// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
// SPDX-License-Identifier: GPL-3.0-or-later

package atspi

func documentNavigationEchoBit(event Event, offset int, selectionOffsets map[int]bool) uint8 {
	switch event.Type {
	case FocusEvent:
		return 1
	case FocusedStateEvent:
		return 2
	case CaretEvent:
		// New native selection is user input, even if its endpoint happens
		// to match a previously requested caret or collapsed selection.
		if event.Source.TextCaretKnown && event.Source.SelectionEnd > event.Source.SelectionStart {
			return 0
		}
		if event.Detail1 == offset {
			return 4
		}
		if event.Source.TextCaretKnown && selectionOffsets[event.Detail1] {
			return 8
		}
	}
	return 0
}

// Chromium can echo a static text caret on its enclosing label/paragraph.
// Include only a single-child chain sharing the complete text offset domain.
// Composite parents have their own hypertext offsets and cannot be matched.
func documentCaretEchoAncestors(tree *AccessibleTree, reference ObjectReference) []ObjectID {
	var ids []ObjectID
	child, err := tree.Resolve(reference)
	if err != nil || child.CharacterCount <= 0 {
		return nil
	}
	for attempts := 0; attempts < maxTreeNodes; attempts++ {
		parent, ok, err := tree.Parent(reference)
		if err != nil || !ok {
			break
		}
		snapshot, err := tree.Resolve(parent)
		if err != nil || IsWebDocumentRole(snapshot.Role) || snapshot.Editable || snapshot.CharacterCount != child.CharacterCount {
			break
		}
		first, ok, err := tree.FirstChild(parent)
		if err != nil || !ok || first != reference {
			break
		}
		last, ok, err := tree.LastChild(parent)
		if err != nil || !ok || last != reference {
			break
		}
		ids = append(ids, parent.ID())
		reference, child = parent, snapshot
	}
	return ids
}