package sipguardian

import (
	"sync"
	"testing"
	"time"

	"go.uber.org/zap"
)

// =============================================================================
// Rate Limiter Tests - Ensuring legitimate traffic flows through
// =============================================================================

func TestRateLimiterBasicAllow(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	// Configure a simple limit
	rl.SetLimit(MethodREGISTER, &MethodRateLimit{
		Method:      MethodREGISTER,
		MaxRequests: 10,
		Window:      time.Minute,
		BurstSize:   5,
	})

	ip := "192.168.1.100"

	// First 5 requests should be allowed (burst)
	for i := 0; i < 5; i++ {
		allowed, reason := rl.Allow(ip, MethodREGISTER)
		if !allowed {
			t.Errorf("Request %d should be allowed within burst, reason: %s", i+1, reason)
		}
	}
}

func TestRateLimiterBurstExhaustion(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	rl.SetLimit(MethodREGISTER, &MethodRateLimit{
		Method:      MethodREGISTER,
		MaxRequests: 10,
		Window:      time.Minute,
		BurstSize:   3,
	})

	ip := "192.168.1.101"

	// Exhaust burst
	for i := 0; i < 3; i++ {
		allowed, _ := rl.Allow(ip, MethodREGISTER)
		if !allowed {
			t.Errorf("Request %d should be allowed within burst", i+1)
		}
	}

	// Next request should be rate limited (burst exhausted)
	allowed, reason := rl.Allow(ip, MethodREGISTER)
	if allowed {
		t.Error("Request after burst should be rate limited")
	}
	if reason != "rate_limit_REGISTER" {
		t.Errorf("Reason should be rate_limit_REGISTER, got: %s", reason)
	}
}

func TestRateLimiterTokenRefill(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	// 60 requests per minute = 1 per second
	rl.SetLimit(MethodOPTIONS, &MethodRateLimit{
		Method:      MethodOPTIONS,
		MaxRequests: 60,
		Window:      time.Minute,
		BurstSize:   2,
	})

	ip := "192.168.1.102"

	// Exhaust burst
	rl.Allow(ip, MethodOPTIONS)
	rl.Allow(ip, MethodOPTIONS)

	// Should be blocked now
	allowed, _ := rl.Allow(ip, MethodOPTIONS)
	if allowed {
		t.Error("Should be rate limited after burst")
	}

	// Wait for token refill (slightly more than 1 second for 1 token)
	time.Sleep(1100 * time.Millisecond)

	// Should be allowed again
	allowed, reason := rl.Allow(ip, MethodOPTIONS)
	if !allowed {
		t.Errorf("Should be allowed after token refill, reason: %s", reason)
	}
}

func TestRateLimiterDifferentMethods(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	// Different limits for different methods
	rl.SetLimit(MethodREGISTER, &MethodRateLimit{
		Method:      MethodREGISTER,
		MaxRequests: 10,
		Window:      time.Minute,
		BurstSize:   2,
	})
	rl.SetLimit(MethodINVITE, &MethodRateLimit{
		Method:      MethodINVITE,
		MaxRequests: 30,
		Window:      time.Minute,
		BurstSize:   5,
	})

	ip := "192.168.1.103"

	// Exhaust REGISTER burst
	rl.Allow(ip, MethodREGISTER)
	rl.Allow(ip, MethodREGISTER)

	// REGISTER should be blocked
	allowed, _ := rl.Allow(ip, MethodREGISTER)
	if allowed {
		t.Error("REGISTER should be rate limited")
	}

	// But INVITE should still work (separate bucket)
	for i := 0; i < 5; i++ {
		allowed, reason := rl.Allow(ip, MethodINVITE)
		if !allowed {
			t.Errorf("INVITE %d should be allowed, reason: %s", i+1, reason)
		}
	}
}

func TestRateLimiterDifferentIPs(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	rl.SetLimit(MethodREGISTER, &MethodRateLimit{
		Method:      MethodREGISTER,
		MaxRequests: 10,
		Window:      time.Minute,
		BurstSize:   2,
	})

	ip1 := "192.168.1.104"
	ip2 := "192.168.1.105"

	// Exhaust IP1's burst
	rl.Allow(ip1, MethodREGISTER)
	rl.Allow(ip1, MethodREGISTER)
	allowed, _ := rl.Allow(ip1, MethodREGISTER)
	if allowed {
		t.Error("IP1 should be rate limited")
	}

	// IP2 should still work (separate bucket)
	for i := 0; i < 2; i++ {
		allowed, reason := rl.Allow(ip2, MethodREGISTER)
		if !allowed {
			t.Errorf("IP2 request %d should be allowed, reason: %s", i+1, reason)
		}
	}
}

func TestRateLimiterDefaultLimits(t *testing.T) {
	logger := zap.NewNop()

	// Reset global rate limiter to get a fresh instance with defaults applied
	rateLimiterMu.Lock()
	globalRateLimiter = nil
	rateLimiterMu.Unlock()

	// GetRateLimiter applies default limits from DefaultMethodLimits
	rl := GetRateLimiter(logger)

	// Test that DefaultMethodLimits are applied
	for method, expectedLimit := range DefaultMethodLimits {
		limit := rl.GetLimit(method)
		if limit.MaxRequests != expectedLimit.MaxRequests {
			t.Errorf("Default limit for %s: got %d, want %d", method, limit.MaxRequests, expectedLimit.MaxRequests)
		}
	}
}

func TestNewRateLimiterHasNoDefaultLimits(t *testing.T) {
	// NewRateLimiter creates a fresh limiter without default method limits
	// This is intentional for testing and custom configurations
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	// Should return the global default (100), not method-specific defaults
	limit := rl.GetLimit(MethodREGISTER)
	if limit.MaxRequests != 100 {
		t.Errorf("NewRateLimiter should have global default 100 for unconfigured methods, got %d", limit.MaxRequests)
	}
}

func TestRateLimiterConcurrentAccess(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	rl.SetLimit(MethodREGISTER, &MethodRateLimit{
		Method:      MethodREGISTER,
		MaxRequests: 100,
		Window:      time.Minute,
		BurstSize:   50,
	})

	var wg sync.WaitGroup
	allowedCount := 0
	var mu sync.Mutex

	// Simulate 100 concurrent requests from different IPs
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func(n int) {
			defer wg.Done()
			ip := "192.168.1." + string(rune('0'+n%10))
			allowed, _ := rl.Allow(ip, MethodREGISTER)
			if allowed {
				mu.Lock()
				allowedCount++
				mu.Unlock()
			}
		}(i)
	}

	wg.Wait()

	// Should have allowed most requests (10 IPs with burst of 50 each = up to 500 capacity)
	if allowedCount < 90 {
		t.Errorf("Expected at least 90 allowed requests, got %d", allowedCount)
	}
}

func TestRateLimiterCleanup(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	// Add some buckets
	rl.Allow("192.168.1.1", MethodREGISTER)
	rl.Allow("192.168.1.2", MethodREGISTER)
	rl.Allow("192.168.1.3", MethodREGISTER)

	stats := rl.GetStats()
	trackedIPs := stats["tracked_ips"].(int)
	if trackedIPs != 3 {
		t.Errorf("Should have 3 tracked IPs, got %d", trackedIPs)
	}

	// Cleanup shouldn't remove fresh entries
	rl.Cleanup()
	stats = rl.GetStats()
	trackedIPs = stats["tracked_ips"].(int)
	if trackedIPs != 3 {
		t.Errorf("Fresh entries should not be cleaned up, got %d IPs", trackedIPs)
	}
}

func TestRateLimiterStats(t *testing.T) {
	logger := zap.NewNop()
	rl := NewRateLimiter(logger)

	rl.SetLimit(MethodREGISTER, &MethodRateLimit{
		Method:      MethodREGISTER,
		MaxRequests: 10,
		Window:      time.Minute,
		BurstSize:   5,
	})

	rl.Allow("192.168.1.100", MethodREGISTER)

	stats := rl.GetStats()

	if _, ok := stats["tracked_ips"]; !ok {
		t.Error("Stats should include tracked_ips")
	}
	if _, ok := stats["limits"]; !ok {
		t.Error("Stats should include limits")
	}

	limits := stats["limits"].(map[string]interface{})
	if _, ok := limits["REGISTER"]; !ok {
		t.Error("Limits should include REGISTER config")
	}
}

func TestGlobalRateLimiter(t *testing.T) {
	logger := zap.NewNop()

	// Reset global rate limiter for clean test
	rateLimiterMu.Lock()
	globalRateLimiter = nil
	rateLimiterMu.Unlock()

	rl := GetRateLimiter(logger)
	if rl == nil {
		t.Fatal("GetRateLimiter should return non-nil")
	}

	// Should return same instance
	rl2 := GetRateLimiter(logger)
	if rl != rl2 {
		t.Error("GetRateLimiter should return same global instance")
	}

	// Should have default limits applied
	registerLimit := rl.GetLimit(MethodREGISTER)
	if registerLimit.MaxRequests != 10 {
		t.Errorf("Global rate limiter should have default REGISTER limit, got %d", registerLimit.MaxRequests)
	}
}

// =============================================================================
// SIP Parsing Function Tests
// =============================================================================

func TestExtractSIPMethod(t *testing.T) {
	tests := []struct {
		name     string
		data     []byte
		expected SIPMethod
	}{
		{"REGISTER", []byte("REGISTER sip:example.com SIP/2.0\r\n"), MethodREGISTER},
		{"INVITE", []byte("INVITE sip:alice@example.com SIP/2.0\r\n"), MethodINVITE},
		{"OPTIONS", []byte("OPTIONS sip:example.com SIP/2.0\r\n"), MethodOPTIONS},
		{"ACK", []byte("ACK sip:alice@example.com SIP/2.0\r\n"), MethodACK},
		{"BYE", []byte("BYE sip:alice@example.com SIP/2.0\r\n"), MethodBYE},
		{"CANCEL", []byte("CANCEL sip:alice@example.com SIP/2.0\r\n"), MethodCANCEL},
		{"INFO", []byte("INFO sip:alice@example.com SIP/2.0\r\n"), MethodINFO},
		{"NOTIFY", []byte("NOTIFY sip:alice@example.com SIP/2.0\r\n"), MethodNOTIFY},
		{"SUBSCRIBE", []byte("SUBSCRIBE sip:alice@example.com SIP/2.0\r\n"), MethodSUBSCRIBE},
		{"MESSAGE", []byte("MESSAGE sip:alice@example.com SIP/2.0\r\n"), MethodMESSAGE},
		{"UPDATE", []byte("UPDATE sip:alice@example.com SIP/2.0\r\n"), MethodUPDATE},
		{"PRACK", []byte("PRACK sip:alice@example.com SIP/2.0\r\n"), MethodPRACK},
		{"REFER", []byte("REFER sip:alice@example.com SIP/2.0\r\n"), MethodREFER},
		{"PUBLISH", []byte("PUBLISH sip:alice@example.com SIP/2.0\r\n"), MethodPUBLISH},
		{"Response (no method)", []byte("SIP/2.0 200 OK\r\n"), ""},
		{"Non-SIP", []byte("GET / HTTP/1.1\r\n"), ""},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			method := ExtractSIPMethod(tt.data)
			if method != tt.expected {
				t.Errorf("ExtractSIPMethod: got %q, want %q", method, tt.expected)
			}
		})
	}
}

// Note: TestExtractTargetExtension is already defined in enumeration_test.go
// These additional tests cover edge cases for rate limiter integration

func TestExtractTargetExtensionEdgeCases(t *testing.T) {
	tests := []struct {
		name     string
		data     []byte
		expected string
	}{
		// Legitimate extension extractions (additional cases)
		{
			name:     "Simple 4-digit extension",
			data:     []byte("REGISTER sip:1001@example.com SIP/2.0\r\n"),
			expected: "1001",
		},
		{
			name:     "3-digit extension",
			data:     []byte("INVITE sip:200@pbx.local SIP/2.0\r\n"),
			expected: "200",
		},
		{
			name:     "Alphanumeric short name",
			data:     []byte("INVITE sip:john@example.com SIP/2.0\r\n"),
			expected: "john",
		},
		// Should NOT extract these as extensions (domain-like or too long)
		{
			name:     "Full domain should not be extracted",
			data:     []byte("REGISTER sip:example.com SIP/2.0\r\n"),
			expected: "", // Contains a dot, filtered out
		},
		{
			name:     "Too long identifier",
			data:     []byte("INVITE sip:verylongusername@example.com SIP/2.0\r\n"),
			expected: "", // >10 chars
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			ext := ExtractTargetExtension(tt.data)
			if ext != tt.expected {
				t.Errorf("ExtractTargetExtension: got %q, want %q", ext, tt.expected)
			}
		})
	}
}

func TestParseUserAgent(t *testing.T) {
	tests := []struct {
		name     string
		data     []byte
		expected string
	}{
		{
			name: "Yealink phone",
			data: []byte("REGISTER sip:example.com SIP/2.0\r\n" +
				"User-Agent: Yealink SIP-T46S 66.86.0.15\r\n"),
			expected: "Yealink SIP-T46S 66.86.0.15",
		},
		{
			name: "Linphone",
			data: []byte("INVITE sip:alice@example.com SIP/2.0\r\n" +
				"User-Agent: Linphone/4.5.0\r\n"),
			expected: "Linphone/4.5.0",
		},
		{
			name: "No User-Agent",
			data: []byte("OPTIONS sip:example.com SIP/2.0\r\n" +
				"Via: SIP/2.0/UDP 192.168.1.1\r\n"),
			expected: "",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			ua := ParseUserAgent(tt.data)
			if ua != tt.expected {
				t.Errorf("ParseUserAgent: got %q, want %q", ua, tt.expected)
			}
		})
	}
}

func TestParseFromHeader(t *testing.T) {
	tests := []struct {
		name           string
		data           []byte
		expectedUser   string
		expectedDomain string
	}{
		{
			name: "Standard From header",
			data: []byte("INVITE sip:bob@example.com SIP/2.0\r\n" +
				"From: \"Alice\" <sip:alice@sip.example.com>;tag=1234\r\n"),
			expectedUser:   "alice",
			expectedDomain: "sip.example.com",
		},
		{
			name: "From header without display name",
			data: []byte("REGISTER sip:example.com SIP/2.0\r\n" +
				"From: <sip:1001@pbx.local>;tag=abc\r\n"),
			expectedUser:   "1001",
			expectedDomain: "pbx.local",
		},
		{
			name: "No From header",
			data: []byte("OPTIONS sip:example.com SIP/2.0\r\n" +
				"To: <sip:bob@example.com>\r\n"),
			expectedUser:   "",
			expectedDomain: "",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			user, domain := ParseFromHeader(tt.data)
			if user != tt.expectedUser {
				t.Errorf("ParseFromHeader user: got %q, want %q", user, tt.expectedUser)
			}
			if domain != tt.expectedDomain {
				t.Errorf("ParseFromHeader domain: got %q, want %q", domain, tt.expectedDomain)
			}
		})
	}
}

func TestParseToHeader(t *testing.T) {
	tests := []struct {
		name           string
		data           []byte
		expectedUser   string
		expectedDomain string
	}{
		{
			name: "Standard To header",
			data: []byte("INVITE sip:bob@example.com SIP/2.0\r\n" +
				"To: \"Bob\" <sip:bob@sip.example.com>\r\n"),
			expectedUser:   "bob",
			expectedDomain: "sip.example.com",
		},
		{
			name: "To header without display name",
			data: []byte("REGISTER sip:example.com SIP/2.0\r\n" +
				"To: <sip:5002@pbx.local>\r\n"),
			expectedUser:   "5002",
			expectedDomain: "pbx.local",
		},
		{
			name: "No To header",
			data: []byte("OPTIONS sip:example.com SIP/2.0\r\n" +
				"From: <sip:alice@example.com>\r\n"),
			expectedUser:   "",
			expectedDomain: "",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			user, domain := ParseToHeader(tt.data)
			if user != tt.expectedUser {
				t.Errorf("ParseToHeader user: got %q, want %q", user, tt.expectedUser)
			}
			if domain != tt.expectedDomain {
				t.Errorf("ParseToHeader domain: got %q, want %q", domain, tt.expectedDomain)
			}
		})
	}
}

func TestParseCallID(t *testing.T) {
	tests := []struct {
		name     string
		data     []byte
		expected string
	}{
		{
			name: "Standard Call-ID header",
			data: []byte("INVITE sip:bob@example.com SIP/2.0\r\n" +
				"Call-ID: 12345-67890@192.168.1.100\r\n"),
			expected: "12345-67890@192.168.1.100",
		},
		{
			name: "Short form Call-ID (i:)",
			data: []byte("REGISTER sip:example.com SIP/2.0\r\n" +
				"i: compact-callid@host\r\n"),
			expected: "compact-callid@host",
		},
		{
			name: "No Call-ID",
			data: []byte("OPTIONS sip:example.com SIP/2.0\r\n" +
				"From: <sip:alice@example.com>\r\n"),
			expected: "",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			callID := ParseCallID(tt.data)
			if callID != tt.expected {
				t.Errorf("ParseCallID: got %q, want %q", callID, tt.expected)
			}
		})
	}
}

// =============================================================================
// Real-world Legitimate Traffic Scenarios
// =============================================================================

func TestLegitimatePhoneRegistration(t *testing.T) {
	// Simulate a typical phone registration pattern:
	// 1. Initial REGISTER (usually 401/407 challenge)
	// 2. Second REGISTER with auth
	// 3. Keep-alive OPTIONS
	// 4. Re-REGISTER before expiry

	logger := zap.NewNop()

	// Reset global rate limiter for clean test
	rateLimiterMu.Lock()
	globalRateLimiter = nil
	rateLimiterMu.Unlock()

	rl := GetRateLimiter(logger)
	ip := "192.168.1.200"

	// Simulate pattern over time
	allowedCount := 0

	// Initial REGISTER
	if allowed, _ := rl.Allow(ip, MethodREGISTER); allowed {
		allowedCount++
	}
	// Auth REGISTER
	if allowed, _ := rl.Allow(ip, MethodREGISTER); allowed {
		allowedCount++
	}
	// Keep-alive OPTIONS (phones do this frequently)
	for i := 0; i < 5; i++ {
		if allowed, _ := rl.Allow(ip, MethodOPTIONS); allowed {
			allowedCount++
		}
	}
	// Another REGISTER
	if allowed, _ := rl.Allow(ip, MethodREGISTER); allowed {
		allowedCount++
	}

	// At minimum, the phone should complete registration (2 REGISTER + OPTIONS)
	if allowedCount < 5 {
		t.Errorf("Legitimate phone registration pattern blocked too early, only %d requests allowed", allowedCount)
	}
}

func TestLegitimateCallFlow(t *testing.T) {
	// Simulate a typical call flow:
	// INVITE -> 100 Trying -> 180 Ringing -> 200 OK -> ACK -> (call) -> BYE -> 200 OK

	logger := zap.NewNop()

	// Reset global rate limiter
	rateLimiterMu.Lock()
	globalRateLimiter = nil
	rateLimiterMu.Unlock()

	rl := GetRateLimiter(logger)
	ip := "192.168.1.201"

	// INVITE
	allowed, reason := rl.Allow(ip, MethodINVITE)
	if !allowed {
		t.Errorf("INVITE should be allowed for call: %s", reason)
	}

	// ACK (not rate limited by default)
	allowed, reason = rl.Allow(ip, MethodACK)
	if !allowed {
		t.Errorf("ACK should be allowed for call: %s", reason)
	}

	// BYE
	allowed, reason = rl.Allow(ip, MethodBYE)
	if !allowed {
		t.Errorf("BYE should be allowed for call: %s", reason)
	}
}

func TestLegitimateSubscriptionFlow(t *testing.T) {
	// Simulate presence/BLF subscription
	logger := zap.NewNop()

	// Reset global rate limiter
	rateLimiterMu.Lock()
	globalRateLimiter = nil
	rateLimiterMu.Unlock()

	rl := GetRateLimiter(logger)
	ip := "192.168.1.202"

	// SUBSCRIBE for presence (phones do multiple for BLF)
	allowedCount := 0
	for i := 0; i < 10; i++ {
		if allowed, _ := rl.Allow(ip, MethodSUBSCRIBE); allowed {
			allowedCount++
		}
	}

	// Default allows 5 burst + some refill
	if allowedCount < 5 {
		t.Errorf("Legitimate SUBSCRIBE pattern blocked too early, only %d allowed", allowedCount)
	}
}

func TestLegitimateMessaging(t *testing.T) {
	// Simulate SMS/messaging traffic
	logger := zap.NewNop()

	// Reset global rate limiter
	rateLimiterMu.Lock()
	globalRateLimiter = nil
	rateLimiterMu.Unlock()

	rl := GetRateLimiter(logger)
	ip := "192.168.1.203"

	// MESSAGE (higher limit - 100/min default)
	allowedCount := 0
	for i := 0; i < 25; i++ {
		if allowed, _ := rl.Allow(ip, MethodMESSAGE); allowed {
			allowedCount++
		}
	}

	// Should allow most messages (20 burst default)
	if allowedCount < 20 {
		t.Errorf("Legitimate MESSAGE pattern blocked too early, only %d allowed", allowedCount)
	}
}