package game

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"

	"thehouseoficarus/internal/config"
	"thehouseoficarus/internal/net"
	"thehouseoficarus/internal/player"
)

// chanConn is a test Conn whose reads come from a channel, so a session's
// input loop can run on its own goroutine exactly like the real server's
// connection goroutine. Writes are recorded in a mutex-guarded buffer and may
// optionally be gated to simulate a slow/stalled client.
type chanConn struct {
	mu     sync.Mutex
	out    []byte
	in     chan string
	closed chan struct{}
	once   sync.Once

	// writeGate, when non-nil, blocks every Write until released.
	writeGate chan struct{}
}

func newChanConn() *chanConn {
	return &chanConn{in: make(chan string, 64), closed: make(chan struct{})}
}

func (c *chanConn) ReadMessage() (string, error) {
	select {
	case line := <-c.in:
		return line, nil
	case <-c.closed:
		return "", fmt.Errorf("connection closed")
	}
}

func (c *chanConn) Write(b []byte) (int, error) {
	if c.writeGate != nil {
		select {
		case <-c.writeGate:
		case <-c.closed:
			return 0, fmt.Errorf("write on closed conn")
		}
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	c.out = append(c.out, b...)
	return len(b), nil
}

func (c *chanConn) Close() error {
	c.once.Do(func() { close(c.closed) })
	return nil
}

func (c *chanConn) SetWriteDeadline(time.Time) error { return nil }
func (c *chanConn) SetReadDeadline(time.Time) error  { return nil }

func (c *chanConn) SetEcho(bool) error { return nil }

func (c *chanConn) Bytes() []byte {
	c.mu.Lock()
	defer c.mu.Unlock()
	return append([]byte(nil), c.out...)
}

func (c *chanConn) Contains(substr string) bool {
	return strings.Contains(string(c.Bytes()), substr)
}

// harness wires a real Game (temp data dir) to fake transports driven from
// per-connection goroutines plus a competing tick goroutine, reproducing the
// production entry-point concurrency: session input, disconnect callbacks, and
// tick callbacks all touching shared state at once.
type harness struct {
	t    *testing.T
	dir  string
	g    *Game
	hub  *net.Hub
	stop func()

	mu       sync.Mutex
	sessions map[string]*net.Session
	conns    map[string]*chanConn
}

func newHarness(t *testing.T) *harness {
	t.Helper()
	dir := t.TempDir()
	seedWorld(t, dir)
	colors := &config.ColorsConfig{}
	g := New(dir, colors, colors, config.ValidationConfig{}, 1)
	hub := net.NewHub()
	g.SetHub(hub)

	stopTick := make(chan struct{})
	done := make(chan struct{})
	go func() {
		defer close(done)
		tick := time.NewTicker(2 * time.Millisecond)
		defer tick.Stop()
		for {
			select {
			case <-tick.C:
				g.Ticks.Tick()
			case <-stopTick:
				return
			}
		}
	}()

	h := &harness{
		t: t, dir: dir, g: g, hub: hub,
		sessions: make(map[string]*net.Session),
		conns:    make(map[string]*chanConn),
	}
	h.stop = func() { close(stopTick); <-done }
	// Stop the Game's owner goroutine too, or every harness test leaks one
	// (each holding a 4096-slot channel) for the life of the test binary.
	// Cleanup is LIFO, so the ticker stops first, then the owner.
	t.Cleanup(g.stopOwner)
	t.Cleanup(h.stop)
	return h
}

// newHarnessWithTicks is newHarness with the production master tick
// subscription registered, so tick-driven systems (disconnect countdown,
// action advance, casino tick) run exactly as they do in production. Most
// harness tests drive the systems directly and do not need this.
func newHarnessWithTicks(t *testing.T) *harness {
	t.Helper()
	h := newHarness(t)
	h.g.SubscribeTicks(1, func() bool {
		h.g.RunTickSystems()
		return true
	})
	return h
}

// Regression: the harness must be able to run the real master tick sequence,
// which is the only way the disconnect countdown (Hub.Remove -> DisconnectTick
// -> onRemove) is exercised end-to-end.
func TestHarnessWithTicksCompletesDisconnect(t *testing.T) {
	h := newHarnessWithTicks(t)
	h.seedAccount("alice")
	h.seedCharacter("alice", "alice")
	sess, _ := h.connect("alice")
	h.hub.Remove(sess)
	h.barrier()
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) && len(h.hub.AllSessions()) > 0 {
		time.Sleep(5 * time.Millisecond)
	}
	if got := len(h.hub.AllSessions()); got != 0 {
		t.Fatalf("session not hard-removed after the countdown: %d", got)
	}
}

// seedWorld writes the minimal on-disk content a Game needs: three rooms.
func seedWorld(t *testing.T, dir string) {
	t.Helper()
	for _, d := range []string{"rooms", "players/accounts", "players/characters"} {
		if err := os.MkdirAll(filepath.Join(dir, d), 0755); err != nil {
			t.Fatalf("mkdir %s: %v", d, err)
		}
	}
	files := map[string]string{
		"rooms/1.yaml": "id: 1\nname: Central\nexits:\n  north:\n    room: 2\n",
		"rooms/2.yaml": "id: 2\nname: North\nexits:\n  south:\n    room: 1\n",
		"rooms/3.yaml": "id: 3\nname: East\n",
	}
	for path, content := range files {
		if err := os.WriteFile(filepath.Join(dir, path), []byte(content), 0644); err != nil {
			t.Fatalf("seed %s: %v", path, err)
		}
	}
}

// seedAccount writes an account file directly (bypassing the login menu).
func (h *harness) seedAccount(name string) {
	const password = "pw"
	t := h.t
	hash, err := player.HashPassword(password)
	if err != nil {
		t.Fatalf("hash: %v", err)
	}
	acc := &player.Account{Name: name, PasswordHash: hash}
	if err := h.g.AccountStore.SaveAccount(acc); err != nil {
		t.Fatalf("seed account %s: %v", name, err)
	}
}

// seedCharacter writes a character file owned by the named account.
func (h *harness) seedCharacter(charName, accountName string) *player.Player {
	t := h.t
	p := player.New(charName)
	p.RoomID = 1
	p.Account = accountName
	if err := h.g.AccountStore.SaveCharacter(p); err != nil {
		t.Fatalf("seed character %s: %v", charName, err)
	}
	acc, err := h.g.AccountStore.LoadAccount(accountName)
	if err != nil {
		t.Fatalf("load account %s: %v", accountName, err)
	}
	acc.Characters = append(acc.Characters, charName)
	if err := h.g.AccountStore.SaveAccount(acc); err != nil {
		t.Fatalf("save account: %v", err)
	}
	return p
}

// connect registers a live in-game session directly, bypassing the login
// menu. The session is put into queued-write mode (like real transports) and
// its input is dispatched through the owner entry point, matching production
// concurrency exactly. Tests that exercise the menu drive handleAccountName
// themselves.
func (h *harness) connect(name string) (*net.Session, *chanConn) {
	t := h.t
	acc, err := h.g.AccountStore.LoadAccount(name)
	if err != nil {
		t.Fatalf("connect %s: %v", name, err)
	}
	p, err := h.g.AccountStore.LoadCharacter(name)
	if err != nil {
		t.Fatalf("connect %s: %v", name, err)
	}
	conn := newChanConn()
	sess := &net.Session{Conn: conn, Account: acc, Player: p}
	sess.SetState(net.StateGame)
	sess.StartWriter()
	h.hub.Add(sess)
	h.hub.EnterRoom(sess, p.RoomID)
	h.g.attachSession(sess)
	h.mu.Lock()
	h.sessions[name] = sess
	h.conns[name] = conn
	h.mu.Unlock()
	return sess, conn
}

// connectMenu registers a session authenticated to accountName sitting in
// the character menu (no character loaded).
func (h *harness) connectMenu(accountName string) *net.Session {
	acc, err := h.g.AccountStore.LoadAccount(accountName)
	if err != nil {
		h.t.Fatalf("connectMenu %s: %v", accountName, err)
	}
	conn := newChanConn()
	sess := &net.Session{Conn: conn, Account: acc}
	sess.SetState(net.StateMenu)
	sess.StartWriter()
	h.hub.Add(sess)
	h.mu.Lock()
	h.sessions[accountName+"-menu"] = sess
	h.conns[accountName+"-menu"] = conn
	h.mu.Unlock()
	return sess
}

// barrier blocks until every task submitted so far has executed on the
// owner goroutine.
func (h *harness) barrier() {
	h.g.RunOnOwner(func() {})
}

// input mirrors net.Server.handleSession: a per-connection goroutine reading
// lines and dispatching them to HandleSession until the channel closes.
func (h *harness) input(sess *net.Session, lines <-chan string) {
	for line := range lines {
		h.g.HandleSessionOnOwner(sess, line)
	}
}

// goInput starts the input goroutine for a session, returning the send channel.
func (h *harness) goInput(sess *net.Session) chan<- string {
	lines := make(chan string, 64)
	go h.input(sess, lines)
	return lines
}