// Cthulhu screen reader.
// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program. If not, see <https://www.gnu.org/licenses/gpl-3.0.html>.

package review

import (
	"context"
	"errors"
	"fmt"

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

type moveResult struct {
	Result
	cursor *Cursor
}

func (worker *Worker) move(ctx context.Context, cursor *Cursor, direction Direction) moveResult {
	var err error
	cursor, err = worker.syncLatestFocus(ctx, cursor, true)
	if err != nil {
		return moveResult{Result: Result{Direction: direction, Err: err}, cursor: cursor}
	}
	if cursor == nil {
		return moveResult{Result: Result{Direction: direction, Err: ErrNoCurrent}}
	}
	position, moved, err := cursor.Move(direction)
	if err == nil {
		return moveResult{Result: Result{Direction: direction, Position: position, Moved: moved}, cursor: cursor}
	}
	if !errors.Is(err, atspi.ErrStaleObject) && !errors.Is(err, atspi.ErrIncompleteTree) {
		return moveResult{Result: Result{Direction: direction, Err: err}, cursor: cursor}
	}

	// An incomplete child list needs recapture without abandoning an otherwise
	// live independent review position. Stale objects still recover from focus.
	var retained *Cursor
	if errors.Is(err, atspi.ErrIncompleteTree) {
		retained = cursor
	}
	recovered, recoveryErr := worker.captureCursor(ctx, retained)
	if recoveryErr != nil {
		return moveResult{Result: Result{Direction: direction, Err: recoveryErr}, cursor: retained}
	}
	if recovered == nil {
		return moveResult{Result: Result{Direction: direction, Err: err}}
	}
	position, moved, err = recovered.Move(direction)
	return moveResult{Result: Result{Direction: direction, Position: position, Moved: moved, Err: err}, cursor: recovered}
}

func (worker *Worker) syncLatestFocus(ctx context.Context, cursor *Cursor, captureIfMissing bool) (*Cursor, error) {
	focus := worker.focus()
	if !focus.Valid() {
		return cursor, nil
	}
	if cursor != nil {
		_, currentErr := cursor.Current()
		_, syncErr := cursor.SyncFocus(focus)
		if syncErr == nil && !errors.Is(currentErr, atspi.ErrStaleObject) {
			return cursor, nil
		}
		if syncErr != nil && !errors.Is(syncErr, atspi.ErrObjectNotFound) && !errors.Is(syncErr, atspi.ErrStaleObject) {
			return cursor, syncErr
		}
	}
	if !captureIfMissing && cursor == nil {
		return nil, nil
	}

	return worker.captureCursor(ctx, nil)
}

func (worker *Worker) captureCursor(ctx context.Context, cursor *Cursor) (*Cursor, error) {
	captureContext, cancelCapture := context.WithTimeout(ctx, worker.captureTimeout)
	tree, err := worker.capturer.CaptureDesktop(captureContext)
	cancelCapture()
	if err != nil {
		return nil, fmt.Errorf("capture object review tree: %w", err)
	}
	if tree == nil {
		return nil, errors.New("capture object review tree: nil tree")
	}
	if cursor == nil || cursor.tree != tree {
		cursor, err = NewCursor(tree)
		if err != nil {
			return nil, err
		}
	}
	// Focus can change while capture is underway. Always synchronize to the
	// newest identity after the capture returns.
	focus := worker.focus()
	if _, err := cursor.SyncFocus(focus); err != nil {
		return nil, err
	}
	return cursor, nil
}