import json
import os
import re
import hashlib
from datetime import datetime


class ScraperError(Exception):
    def __init__(self, station, code, message, url=None, status_code=None):
        self.station = station
        self.code = code
        self.url = url
        self.status_code = status_code
        details = f"[{code}] {message}"
        if status_code is not None:
            details += f" (HTTP {status_code})"
        if url:
            details += f" URL: {url}"
        super().__init__(details)


def save_response_snapshot(station, code, url, content, status_code=None):
    directory = os.path.join("data", "diagnostics")
    try:
        os.makedirs(directory, exist_ok=True)
        digest = hashlib.sha256(f"{station}:{code}:{url}".encode("utf-8")).hexdigest()[:16]
        safe_station = re.sub(r"[^a-zA-Z0-9_-]", "_", station)
        base_path = os.path.join(directory, f"{safe_station}-{code}-{digest}")

        with open(f"{base_path}.json", "w", encoding="utf-8") as metadata_file:
            json.dump({"station": station, "code": code, "url": url, "status_code": status_code,
                       "updated_at": datetime.now().isoformat()}, metadata_file, ensure_ascii=False, indent=2)
        with open(f"{base_path}.html", "w", encoding="utf-8") as response_file:
            response_file.write((content or "")[:2_000_000])
        return base_path
    except OSError as exc:
        return f"snapshot unavailable: {exc}"


def invalid_response(station, code, message, url, response=None, content=None):
    snapshot = save_response_snapshot(
        station,
        url,
        response.text if response is not None else content,
        response.status_code if response is not None else None,
    )
    raise ScraperError(station, code, f"{message}. Snapshot: {snapshot}", url,
                       response.status_code if response is not None else None)