from __future__ import annotations

import json
import logging
from datetime import date, datetime, timedelta
from typing import Any, Optional
from urllib.error import HTTPError, URLError
from urllib.parse import urlencode
from urllib.request import Request, urlopen

from app.core.config import Settings
from app.core.timezone import to_beijing_naive
from app.schemas.agent import SignalItem

logger = logging.getLogger(__name__)


class GitHubHotProjectClient:
    """Collects recently active, high-signal GitHub AI repositories."""

    endpoint = "https://api.github.com/search/repositories"

    def __init__(self, settings: Settings) -> None:
        self.settings = settings

    def collect_hot_projects(self, run_date: date) -> list[SignalItem]:
        # GitHub官方搜索提供开源项目热度候选，最终是否入选交给模型判断。
        since = run_date - timedelta(days=self.settings.github_recent_days)
        repositories: dict[str, dict[str, Any]] = {}
        for query in self._queries(since=since):
            payload = self._search(query)
            for repository in payload.get("items", []):
                html_url = repository.get("html_url")
                if isinstance(html_url, str):
                    repositories[html_url] = repository

        ranked = sorted(repositories.values(), key=lambda item: self._heat_score(item, run_date), reverse=True)
        projects = [self._to_signal_item(repository) for repository in ranked[: self.settings.github_max_projects]]
        logger.info(
            "github_hot_projects_collected days=%s min_stars=%s projects=%s",
            self.settings.github_recent_days,
            self.settings.github_min_stars,
            len(projects),
        )
        return projects

    def _queries(self, since: date) -> list[str]:
        # 查询集聚焦新近创建的AI项目，避免长期头部仓库挤占每日发现。
        since_text = since.isoformat()
        min_stars = self.settings.github_min_stars
        return [
            f"topic:llm created:>={since_text} stars:>={min_stars}",
            f"topic:ai-agent created:>={since_text} stars:>={min_stars}",
            f"topic:rag created:>={since_text} stars:>={min_stars}",
            f"llm in:name,description created:>={since_text} stars:>={min_stars}",
            f"llm agent in:name,description created:>={since_text} stars:>={min_stars}",
        ]

    def _search(self, query: str) -> dict[str, Any]:
        # GitHub REST搜索直接返回排序后的仓库元数据，便于后续模型研判。
        per_page = min(max(self.settings.github_max_projects * 2, 20), 100)
        params = {"q": query, "sort": "stars", "order": "desc", "per_page": str(per_page)}
        url = f"{self.endpoint}?{urlencode(params)}"
        request = Request(
            url,
            headers={
                "Accept": "application/vnd.github+json",
                "User-Agent": "SignalScout",
                "X-GitHub-Api-Version": "2022-11-28",
            },
        )
        try:
            with urlopen(request, timeout=20) as response:
                body = response.read().decode("utf-8")
        except HTTPError as exc:
            message = exc.read().decode("utf-8", errors="replace")
            raise RuntimeError(f"GitHub project search failed: HTTP {exc.code} {message}") from exc
        except URLError as exc:
            raise RuntimeError(f"GitHub project search failed: {exc.reason}") from exc
        return json.loads(body)

    def _to_signal_item(self, repository: dict[str, Any]) -> SignalItem:
        # 仓库元数据先标准化为信号候选，后续由模型统一筛选和改写摘要。
        full_name = str(repository.get("full_name") or repository.get("name") or "Unknown repository")
        description = str(repository.get("description") or "暂无项目描述")
        stars = int(repository.get("stargazers_count") or 0)
        forks = int(repository.get("forks_count") or 0)
        language = repository.get("language") or "未标注语言"
        created_at = self._parse_datetime(repository.get("created_at"))
        pushed_at = self._parse_datetime(repository.get("pushed_at"))
        freshness = created_at.date().isoformat() if created_at else "最近"
        summary = (
            f"{description} 该项目创建于 {freshness}，当前约 {stars} stars、{forks} forks，"
            f"主要语言为 {language}。"
        )
        return SignalItem(
            source_type="github",
            topic="GitHub 热门项目",
            title=full_name,
            summary=summary,
            source_url=str(repository["html_url"]),
            source_name="GitHub",
            published_at=created_at or pushed_at,
            importance=3,
            entities=[full_name, "GitHub", str(language)],
        )

    def _heat_score(self, repository: dict[str, Any], run_date: date) -> int:
        # Stars表示关注度，forks表示采用迹象，新项目获得额外新鲜度权重。
        stars = int(repository.get("stargazers_count") or 0)
        forks = int(repository.get("forks_count") or 0)
        created_at = self._parse_datetime(repository.get("created_at"))
        recency_bonus = 100 if created_at and created_at.date() >= run_date - timedelta(days=7) else 0
        return stars * 3 + forks + recency_bonus

    def _parse_datetime(self, value: Any) -> Optional[datetime]:
        # GitHub时间戳使用UTC ISO格式和Z后缀，入库前先换算为北京时间。
        if not isinstance(value, str):
            return None
        return to_beijing_naive(datetime.fromisoformat(value.replace("Z", "+00:00")))