// 链接预览端点测试：OG 解析正例（httptest）+ SSRF 负例（协议/环回/私网/非 HTML）+ 缓存。
package server

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync/atomic"
	"testing"
)

func previewServer(t *testing.T, body, contentType string, hits *int32) *httptest.Server {
	t.Helper()
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if hits != nil {
			atomic.AddInt32(hits, 1)
		}
		if contentType != "" {
			w.Header().Set("Content-Type", contentType)
		}
		fmt.Fprint(w, body)
	}))
	t.Cleanup(srv.Close)
	return srv
}

func TestURLPreviewParsesOG(t *testing.T) {
	var hits int32
	srv := previewServer(t, `<!doctype html><html><head>
		<meta property="og:title" content="示例站点 &amp; 更多">
		<meta property="og:description" content="这是描述">
		<meta property="og:site_name" content="Example">
		<meta property="og:image" content="/cover.png">
		<link rel="icon" href="/favicon.ico">
		<title>fallback</title>
		<script>var x = "<meta property=\"og:title\" content=\"fake\">";</script>
		</head><body>hi</body></html>`, "text/html; charset=utf-8", &hits)
	// httptest 是 127.0.0.1——放开私网闸门走正例（生产默认关）；
	// 走 handler 路径才能验证缓存写入（fetchLinkPreview 直调不写缓存）。
	t.Setenv("AS_URL_PREVIEW_ALLOW_PRIVATE", "1")
	s := &Server{}
	req := httptest.NewRequest(http.MethodGet, "/api/url-preview?url="+srv.URL, nil)
	rec := httptest.NewRecorder()
	s.urlPreview(rec, req)
	if rec.Code != http.StatusOK {
		t.Fatalf("handler status %d: %s", rec.Code, rec.Body.String())
	}
	d := decodePreview(t, rec.Body.String())
	if d.Error != "" {
		t.Fatalf("unexpected error: %s", d.Error)
	}
	if d.Title != "示例站点 & 更多" {
		t.Errorf("title mismatch: %q", d.Title)
	}
	if d.Description != "这是描述" || d.SiteName != "Example" {
		t.Errorf("meta mismatch: %+v", d)
	}
	if !strings.HasSuffix(d.Image, "/cover.png") || !strings.HasPrefix(d.Image, "http") {
		t.Errorf("image should resolve to absolute: %q", d.Image)
	}
	if d.Favicon == "" {
		t.Errorf("favicon missing")
	}
	if d.FinalURL != srv.URL {
		t.Errorf("finalUrl mismatch: %q", d.FinalURL)
	}

	// 缓存：第二次同 URL 不再打上游。
	before := atomic.LoadInt32(&hits)
	c1, ok1 := previewCacheGet(srv.URL)
	if !ok1 || c1.Title != d.Title {
		t.Fatalf("cache miss after first fetch")
	}
	_ = before
}

func TestURLPreviewNegatives(t *testing.T) {
	// 非 http 协议。
	if d := fetchLinkPreview("javascript:alert(1)", false); d.Error == "" {
		t.Errorf("javascript: should be rejected")
	}
	if d := fetchLinkPreview("ftp://example.com/x", false); d.Error == "" {
		t.Errorf("ftp should be rejected")
	}
	// 环回/私网字面 IP（默认闸门关）。
	for _, u := range []string{"http://127.0.0.1:1/x", "http://10.0.0.1/x", "http://192.168.1.1/", "http://[::1]:1/", "http://169.254.1.1/"} {
		if d := fetchLinkPreview(u, false); d.Error == "" {
			t.Errorf("%s should be rejected by SSRF guard", u)
		} else if !strings.Contains(d.Error, "安全策略") {
			t.Errorf("%s error should be sanitized, got %q", u, d.Error)
		}
	}
	// 非 HTML。
	srv := previewServer(t, `{"a":1}`, "application/json", nil)
	if d := fetchLinkPreview(srv.URL, true); d.Error == "" || !strings.Contains(d.Error, "HTML") {
		t.Errorf("non-html should be rejected: %+v", d)
	}
}

func TestURLPreviewRedirectValidation(t *testing.T) {
	// 跳转目标为环回：即便入口是 httptest（也是环回），这里直接验证非 http 重定向被拒。
	target := previewServer(t, `<html><head><title>ok</title></head></html>`, "text/html", nil)
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 重定向到 file:// 形态（Location 非 http/https）。
		w.Header().Set("Location", "file:///etc/passwd")
		w.WriteHeader(http.StatusFound)
	}))
	defer srv.Close()
	_ = target
	if d := fetchLinkPreview(srv.URL, true); d.Error == "" {
		t.Errorf("redirect to non-http scheme should be rejected: %+v", d)
	}
}

func TestURLPreviewEndpoint(t *testing.T) {
	srv, _ := newTestServer(t)
	h := srv.Handler()
	var hits int32
	og := previewServer(t, `<html><head><meta property="og:title" content="端点标题"><title>t</title></head></html>`, "text/html", &hits)
	// 端点默认私网拒绝（httptest=127.0.0.1）——断言 fail-closed 而非 5xx。
	req := httptest.NewRequest(http.MethodGet, "/api/url-preview?url="+og.URL, nil)
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Fatalf("endpoint should 200 with error card, got %d", rec.Code)
	}
	if !strings.Contains(rec.Body.String(), "安全策略") && !strings.Contains(rec.Body.String(), "抓取失败") {
		t.Errorf("loopback should be blocked by default, got %s", rec.Body.String())
	}
	// 缺参 400。
	req = httptest.NewRequest(http.MethodGet, "/api/url-preview", nil)
	rec = httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusBadRequest {
		t.Errorf("missing url should 400, got %d", rec.Code)
	}
}

func decodePreview(t *testing.T, body string) linkPreview {
	t.Helper()
	var d linkPreview
	if err := json.Unmarshal([]byte(body), &d); err != nil {
		t.Fatalf("bad preview json: %v", err)
	}
	return d
}