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

package app

import (
	"fmt"
	"strings"
)

// Selection is owned by the session's anchor and cursor. Compare ranges in the
// current document without retaining text or inventing a native object identity.
func (session *ocrSession) selection_change_locked(oldStart, oldEnd int) string {
	start, end := session.selection_locked()
	var changes []string
	fragment := func(from, to int, selected bool) {
		if from < 0 || to <= from {
			return
		}
		message := "unselected"
		if selected {
			message = "selected"
		}
		if to-from <= lineSelectionFragmentLimit {
			value, _ := session.cursor.Slice(from, to)
			value = strings.Join(strings.Fields(value), " ")
			if value != "" {
				if selected {
					message = fmt.Sprintf("%s selected", value)
				} else {
					message = fmt.Sprintf("%s unselected", value)
				}
			}
		}
		changes = append(changes, message)
	}
	if oldEnd > oldStart {
		if end <= start {
			fragment(oldStart, oldEnd, false)
		} else {
			fragment(oldStart, min(oldEnd, start), false)
			fragment(max(oldStart, end), oldEnd, false)
		}
	}
	if end > start {
		if oldEnd <= oldStart {
			fragment(start, end, true)
		} else {
			fragment(start, min(end, oldStart), true)
			fragment(max(start, oldEnd), end, true)
		}
	}
	return strings.Join(changes, ", ")
}