package com.webgame.webgamebackend.sse;

import com.webgame.webgamebackend.common.auth.AuthenticationProvider;
import jakarta.servlet.http.HttpServletResponse;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;

import java.io.IOException;

/**
 * SSE 订阅端点
 *
 * 提供 GET /sse/subscribe 端点建立持久化 SSE 连接。
 * 心跳由 SseConnectionManager 统一批量管理，此处不再维护 per-connection 定时器。
 */
@Slf4j
@RestController
@RequestMapping("/sse")
@RequiredArgsConstructor
public class SseController {

    /** SseEmitter 超时时间（30 分钟），超时后由 SseConnectionManager 的 onTimeout 回调清理 */
    private static final long SSE_TIMEOUT_MS = 30 * 60 * 1000L;

    private final SseConnectionManager connectionManager;
    private final AuthenticationProvider authProvider;

    @GetMapping(value = "/subscribe", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
    public SseEmitter subscribe(
            @RequestHeader(value = "Last-Event-ID", required = false) String lastEventId,
            HttpServletResponse response) throws IOException {

        // SSE 路径已排除在 AuthInterceptor 之外，此处手动校验登录态
        String token = authProvider.getCurrentToken();
        if (token == null || token.isBlank()) {
            log.warn("[SSE] 缺少认证 token");
            return writeAuthError(response, HttpServletResponse.SC_UNAUTHORIZED, "缺少认证信息，请先登录");
        }

        String userId = authProvider.getUserIdByToken(token);
        if (userId == null) {
            log.warn("[SSE] token 无效或已过期");
            return writeAuthError(response, HttpServletResponse.SC_UNAUTHORIZED, "登录已过期，请重新登录");
        }

        // 设置认证上下文，后续 getCurrentUserId() 可用
        authProvider.setContextToken(token, -1);
        SseEmitter emitter = new SseEmitter(SSE_TIMEOUT_MS);
        String connectionId = connectionManager.register(userId, emitter);

        // 发送初始连接确认
        try {
            emitter.send(SseEmitter.event()
                    .name("connected")
                    .data("{\"message\":\"连接成功\"}"));
        } catch (IOException | IllegalStateException e) {
            log.warn("[SSE] 发送 connected 事件失败, userId={}, connectionId={}",
                    userId, connectionId, e);
            connectionManager.remove(userId, connectionId);
        }

        if (lastEventId != null && !lastEventId.isBlank()) {
            log.debug("[SSE] 客户端重连, Last-Event-ID={}, userId={}, connectionId={}",
                    lastEventId, userId, connectionId);
        }

        return emitter;
    }

    /**
     * 向 SSE 客户端返回认证错误
     *
     * 直接写入 HttpServletResponse 返回 401 + SSE error 事件，
     * 前端 SseClient.onopen 检测到 response.status === 401 后触发 onUnauthorized，
     * 自动刷新 token 并重连。
     *
     * @return null，通知 Spring MVC 响应已处理完毕，无需 MessageConverter
     */
    private SseEmitter writeAuthError(HttpServletResponse response, int status, String message) throws IOException {
        response.setStatus(status);
        response.setContentType(MediaType.TEXT_EVENT_STREAM_VALUE);
        response.getWriter().write("event: error\ndata: {\"code\":" + status + ",\"message\":\"" + message + "\"}\n\n");
        response.getWriter().flush();
        return null;
    }
}