"""Pre-bake per-handle GPS tracks for the Explore page.

Reads all activity GeoJSON files for a handle, applies RDP simplification,
and writes a single tracks.json for fast client-side heatmap rendering.
"""
from __future__ import annotations

import json
import time
from pathlib import Path

from bincio.extract.simplify import _rdp_mask

_VERSION     = 1
_RDP_EPSILON = 0.0001   # ~10 m on the ground


_SPORT_MAP: dict[str, str] = {
    "cycling": "cycling", "road_cycling": "cycling", "gravel_cycling": "cycling",
    "mountain_biking": "cycling", "e_biking": "cycling", "indoor_cycling": "cycling",
    "biking": "cycling", "bike": "cycling", "ride": "cycling",
    "running": "running", "trail_running": "running", "treadmill_running": "running",
    "jogging": "running",
    "hiking": "hiking", "walking": "hiking", "trekking": "hiking",
    "mountaineering": "hiking",
    "skiing": "skiing", "cross_country_skiing": "skiing", "alpine_skiing": "skiing",
    "snowboarding": "skiing",
}


def _sport_to_type(sport: str | None) -> str:
    if not sport:
        return "other"
    return _SPORT_MAP.get(sport.lower(), "other")


def bake_tracks(handle: str, data_dir: Path) -> int:
    """Build tracks.json for handle. Returns number of tracks included."""
    acts_dir = data_dir / handle / "activities"
    if not acts_dir.exists():
        return 0

    tracks = []
    for gj_path in sorted(acts_dir.glob("*.geojson")):
        act_id = gj_path.stem

        meta: dict = {}
        meta_path = acts_dir / f"{act_id}.json"
        if meta_path.exists():
            try:
                meta = json.loads(meta_path.read_text(encoding="utf-8"))
            except (OSError, json.JSONDecodeError):
                pass

        if meta.get("virtual"):
            continue

        try:
            gj = json.loads(gj_path.read_text(encoding="utf-8"))
        except (OSError, json.JSONDecodeError):
            continue

        raw_coords = gj.get("geometry", {}).get("coordinates") or []
        if len(raw_coords) < 2:
            continue

        lng_lat = [[float(c[0]), float(c[1])] for c in raw_coords if len(c) >= 2]
        if len(lng_lat) < 2:
            continue

        mask = _rdp_mask(lng_lat, epsilon=_RDP_EPSILON)
        simplified = [pt for pt, keep in zip(lng_lat, mask) if keep]
        if len(simplified) < 2:
            continue

        tracks.append({
            "id":     act_id,
            "date":   (meta.get("started_at") or "")[:10],
            "type":   _sport_to_type(meta.get("sport")),
            "name":   meta.get("title") or act_id,
            "dist":   int(meta.get("distance_m") or 0),
            "coords": simplified,
        })

    tracks.sort(key=lambda t: t["date"], reverse=True)

    out = data_dir / handle / "tracks.json"
    out.write_text(
        json.dumps({
            "v":            _VERSION,
            "handle":       handle,
            "generated_at": int(time.time()),
            "tracks":       tracks,
        }),
        encoding="utf-8",
    )
    return len(tracks)