import Foundation

class BooruPostXMLParser: NSObject, XMLParserDelegate {
  private var posts: [BooruPost] = []
  private var currentPost: BooruPost?
  private var parser: XMLParser
  private let provider: BooruProvider
  private var currentPostData: [String: String] = [:]
  private var currentElementName: String?
  private var currentText: String = ""

  init(data: Data, provider: BooruProvider) {
    parser = XMLParser(data: data)
    self.provider = provider

    super.init()

    parser.delegate = self
  }

  func parse() -> [BooruPost] {
    parser.parse()

    return posts
  }

  func parser(
    _ parser: XMLParser,  // swiftlint:disable:this unused_parameter
    didStartElement elementName: String,
    namespaceURI: String?,  // swiftlint:disable:this unused_parameter
    qualifiedName qName: String?,  // swiftlint:disable:this unused_parameter
    attributes attributeDict: [String: String] = [:]
  ) {
    if provider == .gelbooru {
      if elementName == "post" {
        currentPostData = [:]
      } else {
        currentElementName = elementName
        currentText = ""
      }
    } else {
      if elementName == "post" {
        guard let id = attributeDict["id"],
          let heightStr = attributeDict["height"],
          let height = Int(heightStr),
          let score = attributeDict["score"],
          let fileUrl = attributeDict["file_url"],
          let parentId = attributeDict["parent_id"],
          let sampleUrl = attributeDict["sample_url"],
          let sampleWidthStr = attributeDict["sample_width"],
          let sampleWidth = Int(sampleWidthStr),
          let sampleHeightStr = attributeDict["sample_height"],
          let sampleHeight = Int(sampleHeightStr),
          let previewUrl = attributeDict["preview_url"],
          let rating = attributeDict["rating"],
          let tags = attributeDict["tags"],
          let widthStr = attributeDict["width"],
          let width = Int(widthStr),
          let change = attributeDict["change"],
          let md5 = attributeDict["md5"],
          let creatorId = attributeDict["creator_id"],
          let hasChildrenStr = attributeDict["has_children"],
          let createdAt = attributeDict["created_at"],
          let status = attributeDict["status"],
          let source = attributeDict["source"],
          let previewWidthStr = attributeDict["preview_width"],
          let previewWidth = Int(previewWidthStr),
          let previewHeightStr = attributeDict["preview_height"],
          let previewHeight = Int(previewHeightStr)
        else {
          return
        }

        currentPost = BooruPost(
          id: id,
          height: height,
          score: score,
          fileURL: URL(string: fileUrl)!,
          parentID: parentId,
          sampleURL: URL(string: sampleUrl)!,
          sampleWidth: sampleWidth,
          sampleHeight: sampleHeight,
          previewURL: URL(string: previewUrl)!,
          rating: BooruRating(rating),
          tags: tags.components(separatedBy: " ").filter { !$0.isEmpty },
          width: width,
          change: change,
          md5: md5,
          creatorID: creatorId,
          hasChildren: hasChildrenStr == "true",
          createdAt: parseCreatedAt(createdAt)!,
          status: status,
          source: source,
          hasNotes: (attributeDict["has_notes"] ?? "false") == "true",
          hasComments: (attributeDict["has_comments"] ?? "false") == "true",
          previewWidth: previewWidth,
          previewHeight: previewHeight
        )
      }
    }
  }

  func parser(
    _ parser: XMLParser,  // swiftlint:disable:this unused_parameter
    foundCharacters string: String
  ) {
    if provider == .gelbooru, currentElementName != nil {
      currentText += string
    }
  }

  func parser(
    _ parser: XMLParser,  // swiftlint:disable:this unused_parameter
    didEndElement elementName: String,
    namespaceURI: String?,  // swiftlint:disable:this unused_parameter
    qualifiedName qName: String?  // swiftlint:disable:this unused_parameter
  ) {
    if provider == .gelbooru {
      if elementName == "post" {
        guard let id = currentPostData["id"],
          let heightStr = currentPostData["height"],
          let height = Int(heightStr),
          let score = currentPostData["score"],
          let fileUrlStr = currentPostData["file_url"],
          let fileUrl = URL(string: fileUrlStr),
          let parentId = currentPostData["parent_id"],
          let sampleUrlStr = currentPostData["sample_url"],
          let sampleUrl = URL(string: sampleUrlStr),
          let sampleWidthStr = currentPostData["sample_width"],
          let sampleWidth = Int(sampleWidthStr),
          let sampleHeightStr = currentPostData["sample_height"],
          let sampleHeight = Int(sampleHeightStr),
          let previewUrlStr = currentPostData["preview_url"],
          let previewUrl = URL(string: previewUrlStr),
          let rating = currentPostData["rating"],
          let tagsString = currentPostData["tags"],
          let widthStr = currentPostData["width"],
          let width = Int(widthStr),
          let change = currentPostData["change"],
          let md5 = currentPostData["md5"],
          let creatorId = currentPostData["creator_id"],
          let hasChildrenStr = currentPostData["has_children"],
          let createdAtStr = currentPostData["created_at"],
          let createdAt = parseCreatedAt(createdAtStr),
          let status = currentPostData["status"],
          let source = currentPostData["source"],
          let previewWidthStr = currentPostData["preview_width"],
          let previewWidth = Int(previewWidthStr),
          let previewHeightStr = currentPostData["preview_height"],
          let previewHeight = Int(previewHeightStr)
        else {
          return
        }

        posts.append(
          BooruPost(
            id: id,
            height: height,
            score: score,
            fileURL: fileUrl,
            parentID: parentId,
            sampleURL: sampleUrl,
            sampleWidth: sampleWidth,
            sampleHeight: sampleHeight,
            previewURL: previewUrl,
            rating: BooruRating(rating),
            tags: tagsString.components(separatedBy: CharacterSet.whitespacesAndNewlines)
              .filter { !$0.isEmpty },
            width: width,
            change: change,
            md5: md5,
            creatorID: creatorId,
            hasChildren: hasChildrenStr == "true",
            createdAt: createdAt,
            status: status,
            source: source,
            hasNotes: (currentPostData["has_notes"] ?? "false") == "true",
            hasComments: (currentPostData["has_comments"] ?? "false") == "true",
            previewWidth: previewWidth,
            previewHeight: previewHeight
          )
        )
      } else if let currentElement = currentElementName {
        currentPostData[currentElement] = currentText.trimmingCharacters(
          in: .whitespacesAndNewlines
        )
        currentElementName = nil
        currentText = ""
      }
    } else {
      if elementName == "post", let post = currentPost {
        posts.append(post)

        currentPost = nil
      }
    }
  }

  #if DEBUG
    func parser(_: XMLParser, parseErrorOccurred parseError: any Error) {
      print("parser: \(parseError)")
    }
  #endif

  func parseCreatedAt(_ input: String) -> Date? {
    let dateFormatter = DateFormatter()

    dateFormatter.dateFormat = "EEE MMM dd HH:mm:ss Z yyyy"
    dateFormatter.locale = Locale(identifier: "en_US_POSIX")

    if let date = dateFormatter.date(from: input) {
      return date
    }

    if let timestamp = Double(input) {
      return Date(timeIntervalSince1970: timestamp)
    }

    return nil
  }
}