package session

// These tests pin the behavior of the unversioned charmbracelet/x/vt
// dependency. If an upstream bump changes input encoding or mode-callback
// semantics, they fail loudly instead of termd silently emitting wrong bytes.

import (
	"io"
	"sync"
	"testing"
	"time"

	uv "github.com/charmbracelet/ultraviolet"
	"github.com/charmbracelet/x/ansi"
	"github.com/charmbracelet/x/vt"
)

// collector continuously drains the emulator's encoded-input pipe. It must be
// running before any Send* call: the pipe is synchronous, so an unread write
// blocks forever (the daemon's pump goroutine plays this role in production).
type collector struct {
	mu  sync.Mutex
	buf []byte
}

func collect(em *vt.Emulator) *collector {
	c := &collector{}
	go func() {
		b := make([]byte, 4096)
		for {
			n, err := em.Read(b)
			if n > 0 {
				c.mu.Lock()
				c.buf = append(c.buf, b[:n]...)
				c.mu.Unlock()
			}
			if err != nil {
				return
			}
		}
	}()
	return c
}

// expect polls until the collected bytes equal want, then resets the buffer.
func (c *collector) expect(t *testing.T, label, want string) {
	t.Helper()
	deadline := time.Now().Add(2 * time.Second)
	for {
		c.mu.Lock()
		got := string(c.buf)
		c.mu.Unlock()
		if got == want {
			c.mu.Lock()
			c.buf = nil
			c.mu.Unlock()
			return
		}
		if time.Now().After(deadline) {
			t.Fatalf("%s: got %q, want %q", label, got, want)
		}
		time.Sleep(5 * time.Millisecond)
	}
}

// expectNothing asserts no bytes arrive within a settle window.
func (c *collector) expectNothing(t *testing.T, label string) {
	t.Helper()
	time.Sleep(50 * time.Millisecond)
	c.mu.Lock()
	got := string(c.buf)
	c.mu.Unlock()
	if got != "" {
		t.Fatalf("%s: got %q, want nothing", label, got)
	}
}

func TestVTKeyEncodingRespectsDECCKM(t *testing.T) {
	em := vt.NewEmulator(80, 24)
	c := collect(em)

	em.SendKey(uv.KeyPressEvent{Code: uv.KeyUp})
	em.SendKey(uv.KeyPressEvent{Code: 'c', Mod: uv.ModCtrl})
	em.SendKey(uv.KeyPressEvent{Code: uv.KeyEnter})
	c.expect(t, "normal mode", "\x1b[A\x03\r")

	// Application cursor keys (DECSET ?1) switches arrows to SS3.
	if _, err := io.WriteString(em, "\x1b[?1h"); err != nil {
		t.Fatal(err)
	}
	em.SendKey(uv.KeyPressEvent{Code: uv.KeyUp})
	c.expect(t, "DECCKM mode", "\x1bOA")
}

func TestVTMouseEncoding(t *testing.T) {
	em := vt.NewEmulator(80, 24)
	c := collect(em)

	// No tracking mode: SendMouse must emit nothing (termd's 409 pre-check
	// assumes this, but must not depend on it).
	em.SendMouse(uv.MouseClickEvent{X: 1, Y: 1, Button: uv.MouseLeft})
	c.expectNothing(t, "mouse without tracking mode")

	// SGR encoding (?1000 + ?1006): CSI < b;x+1;y+1 M/m, 1-based cells.
	if _, err := io.WriteString(em, "\x1b[?1000h\x1b[?1006h"); err != nil {
		t.Fatal(err)
	}
	em.SendMouse(uv.MouseClickEvent{X: 10, Y: 5, Button: uv.MouseLeft})
	em.SendMouse(uv.MouseReleaseEvent{X: 10, Y: 5, Button: uv.MouseLeft})
	c.expect(t, "SGR click", "\x1b[<0;11;6M\x1b[<0;11;6m")

	em.SendMouse(uv.MouseWheelEvent{X: 0, Y: 0, Button: uv.MouseWheelUp})
	c.expect(t, "SGR wheel", "\x1b[<64;1;1M")

	// Legacy X10 encoding when ?1006 is off.
	if _, err := io.WriteString(em, "\x1b[?1006l"); err != nil {
		t.Fatal(err)
	}
	em.SendMouse(uv.MouseClickEvent{X: 2, Y: 3, Button: uv.MouseLeft})
	c.expect(t, "X10 click", "\x1b[M\x20\x23\x24")
}

func TestVTModeCallbacks(t *testing.T) {
	em := vt.NewEmulator(80, 24)
	var ms modeState
	ms.cursorVisible = true
	altScreen := false
	em.SetCallbacks(vt.Callbacks{
		EnableMode:  func(m ansi.Mode) { ms.set(m, true) },
		DisableMode: func(m ansi.Mode) { ms.set(m, false) },
		AltScreen:   func(on bool) { altScreen = on },
	})

	if _, err := io.WriteString(em, "\x1b[?1049h\x1b[?1h\x1b[?1002h\x1b[?1006h\x1b[?2004h"); err != nil {
		t.Fatal(err)
	}
	if !altScreen {
		t.Error("alt screen callback did not fire on ?1049h")
	}
	if got := ms.mouseMode(); got != "button_event" {
		t.Errorf("mouse mode = %q, want button_event", got)
	}
	if !ms.sgrExt || !ms.appCursorKeys || !ms.bracketedPaste {
		t.Errorf("modes not all tracked: %+v", ms)
	}

	if _, err := io.WriteString(em, "\x1b[?1002l\x1b[?1049l"); err != nil {
		t.Fatal(err)
	}
	if altScreen {
		t.Error("alt screen still on after ?1049l")
	}
	if got := ms.mouseMode(); got != "off" {
		t.Errorf("mouse mode after disable = %q, want off", got)
	}
}