package station_test

import (
	"crypto/tls"
	"encoding/binary"
	"encoding/json"
	"io"
	"net"
	"os"
	"sync"
	"testing"
	"time"

	"gitea.neitzel.de/konrad/funknetz/station"
)

type fakeClock struct {
	mu      sync.Mutex
	now     time.Time
	waiters []*fakeWaiter
	gen     int
}

type fakeWaiter struct {
	deadline time.Time
	ch       chan time.Time
	done     bool
}

func newFakeClock() *fakeClock {
	return &fakeClock{now: time.Date(2026, 10, 3, 12, 0, 0, 0, time.UTC)}
}

func (c *fakeClock) Now() time.Time {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.now
}

func (c *fakeClock) NewTimer(d time.Duration) station.Timer {
	c.mu.Lock()
	defer c.mu.Unlock()
	if d < 0 {
		d = 0
	}
	ch := make(chan time.Time, 1)
	c.gen++
	w := &fakeWaiter{deadline: c.now.Add(d), ch: ch}
	if d == 0 {
		ch <- c.now
		w.done = true
		return &fakeTimer{c: c, w: w}
	}
	c.waiters = append(c.waiters, w)
	return &fakeTimer{c: c, w: w}
}

func (c *fakeClock) Advance(d time.Duration) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.now = c.now.Add(d)
	kept := c.waiters[:0]
	for _, w := range c.waiters {
		if w.done {
			continue
		}
		if !w.deadline.After(c.now) {
			w.done = true
			w.ch <- c.now
			continue
		}
		kept = append(kept, w)
	}
	c.waiters = kept
}

func (c *fakeClock) Generation() int {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.gen
}

func waitClock(t *testing.T, c *fakeClock, after int) {
	t.Helper()
	deadline := time.Now().Add(2 * time.Second)
	for c.Generation() <= after {
		if time.Now().After(deadline) {
			t.Fatal("station did not rearm the clock")
		}
		time.Sleep(time.Millisecond)
	}
}

func (c *fakeClock) BlockUntilWaiting(t *testing.T) {
	t.Helper()
	deadline := time.Now().Add(2 * time.Second)
	for {
		c.mu.Lock()
		n := 0
		for _, w := range c.waiters {
			if !w.done {
				n++
			}
		}
		c.mu.Unlock()
		if n > 0 {
			return
		}
		if time.Now().After(deadline) {
			t.Fatal("station did not wait on the clock")
		}
		time.Sleep(time.Millisecond)
	}
}

type fakeTimer struct {
	c *fakeClock
	w *fakeWaiter
}

func (t *fakeTimer) C() <-chan time.Time { return t.w.ch }

func (t *fakeTimer) Stop() bool {
	t.c.mu.Lock()
	defer t.c.mu.Unlock()
	if t.w.done {
		return false
	}
	t.w.done = true
	return true
}

type reflector struct {
	ln   net.Listener
	udp  *net.UDPConn
	tcp  net.Conn
	tls  *tls.Conn
	peer *net.UDPAddr
	port int
}

func (r *reflector) conn() net.Conn {
	if r.tls != nil {
		return r.tls
	}
	return r.tcp
}

func newReflector(t *testing.T) *reflector {
	t.Helper()
	var ln net.Listener
	var udp *net.UDPConn
	var port int
	for range 8 {
		var err error
		ln, err = net.Listen("tcp", "127.0.0.1:0")
		if err != nil {
			t.Fatal(err)
		}
		port = ln.Addr().(*net.TCPAddr).Port
		udp, err = net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: port})
		if err == nil {
			break
		}
		ln.Close()
		ln = nil
	}
	if udp == nil {
		t.Fatal("udp port stayed in use")
	}
	t.Cleanup(func() {
		if ln != nil {
			ln.Close()
		}
		udp.Close()
	})
	return &reflector{ln: ln, udp: udp, port: port}
}

func (r *reflector) accept(t *testing.T) {
	t.Helper()
	r.ln.(*net.TCPListener).SetDeadline(time.Now().Add(2 * time.Second))
	conn, err := r.ln.Accept()
	if err != nil {
		t.Fatal(err)
	}
	r.tcp = conn
	r.tls = nil
	t.Cleanup(func() { conn.Close() })
}

func (r *reflector) readFrame(t *testing.T) (uint16, []byte) {
	t.Helper()
	conn := r.conn()
	if err := conn.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
		t.Fatal(err)
	}
	var hdr [4]byte
	if _, err := io.ReadFull(conn, hdr[:]); err != nil {
		t.Fatal(err)
	}
	n := binary.BigEndian.Uint32(hdr[:])
	if n > 32768 {
		t.Fatalf("frame length %d", n)
	}
	buf := make([]byte, n)
	if _, err := io.ReadFull(conn, buf); err != nil {
		t.Fatal(err)
	}
	if len(buf) < 2 {
		t.Fatalf("short frame %d", len(buf))
	}
	return binary.BigEndian.Uint16(buf[:2]), buf[2:]
}

func (r *reflector) writeFrame(t *testing.T, typ uint16, body []byte) {
	t.Helper()
	payload := make([]byte, 2+len(body))
	binary.BigEndian.PutUint16(payload, typ)
	copy(payload[2:], body)
	var hdr [4]byte
	binary.BigEndian.PutUint32(hdr[:], uint32(len(payload)))
	conn := r.conn()
	if err := conn.SetWriteDeadline(time.Now().Add(2 * time.Second)); err != nil {
		t.Fatal(err)
	}
	if _, err := conn.Write(append(hdr[:], payload...)); err != nil {
		t.Fatal(err)
	}
}

func (r *reflector) handshake(t *testing.T, cfg *tls.Config) error {
	t.Helper()
	r.tls = tls.Server(r.tcp, cfg)
	if err := r.tls.SetDeadline(time.Now().Add(2 * time.Second)); err != nil {
		return err
	}
	err := r.tls.Handshake()
	_ = r.tls.SetDeadline(time.Time{})
	if err != nil {
		r.tls = nil
	}
	return err
}

func (r *reflector) readUDP(t *testing.T) (typ, id, seq uint16, body []byte) {
	t.Helper()
	if err := r.udp.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
		t.Fatal(err)
	}
	buf := make([]byte, 2048)
	n, addr, err := r.udp.ReadFromUDP(buf)
	if err != nil {
		t.Fatal(err)
	}
	r.peer = addr
	if n < 6 {
		t.Fatalf("short datagram %d", n)
	}
	typ = binary.BigEndian.Uint16(buf[0:2])
	id = binary.BigEndian.Uint16(buf[2:4])
	seq = binary.BigEndian.Uint16(buf[4:6])
	body = append([]byte(nil), buf[6:n]...)
	return typ, id, seq, body
}

func (r *reflector) readRawUDP(t *testing.T) []byte {
	t.Helper()
	if err := r.udp.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
		t.Fatal(err)
	}
	buf := make([]byte, 2048)
	n, addr, err := r.udp.ReadFromUDP(buf)
	if err != nil {
		t.Fatal(err)
	}
	r.peer = addr
	return append([]byte(nil), buf[:n]...)
}

func (r *reflector) writeRawUDP(t *testing.T, pkt []byte) {
	t.Helper()
	if r.peer == nil {
		t.Fatal("no udp peer")
	}
	if err := r.udp.SetWriteDeadline(time.Now().Add(2 * time.Second)); err != nil {
		t.Fatal(err)
	}
	if _, err := r.udp.WriteToUDP(pkt, r.peer); err != nil {
		t.Fatal(err)
	}
}

func (r *reflector) writeUDP(t *testing.T, typ, id, seq uint16, body []byte) {
	t.Helper()
	if r.peer == nil {
		t.Fatal("no udp peer")
	}
	buf := make([]byte, 6+len(body))
	binary.BigEndian.PutUint16(buf[0:2], typ)
	binary.BigEndian.PutUint16(buf[2:4], id)
	binary.BigEndian.PutUint16(buf[4:6], seq)
	copy(buf[6:], body)
	if err := r.udp.SetWriteDeadline(time.Now().Add(2 * time.Second)); err != nil {
		t.Fatal(err)
	}
	if _, err := r.udp.WriteToUDP(buf, r.peer); err != nil {
		t.Fatal(err)
	}
}

func appendU16(b []byte, v uint16) []byte {
	var buf [2]byte
	binary.BigEndian.PutUint16(buf[:], v)
	return append(b, buf[:]...)
}

func appendU32(b []byte, v uint32) []byte {
	var buf [4]byte
	binary.BigEndian.PutUint32(buf[:], v)
	return append(b, buf[:]...)
}

func appendStr(b []byte, s string) []byte {
	b = appendU16(b, uint16(len(s)))
	return append(b, s...)
}

func appendBytes(b []byte, p []byte) []byte {
	b = appendU16(b, uint16(len(p)))
	return append(b, p...)
}

func takeU16(t *testing.T, b []byte) (uint16, []byte) {
	t.Helper()
	if len(b) < 2 {
		t.Fatalf("need 2 bytes, have %d", len(b))
	}
	return binary.BigEndian.Uint16(b[:2]), b[2:]
}

func takeU32(t *testing.T, b []byte) (uint32, []byte) {
	t.Helper()
	if len(b) < 4 {
		t.Fatalf("need 4 bytes, have %d", len(b))
	}
	return binary.BigEndian.Uint32(b[:4]), b[4:]
}

func requireSoftwareIdentity(t *testing.T, body []byte) {
	t.Helper()
	raw, rest := takeStr(t, body)
	if len(rest) != 0 {
		t.Fatalf("software identity has %d trailing bytes", len(rest))
	}
	var got map[string]string
	if err := json.Unmarshal([]byte(raw), &got); err != nil {
		t.Fatalf("software identity %q: %v", raw, err)
	}
	if len(got) != 3 || got["sw"] != station.SoftwareName || got["swVer"] != station.SoftwareVersion || got["projVer"] != station.SoftwareVersion {
		t.Fatalf("software identity = %#v, want sw, swVer, and projVer %q", got, station.SoftwareName)
	}
	if _, ok := got["machineArch"]; ok {
		t.Fatal("protocol 2.0 node information includes machineArch")
	}
}

func takeStr(t *testing.T, b []byte) (string, []byte) {
	t.Helper()
	n, rest := takeU16(t, b)
	if len(rest) < int(n) {
		t.Fatalf("string needs %d bytes, have %d", n, len(rest))
	}
	return string(rest[:n]), rest[n:]
}

func takeBytes(t *testing.T, b []byte) ([]byte, []byte) {
	t.Helper()
	n, rest := takeU16(t, b)
	if len(rest) < int(n) {
		t.Fatalf("bytes need %d, have %d", n, len(rest))
	}
	return append([]byte(nil), rest[:n]...), rest[n:]
}

func serverInfo(clientID uint16, nodes, codecs []string) []byte {
	b := appendU16(nil, 0)
	b = appendU16(b, clientID)
	b = appendU16(b, uint16(len(nodes)))
	for _, n := range nodes {
		b = appendStr(b, n)
	}
	b = appendU16(b, uint16(len(codecs)))
	for _, c := range codecs {
		b = appendStr(b, c)
	}
	return b
}

func writeConfigFile(t *testing.T, body string) string {
	t.Helper()
	path := t.TempDir() + "/funknetz.json"
	if err := os.WriteFile(path, []byte(body), 0o600); err != nil {
		t.Fatal(err)
	}
	return path
}