, filled from fixed (Gl.put) or
# from float bits (Gl.put_bits), uploaded with Gl.buffer_data(…, Gl.bytes_of(n), buf, …).
function gl_floats(n: int) -> pointer { return bytes(n * 4) }
function gl_bytes_of(n: int) -> int { return n * 4 }
function gl_put(buf: pointer, i: int, v: fixed) -> void { mem_put_f32(buf, i, v) }
function gl_get(buf: pointer, i: int) -> fixed { return mem_get_f32(buf, i) }
function gl_put_bits(buf: pointer, i: int, bits: int) -> void { mem_put_f32_bits(buf, i, bits) }
function gl_get_bits(buf: pointer, i: int) -> int { return mem_get_f32_bits(buf, i) }
function gl_ptr(buf: pointer, byte_offset: int) -> pointer { return mem_off(buf, byte_offset) }
function gl_f32(v: fixed) -> int { return fx_to_f32(v) }
function gl_fixed(bits: int) -> fixed { return f32_to_fx(bits) }

# One VAO, one VBO helper: create a vertex array object and return it, bound.
function gl_vao() -> int {
  let ids = gl_scratch()
  gl_gen_vertex_arrays(1, ids)
  gl_bind_vertex_array(ids[0])
  return ids[0]
}
function gl_buffer() -> int {
  let ids = gl_scratch()
  gl_gen_buffers(1, ids)
  return ids[0]
}
function gl_texture() -> int {
  let ids = gl_scratch()
  gl_gen_textures(1, ids)
  return ids[0]
}
function gl_framebuffer() -> int {
  let ids = gl_scratch()
  gl_gen_framebuffers(1, ids)
  return ids[0]
}