"""
Strava API sync helpers.

OAuth: exchange_code() / refresh_tokens() talk to Strava's token endpoint.
get_valid_access_token() transparently refreshes an expired access token and
persists the rotated refresh token.

sync_strava_activities() lists the athlete's activities, fetches per-activity
streams, builds a fit_parser-shaped dict and hands it to persist_activity()
(shared with the file-upload path) so Strava activities get identical dedup,
PR, route and segment handling.

Tokens are Fernet-encrypted with the same SECRET_KEY scheme as Garmin creds.
"""
import logging
from datetime import date, datetime, timedelta, timezone
from typing import Optional

import httpx
import polyline as polyline_lib

from app.services.fit_parser import _bounding_box, _active_spans
from app.services.garmin_connect_sync import _fernet  # reuse the SECRET_KEY-derived Fernet

logger = logging.getLogger(__name__)

STRAVA_AUTHORIZE_URL = "https://www.strava.com/oauth/authorize"
STRAVA_TOKEN_URL = "https://www.strava.com/oauth/token"
STRAVA_API_BASE = "https://www.strava.com/api/v3"

# Scope needed to read all activities (including those marked "Only You").
STRAVA_SCOPE = "read,activity:read_all"

# Like Garmin: incremental syncs only re-scan the last day or two for late edits.
INCREMENTAL_BUFFER_DAYS = 1

# Strava activity type / sport_type → MileVault internal sport_type. Gym types map
# onto the internal vocabulary so sportColor() paints them red, GPS types green/etc.
STRAVA_SPORT_MAP = {
    "run": "running", "trailrun": "running", "virtualrun": "running",
    "ride": "cycling", "virtualride": "cycling", "mountainbikeride": "cycling",
    "gravelride": "cycling", "ebikeride": "cycling", "emountainbikeride": "cycling",
    "handcycle": "cycling", "velomobile": "cycling",
    "walk": "walking", "hike": "hiking",
    "swim": "swimming",
    "weighttraining": "strength_training", "workout": "training",
    "crossfit": "hiit", "hiit": "hiit",
    "elliptical": "fitness_equipment", "stairstepper": "fitness_equipment",
    "golf": "golf", "yoga": "yoga",
}


def encrypt_token(token: str) -> str:
    return _fernet().encrypt(token.encode()).decode()


def decrypt_token(enc: str) -> str:
    return _fernet().decrypt(enc.encode()).decode()


# ── OAuth ──────────────────────────────────────────────────────────────────────

def _token_request(payload: dict) -> dict:
    from app.core.config import settings
    payload = {
        "client_id": settings.strava_client_id,
        "client_secret": settings.strava_client_secret,
        **payload,
    }
    with httpx.Client(timeout=30) as client:
        resp = client.post(STRAVA_TOKEN_URL, data=payload)
    resp.raise_for_status()
    return resp.json()


def exchange_code(code: str) -> dict:
    """Exchange an authorization code for tokens. Returns the raw token dict
    (access_token, refresh_token, expires_at, athlete{...})."""
    return _token_request({"code": code, "grant_type": "authorization_code"})


def refresh_tokens(refresh_token: str) -> dict:
    """Get a fresh access token (and possibly rotated refresh token)."""
    return _token_request({"refresh_token": refresh_token, "grant_type": "refresh_token"})


def get_valid_access_token(cfg, db) -> str:
    """Return a usable access token for `cfg`, refreshing and persisting if the
    current one is expired or about to expire. `cfg` is a StravaConfig row."""
    now = datetime.now(timezone.utc)
    expires_at = cfg.expires_at
    if expires_at is not None and expires_at.tzinfo is None:
        expires_at = expires_at.replace(tzinfo=timezone.utc)

    if expires_at is None or expires_at <= now + timedelta(seconds=60):
        tok = refresh_tokens(decrypt_token(cfg.refresh_token_enc))
        cfg.access_token_enc = encrypt_token(tok["access_token"])
        cfg.refresh_token_enc = encrypt_token(tok["refresh_token"])
        cfg.expires_at = datetime.fromtimestamp(tok["expires_at"], tz=timezone.utc)
        db.commit()
        return tok["access_token"]

    return decrypt_token(cfg.access_token_enc)


# ── Activity sync ──────────────────────────────────────────────────────────────

def _api_get(client: httpx.Client, token: str, path: str, **params):
    resp = client.get(
        f"{STRAVA_API_BASE}{path}",
        headers={"Authorization": f"Bearer {token}"},
        params=params,
    )
    if resp.status_code == 429:
        raise StravaRateLimited()
    resp.raise_for_status()
    return resp.json()


class StravaRateLimited(Exception):
    """Raised when Strava returns HTTP 429 (rate limit exceeded)."""


def _streams_to_points(streams: dict, start_dt: datetime) -> list:
    """Convert Strava's key_by_type streams into fit_parser-shaped data points."""
    time_s = (streams.get("time") or {}).get("data") or []
    if not time_s:
        return []
    latlng = (streams.get("latlng") or {}).get("data") or []
    altitude = (streams.get("altitude") or {}).get("data") or []
    heartrate = (streams.get("heartrate") or {}).get("data") or []
    cadence = (streams.get("cadence") or {}).get("data") or []
    watts = (streams.get("watts") or {}).get("data") or []
    velocity = (streams.get("velocity_smooth") or {}).get("data") or []
    temp = (streams.get("temp") or {}).get("data") or []
    distance = (streams.get("distance") or {}).get("data") or []

    def at(arr, i):
        return arr[i] if i < len(arr) else None

    points = []
    for i, off in enumerate(time_s):
        ll = at(latlng, i)
        lat = ll[0] if ll else None
        lng = ll[1] if ll else None
        points.append({
            "timestamp": (start_dt + timedelta(seconds=off)).isoformat(),
            "latitude": lat, "longitude": lng,
            "altitude_m": at(altitude, i),
            "heart_rate": at(heartrate, i),
            "cadence": at(cadence, i),
            "speed_ms": at(velocity, i),
            "power": at(watts, i),
            "temperature_c": at(temp, i),
            "distance_m": at(distance, i),
        })
    return points


def _build_parsed(summary: dict, points: list) -> dict:
    """Assemble a fit_parser-shaped dict from a Strava summary + stream points."""
    raw_type = (summary.get("sport_type") or summary.get("type") or "workout")
    sport = STRAVA_SPORT_MAP.get(str(raw_type).lower(), str(raw_type).lower())

    start_str = summary.get("start_date")  # UTC ISO, e.g. 2020-01-01T08:00:00Z
    start_dt = datetime.fromisoformat(start_str.replace("Z", "+00:00")) if start_str else None

    coords = [(p["latitude"], p["longitude"]) for p in points if p["latitude"] and p["longitude"]]
    encoded = polyline_lib.encode(coords) if coords else (summary.get("map") or {}).get("summary_polyline")

    # Elevation loss from the altitude stream (summary only gives gain).
    alts = [p["altitude_m"] for p in points if p["altitude_m"] is not None]
    downhill = sum(max(0.0, alts[i-1] - alts[i]) for i in range(1, len(alts))) if alts else None

    return {
        "name": summary.get("name") or f"{sport.title()} {start_dt.date() if start_dt else ''}".strip(),
        "sport_type": sport,
        "start_time": start_dt.isoformat() if start_dt else None,
        "distance_m": summary.get("distance"),
        "duration_s": summary.get("elapsed_time"),
        "moving_time_s": summary.get("moving_time"),
        "elevation_gain_m": summary.get("total_elevation_gain"),
        "elevation_loss_m": downhill,
        "avg_heart_rate": summary.get("average_heartrate"),
        "max_heart_rate": summary.get("max_heartrate"),
        "avg_cadence": summary.get("average_cadence"),
        "avg_power": summary.get("average_watts"),
        "normalized_power": summary.get("weighted_average_watts"),
        "avg_speed_ms": summary.get("average_speed"),
        "max_speed_ms": summary.get("max_speed"),
        "active_spans": _active_spans(points),
        "avg_temperature_c": summary.get("average_temp"),
        "calories": summary.get("calories"),
        "training_stress_score": None,
        "vo2max_estimate": None,
        "polyline": encoded,
        "bounding_box": _bounding_box(coords),
        "source_type": "strava",
        "rejected_reason": None,
        "data_points": points,
        "laps": [],
    }


def sync_strava_activities(cfg, user_id: int, db, lookback_days: int = 30,
                           status_callback=None) -> int:
    """List the athlete's activities since the appropriate window, fetch streams
    for each new one and persist it. Returns the number of activities imported."""
    import time as _time
    from app.workers.tasks import persist_activity

    since = cfg.last_sync_at
    if since is not None and since.tzinfo is None:
        since = since.replace(tzinfo=timezone.utc)

    if since:
        after_dt = since - timedelta(days=INCREMENTAL_BUFFER_DAYS)
    elif lookback_days == -1:
        after_dt = datetime(2010, 1, 1, tzinfo=timezone.utc)
    else:
        after_dt = datetime.now(timezone.utc) - timedelta(days=max(lookback_days, 1))
    after_epoch = int(after_dt.timestamp())

    token = get_valid_access_token(cfg, db)
    imported = 0

    with httpx.Client(timeout=60) as client:
        # 1) Page through activity summaries (newest first within each page).
        summaries = []
        page = 1
        while True:
            batch = _api_get(client, token, "/athlete/activities",
                             after=after_epoch, page=page, per_page=100)
            if not batch:
                break
            summaries.extend(batch)
            if len(batch) < 100:
                break
            page += 1
            _time.sleep(0.3)

        total = len(summaries)
        if status_callback:
            status_callback(f"Syncing activities: 0/{total} imported")

        # 2) For each, fetch streams and persist. Oldest-first so PRs accrue in order.
        for idx, summary in enumerate(sorted(summaries, key=lambda s: s.get("start_date") or "")):
            sid = str(summary.get("id") or "").strip()
            if not sid:
                continue

            points = []
            try:
                streams = _api_get(
                    client, token, f"/activities/{sid}/streams",
                    keys="time,latlng,altitude,heartrate,cadence,watts,velocity_smooth,temp,distance",
                    key_by_type="true",
                )
                start_str = summary.get("start_date")
                start_dt = datetime.fromisoformat(start_str.replace("Z", "+00:00")) if start_str else None
                if start_dt:
                    points = _streams_to_points(streams, start_dt)
            except StravaRateLimited:
                # Out of quota — stop here; the next scheduled sync resumes the rest.
                if status_callback:
                    status_callback(f"Rate-limited by Strava — imported {imported}, will resume next sync")
                logger.warning("Strava rate limit hit for user %s after %d imports", user_id, imported)
                break
            except Exception as exc:
                logger.warning("Failed to fetch streams for Strava activity %s: %s", sid, exc)
                # Still persist from the summary (map polyline only, no per-point data).

            parsed = _build_parsed(summary, points)
            if not parsed.get("start_time"):
                continue

            try:
                result = persist_activity(db, user_id, parsed, strava_activity_id=sid)
                if result.get("status") == "ok":
                    imported += 1
            except Exception as exc:
                logger.warning("Failed to persist Strava activity %s: %s", sid, exc)
                db.rollback()

            if status_callback and (idx % 5 == 0 or idx == total - 1):
                status_callback(f"Syncing activities: {imported}/{total} imported")

            _time.sleep(0.3)   # be gentle on the rate limit

    return imported