"""Freunde: Anfrage schicken, annehmen, ablehnen, entfernen.

Freunde sind die Grundlage fürs Teilen: Vorratslisten und Kanban-Projekte lassen sich nur mit Freunden teilen,
auf der Reise-Karte erscheinen nur Städte von Freunden. Administratoren gelten diese Einschränkungen nicht.
"""
from fastapi import APIRouter, Depends, HTTPException

from .auth import current_user
from .common import now_iso
from .db import transaction

router = APIRouter()

MIN_SEARCH = 2


def _pair(a: int, b: int) -> tuple:
    return (a, b) if a < b else (b, a)


def friend_ids(conn, user_id: int) -> set:
    """IDs aller angenommenen Freunde."""
    rows = conn.execute(
        "SELECT user_a, user_b FROM friendships WHERE accepted = 1 AND (user_a = ? OR user_b = ?)", (user_id, user_id)
    )
    return {r["user_b"] if r["user_a"] == user_id else r["user_a"] for r in rows}


def shareable(conn, user: dict) -> list:
    """Konten, mit denen man teilen darf: Freunde – Administratoren alle (außer sich selbst)."""
    rows = conn.execute("SELECT id, display_name FROM users WHERE id != ? ORDER BY display_name COLLATE NOCASE", (user["id"],))
    allowed = None if user["isAdmin"] else friend_ids(conn, user["id"])
    return [{"id": r["id"], "name": r["display_name"]} for r in rows if allowed is None or r["id"] in allowed]


def check_shareable(conn, user: dict, ids, keep=()) -> None:
    """Neue Mitglieder müssen Freunde sein (Admins: beliebig). keep: schon eingetragene Mitglieder dürfen bleiben."""
    allowed = {u["id"] for u in shareable(conn, user)} | set(keep)
    if any(i not in allowed for i in ids):
        raise HTTPException(400, "Teilen geht nur mit Freunden – bitte zuerst unter „Freunde“ hinzufügen.")


def _person(row) -> dict:
    return {"id": row["id"], "name": row["display_name"], "username": row["username"]}


def _state(conn, user_id: int) -> dict:
    rows = conn.execute(
        """SELECT u.id, u.username, u.display_name, f.accepted, f.requested_by FROM friendships f
           JOIN users u ON u.id = CASE WHEN f.user_a = ? THEN f.user_b ELSE f.user_a END
           WHERE f.user_a = ? OR f.user_b = ? ORDER BY u.display_name COLLATE NOCASE""",
        (user_id, user_id, user_id),
    ).fetchall()
    return {
        "friends": [_person(r) for r in rows if r["accepted"]],
        "incoming": [_person(r) for r in rows if not r["accepted"] and r["requested_by"] != user_id],
        "outgoing": [_person(r) for r in rows if not r["accepted"] and r["requested_by"] == user_id],
    }


@router.get("/api/freunde")
def get_friends(user: dict = Depends(current_user)):
    with transaction() as conn:
        return _state(conn, user["id"])


@router.get("/api/freunde/suche")
def search_users(q: str = "", user: dict = Depends(current_user)):
    """Konten nach Name oder Benutzername suchen (ab 2 Zeichen), mit Stand der Freundschaft."""
    q = q.strip()
    if len(q) < MIN_SEARCH:
        return []
    like = "%" + q.replace("\\", "\\\\").replace("%", "\\%").replace("_", "\\_") + "%"
    with transaction() as conn:
        rows = conn.execute(
            """SELECT id, username, display_name FROM users
               WHERE id != ? AND (display_name LIKE ? ESCAPE '\\' OR username LIKE ? ESCAPE '\\')
               ORDER BY display_name COLLATE NOCASE LIMIT 20""",
            (user["id"], like, like),
        ).fetchall()
        state = _state(conn, user["id"])
    status = {p["id"]: s for s, key in (("freund", "friends"), ("angefragt", "outgoing"), ("eingeladen", "incoming")) for p in state[key]}
    return [{**_person(r), "status": status.get(r["id"])} for r in rows]


@router.post("/api/freunde/{other_id}")
def befriend(other_id: int, user: dict = Depends(current_user)):
    """Anfrage schicken – oder eine offene Anfrage der anderen Person annehmen."""
    if other_id == user["id"]:
        raise HTTPException(400, "Mit sich selbst befreundet sein geht nicht.")
    a, b = _pair(user["id"], other_id)
    with transaction() as conn:
        if not conn.execute("SELECT 1 FROM users WHERE id = ?", (other_id,)).fetchone():
            raise HTTPException(404, "Konto nicht gefunden.")
        row = conn.execute("SELECT * FROM friendships WHERE user_a = ? AND user_b = ?", (a, b)).fetchone()
        if not row:
            conn.execute(
                "INSERT INTO friendships (user_a, user_b, requested_by, accepted, created_at) VALUES (?, ?, ?, 0, ?)",
                (a, b, user["id"], now_iso()),
            )
        elif not row["accepted"] and row["requested_by"] != user["id"]:
            conn.execute("UPDATE friendships SET accepted = 1 WHERE user_a = ? AND user_b = ?", (a, b))
        return _state(conn, user["id"])


@router.delete("/api/freunde/{other_id}")
def unfriend(other_id: int, user: dict = Depends(current_user)):
    """Anfrage zurückziehen oder ablehnen bzw. Freundschaft beenden."""
    a, b = _pair(user["id"], other_id)
    with transaction() as conn:
        conn.execute("DELETE FROM friendships WHERE user_a = ? AND user_b = ?", (a, b))
        return _state(conn, user["id"])