# lighting.ludic — the 2D light-accumulation pass: Light.ambient (scene modulate),
# Light.point (additive radial glow with linear falloff), and Light.occlude /
# Light.clear_occluders (hard shadows). Each assertion that holds prints its
# number, so a full run prints:
#   1 2 3 4 5 6 7 8 9 10 11 12 13 14
# It lights the headless framebuffer and reads pixels back with Screen.pixel, so
# it verifies the actual composited result — not just that a call compiled. All
# deterministic (integer + Q16.16 fixed). Colours are 0x00RRGGBB.
program Lighting {
  property Tag { v: int = 0 }
  model Marker { Tag }

  handler Boot phase Start {
    let WHITE = 16777215      # 0xFFFFFF
    let RED   = 16711680      # 0xFF0000
    let BLUE  = 64            # 0x000040
    let GREY  = 8421504       # 0x808080 (128,128,128)

    # --- Light.ambient multiplies the whole scene by a tint (channel * a / 255) ---
    Screen.clear(0)
    Screen.put_pixel(5, 5, WHITE)
    Screen.put_pixel(6, 5, 0)
    Light.ambient(GREY)                            # white -> (128,128,128); black stays black
    if Screen.pixel(5, 5) == GREY { print(1) }
    if Screen.pixel(6, 5) == 0    { print(2) }

    # --- Light.point adds a radial glow, brightest at the centre, 0 at the radius ---
    Screen.clear(0)
    Light.point(50, 50, 20, WHITE, 1.0)
    if Screen.pixel(50, 50) == WHITE { print(3) }          # centre: full brightness
    if (Screen.pixel(60, 50) & 255) == 127 { print(4) }    # d=10: 255*10/20 = 127
    if Screen.pixel(75, 50) == 0 { print(5) }              # d=25 > radius: untouched

    # --- falloff is monotonic: nearer pixels are brighter ---
    if (Screen.pixel(55, 50) & 255) > (Screen.pixel(65, 50) & 255) { print(6) }
    if (Screen.pixel(55, 50) & 255) == 191 { print(7) }    # d=5:  255*15/20 = 191
    if (Screen.pixel(65, 50) & 255) == 63  { print(8) }    # d=15: 255*5/20  = 63

    # --- energy scales brightness (0.5 halves the centre) ---
    Screen.clear(0)
    Light.point(50, 50, 20, WHITE, 0.5)
    if (Screen.pixel(50, 50) & 255) == 127 { print(9) }    # 255 * 0.5 = 127

    # --- lights accumulate additively, clamped per channel at 255 ---
    Screen.clear(0)
    Light.point(50, 50, 20, BLUE, 1.0)
    Light.point(50, 50, 20, BLUE, 1.0)
    if (Screen.pixel(50, 50) & 255) == 128 { print(10) }   # 64 + 64
    Screen.clear(0)
    Light.point(50, 50, 20, RED, 2.0)                      # 255 * 2 -> clamp 255
    if ((Screen.pixel(50, 50) >> 16) & 255) == 255 { print(11) }

    # --- Light.occlude casts a hard shadow: a wall blocks the ray behind it ---
    Screen.clear(0)
    Light.clear_occluders()
    Light.occlude(60, 45, 4, 10)                   # a thin wall just right of the light
    Light.point(50, 50, 40, WHITE, 1.0)
    if Screen.pixel(75, 50) == 0        { print(12) }   # behind the wall: in shadow
    if (Screen.pixel(25, 50) & 255) != 0 { print(13) }  # opposite side: still lit

    # --- clearing occluders reopens the light ---
    Screen.clear(0)
    Light.clear_occluders()
    Light.point(50, 50, 40, WHITE, 1.0)
    if Screen.pixel(75, 50) != 0 { print(14) }     # no wall now: lit again
  }

  handler Run phase Update { quit() }
}