package com.nanri.aiimage.config;

import com.sun.net.httpserver.HttpServer;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.springframework.web.client.ResourceAccessException;
import org.springframework.web.client.RestClient;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.http.HttpClient;
import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeoutException;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.junit.jupiter.api.Assertions.fail;

/**
 * task-173：超时生效测试（plan 10，mock 慢端点）。
 *
 * 用本机回环 HttpServer 模拟慢端点，验证 HttpClientPool.requestFactory(readTimeout)
 * 真实管线：慢于配置超时的端点超时内失败、快/预算内响应不误伤、超时类型为
 * java.util.concurrent.TimeoutException、超时时长随配置缩放、连接超时对本机不可达地址生效。
 * 全部本地确定性，不发外部网络请求。
 *
 * 已核实的平台边界（task-166 记录）：JDK 请求超时封顶的是"到响应头"的时长，
 * 流式 body 读取不受请求超时约束，因此不为此编造"总时长封顶 body"的断言。
 */
class HttpClientTimeoutEffectiveTest {

    private static HttpServer server;
    private static ExecutorService serverExecutor;

    @BeforeAll
    static void startServer() throws IOException {
        serverExecutor = Executors.newCachedThreadPool(r -> {
            Thread t = new Thread(r, "http-timeout-test");
            t.setDaemon(true);
            return t;
        });
        server = HttpServer.create(new InetSocketAddress("127.0.0.1", 0), 0);
        server.setExecutor(serverExecutor);
        server.createContext("/slow", exchange -> {
            String query = exchange.getRequestURI().getQuery(); // ms=N
            long ms = 2_000;
            if (query != null && query.startsWith("ms=")) {
                ms = Long.parseLong(query.substring(3));
            }
            sleep(ms);
            respond(exchange, "slow-done");
        });
        server.createContext("/fast", exchange -> respond(exchange, "ok"));
        server.start();
    }

    @AfterAll
    static void stopServer() {
        if (server != null) {
            server.stop(0);
        }
        if (serverExecutor != null) {
            serverExecutor.shutdownNow();
        }
    }

    private static void respond(com.sun.net.httpserver.HttpExchange exchange, String body) throws IOException {
        byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
        exchange.sendResponseHeaders(200, bytes.length);
        try (OutputStream out = exchange.getResponseBody()) {
            out.write(bytes);
        }
    }

    private static void sleep(long ms) {
        try {
            Thread.sleep(ms);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }

    private static String baseUrl() {
        return "http://127.0.0.1:" + server.getAddress().getPort();
    }

    private static RestClient clientWithReadTimeout(int readTimeoutMillis) {
        return RestClient.builder()
                .requestFactory(HttpClientPool.requestFactory(readTimeoutMillis))
                .build();
    }

    @Test
    void readTimeoutFiresOnSlowEndpoint() {
        RestClient client = clientWithReadTimeout(300);
        long startedAt = System.nanoTime();
        ResourceAccessException ex = assertThrows(ResourceAccessException.class,
                () -> client.get().uri(baseUrl() + "/slow?ms=3000").retrieve().toBodilessEntity());
        long elapsedMs = (System.nanoTime() - startedAt) / 1_000_000;
        assertTrue(isTimeoutRoot(ex), "根因应为超时异常，实际 " + root(ex));
        assertTrue(elapsedMs < 1_500, "慢端点应在配置超时附近失败，实际 " + elapsedMs + "ms");
    }

    @Test
    void fastEndpointSucceedsWithoutTimeout() {
        RestClient client = clientWithReadTimeout(300);
        client.get().uri(baseUrl() + "/fast").retrieve().toBodilessEntity();
        // 未抛异常即通过：快响应不应被误判超时
    }

    @Test
    void moderatelySlowWithinBudgetSucceeds() {
        // 预算内慢响应（500ms < readTimeout 3000ms）应正常返回，不得提前误杀
        RestClient client = clientWithReadTimeout(3_000);
        client.get().uri(baseUrl() + "/slow?ms=500").retrieve().toBodilessEntity();
    }

    @Test
    void timeoutRootIsTimeoutException() {
        RestClient client = clientWithReadTimeout(200);
        ResourceAccessException ex = assertThrows(ResourceAccessException.class,
                () -> client.get().uri(baseUrl() + "/slow?ms=2000").retrieve().toBodilessEntity());
        // JDK 在负载下可能抛 java.util.concurrent.TimeoutException 或 java.net.http.HttpTimeoutException，
        // 两者同属"超时"；按超时语义断言而非绑定具体类型。
        assertTrue(isTimeoutRoot(ex), "根因应为超时异常，实际 " + root(ex));
    }

    @Test
    void readTimeoutScalesWithConfiguredValue() {
        long elapsedShort = timeToFail(150);
        long elapsedLong = timeToFail(700);
        assertTrue(elapsedShort < elapsedLong,
                "更小的 readTimeout 应更快失败：" + elapsedShort + "ms vs " + elapsedLong + "ms");
        assertTrue(elapsedLong < 2_500, "较长配置也应在合理范围内失败");
    }

    @Test
    void requestFactoryClampsNonPositiveReadTimeout() {
        // HttpClientPool.requestFactory 把非正值钳制到最小 1ms，慢端点极快失败
        RestClient client = RestClient.builder()
                .requestFactory(HttpClientPool.requestFactory(-5))
                .build();
        long startedAt = System.nanoTime();
        assertThrows(ResourceAccessException.class,
                () -> client.get().uri(baseUrl() + "/slow?ms=2000").retrieve().toBodilessEntity());
        long elapsedMs = (System.nanoTime() - startedAt) / 1_000_000;
        assertTrue(elapsedMs < 800, "钳制到 1ms 后应极快失败，实际 " + elapsedMs + "ms");
    }

    @Test
    void connectTimeoutFiresOnUnreachableHost() {
        // 本机不可达地址（TEST-NET-1 保留段）+ 短连接超时 → 在限定时间内以传输错误失败
        HttpClientProperties props = new HttpClientProperties();
        props.setConnectTimeoutMillis(500);
        HttpClient client = HttpClient.newBuilder()
                .connectTimeout(Duration.ofMillis(props.effectiveConnectTimeoutMillis()))
                .build();
        org.springframework.http.client.JdkClientHttpRequestFactory factory =
                new org.springframework.http.client.JdkClientHttpRequestFactory(client);
        RestClient rest = RestClient.builder().requestFactory(factory).build();

        long startedAt = System.nanoTime();
        try {
            rest.get().uri("http://192.0.2.1:81/").retrieve().toBodilessEntity();
            fail("不可达地址不应成功");
        } catch (ResourceAccessException expected) {
            // 预期：连接超时或快速不可达，均属传输错误
        }
        long elapsedMs = (System.nanoTime() - startedAt) / 1_000_000;
        assertTrue(elapsedMs < 3_000, "连接超时应在限定时间内失败，实际 " + elapsedMs + "ms");
    }

    @Test
    void sharedPoolAndNamespaceDefaultsAreOperative() {
        // 连接超时来源=共享 HttpClient(10s)；命名空间默认 read=60s 经 requestFactory 生效且不误伤快响应
        assertEquals(Duration.ofSeconds(10), HttpClientPool.sharedHttpClient().connectTimeout().orElseThrow(),
                "共享 HttpClient 连接超时为 10s");
        HttpClientProperties props = new HttpClientProperties();
        assertEquals(60_000L, props.effectiveReadTimeoutMillis());
        RestClient client = clientWithReadTimeout((int) props.effectiveReadTimeoutMillis());
        client.get().uri(baseUrl() + "/fast").retrieve().toBodilessEntity();
    }

    private static long timeToFail(int readTimeoutMillis) {
        RestClient client = clientWithReadTimeout(readTimeoutMillis);
        long startedAt = System.nanoTime();
        assertThrows(ResourceAccessException.class,
                () -> client.get().uri(baseUrl() + "/slow?ms=5000").retrieve().toBodilessEntity());
        return (System.nanoTime() - startedAt) / 1_000_000;
    }

    private static Throwable root(Throwable error) {
        Throwable current = error;
        while (current.getCause() != null && current.getCause() != current) {
            current = current.getCause();
        }
        return current;
    }

    private static boolean isTimeoutRoot(Throwable error) {
        return root(error) instanceof TimeoutException
                || root(error) instanceof java.net.http.HttpTimeoutException;
    }
}