#!/usr/bin/env python3
"""
patch_web_search_fallback.py — DuckDuckGo 免费 fallback

当所有付费搜索后端（Firecrawl / Tavily / Exa / Parallel）都不可用时，
自动 fallback 到 DuckDuckGo 搜索，无需任何 API key。

Monkey-patch 目标（tools/web_tools.py）：
  - _get_backend()        : 无可用后端时返回 "duckduckgo"
  - web_search_tool()     : 分发 duckduckgo 后端
  - _is_backend_available(): duckduckgo 始终返回 True
"""

import json
import logging

logger = logging.getLogger(__name__)


def _ddg_search(query: str, limit: int = 5) -> dict:
    """通过 DuckDuckGo 搜索，返回标准格式结果。"""
    try:
        from duckduckgo_search import DDGS

        results = []
        with DDGS() as ddgs:
            for i, r in enumerate(ddgs.text(query, max_results=limit)):
                results.append({
                    "title": r.get("title", ""),
                    "url": r.get("href", ""),
                    "description": r.get("body", ""),
                    "position": i + 1,
                })

        return {"success": True, "data": {"web": results}}
    except Exception as e:
        logger.error("DuckDuckGo search failed: %s", e)
        return {"success": False, "error": f"DuckDuckGo search failed: {e}"}


def patch():
    """Apply the DuckDuckGo fallback patch to web_tools."""
    import tools.web_tools as wt

    # ── 1. 让 _get_backend() 在无可用后端时返回 "duckduckgo" ──
    _original_get_backend = wt._get_backend

    def _get_backend_patched():
        configured = (wt._load_web_config().get("backend") or "").lower().strip()
        # 用户显式指定了某个后端 → 尊重配置（即使 key 可能无效）
        if configured in ("parallel", "firecrawl", "tavily", "exa"):
            return configured

        # 按优先级检查哪个后端可用
        for backend in ("firecrawl", "parallel", "tavily", "exa"):
            if wt._is_backend_available(backend):
                return backend

        # 全都不可用 → DuckDuckGo 兜底
        return "duckduckgo"

    wt._get_backend = _get_backend_patched

    # ── 2. 在 web_search_tool() 中添加 duckduckgo 分发 ──
    _original_web_search = wt.web_search_tool

    def web_search_patched(query: str, limit: int = 5) -> str:
        backend = wt._get_backend()

        if backend == "duckduckgo":
            logger.info("DuckDuckGo search (free fallback): '%s' (limit: %d)", query, limit)
            response_data = _ddg_search(query, limit)
            return json.dumps(response_data, indent=2, ensure_ascii=False)

        # 其他后端走原逻辑
        return _original_web_search(query, limit)

    wt.web_search_tool = web_search_patched

    # ── 3. 让 _is_backend_available("duckduckgo") 始终返回 True ──
    _original_is_backend_available = wt._is_backend_available

    def _is_backend_available_patched(backend: str) -> bool:
        if backend == "duckduckgo":
            return True
        return _original_is_backend_available(backend)

    wt._is_backend_available = _is_backend_available_patched

    # ── 4. 让 web_extract 也能在 duckduckgo 后端下工作 ──
    # web_extract 不依赖搜索后端（它直接抓 URL），但如果 _get_backend
    # 返回 "duckduckgo" 且 web_extract 内部也调用 _get_backend，需要兼容。
    # 目前 web_extract 不调用 _get_backend，所以不需要 patch。

    logger.info(
        "Web search: DuckDuckGo free fallback enabled "
        "(no API key required, auto-activates when paid backends unavailable)"
    )


if __name__ == "__main__":
    patch()