import logging
import secrets
import time
from datetime import datetime, timezone
from typing import Optional
from urllib.parse import urlencode

import requests as http_requests
from fastapi import APIRouter, Depends, HTTPException, Query, Request
from fastapi.responses import RedirectResponse
from pydantic import BaseModel
from sqlalchemy.orm import Session

import models
from auth import get_current_user
from database import get_db

logger = logging.getLogger(__name__)
router = APIRouter()

HA_DEFAULT_COLOR = "#03a9f4"

# In-memory store for pending OAuth states (short-lived, ~10 min TTL)
_pending_oauth: dict[str, dict] = {}


def _cleanup_pending():
    now = time.time()
    for k in [k for k, v in _pending_oauth.items() if v["expires"] < now]:
        _pending_oauth.pop(k, None)


# ── Auth helpers ──────────────────────────────────────────

def _ha_refresh(url: str, refresh_token: str, client_id: str) -> tuple:
    """Refresh grant → (access_token, expires_in)"""
    resp = http_requests.post(
        f"{url.rstrip('/')}/auth/token",
        data={
            "grant_type": "refresh_token",
            "refresh_token": refresh_token,
            "client_id": client_id,
        },
        timeout=10,
        verify=False,
    )
    resp.raise_for_status()
    data = resp.json()
    return data["access_token"], data.get("expires_in", 1800)


def _get_valid_token(account: models.HomeAssistantAccount, db: Session) -> str:
    """Return a valid access token, refreshing if necessary."""
    if account.auth_method != "oauth":
        return account.token  # Long-Lived Token läuft nicht ab
    now = datetime.now(timezone.utc)
    if account.token_expiry and account.token_expiry.replace(tzinfo=timezone.utc) > now:
        return account.token
    # Needs refresh
    try:
        access_token, expires_in = _ha_refresh(
            account.url, account.refresh_token, account.client_id or ""
        )
    except Exception as exc:
        logger.error("HA token refresh failed for %s: %s", account.name, exc)
        raise HTTPException(401, "Home Assistant Token abgelaufen, bitte Konto neu verbinden")
    account.token = access_token
    account.token_expiry = datetime.fromtimestamp(now.timestamp() + expires_in, tz=timezone.utc)
    db.commit()
    return access_token


# ── HA API helpers ────────────────────────────────────────

def _ha_get_calendars(url: str, token: str) -> list:
    try:
        resp = http_requests.get(
            f"{url.rstrip('/')}/api/calendars",
            headers={"Authorization": f"Bearer {token}"},
            timeout=10,
            verify=False,
        )
        resp.raise_for_status()
        return resp.json()
    except http_requests.exceptions.ConnectionError:
        raise HTTPException(503, "Home Assistant nicht erreichbar")
    except http_requests.exceptions.Timeout:
        raise HTTPException(503, "Home Assistant antwortet nicht (Timeout)")
    except http_requests.exceptions.HTTPError as e:
        if e.response is not None and e.response.status_code == 401:
            raise HTTPException(400, "Ungültiger Access Token")
        raise HTTPException(502, f"Home Assistant Fehler: {e}")


def _ha_get_events(url: str, token: str, entity_id: str, start_dt: datetime, end_dt: datetime) -> list:
    try:
        resp = http_requests.get(
            f"{url.rstrip('/')}/api/calendars/{entity_id}",
            headers={"Authorization": f"Bearer {token}"},
            params={"start": start_dt.isoformat(), "end": end_dt.isoformat()},
            timeout=15,
            verify=False,
        )
        resp.raise_for_status()
        return resp.json()
    except http_requests.exceptions.ConnectionError:
        raise http_requests.exceptions.ConnectionError(f"HA nicht erreichbar für {entity_id}")
    except http_requests.exceptions.Timeout:
        raise http_requests.exceptions.Timeout(f"HA Timeout für {entity_id}")


def _ha_update_event(url: str, token: str, entity_id: str, uid: str, data: dict):
    """Update an event via HA service call API (calendar.update_event)."""
    base = url.rstrip("/")
    headers = {"Authorization": f"Bearer {token}", "Content-Type": "application/json"}
    body = {"entity_id": entity_id, "uid": uid}
    if "title" in data:
        body["summary"] = data["title"]
    if "description" in data:
        body["description"] = data["description"]
    if "location" in data:
        body["location"] = data["location"]
    if "start" in data and "end" in data:
        if data.get("allDay"):
            body["dtstart"] = data["start"][:10]
            body["dtend"] = data["end"][:10]
        else:
            s = data["start"].replace("Z", "").replace("T", " ")
            e = data["end"].replace("Z", "").replace("T", " ")
            # Strip timezone offset if present (e.g. +02:00)
            if "+" in s and s.index("+") > 10:
                s = s[:s.index("+")]
            if "+" in e and e.index("+") > 10:
                e = e[:e.index("+")]
            body["dtstart"] = s
            body["dtend"] = e
    resp = http_requests.post(
        f"{base}/api/services/calendar/update_event",
        headers=headers, json=body, timeout=15, verify=False,
    )
    resp.raise_for_status()
    return resp


def _ha_delete_event(url: str, token: str, entity_id: str, uid: str):
    """Delete an event via HA service call API (calendar.delete_event)."""
    base = url.rstrip("/")
    headers = {"Authorization": f"Bearer {token}", "Content-Type": "application/json"}
    resp = http_requests.post(
        f"{base}/api/services/calendar/delete_event",
        headers=headers,
        json={"entity_id": entity_id, "uid": uid},
        timeout=15, verify=False,
    )
    resp.raise_for_status()
    return resp


def _parse_ha_event(ev: dict, cal_db_id: int, cal_name: str, cal_color: str) -> dict:
    start = ev.get("start", {})
    end = ev.get("end", {})
    all_day = "date" in start and "dateTime" not in start
    return {
        "id": ev.get("uid") or f"ha-{cal_db_id}-{ev.get('summary', '')}",
        "url": f"homeassistant://{cal_db_id}/{ev.get('uid', '')}",
        "title": ev.get("summary", "(Kein Titel)"),
        "start": start.get("dateTime") or start.get("date", ""),
        "end": end.get("dateTime") or end.get("date", ""),
        "allDay": all_day,
        "location": ev.get("location", ""),
        "description": ev.get("description", ""),
        "color": None,
        "calendar_id": f"homeassistant-{cal_db_id}",
        "calendar_name": cal_name,
        "calendarColor": cal_color,
        "source": "homeassistant",
    }


def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_dt: datetime, db: Session) -> list:
    all_events = []
    try:
        token = _get_valid_token(account, db)
    except Exception as exc:
        logger.error("HA token error for %s: %s", account.name, exc)
        raise
    for cal in account.calendars:
        if not cal.enabled or cal.sidebar_hidden:
            continue
        try:
            raw = _ha_get_events(account.url, token, cal.entity_id, start_dt, end_dt)
            color = cal.color or HA_DEFAULT_COLOR
            for ev in raw:
                all_events.append(_parse_ha_event(ev, cal.id, cal.name, color))
        except Exception as exc:
            logger.error("HA event fetch error %s (%s): %s", cal.entity_id, account.name, exc)
    return all_events


# ── Serialization ─────────────────────────────────────────

def _account_dict(a: models.HomeAssistantAccount) -> dict:
    return {
        "id": a.id,
        "name": a.name,
        "url": a.url,
        "auth_method": a.auth_method or "token",
        "calendars": [
            {
                "id": c.id,
                "name": c.name,
                "entity_id": c.entity_id,
                "color": c.color or HA_DEFAULT_COLOR,
                "enabled": c.enabled,
                "sidebar_hidden": bool(c.sidebar_hidden),
            }
            for c in a.calendars
        ],
    }


# ── Pydantic models ───────────────────────────────────────

class HAAccountCreate(BaseModel):
    name: str
    url: str
    token: str


class HAOAuthStart(BaseModel):
    name: str
    url: str
    client_id: str
    redirect_uri: str


class HACalendarUpdate(BaseModel):
    enabled: Optional[bool] = None
    color: Optional[str] = None
    name: Optional[str] = None
    sidebar_hidden: Optional[bool] = None


# ── Endpoints ─────────────────────────────────────────────

@router.get("/accounts")
def list_accounts(
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    accounts = (
        db.query(models.HomeAssistantAccount)
        .filter(models.HomeAssistantAccount.user_id == current_user.id)
        .all()
    )
    return [_account_dict(a) for a in accounts]


@router.post("/accounts")
def add_account(
    data: HAAccountCreate,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    """Create a HA account from a Long-Lived Access Token."""
    remote_cals = _ha_get_calendars(data.url, data.token)

    account = models.HomeAssistantAccount(
        user_id=current_user.id,
        name=data.name,
        url=data.url,
        token=data.token,
        auth_method="token",
        refresh_token=None,
        token_expiry=None,
    )
    db.add(account)
    db.flush()

    for cal in remote_cals:
        entity_id = cal.get("entity_id", "")
        if not entity_id:
            continue
        db.add(models.HomeAssistantCalendar(
            account_id=account.id,
            entity_id=entity_id,
            name=cal.get("name") or entity_id,
            color=None,
            enabled=True,
        ))

    db.commit()
    db.refresh(account)
    return _account_dict(account)


@router.post("/auth-url")
def oauth_start(
    data: HAOAuthStart,
    current_user: models.User = Depends(get_current_user),
):
    """Start the OAuth flow: store pending state, return HA authorization URL."""
    _cleanup_pending()
    state_token = secrets.token_urlsafe(32)
    _pending_oauth[state_token] = {
        "user_id": current_user.id,
        "ha_url": data.url.rstrip('/'),
        "name": data.name,
        "client_id": data.client_id,
        "redirect_uri": data.redirect_uri,
        "expires": time.time() + 600,
    }
    params = {
        "client_id": data.client_id,
        "redirect_uri": data.redirect_uri,
        "state": state_token,
        "response_type": "code",
    }
    return {"url": f"{data.url.rstrip('/')}/auth/authorize?{urlencode(params)}"}


@router.get("/callback")
def oauth_callback(
    request: Request,
    code: str = Query(""),
    state: str = Query(""),
    error: str = Query(""),
    db: Session = Depends(get_db),
):
    """Callback from Home Assistant after user authorization."""
    if error or not code:
        return RedirectResponse(url=f"/?ha_error={error or 'no_code'}", status_code=302)

    pending = _pending_oauth.pop(state, None)
    if not pending or pending["expires"] < time.time():
        return RedirectResponse(url="/?ha_error=state_expired", status_code=302)

    ha_url = pending["ha_url"]
    client_id = pending["client_id"]

    # Exchange code for tokens
    try:
        resp = http_requests.post(
            f"{ha_url}/auth/token",
            data={
                "grant_type": "authorization_code",
                "code": code,
                "client_id": client_id,
            },
            timeout=15,
            verify=False,
        )
    except Exception as exc:
        logger.error("HA token exchange connection error: %s", exc)
        return RedirectResponse(url="/?ha_error=ha_unreachable", status_code=302)

    if resp.status_code != 200:
        logger.error("HA token exchange failed (%s): %s", resp.status_code, resp.text)
        return RedirectResponse(url="/?ha_error=token_exchange_failed", status_code=302)

    tokens = resp.json()
    access_token = tokens["access_token"]
    refresh_token = tokens.get("refresh_token", "")
    expires_in = tokens.get("expires_in", 1800)
    now = datetime.now(timezone.utc)

    try:
        remote_cals = _ha_get_calendars(ha_url, access_token)
    except HTTPException as exc:
        logger.error("HA calendar fetch failed after OAuth: %s", exc.detail)
        return RedirectResponse(url="/?ha_error=calendars_failed", status_code=302)

    account = models.HomeAssistantAccount(
        user_id=pending["user_id"],
        name=pending["name"],
        url=ha_url,
        token=access_token,
        auth_method="oauth",
        refresh_token=refresh_token,
        token_expiry=datetime.fromtimestamp(now.timestamp() + expires_in, tz=timezone.utc),
        client_id=client_id,
    )
    db.add(account)
    db.flush()

    for cal in remote_cals:
        entity_id = cal.get("entity_id", "")
        if not entity_id:
            continue
        db.add(models.HomeAssistantCalendar(
            account_id=account.id,
            entity_id=entity_id,
            name=cal.get("name") or entity_id,
            color=None,
            enabled=True,
        ))

    db.commit()
    return RedirectResponse(url="/?ha_connected=1", status_code=302)


@router.delete("/accounts/{account_id}")
def delete_account(
    account_id: int,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    acc = (
        db.query(models.HomeAssistantAccount)
        .filter(
            models.HomeAssistantAccount.id == account_id,
            models.HomeAssistantAccount.user_id == current_user.id,
        )
        .first()
    )
    if not acc:
        raise HTTPException(404, "Account not found")
    db.delete(acc)
    db.commit()
    return {"ok": True}


@router.post("/accounts/{account_id}/sync")
def sync_account(
    account_id: int,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    acc = (
        db.query(models.HomeAssistantAccount)
        .filter(
            models.HomeAssistantAccount.id == account_id,
            models.HomeAssistantAccount.user_id == current_user.id,
        )
        .first()
    )
    if not acc:
        raise HTTPException(404, "Account not found")

    token = _get_valid_token(acc, db)
    remote_cals = _ha_get_calendars(acc.url, token)
    existing = {c.entity_id: c for c in acc.calendars}

    for cal in remote_cals:
        entity_id = cal.get("entity_id", "")
        if not entity_id:
            continue
        if entity_id not in existing:
            db.add(models.HomeAssistantCalendar(
                account_id=acc.id,
                entity_id=entity_id,
                name=cal.get("name") or entity_id,
                color=None,
                enabled=True,
            ))
        else:
            existing[entity_id].name = cal.get("name") or entity_id

    db.commit()
    db.refresh(acc)
    return _account_dict(acc)


@router.put("/calendars/{calendar_id}")
def update_calendar(
    calendar_id: int,
    data: HACalendarUpdate,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    cal = (
        db.query(models.HomeAssistantCalendar)
        .join(models.HomeAssistantAccount)
        .filter(
            models.HomeAssistantCalendar.id == calendar_id,
            models.HomeAssistantAccount.user_id == current_user.id,
        )
        .first()
    )
    if not cal:
        raise HTTPException(404, "Calendar not found")
    if data.enabled is not None:
        cal.enabled = data.enabled
    if data.color is not None:
        cal.color = data.color
    if data.name is not None:
        cal.name = data.name
    if data.sidebar_hidden is not None:
        cal.sidebar_hidden = data.sidebar_hidden
    db.commit()
    return {"ok": True}


# ── Event CRUD ───────────────────────────────────────────

class HAEventUpdate(BaseModel):
    title: Optional[str] = None
    start: Optional[str] = None
    end: Optional[str] = None
    allDay: Optional[bool] = None
    location: Optional[str] = None
    description: Optional[str] = None


@router.put("/events/{calendar_id}/{uid}")
def update_event(
    calendar_id: int,
    uid: str,
    data: HAEventUpdate,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    cal = (
        db.query(models.HomeAssistantCalendar)
        .join(models.HomeAssistantAccount)
        .filter(
            models.HomeAssistantCalendar.id == calendar_id,
            models.HomeAssistantAccount.user_id == current_user.id,
        )
        .first()
    )
    if not cal:
        raise HTTPException(404, "Calendar not found")
    account = cal.account
    token = _get_valid_token(account, db)
    try:
        _ha_update_event(
            account.url, token, cal.entity_id, uid,
            data.model_dump(exclude_none=True),
        )
        return {"ok": True}
    except Exception as exc:
        raise HTTPException(500, f"HA event update failed: {exc}")


@router.delete("/events/{calendar_id}/{uid}")
def delete_event(
    calendar_id: int,
    uid: str,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user),
):
    cal = (
        db.query(models.HomeAssistantCalendar)
        .join(models.HomeAssistantAccount)
        .filter(
            models.HomeAssistantCalendar.id == calendar_id,
            models.HomeAssistantAccount.user_id == current_user.id,
        )
        .first()
    )
    if not cal:
        raise HTTPException(404, "Calendar not found")
    account = cal.account
    token = _get_valid_token(account, db)
    try:
        _ha_delete_event(account.url, token, cal.entity_id, uid)
        return {"ok": True}
    except Exception as exc:
        raise HTTPException(500, f"HA event delete failed: {exc}")