RichTextViewContext.swift

//
//  RichTextViewContext.swift
//  Proton
//
//  Created by Rajdeep Kwatra on 14/1/20.
//  Copyright © 2020 Rajdeep Kwatra. All rights reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

import Foundation
import UIKit

class RichTextViewContext: NSObject, UITextViewDelegate {
    weak var activeTextView: RichTextView?

    weak var selectedTextView: RichTextView?

    func textView(_ textView: UITextView, shouldInteractWith textAttachment: NSTextAttachment, in characterRange: NSRange, interaction: UITextItemInteraction) -> Bool {
        return interaction != .presentActions
    }

    func textViewDidChangeSelection(_ textView: UITextView) {
        guard textView.delegate === self else { return }
        if textView.selectedTextRange != nil {
            selectedTextView = textView.asRichTextView
        } else {
            selectedTextView = nil
        }

        guard let richTextView = textView as? RichTextView else { return }
        let range = textView.selectedRange

        resetAttachmentSelection(textView)
        guard range.length > 0 else {
            if textView.attributedText.length == 0 {
                richTextView.resetTypingAttributes()
            }
            var attributes = richTextView.typingAttributes
            let contentType = attributes[.blockContentType] as? EditorContent.Name ?? .unknown
            attributes[.blockContentType] = nil
            richTextView.richTextViewDelegate?.richTextView(richTextView, didChangeSelection: range, attributes: attributes, contentType: contentType)
            return
        }

        let substring = textView.attributedText.attributedSubstring(from: range)

        // Mark attachments as selected if there are any in the selected range
        substring.enumerateAttribute(.attachment, in: substring.fullRange, options: .longestEffectiveRangeNotRequired) { attachment, range, _ in
            if let attachment = attachment as? Attachment {
                attachment.isSelected = true
            }
        }

        var attributes = substring.attributes(at: 0, effectiveRange: nil)
        let contentType = attributes[.blockContentType] as? EditorContent.Name ?? .unknown
        attributes[.blockContentType] = nil
        richTextView.richTextViewDelegate?.richTextView(richTextView, didChangeSelection: range, attributes: attributes, contentType: contentType)
    }

    func resetAttachmentSelection(_ textView: UITextView) {
        guard textView.delegate === self else { return }

        guard let attributedText = textView.attributedText else { return }
        attributedText.enumerateAttribute(.attachment, in: attributedText.fullRange, options: .longestEffectiveRangeNotRequired) { attachment, _, _ in
            if let attachment = attachment as? Attachment {
                attachment.isSelected = false
            }
        }
    }
}

extension UITextView {
    var asRichTextView: RichTextView? {
        self as? RichTextView
    }
}