Pad/internal/test/e2e/scroll_cursor_test.go

package e2e_test

import (
	"testing"
	"time"

	"pad/internal/editor"
	"pad/internal/test/e2e"
	"pad/internal/ui"
)

// TestEditorClickToMoveCursorWithScroll verifies that a tap in the editor
// accounts for the current scroll offset and lands on the right line.
//
// State setup/assertions use the harness's owner-side helpers (WithState /
// CursorPosition / Inspect); the tap handler closure runs on the logic
// goroutine via SendInput, so its reads of editor.TheState are safe.
func TestEditorClickToMoveCursorWithScroll(t *testing.T) {
	// NewHarnessWithDefaults already starts the logic goroutine.
	h := e2e.NewHarnessWithDefaults()
	defer h.Cleanup()

	// Switch to editor page (owner-side)
	if err := h.WithState(func(st *editor.State) { editor.GoToEditor(nil) }); err != nil {
		t.Fatalf("GoToEditor: %v", err)
	}
	h.SendConfig(780, 1688)
	// Give it a moment to initialize
	time.Sleep(200 * time.Millisecond)

	// Wait for frame
	_, err := h.WaitForFrameCount(1, 5*time.Second)
	if err != nil {
		t.Fatalf("timeout waiting for frame: %v", err)
	}

	// Setup:
	// - 2 lines, each 10 chars + newline.
	// - Line height = 14 * 1.2 = 16.8 (rounded?) Let's check EditorLineHeight()
	// EditorLineHeight is 14 * 1.2 = 16.8.
	lineHeight := 16.8
	if err := h.WithState(func(st *editor.State) {
		st.Editor.Buffer = "Line 1\nLine 2\nLine 3"

		// Scroll to start of Line 2 (skip Line 1)
		st.ScrollOffset = ui.Dp(lineHeight)

		// GlyphLayout:
		// Line 1: y = 0
		// Line 2: y = 16.8
		// Line 3: y = 33.6
		st.Editor.GlyphLayout = ui.GlyphLayout{
			ByteOffsets: []int{0, 7, 14}, // Start of each line
			X:           []ui.Dp{10, 10, 10},
			Y:           []ui.Dp{ui.Dp(0), ui.Dp(lineHeight), ui.Dp(lineHeight * 2)},
			Advance:     []ui.Dp{10, 10, 10},
		}
	}); err != nil {
		t.Fatalf("WithState: %v", err)
	}

	// Tap at y=10 (within the text area).
	// Because of scroll=16.8, this should correspond to:
	// visualLine = (y + scroll) / lineHeight = (10 + 16.8) / 16.8 = 26.8 / 16.8 = 1.59 -> 1
	// Line 1 is index 0. Line 2 is index 1.
	// So visualLine 1 should be Line 2.

	// The problem is that SetCursorFromPoint expects y in DP, but receives it as raw pixels
	// if we're not careful. Let's pass the y value properly.
	// The test harness sends raw pixel coordinates to handler.
	// EditorLayout converts tap point:
	// localY := float64(pt.Y - editorRegion.Y + TheState.ScrollOffset)
	// So the handler receives Y as pt.Y, where pt.Y is relative to the screen.
	// The test harness doesn't seem to account for region offset.

	// Let's debug by printing in the test (owner-side read).
	v, err := h.Inspect(func(st *editor.State) any { return float64(st.ScrollOffset) })
	if err != nil {
		t.Fatalf("Inspect: %v", err)
	}
	t.Logf("ScrollOffset: %v", v)

	h.SendInput([]ui.InputEvent{
		{
			Handler: func(data any) {
				if pt, ok := data.(ui.Point); ok {
					// Manually simulate the offset correction that EditorLayout does
					// editorRegion.Y is the (margin-free) statusBarH(32) = 32.
					// Let's set pt.Y to 10 + 32 = 42.
					localY := float64(pt.Y) - 32.0 + float64(editor.TheState.ScrollOffset)
					editor.SetCursorFromPoint(float64(pt.X), localY)
				}
			},
			Data: ui.Point{X: 10, Y: 42},
		},
	})

	// Assert cursor moved to start of Line 2 (offset 7)
	time.Sleep(100 * time.Millisecond) // Give logic goroutine a moment to process input
	pos, err := h.CursorPosition()
	if err != nil {
		t.Fatalf("CursorPosition: %v", err)
	}
	t.Logf("Cursor position: %d", pos)
	if pos != 7 {
		t.Errorf("expected cursor to move to 7 (Line 2), but got %d", pos)
	}
}

// TestRealFile_CaretCursorOutsideWindow pins the off-screen caret contract:
// when the user scrolls the caret's line out of the viewport, the shaped
// window no longer contains the cursor's byte, and the frame must carry the
// TRUE window-relative cursor position (negative when the cursor is above
// the window, past len(Value) when below) so the renderer can skip the caret
// entirely.
//
// Pre-fix, EditorLayout clamped a negative window-relative cursor to 0 and
// drawWrappedText drew the caret unconditionally: scrolling the caret's line
// just past the top of the viewport made the caret "jump" onto the first
// visible line, then snap back to its real line when the user scrolled back
// (the reported cursor-jumps-to-adjacent-line bug). Native Android simply
// does not draw a caret that is off-screen.
func TestRealFile_CaretCursorOutsideWindow(t *testing.T) {
	const (
		lines    = 60
		lineLen  = 21
		scrollLn = 10
	)
	h, _ := realFileHarness(t, "caret_window.txt", uniformContent(lines))
	defer h.Cleanup()

	h.SendConfig(780, 400)
	if _, err := h.WaitForFrame(5 * time.Second); err != nil {
		t.Fatalf("wait for frame: %v", err)
	}

	// Scroll so the window starts at line 10 (byte 210); put the caret on
	// line 5 (byte 105), ABOVE the window.
	caretAbove := 5 * lineLen
	if err := h.WithState(func(st *editor.State) {
		st.ScrollOffset = ui.Dp(16.8*scrollLn + 5)
		st.Editor.CursorPosition = caretAbove
	}); err != nil {
		t.Fatalf("WithState: %v", err)
	}
	prev := h.FrameCount()
	h.SendConfig(780, 400) // state changes alone do not emit frames
	if _, err := h.WaitForFrameCount(prev+1, 5*time.Second); err != nil {
		t.Fatalf("wait for scrolled frame: %v", err)
	}
	tf, ok := lastEditorTextField(t, h)
	if !ok {
		t.Fatal("no editor_text TextField in latest frame")
	}
	if want := caretAbove - scrollLn*lineLen; tf.CursorPosition != want {
		t.Fatalf("window cursor above = %d, want %d (negative: cursor above window, caret must be hidden)", tf.CursorPosition, want)
	}

	// Mirror case: caret on line 50 (byte 1050), BELOW the window (the
	// ~18-line window at line 10 ends far short of it).
	caretBelow := 50 * lineLen
	if err := h.WithState(func(st *editor.State) {
		st.Editor.CursorPosition = caretBelow
	}); err != nil {
		t.Fatalf("WithState: %v", err)
	}
	prev = h.FrameCount()
	h.SendConfig(780, 400)
	if _, err := h.WaitForFrameCount(prev+1, 5*time.Second); err != nil {
		t.Fatalf("wait for scrolled frame (below): %v", err)
	}
	tf, ok = lastEditorTextField(t, h)
	if !ok {
		t.Fatal("no editor_text TextField in latest frame")
	}
	if want := caretBelow - scrollLn*lineLen; tf.CursorPosition != want {
		t.Fatalf("window cursor below = %d, want %d (past len(Value): cursor below window, caret must be hidden)", tf.CursorPosition, want)
	}
	if tf.CursorPosition <= len(tf.Value) {
		t.Fatalf("window cursor %d should be past window end %d", tf.CursorPosition, len(tf.Value))
	}

	// And the in-window case must still carry the plain relative offset.
	if err := h.WithState(func(st *editor.State) {
		st.Editor.CursorPosition = 12*lineLen + 9
	}); err != nil {
		t.Fatalf("WithState: %v", err)
	}
	prev = h.FrameCount()
	h.SendConfig(780, 400)
	if _, err := h.WaitForFrameCount(prev+1, 5*time.Second); err != nil {
		t.Fatalf("wait for scrolled frame (inside): %v", err)
	}
	tf, ok = lastEditorTextField(t, h)
	if !ok {
		t.Fatal("no editor_text TextField in latest frame")
	}
	if want := 12*lineLen + 9 - scrollLn*lineLen; tf.CursorPosition != want {
		t.Fatalf("window cursor inside = %d, want %d", tf.CursorPosition, want)
	}
}