import SwiftUI

struct SearchSuggestionsView: View {
  var items: [Either<BooruTag, BooruSearchQuery>]
  @Binding var searchText: String

  private var lastSearchTag: String {
    String(searchText.split(separator: " ").last ?? "").lowercased()
  }

  private var filteredItems: [Either<BooruTag, BooruSearchQuery>] {
    let matchCanidateTag = lastSearchTag
    let matchingTagsLimit = 50

    guard !matchCanidateTag.isEmpty else { return [] }

    var seenTags = Set<String>()
    var matchingTags: [Either<BooruTag, BooruSearchQuery>] = []

    matchingTags.reserveCapacity(matchingTagsLimit)

    for item in items {
      if matchingTags.count >= matchingTagsLimit { break }

      switch item {
      case .left(let tag):
        let lowercasedName = tag.name.lowercased()

        if lowercasedName.contains(matchCanidateTag),
          seenTags.insert(lowercasedName).inserted
        {
          matchingTags.append(item)
        }

      case .right(let query):
        for tagName in query.tags {
          let lowercasedTagName = tagName.lowercased()

          if lowercasedTagName.contains(matchCanidateTag),
            seenTags.insert(lowercasedTagName).inserted
          {
            matchingTags.append(item)

            break
          }
        }
      }
    }

    return matchingTags
  }

  var body: some View {
    ForEach(filteredItems, id: \.self) { item in
      switch item {
      case .left(let tag):
        Button {
          if let range = searchText.range(of: lastSearchTag, options: .backwards) {
            searchText.replaceSubrange(range, with: tag.name)
          }
        } label: {
          Text(tag.name)
        }

      case .right(let query):
        Button {
          if let range = searchText.range(of: lastSearchTag, options: .backwards),
            let matchingTag = query.tags.first(where: { $0.lowercased().contains(lastSearchTag) })
          {
            searchText.replaceSubrange(range, with: matchingTag)
          }
        } label: {
          if let matchingTag = query.tags.first(where: { $0.lowercased().contains(lastSearchTag) })
          {
            Text(matchingTag)
          } else {
            Text(query.tags.first ?? "")
          }
        }
      }
    }
  }
}