import Foundation

public struct Charset {
  private static let specialChars: [Character: [UInt8]] = [
    "Ã": [65, 222],
    "ã": [97, 222],
    "Õ": [79, 222],
    "õ": [111, 222],
    "Ẫ": [194, 222],
    "ẫ": [226, 222],
    "Ẽ": [69, 222],
    "ẽ": [101, 222],
    "Ĩ": [73, 222],
    "ĩ": [105, 222],
    "Ũ": [85, 222],
    "ũ": [117, 222],
    "Ẵ": [195, 222],
    "ẵ": [227, 222],
    "Ễ": [202, 222],
    "ễ": [234, 222],
    "Ỗ": [212, 222],
    "ỗ": [244, 222],
    "Ỡ": [213, 222],
    "ỡ": [245, 222],
    "Ữ": [221, 222],
    "ữ": [253, 222],
    "Ỹ": [89, 222],
    "ỹ": [121, 222],
    "Ì": [73, 204],
    "ì": [105, 204],
    "Ò": [79, 204],
    "ò": [111, 204],
    "Ầ": [194, 204],
    "ầ": [226, 204],
    "Ằ": [195, 204],
    "ằ": [227, 204],
    "Ề": [202, 204],
    "ề": [234, 204],
    "Ồ": [212, 204],
    "ồ": [244, 204],
    "Ờ": [213, 204],
    "ờ": [245, 204],
    "Ừ": [221, 204],
    "ừ": [253, 204],
    "Ỳ": [89, 204],
    "ỳ": [121, 204],
    "Ị": [73, 242],
    "ị": [105, 242],
    "Ọ": [79, 242],
    "ọ": [111, 242],
    "Ạ": [65, 242],
    "ạ": [97, 242],
    "Ậ": [194, 242],
    "ậ": [226, 242],
    "Ặ": [195, 242],
    "ặ": [227, 242],
    "Ẹ": [69, 242],
    "ẹ": [101, 242],
    "Ệ": [202, 242],
    "ệ": [234, 242],
    "Ộ": [212, 242],
    "ộ": [244, 242],
    "Ợ": [213, 242],
    "ợ": [245, 242],
    "Ụ": [85, 242],
    "ụ": [117, 242],
    "Ự": [221, 242],
    "ự": [253, 242],
    "Ỵ": [89, 242],
    "ỵ": [121, 242],
    "Ỏ": [79, 210],
    "ỏ": [111, 210],
    "Ỉ": [73, 210],
    "ỉ": [105, 210],
    "Ả": [65, 210],
    "ả": [97, 210],
    "Ẩ": [194, 210],
    "ẩ": [226, 210],
    "Ẳ": [195, 210],
    "ẳ": [227, 210],
    "Ẻ": [69, 210],
    "ẻ": [101, 210],
    "Ể": [202, 210],
    "ể": [234, 210],
    "Ổ": [212, 210],
    "ổ": [244, 210],
    "Ở": [213, 210],
    "ở": [245, 210],
    "Ủ": [85, 210],
    "ủ": [117, 210],
    "Ử": [221, 210],
    "ử": [253, 210],
    "Ỷ": [89, 210],
    "ỷ": [121, 210],
    "Ý": [89, 236],
    "ý": [121, 236],
    "Ấ": [194, 236],
    "ấ": [226, 236],
    "Ắ": [195, 236],
    "ắ": [227, 236],
    "Ế": [202, 236],
    "ế": [234, 236],
    "Ố": [212, 236],
    "ố": [244, 236],
    "Ớ": [213, 236],
    "ớ": [245, 236],
    "Ứ": [221, 236],
    "ứ": [253, 236],
  ]

  public static func encode(_ input: String, hasQuote: Bool = false) -> [UInt8]
  {
    var output: [UInt8] = []
    let chars = CodePageDefinitions.definitions["windows1258"]?.chars ?? ""
    let offset = CodePageDefinitions.definitions["windows1258"]?.offset ?? 0

    for char in input {
      if let codepoint = char.unicodeScalars.first?.value {
        if codepoint < 128 {
          output.append(UInt8(codepoint))
        } else {
          if let position = chars.firstIndex(of: char) {
            let distance = chars.distance(from: chars.startIndex, to: position)
            output.append(UInt8(offset + distance))
          } else if codepoint < 256
            && (codepoint < offset || codepoint >= offset + chars.count)
          {
            output.append(UInt8(codepoint))
          } else if let specialChar = specialChars[char] {
            if hasQuote {
              output.append(contentsOf: specialChar)
            } else {
              output.append(specialChar[0])
            }
          } else {
            output.append(0x3f)  // Question mark
          }
        }
      }
    }

    return output
  }
}