package middleware

import (
	"net"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"
)

func TestRateLimit_AllowsUnderLimit(t *testing.T) {
	h := RateLimit(RateLimitConfig{
		Requests: 5,
		Window:   10 * time.Second,
	}, nil)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	}))

	for i := 0; i < 5; i++ {
		req := httptest.NewRequest("GET", "/search?q=test", nil)
		req.RemoteAddr = "1.2.3.4:1234"
		rec := httptest.NewRecorder()
		h.ServeHTTP(rec, req)
		if rec.Code != http.StatusOK {
			t.Fatalf("request %d: expected 200, got %d", i+1, rec.Code)
		}
	}
}

func TestRateLimit_BlocksOverLimit(t *testing.T) {
	h := RateLimit(RateLimitConfig{
		Requests: 3,
		Window:   10 * time.Second,
	}, nil)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	}))

	for i := 0; i < 3; i++ {
		req := httptest.NewRequest("GET", "/search?q=test", nil)
		req.RemoteAddr = "1.2.3.4:1234"
		rec := httptest.NewRecorder()
		h.ServeHTTP(rec, req)
		if rec.Code != http.StatusOK {
			t.Fatalf("request %d: expected 200, got %d", i+1, rec.Code)
		}
	}

	// 4th request should be blocked.
	req := httptest.NewRequest("GET", "/search?q=test", nil)
	req.RemoteAddr = "1.2.3.4:1234"
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if rec.Code != http.StatusTooManyRequests {
		t.Errorf("expected 429, got %d", rec.Code)
	}
}

func TestRateLimit_DifferentIPs(t *testing.T) {
	h := RateLimit(RateLimitConfig{
		Requests: 1,
		Window:   10 * time.Second,
	}, nil)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	}))

	// IP A: allowed
	req := httptest.NewRequest("GET", "/search", nil)
	req.RemoteAddr = "1.1.1.1:1234"
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Errorf("IP A first request: expected 200, got %d", rec.Code)
	}

	// IP A: blocked
	req = httptest.NewRequest("GET", "/search", nil)
	req.RemoteAddr = "1.1.1.1:1234"
	rec = httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusTooManyRequests {
		t.Errorf("IP A second request: expected 429, got %d", rec.Code)
	}

	// IP B: allowed (separate bucket)
	req = httptest.NewRequest("GET", "/search", nil)
	req.RemoteAddr = "2.2.2.2:1234"
	rec = httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Errorf("IP B first request: expected 200, got %d", rec.Code)
	}
}

func TestRateLimit_XForwardedFor(t *testing.T) {
	h := RateLimit(RateLimitConfig{
		Requests:        1,
		Window:          10 * time.Second,
		TrustedProxies:  []string{"10.0.0.0/8"},
	}, nil)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	}))

	// Request via proxy — should use X-Forwarded-For.
	req := httptest.NewRequest("GET", "/search", nil)
	req.RemoteAddr = "10.0.0.1:1234"
	req.Header.Set("X-Forwarded-For", "203.0.113.50, 10.0.0.1")
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Errorf("first XFF request: expected 200, got %d", rec.Code)
	}

	// Different proxy, same client IP — should be blocked.
	req = httptest.NewRequest("GET", "/search", nil)
	req.RemoteAddr = "10.0.0.2:1234"
	req.Header.Set("X-Forwarded-For", "203.0.113.50, 10.0.0.2")
	rec = httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusTooManyRequests {
		t.Errorf("same XFF client: expected 429, got %d", rec.Code)
	}
}

func TestRateLimit_WindowExpires(t *testing.T) {
	limiter := &ipLimiter{
		requests: 1,
		window:   50 * time.Millisecond,
		clients:  make(map[string]*bucket),
	}

	if !limiter.allow("1.1.1.1") {
		t.Error("first request should be allowed")
	}
	if limiter.allow("1.1.1.1") {
		t.Error("second request should be blocked")
	}

	// Wait for window to expire.
	time.Sleep(60 * time.Millisecond)

	if !limiter.allow("1.1.1.1") {
		t.Error("request after window expiry should be allowed")
	}
}

func TestExtractIP(t *testing.T) {
	// Trusted proxy: loopback
	loopback := mustParseCIDR("127.0.0.0/8")
	privateNet := mustParseCIDR("10.0.0.0/8")

	tests := []struct {
		name     string
		xff      string
		realIP   string
		remote   string
		trusted  []*net.IPNet
		expected string
	}{
		// No trusted proxies → always use RemoteAddr.
		{"no_trusted_xff", "203.0.113.50, 10.0.0.1", "", "10.0.0.1:1234", nil, "10.0.0.1"},
		{"no_trusted_real", "", "203.0.113.50", "10.0.0.1:1234", nil, "10.0.0.1"},
		{"no_trusted_remote", "", "", "1.2.3.4:5678", nil, "1.2.3.4"},
		// Trusted proxy → XFF is respected.
		{"trusted_xff", "203.0.113.50, 10.0.0.1", "", "10.0.0.1:1234", []*net.IPNet{privateNet}, "203.0.113.50"},
		{"trusted_real_ip", "", "203.0.113.50", "10.0.0.1:1234", []*net.IPNet{privateNet}, "203.0.113.50"},
		// Untrusted remote → XFF ignored even if present.
		{"untrusted_xff", "203.0.113.50, 10.0.0.1", "", "1.2.3.4:5678", []*net.IPNet{loopback}, "1.2.3.4"},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			req := httptest.NewRequest("GET", "/", nil)
			if tt.xff != "" {
				req.Header.Set("X-Forwarded-For", tt.xff)
			}
			if tt.realIP != "" {
				req.Header.Set("X-Real-IP", tt.realIP)
			}
			req.RemoteAddr = tt.remote

			if got := extractIP(req, tt.trusted...); got != tt.expected {
				t.Errorf("extractIP() = %q, want %q", got, tt.expected)
			}
		})
	}
}

func mustParseCIDR(s string) *net.IPNet {
	_, network, err := net.ParseCIDR(s)
	if err != nil {
		panic(err)
	}
	return network
}