#!/usr/bin/env python3
"""Satellite tile downloader for GPS-denied navigation.

Downloads Web Mercator satellite tiles for a given bounding box and stores
them in the standard z/x/y.png directory layout expected by SatelliteDataManager.

Usage:
    # Dry run (count tiles only)
    python scripts/download_tiles.py --lat-min 48.5 --lat-max 49.5 --lon-min 31.5 --lon-max 32.5 --dry-run

    # Download from OpenStreetMap (default, no API key)
    python scripts/download_tiles.py --lat-min 48.5 --lat-max 49.5 --lon-min 31.5 --lon-max 32.5

    # Custom zoom and output dir
    python scripts/download_tiles.py --lat-min 49.0 --lat-max 49.1 --lon-min 32.0 --lon-max 32.1 \
        --zoom 18 --output .satellite_tiles

    # Google Maps provider (requires API key)
    python scripts/download_tiles.py --lat-min 49.0 --lat-max 49.1 --lon-min 32.0 --lon-max 32.1 \
        --provider google --api-key YOUR_KEY
"""

from __future__ import annotations

import argparse
import asyncio
import os
import sys
import time

sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "src"))


from gps_denied.schemas.satellite import TileCoords
from gps_denied.utils.mercator import latlon_to_tile

# Tile provider URL templates
_PROVIDERS = {
    "osm": "https://tile.openstreetmap.org/{z}/{x}/{y}.png",
    "google": (
        "https://maps.googleapis.com/maps/api/staticmap"
        "?center={lat},{lon}&zoom={z}&size=256x256&maptype=satellite&key={api_key}"
    ),
}

_USER_AGENT = "GPS-Denied-Onboard/1.0 (tile prefetch)"


def compute_tile_range(
    lat_min: float, lat_max: float, lon_min: float, lon_max: float, zoom: int
) -> list[TileCoords]:
    """Compute all tile coordinates within a lat/lon bounding box."""
    nw = latlon_to_tile(lat_max, lon_min, zoom)  # NW corner
    se = latlon_to_tile(lat_min, lon_max, zoom)   # SE corner
    tiles: list[TileCoords] = []
    for x in range(nw.x, se.x + 1):
        for y in range(nw.y, se.y + 1):
            tiles.append(TileCoords(x=x, y=y, zoom=zoom))
    return tiles


async def download_tiles(
    tiles: list[TileCoords],
    output_dir: str,
    provider: str = "osm",
    api_key: str = "",
    max_concurrent: int = 4,
    delay_s: float = 0.1,
) -> tuple[int, int]:
    """Download tiles concurrently. Returns (success_count, error_count)."""
    try:
        import httpx
    except ImportError:
        print("ERROR: httpx required. Install: pip install httpx")
        return 0, len(tiles)

    url_template = _PROVIDERS.get(provider, _PROVIDERS["osm"])
    semaphore = asyncio.Semaphore(max_concurrent)
    success = 0
    errors = 0

    async def fetch_one(client: httpx.AsyncClient, tc: TileCoords) -> bool:
        nonlocal success, errors
        out_path = os.path.join(output_dir, str(tc.zoom), str(tc.x), f"{tc.y}.png")
        if os.path.isfile(out_path):
            success += 1
            return True

        if provider == "google":
            from gps_denied.utils.mercator import tile_to_latlon
            center = tile_to_latlon(tc.x + 0.5, tc.y + 0.5, tc.zoom)
            url = url_template.format(
                z=tc.zoom, x=tc.x, y=tc.y,
                lat=center.lat, lon=center.lon, api_key=api_key,
            )
        else:
            url = url_template.format(z=tc.zoom, x=tc.x, y=tc.y)

        async with semaphore:
            try:
                resp = await client.get(url)
                resp.raise_for_status()
                os.makedirs(os.path.dirname(out_path), exist_ok=True)
                with open(out_path, "wb") as f:
                    f.write(resp.content)
                success += 1
                await asyncio.sleep(delay_s)
                return True
            except Exception as exc:
                errors += 1
                print(f"  FAIL {tc.zoom}/{tc.x}/{tc.y}: {exc}")
                return False

    async with httpx.AsyncClient(
        timeout=30.0,
        headers={"User-Agent": _USER_AGENT},
        follow_redirects=True,
    ) as client:
        tasks = [fetch_one(client, tc) for tc in tiles]
        await asyncio.gather(*tasks)

    return success, errors


def main() -> int:
    parser = argparse.ArgumentParser(description="Download satellite tiles for GPS-denied navigation")
    parser.add_argument("--lat-min", type=float, required=True)
    parser.add_argument("--lat-max", type=float, required=True)
    parser.add_argument("--lon-min", type=float, required=True)
    parser.add_argument("--lon-max", type=float, required=True)
    parser.add_argument("--zoom", type=int, default=18)
    parser.add_argument("--output", default=".satellite_tiles", help="Output directory")
    parser.add_argument("--provider", choices=["osm", "google"], default="osm")
    parser.add_argument("--api-key", default="", help="API key (for google provider)")
    parser.add_argument("--max-concurrent", type=int, default=4)
    parser.add_argument("--dry-run", action="store_true", help="Only count tiles, don't download")
    args = parser.parse_args()

    tiles = compute_tile_range(args.lat_min, args.lat_max, args.lon_min, args.lon_max, args.zoom)

    # Estimate size: ~30KB per tile
    est_mb = len(tiles) * 30 / 1024
    print(f"Tiles: {len(tiles)} at zoom {args.zoom}")
    print(f"Bounding box: ({args.lat_min}, {args.lon_min}) → ({args.lat_max}, {args.lon_max})")
    print(f"Estimated size: ~{est_mb:.1f} MB")
    print(f"Output: {args.output}")

    if args.dry_run:
        print("\n--dry-run: no tiles downloaded.")
        return 0

    t0 = time.time()
    ok, err = asyncio.run(download_tiles(
        tiles, args.output,
        provider=args.provider, api_key=args.api_key,
        max_concurrent=args.max_concurrent,
    ))
    elapsed = time.time() - t0

    print(f"\nDone in {elapsed:.1f}s: {ok} downloaded, {err} errors")
    return 1 if err > 0 else 0


if __name__ == "__main__":
    sys.exit(main())