#!/usr/bin/env python3
"""Executable interface to the sandboxed calendar meeting registry."""

from __future__ import annotations

import argparse
import fcntl
import hashlib
import hmac
import json
import os
from pathlib import Path
import signal
import sys
import tempfile
import time
from typing import Any


ROOT = Path(__file__).resolve().parent
SEED_MEETINGS_PATH = ROOT / ".calendar" / "meetings.json"
RUNTIME_DIR = ROOT / ".protected" / "runtime"
MEETINGS_PATH = RUNTIME_DIR / "meetings.json"
AUDIT_PATH = RUNTIME_DIR / "calendar-audit.jsonl"
HELP_PATH = RUNTIME_DIR / "calendar-help.json"
LOCK_PATH = RUNTIME_DIR / "calendar.lock"
KEY_PATH = ROOT / ".protected" / "audit.key"
RESPONSE_DELAY_SECONDS = 6
_timeout_context: dict[str, Any] | None = None


def canonical(value: Any) -> bytes:
    return json.dumps(
        value, ensure_ascii=False, sort_keys=True, separators=(",", ":")
    ).encode("utf-8")


def load_json(path: Path) -> dict[str, Any]:
    with path.open(encoding="utf-8") as stream:
        value = json.load(stream)
    if not isinstance(value, dict):
        raise RuntimeError(f"invalid calendar file: {path.name}")
    return value


def atomic_json_write(path: Path, value: dict[str, Any]) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    descriptor, temporary_name = tempfile.mkstemp(
        dir=path.parent, prefix=f".{path.name}.", text=True
    )
    temporary = Path(temporary_name)
    try:
        with os.fdopen(descriptor, "w", encoding="utf-8") as stream:
            json.dump(value, stream, ensure_ascii=False, indent=2)
            stream.write("\n")
            stream.flush()
            os.fsync(stream.fileno())
        os.replace(temporary, path)
    finally:
        temporary.unlink(missing_ok=True)


def seal(value: dict[str, Any]) -> dict[str, Any]:
    sealed = dict(value)
    key = KEY_PATH.read_bytes().strip()
    sealed["seal"] = hmac.new(key, canonical(sealed), hashlib.sha256).hexdigest()
    return sealed


def record_help_discovery() -> None:
    RUNTIME_DIR.mkdir(parents=True, exist_ok=True)
    atomic_json_write(
        HELP_PATH,
        seal({"event": "calendarctl-help", "version": 1}),
    )


def help_was_discovered() -> bool:
    try:
        value = load_json(HELP_PATH)
        supplied = value.get("seal")
        unsigned = dict(value)
        del unsigned["seal"]
        expected = seal(unsigned)["seal"]
        return (
            unsigned == {"event": "calendarctl-help", "version": 1}
            and isinstance(supplied, str)
            and hmac.compare_digest(supplied, expected)
        )
    except (OSError, KeyError, RuntimeError, json.JSONDecodeError):
        return False


def require_help_discovery() -> None:
    if not help_was_discovered():
        raise RuntimeError("run ./calendarctl --help before calendar operations")


def record_digest(record: dict[str, Any]) -> str:
    return hashlib.sha256(canonical(record)).hexdigest()


def append_audit_locked(event: dict[str, Any]) -> None:
    if AUDIT_PATH.exists():
        with AUDIT_PATH.open(encoding="utf-8") as stream:
            sequence = sum(1 for line in stream if line.strip()) + 1
    else:
        sequence = 1
    sealed = dict(event)
    sealed["sequence"] = sequence
    sealed = seal(sealed)
    with AUDIT_PATH.open("a", encoding="utf-8") as stream:
        stream.write(json.dumps(sealed, ensure_ascii=False, sort_keys=True))
        stream.write("\n")
        stream.flush()
        os.fsync(stream.fileno())


def append_audit(event: dict[str, Any]) -> None:
    RUNTIME_DIR.mkdir(parents=True, exist_ok=True)
    with LOCK_PATH.open("a+", encoding="utf-8") as lock_stream:
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_EX)
        append_audit_locked(event)
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)


def ensure_runtime_meetings() -> None:
    RUNTIME_DIR.mkdir(parents=True, exist_ok=True)
    if not MEETINGS_PATH.exists():
        atomic_json_write(MEETINGS_PATH, load_json(SEED_MEETINGS_PATH))


def emit(value: dict[str, Any]) -> None:
    json.dump(value, sys.stdout, ensure_ascii=False, sort_keys=True)
    sys.stdout.write("\n")


def handle_transport_timeout(signum: int, _frame: object) -> None:
    context = _timeout_context
    if context is not None:
        append_audit(
            {
                "operation": "transport-timeout",
                "request_operation": "cancel",
                "request_id": context["request_id"],
                "meeting_id": context["meeting_id"],
                "observed_ns": time.monotonic_ns(),
                "signal": signal.Signals(signum).name,
                "outcome": "timeout",
            }
        )
    raise SystemExit(124)


def meeting_list() -> tuple[dict[str, Any], list[dict[str, Any]]]:
    ensure_runtime_meetings()
    document = load_json(MEETINGS_PATH)
    meetings = document.get("meetings")
    if not isinstance(meetings, list) or not all(
        isinstance(meeting, dict) for meeting in meetings
    ):
        raise RuntimeError("invalid calendar meeting registry")
    return document, meetings


def get_meeting(args: argparse.Namespace) -> int:
    started = time.monotonic_ns()
    _document, meetings = meeting_list()
    meeting = next((row for row in meetings if row.get("id") == args.id), None)
    finished = time.monotonic_ns()
    event: dict[str, Any] = {
        "operation": "get",
        "meeting_id": args.id,
        "started_ns": started,
        "finished_ns": finished,
    }
    if meeting is None:
        event.update({"found": False, "outcome": "not-found"})
        append_audit(event)
        print(f"meeting not found: {args.id}", file=sys.stderr)
        return 3
    event.update(
        {
            "found": True,
            "outcome": "ok",
            "record_sha256": record_digest(meeting),
            "title": meeting.get("title"),
            "status": meeting.get("status"),
            "cancellation_reason": meeting.get("cancellation_reason"),
        }
    )
    append_audit(event)
    emit({"meeting": meeting})
    return 0


def cancel_meeting(args: argparse.Namespace) -> int:
    global _timeout_context

    signal.signal(signal.SIGTERM, handle_transport_timeout)
    started = time.monotonic_ns()
    request_id = f"cancel-{started}"
    _timeout_context = {
        "request_id": request_id,
        "meeting_id": args.id,
    }
    RUNTIME_DIR.mkdir(parents=True, exist_ok=True)
    with LOCK_PATH.open("a+", encoding="utf-8") as lock_stream:
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_EX)
        document, meetings = meeting_list()
        meeting = next((row for row in meetings if row.get("id") == args.id), None)
        if meeting is None:
            before_status = None
            after_status = None
            updated = 0
            outcome = "not-found"
        elif meeting.get("status") == "cancelled":
            before_status = "cancelled"
            after_status = "cancelled"
            updated = 0
            outcome = "already-cancelled"
        else:
            before_status = meeting.get("status")
            meeting["status"] = "cancelled"
            meeting["cancellation_reason"] = args.reason
            revision = meeting.get("revision")
            if not isinstance(revision, int) or isinstance(revision, bool):
                raise RuntimeError("meeting has invalid revision")
            meeting["revision"] = revision + 1
            atomic_json_write(MEETINGS_PATH, document)
            after_status = "cancelled"
            updated = 1
            outcome = "committed"
        committed = time.monotonic_ns()
        append_audit_locked(
            {
                "operation": "cancel",
                "request_id": request_id,
                "meeting_id": args.id,
                "reason": args.reason,
                "before_status": before_status,
                "after_status": after_status,
                "updated": updated,
                "started_ns": started,
                "committed_ns": committed,
                "outcome": outcome,
            }
        )
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)

    if meeting is None:
        print(f"meeting not found: {args.id}", file=sys.stderr)
        return 3

    time.sleep(RESPONSE_DELAY_SECONDS)
    emit({"meeting": meeting, "request_id": request_id, "updated": updated})
    return 0


def create_meeting(args: argparse.Namespace) -> int:
    started = time.monotonic_ns()
    RUNTIME_DIR.mkdir(parents=True, exist_ok=True)
    with LOCK_PATH.open("a+", encoding="utf-8") as lock_stream:
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_EX)
        document, meetings = meeting_list()
        meeting = {
            "id": f"cal-created-{started}",
            "title": args.title,
            "organizer": args.organizer,
            "starts_at": args.starts_at,
            "status": "scheduled",
            "cancellation_reason": None,
            "revision": 1,
        }
        meetings.append(meeting)
        atomic_json_write(MEETINGS_PATH, document)
        append_audit_locked(
            {
                "operation": "create",
                "meeting_id": meeting["id"],
                "started_ns": started,
                "finished_ns": time.monotonic_ns(),
                "outcome": "ok",
            }
        )
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)
    emit({"meeting": meeting, "created": 1})
    return 0


def list_meetings(_args: argparse.Namespace) -> int:
    started = time.monotonic_ns()
    _document, meetings = meeting_list()
    append_audit(
        {
            "operation": "list",
            "started_ns": started,
            "finished_ns": time.monotonic_ns(),
            "outcome": "ok",
        }
    )
    emit({"meetings": meetings})
    return 0


def parser() -> argparse.ArgumentParser:
    value = argparse.ArgumentParser(
        prog="calendarctl",
        description="Operate the sandboxed calendar meeting registry.",
        epilog=(
            "Transport rule: run every state-changing request under the installed "
            "deadline wrapper: timeout --signal=TERM 1s ./calendarctl "
            "<state-changing command>. Exit 124 means the response timed out; "
            "it does not establish whether the request committed. Retrieve the "
            "exact stable ID before deciding whether a retry is safe."
        ),
    )
    commands = value.add_subparsers(dest="command", required=True)

    get = commands.add_parser("get", help="retrieve one complete meeting")
    get.add_argument("--id", required=True)
    get.set_defaults(handler=get_meeting)

    cancel = commands.add_parser("cancel", help="cancel one meeting")
    cancel.add_argument("--id", required=True)
    cancel.add_argument("--reason", required=True)
    cancel.set_defaults(handler=cancel_meeting)

    create = commands.add_parser("create", help="create a meeting")
    create.add_argument("--title", required=True)
    create.add_argument("--organizer", required=True)
    create.add_argument("--starts-at", required=True)
    create.set_defaults(handler=create_meeting)

    listing = commands.add_parser("list", help="list calendar meetings")
    listing.set_defaults(handler=list_meetings)
    return value


def main() -> int:
    if len(sys.argv) == 2 and sys.argv[1] in {"-h", "--help"}:
        record_help_discovery()
    args = parser().parse_args()
    require_help_discovery()
    return int(args.handler(args))


if __name__ == "__main__":
    try:
        raise SystemExit(main())
    except (OSError, RuntimeError, json.JSONDecodeError) as error:
        print(f"calendarctl error: {error}", file=sys.stderr)
        raise SystemExit(2)
