"""BacklogItem service — tenant-scoped CRUD + convert (AP0.8c)."""

from __future__ import annotations

from typing import Any, Literal, Optional

from psycopg2.extras import RealDictCursor

from db import get_connection
from services.actions import create_action
from services.audit import log_audit
from services.initiatives import PRIORITIES, get_initiative
from services.plan_ist import validate_roadmap_item_in_initiative

BacklogStatus = Literal["new", "triaged", "accepted", "rejected", "converted"]

BACKLOG_STATUSES = frozenset({"new", "triaged", "accepted", "rejected", "converted"})

_BACKLOG_COLUMNS = """
    id, tenant_id, initiative_id, title, description, status,
    priority, roadmap_item_id, converted_action_id, 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", "converted_action_id", "roadmap_item_id"):
        if result.get(key):
            result[key] = str(result[key])
    if result.get("created_at"):
        result["created_at"] = result["created_at"].isoformat()
    if result.get("updated_at"):
        result["updated_at"] = result["updated_at"].isoformat()
    return result


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


def _validate_priority(priority: str) -> None:
    if priority not in PRIORITIES:
        raise ValueError(f"Ungültige Priorität: {priority}")


def create_backlog_item(
    *,
    tenant_id: str,
    initiative_id: str,
    title: str,
    description: str = "",
    status: BacklogStatus = "new",
    priority: str = "normal",
    roadmap_item_id: Optional[str] = None,
    user_id: Optional[str] = None,
) -> dict[str, Any]:
    title = title.strip()
    if not title:
        raise ValueError("Titel ist erforderlich")
    _validate_status(status)
    _validate_priority(priority)
    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:
            validate_roadmap_item_in_initiative(
                cur,
                tenant_id=tenant_id,
                initiative_id=initiative_id,
                roadmap_item_id=roadmap_item_id,
            )
            cur.execute(
                f"""
                INSERT INTO backlog_items (
                    tenant_id, initiative_id, title, description, status, priority,
                    roadmap_item_id
                )
                VALUES (%s, %s, %s, %s, %s, %s, %s)
                RETURNING {_BACKLOG_COLUMNS}
                """,
                (tenant_id, initiative_id, title, description, status, priority, roadmap_item_id),
            )
            row = _serialize_row(dict(cur.fetchone()))
        conn.commit()
    finally:
        conn.close()

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


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


def update_backlog_item(
    *,
    tenant_id: str,
    backlog_item_id: str,
    user_id: Optional[str] = None,
    title: Optional[str] = None,
    description: Optional[str] = None,
    status: Optional[BacklogStatus] = None,
    priority: Optional[str] = None,
    roadmap_item_id: Optional[str] = None,
    clear_roadmap_item: bool = False,
) -> Optional[dict[str, Any]]:
    existing = get_backlog_item(tenant_id=tenant_id, backlog_item_id=backlog_item_id)
    if not existing:
        return None
    if existing["status"] == "converted":
        raise ValueError("Konvertiertes Backlog-Item kann nicht bearbeitet werden")

    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 priority is not None:
        _validate_priority(priority)
        updates.append("priority = %s")
        params.append(priority)
    if clear_roadmap_item:
        updates.append("roadmap_item_id = NULL")
    elif roadmap_item_id is not None:
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                validate_roadmap_item_in_initiative(
                    cur,
                    tenant_id=tenant_id,
                    initiative_id=existing["initiative_id"],
                    roadmap_item_id=roadmap_item_id,
                )
        finally:
            conn.close()
        updates.append("roadmap_item_id = %s")
        params.append(roadmap_item_id)

    if not updates:
        return existing

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

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

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


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

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


def convert_backlog_to_action(
    *,
    tenant_id: str,
    backlog_item_id: str,
    user_id: Optional[str] = None,
    assigned_actor_ids: Optional[list[str]] = None,
) -> dict[str, Any]:
    existing = get_backlog_item(tenant_id=tenant_id, backlog_item_id=backlog_item_id)
    if not existing:
        raise ValueError("Backlog-Item nicht gefunden")
    if existing["status"] == "converted":
        raise ValueError("Backlog-Item wurde bereits konvertiert")
    if existing["status"] not in ("accepted", "triaged", "new"):
        raise ValueError("Backlog-Item kann in diesem Status nicht konvertiert werden")

    action = create_action(
        tenant_id=tenant_id,
        initiative_id=existing["initiative_id"],
        title=existing["title"],
        description=existing["description"] or "",
        priority=existing["priority"],
        roadmap_item_id=existing.get("roadmap_item_id"),
        assigned_actor_ids=assigned_actor_ids or [],
        user_id=user_id,
    )

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                UPDATE backlog_items
                SET status = 'converted',
                    converted_action_id = %s,
                    updated_at = NOW()
                WHERE id = %s AND tenant_id = %s
                RETURNING {_BACKLOG_COLUMNS}
                """,
                (action["id"], backlog_item_id, tenant_id),
            )
            row = _serialize_row(dict(cur.fetchone()))
        conn.commit()
    finally:
        conn.close()

    log_audit(
        "backlog.converted_to_action",
        user_id=user_id,
        tenant_id=tenant_id,
        details={
            "backlog_item_id": backlog_item_id,
            "action_id": action["id"],
            "initiative_id": existing["initiative_id"],
        },
    )
    return {"backlog_item": row, "action": action}