import json
import logging
import os
import tempfile
from datetime import timezone as dt_timezone
from math import asin, cos, radians, sin, sqrt
from typing import Optional

from django.conf import settings
from django.contrib.auth import get_user_model
from django.core.files import File

from locations.models import GeoLocation
from scrobbles.models import Scrobble
from trails.models import Trail, TrailLogData

logger = logging.getLogger(__name__)

User = get_user_model()


def haversine(lat1, lon1, lat2, lon2):
    R = 6371000
    dlat = radians(lat2 - lat1)
    dlon = radians(lon2 - lon1)
    a = sin(dlat / 2) ** 2 + cos(radians(lat1)) * cos(radians(lat2)) * sin(dlon / 2) ** 2
    return R * 2 * asin(sqrt(a))


def compute_trail_stats(points):
    distance_m = 0.0
    elevation_gain = 0.0
    first_time = None
    last_time = None

    for i in range(1, len(points)):
        lat1, lon1, ele1, t1 = points[i - 1]
        lat2, lon2, ele2, t2 = points[i]

        if lat1 is not None and lon1 is not None and lat2 is not None and lon2 is not None:
            distance_m += haversine(lat1, lon1, lat2, lon2)

        if ele1 is not None and ele2 is not None and ele2 > ele1:
            elevation_gain += ele2 - ele1

        if first_time is None and t1 is not None:
            first_time = t1
        if t2 is not None:
            last_time = t2

    moving_time = (
        (last_time - first_time).total_seconds()
        if first_time and last_time
        else 0
    )
    avg_speed_kmh = (distance_m / 1000) / (moving_time / 3600) if moving_time > 0 else 0.0

    return {
        "distance_km": round(distance_m / 1000, 2),
        "elevation_gain_m": round(elevation_gain, 1),
        "moving_time_seconds": int(moving_time),
        "avg_speed_kmh": round(avg_speed_kmh, 2),
    }


def parse_trackpoints(file_path):
    _, ext = os.path.splitext(file_path)
    ext = ext.lower()

    if ext == ".gpx":
        return _parse_gpx(file_path)
    elif ext == ".fit":
        return _parse_fit(file_path)
    else:
        raise ValueError(f"Unsupported file type: {ext}")


def _parse_gpx(file_path):
    import gpxpy

    with open(file_path) as f:
        gpx = gpxpy.parse(f)

    points = []
    track_name = None
    description = None
    extra = {}

    for track in gpx.tracks:
        if track.name and not track_name:
            track_name = track.name
        if track.description and not description:
            description = track.description
        if track.comment and not extra:
            try:
                cmt_data = json.loads(track.comment)
                data = cmt_data.get("activity_dict") or cmt_data
                hr_avg = data.get("average_heartrate")
                if hr_avg is not None:
                    extra["avg_heartrate"] = int(round(hr_avg))
                hr_max = data.get("max_heartrate")
                if hr_max is not None:
                    extra["max_heartrate"] = int(round(hr_max))
                extra["calories"] = data.get("calories")
                extra["moving_time_seconds"] = data.get("moving_time")
                extra["total_elevation_gain_m"] = data.get("total_elevation_gain")
                avg_speed = data.get("average_speed")
                if avg_speed is not None:
                    extra["avg_speed_kmh"] = round(avg_speed * 3.6, 2)
                extra["activity_type"] = cmt_data.get("type") or data.get("type")
            except (json.JSONDecodeError, TypeError):
                pass
        for seg in track.segments:
            for pt in seg.points:
                points.append((pt.latitude, pt.longitude, pt.elevation, pt.time))

    return {
        "points": points,
        "name": track_name or os.path.splitext(os.path.basename(file_path))[0],
        "description": description,
        "extra": extra,
    }


def _parse_fit(file_path):
    import fitparse

    fitfile = fitparse.FitFile(file_path)
    messages = list(fitfile.get_messages("record"))

    points = []
    track_name = os.path.splitext(os.path.basename(file_path))[0]
    extra = {}

    session_msgs = list(fitfile.get_messages("session"))
    for msg in session_msgs:
        for field in msg:
            if field.name == "sport" and field.value:
                track_name = str(field.value)
            elif field.name == "total_distance" and field.value:
                extra["distance_km"] = round(field.value / 1000, 2)
            elif field.name == "total_timer_time" and field.value:
                extra["moving_time_seconds"] = int(field.value)
            elif field.name == "total_elapsed_time" and field.value:
                extra.setdefault("moving_time_seconds", int(field.value))
            elif field.name == "total_ascent" and field.value:
                extra["total_elevation_gain_m"] = field.value
            elif field.name == "avg_heart_rate" and field.value:
                extra["avg_heartrate"] = int(round(field.value))
            elif field.name == "max_heart_rate" and field.value:
                extra["max_heartrate"] = int(round(field.value))
            elif field.name == "avg_speed" and field.value:
                extra["avg_speed_kmh"] = round(field.value * 3.6, 2)
            elif field.name == "total_calories" and field.value:
                extra["calories"] = int(field.value)

    for msg in messages:
        lat = None
        lon = None
        ele = None
        t = None
        for field in msg:
            if field.name == "position_lat":
                lat = field.value * (180.0 / (2**31)) if field.value else None
            elif field.name == "position_long":
                lon = field.value * (180.0 / (2**31)) if field.value else None
            elif field.name == "altitude":
                ele = field.value
            elif field.name == "timestamp":
                t = field.value.replace(tzinfo=dt_timezone.utc) if field.value else None
        if lat is not None and lon is not None:
            points.append((lat, lon, ele, t))

    return {
        "points": points,
        "name": track_name,
        "description": None,
        "extra": extra,
    }


def convert_fit_to_gpx(file_path):
    import gpxpy.gpx

    result = _parse_fit(file_path)
    points = result["points"]
    track_name = result["name"]
    gpx = gpxpy.gpx.GPX()
    gpx_track = gpxpy.gpx.GPXTrack(name=track_name)
    gpx.tracks.append(gpx_track)
    gpx_seg = gpxpy.gpx.GPXTrackSegment()
    gpx_track.segments.append(gpx_seg)

    for lat, lon, ele, t in points:
        gpx_seg.points.append(gpxpy.gpx.GPXTrackPoint(lat, lon, elevation=ele, time=t))

    tmp = tempfile.NamedTemporaryFile(mode="w", suffix=".gpx", delete=False)
    tmp.write(gpx.to_xml())
    tmp.close()
    return tmp.name


def import_trail_gpx(file_path, user_id, original_filename=None):
    user = User.objects.get(id=user_id)
    new_scrobbles = []

    result = parse_trackpoints(file_path)
    points = result["points"]
    track_name = result["name"]
    description = result.get("description")
    extra = result.get("extra", {})

    if not points:
        logger.warning(f"No trackpoints found in {file_path}")
        return []

    first_lat, first_lon, _, first_time = points[0]
    _, _, _, last_time = points[-1]

    if first_time is None:
        logger.warning(f"No timestamps in {file_path}")
        return []

    geo, _ = GeoLocation.objects.get_or_create(
        lat=round(first_lat, 6),
        lon=round(first_lon, 6),
        defaults={"altitude": None},
    )

    trail = Trail.find_by_trailhead(first_lat, first_lon, tolerance_m=100)
    if not trail:
        trail = Trail.find_or_create(track_name)
        trail.trailhead_location = geo
        trail.save(update_fields=["trailhead_location"])

    timestamp = first_time
    stop_timestamp = last_time

    existing = Scrobble.objects.filter(
        timestamp=timestamp,
        trail=trail,
        user=user,
    ).first()
    if existing:
        logger.debug(f"Skipping existing scrobble for trail {trail}")
        return []

    computed = compute_trail_stats(points)

    logdata = TrailLogData(
        description=description,
        distance_km=computed["distance_km"],
        elevation_gain_m=computed["elevation_gain_m"],
        moving_time_seconds=computed["moving_time_seconds"],
        activity_type=extra.get("activity_type"),
        avg_speed_kmh=computed["avg_speed_kmh"],
        avg_heartrate=extra.get("avg_heartrate"),
        max_heartrate=extra.get("max_heartrate"),
        calories=extra.get("calories"),
    )

    duration = int((stop_timestamp - timestamp).total_seconds()) if stop_timestamp else 0

    scrobble = Scrobble(
        user=user,
        timestamp=timestamp,
        stop_timestamp=stop_timestamp,
        playback_position_seconds=duration,
        source="GPX Import",
        trail=trail,
        log=logdata.asdict,
        timezone=user.profile.timezone or settings.TIME_ZONE,
        played_to_completion=True,
        in_progress=False,
        media_type=Scrobble.MediaType.TRAIL,
    )

    _, ext = os.path.splitext(file_path)
    if ext.lower() == ".fit":
        gpx_path = convert_fit_to_gpx(file_path)
        with open(gpx_path, "rb") as f:
            scrobble.gpx_file.save(
                f"{original_filename or 'trail'}.gpx",
                File(f),
                save=False,
            )
        os.unlink(gpx_path)
    else:
        with open(file_path, "rb") as f:
            scrobble.gpx_file.save(
                original_filename or os.path.basename(file_path),
                File(f),
                save=False,
            )

    new_scrobbles.append(scrobble)

    created = Scrobble.objects.bulk_create(new_scrobbles)
    logger.info(f"Created {len(created)} trail scrobbles")
    return created