import hmac
import hashlib
import logging
import threading

from flask import request, abort, Blueprint

from community_qa_bot.settings import (
    FORUM_WEBHOOK_SECRET,
    FORUM_API_USERNAME,
    TIDB_AI_API_KEY,
    TIDB_AI_FORUM_CHAT_ENGINE,
)
from community_qa_bot.pingcap_qa_service import CommunityQAService
from .discourse_api import reply_to_topic, get_posts_of_topic

logger = logging.getLogger(__name__)

qa_service = CommunityQAService(
    api_key=TIDB_AI_API_KEY,
    chat_engine=TIDB_AI_FORUM_CHAT_ENGINE,
)

forum_bp = Blueprint('forum', __name__)


def is_valid_discourse_webhook_request(payload, signature):
    if not (payload and signature):
        return False
    mac = hmac.new(FORUM_WEBHOOK_SECRET.encode('utf-8'), msg=payload, digestmod=hashlib.sha256)
    return hmac.compare_digest(mac.hexdigest(), signature.split('=')[1])


@forum_bp.route('/discourse-webhook', methods=['POST'])
def discourse_webhook():
    event_name = request.headers.get('X-Discourse-Event')
    signature = request.headers.get('X-Discourse-Event-Signature')
    
    if not is_valid_discourse_webhook_request(request.data, signature):
        abort(403)

    logger.debug(f'event_name: {event_name}, payload: {request.data}')

    if event_name == 'post_created':
        threading.Thread(target=handle_post_created, args=(request.json,)).start()

    return 'ok'


def build_qa_context_for_post_created(topic_id, post_id):
    qa_context = []
    skip = True
    posts = get_posts_of_topic(topic_id, post_id)
    if not posts:
        return qa_context, skip

    # Other users reply to the topic, ignore it
    if posts['participant_count'] != 2:
        return qa_context, skip
    
    for post in posts['post_stream']['posts']:
        if post['username'] == FORUM_API_USERNAME:
            qa_context.append({
                'role': 'assistant',
                'content': post['cooked']
            })
        else:
            qa_context.append({
                'role': 'user',
                'content': post['cooked']
            })
    qa_context = qa_context[-5:]
    if not qa_context or qa_context[-1]['role'] == 'assistant':
        skip = True
    else:
        skip = False
    return qa_context, skip


def handle_post_created(payload):
    logger.debug(f'handle_post_created: {payload}')
    post = payload['post']
    post_id = post['id']
    topic_id = post['topic_id']
    username = post['username']
    if post['post_number'] == 1:
        return handle_topic_created(payload)

    # Ignore the posts created by the bot itself
    if post['username'] == FORUM_API_USERNAME:
        return

    qa_context, skip = build_qa_context_for_post_created(topic_id, post_id)
    if skip:
        return

    answer, _, _ = qa_service.ask(origin="forum", qa_context=qa_context)
    if answer:
        return reply_to_topic(topic_id, answer)


def build_qa_context_for_topic_created(title, body):
    return [{
        'role': 'user',
        'content': f'title: {title}\n {body}'
    }]


def handle_topic_created(payload):
    logger.debug(f'handle_topic_created: {payload}')
    post = payload['post']
    post_id = post['id']
    username = post['username']
    topic_id = post['topic_id']
    topic_title = post['topic_title']
    topic_body = post['raw']
    answer, _, _ = qa_service.ask(
        origin="forum",
        qa_context=build_qa_context_for_topic_created(topic_title, topic_body),
    )
    if answer:
        return reply_to_topic(topic_id, answer)