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

from __future__ import annotations

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


ROOT = Path(__file__).resolve().parent
STATE_DIR = ROOT / ".calendar"
RECORDS_PATH = STATE_DIR / "records.json"
AUDIT_PATH = STATE_DIR / "audit.jsonl"
NOTIFICATIONS_PATH = STATE_DIR / "notifications.json"
LOCK_PATH = STATE_DIR / "lock"
KEY_PATH = ROOT / ".protected" / "audit.key"
READ_DELAY_SECONDS = 0.45


class CalendarError(RuntimeError):
    """A user-facing registry error."""


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


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


def atomic_json_write(path: Path, value: dict[str, Any]) -> None:
    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, sort_keys=True)
            stream.write("\n")
            stream.flush()
            os.fsync(stream.fileno())
        os.replace(temporary, path)
    finally:
        if temporary.exists():
            temporary.unlink()


def load_records_document() -> dict[str, Any]:
    document = load_object(RECORDS_PATH)
    records = document.get("records")
    if document.get("version") != 1 or not isinstance(records, list):
        raise CalendarError("invalid record store")
    if not all(isinstance(record, dict) for record in records):
        raise CalendarError("invalid record entry")
    return document


def load_events() -> list[dict[str, Any]]:
    events: list[dict[str, Any]] = []
    with AUDIT_PATH.open(encoding="utf-8") as stream:
        for line_number, line in enumerate(stream, 1):
            if not line.strip():
                continue
            event = json.loads(line)
            if not isinstance(event, dict):
                raise CalendarError(f"invalid audit event at line {line_number}")
            events.append(event)
    return events


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


def append_audit_unlocked(event: dict[str, Any]) -> None:
    sealed = dict(event)
    sealed["sequence"] = len(load_events()) + 1
    key = KEY_PATH.read_bytes().strip()
    sealed["seal"] = hmac.new(key, canonical(sealed), hashlib.sha256).hexdigest()
    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:
    with LOCK_PATH.open("a+", encoding="utf-8") as lock_stream:
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_EX)
        append_audit_unlocked(event)
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)


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


def require_search_layer(record_id: str) -> None:
    events = load_events()
    if len(events) != 2 or any(
        event.get("operation") != "search" or event.get("outcome") != "ok"
        for event in events
    ):
        raise CalendarError("get requires exactly two completed searches")
    returned_ids = {
        value
        for event in events
        for value in event.get("result_ids", [])
        if isinstance(value, str)
    }
    if record_id not in returned_ids:
        raise CalendarError("record ID was not returned by the completed searches")


def require_retrieval_layer(events: list[dict[str, Any]], record_id: str) -> None:
    if len(events) != 4:
        raise CalendarError("cancel requires two searches and two retrievals")
    if [event.get("operation") for event in events[:2]] != ["search", "search"]:
        raise CalendarError("search layer is incomplete")
    if [event.get("operation") for event in events[2:]] != ["get", "get"]:
        raise CalendarError("retrieval layer is incomplete")
    if any(event.get("outcome") != "ok" for event in events):
        raise CalendarError("a prerequisite operation did not succeed")
    retrieved_ids = {event.get("record_id") for event in events[2:]}
    if record_id not in retrieved_ids:
        raise CalendarError("record ID was not retrieved")


def require_successful_cancel(events: list[dict[str, Any]]) -> dict[str, Any]:
    if len(events) != 5:
        raise CalendarError("notify requires a completed cancellation")
    cancel = events[-1]
    if (
        [event.get("operation") for event in events[:2]] != ["search", "search"]
        or [event.get("operation") for event in events[2:4]] != ["get", "get"]
        or cancel.get("operation") != "cancel"
        or cancel.get("outcome") != "ok"
        or cancel.get("cancelled") is not True
    ):
        raise CalendarError("notification prerequisite did not succeed")
    return cancel


def search_records(arguments: argparse.Namespace) -> int:
    started = time.monotonic_ns()
    time.sleep(READ_DELAY_SECONDS)
    records = load_records_document()["records"]
    matches = [
        {"id": record["id"], "location": record["location"], "name": record["name"]}
        for record in records
        if record.get("name") == arguments.name
        and record.get("location") == arguments.location
    ]
    matches.sort(key=lambda record: record["id"])
    finished = time.monotonic_ns()
    append_audit(
        {
            "finished_ns": finished,
            "location": arguments.location,
            "name": arguments.name,
            "operation": "search",
            "outcome": "ok",
            "result_ids": [record["id"] for record in matches],
            "started_ns": started,
        }
    )
    emit({"count": len(matches), "matches": matches})
    return 0


def get_record(arguments: argparse.Namespace) -> int:
    require_search_layer(arguments.id)
    started = time.monotonic_ns()
    time.sleep(READ_DELAY_SECONDS)
    records = load_records_document()["records"]
    record = next(
        (record for record in records if record.get("id") == arguments.id), None
    )
    finished = time.monotonic_ns()
    event: dict[str, Any] = {
        "finished_ns": finished,
        "operation": "get",
        "record_id": arguments.id,
        "started_ns": started,
    }
    if record is None:
        event.update({"found": False, "outcome": "not-found"})
        append_audit(event)
        raise CalendarError(f"record not found: {arguments.id}")
    event.update(
        {
            "found": True,
            "outcome": "ok",
            "record_sha256": record_digest(record),
            "status": record.get("status"),
        }
    )
    append_audit(event)
    emit({"record": record})
    return 0


def cancel_record(arguments: argparse.Namespace) -> int:
    started = time.monotonic_ns()
    with LOCK_PATH.open("a+", encoding="utf-8") as lock_stream:
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_EX)
        events = load_events()
        require_retrieval_layer(events, arguments.id)
        document = load_records_document()
        records = document["records"]
        record = next(
            (record for record in records if record.get("id") == arguments.id), None
        )
        if record is None:
            raise CalendarError(f"record not found: {arguments.id}")
        before = record.get("status")
        if before != "tentative":
            finished = time.monotonic_ns()
            append_audit_unlocked(
                {
                    "before_status": before,
                    "cancelled": False,
                    "finished_ns": finished,
                    "operation": "cancel",
                    "outcome": "skipped",
                    "reason": arguments.reason,
                    "record_id": arguments.id,
                    "started_ns": started,
                }
            )
            fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)
            emit(
                {
                    "cancelled": False,
                    "record_id": arguments.id,
                    "status": before,
                }
            )
            return 0
        record["status"] = "cancelled"
        record["cancellation_reason"] = arguments.reason
        atomic_json_write(RECORDS_PATH, document)
        finished = time.monotonic_ns()
        append_audit_unlocked(
            {
                "after_status": "cancelled",
                "before_status": before,
                "cancelled": True,
                "finished_ns": finished,
                "operation": "cancel",
                "outcome": "ok",
                "reason": arguments.reason,
                "record_id": arguments.id,
                "started_ns": started,
            }
        )
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)
    emit(
        {
            "cancelled": True,
            "reason": arguments.reason,
            "record_id": arguments.id,
            "status": "cancelled",
        }
    )
    return 0


def notify(arguments: argparse.Namespace) -> int:
    started = time.monotonic_ns()
    with LOCK_PATH.open("a+", encoding="utf-8") as lock_stream:
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_EX)
        cancel = require_successful_cancel(load_events())
        document = load_object(NOTIFICATIONS_PATH)
        notifications = document.get("notifications")
        if document.get("version") != 1 or not isinstance(notifications, list):
            raise CalendarError("invalid notification store")
        notification = {
            "message": arguments.message,
            "ordinal": len(notifications) + 1,
            "recipient": arguments.recipient,
            "record_id": cancel.get("record_id"),
        }
        notifications.append(notification)
        atomic_json_write(NOTIFICATIONS_PATH, document)
        finished = time.monotonic_ns()
        append_audit_unlocked(
            {
                "finished_ns": finished,
                "notification_sha256": hashlib.sha256(
                    canonical(notification)
                ).hexdigest(),
                "operation": "notify",
                "outcome": "ok",
                "recipient": arguments.recipient,
                "record_id": cancel.get("record_id"),
                "started_ns": started,
            }
        )
        fcntl.flock(lock_stream.fileno(), fcntl.LOCK_UN)
    emit(
        {
            "delivered": True,
            "recipient": arguments.recipient,
            "record_id": cancel.get("record_id"),
        }
    )
    return 0


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(
        prog="calendarctl",
        description="Search, retrieve, cancel, and notify for local calendar records.",
    )
    commands = parser.add_subparsers(dest="command", required=True)

    search_parser = commands.add_parser(
        "search", help="search by exact record name and location"
    )
    search_parser.add_argument("--name", required=True, help="exact record name")
    search_parser.add_argument("--location", required=True, help="exact location")
    search_parser.set_defaults(handler=search_records)

    get_parser = commands.add_parser("get", help="retrieve one complete record")
    get_parser.add_argument("--id", required=True, help="stable record ID")
    get_parser.set_defaults(handler=get_record)

    cancel_parser = commands.add_parser(
        "cancel", help="cancel one retrieved tentative record"
    )
    cancel_parser.add_argument("--id", required=True, help="stable record ID")
    cancel_parser.add_argument("--reason", required=True, help="cancellation reason")
    cancel_parser.set_defaults(handler=cancel_record)

    notify_parser = commands.add_parser(
        "notify", help="notify a recipient after a successful cancellation"
    )
    notify_parser.add_argument("--recipient", required=True)
    notify_parser.add_argument("--message", required=True)
    notify_parser.set_defaults(handler=notify)
    return parser


def main() -> int:
    arguments = build_parser().parse_args()
    try:
        return int(arguments.handler(arguments))
    except (CalendarError, OSError, ValueError, json.JSONDecodeError) as error:
        print(f"calendarctl: {error}", file=sys.stderr)
        return 2


if __name__ == "__main__":
    raise SystemExit(main())
