"""Milestone service — tenant-scoped CRUD (AP0.8d)."""

from __future__ import annotations

from datetime import date
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

MilestoneStatus = Literal[
    "planned", "active", "at_risk", "reached", "moved", "discarded"
]

MILESTONE_STATUSES = frozenset(
    {"planned", "active", "at_risk", "reached", "moved", "discarded"}
)


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])
    if result.get("target_date"):
        result["target_date"] = (
            result["target_date"].isoformat()
            if hasattr(result["target_date"], "isoformat")
            else str(result["target_date"])
        )
    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 MILESTONE_STATUSES:
        raise ValueError(f"Ungültiger Meilenstein-Status: {status}")


def create_milestone(
    *,
    tenant_id: str,
    initiative_id: str,
    title: str,
    goal_description: str = "",
    status: MilestoneStatus = "planned",
    target_date: Optional[date] = None,
    user_id: Optional[str] = None,
) -> dict[str, Any]:
    title = title.strip()
    if not title:
        raise ValueError("Titel ist erforderlich")
    _validate_status(status)
    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(
                """
                INSERT INTO milestones (
                    tenant_id, initiative_id, title, goal_description, status, target_date
                )
                VALUES (%s, %s, %s, %s, %s, %s)
                RETURNING id, tenant_id, initiative_id, title, goal_description, status,
                          target_date, created_at, updated_at
                """,
                (tenant_id, initiative_id, title, goal_description, status, target_date),
            )
            row = _serialize_row(dict(cur.fetchone()))
        conn.commit()
    finally:
        conn.close()

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


def list_milestones_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(
                """
                SELECT id, tenant_id, initiative_id, title, goal_description, status,
                       target_date, created_at, updated_at
                FROM milestones
                WHERE tenant_id = %s AND initiative_id = %s
                ORDER BY target_date NULLS LAST, updated_at DESC, title
                """,
                (tenant_id, initiative_id),
            )
            return [_serialize_row(dict(r)) for r in cur.fetchall()]
    finally:
        conn.close()


def get_milestone(*, tenant_id: str, milestone_id: str) -> Optional[dict[str, Any]]:
    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                """
                SELECT id, tenant_id, initiative_id, title, goal_description, status,
                       target_date, created_at, updated_at
                FROM milestones
                WHERE id = %s AND tenant_id = %s
                """,
                (milestone_id, tenant_id),
            )
            row = cur.fetchone()
            return _serialize_row(dict(row)) if row else None
    finally:
        conn.close()


def update_milestone(
    *,
    tenant_id: str,
    milestone_id: str,
    user_id: Optional[str] = None,
    title: Optional[str] = None,
    goal_description: Optional[str] = None,
    status: Optional[MilestoneStatus] = None,
    target_date: Optional[date] = None,
    clear_target_date: bool = False,
) -> Optional[dict[str, Any]]:
    existing = get_milestone(tenant_id=tenant_id, milestone_id=milestone_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 goal_description is not None:
        updates.append("goal_description = %s")
        params.append(goal_description)
    if status is not None:
        _validate_status(status)
        updates.append("status = %s")
        params.append(status)
    if clear_target_date:
        updates.append("target_date = NULL")
    elif target_date is not None:
        updates.append("target_date = %s")
        params.append(target_date)

    if not updates:
        return existing

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

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

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


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

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