import os
import signal
import time
from contextlib import suppress
from pathlib import Path
from engine import runtime
from engine.extension import Extension
from engine.proc import ran
from engine.sessions import alive
from engine.stored import write_text
from engine.viewer import last, running

STAYS_UP = Extension()
WAIT = 15.0
EVERY = 0.2
ESCALATE = 5.0


def flag(root: Path) -> Path:
    return runtime.folder(root) / "stop"


def at(root: Path) -> float:
    try:
        text = flag(root).read_text().strip()
        return float(text) if text else 0.0
    except (OSError, ValueError):
        return 0.0


def asked(root: Path, since: float = 0.0) -> bool:
    return at(root) > since


def session_flag(root: Path, terminal: str) -> Path:
    return runtime.session_file(Path(root), terminal, "stop")


def ask_session(root: Path, terminal: str) -> None:
    write_text(session_flag(root, terminal), f"{time.time()}\n")


def ask(root: Path) -> None:
    where = flag(root)
    where.parent.mkdir(parents=True, exist_ok=True)
    write_text(where, f"{time.time()}\n")


def clear(root: Path) -> None:
    flag(root).unlink(missing_ok=True)


def gone(root: Path, seconds: float = WAIT) -> bool:
    server = serving(Path(root))
    end = time.monotonic() + seconds
    while time.monotonic() < end:
        if not (alive(server) if server else running(Path(root))):
            return True
        time.sleep(EVERY)
    return False


def ended(root: Path) -> bool:
    if gone(root):
        return True
    for signal_, seconds in ((signal.SIGTERM, ESCALATE), (signal.SIGKILL, ESCALATE)):
        server = serving(Path(root))
        if not server:
            return not running(Path(root))
        with suppress(OSError):
            os.kill(server, signal_)
        if gone(root, seconds):
            return True
    return False


def serving(root: Path) -> int:
    pid = last(root).pid
    listed = ran(["ps", "-o", "command=", "-p", str(pid)]) if pid else None
    command = listed.stdout if listed else ""
    return pid if " serve" in command and any(form in command for form in (str(root), str(root.resolve()))) else 0


def stays_up(record) -> bool:
    """A journal whose server outlives its last agent, such as one on a server of its own."""
    return any(keep(record.root) for keep in STAYS_UP.each(record))