"""Download Sentinel-2 cloudless satellite tiles into a local PMTiles archive."""

from __future__ import annotations

import argparse
import email.utils
import http.client
import math
import sqlite3
import subprocess
import tempfile
import threading
import time
import urllib.error
import urllib.parse
import urllib.request
from concurrent.futures import FIRST_COMPLETED, Future, ThreadPoolExecutor, wait
from dataclasses import dataclass
from datetime import datetime, timezone
from pathlib import Path

from pipeline.download.tiles import ensure_pmtiles_cli
from pipeline.local_temp import local_tmp_dir

DEFAULT_TILE_URL = (
    "https://tiles.maps.eox.at/wmts/1.0.0/s2cloudless_3857/default/"
    "GoogleMapsCompatible/{z}/{y}/{x}.jpg"
)
DEFAULT_BBOX = (-10.5, 49.0, 5.0, 61.0)
DEFAULT_MIN_ZOOM = 5
DEFAULT_MAX_ZOOM = 13
DEFAULT_RETRY_COOLDOWN = 15.0
USER_AGENT = "perfect-postcode-satellite-tiles/1.0"
RETRYABLE_HTTP_STATUS = {408, 429, 500, 502, 503, 504}
ATTRIBUTION = (
    "Sentinel-2 cloudless - https://s2maps.eu by EOX IT Services GmbH "
    "(Contains modified Copernicus Sentinel data 2024)"
)


@dataclass(frozen=True)
class Tile:
    zoom: int
    x: int
    y: int


class _DownloadThrottle:
    def __init__(self, min_request_interval: float) -> None:
        self._min_request_interval = max(0.0, min_request_interval)
        self._next_request_at = 0.0
        self._lock = threading.Lock()

    def wait(self) -> None:
        while True:
            with self._lock:
                now = time.monotonic()
                wait_for = self._next_request_at - now
                if wait_for <= 0:
                    if self._min_request_interval:
                        self._next_request_at = now + self._min_request_interval
                    return

            time.sleep(min(wait_for, 1.0))

    def defer(self, delay: float) -> bool:
        if delay <= 0:
            return False

        target = time.monotonic() + delay
        with self._lock:
            should_announce = target > self._next_request_at + 1.0
            self._next_request_at = max(self._next_request_at, target)
            return should_announce


def _lonlat_to_tile(lon: float, lat: float, zoom: int) -> tuple[int, int]:
    lat = max(min(lat, 85.05112878), -85.05112878)
    n = 1 << zoom
    x = int(math.floor((lon + 180.0) / 360.0 * n))
    y = int(
        math.floor((1.0 - math.asinh(math.tan(math.radians(lat))) / math.pi) / 2.0 * n)
    )
    return min(max(x, 0), n - 1), min(max(y, 0), n - 1)


def _tile_ranges(
    bbox: tuple[float, float, float, float], zoom: int
) -> tuple[range, range]:
    west, south, east, north = bbox
    min_x, min_y = _lonlat_to_tile(west, north, zoom)
    max_x, max_y = _lonlat_to_tile(east, south, zoom)
    return range(min_x, max_x + 1), range(min_y, max_y + 1)


def _iter_tiles(
    bbox: tuple[float, float, float, float], min_zoom: int, max_zoom: int
):
    for zoom in range(min_zoom, max_zoom + 1):
        x_range, y_range = _tile_ranges(bbox, zoom)
        for x in x_range:
            for y in y_range:
                yield Tile(zoom=zoom, x=x, y=y)


def _tile_count(
    bbox: tuple[float, float, float, float], min_zoom: int, max_zoom: int
) -> int:
    count = 0
    for zoom in range(min_zoom, max_zoom + 1):
        x_range, y_range = _tile_ranges(bbox, zoom)
        count += len(x_range) * len(y_range)
    return count


def _is_eox_tile_url(url: str) -> bool:
    host = urllib.parse.urlparse(url).hostname or ""
    return host == "tiles.maps.eox.at" or host.endswith(".tiles.maps.eox.at")


def _retry_after_seconds(headers) -> float | None:
    raw = None
    if headers is not None:
        raw = headers.get("retry-after") or headers.get("Retry-After")
    if not raw:
        return None

    try:
        return max(0.0, float(raw))
    except ValueError:
        pass

    try:
        retry_at = email.utils.parsedate_to_datetime(raw)
    except (TypeError, ValueError):
        return None

    if retry_at.tzinfo is None:
        retry_at = retry_at.replace(tzinfo=timezone.utc)
    return max(0.0, (retry_at - datetime.now(timezone.utc)).total_seconds())


def _http_retry_delay(
    err: urllib.error.HTTPError,
    url: str,
    attempt: int,
    retry_cooldown: float,
) -> float | None:
    if err.code in {204, 404}:
        return None

    retry_after = _retry_after_seconds(err.headers)
    if retry_after is not None:
        return retry_after

    if err.code == 403 and _is_eox_tile_url(url):
        return retry_cooldown

    if err.code in RETRYABLE_HTTP_STATUS:
        return min(2.0, 0.25 * (2**attempt))

    return None


def _fetch_tile(
    tile: Tile,
    source_url: str,
    timeout: float,
    retries: int,
    throttle: _DownloadThrottle,
    retry_cooldown: float,
) -> tuple[Tile, bytes | None]:
    url = source_url.format(z=tile.zoom, x=tile.x, y=tile.y)
    last_error: Exception | None = None

    for attempt in range(retries + 1):
        try:
            throttle.wait()
            req = urllib.request.Request(url, headers={"User-Agent": USER_AGENT})
            with urllib.request.urlopen(req, timeout=timeout) as response:
                content_type = response.headers.get("content-type", "")
                data = response.read()
                if not data:
                    return tile, None
                if not content_type.lower().startswith("image/"):
                    raise RuntimeError(
                        f"Unexpected content type for {url}: {content_type or 'unknown'}"
                    )
                return tile, data
        except urllib.error.HTTPError as err:
            if err.code in {204, 404}:
                return tile, None
            retry_delay = _http_retry_delay(err, url, attempt, retry_cooldown)
            if retry_delay is None:
                raise RuntimeError(
                    f"Failed to download satellite tile {url}: {err}"
                ) from err
            last_error = err
        except (
            TimeoutError,
            urllib.error.URLError,
            ConnectionError,
            http.client.HTTPException,
            RuntimeError,
        ) as err:
            last_error = err
            retry_delay = min(2.0, 0.25 * (2**attempt))

        if attempt < retries:
            if throttle.defer(retry_delay) and retry_delay >= 5.0:
                print(
                    f"Satellite tile source returned {last_error}; "
                    f"pausing downloads for {retry_delay:.0f}s before retrying",
                    flush=True,
                )

    assert last_error is not None
    raise RuntimeError(f"Failed to download satellite tile {url}: {last_error}") from last_error


def _create_mbtiles(
    mbtiles_path: Path,
    bbox: tuple[float, float, float, float],
    min_zoom: int,
    max_zoom: int,
    source_url: str,
    max_workers: int,
    timeout: float,
    retries: int,
    retry_cooldown: float,
    min_request_interval: float,
) -> int:
    if mbtiles_path.exists():
        mbtiles_path.unlink()

    conn = sqlite3.connect(mbtiles_path)
    conn.execute("PRAGMA journal_mode = WAL")
    conn.execute("PRAGMA synchronous = NORMAL")
    conn.execute("CREATE TABLE metadata (name TEXT, value TEXT)")
    conn.execute(
        "CREATE TABLE tiles (zoom_level INTEGER, tile_column INTEGER, "
        "tile_row INTEGER, tile_data BLOB)"
    )
    conn.execute(
        "CREATE UNIQUE INDEX tile_index ON tiles (zoom_level, tile_column, tile_row)"
    )
    conn.executemany(
        "INSERT INTO metadata (name, value) VALUES (?, ?)",
        [
            ("name", "Sentinel-2 cloudless satellite basemap"),
            ("type", "baselayer"),
            ("version", "1"),
            ("description", "Sentinel-2 cloudless Web Mercator satellite imagery"),
            ("format", "jpg"),
            ("attribution", ATTRIBUTION),
            ("bounds", ",".join(f"{value:.6f}" for value in bbox)),
            ("minzoom", str(min_zoom)),
            ("maxzoom", str(max_zoom)),
        ],
    )

    total = _tile_count(bbox, min_zoom, max_zoom)
    inserted = 0
    completed = 0
    submitted = 0
    tiles = iter(_iter_tiles(bbox, min_zoom, max_zoom))
    pending: set[Future[tuple[Tile, bytes | None]]] = set()
    queue_size = max_workers * 4
    throttle = _DownloadThrottle(min_request_interval=min_request_interval)

    def submit_next(executor: ThreadPoolExecutor) -> bool:
        nonlocal submitted
        try:
            tile = next(tiles)
        except StopIteration:
            return False
        pending.add(
            executor.submit(
                _fetch_tile,
                tile,
                source_url,
                timeout,
                retries,
                throttle,
                retry_cooldown,
            )
        )
        submitted += 1
        return True

    try:
        with ThreadPoolExecutor(max_workers=max_workers) as executor:
            for _ in range(queue_size):
                if not submit_next(executor):
                    break

            while pending:
                done, pending = wait(pending, return_when=FIRST_COMPLETED)
                for future in done:
                    tile, tile_data = future.result()
                    completed += 1
                    if tile_data is not None:
                        tms_y = (1 << tile.zoom) - 1 - tile.y
                        conn.execute(
                            "INSERT OR REPLACE INTO tiles VALUES (?, ?, ?, ?)",
                            (tile.zoom, tile.x, tms_y, tile_data),
                        )
                        inserted += 1

                    submit_next(executor)

                    if completed % 1000 == 0 or completed == total:
                        conn.commit()
                        print(
                            f"Downloaded {completed:,}/{total:,} satellite tiles "
                            f"({inserted:,} stored)",
                            flush=True,
                        )
    finally:
        conn.commit()
        conn.close()

    return inserted


def build_satellite_tiles(
    output_path: Path,
    pmtiles_bin: Path,
    pmtiles_version: str,
    bbox: tuple[float, float, float, float],
    min_zoom: int,
    max_zoom: int,
    source_url: str,
    max_workers: int,
    timeout: float,
    retries: int,
    retry_cooldown: float,
    min_request_interval: float,
) -> None:
    if min_zoom > max_zoom:
        raise ValueError("--min-zoom must be <= --max-zoom")
    if len(bbox) != 4 or bbox[0] >= bbox[2] or bbox[1] >= bbox[3]:
        raise ValueError("--bbox must be west,south,east,north")

    output_path.parent.mkdir(parents=True, exist_ok=True)
    ensure_pmtiles_cli(pmtiles_bin, pmtiles_version)

    with tempfile.TemporaryDirectory(dir=local_tmp_dir()) as tmp:
        mbtiles_path = Path(tmp) / "satellite.mbtiles"
        tile_count = _create_mbtiles(
            mbtiles_path=mbtiles_path,
            bbox=bbox,
            min_zoom=min_zoom,
            max_zoom=max_zoom,
            source_url=source_url,
            max_workers=max_workers,
            timeout=timeout,
            retries=retries,
            retry_cooldown=retry_cooldown,
            min_request_interval=min_request_interval,
        )
        if tile_count == 0:
            raise RuntimeError("Satellite tile download produced no tiles")

        subprocess.run(
            [
                str(pmtiles_bin),
                "convert",
                str(mbtiles_path),
                str(output_path),
                "--force",
            ],
            check=True,
        )

    size_mb = output_path.stat().st_size / (1024 * 1024)
    print(f"Wrote {output_path} ({size_mb:.1f} MB)", flush=True)


def _parse_bbox(raw: str) -> tuple[float, float, float, float]:
    parts = [float(part.strip()) for part in raw.split(",")]
    if len(parts) != 4:
        raise argparse.ArgumentTypeError("bbox must contain four comma-separated numbers")
    return parts[0], parts[1], parts[2], parts[3]


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--output", type=Path, required=True)
    parser.add_argument(
        "--pmtiles-bin", type=Path, default=Path("property-data/pmtiles")
    )
    parser.add_argument("--pmtiles-version", default="1.22.3")
    parser.add_argument("--bbox", type=_parse_bbox, default=DEFAULT_BBOX)
    parser.add_argument("--min-zoom", type=int, default=DEFAULT_MIN_ZOOM)
    parser.add_argument("--max-zoom", type=int, default=DEFAULT_MAX_ZOOM)
    parser.add_argument("--source-url", default=DEFAULT_TILE_URL)
    parser.add_argument("--max-workers", type=int, default=8)
    parser.add_argument("--timeout", type=float, default=20.0)
    parser.add_argument("--retries", type=int, default=3)
    parser.add_argument(
        "--retry-cooldown",
        type=float,
        default=DEFAULT_RETRY_COOLDOWN,
        help="Seconds to pause all workers after an EOX rate-limit response",
    )
    parser.add_argument(
        "--min-request-interval",
        type=float,
        default=0.0,
        help="Minimum seconds between tile requests across all workers",
    )
    args = parser.parse_args()

    build_satellite_tiles(
        output_path=args.output,
        pmtiles_bin=args.pmtiles_bin,
        pmtiles_version=args.pmtiles_version,
        bbox=args.bbox,
        min_zoom=args.min_zoom,
        max_zoom=args.max_zoom,
        source_url=args.source_url,
        max_workers=max(1, args.max_workers),
        timeout=args.timeout,
        retries=max(0, args.retries),
        retry_cooldown=max(0.0, args.retry_cooldown),
        min_request_interval=max(0.0, args.min_request_interval),
    )


if __name__ == "__main__":
    main()