package e2e_test

import (
	"testing"
	"time"

	"gioui.org/io/key"
	"pad/internal/editor"
	"pad/internal/test/e2e"
	"pad/internal/ui"
)

// incidentContent is the file from the 2026-09-19 phone incident: "test"
// plus five newlines (9 bytes). The tap target is byte 6 (the start of
// line 3), exactly where the user tapped.
const incidentContent = "test\n\n\n\n\n"

func setCursor(t *testing.T, h *e2e.Harness, pos int) {
	t.Helper()
	if err := h.WithState(func(st *editor.State) {
		st.Editor.CursorPosition = pos
	}); err != nil {
		t.Fatalf("set cursor: %v", err)
	}
}

// contentAfter sends the input batch (nil = none) and waits until the buffer
// content reaches want; the logic goroutine applies the events
// asynchronously, so a read straight after SendInput is a race.
func contentAfter(t *testing.T, h *e2e.Harness, events []ui.InputEvent, want string) string {
	t.Helper()
	if events != nil {
		h.SendInput(events)
	}
	for i := 0; i < 300; i++ {
		c, err := h.FullContent()
		if err != nil {
			t.Fatalf("FullContent: %v", err)
		}
		if c == want {
			return c
		}
		time.Sleep(10 * time.Millisecond)
	}
	t.Fatalf("buffer did not reach %q", want)
	return ""
}

// TestIMECommitAfterEnterKeySameBatch is the exact phone incident: tap at
// byte 6, type "a" (Gboard autocaps and commits [6,6)→"A"), press Enter
// (Gboard sends it as a KEY EVENT, not a commit — the logic inserts "\n"
// and the caret moves to 8, but Gboard's local model still lacks it), then
// type "a" (Gboard, one edit behind, commits the word append [6,7)→"Aa"
// against the pre-Enter caret). The key event and the append commit arrive
// in the same input batch, so no frame has drawn between them.
//
// The append must be applied at its reported range — everything before the
// pending key edit is byte-identical in both models — instead of being
// drift-snapped to the new caret and duplicated (the incident produced
// "test\n\nA\nAaAa\n\n\n").
func TestIMECommitAfterEnterKeySameBatch(t *testing.T) {
	h, _ := realFileHarness(t, "test.txt", incidentContent)
	defer h.Cleanup()
	setCursor(t, h, 6)

	// "a" typed with autocap: one clean IME commit.
	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 6, EndRune: 6, Text: "A"},
	}}, "test\n\nA\n\n\n")

	// Enter (key event) and the stale-model word append in ONE batch: the
	// logic processes the "\n" first, so when the append is guarded the
	// caret is already at 8 while the commit ends at 7. "A" must be replaced
	// by "Aa" in place and the Enter newline survive after it.
	contentAfter(t, h, []ui.InputEvent{
		{Handler: editor.HandleKeyDown, Data: ui.KeyEvent{Name: key.NameReturn}},
		{Handler: editor.HandleIMECommit, Data: editor.IMECommit{StartRune: 6, EndRune: 7, Text: "Aa"}},
	}, "test\n\nAa\n\n\n\n")

	if pos, _ := h.CursorPosition(); pos != 8 {
		t.Errorf("cursor: got %d want 8 (end of the replaced word)", pos)
	}
}

// TestIMECommitAfterEnterKeyNextBatch is the same incident with the append
// commit arriving in a LATER input batch than the Enter: a frame was
// emitted for the Enter, but the resyncing snippet push only lands on the
// next drawn frame, and the IME's commit can beat it. The pending key edit
// must still be honored.
func TestIMECommitAfterEnterKeyNextBatch(t *testing.T) {
	h, _ := realFileHarness(t, "test.txt", incidentContent)
	defer h.Cleanup()
	setCursor(t, h, 6)

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 6, EndRune: 6, Text: "A"},
	}}, "test\n\nA\n\n\n")

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleKeyDown,
		Data:    ui.KeyEvent{Name: key.NameReturn},
	}}, "test\n\nA\n\n\n\n")

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 6, EndRune: 7, Text: "Aa"},
	}}, "test\n\nAa\n\n\n\n")
}

// TestIMEEmptyCommitStillSnappedWithPendingEdit: a pending key edit does
// NOT relax the guard for range deletions (empty text). Deleting at a range
// the IME sees but the app no longer expects there is how documents get
// clobbered; such commits must still snap to the caret (a no-op there).
func TestIMEEmptyCommitStillSnappedWithPendingEdit(t *testing.T) {
	h, _ := realFileHarness(t, "test.txt", incidentContent)
	defer h.Cleanup()
	setCursor(t, h, 6)

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 6, EndRune: 6, Text: "A"},
	}}, "test\n\nA\n\n\n")

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleKeyDown,
		Data:    ui.KeyEvent{Name: key.NameReturn},
	}}, "test\n\nA\n\n\n\n")

	// Gboard's stale model still shows "A" at [6,7) and asks to delete it.
	// The commit must snap to the caret (a no-op there), so the "A"
	// survives. The content is unchanged by a correct snap, so poll for
	// quiescence (a new frame after the input) before asserting.
	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 6, EndRune: 7, Text: ""},
	}}, "test\n\nA\n\n\n\n")
	before := h.FrameCount()
	for h.FrameCount() == before {
		time.Sleep(10 * time.Millisecond)
	}
	if c, _ := h.FullContent(); c != "test\n\nA\n\n\n\n" {
		t.Fatalf("empty commit must snap to the caret (no-op), got %q", c)
	}
}

// TestIMECommitPastPendingEditStillSnapped: a commit that ends PAST the
// pending key edit addresses text the IME's model does not have (it is
// shifted by the edit), so it is still anomalous and snaps to the caret.
func TestIMECommitPastPendingEditStillSnapped(t *testing.T) {
	h, _ := realFileHarness(t, "test.txt", incidentContent)
	defer h.Cleanup()
	setCursor(t, h, 6)

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 6, EndRune: 6, Text: "A"},
	}}, "test\n\nA\n\n\n")

	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleKeyDown,
		Data:    ui.KeyEvent{Name: key.NameReturn},
	}}, "test\n\nA\n\n\n\n")

	// Ends at 9, past the pending edit at 7: the range crosses the edit, so
	// the file content there is NOT what the IME sees. Snap to the caret
	// (8): "x" lands at 8, not 9.
	contentAfter(t, h, []ui.InputEvent{{
		Handler: editor.HandleIMECommit,
		Data:    editor.IMECommit{StartRune: 9, EndRune: 9, Text: "x"},
	}}, "test\n\nA\nx\n\n\n")
}