import asyncio
import json
import logging
from datetime import datetime, timedelta
from typing import List, Optional
import dropbox
from modules.dropbox.client import dbx

# Logger
logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)

# Cache: key = folder_path, value = {"timestamp": datetime, "data": List[dict]}
_discourse_cache: dict[str, dict] = {}
CACHE_TTL = timedelta(hours=1)
FOLDER_PATH = "/_discourses"

async def fetch_discourses_from_dropbox() -> List[dict]:
    """
    Fetch all discourse JSONs for a scripture from Dropbox with caching.
    Expects files in "/_discourses/".
    """
    loop = asyncio.get_running_loop()
    folder_path = FOLDER_PATH

    # Check cache
    cache_entry = _discourse_cache.get(folder_path)
    if cache_entry:
        age = datetime.now() - cache_entry["timestamp"]
        if age < CACHE_TTL:
            logger.info(f"Using cached discourses for '{folder_path}' (age={age})")
            return cache_entry["data"]

    logger.info(f"Fetching discourses from Dropbox folder '{folder_path}'")
    discourses: List[dict] = []

    try:
        # List folder contents (synchronously in executor)
        res = await loop.run_in_executor(None, dbx.files_list_folder, folder_path)
        for entry in res.entries:
            if isinstance(entry, dropbox.files.FileMetadata) and entry.name.lower().endswith(".json"):
                metadata, fres = await loop.run_in_executor(
                    None, dbx.files_download, f"{folder_path}/{entry.name}"
                )
                data = fres.content.decode("utf-8")
                discourses.append(json.loads(data))

        # Update cache
        _discourse_cache[folder_path] = {"timestamp": datetime.now(), "data": discourses}
        logger.info(f"Cached {len(discourses)} discourses for '{folder_path}'")
        return discourses

    except Exception as e:
        logger.error(f"Error fetching discourses from '{folder_path}'", exc_info=e)
        # fallback to cached data if available
        if cache_entry:
            logger.warning(f"Returning stale cached discourses for '{folder_path}'")
            return cache_entry["data"]
        else:
            logger.warning(f"No cached discourses available for '{folder_path}'")
            return []


async def get_discourse_summaries(page: int = 1, per_page: int = 10):
    """
    Returns paginated summaries: id, topic_name, thumbnail_url.
    Sorted by topic_name.
    """
    all_discourses = await fetch_discourses_from_dropbox()

    # Build summaries
    summaries = [
        {
            "id": d.get("id"),
            "topic_name": d.get("topic_name"),
            "thumbnail_url": d.get("thumbnail_url"),
        }
        for d in all_discourses
    ]

    summaries.sort(key=lambda x: (x.get("topic_name") or "").lower())

    # Pagination
    total_items = len(summaries)
    total_pages = (total_items + per_page - 1) // per_page
    if page < 1 or page > total_pages:
        logger.warning(f"Invalid page {page}. Must be between 1 and {total_pages}")
        return {"page": page, "per_page": per_page, "total_pages": total_pages, "total_items": total_items, "data": []}

    start = (page - 1) * per_page
    end = start + per_page
    paginated = summaries[start:end]

    return {
        "page": page,
        "per_page": per_page,
        "total_pages": total_pages,
        "total_items": total_items,
        "data": paginated,
    }


async def get_discourse_by_id(topic_id: int) -> Optional[dict]:
    """
    Fetch a single discourse JSON by topic_id from Dropbox.
    Uses in-memory caching per file.
    """
    loop = asyncio.get_running_loop()
    file_path = f"{FOLDER_PATH}/{topic_id}.json"

    # Check cache
    cache_entry = _discourse_cache.get(file_path)
    if cache_entry:
        age = datetime.now() - cache_entry["timestamp"]
        if age < CACHE_TTL:
            logger.info(f"Using cached discourse for topic {topic_id} (age={age})")
            return cache_entry["data"]

    try:
        logger.info(f"Fetching discourse {topic_id} from Dropbox: {file_path}")
        metadata, res = await loop.run_in_executor(None, dbx.files_download, file_path)
        data = res.content.decode("utf-8")
        discourse = json.loads(data)

        # Update cache
        _discourse_cache[file_path] = {"timestamp": datetime.now(), "data": discourse}
        return discourse

    except dropbox.exceptions.HttpError as e:
        logger.error(f"Dropbox file not found: {file_path}", exc_info=e)
        return None
    except Exception as e:
        logger.error(f"Error fetching discourse {topic_id}", exc_info=e)
        # fallback to cached data if available
        if cache_entry:
            logger.warning(f"Returning stale cached discourse for topic {topic_id}")
            return cache_entry["data"]
        return None