package e2e

import (
	"context"
	"fmt"
	"io"
	"net"
	"testing"
	"time"

	"github.com/iceBear67/redapricot/client"
)

// startClient builds and starts an in-process client against the hub, with the
// given mappings, returning the running client.
func startClient(t *testing.T, hubAddr, psk string, maxTunnels int, mappings []client.Mapping) *client.Client {
	t.Helper()
	return startClientWithPing(t, hubAddr, psk, maxTunnels, 20000, mappings)
}

// startClientWithPing is startClient with an explicit heartbeat interval, for
// tests that need liveness detection to trigger quickly.
func startClientWithPing(t *testing.T, hubAddr, psk string, maxTunnels, pingMs int, mappings []client.Mapping) *client.Client {
	t.Helper()
	return startClientCfg(t, &client.Config{
		Server:         hubAddr,
		PSK:            psk,
		MaxTunnels:     maxTunnels,
		PingIntervalMs: pingMs,
		Mappings:       mappings,
	})
}

// startClientCfg runs an in-process client from a fully-specified config, for
// tests that need a knob the shorthand helpers do not expose.
func startClientCfg(t *testing.T, cfg *client.Config) *client.Client {
	t.Helper()
	c := client.New(cfg)
	ctx, cancel := context.WithCancel(context.Background())
	t.Cleanup(func() {
		cancel()
		c.Close()
	})
	if err := c.Start(ctx); err != nil {
		t.Fatalf("client start: %v", err)
	}
	// Give the control-session registration a moment to reach the hub.
	time.Sleep(200 * time.Millisecond)
	return c
}

// TestRoundTrip verifies the full path plus verbatim handshake forwarding and
// case-insensitive pattern matching.
func TestRoundTrip(t *testing.T) {
	const psk = "e2e-roundtrip"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	startClient(t, hubAddr, psk, 4, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr},
	})

	// The player connects using mixed case; the hub matches case-insensitively
	// but forwards the address verbatim.
	pc := dialPlayer(t, hubAddr, "MC.Local")
	defer pc.Close()
	playerEcho(t, pc, []byte("hello redapricot"))

	ev := dest.waitEvent(t, 5*time.Second)
	if ev.handshakeAddr != "MC.Local" {
		t.Fatalf("destination saw handshake address %q, want verbatim %q", ev.handshakeAddr, "MC.Local")
	}
	if ev.hasProxy {
		t.Fatalf("did not expect a PROXY header for a non-proxy mapping")
	}
}

// TestRegexPatternMatch verifies a wildcard regex pattern routes a matching
// player (whole-hostname, case-insensitive) and drops a non-matching one, and
// that the client maps the hub-echoed pattern back to its destination.
func TestRegexPatternMatch(t *testing.T) {
	const psk = "e2e-regex"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	startClient(t, hubAddr, psk, 2, []client.Mapping{
		{Pattern: `mc\d+\.local`, Destination: dest.addr},
	})

	// Matches the regex (digit wildcard, mixed case); the whole hostname matches.
	pc := dialPlayer(t, hubAddr, "MC7.Local")
	defer pc.Close()
	playerEcho(t, pc, []byte("regex hello"))
	ev := dest.waitEvent(t, 5*time.Second)
	if ev.handshakeAddr != "MC7.Local" {
		t.Fatalf("destination saw handshake address %q, want verbatim %q", ev.handshakeAddr, "MC7.Local")
	}

	// A host that does not fully match the pattern is dropped ('\d+' needs a digit).
	pc2 := dialPlayer(t, hubAddr, "mc.local")
	defer pc2.Close()
	_ = pc2.SetReadDeadline(time.Now().Add(3 * time.Second))
	if _, err := pc2.Read(make([]byte, 16)); err == nil {
		t.Fatalf("expected the hub to drop a host that does not match the regex")
	}
}

// TestLargeTransfer pushes a multi-megabyte payload both ways to exercise
// framing and back-pressure.
func TestLargeTransfer(t *testing.T) {
	const psk = "e2e-large"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	startClient(t, hubAddr, psk, 2, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr},
	})

	pc := dialPlayer(t, hubAddr, "mc.local")
	defer pc.Close()

	payload := make([]byte, 3*1024*1024)
	for i := range payload {
		payload[i] = byte(i*31 + 7)
	}
	// Write from a goroutine while reading back concurrently to avoid deadlock.
	writeErr := make(chan error, 1)
	go func() {
		_, err := pc.Write(payload)
		writeErr <- err
	}()
	got := make([]byte, len(payload))
	_ = pc.SetReadDeadline(time.Now().Add(30 * time.Second))
	if _, err := io.ReadFull(pc, got); err != nil {
		t.Fatalf("read large echo: %v", err)
	}
	if err := <-writeErr; err != nil {
		t.Fatalf("write large payload: %v", err)
	}
	for i := range payload {
		if got[i] != payload[i] {
			t.Fatalf("large echo mismatch at byte %d", i)
		}
	}
}

// TestEachPlayerGetsOwnWorker confirms the 1:1 rule: N concurrent players
// produce N worker connections, and the maxTunnels cap is honoured.
func TestEachPlayerGetsOwnWorker(t *testing.T) {
	const psk = "e2e-concurrent"
	const n = 8
	const maxTunnels = 16
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	c := startClient(t, hubAddr, psk, maxTunnels, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr},
	})

	conns := make([]net.Conn, 0, n)
	defer func() {
		for _, pc := range conns {
			_ = pc.Close()
		}
	}()
	for i := 0; i < n; i++ {
		pc := dialPlayer(t, hubAddr, "mc.local")
		playerEcho(t, pc, []byte(fmt.Sprintf("hello-%d", i)))
		conns = append(conns, pc)
	}

	got := c.WorkerConnCount()
	if got != n {
		t.Fatalf("expected %d worker conns for %d players, got %d", n, n, got)
	}
	if got > maxTunnels {
		t.Fatalf("worker conns %d exceed maxTunnels %d", got, maxTunnels)
	}
	t.Logf("%d players on %d worker conn(s)", n, got)
}

// TestProxyProtocol checks that the client prepends a correct HAProxy v2 header
// carrying the player's real source address.
func TestProxyProtocol(t *testing.T) {
	const psk = "e2e-proxy"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	startClient(t, hubAddr, psk, 2, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr, ProxyProtocol: true},
	})

	pc := dialPlayer(t, hubAddr, "mc.local")
	defer pc.Close()
	playerEcho(t, pc, []byte("proxied hello"))

	ev := dest.waitEvent(t, 5*time.Second)
	if !ev.hasProxy {
		t.Fatalf("expected a PROXY v2 header")
	}
	localPort := pc.LocalAddr().(*net.TCPAddr).Port
	if ev.proxy.srcPort != localPort {
		t.Fatalf("proxy src port %d, want player local port %d", ev.proxy.srcPort, localPort)
	}
	if !ev.proxy.srcIP.IsLoopback() {
		t.Fatalf("proxy src ip %v, want loopback", ev.proxy.srcIP)
	}
	t.Logf("PROXY v2: src=%v:%d dst=%v:%d", ev.proxy.srcIP, ev.proxy.srcPort, ev.proxy.dstIP, ev.proxy.dstPort)
}

// TestPlayerDisconnectPropagates: player closing → hub FIN → destination EOF.
func TestPlayerDisconnectPropagates(t *testing.T) {
	const psk = "e2e-disc"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	startClient(t, hubAddr, psk, 2, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr},
	})

	pc := dialPlayer(t, hubAddr, "mc.local")
	playerEcho(t, pc, []byte("bye soon"))
	_ = pc.Close()

	select {
	case <-dest.connClosed:
	case <-time.After(5 * time.Second):
		t.Fatalf("destination did not observe the player disconnect")
	}
}

// TestDestinationDisconnectPropagates: destination closing → client FIN → player EOF.
func TestDestinationDisconnectPropagates(t *testing.T) {
	const psk = "e2e-destclose"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEchoOnceClose)
	startClient(t, hubAddr, psk, 2, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr},
	})

	pc := dialPlayer(t, hubAddr, "mc.local")
	defer pc.Close()
	payload := []byte("one shot")
	if _, err := pc.Write(payload); err != nil {
		t.Fatalf("write: %v", err)
	}
	got := make([]byte, len(payload))
	_ = pc.SetReadDeadline(time.Now().Add(5 * time.Second))
	if _, err := io.ReadFull(pc, got); err != nil {
		t.Fatalf("read echo: %v", err)
	}
	// Destination has now closed; the player's next read must reach EOF.
	_ = pc.SetReadDeadline(time.Now().Add(5 * time.Second))
	if _, err := pc.Read(make([]byte, 16)); err == nil {
		t.Fatalf("expected EOF after destination closed")
	}
}

// TestBadPSK: a client with the wrong PSK cannot establish a control session.
func TestBadPSK(t *testing.T) {
	const psk = "e2e-correct"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)

	cfg := &client.Config{
		Server:         hubAddr,
		PSK:            "totally-wrong",
		MaxTunnels:     2,
		PingIntervalMs: 20000,
		Mappings:       []client.Mapping{{Pattern: "mc.local", Destination: dest.addr}},
	}
	c := client.New(cfg)
	ctx, cancel := context.WithCancel(context.Background())
	defer func() { cancel(); c.Close() }()
	if err := c.Start(ctx); err == nil {
		t.Fatalf("expected control session to fail with a wrong PSK")
	}
}

// TestUnmatchedPattern: a player using an unregistered address is dropped.
func TestUnmatchedPattern(t *testing.T) {
	const psk = "e2e-nomatch"
	port := freePort(t)
	hubAddr := fmt.Sprintf("127.0.0.1:%d", port)
	startHub(t, port, psk)
	dest := newMockDest(t, modeEcho)
	startClient(t, hubAddr, psk, 2, []client.Mapping{
		{Pattern: "mc.local", Destination: dest.addr},
	})

	pc := dialPlayer(t, hubAddr, "unknown.host")
	defer pc.Close()
	_ = pc.SetReadDeadline(time.Now().Add(5 * time.Second))
	if _, err := pc.Read(make([]byte, 16)); err == nil {
		t.Fatalf("expected the hub to drop an unmatched player")
	}
}