# -*- coding: utf-8 -*-
"""前端对话组件后端 API —— issue #77（Template-Ti 一期）。

父 Issue #11「④ LLM 报警解释 / 交接班 / NL 查询」子任务：
为驾驶舱/移动端提供对话组件所需的后端 API：

- `GET /`：返回对话组件页面（chat_widget.html，静态）；
- `GET /api/health`：服务健康；
- `POST /api/chat`：对话接口——按 `scenario` 分发到 Ti 场景
  （alarm_explain / shift_handover / nl_query），返回统一 JSON：
  `{answer, route, answer_id, scenario}`。

纯标准库实现（http.server，无框架依赖），便于联调/内嵌；
runner 可注入（测试/替换实现均解耦）。
"""
from __future__ import annotations

import json
import os
from typing import Optional
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from urllib.parse import urlparse

#: 组件页面路径（相对本模块）
WIDGET_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)),
                           "chat_widget.html")

#: 场景 → runner 方法映射
SCENARIO_METHODS = {
    "alarm_explain": "explain_alarm",
    "shift_handover": "generate_handover",
    "nl_query": "query_cockpit",
    "default": "query_cockpit",
}


def dispatch(runner, request: dict) -> dict:
    """按请求分发到场景 runner，返回统一响应。

    Args:
        runner: 提供 explain_alarm / generate_handover / query_cockpit 的对象；
        request: `{question, scenario, confidence?}`。
    Returns:
        统一 JSON 字典；场景未知 → 降级 nl_query；异常 → error 响应。
    """
    question = str(request.get("question", "")).strip()
    scenario = str(request.get("scenario", "default"))
    confidence = float(request.get("confidence", 1.0))
    if not question:
        return {"error": "question 不能为空"}

    method_name = SCENARIO_METHODS.get(
        scenario, SCENARIO_METHODS["default"])
    resolved = scenario if scenario in SCENARIO_METHODS else "default"
    method = getattr(runner, method_name, None)
    if method is None:
        return {"error": f"场景 {scenario!r} 未实现"}

    try:
        result = method(question, confidence=confidence)
    except Exception as exc:  # noqa: BLE001 - 统一异常 → error JSON
        return {"error": f"处理失败: {exc}"}

    return {
        "answer": result.answer,
        "route": getattr(result.route, "target", ""),
        "answer_id": getattr(result, "answer_id", ""),
        "scenario": resolved,
        "needs_human": bool(getattr(result, "needs_human", False)),
    }


class ChatHandler(BaseHTTPRequestHandler):
    """对话 API HTTP 处理（GET 组件页 / POST /api/chat）。"""

    #: 场景 runner（由 make_server 注入）
    runner = None

    def log_message(self, *args):  # 静默访问日志
        pass

    def do_GET(self):
        path = urlparse(self.path).path
        if path == "/api/health":
            self._json(200, {"status": "ok"})
            return
        if path in ("/", "/index.html", "/chat_widget.html"):
            self._html(WIDGET_PATH)
            return
        self._json(404, {"error": "not found"})

    def do_POST(self):
        if urlparse(self.path).path != "/api/chat":
            self._json(404, {"error": "not found"})
            return
        try:
            length = int(self.headers.get("Content-Length", 0))
            request = json.loads(self.rfile.read(length).decode("utf-8"))
        except (ValueError, json.JSONDecodeError):
            self._json(400, {"error": "请求体不是合法 JSON"})
            return
        self._json(200, dispatch(self.runner, request))

    # ------------------------------------------------------------------
    def _json(self, code: int, payload: dict) -> None:
        body = json.dumps(payload, ensure_ascii=False).encode("utf-8")
        self.send_response(code)
        self.send_header("Content-Type", "application/json; charset=utf-8")
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

    def _html(self, path: str) -> None:
        if not os.path.isfile(path):
            self._json(404, {"error": "widget 页面缺失"})
            return
        with open(path, "rb") as fh:
            body = fh.read()
        self.send_response(200)
        self.send_header("Content-Type", "text/html; charset=utf-8")
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)


def make_server(host: str, port: int, runner=None) -> ThreadingHTTPServer:
    """构建对话 API 服务器（runner 可注入，便于测试/替换）。"""
    ChatHandler.runner = runner
    return ThreadingHTTPServer((host, port), ChatHandler)


if __name__ == "__main__":
    import argparse

    parser = argparse.ArgumentParser(description="对话 API 服务（issue #77）")
    parser.add_argument("--host", default="127.0.0.1")
    parser.add_argument("--port", type=int, default=8080)
    args = parser.parse_args()
    print(f"对话 API 服务：http://{args.host}:{args.port}/（组件页）")
    make_server(args.host, args.port).serve_forever()