package ircserver_test

import (
	"bufio"
	"database/sql"
	"fmt"
	"log/slog"
	"net"
	"os"
	"strings"
	"testing"
	"time"

	"git.eeqj.de/sneak/neoirc/internal/broker"
	"git.eeqj.de/sneak/neoirc/internal/config"
	"git.eeqj.de/sneak/neoirc/internal/db"
	"git.eeqj.de/sneak/neoirc/internal/ircserver"

	_ "modernc.org/sqlite"
)

const testTimeout = 5 * time.Second

func TestMain(m *testing.M) {
	db.SetBcryptCost(4)

	os.Exit(m.Run())
}

// testEnv holds the shared test infrastructure.
type testEnv struct {
	database *db.Database
	brk      *broker.Broker
	cfg      *config.Config
	srv      *ircserver.Server
}

func newTestEnv(t *testing.T) *testEnv {
	t.Helper()

	dsn := fmt.Sprintf(
		"file:%s?mode=memory&cache=shared&_journal_mode=WAL",
		t.Name(),
	)

	conn, err := sql.Open("sqlite", dsn)
	if err != nil {
		t.Fatalf("open db: %v", err)
	}

	conn.SetMaxOpenConns(1)

	_, err = conn.ExecContext(
		t.Context(), "PRAGMA foreign_keys = ON",
	)
	if err != nil {
		t.Fatalf("pragma: %v", err)
	}

	database := db.NewTestDatabaseFromConn(conn)

	err = database.RunMigrations(t.Context())
	if err != nil {
		t.Fatalf("migrate: %v", err)
	}

	brk := broker.New()

	cfg := &config.Config{ //nolint:exhaustruct
		ServerName: "test.irc",
		MOTD:       "Welcome to test IRC",
	}

	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("listen: %v", err)
	}

	addr := listener.Addr().String()

	err = listener.Close()
	if err != nil {
		t.Fatalf("close listener: %v", err)
	}

	log := slog.New(slog.NewTextHandler(
		os.Stderr,
		&slog.HandlerOptions{Level: slog.LevelError}, //nolint:exhaustruct
	))

	srv := ircserver.NewTestServer(log, cfg, database, brk)

	err = srv.Start(addr)
	if err != nil {
		t.Fatalf("start irc server: %v", err)
	}

	t.Cleanup(func() {
		srv.Stop()

		err := conn.Close()
		if err != nil {
			t.Logf("close db: %v", err)
		}
	})

	return &testEnv{
		database: database,
		brk:      brk,
		cfg:      cfg,
		srv:      srv,
	}
}

// dial connects to the test server.
func (env *testEnv) dial(t *testing.T) *testClient {
	t.Helper()

	conn, err := net.DialTimeout(
		"tcp",
		env.srv.Listener().Addr().String(),
		testTimeout,
	)
	if err != nil {
		t.Fatalf("dial: %v", err)
	}

	t.Cleanup(func() {
		err := conn.Close()
		if err != nil {
			t.Logf("close conn: %v", err)
		}
	})

	return &testClient{
		t:       t,
		conn:    conn,
		scanner: bufio.NewScanner(conn),
	}
}

// testClient wraps a raw TCP connection with helpers.
type testClient struct {
	t       *testing.T
	conn    net.Conn
	scanner *bufio.Scanner
}

func (tc *testClient) send(line string) {
	tc.t.Helper()

	_ = tc.conn.SetWriteDeadline(
		time.Now().Add(testTimeout),
	)

	_, err := fmt.Fprintf(tc.conn, "%s\r\n", line)
	if err != nil {
		tc.t.Fatalf("send: %v", err)
	}
}

func (tc *testClient) readLine() string {
	tc.t.Helper()

	_ = tc.conn.SetReadDeadline(
		time.Now().Add(testTimeout),
	)

	if !tc.scanner.Scan() {
		err := tc.scanner.Err()
		if err != nil {
			tc.t.Fatalf("read: %v", err)
		}

		tc.t.Fatal("connection closed unexpectedly")
	}

	return tc.scanner.Text()
}

// readUntil reads lines until one matches the predicate.
func (tc *testClient) readUntil(
	pred func(string) bool,
) []string {
	tc.t.Helper()

	var lines []string

	for {
		line := tc.readLine()
		lines = append(lines, line)

		if pred(line) {
			return lines
		}
	}
}

// register sends NICK + USER and reads through the welcome
// burst.
func (tc *testClient) register(nick string) []string {
	tc.t.Helper()

	tc.send("NICK " + nick)
	tc.send("USER " + nick + " 0 * :Test User")

	return tc.readUntil(func(line string) bool {
		return strings.Contains(line, " 376 ") ||
			strings.Contains(line, " 422 ")
	})
}

// assertContains checks that at least one line matches the
// given substring.
func assertContains(
	t *testing.T,
	lines []string,
	substr, description string,
) {
	t.Helper()

	for _, line := range lines {
		if strings.Contains(line, substr) {
			return
		}
	}

	t.Errorf("did not find %q in output: %s", substr, description)
}

// joinAndDrain joins a channel and reads until
// RPL_ENDOFNAMES.
func (tc *testClient) joinAndDrain(channel string) {
	tc.t.Helper()

	tc.send("JOIN " + channel)

	tc.readUntil(func(line string) bool {
		return strings.Contains(line, " 366 ")
	})
}

// sendAndExpect sends a command and reads until a line
// containing the expected substring is found.
func (tc *testClient) sendAndExpect(
	cmd, expect string,
) []string {
	tc.t.Helper()

	tc.send(cmd)

	return tc.readUntil(func(line string) bool {
		return strings.Contains(line, expect)
	})
}

func TestRegistration(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	lines := client.register("alice")
	assertContains(t, lines, " 001 ", "RPL_WELCOME")
}

func TestWelcomeContainsNick(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	lines := client.register("bob")

	for _, line := range lines {
		if strings.Contains(line, " 001 ") &&
			!strings.Contains(line, "bob") {
			t.Errorf("001 should contain nick: %s", line)
		}
	}
}

func TestPingPong(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("pingtest")
	lines := client.sendAndExpect("PING :hello", "PONG")
	assertContains(t, lines, "PONG", "PONG response")
}

func TestJoinChannel(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("joiner")
	client.send("JOIN #test")

	lines := client.readUntil(func(line string) bool {
		return strings.Contains(line, " 366 ")
	})

	assertContains(t, lines, "JOIN", "JOIN echo")
	assertContains(t, lines, " 366 ", "RPL_ENDOFNAMES")
}

func TestPrivmsgBetweenClients(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)

	alice := env.dial(t)
	alice.register("alice_pm")

	bob := env.dial(t)
	bob.register("bob_pm")

	alice.joinAndDrain("#chat")
	bob.joinAndDrain("#chat")

	alice.send("PRIVMSG #chat :hello bob!")
	lines := bob.sendAndExpect("PING :sync", "hello bob!")
	assertContains(t, lines, "hello bob!", "channel PRIVMSG")
}

func TestNickChange(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("oldnick")
	lines := client.sendAndExpect("NICK newnick", "newnick")
	assertContains(t, lines, "NICK", "NICK change echo")
}

func TestDuplicateNick(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)

	first := env.dial(t)
	first.register("taken")

	second := env.dial(t)
	second.send("NICK taken")
	second.send("USER taken 0 * :Test")

	lines := second.readUntil(func(line string) bool {
		return strings.Contains(line, " 433 ")
	})

	assertContains(t, lines, " 433 ", "ERR_NICKNAMEINUSE")
}

func TestListChannels(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("lister")
	client.joinAndDrain("#listtest")
	lines := client.sendAndExpect("LIST", " 323 ")
	assertContains(t, lines, " 323 ", "RPL_LISTEND") //nolint:misspell // IRC term
}

func TestWhois(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("whoistest")
	lines := client.sendAndExpect(
		"WHOIS whoistest", " 318 ",
	)

	assertContains(t, lines, " 311 ", "RPL_WHOISUSER")
	assertContains(t, lines, " 318 ", "RPL_ENDOFWHOIS")
}

func TestQuit(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("quitter")
	lines := client.sendAndExpect(
		"QUIT :goodbye", "ERROR",
	)

	assertContains(t, lines, "goodbye", "QUIT reason")
}

func TestTopicSetAndGet(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("topicuser")
	client.joinAndDrain("#topictest")
	lines := client.sendAndExpect(
		"TOPIC #topictest :New topic here",
		"New topic here",
	)

	assertContains(
		t, lines, "New topic here", "TOPIC echo",
	)
}

func TestUnknownCommand(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("unknowncmd")
	lines := client.sendAndExpect("FOOBAR", " 421 ")
	assertContains(t, lines, " 421 ", "ERR_UNKNOWNCOMMAND")
}

func TestDirectMessage(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)

	sender := env.dial(t)
	sender.register("dmsender")

	receiver := env.dial(t)
	receiver.register("dmreceiver")

	// Give relay goroutines time to start.
	time.Sleep(100 * time.Millisecond)

	sender.send("PRIVMSG dmreceiver :hello privately")

	lines := receiver.readUntil(func(line string) bool {
		return strings.Contains(line, "hello privately")
	})

	assertContains(
		t, lines, "hello privately", "direct PRIVMSG",
	)
}

func TestCAPNegotiation(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.send("CAP LS 302")

	line := client.readLine()
	if !strings.Contains(line, "CAP") {
		t.Errorf("expected CAP response, got: %s", line)
	}

	client.send("CAP END")
	lines := client.register("capuser")
	assertContains(t, lines, " 001 ", "registration after CAP")
}

func TestPartChannel(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("parter")
	client.joinAndDrain("#parttest")
	lines := client.sendAndExpect(
		"PART #parttest :leaving", "PART",
	)

	assertContains(t, lines, "#parttest", "PART echo")
}

func TestModeQuery(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("modeuser")
	client.joinAndDrain("#modetest")
	lines := client.sendAndExpect(
		"MODE #modetest", " 324 ",
	)

	assertContains(
		t, lines, " 324 ", "RPL_CHANNELMODEIS",
	)
}

func TestWhoChannel(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("whouser")
	client.joinAndDrain("#whotest")
	lines := client.sendAndExpect("WHO #whotest", " 315 ")
	assertContains(t, lines, " 352 ", "RPL_WHOREPLY")
}

func TestLusers(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("luseruser")
	lines := client.sendAndExpect("LUSERS", " 255 ")
	assertContains(t, lines, " 251 ", "RPL_LUSERCLIENT")
}

func TestMotd(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("motduser")
	lines := client.sendAndExpect("MOTD", " 376 ")
	assertContains(t, lines, " 376 ", "RPL_ENDOFMOTD")
}

func TestAwaySetAndClear(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("awayuser")

	setLines := client.sendAndExpect(
		"AWAY :brb lunch", " 306 ",
	)
	assertContains(t, setLines, " 306 ", "RPL_NOWAWAY")

	clearLines := client.sendAndExpect("AWAY", " 305 ")
	assertContains(t, clearLines, " 305 ", "RPL_UNAWAY")
}

func TestHandlePassPostRegistration(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("passuser")
	lines := client.sendAndExpect(
		"PASS :mypassword123", "Password set",
	)

	assertContains(
		t, lines, "Password set", "password confirmation",
	)
}

func TestPreRegistrationNotRegistered(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.send("PRIVMSG #test :hello")

	line := client.readLine()
	if !strings.Contains(line, " 451 ") {
		t.Errorf(
			"expected ERR_NOTREGISTERED (451), got: %s",
			line,
		)
	}
}

func TestNamesNonExistentChannel(t *testing.T) {
	t.Parallel()

	env := newTestEnv(t)
	client := env.dial(t)

	client.register("namesuser")
	lines := client.sendAndExpect(
		"NAMES #doesnotexist", " 366 ",
	)

	assertContains(
		t, lines, " 366 ",
		"RPL_ENDOFNAMES for non-existent channel",
	)
}

func BenchmarkParseMessage(b *testing.B) {
	line := ":nick!user@host PRIVMSG #channel :Hello, world!"

	b.ResetTimer()

	for range b.N {
		_ = ircserver.ParseMessage(line)
	}
}

func BenchmarkFormatMessage(b *testing.B) {
	b.ResetTimer()

	for range b.N {
		_ = ircserver.FormatMessage(
			"nick!user@host", "PRIVMSG",
			"#channel", "Hello, world!",
		)
	}
}