"""Mastodon public API client — no authentication required."""

import logging
import re
import time
from html import unescape
from typing import Optional
from urllib.parse import urljoin

import requests

logger = logging.getLogger(__name__)

# Respect rate limits: Mastodon returns 300 requests per 5 min by default
DEFAULT_TIMEOUT = 30
MAX_RETRIES = 3
RETRY_BACKOFF = 5  # seconds


class MastodonAPIError(Exception):
    pass


class RateLimitError(MastodonAPIError):
    def __init__(self, retry_after: float = 60):
        self.retry_after = retry_after
        super().__init__(f"Rate limited, retry after {retry_after}s")


def _strip_html(html: str) -> str:
    """Strip HTML tags and decode entities to get plain text."""
    # Replace <br> and </p> with newlines
    text = re.sub(r"<br\s*/?>", "\n", html)
    text = re.sub(r"</p>", "\n", text)
    # Remove all remaining tags
    text = re.sub(r"<[^>]+>", "", text)
    return unescape(text).strip()


def _api_get(instance: str, path: str, params: Optional[dict] = None) -> requests.Response:
    """Make a GET request to a Mastodon instance's public API."""
    url = f"https://{instance}{path}"
    headers = {"Accept": "application/json", "User-Agent": "MastodonCollector/1.0"}

    for attempt in range(MAX_RETRIES):
        try:
            resp = requests.get(url, params=params, headers=headers, timeout=DEFAULT_TIMEOUT)

            if resp.status_code == 429:
                retry_after = float(resp.headers.get("X-RateLimit-Reset", 60))
                # If it's an ISO timestamp, calculate delta
                if retry_after > 1_000_000:
                    retry_after = 60
                logger.warning("Rate limited by %s, waiting %.0fs", instance, retry_after)
                raise RateLimitError(retry_after)

            if resp.status_code == 404:
                raise MastodonAPIError(f"Not found: {url}")

            resp.raise_for_status()
            return resp

        except RateLimitError:
            raise
        except requests.RequestException as e:
            if attempt < MAX_RETRIES - 1:
                wait = RETRY_BACKOFF * (attempt + 1)
                logger.warning("Request to %s failed (attempt %d/%d): %s — retrying in %ds",
                               url, attempt + 1, MAX_RETRIES, e, wait)
                time.sleep(wait)
            else:
                raise MastodonAPIError(f"Failed after {MAX_RETRIES} attempts: {e}") from e

    raise MastodonAPIError("Unexpected retry exhaustion")


def lookup_account(instance: str, username: str) -> dict:
    """Look up an account on an instance by username. Returns the account JSON."""
    # Try the v1 lookup endpoint first (available on most instances)
    try:
        resp = _api_get(instance, "/api/v1/accounts/lookup", {"acct": username})
        return resp.json()
    except MastodonAPIError:
        pass

    # Fallback: search for the account
    resp = _api_get(instance, "/api/v2/search", {"q": f"@{username}@{instance}", "type": "accounts", "limit": 1})
    data = resp.json()
    accounts = data.get("accounts", [])
    if not accounts:
        raise MastodonAPIError(f"Account @{username} not found on {instance}")
    return accounts[0]


def get_account_statuses(
    instance: str,
    account_id: str,
    since_id: Optional[str] = None,
    limit: int = 40,
    exclude_reblogs: bool = False,
) -> list[dict]:
    """
    Fetch statuses from an account. Handles pagination to get all new statuses.
    Returns list of status dicts, oldest first.
    """
    all_statuses = []
    params = {"limit": min(limit, 40)}
    if since_id:
        params["since_id"] = since_id
    if exclude_reblogs:
        params["exclude_reblogs"] = "true"

    path = f"/api/v1/accounts/{account_id}/statuses"

    # Paginate through results
    max_pages = 25  # safety limit
    page = 0

    while page < max_pages:
        resp = _api_get(instance, path, params)
        statuses = resp.json()

        if not statuses:
            break

        all_statuses.extend(statuses)
        page += 1

        # Check Link header for next page
        link_header = resp.headers.get("Link", "")
        next_match = re.search(r'<([^>]+)>;\s*rel="next"', link_header)
        if not next_match:
            break

        # Parse the next URL for max_id
        next_url = next_match.group(1)
        max_id_match = re.search(r"max_id=(\d+)", next_url)
        if not max_id_match:
            break

        params["max_id"] = max_id_match.group(1)
        # Remove since_id for subsequent pages — we're paginating backwards
        # Actually we keep since_id as the floor
        time.sleep(0.5)  # Be polite between pages

    # Return oldest first so we can process chronologically
    all_statuses.reverse()
    return all_statuses


def get_status_context(instance: str, status_id: str) -> dict:
    """Get the context (ancestors + descendants) of a status. Useful for threading."""
    resp = _api_get(instance, f"/api/v1/statuses/{status_id}/context")
    return resp.json()


def classify_status(status: dict, monitored_account_id: str) -> str:
    """
    Classify a status as: post, reply, mention, or reblog.
    - reblog: the status is a boost of another status
    - reply: the status is in reply to another status
    - mention: the status mentions other accounts (but is not a reply)
    - post: a standalone original post
    """
    if status.get("reblog"):
        return "reblog"
    if status.get("in_reply_to_id"):
        return "reply"
    mentions = status.get("mentions", [])
    if mentions:
        # Only classify as "mention" if it mentions someone other than self
        other_mentions = [m for m in mentions if m.get("id") != monitored_account_id]
        if other_mentions:
            return "mention"
    return "post"


def parse_status(status: dict, monitored_account_id: str) -> dict:
    """Parse a raw Mastodon status JSON into a flat dict for storage."""
    # If it's a reblog, we store the original content but flag it
    actual = status.get("reblog") or status
    content_html = actual.get("content", "")

    return {
        "status_id": status["id"],
        "uri": status.get("uri", ""),
        "url": status.get("url") or actual.get("url", ""),
        "content": content_html,
        "text_content": _strip_html(content_html),
        "visibility": status.get("visibility", "public"),
        "created_at": status.get("created_at"),
        "language": status.get("language") or actual.get("language"),
        "sensitive": status.get("sensitive", False),
        "spoiler_text": status.get("spoiler_text", ""),
        "in_reply_to_id": status.get("in_reply_to_id"),
        "in_reply_to_account_id": status.get("in_reply_to_account_id"),
        "conversation_id": status.get("conversation", {}).get("id") if isinstance(status.get("conversation"), dict) else None,
        "replies_count": status.get("replies_count", 0),
        "reblogs_count": status.get("reblogs_count", 0),
        "favourites_count": status.get("favourites_count", 0),
        "status_type": classify_status(status, monitored_account_id),
        "mentions": [
            {
                "mentioned_account_id": m.get("id"),
                "mentioned_username": m.get("username", ""),
                "mentioned_acct": m.get("acct", ""),
                "mentioned_url": m.get("url", ""),
            }
            for m in (actual.get("mentions") or [])
        ],
        "media_attachments": [
            {
                "media_id": ma.get("id"),
                "media_type": ma.get("type"),
                "url": ma.get("url"),
                "preview_url": ma.get("preview_url"),
                "description": ma.get("description"),
            }
            for ma in (actual.get("media_attachments") or [])
        ],
        "tags": [
            {"name": t.get("name", ""), "url": t.get("url", "")}
            for t in (actual.get("tags") or [])
        ],
        "raw_json": status,
    }