import Foundation
import UIKit


// MARK: - CommentAttachmentRenderer: Renders HTML Comments!
//
final public class CommentAttachmentRenderer {

    /// Comment Attachment Text
    ///
    let defaultText = NSLocalizedString("[COMMENT]", comment: "Comment Attachment Label")

    /// Text Color
    ///
    var textColor = UIColor.gray

    /// Text Font
    ///
    var textFont: UIFont


    /// Default Initializer
    ///
    public init(font: UIFont) {
        self.textFont = font
    }
}


// MARK: - TextViewCommentsDelegate Methods
//
extension CommentAttachmentRenderer: TextViewAttachmentImageProvider {

    public func textView(_ textView: TextView, shouldRender attachment: NSTextAttachment) -> Bool {
        return attachment is CommentAttachment
    }

    public func textView(_ textView: TextView, imageFor attachment: NSTextAttachment, with size: CGSize) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(size, false, 0)

        // Either this is a comment attachment, or the logic is broken.
        let commentAttachment = attachment as! CommentAttachment

        guard !isGutenbergComment(commentAttachment) else {
            return nil
        }

        let message = messageAttributedString()
        let targetRect = boundingRect(for: message, size: size)

        message.draw(in: targetRect)

        let result = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return result
    }

    public func textView(_ textView: TextView, boundsFor attachment: NSTextAttachment, with lineFragment: CGRect) -> CGRect {
        let message = messageAttributedString()

        // Either this is a comment attachment, or the logic is broken.
        let commentAttachment = attachment as! CommentAttachment

        guard !isGutenbergComment(commentAttachment) else {
            return .zero
        }

        let size = CGSize(width: lineFragment.size.width, height: lineFragment.size.height)
        var rect = boundingRect(for: message, size: size)
        rect.origin.y = textFont.descender

        return rect.integral
    }
}


// MARK: - Private Methods
//
private extension CommentAttachmentRenderer {

    func boundingRect(for message: NSAttributedString, size: CGSize) -> CGRect {
        let targetBounds = message.boundingRect(with: size, options: [.usesLineFragmentOrigin, .usesFontLeading], context: nil)
        let targetPosition = CGPoint(x: ((size.width - targetBounds.width) * 0.5), y: ((size.height - targetBounds.height) * 0.5))

        return CGRect(origin: targetPosition, size: targetBounds.size)
    }

    func messageAttributedString() -> NSAttributedString {
        let attributes: [NSAttributedString.Key: Any] = [
            .foregroundColor: textColor,
            .font: textFont
        ]

        return NSAttributedString(string: defaultText, attributes: attributes)
    }

    func isGutenbergComment(_ comment: CommentAttachment) -> Bool {

        let openingGutenbergTag = "wp:"
        let closingGutenbergTag = "/wp:"

        let text = comment.text.trimmingCharacters(in: .whitespacesAndNewlines)

        return verify(text, startsWith: openingGutenbergTag) || verify(text, startsWith: closingGutenbergTag)
    }

    func verify(_ text: String, startsWith string: String) -> Bool {

        guard let endIndex = text.index(text.startIndex, offsetBy: string.count, limitedBy: text.endIndex) else {
            return false
        }

        let testRange = text.startIndex ..< endIndex
        let testString = String(text[testRange])

        return testString == string
    }
}