import Foundation
import Saga

extension Date {
  func formatted(_ format: String) -> String {
    let formatter = DateFormatter()
    formatter.dateFormat = format
    return formatter.string(from: self)
  }
}

extension Item where M == ArticleMetadata {

  /// The article summary, which is used when displaying a list of articles.
  var summary: String {
    // Use the summary if supplied in the articles front-matter.
    if let summary = metadata.summary {
      return summary
    }
    // Generate the summary from the first 255 words of the article.
    return String(body.withoutHtmlTags.truncate())
  }

  /// The articles banner image path.
  var imagePath: String {
    let image = metadata.image ?? "\(filenameWithoutExtension).png"
    return "/articles/images/\(image)"
  }

  /// An easy way to only get public articles, since ArticleMetadata.public is optional
  var `public`: Bool {
    #if DEBUG
      return true
    #else
      return metadata.public ?? true
    #endif
  }

  func getPrimaryTag() -> String? {
    guard let primaryTag = metadata.primaryTag else {
      guard metadata.tags.count == 1 else { return nil }
      return metadata.tags[0]
    }
    return primaryTag
  }

  func getDate() -> Date {
    guard let date = metadata.date else { return date }
    return date
  }

  func getUpdatedDate() -> Date? {
    return metadata.updated
  }
}

// NOTE: Most of these are taken from https://github.com/loopwerk/loopwerk.io

extension String {

  /// Used to generate the word count of an article, to be displayed as metadata about
  /// the article.
  var numberOfWords: Int {
    let characterSet = CharacterSet.whitespacesAndNewlines.union(.punctuationCharacters)
    let components = self.components(separatedBy: characterSet)
    return components.filter { !$0.isEmpty }.count
  }

  // This is a sloppy implementation but sadly `NSAttributedString(data:options:documentAttributes:)`
  // is not available in CoreFoundation, and as such can't run on Linux (blocking CI builds).
  var withoutHtmlTags: String {
    return replacingOccurrences(of: "(?m)<pre><span></span><code>[\\s\\S]+?</code></pre>", with: "", options: .regularExpression, range: nil)
      .replacingOccurrences(of: "<[^>]+>", with: "", options: .regularExpression, range: nil)
      .trimmingCharacters(in: .whitespacesAndNewlines)
  }

  /// See https://jinja2docs.readthedocs.io/en/stable/templates.html#truncate
  func truncate(length: Int = 255, killWords: Bool = false, end: String = "...", leeway: Int = 5) -> String {
    if count <= length + leeway {
      return self
    }

    if killWords {
      return prefix(length - end.count) + end
    }

    return prefix(length - end.count).split(separator: " ").dropLast().joined(separator: " ") + end
  }

  /// Removes unwanted breaks that are caused by the way markdown files are formatted by
  /// prettier in my neovim setup.  When not applied then paragraphs get split up improperly
  /// causing them to display funny on the site.
  var removeBreaks: String {
    replacingOccurrences(of: "<br>", with: "")
      .replacingOccurrences(of: "<br />", with: "")
      .trimmingCharacters(in: .whitespacesAndNewlines)
  }

}