package discovery

import (
	"log"
	"net"
	"strings"
	"testing"
	"time"

	"github.com/miekg/dns"
)

func TestDNSDiscovery_Interception(t *testing.T) {
	serviceIP := "192.0.2.100"
	upstreamDNS := []string{"8.8.8.8"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	// Test intercepting Bose service
	m := new(dns.Msg)
	m.SetQuestion("api.bose.com.", dns.TypeA)

	rw := &mockResponseWriter{}
	d.ServeDNS(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message, got nil")
	}

	if len(rw.msg.Answer) == 0 {
		t.Fatal("Expected an answer in the response")
	}

	if a, ok := rw.msg.Answer[0].(*dns.A); ok {
		if a.A.String() != serviceIP {
			t.Errorf("Expected intercepted IP %s, got %s", serviceIP, a.A.String())
		}
	} else {
		t.Errorf("Expected A record, got %T", rw.msg.Answer[0])
	}

	// Test intercepting streamingoauth.bose.com
	if !d.shouldIntercept("streamingoauth.bose.com") {
		t.Error("Expected streamingoauth.bose.com to be intercepted")
	}

	// Test aftertouch.test
	m2 := new(dns.Msg)
	m2.SetQuestion("aftertouch.test.", dns.TypeA)
	rw2 := &mockResponseWriter{}
	d.ServeDNS(rw2, m2)

	if rw2.msg == nil || len(rw2.msg.Answer) == 0 {
		t.Fatal("Expected response for aftertouch.test")
	}

	if a, ok := rw2.msg.Answer[0].(*dns.A); ok {
		if a.A.String() != serviceIP {
			t.Errorf("Expected intercepted IP %s for aftertouch.test, got %s", serviceIP, a.A.String())
		}
	} else {
		t.Errorf("Expected A record for aftertouch.test, got %T", rw2.msg.Answer[0])
	}
}

func TestDNSDiscovery_Forwarding(t *testing.T) {
	// This test is harder because it needs a real upstream or a mock.
	// For now, let's just test that it calls forward and record.
	serviceIP := "192.0.2.100"
	upstreamDNS := []string{"127.0.0.1:5353"} // Use a port that is likely closed or we can mock
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	m := new(dns.Msg)
	m.SetQuestion("google.com.", dns.TypeA)

	rw := &mockResponseWriter{}

	// Start a mock upstream DNS server
	mux := dns.NewServeMux()
	mux.HandleFunc("google.com.", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)
		_ = w.WriteMsg(m)
	})
	ts := &dns.Server{Addr: "127.0.0.1:5353", Net: "udp", Handler: mux, ReadTimeout: 100 * time.Millisecond, WriteTimeout: 100 * time.Millisecond}
	go func() {
		_ = ts.ListenAndServe()
	}()
	defer func() { _ = ts.Shutdown() }()

	// Give it a moment to start
	time.Sleep(100 * time.Millisecond)

	// We expect forward to succeed
	d.ServeDNS(rw, m)

	d.mu.RLock()
	host, exists := d.discovered["google.com"]
	d.mu.RUnlock()

	if !exists {
		t.Error("Expected google.com to be recorded in discovery")
	}
	if host.IsBoseService {
		t.Error("google.com should not be identified as a Bose service")
	}
}

func TestDNSDiscovery_StartTCP(t *testing.T) {
	serviceIP := "192.0.2.100"
	upstreamDNS := []string{"8.8.8.8"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	addr := "127.0.0.1:5354"
	go func() {
		_ = d.Start(addr)
	}()

	// Give it a moment to start
	time.Sleep(200 * time.Millisecond)

	// Test TCP resolution
	m := new(dns.Msg)
	m.SetQuestion("api.bose.com.", dns.TypeA)

	c := new(dns.Client)
	c.Net = "tcp"
	in, _, err := c.Exchange(m, addr)
	if err != nil {
		t.Fatalf("Failed to exchange via TCP: %v", err)
	}

	if len(in.Answer) == 0 {
		t.Fatal("Expected answer in TCP response")
	}

	if a, ok := in.Answer[0].(*dns.A); ok {
		if a.A.String() != serviceIP {
			t.Errorf("Expected intercepted IP %s via TCP, got %s", serviceIP, a.A.String())
		}
	} else {
		t.Errorf("Expected A record via TCP, got %T", in.Answer[0])
	}

	// Test Shutdown
	err = d.Shutdown()
	if err != nil {
		t.Errorf("Shutdown failed: %v", err)
	}

	// Verify it's really shut down by trying to connect
	_, _, err = c.Exchange(m, addr)
	if err == nil {
		t.Error("Expected error after shutdown, but could still exchange")
	}
}

func TestDNSDiscovery_SelfForwarding(t *testing.T) {
	serviceIP := "soundtouch.local"
	upstreamDNS := []string{"127.0.0.1:5357"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	// Mock upstream DNS server for soundtouch.local
	mux := dns.NewServeMux()
	mux.HandleFunc("soundtouch.local.", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)
		rr, _ := dns.NewRR("soundtouch.local. 60 IN A 192.0.2.10")
		m.Answer = append(m.Answer, rr)
		_ = w.WriteMsg(m)
	})
	ts := &dns.Server{Addr: "127.0.0.1:5357", Net: "udp", Handler: mux, ReadTimeout: 100 * time.Millisecond, WriteTimeout: 100 * time.Millisecond}
	go func() {
		_ = ts.ListenAndServe()
	}()
	defer func() { _ = ts.Shutdown() }()

	time.Sleep(100 * time.Millisecond)

	m := new(dns.Msg)
	m.SetQuestion("soundtouch.local.", dns.TypeA)
	rw := &mockResponseWriter{}
	d.ServeDNS(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response for soundtouch.local")
	}

	if rw.msg.Rcode != dns.RcodeSuccess {
		t.Errorf("Expected Success (0) for soundtouch.local being forwarded, got %d", rw.msg.Rcode)
	}

	if len(rw.msg.Answer) == 0 {
		t.Fatal("Expected an answer in the response")
	}

	if a, ok := rw.msg.Answer[0].(*dns.A); ok {
		if a.A.String() != "192.0.2.10" {
			t.Errorf("Expected IP 192.0.2.10, got %s", a.A.String())
		}
	}

	// Check if d.recordQuery logged it correctly.
	d.mu.RLock()
	host, exists := d.discovered["soundtouch.local"]
	d.mu.RUnlock()

	if !exists {
		t.Error("Expected soundtouch.local to be recorded")
	}
	// It should NOT be intercepted anymore
	if host != nil && host.IsIntercepted {
		t.Error("Expected soundtouch.local NOT to be intercepted anymore, but forwarded")
	}
}

func TestDNSDiscovery_ForwardLocal(t *testing.T) {
	serviceIP := "192.0.2.100"
	upstreamDNS := []string{"127.0.0.1:5356"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	m := new(dns.Msg)
	m.SetQuestion("someone-else.local.", dns.TypeA)
	rw := &mockResponseWriter{}

	// Start a mock upstream DNS server that returns SUCCESS for .local
	mux := dns.NewServeMux()
	mux.HandleFunc("someone-else.local.", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)
		rr, _ := dns.NewRR("someone-else.local. 60 IN A 192.0.2.50")
		m.Answer = append(m.Answer, rr)
		_ = w.WriteMsg(m)
	})
	ts := &dns.Server{Addr: "127.0.0.1:5356", Net: "udp", Handler: mux, ReadTimeout: 100 * time.Millisecond, WriteTimeout: 100 * time.Millisecond}
	go func() {
		_ = ts.ListenAndServe()
	}()
	defer func() { _ = ts.Shutdown() }()

	time.Sleep(100 * time.Millisecond)

	d.ServeDNS(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message")
	}

	if rw.msg.Rcode != dns.RcodeSuccess {
		t.Errorf("Expected Success (0) for .local being forwarded, got %d", rw.msg.Rcode)
	}

	if len(rw.msg.Answer) == 0 {
		t.Fatal("Expected an answer in the response")
	}
}

func TestDNSDiscovery_IsRunning(t *testing.T) {
	serviceIP := "192.0.2.100"
	upstreamDNS := []string{"8.8.8.8"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	addr := "127.0.0.1:5355"

	if d.IsRunning(addr) {
		t.Error("Expected IsRunning to be false before Start")
	}

	go func() {
		_ = d.Start(addr)
	}()

	// Give it a moment to start
	time.Sleep(200 * time.Millisecond)

	if !d.IsRunning(addr) {
		t.Error("Expected IsRunning to be true after Start")
	}

	if d.IsRunning("127.0.0.1:9999") {
		t.Error("Expected IsRunning to be false for wrong address")
	}

	_ = d.Shutdown()

	if d.IsRunning(addr) {
		t.Error("Expected IsRunning to be false after Shutdown")
	}
}

type mockResponseWriter struct {
	msg *dns.Msg
}

func (m *mockResponseWriter) LocalAddr() net.Addr         { return nil }
func (m *mockResponseWriter) RemoteAddr() net.Addr        { return nil }
func (m *mockResponseWriter) WriteMsg(msg *dns.Msg) error { m.msg = msg; return nil }
func (m *mockResponseWriter) Write([]byte) (int, error)   { return 0, nil }
func (m *mockResponseWriter) Close() error                { return nil }
func (m *mockResponseWriter) TsigStatus() error           { return nil }
func (m *mockResponseWriter) TsigTimersOnly(bool)         {}
func (m *mockResponseWriter) Hijack()                     {}

func TestDNSDiscovery_LogThrottling(t *testing.T) {
	d := NewDNSDiscovery([]string{"8.8.8.8"}, "192.0.2.100", "")

	// Capture log output
	var logBuf strings.Builder
	oldOutput := log.Writer()
	log.SetOutput(&logBuf)
	defer log.SetOutput(oldOutput)

	msg := "Test log message"
	d.throttledLog(msg)
	d.throttledLog(msg)
	d.throttledLog(msg)

	count := strings.Count(logBuf.String(), msg)
	if count != 1 {
		t.Errorf("Expected log message to appear once due to throttling, but appeared %d times", count)
	}

	// Advance time by 11 seconds to bypass throttling
	d.lastLogMu.Lock()
	d.lastLog[msg] = time.Now().Add(-11 * time.Second)
	d.lastLogMu.Unlock()

	d.throttledLog(msg)
	count = strings.Count(logBuf.String(), msg)
	if count != 2 {
		t.Errorf("Expected log message to appear twice after advancing time, but appeared %d times", count)
	}
}

func TestDNSDiscovery_LoopPrevention(t *testing.T) {
	serviceIP := "192.0.2.100"
	bindAddr := "127.0.0.1:53"
	upstreamDNS := []string{"127.0.0.1:53"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")
	d.bindAddr = bindAddr

	// Capture log output to avoid panic if it's being throttled/logged
	var logBuf strings.Builder
	oldOutput := log.Writer()
	log.SetOutput(&logBuf)
	defer log.SetOutput(oldOutput)

	m := new(dns.Msg)
	m.SetQuestion("google.com.", dns.TypeA)

	rw := &mockResponseWriter{}
	d.forward(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message")
	}

	if rw.msg.Rcode != dns.RcodeServerFailure {
		t.Errorf("Expected RcodeServerFailure (2), got %d", rw.msg.Rcode)
	}
}

func TestDNSDiscovery_EmptyUpstream(t *testing.T) {
	serviceIP := "192.0.2.100"
	var upstreamDNS []string // Empty upstream
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")
	d.bindAddr = ":53"

	m := new(dns.Msg)
	m.SetQuestion("google.com.", dns.TypeA)

	rw := &mockResponseWriter{}
	d.ServeDNS(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message, got nil")
	}

	if rw.msg.Rcode != dns.RcodeServerFailure {
		t.Errorf("Expected RcodeServerFailure (2) for empty upstream, got %d", rw.msg.Rcode)
	}

	// Verify log message (optional, but good to check it's the simplified one)
}

func TestDNSDiscovery_ForwardTimeout(t *testing.T) {
	serviceIP := "192.0.2.100"

	// Mock server that deliberately delays its response
	mux := dns.NewServeMux()
	mux.HandleFunc("google.com.", func(w dns.ResponseWriter, r *dns.Msg) {
		time.Sleep(200 * time.Millisecond) // Longer than the timeout
		m := new(dns.Msg)
		m.SetReply(r)
		_ = w.WriteMsg(m)
	})

	ts := &dns.Server{Addr: "127.0.0.1:5358", Net: "udp", Handler: mux}
	go func() { _ = ts.ListenAndServe() }()
	defer func() { _ = ts.Shutdown() }()

	// Give the server a moment to start
	time.Sleep(50 * time.Millisecond)

	upstreamDNS := []string{"127.0.0.1:5358"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")
	d.timeout = 100 * time.Millisecond

	m := new(dns.Msg)
	m.SetQuestion("google.com.", dns.TypeA)

	rw := &mockResponseWriter{}

	start := time.Now()
	d.forward(rw, m)
	duration := time.Since(start)

	// Since we're forwarding to a local server that sleeps for 200ms,
	// and our timeout is 100ms, it should take at least 100ms.
	if duration < 100*time.Millisecond {
		t.Errorf("Expected forward to take at least 100ms (timeout), but took %v", duration)
	}

	if rw.msg == nil || rw.msg.Rcode != dns.RcodeServerFailure {
		t.Errorf("Expected RcodeServerFailure after timeout, got msg: %v", rw.msg)
	}
}

func TestDNSDiscovery_MultipleUpstreams(t *testing.T) {
	serviceIP := "192.0.2.100"

	// Mock server 1: returns NXDOMAIN
	mux1 := dns.NewServeMux()
	mux1.HandleFunc("test.com.", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)
		m.Rcode = dns.RcodeNameError
		_ = w.WriteMsg(m)
	})
	ts1 := &dns.Server{Addr: "127.0.0.1:5356", Net: "udp", Handler: mux1}
	go func() { _ = ts1.ListenAndServe() }()
	defer func() { _ = ts1.Shutdown() }()

	// Mock server 2: succeeds
	mux2 := dns.NewServeMux()
	mux2.HandleFunc("test.com.", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)
		m.Answer = append(m.Answer, &dns.A{
			Hdr: dns.RR_Header{Name: r.Question[0].Name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 300},
			A:   net.ParseIP("1.2.3.4"),
		})
		_ = w.WriteMsg(m)
	})
	ts2 := &dns.Server{Addr: "127.0.0.1:5357", Net: "udp", Handler: mux2}
	go func() { _ = ts2.ListenAndServe() }()
	defer func() { _ = ts2.Shutdown() }()

	time.Sleep(100 * time.Millisecond)

	upstreamDNS := []string{"127.0.0.1:5356", "127.0.0.1:5357"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	m := new(dns.Msg)
	m.SetQuestion("test.com.", dns.TypeA)
	rw := &mockResponseWriter{}

	d.forward(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message")
	}

	// It should succeed because it falls back to the second upstream
	if rw.msg.Rcode != dns.RcodeSuccess {
		t.Errorf("Expected RcodeSuccess (0), got %d. Fallback failed.", rw.msg.Rcode)
	}

	if len(rw.msg.Answer) == 0 {
		t.Fatal("Expected an answer from the second upstream")
	}
}

func TestDNSDiscovery_HostnameServiceIP(t *testing.T) {
	// Use localhost which should resolve to 127.0.0.1
	serviceIP := "localhost"
	upstreamDNS := []string{"8.8.8.8"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	m := new(dns.Msg)
	m.SetQuestion("api.bose.com.", dns.TypeA)

	rw := &mockResponseWriter{}
	d.ServeDNS(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message, got nil")
	}

	if len(rw.msg.Answer) == 0 {
		t.Fatal("Expected an answer in the response")
	}

	if a, ok := rw.msg.Answer[0].(*dns.A); ok {
		// It should be resolved to 127.0.0.1 (or whatever localhost resolves to)
		if a.A.String() == "" {
			t.Error("Expected a non-empty IP address")
		}
		log.Printf("Resolved localhost to %s", a.A.String())
	} else if cname, ok := rw.msg.Answer[0].(*dns.CNAME); ok {
		// Fallback to CNAME is also acceptable if resolution failed but it shouldn't for localhost
		if cname.Target != "localhost." {
			t.Errorf("Expected CNAME to localhost., got %s", cname.Target)
		}
	} else {
		t.Errorf("Expected A or CNAME record, got %T", rw.msg.Answer[0])
	}
}

func TestDNSDiscovery_UnresolvableHostname(t *testing.T) {
	// Use a likely unresolvable hostname
	serviceIP := "this.hostname.does.not.exist.at.all.invalid"
	upstreamDNS := []string{"8.8.8.8"}
	d := NewDNSDiscovery(upstreamDNS, serviceIP, "")

	m := new(dns.Msg)
	m.SetQuestion("api.bose.com.", dns.TypeA)

	rw := &mockResponseWriter{}
	d.ServeDNS(rw, m)

	if rw.msg == nil {
		t.Fatal("Expected a response message, got nil")
	}

	if len(rw.msg.Answer) == 0 {
		t.Fatal("Expected an answer in the response (CNAME fallback)")
	}

	if cname, ok := rw.msg.Answer[0].(*dns.CNAME); ok {
		expected := serviceIP + "."
		if cname.Target != expected {
			t.Errorf("Expected CNAME to %s, got %s", expected, cname.Target)
		}
	} else {
		t.Errorf("Expected CNAME record for unresolvable hostname, got %T", rw.msg.Answer[0])
	}
}

// mockResponseWriterWithAddr is like mockResponseWriter but returns a
// configurable remote address; used to simulate queries from speaker IPs.
type mockResponseWriterWithAddr struct {
	mockResponseWriter
	remote net.Addr
}

func (m *mockResponseWriterWithAddr) RemoteAddr() net.Addr { return m.remote }

// mockUDPAddr implements net.Addr for test purposes.
type mockUDPAddr struct{ addr string }

func (a *mockUDPAddr) Network() string { return "udp" }
func (a *mockUDPAddr) String() string  { return a.addr }

func TestDNSDiscovery_InterceptClientTracking_NonLoopback(t *testing.T) {
	d := NewDNSDiscovery([]string{"8.8.8.8"}, "192.0.2.100", "")

	// Query for an intercepted Bose hostname from a non-loopback address.
	msg := new(dns.Msg)
	msg.SetQuestion("content.api.bose.io.", dns.TypeA)

	rw := &mockResponseWriterWithAddr{
		remote: &mockUDPAddr{addr: "10.1.103.209:54321"},
	}
	d.ServeDNS(rw, msg)

	clients := d.InterceptClientIPs()
	if _, ok := clients["10.1.103.209"]; !ok {
		t.Errorf("expected 10.1.103.209 in interceptClients, got %v", clients)
	}
}

func TestDNSDiscovery_InterceptClientTracking_LoopbackExcluded(t *testing.T) {
	d := NewDNSDiscovery([]string{"8.8.8.8"}, "192.0.2.100", "")

	// Query for an intercepted hostname from loopback (health-probe scenario).
	msg := new(dns.Msg)
	msg.SetQuestion("api.bose.com.", dns.TypeA)

	rw := &mockResponseWriterWithAddr{
		remote: &mockUDPAddr{addr: "127.0.0.1:55069"},
	}
	d.ServeDNS(rw, msg)

	clients := d.InterceptClientIPs()
	if len(clients) != 0 {
		t.Errorf("expected no clients (loopback should be excluded), got %v", clients)
	}
}

func TestDNSDiscovery_InterceptClientTracking_NonInterceptedNotRecorded(t *testing.T) {
	// Forwarded (non-intercepted) queries should not populate interceptClients.
	upstreamMux := dns.NewServeMux()
	upstreamMux.HandleFunc("google.com.", func(w dns.ResponseWriter, r *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(r)
		_ = w.WriteMsg(m)
	})
	ts := &dns.Server{Addr: "127.0.0.1:5360", Net: "udp", Handler: upstreamMux,
		ReadTimeout: 100 * time.Millisecond, WriteTimeout: 100 * time.Millisecond}
	go func() { _ = ts.ListenAndServe() }()
	defer func() { _ = ts.Shutdown() }()
	time.Sleep(100 * time.Millisecond)

	d := NewDNSDiscovery([]string{"127.0.0.1:5360"}, "192.0.2.100", "")

	msg := new(dns.Msg)
	msg.SetQuestion("google.com.", dns.TypeA)

	rw := &mockResponseWriterWithAddr{
		remote: &mockUDPAddr{addr: "10.1.103.209:54321"},
	}
	d.ServeDNS(rw, msg)

	clients := d.InterceptClientIPs()
	if len(clients) != 0 {
		t.Errorf("expected no intercept clients for non-intercepted query, got %v", clients)
	}
}