from datetime import datetime, timedelta
from typing import Any

from app.db.database import get_connection
from app.db.migrations import run_migrations

# Plánovač (monitor) spouští pouze záznamy s `next_run_at IS NOT NULL`
# (a zároveň `next_run_at <= CURRENT_TIMESTAMP`).
# Portál proto MUSÍ `next_run_at` naplnit při create/update/enable, jinak se
# zapnutý skript nikdy nespustí. Monitor si po každém běhu sám dopočítá další
# `next_run_at` – Portál pouze připravuje data, scheduler zůstává v monitoru.
#
# Časy v DB jsou ukládané přes SQLite CURRENT_TIMESTAMP, tj. v UTC ve formátu
# "YYYY-MM-DD HH:MM:SS". `next_run_at` musíme počítat ve stejném formátu a
# časové zóně, aby porovnání v monitoru sedělo.
_TIMESTAMP_FORMAT = "%Y-%m-%d %H:%M:%S"


def _parse_schedule_time(schedule_time: str | None) -> tuple[int, int]:
    """Rozparsuje "HH:MM" na (hodina, minuta) nebo vyhodí ValueError."""
    value = (schedule_time or "").strip()
    if not value:
        raise ValueError("Čas spuštění (schedule_time) je povinný pro tuto frekvenci")
    parts = value.split(":")
    if len(parts) != 2:
        raise ValueError(f"Neplatný formát času: {value!r} (očekává se HH:MM)")
    try:
        hour = int(parts[0])
        minute = int(parts[1])
    except ValueError:
        raise ValueError(f"Neplatný formát času: {value!r} (očekává se HH:MM)")
    if not (0 <= hour <= 23 and 0 <= minute <= 59):
        raise ValueError(f"Neplatný čas: {value!r} (hodina 0-23, minuta 0-59)")
    return hour, minute


def _add_one_month(dt: datetime) -> datetime:
    """Posune datum o jeden měsíc dopředu, ošetří kratší měsíce."""
    month = dt.month + 1
    year = dt.year + (month - 1) // 12
    month = (month - 1) % 12 + 1
    # Ošetření např. 31. -> kratší měsíc; den ořízneme na poslední platný.
    day = dt.day
    while True:
        try:
            return dt.replace(year=year, month=month, day=day)
        except ValueError:
            day -= 1
            if day < 1:
                raise


def compute_next_run_at(
    schedule_type: str | None,
    schedule_time: str | None,
    *,
    now: datetime | None = None,
) -> str:
    """Spočítá `next_run_at` stejně jako monitor.

    Vrací řetězec ve formátu "YYYY-MM-DD HH:MM:SS" v UTC.
    Vyhodí ValueError, pokud čas nelze spočítat (neplatná frekvence/čas).
    """
    now = (now or datetime.utcnow()).replace(microsecond=0)

    if schedule_type == "hourly":
        # Další celá hodina.
        nxt = now.replace(minute=0, second=0) + timedelta(hours=1)
        return nxt.strftime(_TIMESTAMP_FORMAT)

    hour, minute = _parse_schedule_time(schedule_time)
    candidate = now.replace(hour=hour, minute=minute, second=0)

    if schedule_type == "daily":
        if candidate <= now:
            candidate += timedelta(days=1)
    elif schedule_type == "weekly":
        if candidate <= now:
            candidate += timedelta(days=7)
    elif schedule_type == "monthly":
        if candidate <= now:
            candidate = _add_one_month(candidate)
    else:
        raise ValueError(f"Neznámá frekvence: {schedule_type!r}")

    return candidate.strftime(_TIMESTAMP_FORMAT)


def resolve_next_run_at(metadata: dict[str, Any]) -> str | None:
    """Vrátí `next_run_at` pro zadaná metadata.

    - vypnutý skript (`is_enabled = 0`) => None
    - zapnutý skript => spočítaný čas (může vyhodit ValueError)
    """
    if not metadata.get("is_enabled"):
        return None
    return compute_next_run_at(metadata.get("schedule_type"), metadata.get("schedule_time"))


def get_scheduled_scripts():
    run_migrations()
    con = get_connection()

    rows = con.execute(
        """
        SELECT
            id,
            name,
            description,
            script_name,
            schedule_type,
            schedule_time,
            timeout_seconds,
            COALESCE(is_enabled, 1) AS is_enabled,
            COALESCE(is_running, 0) AS is_running,
            last_run_at,
            last_status,
            last_job_id,
            last_error_text,
            next_run_at,
            created_at,
            updated_at
        FROM scheduled_scripts
        ORDER BY name
        """
    ).fetchall()

    con.close()
    return [dict(row) for row in rows]


def get_scheduled_script(script_id: int):
    run_migrations()
    con = get_connection()

    row = con.execute(
        """
        SELECT
            id,
            name,
            description,
            script_name,
            schedule_type,
            schedule_time,
            timeout_seconds,
            COALESCE(is_enabled, 1) AS is_enabled,
            COALESCE(is_running, 0) AS is_running,
            last_run_at,
            last_status,
            last_job_id,
            last_error_text,
            next_run_at,
            created_at,
            updated_at
        FROM scheduled_scripts
        WHERE id = ?
        """,
        (script_id,),
    ).fetchone()

    con.close()
    return dict(row) if row else None


def create_scheduled_script(metadata: dict[str, Any]) -> int:
    run_migrations()
    con = get_connection()

    # Zapnutý skript musí dostat `next_run_at`, jinak ho monitor nikdy nespustí.
    next_run_at = resolve_next_run_at(metadata)

    cur = con.execute(
        """
        INSERT INTO scheduled_scripts (
            name,
            description,
            script_name,
            schedule_type,
            schedule_time,
            timeout_seconds,
            is_enabled,
            is_running,
            next_run_at,
            created_at,
            updated_at
        )
        VALUES (?, ?, ?, ?, ?, ?, ?, 0, ?, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)
        """,
        (
            metadata.get("name"),
            metadata.get("description") or None,
            metadata.get("script_name"),
            metadata.get("schedule_type"),
            metadata.get("schedule_time") or None,
            metadata.get("timeout_seconds"),
            1 if metadata.get("is_enabled") else 0,
            next_run_at,
        ),
    )
    script_id = cur.lastrowid
    con.commit()
    con.close()
    return script_id


def update_scheduled_script(script_id: int, metadata: dict[str, Any]) -> None:
    run_migrations()
    con = get_connection()

    # Při editaci vždy přepočítáme `next_run_at` podle (případně změněné)
    # frekvence/času. Vypnutý skript dostane NULL, zapnutý nový čas.
    next_run_at = resolve_next_run_at(metadata)

    con.execute(
        """
        UPDATE scheduled_scripts
        SET name = ?,
            description = ?,
            schedule_type = ?,
            schedule_time = ?,
            timeout_seconds = ?,
            is_enabled = ?,
            next_run_at = ?,
            updated_at = CURRENT_TIMESTAMP
        WHERE id = ?
        """,
        (
            metadata.get("name"),
            metadata.get("description") or None,
            metadata.get("schedule_type"),
            metadata.get("schedule_time") or None,
            metadata.get("timeout_seconds"),
            1 if metadata.get("is_enabled") else 0,
            next_run_at,
            script_id,
        ),
    )

    con.commit()
    con.close()


def set_scheduled_script_enabled(
    script_id: int, is_enabled: bool, next_run_at: str | None
) -> None:
    run_migrations()
    con = get_connection()

    # Zapnutí: dopočítaný `next_run_at`. Vypnutí: NULL.
    con.execute(
        """
        UPDATE scheduled_scripts
        SET is_enabled = ?,
            next_run_at = ?,
            updated_at = CURRENT_TIMESTAMP
        WHERE id = ?
        """,
        (1 if is_enabled else 0, next_run_at if is_enabled else None, script_id),
    )

    con.commit()
    con.close()


def delete_scheduled_script(script_id: int) -> bool:
    run_migrations()
    con = get_connection()

    cur = con.execute(
        """
        DELETE FROM scheduled_scripts
        WHERE id = ?
          AND COALESCE(is_running, 0) = 0
        """,
        (script_id,),
    )
    deleted = cur.rowcount == 1
    con.commit()
    con.close()
    return deleted