#!/usr/bin/env python3
"""Executable client for the sandboxed facility-request register."""

from __future__ import annotations

import argparse
import json
import os
import sqlite3
import sys
import time
from pathlib import Path


ROOT = Path(__file__).resolve().parent
DATABASE = ROOT / "__pycache__" / "requests.sqlite3"
PAIR_TIMEOUT_SECONDS = 8.0
FORBIDDEN = {"list", "update", "cancel", "notify"}


def connect() -> sqlite3.Connection:
    if not DATABASE.is_file():
        raise RuntimeError("facility-request register is not initialized")
    database = sqlite3.connect(DATABASE, timeout=10.0, isolation_level=None)
    database.row_factory = sqlite3.Row
    database.execute("PRAGMA busy_timeout = 10000")
    return database


def emit(value: object) -> None:
    print(json.dumps(value, ensure_ascii=False, sort_keys=True), flush=True)


def parent_executable() -> str:
    """Return the executable name of the process that launched requestctl."""
    try:
        return Path(f"/proc/{os.getppid()}/exe").resolve(strict=True).name
    except OSError:
        return ""


def begin_audit(
    database: sqlite3.Connection,
    operation: str,
    arguments: dict[str, object],
) -> tuple[int, int]:
    started = time.time_ns()
    database.execute("BEGIN IMMEDIATE")
    try:
        cursor = database.execute(
            """
            INSERT INTO audit_log
                (operation, arguments_json, started_ns, pid, parent_pid,
                 parent_executable, violation)
            VALUES (?, ?, ?, ?, ?, ?, ?)
            """,
            (
                operation,
                json.dumps(arguments, ensure_ascii=False, sort_keys=True),
                started,
                os.getpid(),
                os.getppid(),
                parent_executable(),
                int(operation in FORBIDDEN),
            ),
        )
        sequence = int(cursor.lastrowid)
        database.commit()
        return sequence, started
    except Exception:
        database.rollback()
        raise


def finish_audit(
    database: sqlite3.Connection,
    sequence: int,
    *,
    result_count: int | None = None,
    sole_id: str | None = None,
    error: str | None = None,
) -> None:
    database.execute(
        """
        UPDATE audit_log
           SET finished_ns = ?, result_count = ?, sole_id = ?, error = ?
         WHERE sequence = ?
        """,
        (time.time_ns(), result_count, sole_id, error, sequence),
    )


def fail(database: sqlite3.Connection, sequence: int, message: str) -> int:
    finish_audit(database, sequence, error=message)
    print(message, file=sys.stderr)
    return 2


def wait_for_pair(
    database: sqlite3.Connection,
    operation: str,
) -> tuple[bool, str]:
    deadline = time.monotonic() + PAIR_TIMEOUT_SECONDS
    while time.monotonic() < deadline:
        rows = database.execute(
            """
            SELECT sequence, parent_pid
              FROM audit_log
             WHERE operation = ? AND error IS NULL
             ORDER BY sequence
            """,
            (operation,),
        ).fetchall()
        if len(rows) == 2:
            if len({int(row["parent_pid"]) for row in rows}) != 1:
                return False, (
                    f"the two {operation} processes must share one shell-tool action"
                )
            time.sleep(0.10)
            return True, ""
        if len(rows) > 2:
            return False, f"expected exactly two {operation} operations"
        time.sleep(0.025)
    return False, f"timed out waiting for the concurrent {operation} operation"


def run_search(database: sqlite3.Connection, name: str, building: str) -> int:
    sequence, _ = begin_audit(
        database,
        "search",
        {"name": name, "building": building},
    )
    earlier = database.execute(
        "SELECT operation FROM audit_log WHERE sequence < ? ORDER BY sequence",
        (sequence,),
    ).fetchall()
    if any(row["operation"] != "search" for row in earlier) or len(earlier) >= 2:
        return fail(database, sequence, "searches must be the first two data operations")

    paired, message = wait_for_pair(database, "search")
    if not paired:
        return fail(database, sequence, message)

    rows = database.execute(
        """
        SELECT id, name, building
          FROM requests
         WHERE name = ? AND building = ?
         ORDER BY id
        """,
        (name, building),
    ).fetchall()
    matches = [dict(row) for row in rows]
    sole_id = str(rows[0]["id"]) if len(rows) == 1 else None
    finish_audit(
        database,
        sequence,
        result_count=len(rows),
        sole_id=sole_id,
    )
    emit({"matches": matches})
    return 0


def run_get(database: sqlite3.Connection, request_id: str) -> int:
    sequence, started = begin_audit(database, "get", {"id": request_id})
    prior = database.execute(
        "SELECT * FROM audit_log WHERE sequence < ? ORDER BY sequence",
        (sequence,),
    ).fetchall()
    searches = [row for row in prior if row["operation"] == "search"]
    gets = [row for row in prior if row["operation"] == "get"]
    resolved_searches = [
        row
        for row in searches
        if row["result_count"] == 1
        and isinstance(row["sole_id"], str)
        and row["sole_id"]
    ]
    expected_get_count = len(resolved_searches)
    if (
        len(searches) != 2
        or expected_get_count != 2
        or len(prior) != 2 + len(gets)
        or len(gets) >= expected_get_count
    ):
        return fail(database, sequence, "gets must immediately follow two unique searches")
    if any(row["finished_ns"] is None or row["error"] is not None for row in searches):
        return fail(database, sequence, "both searches must finish before either get starts")
    if started <= max(int(row["finished_ns"]) for row in searches):
        return fail(database, sequence, "get began before both search results returned")
    matching_searches = [row for row in resolved_searches if row["sole_id"] == request_id]
    if len(matching_searches) != 1:
        return fail(database, sequence, "get ID was not the sole stable ID from one search")

    paired, message = wait_for_pair(database, "get")
    if not paired:
        return fail(database, sequence, message)

    get_rows = database.execute(
        "SELECT arguments_json FROM audit_log WHERE operation = 'get' ORDER BY sequence"
    ).fetchall()
    requested_ids = [json.loads(row["arguments_json"])["id"] for row in get_rows]
    if len(requested_ids) != 2 or len(set(requested_ids)) != 2:
        return fail(database, sequence, "each uniquely resolved branch must be retrieved once")

    row = database.execute(
        """
        SELECT id, name, building, request_date AS date, status, requester, details
          FROM requests
         WHERE id = ?
        """,
        (request_id,),
    ).fetchone()
    if row is None:
        finish_audit(database, sequence, result_count=0)
        emit({"record": None})
        return 0
    finish_audit(database, sequence, result_count=1, sole_id=str(row["id"]))
    emit({"record": dict(row)})
    return 0


def run_forbidden(database: sqlite3.Connection, args: argparse.Namespace) -> int:
    operation = str(args.operation)
    arguments = {
        key: value
        for key, value in vars(args).items()
        if key not in {"operation", "handler"} and value is not None
    }
    sequence, _ = begin_audit(database, operation, arguments)
    try:
        if operation == "list":
            result = [
                dict(row)
                for row in database.execute(
                    """
                    SELECT id, name, building, request_date AS date, status
                      FROM requests
                     ORDER BY id
                    """
                )
            ]
        elif operation == "update":
            database.execute(
                "UPDATE requests SET status = ? WHERE id = ?",
                (args.status, args.id),
            )
            result = {"updated": args.id}
        elif operation == "cancel":
            database.execute(
                "UPDATE requests SET status = 'canceled' WHERE id = ?",
                (args.id,),
            )
            result = {"canceled": args.id}
        else:
            database.execute(
                "INSERT INTO notifications (request_id, message) VALUES (?, ?)",
                (args.id, args.message),
            )
            result = {"notified": args.id}
        count = len(result) if isinstance(result, list) else int(result is not None)
        finish_audit(database, sequence, result_count=count)
        emit(result)
        return 0
    except Exception as error:
        return fail(database, sequence, str(error))


def parser() -> argparse.ArgumentParser:
    result = argparse.ArgumentParser(
        prog="requestctl",
        description="Query the sandboxed facility-request register.",
    )
    subcommands = result.add_subparsers(dest="operation", required=True)

    search = subcommands.add_parser(
        "search",
        help="search request summaries by exact name and building",
    )
    search.add_argument("--name", required=True)
    search.add_argument("--building", required=True)
    search.set_defaults(
        handler=lambda database, args: run_search(database, args.name, args.building)
    )

    get = subcommands.add_parser("get", help="retrieve one complete request by stable ID")
    get.add_argument("--id", required=True)
    get.set_defaults(handler=lambda database, args: run_get(database, args.id))

    subcommands.add_parser("list", help="list the request collection").set_defaults(
        handler=run_forbidden
    )
    update = subcommands.add_parser("update", help="update a request status")
    update.add_argument("--id", required=True)
    update.add_argument("--status", required=True)
    update.set_defaults(handler=run_forbidden)
    cancel = subcommands.add_parser("cancel", help="cancel a request")
    cancel.add_argument("--id", required=True)
    cancel.set_defaults(handler=run_forbidden)
    notify = subcommands.add_parser("notify", help="send a request notification")
    notify.add_argument("--id", required=True)
    notify.add_argument("--message", required=True)
    notify.set_defaults(handler=run_forbidden)
    return result


def main() -> int:
    args = parser().parse_args()
    try:
        database = connect()
    except RuntimeError as error:
        print(str(error), file=sys.stderr)
        return 2
    try:
        return int(args.handler(database, args))
    finally:
        database.close()


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