"""First-person cockpit camera from the player vehicle's 0x1f pose.
  py fp_render.py <fifodump> <out.png> [upoff] [worldup_y] [fwd_sign]"""
import os, sys, struct
os.environ.setdefault('SDL_VIDEODRIVER', 'dummy')
import numpy as np
from _backend import pick_renderer, save_frame
from vrboard import VirtualBoard, Msg, A
Renderer, backend = pick_renderer()

data = open(sys.argv[1], 'rb').read()
out = sys.argv[2]
upoff = float(sys.argv[3]) if len(sys.argv) > 3 else 8.0
wuy   = float(sys.argv[4]) if len(sys.argv) > 4 else 1.0     # worldup y sign
fsign = float(sys.argv[5]) if len(sys.argv) > 5 else 1.0     # nose sign
board = VirtualBoard()
off = 0
while off + 8 <= len(data):
    if data[off:off + 4] != b'VPXM':
        off += 1; continue
    ln = struct.unpack_from('<I', data, off + 4)[0]
    body = data[off + 8:off + 8 + ln]; off += 8 + ln
    if len(body) >= 4:
        a = struct.unpack_from('<I', body, 0)[0]
        if a < 0x100:
            try: board.handle(Msg(False, 0xff, a, body[4:]))
            except Exception: pass

r = Renderer(w=832, h=512)
c = r.cache; c.maybe_rebuild(board)
anim = board.anim_abs
chain = c.cam_chain
h = None
if chain and chain[-1] in anim:
    h = chain[-1]
elif anim:
    h = max(anim, key=lambda k: float(np.abs(np.array(anim[k][9:12])).sum()))
if h is None:
    print("no animated vehicle"); sys.exit(1)
f = anim[h]
R = np.array(f[:9]).reshape(3, 3); t = np.array(f[9:12])
fwd = fsign * R[2]                       # vehicle nose (+Z), sign-tunable
fwd = fwd / max(np.linalg.norm(fwd), 1e-6)
worldup = np.array([0.0, wuy, 0.0])
eye = t + worldup * upoff                # up out of the cockpit
back = -fwd
right = np.cross(worldup, back); right /= max(np.linalg.norm(right), 1e-6)
up = np.cross(back, right)
M = np.eye(4)
M[0, :3], M[1, :3], M[2, :3], M[3, :3] = right, up, back, eye
r.cam_matrix = lambda _b, _M=M: _M
r.draw(board)
save_frame(r, out)
print(f"wrote {out} [{backend}]  veh={hex(h)} eye={eye.round(1)} fwd={fwd.round(2)}")