"""第5-6课标准示例：启动本地HTTP服务并自动调用图书接口。"""

import json
from http import HTTPStatus
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from threading import Thread
from urllib.error import HTTPError
from urllib.request import Request, urlopen


class BookApiHandler(BaseHTTPRequestHandler):
    """处理本课图书查询和新增请求的最小HTTP处理器。"""

    # 本课不连接数据库，使用类属性保存当前程序运行期间的图书。
    # 程序退出后这份列表会消失，再次运行时会重新从一条图书开始。
    books = [{"id": 1, "title": "Python入门"}]

    def send_json(
        self,
        status: HTTPStatus,
        data: dict | list,
        extra_headers: dict | None = None,
    ) -> None:
        """把Python对象转换为UTF-8 JSON响应。"""

        # HTTP连接传输的是字节，因此先生成JSON字符串，再编码成UTF-8字节。
        response_body = json.dumps(data, ensure_ascii=False).encode("utf-8")
        self.send_response(status)
        self.send_header("Content-Type", "application/json; charset=utf-8")
        # Content-Length必须填写字节数量，不能直接计算中文字符串的字符数。
        self.send_header("Content-Length", str(len(response_body)))
        if extra_headers is not None:
            for header_name, header_value in extra_headers.items():
                self.send_header(header_name, header_value)
        self.end_headers()
        self.wfile.write(response_body)

    def do_GET(self) -> None:
        """处理GET /books，并拒绝未知路径。"""

        # 标准库收到GET请求后会自动调用本方法，self.path保存请求目标。
        if self.path == "/books":
            self.send_json(HTTPStatus.OK, {"items": self.books})
            return
        self.send_json(HTTPStatus.NOT_FOUND, {"message": "资源不存在"})

    def do_POST(self) -> None:
        """处理POST /books，校验JSON并创建图书。"""

        if self.path != "/books":
            self.send_json(HTTPStatus.NOT_FOUND, {"message": "资源不存在"})
            return

        try:
            # Content-Length告诉服务器本次请求体一共有多少字节。
            content_length = int(self.headers.get("Content-Length", "0"))
            request_body = self.rfile.read(content_length).decode("utf-8")
            request_data = json.loads(request_body)
        except (UnicodeDecodeError, json.JSONDecodeError):
            self.send_json(HTTPStatus.BAD_REQUEST, {"message": "JSON格式错误"})
            return

        title = request_data.get("title")
        if not isinstance(title, str) or not title.strip():
            self.send_json(
                HTTPStatus.UNPROCESSABLE_CONTENT,
                {"message": "书名不能为空"},
            )
            return

        # 本课用列表长度模拟生成编号；真实项目通常由数据库生成主键。
        book = {"id": len(self.books) + 1, "title": title.strip()}
        self.books.append(book)
        self.send_json(
            HTTPStatus.CREATED,
            book,
            {"Location": f"/books/{book['id']}"},
        )

    def log_message(self, format_text: str, *args: object) -> None:
        """关闭标准库默认访问日志，让教学输出保持清晰。"""


def send_request(
    url: str,
    method: str = "GET",
    data: dict | None = None,
) -> None:
    """作为客户端发送HTTP请求并输出响应。"""

    request_body = None
    headers = {"Accept": "application/json"}
    if data is not None:
        request_body = json.dumps(data, ensure_ascii=False).encode("utf-8")
        headers["Content-Type"] = "application/json; charset=utf-8"

    # Request只负责描述请求；urlopen()执行时才真正连接服务器并发送请求。
    request = Request(url, data=request_body, headers=headers, method=method)
    try:
        with urlopen(request, timeout=3) as response:
            response_text = response.read().decode("utf-8")
            print(f"{method} {request.full_url} -> {response.status}")
            print(f"响应体：{response_text}")
    except HTTPError as error:
        response_text = error.read().decode("utf-8")
        print(f"{method} {request.full_url} -> {error.code}")
        print(f"响应体：{response_text}")


def main() -> None:
    """在随机本地端口启动服务，完成调用后安全关闭。"""

    # 127.0.0.1限制为本机访问；端口0表示让操作系统选择可用端口。
    server = ThreadingHTTPServer(("127.0.0.1", 0), BookApiHandler)
    # 服务器需要持续等待请求，因此放入后台线程；主线程继续充当客户端。
    server_thread = Thread(target=server.serve_forever, daemon=True)
    server_thread.start()
    host, port = server.server_address
    base_url = f"http://{host}:{port}"
    print(f"本地服务已启动：{base_url}")

    try:
        send_request(f"{base_url}/books")
        send_request(
            f"{base_url}/books",
            method="POST",
            data={"title": "HTTP接口实践"},
        )
        send_request(f"{base_url}/books")
        send_request(f"{base_url}/missing")
    finally:
        # 即使某次请求失败，也必须释放监听端口并等待后台线程退出。
        server.shutdown()
        server.server_close()
        server_thread.join()
        print("本地服务已关闭。")


if __name__ == "__main__":
    main()