from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from pydantic import BaseModel
from typing import Optional
from datetime import datetime

from app.core.database import get_db
from app.core.security import get_current_user
from app.core.config import settings
from app.models.user import User, GarminConnectConfig

router = APIRouter()


class GarminConfigIn(BaseModel):
    email: str
    password: Optional[str] = None       # plaintext; encrypted before storage. None = keep existing.
    sync_enabled: bool = True
    sync_activities: bool = True
    sync_wellness: bool = True
    sync_lookback_days: int = 30         # days to look back on first sync; -1 = all-time


class GarminConfigOut(BaseModel):
    email: str
    sync_enabled: bool
    sync_activities: bool
    sync_wellness: bool
    sync_lookback_days: int
    sync_interval_minutes: int           # how often the automatic sync runs
    last_sync_at: Optional[datetime]
    last_sync_status: Optional[str]
    connected: bool

    class Config:
        from_attributes = True


def _wants_more_history(old: int, new: int) -> bool:
    """True if `new` lookback requests older data than `old` (-1 = all-time)."""
    if new == old:
        return False
    if new == -1:          # all-time requested where it wasn't before
        return True
    if old == -1:          # was all-time, now finite → narrower, not more
        return False
    return new > old


@router.get("/config", response_model=GarminConfigOut)
async def get_config(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(GarminConnectConfig).where(GarminConnectConfig.user_id == current_user.id)
    )
    cfg = result.scalar_one_or_none()
    if not cfg:
        return GarminConfigOut(
            email="", sync_enabled=False, sync_activities=True,
            sync_wellness=True, sync_lookback_days=30,
            sync_interval_minutes=settings.garmin_sync_interval_minutes,
            last_sync_at=None, last_sync_status=None, connected=False,
        )
    return GarminConfigOut(
        email=cfg.email,
        sync_enabled=cfg.sync_enabled,
        sync_activities=cfg.sync_activities,
        sync_wellness=cfg.sync_wellness,
        sync_lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
        sync_interval_minutes=settings.garmin_sync_interval_minutes,
        last_sync_at=cfg.last_sync_at,
        last_sync_status=cfg.last_sync_status,
        connected=True,
    )


@router.put("/config", response_model=GarminConfigOut)
async def save_config(
    body: GarminConfigIn,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """
    Save Garmin Connect settings. If a password is provided, re-authenticates and
    refreshes the stored OAuth token. If no password is provided, only updates the
    non-credential settings (toggles, lookback days) without re-logging in.
    """
    from app.services.garmin_connect_sync import encrypt_password, authenticate_garmin

    result = await db.execute(
        select(GarminConnectConfig).where(GarminConnectConfig.user_id == current_user.id)
    )
    cfg = result.scalar_one_or_none()

    if body.password:
        # Credentials update — test-login before saving
        enc = encrypt_password(body.password)
        try:
            garmin, token_store = authenticate_garmin(body.email, enc, None)
        except Exception as exc:
            raise HTTPException(status_code=400, detail=f"Garmin login failed: {exc}")

        if cfg:
            cfg.email = body.email
            cfg.password_enc = enc
            cfg.token_store = token_store
            cfg.last_sync_status = "Credentials updated"
        else:
            cfg = GarminConnectConfig(
                user_id=current_user.id,
                email=body.email,
                password_enc=enc,
                token_store=token_store,
                last_sync_status="Connected",
            )
            db.add(cfg)
    else:
        # Settings-only update — password unchanged
        if not cfg:
            raise HTTPException(status_code=400, detail="No Garmin account connected — password required for first-time setup")

    # If the user is now asking for MORE history than before, reset last_sync_at so
    # the next sync treats it as a first sync and does a one-time backfill of the
    # wider lookback window (then resumes cheap incremental syncs). Scheduled syncs
    # otherwise only refresh the last day or two, so without this an increased
    # lookback would never actually fetch the older data.
    old_lookback = cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30
    if _wants_more_history(old_lookback, body.sync_lookback_days):
        cfg.last_sync_at = None
        cfg.last_sync_status = "Lookback increased — backfill on next sync"

    cfg.sync_enabled = body.sync_enabled
    cfg.sync_activities = body.sync_activities
    cfg.sync_wellness = body.sync_wellness
    cfg.sync_lookback_days = body.sync_lookback_days

    await db.commit()
    await db.refresh(cfg)

    return GarminConfigOut(
        email=cfg.email,
        sync_enabled=cfg.sync_enabled,
        sync_activities=cfg.sync_activities,
        sync_wellness=cfg.sync_wellness,
        sync_lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
        sync_interval_minutes=settings.garmin_sync_interval_minutes,
        last_sync_at=cfg.last_sync_at,
        last_sync_status=cfg.last_sync_status,
        connected=True,
    )


@router.delete("/config")
async def delete_config(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(GarminConnectConfig).where(GarminConnectConfig.user_id == current_user.id)
    )
    cfg = result.scalar_one_or_none()
    if cfg:
        await db.delete(cfg)
        await db.commit()
    return {"status": "ok"}


@router.post("/trigger")
async def trigger_sync(
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Enqueue an immediate Garmin Connect sync for this user."""
    result = await db.execute(
        select(GarminConnectConfig).where(GarminConnectConfig.user_id == current_user.id)
    )
    cfg = result.scalar_one_or_none()
    if not cfg or not cfg.sync_enabled:
        raise HTTPException(status_code=400, detail="Garmin Connect sync is not configured or disabled")

    from app.workers.tasks import sync_garmin_connect_user
    task = sync_garmin_connect_user.delay(current_user.id)
    return {"task_id": task.id, "status": "queued"}