"""RecurringElement service — tenant-scoped CRUD (AP0.9e)."""

from __future__ import annotations

from datetime import datetime
from typing import Any, Literal, Optional

from psycopg2.extras import RealDictCursor

from db import get_connection
from services.audit import log_audit
from services.initiatives import get_initiative

RecurringStatus = Literal["active", "paused", "ended"]

RECURRING_STATUSES = frozenset({"active", "paused", "ended"})

_RECURRING_COLUMNS = """
    id, tenant_id, initiative_id, title, description, status,
    interval_days, next_due_at, created_at, updated_at
"""


def _serialize_row(row: dict[str, Any]) -> dict[str, Any]:
    result = dict(row)
    for key in ("id", "tenant_id", "initiative_id"):
        if result.get(key):
            result[key] = str(result[key])
    for ts_key in ("created_at", "updated_at", "next_due_at"):
        if result.get(ts_key):
            result[ts_key] = result[ts_key].isoformat()
    return result


def _validate_status(status: str) -> None:
    if status not in RECURRING_STATUSES:
        raise ValueError(f"Ungültiger Recurring-Status: {status}")


def create_recurring_element(
    *,
    tenant_id: str,
    initiative_id: str,
    title: str,
    description: str = "",
    status: RecurringStatus = "active",
    interval_days: Optional[int] = None,
    next_due_at: Optional[datetime] = None,
    user_id: Optional[str] = None,
) -> dict[str, Any]:
    title = title.strip()
    if not title:
        raise ValueError("Titel ist erforderlich")
    _validate_status(status)
    if interval_days is not None and interval_days <= 0:
        raise ValueError("interval_days muss positiv sein")
    if not get_initiative(tenant_id=tenant_id, initiative_id=initiative_id):
        raise ValueError("Initiative nicht gefunden")

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                INSERT INTO recurring_elements (
                    tenant_id, initiative_id, title, description, status,
                    interval_days, next_due_at
                )
                VALUES (%s, %s, %s, %s, %s, %s, %s)
                RETURNING {_RECURRING_COLUMNS}
                """,
                (
                    tenant_id,
                    initiative_id,
                    title,
                    description,
                    status,
                    interval_days,
                    next_due_at,
                ),
            )
            row = _serialize_row(dict(cur.fetchone()))
        conn.commit()
    finally:
        conn.close()

    log_audit(
        "recurring.created",
        user_id=user_id,
        tenant_id=tenant_id,
        details={"recurring_id": row["id"], "initiative_id": initiative_id},
    )
    return row


def list_recurring_for_initiative(
    *, tenant_id: str, initiative_id: str
) -> list[dict[str, Any]]:
    if not get_initiative(tenant_id=tenant_id, initiative_id=initiative_id):
        raise ValueError("Initiative nicht gefunden")

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                SELECT {_RECURRING_COLUMNS}
                FROM recurring_elements
                WHERE tenant_id = %s AND initiative_id = %s
                ORDER BY updated_at DESC, title
                """,
                (tenant_id, initiative_id),
            )
            return [_serialize_row(dict(r)) for r in cur.fetchall()]
    finally:
        conn.close()


def get_recurring_element(
    *, tenant_id: str, recurring_id: str
) -> Optional[dict[str, Any]]:
    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                SELECT {_RECURRING_COLUMNS}
                FROM recurring_elements
                WHERE id = %s AND tenant_id = %s
                """,
                (recurring_id, tenant_id),
            )
            row = cur.fetchone()
            return _serialize_row(dict(row)) if row else None
    finally:
        conn.close()


def update_recurring_element(
    *,
    tenant_id: str,
    recurring_id: str,
    user_id: Optional[str] = None,
    title: Optional[str] = None,
    description: Optional[str] = None,
    status: Optional[RecurringStatus] = None,
    interval_days: Optional[int] = None,
    clear_interval_days: bool = False,
    next_due_at: Optional[datetime] = None,
    clear_next_due_at: bool = False,
) -> Optional[dict[str, Any]]:
    existing = get_recurring_element(tenant_id=tenant_id, recurring_id=recurring_id)
    if not existing:
        return None

    old_status = existing["status"]
    updates: list[str] = []
    params: list[Any] = []

    if title is not None:
        title = title.strip()
        if not title:
            raise ValueError("Titel ist erforderlich")
        updates.append("title = %s")
        params.append(title)
    if description is not None:
        updates.append("description = %s")
        params.append(description)
    if status is not None:
        _validate_status(status)
        updates.append("status = %s")
        params.append(status)
    if clear_interval_days:
        updates.append("interval_days = NULL")
    elif interval_days is not None:
        if interval_days <= 0:
            raise ValueError("interval_days muss positiv sein")
        updates.append("interval_days = %s")
        params.append(interval_days)
    if clear_next_due_at:
        updates.append("next_due_at = NULL")
    elif next_due_at is not None:
        updates.append("next_due_at = %s")
        params.append(next_due_at)

    if not updates:
        return existing

    updates.append("updated_at = NOW()")
    params.extend([recurring_id, tenant_id])

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                UPDATE recurring_elements
                SET {", ".join(updates)}
                WHERE id = %s AND tenant_id = %s
                RETURNING {_RECURRING_COLUMNS}
                """,
                params,
            )
            row = cur.fetchone()
            if not row:
                return None
            result = _serialize_row(dict(row))
        conn.commit()
    finally:
        conn.close()

    log_audit(
        "recurring.updated",
        user_id=user_id,
        tenant_id=tenant_id,
        details={"recurring_id": recurring_id},
    )
    if status is not None and status != old_status:
        log_audit(
            "recurring.status_changed",
            user_id=user_id,
            tenant_id=tenant_id,
            details={
                "recurring_id": recurring_id,
                "from_status": old_status,
                "to_status": status,
            },
        )
    return result


def delete_recurring_element(
    *,
    tenant_id: str,
    recurring_id: str,
    user_id: Optional[str] = None,
) -> bool:
    conn = get_connection()
    try:
        with conn.cursor() as cur:
            cur.execute(
                """
                DELETE FROM recurring_elements
                WHERE id = %s AND tenant_id = %s RETURNING id
                """,
                (recurring_id, tenant_id),
            )
            deleted = cur.fetchone() is not None
        conn.commit()
    finally:
        conn.close()

    if deleted:
        log_audit(
            "recurring.deleted",
            user_id=user_id,
            tenant_id=tenant_id,
            details={"recurring_id": recurring_id},
        )
    return deleted