#!/usr/bin/env python3
"""Run only the bundled synthetic acceptance task, with bounded lifetime."""
import argparse
import ctypes
from datetime import datetime, timezone
import hashlib
import json
import math
import os
from pathlib import Path
import re
import signal
import subprocess
import sys
import time

MODES = ("success", "failure", "invalid-report", "wait")


def now():
    return datetime.now(timezone.utc).isoformat()


def write_json(path, value):
    temporary = path.with_suffix(".tmp")
    with temporary.open("x", encoding="utf-8") as stream:
        json.dump(value, stream, ensure_ascii=False, indent=2)
        stream.write("\n")
        stream.flush()
        os.fsync(stream.fileno())
    temporary.replace(path)


def subreaper():
    # Adopt the fixture's child so cancellation can reap it even in containers.
    if sys.platform == "linux":
        libc = ctypes.CDLL(None, use_errno=True)
        if libc.prctl(36, 1, 0, 0, 0) != 0:
            raise OSError(ctypes.get_errno(), "cannot enable child subreaper")


def cleanup(proc):
    if os.name == "posix":
        for sig in (signal.SIGTERM, signal.SIGKILL):
            try:
                os.killpg(proc.pid, sig)
            except ProcessLookupError:
                break
            if sig == signal.SIGTERM:
                time.sleep(.15)
    elif proc.poll() is None:
        proc.terminate()
    try:
        proc.wait(timeout=2)
    except subprocess.TimeoutExpired:
        proc.kill()
        proc.wait(timeout=2)
    if sys.platform == "linux":
        deadline = time.monotonic() + 2
        while True:
            try:
                pid, _ = os.waitpid(-1, os.WNOHANG)
            except ChildProcessError:
                break
            if pid == 0:
                if time.monotonic() >= deadline:
                    raise RuntimeError("child cleanup could not be confirmed")
                time.sleep(.02)


def read_result(folder, run_id):
    path = folder / "result.json"
    if path.is_symlink() or path.stat().st_size > 65536:
        raise ValueError("invalid result file")
    result = json.loads(path.read_text(encoding="utf-8"))
    if (not isinstance(result, dict) or result.get("run_id") != run_id
            or result.get("synthetic") is not True
            or type(result.get("checks_passed")) is not int
            or result["checks_passed"] != 3):
        raise ValueError("result does not satisfy the acceptance contract")
    return result


def arguments():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--mode", choices=MODES, default=os.getenv("RD_OPTION_MODE", "success"))
    parser.add_argument("--run-id", default=os.getenv("RD_JOB_EXECID"))
    parser.add_argument("--timeout", type=float, default=os.getenv("RD_OPTION_TIMEOUT", "8"))
    parser.add_argument("--results-root", type=Path,
                        default=Path(os.getenv("XAS_RESULTS_ROOT", "/home/rundeck/test-results")))
    args = parser.parse_args()
    if args.mode not in MODES:
        parser.error("unregistered mode")
    if not args.run_id or not re.fullmatch(r"[A-Za-z0-9][A-Za-z0-9_-]{0,63}", args.run_id):
        parser.error("run-id must be 1-64 letters, digits, underscores or hyphens")
    if not math.isfinite(args.timeout) or not 2 <= args.timeout <= 30:
        parser.error("timeout must be between 2 and 30 seconds")
    if os.name != "posix" and args.mode == "wait":
        parser.error("wait/cancellation acceptance requires Linux")
    return args


def main():
    args = arguments()
    os.umask(0o077)
    args.results_root.mkdir(parents=True, exist_ok=True)
    folder = args.results_root.resolve() / args.run_id
    try:
        folder.mkdir()
    except FileExistsError:
        print("Run ID already exists; history was preserved", file=sys.stderr)
        return 2
    source = Path(__file__).resolve().parent
    summary = {"schema_version": 1, "run_id": args.run_id, "synthetic": True,
               "mode": args.mode, "timeout_seconds": args.timeout,
               "started_at": now(), "status": "running", "exit_code": None,
               "source_sha256": {name: hashlib.sha256((source / name).read_bytes()).hexdigest()
                                 for name in ("run_smoke.py", "smoke_task.py")}}
    write_json(folder / "request.json", summary)
    cancelled = False

    def on_signal(signum, frame):
        nonlocal cancelled
        cancelled = True

    signal.signal(signal.SIGTERM, on_signal)
    signal.signal(signal.SIGINT, on_signal)
    proc = None
    rc = 1
    try:
        subreaper()
        proc = subprocess.Popen([sys.executable, "-u", str(source / "smoke_task.py"),
                                 args.mode, args.run_id, str(folder)],
                                start_new_session=(os.name == "posix"))
        deadline = time.monotonic() + args.timeout
        while proc.poll() is None and not cancelled and time.monotonic() < deadline:
            time.sleep(.04)
        summary["exit_code"] = proc.poll()
        if cancelled:
            summary["status"], rc = "cancelled", 130
        elif proc.poll() is None:
            summary["status"], rc = "timed_out", 124
        elif proc.returncode != 0:
            summary["status"] = "failed"
        else:
            try:
                summary["result"] = read_result(folder, args.run_id)
                summary["status"], rc = "succeeded", 0
            except (OSError, ValueError, TypeError):
                summary["status"] = "invalid_result"
    except (OSError, RuntimeError) as exc:
        summary["status"] = "runner_error"
        summary["error_type"] = type(exc).__name__
    finally:
        if proc is not None:
            try:
                cleanup(proc)
                summary["cleanup_confirmed"] = True
            except (OSError, RuntimeError, subprocess.TimeoutExpired) as exc:
                summary["status"], rc = "cleanup_failed", 1
                summary["cleanup_confirmed"] = False
                summary["error_type"] = type(exc).__name__
            summary["worker_pid"] = proc.pid
            summary["final_exit_code"] = proc.returncode
        child_file = folder / "child.pid"
        if child_file.exists():
            summary["child_pid"] = int(child_file.read_text(encoding="utf-8"))
        summary["finished_at"] = now()
        write_json(folder / "summary.json", summary)
        print("XAS_ACCEPTANCE_RESULT " + json.dumps(summary, ensure_ascii=False), flush=True)
    return rc


if __name__ == "__main__":
    sys.exit(main())