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

package review

import (
	"context"

	"git.stormux.org/storm/cthulhu/internal/atspi"
)

// Native selections can report their caret on a label/paragraph rather than
// its static text child. Transfer offsets only when both expose the identical
// text range. Captured hypertext parents own their direct-text offsets;
// embedded or ambiguous child offsets must never be guessed.
func (cursor *DocumentCursor) syncNativeCaret(ctx context.Context, reader DocumentCaretReader, focus atspi.ObjectID, offset int) error {
	if offset < 0 {
		return atspi.ErrNoDocumentCaret
	}
	if _, err := cursor.SyncFocus(ctx, focus); err != nil {
		return err
	}
	cursor.mu.Lock()
	defer cursor.mu.Unlock()
	place := &cursor.places[len(cursor.places)-1]
	doc, err := cursor.tree.Document(ctx, place.focus)
	if err != nil {
		return err
	}
	node, offset, err := native_caret_node(ctx, reader, doc, focus, offset)
	if err != nil {
		return err
	}

	place.object, place.offset, place.origin = node.Reference, offset, CaretNavigation
	place.tableCell = atspi.ObjectID{}
	return nil
}

func native_caret_node(ctx context.Context, reader DocumentCaretReader, doc atspi.DocumentSnapshot, focus atspi.ObjectID, offset int) (atspi.DocumentNode, int, error) {
	nodes := make(map[atspi.ObjectID]atspi.DocumentNode, len(doc.Nodes))
	for _, node := range doc.Nodes {
		nodes[node.Reference.ID()] = node
	}
	node := nodes[focus]
	if !node.Reference.Valid() || offset < 0 || offset > node.Snapshot.CharacterCount || node.Snapshot.Editable || node.Snapshot.Role == "password text" {
		return atspi.DocumentNode{}, 0, atspi.ErrNoDocumentCaret
	}
	for len(node.Children) != 0 && !wholeCaretNode(node.Snapshot) {
		if len(node.Snapshot.TextChildren) != 0 {
			embedded := atspi.ObjectID{}
			for _, child := range node.Snapshot.TextChildren {
				if child.Offset == offset {
					embedded = child.Child
					break
				}
			}
			if !embedded.Valid() {
				return node, offset, nil
			}
			child, ok := nodes[embedded]
			if !ok || child.Hidden || child.Snapshot.Editable || child.Snapshot.Role == "password text" {
				return atspi.DocumentNode{}, 0, atspi.ErrNoDocumentCaret
			}
			node, offset = child, 0
			continue
		}
		if len(node.Children) != 1 {
			return atspi.DocumentNode{}, 0, atspi.ErrNoDocumentCaret
		}
		child, ok := nodes[node.Children[0]]
		if !ok || child.Hidden || child.Snapshot.Editable || child.Snapshot.CharacterCount != node.Snapshot.CharacterCount {
			return atspi.DocumentNode{}, 0, atspi.ErrNoDocumentCaret
		}
		probeOffset := max(0, min(offset, node.Snapshot.CharacterCount-1))
		parentText, err := reader.ReadDocumentCaret(ctx, node.Reference, probeOffset, atspi.DocumentCaretBrailleLine)
		if err != nil {
			return atspi.DocumentNode{}, 0, err
		}
		childText, err := reader.ReadDocumentCaret(ctx, child.Reference, probeOffset, atspi.DocumentCaretBrailleLine)
		if err != nil {
			return atspi.DocumentNode{}, 0, err
		}
		if parentText.Start != childText.Start || parentText.End != childText.End || parentText.Text == "" || parentText.Text != childText.Text {
			return atspi.DocumentNode{}, 0, atspi.ErrNoDocumentCaret
		}
		node = child
	}
	return node, offset, nil
}

// Use the navigation FIFO so a subsequent intercepted arrow sees the native
// selection endpoint, even if capturing the document is still in progress.
func (worker *Worker) SyncDocumentCaret(focus atspi.ObjectID, offset int) error {
	if !focus.Valid() || offset < 0 {
		return atspi.ErrNoDocumentCaret
	}
	select {
	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), nativeCaret: true, nativeCaretFocus: focus, nativeCaretOffset: offset}:
		return nil
	default:
		return ErrRequestQueueFull
	}
}

func (worker *Worker) syncDocumentCaret(ctx context.Context, cursor *DocumentCursor, request request) (Result, *DocumentCursor) {
	result := Result{DocumentNativeCaret: true, DocumentEpoch: request.documentEpoch, DocumentFocus: request.nativeCaretFocus}
	if worker.focus() != request.nativeCaretFocus {
		result.Err = atspi.ErrStaleObject
		return result, cursor
	}
	reader, ok := worker.nativeCapturerFor(request.nativeCaretFocus).(DocumentCaretReader)
	if !ok {
		result.Err = atspi.ErrNoDocumentCaret
		return result, cursor
	}
	ctx, cancel := context.WithTimeout(ctx, worker.captureTimeout)
	defer cancel()
	if cursor == nil {
		cursor, result.Err = worker.refreshDocumentCursor(ctx, nil, request.nativeCaretFocus)
		if result.Err != nil {
			return result, cursor
		}
	}
	result.Err = cursor.syncNativeCaret(ctx, reader, request.nativeCaretFocus, request.nativeCaretOffset)
	if documentNeedsCapture(result.Err) {
		fresh, captureErr := worker.refreshDocumentCursor(ctx, cursor, request.nativeCaretFocus)
		if captureErr == nil && worker.focus() == request.nativeCaretFocus {
			cursor = fresh
			result.Err = cursor.syncNativeCaret(ctx, reader, request.nativeCaretFocus, request.nativeCaretOffset)
		} else if captureErr != nil {
			result.Err = captureErr
		}
	}
	if result.Err == nil {
		result.DocumentPosition, result.Err = cursor.SyncFocus(ctx, request.nativeCaretFocus)
	}
	return result, cursor
}