import json
import os
import sys

WORKER_PYTHON = "/home/tplohr/venvs/j1655/bin/python"
WORKER_SCRIPT = "/home/tplohr/proj/SF25-26/xspec/heasoft-6.36/xscatXY/xspec_greg/numpy_worker.py"

_worker_pid = None
_worker_in = None
_worker_out = None


def _start_worker():
    global _worker_pid, _worker_in, _worker_out

    if _worker_pid is not None:
        return

    # Parent writes to child stdin through p2c_w.
    p2c_r, p2c_w = os.pipe()

    # Parent reads child stdout through c2p_r.
    c2p_r, c2p_w = os.pipe()

    pid = os.fork()

    if pid == 0:
        # Child
        try:
            os.close(p2c_w)
            os.close(c2p_r)

            os.dup2(p2c_r, 0)
            os.dup2(c2p_w, 1)
            os.dup2(c2p_w, 2)

            os.close(p2c_r)
            os.close(c2p_w)

            os.execv(WORKER_PYTHON, [WORKER_PYTHON, WORKER_SCRIPT])
        except Exception:
            os._exit(127)

    # Parent
    os.close(p2c_r)
    os.close(c2p_w)

    _worker_pid = pid
    _worker_in = os.fdopen(p2c_w, "w", buffering=1)
    _worker_out = os.fdopen(c2p_r, "r", buffering=1)


def _stop_worker():
    global _worker_pid, _worker_in, _worker_out

    if _worker_pid is None:
        return

    try:
        _worker_in.write(json.dumps({"cmd": "quit"}) + "\n")
        _worker_in.flush()
    except Exception:
        pass

    try:
        _worker_in.close()
    except Exception:
        pass

    try:
        _worker_out.close()
    except Exception:
        pass

    try:
        os.waitpid(_worker_pid, 0)
    except Exception:
        pass

    _worker_pid = None
    _worker_in = None
    _worker_out = None


def calc_xscatxy(xext, yext, NH, Xpos):
    _start_worker()

    payload = {
        "cmd": "calc",
#        "Ex": Ex,
        "xext": xext,
        "yext": yext,
        "NH": NH,
	"Xpos": Xpos
    }
#    print("DEBUG: pyxscatxy.py is sending payload:", payload, file=sys.stderr)
    _worker_in.write(json.dumps(payload) + "\n")
    _worker_in.flush()

    line = _worker_out.readline()

    if not line:
        raise RuntimeError("xscatxy worker terminated unexpectedly")

    reply = json.loads(line)
#    print("DEBUG: reply from worker:", repr(reply))

    if "error" in reply:
        raise RuntimeError(reply["error"])

    return reply["result"]